Merge pull request #628 from angelo-v/patch-1

Update README.md
2024-04-12 16:00:14 +02:00 · 2024-04-12 15:34:32 +02:00 · 2023-11-14 13:43:42 +01:00 · 2023-10-06 09:44:30 +02:00 · 2023-01-24 12:42:57 +01:00 · 2023-01-23 16:14:30 -05:00
84 changed files with 14169 additions and 5564 deletions
--- a/.bowerrc
+++ b/.bowerrc
@@ -1,3 +0,0 @@
-{
- "directory": "../"
-}
--- a/.github/workflows/nodejs.yml
+++ b/.github/workflows/nodejs.yml
@@ -0,0 +1,31 @@
+# This workflow will do a clean install of node dependencies, build the source code and run tests across different versions of node
+# For more information see: https://help.github.com/actions/language-and-framework-guides/using-nodejs-with-github-actions
+
+name: Node.js CI
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        node-version: [10.x, 12.x, 13.x]
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Use Node.js ${{ matrix.node-version }}
+      uses: actions/setup-node@v1
+      with:
+        node-version: ${{ matrix.node-version }}
+    - run: npm ci
+    - run: npm run lint
+    - run: npm run test-extensive
+      env:
+        CI: true
--- a/.gitignore
+++ b/.gitignore
@@ -1,12 +1,4 @@
 node_modules
-bower_components
-build
-build_test
-.directory
-.codio
-.settings
-.jshintignore
-.jshintrc
-.validate.json
-/y.js
-/y.js.map
+dist
+.vscode
+docs
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,4 +0,0 @@
-[submodule "dist"]
-	path = dist
-	url = https://github.com/y-js/yjs.git
-	branch = dist
--- a/.jsdoc.json
+++ b/.jsdoc.json
@@ -0,0 +1,50 @@
+{
+  "sourceType": "module",
+  "tags": {
+    "allowUnknownTags": true,
+    "dictionaries": ["jsdoc"]
+  },
+  "source": {
+    "include": ["./src"],
+    "includePattern": ".js$"
+  },
+  "plugins": [
+    "plugins/markdown"
+  ],
+  "templates": {
+    "referenceTitle": "Yjs",
+    "disableSort": false,
+    "useCollapsibles": true,
+    "collapse": true,
+    "resources": {
+      "yjs.dev": "Yjs website"
+    },
+    "logo": {
+      "url": "https://user-images.githubusercontent.com/5553757/48975307-61efb100-f06d-11e8-9177-ee895e5916e5.png",
+      "width": "162px",
+      "height": "162px",
+      "link": "/"
+    },
+    "tabNames": {
+      "api": "API",
+      "tutorials": "Examples"
+    },
+    "footerText": "Shared Editing",
+    "css": [
+      "./style.css"
+    ],
+    "default": {
+      "staticFiles": {
+          "include": ["examples/"]
+      }
+    }
+  },
+  "opts": {
+    "destination": "./docs/",
+    "encoding": "utf8",
+    "private": false,
+    "recurse": true,
+    "template": "./node_modules/tui-jsdoc-template",
+    "tutorials": "./examples"
+  }
+}
--- a/.markdownlint.json
+++ b/.markdownlint.json
@@ -0,0 +1,4 @@
+{
+  "default": true,
+  "no-inline-html": false
+}
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,8 +0,0 @@
-language: node_js
-before_install:
-  - "npm install -g bower"
-node_js:
-  - "0.12"
-branches:
-  only:
-    - master
--- a/Examples/OfflineEditing/index.html
+++ b/Examples/OfflineEditing/index.html
@@ -1,12 +0,0 @@
-<!DOCTYPE html>
-<html>
-<body>
-  <button id="button">Disconnect</button>
-  <h1 id="contenteditable" contentEditable></h1>
-  <textarea style="width:80%;" rows=40 id="textfield"></textarea>
-
-  <script src="../../node_modules/simplewebrtc/simplewebrtc.bundle.js"></script>
-  <script src="../../y.js"></script>
-  <script src="./index.js"></script>
-</body>
-</html>
--- a/Examples/OfflineEditing/index.js
+++ b/Examples/OfflineEditing/index.js
@@ -1,50 +0,0 @@
-/* global Y */
-
-// create a shared object. This function call will return a promise!
-Y({
-  db: {
-    name: 'IndexedDB',
-    namespace: 'offlineEditingDemo'
-  },
-  connector: {
-    name: 'WebRTC',
-    room: 'offlineEditingDemo',
-    debug: true
-  }
-}).then(function (yconfig) {
-  // yconfig holds all the information about the shared object
-  window.yconfig = yconfig
-  // yconfig.root holds the shared element
-  window.y = yconfig.root
-
-  // now we bind the textarea and the contenteditable h1 element
-  // to a shared element
-  var textarea = document.getElementById('textfield')
-  var contenteditable = document.getElementById('contenteditable')
-  yconfig.root.observePath(['text'], function (text) {
-    // every time the 'text' property of the yconfig.root changes,
-    // this function is called. Then we bind it to the html elements
-    if (text != null) {
-      // when the text property is deleted, text may be undefined!
-      // This is why we have to check if text exists..
-      text.bind(textarea)
-      text.bind(contenteditable)
-    }
-  })
-  // create a shared TextBind
-  var textpromise = yconfig.root.get('text')
-  if (textpromise == null) {
-    yconfig.root.set('text', Y.TextBind)
-  }
-  // We also provide a button for disconnecting/reconnecting the shared element
-  var button = document.querySelector('#button')
-  button.onclick = function () {
-    if (button.innerText === 'Disconnect') {
-      yconfig.disconnect()
-      button.innerText = 'Reconnect'
-    } else {
-      yconfig.reconnect()
-      button.innerText = 'Disconnect'
-    }
-  }
-})
--- a/Examples/TextBind/index.html
+++ b/Examples/TextBind/index.html
@@ -1,12 +0,0 @@
-<!DOCTYPE html>
-<html>
-<body>
-  <button id="button">Disconnect</button>
-  <h1 id="contenteditable" contentEditable></h1>
-  <textarea style="width:80%;" rows=40 id="textfield"></textarea>
-
-  <script src="../../node_modules/simplewebrtc/simplewebrtc.bundle.js"></script>
-  <script src="../../y.js"></script>
-  <script src="./index.js"></script>
-</body>
-</html>
--- a/Examples/TextBind/index.js
+++ b/Examples/TextBind/index.js
@@ -1,47 +0,0 @@
-/* global Y */
-
-// create a shared object. This function call will return a promise!
-Y({
-  db: {
-    name: 'Memory'
-  },
-  connector: {
-    name: 'WebRTC',
-    room: 'TextBindDemo',
-    debug: true
-  }
-}).then(function (yconfig) {
-  // yconfig holds all the information about the shared object
-  window.yconfig = yconfig
-  // yconfig.root holds the shared element
-  window.y = yconfig.root
-
-  // now we bind the textarea and the contenteditable h1 element
-  // to a shared element
-  var textarea = document.getElementById('textfield')
-  var contenteditable = document.getElementById('contenteditable')
-  yconfig.root.observePath(['text'], function (text) {
-    // every time the 'text' property of the yconfig.root changes,
-    // this function is called. Then we bind it to the html elements
-    if (text != null) {
-      // when the text property is deleted, text may be undefined!
-      // This is why we have to check if text exists..
-      text.bind(textarea)
-      text.bind(contenteditable)
-    }
-  })
-  // create a shared TextBind
-  yconfig.root.set('text', Y.TextBind)
-
-  // We also provide a button for disconnecting/reconnecting the shared element
-  var button = document.querySelector('#button')
-  button.onclick = function () {
-    if (button.innerText === 'Disconnect') {
-      yconfig.disconnect()
-      button.innerText = 'Reconnect'
-    } else {
-      yconfig.reconnect()
-      button.innerText = 'Disconnect'
-    }
-  }
-})
--- a/README.md
+++ b/README.md
--- a/1
+++ b/1
--- a/gulpfile.js
+++ b/gulpfile.js
@@ -1,207 +0,0 @@
-/* eslint-env node */
-
-/** Gulp Commands
-
-  gulp command*
-    [--export ModuleType]
-    [--name ModuleName]
-    [--testport TestPort]
-    [--testfiles TestFiles]
-
-  Module name (ModuleName):
-    Compile this to "y.js" (default)
-
-  Supported module types (ModuleType):
-    - amd
-    - amdStrict
-    - common
-    - commonStrict
-    - ignore (default)
-    - system
-    - umd
-    - umdStrict
-
-  Test port (TestPort):
-    Serve the specs on port 8888 (default)
-
-  Test files (TestFiles):
-    Specify which specs to use!
-
-  Commands:
-    - build:deploy
-        Build this library for deployment (es6->es5, minified)
-    - dev:browser
-        Watch the ./src directory.
-        Builds the library on changes.
-        Starts an http-server and serves the test suite on http://127.0.0.1:8888.
-    - dev:node
-        Watch the ./src directory.
-        Builds and specs the library on changes.
-        Usefull to run with node-inspector.
-        `node-debug $(which gulp) dev:node
-    - test:
-        Test this library
-*/
-
-var gulp = require('gulp')
-var sourcemaps = require('gulp-sourcemaps')
-var babel = require('gulp-babel')
-var uglify = require('gulp-uglify')
-var minimist = require('minimist')
-var jasmine = require('gulp-jasmine')
-var jasmineBrowser = require('gulp-jasmine-browser')
-var concat = require('gulp-concat')
-var watch = require('gulp-watch')
-var shell = require('gulp-shell')
-var $ = require('gulp-load-plugins')()
-
-var options = minimist(process.argv.slice(2), {
-  string: ['export', 'name', 'testport', 'testfiles', 'regenerator'],
-  default: {
-    export: 'ignore',
-    name: 'y.js',
-    testport: '8888',
-    testfiles: 'src/**/*.js',
-    regenerator: process.version < 'v0.12'
-  }
-})
-
-var polyfills = [
-  './node_modules/gulp-babel/node_modules/babel-core/node_modules/regenerator/runtime.js'
-]
-
-var concatOrder = [
-  'y.js',
-  'Connector.js',
-  'Database.js',
-  'Transaction.js',
-  'Struct.js',
-  'Utils.js',
-  'Databases/RedBlackTree.js',
-  'Databases/Memory.js',
-  'Databases/IndexedDB.js',
-  'Connectors/Test.js',
-  'Connectors/WebRTC.js',
-  'Types/Array.js',
-  'Types/Map.js',
-  'Types/TextBind.js'
-]
-
-var files = {
-  src: polyfills.concat(concatOrder.map(function (f) {
-    return 'src/' + f
-  })),
-  test: ['build/Helper.spec.js'].concat(concatOrder.map(function (f) {
-    return 'build/' + f
-  }).concat(['build/**/*.spec.js']))
-}
-
-if (options.regenerator) {
-  files.test = polyfills.concat(files.test)
-}
-
-gulp.task('deploy:build', function () {
-  return gulp.src(files.src)
-    .pipe(sourcemaps.init())
-    .pipe(concat('y.js'))
-    .pipe(babel({
-      loose: 'all',
-      modules: 'ignore',
-      experimental: true
-    }))
-    .pipe(uglify())
-    .pipe(sourcemaps.write('.'))
-    .pipe(gulp.dest('.'))
-})
-
-gulp.task('deploy:updateSubmodule', function () {
-  return $.git.updateSubmodule({ args: '--init' })
-})
-
-gulp.task('deploy:copy', function () {
-  return gulp.src(['./y.js', './y.js.map', './README.md', 'package.json', 'LICENSE'])
-    .pipe(gulp.dest('./dist/'))
-})
-
-gulp.task('deploy:bump', function () {
-  return gulp.src('./package.json')
-    .pipe($.bump({type: 'patch'}))
-    .pipe(gulp.dest('./'))
-})
-
-gulp.task('deploy', ['deploy:updateSubmodule', 'deploy:bump', 'deploy:build', 'deploy:copy'], function () {
-  return gulp.src('./package.json', {read: false})
-    .pipe(shell([
-      'echo "Deploying version <%= getVersion(file.path) %>"',
-      'cd ./dist/',
-      'git add -A',
-      'git commit -am "Deploy <%= getVersion(file.path) %>" -n',
-      'git tag -a v<%= getVersion(file.path) %> -m "Release <%= getVersion(file.path) %>"',
-      'git push',
-      'git push origin --tags',
-      'cd ..',
-      'git commit -am "Release <%= getVersion(file.path) %>" -n',
-      'git push'
-    ], {
-      templateData: {
-        getVersion: function (s) {
-          return require(s).version
-        }
-      }
-    }))
-})
-
-gulp.task('build:test', function () {
-  var babelOptions = {
-    loose: 'all',
-    modules: 'ignore',
-    experimental: true
-  }
-  if (!options.regenerator) {
-    babelOptions.blacklist = 'regenerator'
-  }
-  gulp.src(files.src)
-    .pipe(sourcemaps.init())
-    .pipe(concat('y.js'))
-    .pipe(babel(babelOptions))
-    .pipe(sourcemaps.write())
-    .pipe(gulp.dest('.'))
-
-  return gulp.src('src/**/*.js')
-    .pipe(sourcemaps.init())
-    .pipe(babel(babelOptions))
-    .pipe(sourcemaps.write())
-    .pipe(gulp.dest('build'))
-})
-
-gulp.task('dev:node', ['test'], function () {
-  gulp.watch('src/**/*.js', ['test'])
-})
-
-gulp.task('dev:browser', ['build:test'], function () {
-  gulp.watch('src/**/*.js', ['build:test'])
-
-  gulp.src(files.test)
-    .pipe(watch(['build/**/*.js']))
-    .pipe(jasmineBrowser.specRunner())
-    .pipe(jasmineBrowser.server({port: options.testport}))
-})
-
-gulp.task('dev', ['build:test'], function () {
-  gulp.start('dev:browser')
-  gulp.start('dev:node')
-})
-
-gulp.task('test', ['build:test'], function () {
-  var testfiles = files.test
-  if (typeof Promise === 'undefined') {
-    testfiles.concat(['src/polyfills.js'])
-  }
-  return gulp.src(testfiles)
-    .pipe(jasmine({
-      verbose: true,
-      includeStuckTrace: true
-    }))
-})
-
-gulp.task('default', ['test'])
--- a/package-lock.json
+++ b/package-lock.json
--- a/package.json
+++ b/package.json
@@ -1,65 +1,79 @@
 {
  "name": "yjs",
-  "version": "0.6.18",
-  "description": "A framework for real-time p2p shared editing on arbitrary complex data types",
-  "main": "y.js",
-  "scripts": {
-    "test": "node --harmony ./node_modules/.bin/gulp test",
-    "lint": "./node_modules/.bin/standard",
-    "build": "./node_modules/.bin/standard build"
+  "version": "13.2.0",
+  "description": "Shared Editing Library",
+  "main": "./dist/yjs.cjs",
+  "module": "./dist/yjs.mjs",
+  "types": "./dist/src/index.d.ts",
+  "sideEffects": false,
+  "funding": {
+    "type": "GitHub Sponsors ❤",
+    "url": "https://github.com/sponsors/dmonad"
  },
-  "pre-commit": [
-    "lint",
-    "test"
+  "scripts": {
+    "test": "npm run dist && node ./dist/tests.cjs --repitition-time 50",
+    "test-extensive": "npm run lint && npm run dist && node ./dist/tests.cjs --production --repitition-time 10000",
+    "dist": "rm -rf dist && rollup -c && tsc",
+    "watch": "rollup -wc",
+    "lint": "markdownlint README.md && standard && tsc",
+    "docs": "rm -rf docs; jsdoc --configure ./.jsdoc.json --verbose --readme ./README.md --package ./package.json || true",
+    "serve-docs": "npm run docs && http-server ./docs/",
+    "preversion": "npm run lint && PRODUCTION=1 npm run dist && npm run docs && node ./dist/tests.cjs --repitition-time 1000",
+    "debug": "concurrently 'http-server -o test.html' 'npm run watch'",
+    "trace-deopt": "clear && rollup -c  && node --trace-deopt dist/test.cjs",
+    "trace-opt": "clear && rollup -c  && node --trace-opt dist/test.cjs"
+  },
+  "files": [
+    "dist/*",
+    "src/*",
+    "tests/*",
+    "docs/*"
  ],
+  "dictionaries": {
+    "doc": "docs",
+    "test": "tests"
+  },
  "standard": {
-    "parser": "babel-eslint",
    "ignore": [
-      "build/**",
-      "./y.js",
-      "./y.js.map"
+      "/dist",
+      "/node_modules",
+      "/docs"
    ]
  },
  "repository": {
    "type": "git",
-    "url": "https://github.com/y-js/yjs.git"
+    "url": "https://github.com/yjs/yjs.git"
  },
  "keywords": [
-    "OT",
-    "Operational Transformation",
-    "collaboration",
-    "synchronization",
-    "ShareJs",
-    "OpenCoweb",
-    "concurrency"
+    "Yjs",
+    "CRDT",
+    "offline",
+    "shared editing",
+    "concurrency",
+    "collaboration"
  ],
  "author": "Kevin Jahns",
-  "email": "kevin.jahns@rwth-aachen.de",
+  "email": "kevin.jahns@protonmail.com",
  "license": "MIT",
  "bugs": {
-    "url": "https://github.com/y-js/yjs/issues"
+    "url": "https://github.com/yjs/yjs/issues"
+  },
+  "homepage": "https://yjs.dev",
+  "dependencies": {
+    "lib0": "^0.2.27"
  },
-  "homepage": "http://y-js.org",
  "devDependencies": {
-    "babel-eslint": "^4.1.2",
-    "gulp": "^3.9.0",
-    "gulp-babel": "^5.2.1",
-    "gulp-bump": "^1.0.0",
-    "gulp-concat": "^2.6.0",
-    "gulp-filter": "^3.0.1",
-    "gulp-git": "^1.6.0",
-    "gulp-jasmine": "^2.0.1",
-    "gulp-jasmine-browser": "^0.2.3",
-    "gulp-load-plugins": "^1.0.0",
-    "gulp-shell": "^0.5.1",
-    "gulp-sourcemaps": "^1.5.2",
-    "gulp-tag-version": "^1.3.0",
-    "gulp-uglify": "^1.4.1",
-    "gulp-util": "^3.0.6",
-    "gulp-watch": "^4.3.5",
-    "minimist": "^1.2.0",
-    "pre-commit": "^1.1.1",
-    "promise-polyfill": "^2.1.0",
-    "standard": "^5.2.2"
+    "@rollup/plugin-commonjs": "^11.1.0",
+    "@rollup/plugin-node-resolve": "^7.1.3",
+    "concurrently": "^3.6.1",
+    "http-server": "^0.12.3",
+    "jsdoc": "^3.6.4",
+    "markdownlint-cli": "^0.23.1",
+    "rollup": "^1.32.1",
+    "rollup-cli": "^1.0.9",
+    "standard": "^14.3.4",
+    "tui-jsdoc-template": "^1.2.2",
+    "typescript": "^3.9.3",
+    "y-protocols": "^0.2.3"
  }
 }
--- a/rollup.config.js
+++ b/rollup.config.js
@@ -0,0 +1,94 @@
+import nodeResolve from '@rollup/plugin-node-resolve'
+import commonjs from '@rollup/plugin-commonjs'
+
+const localImports = process.env.LOCALIMPORTS
+
+const customModules = new Set([
+  'y-websocket',
+  'y-codemirror',
+  'y-ace',
+  'y-textarea',
+  'y-quill',
+  'y-dom',
+  'y-prosemirror'
+])
+/**
+ * @type {Set<any>}
+ */
+const customLibModules = new Set([
+  'lib0',
+  'y-protocols'
+])
+const debugResolve = {
+  resolveId (importee) {
+    if (importee === 'yjs') {
+      return `${process.cwd()}/src/index.js`
+    }
+    if (localImports) {
+      if (customModules.has(importee.split('/')[0])) {
+        return `${process.cwd()}/../${importee}/src/${importee}.js`
+      }
+      if (customLibModules.has(importee.split('/')[0])) {
+        return `${process.cwd()}/../${importee}`
+      }
+    }
+    return null
+  }
+}
+
+export default [{
+  input: './src/index.js',
+  output: {
+    name: 'Y',
+    file: 'dist/yjs.cjs',
+    format: 'cjs',
+    sourcemap: true,
+    paths: path => {
+      if (/^lib0\//.test(path)) {
+        return `lib0/dist/${path.slice(5, -3)}.cjs`
+      }
+      return path
+    }
+  },
+  external: id => /^lib0\//.test(id)
+}, {
+  input: './src/index.js',
+  output: {
+    name: 'Y',
+    file: 'dist/yjs.mjs',
+    format: 'esm',
+    sourcemap: true
+  },
+  external: id => /^lib0\//.test(id)
+}, {
+  input: './tests/index.js',
+  output: {
+    name: 'test',
+    file: 'dist/tests.js',
+    format: 'iife',
+    sourcemap: true
+  },
+  plugins: [
+    debugResolve,
+    nodeResolve({
+      mainFields: ['module', 'browser', 'main']
+    }),
+    commonjs()
+  ]
+}, {
+  input: './tests/index.js',
+  output: {
+    name: 'test',
+    file: 'dist/tests.cjs',
+    format: 'cjs',
+    sourcemap: true
+  },
+  plugins: [
+    debugResolve,
+    nodeResolve({
+      mainFields: ['module', 'main']
+    }),
+    commonjs()
+  ],
+  external: ['isomorphic.js']
+}]
--- a/src/Connector.js
+++ b/src/Connector.js
@@ -1,328 +0,0 @@
-/* globals Y */
-'use strict'
-
-class AbstractConnector {
-  /*
-    opts contains the following information:
-     role : String Role of this client ("master" or "slave")
-     userId : String Uniquely defines the user.
-     debug: Boolean Whether to print debug messages (optional)
-  */
-  constructor (y, opts) {
-    this.y = y
-    if (opts == null) {
-      opts = {}
-    }
-    if (opts.role == null || opts.role === 'master') {
-      this.role = 'master'
-    } else if (opts.role === 'slave') {
-      this.role = 'slave'
-    } else {
-      throw new Error("Role must be either 'master' or 'slave'!")
-    }
-    this.role = opts.role
-    this.connections = {}
-    this.isSynced = false
-    this.userEventListeners = []
-    this.whenSyncedListeners = []
-    this.currentSyncTarget = null
-    this.syncingClients = []
-    this.forwardToSyncingClients = opts.forwardToSyncingClients !== false
-    this.debug = opts.debug === true
-    this.broadcastedHB = false
-    this.syncStep2 = Promise.resolve()
-  }
-  reconnect () {
-  }
-  disconnect () {
-    this.connections = {}
-    this.isSynced = false
-    this.currentSyncTarget = null
-    this.broadcastedHB = false
-    this.syncingClients = []
-    this.whenSyncedListeners = []
-    return this.y.db.stopGarbageCollector()
-  }
-  setUserId (userId) {
-    this.userId = userId
-    return this.y.db.setUserId(userId)
-  }
-  onUserEvent (f) {
-    this.userEventListeners.push(f)
-  }
-  userLeft (user) {
-    delete this.connections[user]
-    if (user === this.currentSyncTarget) {
-      this.currentSyncTarget = null
-      this.findNextSyncTarget()
-    }
-    this.syncingClients = this.syncingClients.filter(function (cli) {
-      return cli !== user
-    })
-    for (var f of this.userEventListeners) {
-      f({
-        action: 'userLeft',
-        user: user
-      })
-    }
-  }
-  userJoined (user, role) {
-    if (role == null) {
-      throw new Error('You must specify the role of the joined user!')
-    }
-    if (this.connections[user] != null) {
-      throw new Error('This user already joined!')
-    }
-    this.connections[user] = {
-      isSynced: false,
-      role: role
-    }
-    for (var f of this.userEventListeners) {
-      f({
-        action: 'userJoined',
-        user: user,
-        role: role
-      })
-    }
-    if (this.currentSyncTarget == null) {
-      this.findNextSyncTarget()
-    }
-  }
-  // Execute a function _when_ we are connected.
-  // If not connected, wait until connected
-  whenSynced (f) {
-    if (this.isSynced) {
-      f()
-    } else {
-      this.whenSyncedListeners.push(f)
-    }
-  }
-  /*
-
-   returns false, if there is no sync target
-   true otherwise
-  */
-  findNextSyncTarget () {
-    if (this.currentSyncTarget != null || this.isSynced) {
-      return // "The current sync has not finished!"
-    }
-
-    var syncUser = null
-    for (var uid in this.connections) {
-      if (!this.connections[uid].isSynced) {
-        syncUser = uid
-        break
-      }
-    }
-    if (syncUser != null) {
-      var conn = this
-      this.currentSyncTarget = syncUser
-      this.y.db.requestTransaction(function *() {
-        conn.send(syncUser, {
-          type: 'sync step 1',
-          stateSet: yield* this.getStateSet(),
-          deleteSet: yield* this.getDeleteSet()
-        })
-      })
-    } else {
-      this.isSynced = true
-      // call when synced listeners
-      for (var f of this.whenSyncedListeners) {
-        f()
-      }
-      this.whenSyncedListeners = []
-      this.y.db.requestTransaction(function *() {
-        yield* this.garbageCollectAfterSync()
-      })
-    }
-  }
-  send (uid, message) {
-    if (this.debug) {
-      console.log(`send ${this.userId} -> ${uid}: ${message.type}`, m) // eslint-disable-line
-    }
-  }
-  /*
-    You received a raw message, and you know that it is intended for Yjs. Then call this function.
-  */
-  receiveMessage (sender, m) {
-    if (sender === this.userId) {
-      return
-    }
-    if (this.debug) {
-      console.log(`receive ${sender} -> ${this.userId}: ${m.type}`, JSON.parse(JSON.stringify(m))) // eslint-disable-line
-    }
-    if (m.type === 'sync step 1') {
-      // TODO: make transaction, stream the ops
-      let conn = this
-      this.y.db.requestTransaction(function *() {
-        var currentStateSet = yield* this.getStateSet()
-        yield* this.applyDeleteSet(m.deleteSet)
-
-        var ds = yield* this.getDeleteSet()
-        var ops = yield* this.getOperations(m.stateSet)
-        conn.send(sender, {
-          type: 'sync step 2',
-          os: ops,
-          stateSet: currentStateSet,
-          deleteSet: ds
-        })
-        if (this.forwardToSyncingClients) {
-          conn.syncingClients.push(sender)
-          setTimeout(function () {
-            conn.syncingClients = conn.syncingClients.filter(function (cli) {
-              return cli !== sender
-            })
-            conn.send(sender, {
-              type: 'sync done'
-            })
-          }, conn.syncingClientDuration)
-        } else {
-          conn.send(sender, {
-            type: 'sync done'
-          })
-        }
-        conn._setSyncedWith(sender)
-      })
-    } else if (m.type === 'sync step 2') {
-      let conn = this
-      var broadcastHB = !this.broadcastedHB
-      this.broadcastedHB = true
-      var db = this.y.db
-      this.syncStep2 = new Promise(function (resolve) {
-        db.requestTransaction(function * () {
-          yield* this.applyDeleteSet(m.deleteSet)
-          this.store.apply(m.os)
-          db.requestTransaction(function * () {
-            var ops = yield* this.getOperations(m.stateSet)
-            if (ops.length > 0) {
-              m = {
-                type: 'update',
-                ops: ops
-              }
-              if (!broadcastHB) { // TODO: consider to broadcast here..
-                conn.send(sender, m)
-              } else {
-                // broadcast only once!
-                conn.broadcast(m)
-              }
-            }
-            resolve()
-          })
-        })
-      })
-    } else if (m.type === 'sync done') {
-      var self = this
-      this.syncStep2.then(function () {
-        self._setSyncedWith(sender)
-      })
-    } else if (m.type === 'update') {
-      if (this.forwardToSyncingClients) {
-        for (var client of this.syncingClients) {
-          this.send(client, m)
-        }
-      }
-      this.y.db.apply(m.ops)
-    }
-  }
-  _setSyncedWith (user) {
-    var conn = this.connections[user]
-    if (conn != null) {
-      conn.isSynced = true
-    }
-    if (user === this.currentSyncTarget) {
-      this.currentSyncTarget = null
-      this.findNextSyncTarget()
-    }
-  }
-  /*
-    Currently, the HB encodes operations as JSON. For the moment I want to keep it
-    that way. Maybe we support encoding in the HB as XML in the future, but for now I don't want
-    too much overhead. Y is very likely to get changed a lot in the future
-
-    Because we don't want to encode JSON as string (with character escaping, wich makes it pretty much unreadable)
-    we encode the JSON as XML.
-
-    When the HB support encoding as XML, the format should look pretty much like this.
-
-    does not support primitive values as array elements
-    expects an ltx (less than xml) object
-  */
-  parseMessageFromXml (m) {
-    function parseArray (node) {
-      for (var n of node.children) {
-        if (n.getAttribute('isArray') === 'true') {
-          return parseArray(n)
-        } else {
-          return parseObject(n)
-        }
-      }
-    }
-    function parseObject (node) {
-      var json = {}
-      for (var attrName in node.attrs) {
-        var value = node.attrs[attrName]
-        var int = parseInt(value, 10)
-        if (isNaN(int) || ('' + int) !== value) {
-          json[attrName] = value
-        } else {
-          json[attrName] = int
-        }
-      }
-      for (var n in node.children) {
-        var name = n.name
-        if (n.getAttribute('isArray') === 'true') {
-          json[name] = parseArray(n)
-        } else {
-          json[name] = parseObject(n)
-        }
-      }
-      return json
-    }
-    parseObject(m)
-  }
-  /*
-    encode message in xml
-    we use string because Strophe only accepts an "xml-string"..
-    So {a:4,b:{c:5}} will look like
-    <y a="4">
-      <b c="5"></b>
-    </y>
-    m - ltx element
-    json - Object
-  */
-  encodeMessageToXml (msg, obj) {
-    // attributes is optional
-    function encodeObject (m, json) {
-      for (var name in json) {
-        var value = json[name]
-        if (name == null) {
-          // nop
-        } else if (value.constructor === Object) {
-          encodeObject(m.c(name), value)
-        } else if (value.constructor === Array) {
-          encodeArray(m.c(name), value)
-        } else {
-          m.setAttribute(name, value)
-        }
-      }
-    }
-    function encodeArray (m, array) {
-      m.setAttribute('isArray', 'true')
-      for (var e of array) {
-        if (e.constructor === Object) {
-          encodeObject(m.c('array-element'), e)
-        } else {
-          encodeArray(m.c('array-element'), e)
-        }
-      }
-    }
-    if (obj.constructor === Object) {
-      encodeObject(msg.c('y', { xmlns: 'http://y.ninja/connector-stanza' }), obj)
-    } else if (obj.constructor === Array) {
-      encodeArray(msg.c('y', { xmlns: 'http://y.ninja/connector-stanza' }), obj)
-    } else {
-      throw new Error("I can't encode this json!")
-    }
-  }
-}
-Y.AbstractConnector = AbstractConnector
--- a/src/Connectors/Test.js
+++ b/src/Connectors/Test.js
@@ -1,136 +0,0 @@
-/* global getRandom, Y, wait, async */
-'use strict'
-
-var globalRoom = {
-  users: {},
-  buffers: {},
-  removeUser: function (user) {
-    for (var i in this.users) {
-      this.users[i].userLeft(user)
-    }
-    delete this.users[user]
-    delete this.buffers[user]
-  },
-  addUser: function (connector) {
-    this.users[connector.userId] = connector
-    this.buffers[connector.userId] = []
-    for (var uname in this.users) {
-      if (uname !== connector.userId) {
-        var u = this.users[uname]
-        u.userJoined(connector.userId, 'master')
-        connector.userJoined(u.userId, 'master')
-      }
-    }
-  }
-}
-Y.utils.globalRoom = globalRoom
-
-function flushOne () {
-  var bufs = []
-  for (var i in globalRoom.buffers) {
-    if (globalRoom.buffers[i].length > 0) {
-      bufs.push(i)
-    }
-  }
-  if (bufs.length > 0) {
-    var userId = getRandom(bufs)
-    var m = globalRoom.buffers[userId].shift()
-    var user = globalRoom.users[userId]
-    user.receiveMessage(m[0], m[1])
-    return true
-  } else {
-    return false
-  }
-}
-
-// setInterval(flushOne, 10)
-
-var userIdCounter = 0
-
-class Test extends Y.AbstractConnector {
-  constructor (y, options) {
-    if (options === undefined) {
-      throw new Error('Options must not be undefined!')
-    }
-    options.role = 'master'
-    options.forwardToSyncingClients = false
-    super(y, options)
-    this.setUserId((userIdCounter++) + '').then(() => {
-      globalRoom.addUser(this)
-    })
-    this.globalRoom = globalRoom
-    this.syncingClientDuration = 0
-  }
-  receiveMessage (sender, m) {
-    super.receiveMessage(sender, JSON.parse(JSON.stringify(m)))
-  }
-  send (userId, message) {
-    var buffer = globalRoom.buffers[userId]
-    if (buffer != null) {
-      buffer.push(JSON.parse(JSON.stringify([this.userId, message])))
-    }
-  }
-  broadcast (message) {
-    for (var key in globalRoom.buffers) {
-      globalRoom.buffers[key].push(JSON.parse(JSON.stringify([this.userId, message])))
-    }
-  }
-  isDisconnected () {
-    return globalRoom.users[this.userId] == null
-  }
-  reconnect () {
-    if (this.isDisconnected()) {
-      globalRoom.addUser(this)
-      super.reconnect()
-    }
-    return this.flushAll()
-  }
-  disconnect () {
-    if (!this.isDisconnected()) {
-      globalRoom.removeUser(this.userId)
-      super.disconnect()
-    }
-    return wait()
-  }
-  flush () {
-    var self = this
-    return async(function * () {
-      yield wait()
-      while (globalRoom.buffers[self.userId].length > 0) {
-        var m = globalRoom.buffers[self.userId].shift()
-        this.receiveMessage(m[0], m[1])
-        yield wait()
-      }
-    })
-  }
-  flushAll () {
-    return new Promise(function (resolve) {
-      // flushes may result in more created operations,
-      // flush until there is nothing more to flush
-      function nextFlush () {
-        var c = flushOne()
-        if (c) {
-          while (flushOne()) {
-            // nop
-          }
-          wait().then(nextFlush)
-        } else {
-          wait().then(function () {
-            resolve()
-          })
-        }
-      }
-      // in the case that there are
-      // still actions that want to be performed
-      wait().then(nextFlush)
-    })
-  }
-  /*
-    Flushes an operation for some user..
-  */
-  flushOne () {
-    flushOne()
-  }
-}
-
-Y.Test = Test
--- a/src/Connectors/WebRTC.js
+++ b/src/Connectors/WebRTC.js
@@ -1,94 +0,0 @@
-/* global Y, SimpleWebRTC */
-'use strict'
-
-class WebRTC extends Y.AbstractConnector {
-  constructor (y, options) {
-    if (options === undefined) {
-      throw new Error('Options must not be undefined!')
-    }
-    if (options.room == null) {
-      throw new Error('You must define a room name!')
-    }
-    options.role = 'slave'
-    super(y, options)
-    this.webrtcOptions = {
-      url: options.url || 'https://yatta.ninja:8888',
-      room: options.room
-    }
-    var swr = new SimpleWebRTC(this.webrtcOptions)
-    this.swr = swr
-    var self = this
-    swr.once('connectionReady', function (userId) {
-      // SimpleWebRTC (swr) is initialized
-      swr.joinRoom(self.webrtcOptions.room)
-
-      swr.once('joinedRoom', function () {
-        self.setUserId(userId)
-        /*
-        var i
-        // notify the connector class about all the users that already
-        // joined the session
-        for(i in self.swr.webrtc.peers){
-          self.userJoined(self.swr.webrtc.peers[i].id, "master")
-        }*/
-        swr.on('channelMessage', function (peer, room_, message) {
-          // The client received a message
-          // Check if the connector is already initialized,
-          // only then forward the message to the connector class
-          if (message.type != null) {
-            self.receiveMessage(peer.id, message.payload)
-          }
-        })
-      })
-
-      swr.on('createdPeer', function (peer) {
-        // a new peer/client joined the session.
-        // Notify the connector class, if the connector
-        // is already initialized
-        self.userJoined(peer.id, 'master')
-      })
-
-      swr.on('peerStreamRemoved', function (peer) {
-        // a client left the session.
-        // Notify the connector class, if the connector
-        // is already initialized
-        self.userLeft(peer.id)
-      })
-    })
-  }
-  disconnect () {
-    this.swr.leaveRoom()
-    super.disconnect()
-  }
-  reconnect () {
-    this.swr.joinRoom(this.webrtcOptions.room)
-    super.reconnect()
-  }
-  send (uid, message) {
-    var self = this
-    // we have to make sure that the message is sent under all circumstances
-    var send = function () {
-      // check if the clients still exists
-      var peer = self.swr.webrtc.getPeers(uid)[0]
-      var success
-      if (peer) {
-        // success is true, if the message is successfully sent
-        success = peer.sendDirectly('simplewebrtc', 'yjs', message)
-      }
-      if (!success) {
-        // resend the message if it didn't work
-        setTimeout(send, 500)
-      }
-    }
-    // try to send the message
-    send()
-  }
-  broadcast (message) {
-    this.swr.sendDirectlyToAll('simplewebrtc', 'yjs', message)
-  }
-  isDisconnected () {
-    return false
-  }
-}
-
-Y.WebRTC = WebRTC
--- a/src/Database.js
+++ b/src/Database.js
@@ -1,341 +0,0 @@
-/* global Y */
-'use strict'
-
-/*
-  Partial definition of an OperationStore.
-  TODO: name it Database, operation store only holds operations.
-
-  A database definition must alse define the following methods:
-  * logTable() (optional)
-    - show relevant information information in a table
-  * requestTransaction(makeGen)
-    - request a transaction
-  * destroy()
-    - destroy the database
-*/
-class AbstractDatabase {
-  constructor (y, opts) {
-    this.y = y
-    // E.g. this.listenersById[id] : Array<Listener>
-    this.listenersById = {}
-    // Execute the next time a transaction is requested
-    this.listenersByIdExecuteNow = []
-    // A transaction is requested
-    this.listenersByIdRequestPending = false
-    /* To make things more clear, the following naming conventions:
-       * ls : we put this.listenersById on ls
-       * l : Array<Listener>
-       * id : Id (can't use as property name)
-       * sid : String (converted from id via JSON.stringify
-                       so we can use it as a property name)
-
-      Always remember to first overwrite
-      a property before you iterate over it!
-    */
-    // TODO: Use ES7 Weak Maps. This way types that are no longer user,
-    // wont be kept in memory.
-    this.initializedTypes = {}
-    this.whenUserIdSetListener = null
-    this.waitingTransactions = []
-    this.transactionInProgress = false
-    if (typeof YConcurrency_TestingMode !== 'undefined') {
-      this.executeOrder = []
-    }
-    this.gc1 = [] // first stage
-    this.gc2 = [] // second stage -> after that, remove the op
-    this.gcTimeout = opts.gcTimeout || 5000
-    var os = this
-    function garbageCollect () {
-      return new Promise((resolve) => {
-        os.requestTransaction(function * () {
-          if (os.y.connector != null && os.y.connector.isSynced) {
-            for (var i in os.gc2) {
-              var oid = os.gc2[i]
-              yield* this.garbageCollectOperation(oid)
-            }
-            os.gc2 = os.gc1
-            os.gc1 = []
-          }
-          if (os.gcTimeout > 0) {
-            os.gcInterval = setTimeout(garbageCollect, os.gcTimeout)
-          }
-          resolve()
-        })
-      })
-    }
-    this.garbageCollect = garbageCollect
-    if (this.gcTimeout > 0) {
-      garbageCollect()
-    }
-  }
-  addToDebug () {
-    if (typeof YConcurrency_TestingMode !== 'undefined') {
-      var command = Array.prototype.map.call(arguments, function (s) {
-        if (typeof s === 'string') {
-          return s
-        } else {
-          return JSON.stringify(s)
-        }
-      }).join('').replace(/"/g, "'").replace(/,/g, ', ').replace(/:/g, ': ')
-      this.executeOrder.push(command)
-    }
-  }
-  getDebugData () {
-    console.log(this.executeOrder.join('\n'))
-  }
-  stopGarbageCollector () {
-    var self = this
-    return new Promise(function (resolve) {
-      self.requestTransaction(function * () {
-        var ungc = self.gc1.concat(self.gc2)
-        self.gc1 = []
-        self.gc2 = []
-        for (var i in ungc) {
-          var op = yield* this.getOperation(ungc[i])
-          delete op.gc
-          yield* this.setOperation(op)
-        }
-        resolve()
-      })
-    })
-  }
-  /*
-    Try to add to GC.
-
-    TODO: rename this function
-
-    Rulez:
-    * Only gc if this user is online
-    * The most left element in a list must not be gc'd.
-      => There is at least one element in the list
-
-    returns true iff op was added to GC
-  */
-  addToGarbageCollector (op, left) {
-    if (
-      op.gc == null &&
-      op.deleted === true &&
-      this.y.connector.isSynced &&
-      left != null &&
-      left.deleted === true
-    ) {
-      op.gc = true
-      this.gc1.push(op.id)
-      return true
-    } else {
-      return false
-    }
-  }
-  removeFromGarbageCollector (op) {
-    function filter (o) {
-      return !Y.utils.compareIds(o, op.id)
-    }
-    this.gc1 = this.gc1.filter(filter)
-    this.gc2 = this.gc2.filter(filter)
-    delete op.gc
-  }
-  destroy () {
-    clearInterval(this.gcInterval)
-    this.gcInterval = null
-  }
-  setUserId (userId) {
-    var self = this
-    return new Promise(function (resolve) {
-      self.requestTransaction(function * () {
-        self.userId = userId
-        self.opClock = (yield* this.getState(userId)).clock
-        if (self.whenUserIdSetListener != null) {
-          self.whenUserIdSetListener()
-          self.whenUserIdSetListener = null
-        }
-        resolve()
-      })
-    })
-  }
-  whenUserIdSet (f) {
-    if (this.userId != null) {
-      f()
-    } else {
-      this.whenUserIdSetListener = f
-    }
-  }
-  getNextOpId () {
-    if (this.userId == null) {
-      throw new Error('OperationStore not yet initialized!')
-    }
-    return [this.userId, this.opClock++]
-  }
-  /*
-    Apply a list of operations.
-
-    * get a transaction
-    * check whether all Struct.*.requiredOps are in the OS
-    * check if it is an expected op (otherwise wait for it)
-    * check if was deleted, apply a delete operation after op was applied
-  */
-  apply (ops) {
-    for (var key in ops) {
-      var o = ops[key]
-      var required = Y.Struct[o.struct].requiredOps(o)
-      this.whenOperationsExist(required, o)
-    }
-  }
-  /*
-    op is executed as soon as every operation requested is available.
-    Note that Transaction can (and should) buffer requests.
-  */
-  whenOperationsExist (ids, op) {
-    if (ids.length > 0) {
-      let listener = {
-        op: op,
-        missing: ids.length
-      }
-
-      for (let key in ids) {
-        let id = ids[key]
-        let sid = JSON.stringify(id)
-        let l = this.listenersById[sid]
-        if (l == null) {
-          l = []
-          this.listenersById[sid] = l
-        }
-        l.push(listener)
-      }
-    } else {
-      this.listenersByIdExecuteNow.push({
-        op: op
-      })
-    }
-
-    if (this.listenersByIdRequestPending) {
-      return
-    }
-
-    this.listenersByIdRequestPending = true
-    var store = this
-
-    this.requestTransaction(function * () {
-      var exeNow = store.listenersByIdExecuteNow
-      store.listenersByIdExecuteNow = []
-
-      var ls = store.listenersById
-      store.listenersById = {}
-
-      store.listenersByIdRequestPending = false
-
-      for (let key in exeNow) {
-        let o = exeNow[key].op
-        yield* store.tryExecute.call(this, o)
-      }
-
-      for (var sid in ls) {
-        var l = ls[sid]
-        var id = JSON.parse(sid)
-        if ((yield* this.getOperation(id)) == null) {
-          store.listenersById[sid] = l
-        } else {
-          for (let key in l) {
-            let listener = l[key]
-            let o = listener.op
-            if (--listener.missing === 0) {
-              yield* store.tryExecute.call(this, o)
-            }
-          }
-        }
-      }
-    })
-  }
-  /*
-    Actually execute an operation, when all expected operations are available.
-  */
-  * tryExecute (op) {
-    this.store.addToDebug('yield* this.store.tryExecute.call(this, ', JSON.stringify(op), ')')
-    if (op.struct === 'Delete') {
-      yield* Y.Struct.Delete.execute.call(this, op)
-      yield* this.store.operationAdded(this, op)
-    } else if ((yield* this.getOperation(op.id)) == null && !(yield* this.isGarbageCollected(op.id))) {
-      yield* Y.Struct[op.struct].execute.call(this, op)
-      yield* this.addOperation(op)
-      yield* this.store.operationAdded(this, op)
-    }
-  }
-  // called by a transaction when an operation is added
-  * operationAdded (transaction, op) {
-    if (op.struct === 'Delete') {
-      var target = yield* transaction.getOperation(op.target)
-      if (target != null) {
-        var type = transaction.store.initializedTypes[JSON.stringify(target.parent)]
-        if (type != null) {
-          yield* type._changed(transaction, {
-            struct: 'Delete',
-            target: op.target
-          })
-        }
-      }
-    } else {
-      // increase SS
-      var o = op
-      var state = yield* transaction.getState(op.id[0])
-      while (o != null && o.id[1] === state.clock && op.id[0] === o.id[0]) {
-        // either its a new operation (1. case), or it is an operation that was deleted, but is not yet in the OS
-        state.clock++
-        yield* transaction.checkDeleteStoreForState(state)
-        o = yield* transaction.os.findNext(o.id)
-      }
-      yield* transaction.setState(state)
-
-      // notify whenOperation listeners (by id)
-      var sid = JSON.stringify(op.id)
-      var l = this.listenersById[sid]
-      delete this.listenersById[sid]
-
-      if (l != null) {
-        for (var key in l) {
-          var listener = l[key]
-          if (--listener.missing === 0) {
-            this.whenOperationsExist([], listener.op)
-          }
-        }
-      }
-      var t = this.initializedTypes[JSON.stringify(op.parent)]
-      // notify parent, if it has been initialized as a custom type
-      if (t != null) {
-        yield* t._changed(transaction, Y.utils.copyObject(op))
-      }
-
-      // Delete if DS says this is actually deleted
-      if (!op.deleted && (yield* transaction.isDeleted(op.id))) {
-        var delop = {
-          struct: 'Delete',
-          target: op.id
-        }
-        yield* Y.Struct['Delete'].execute.call(transaction, delop)
-        if (t != null) {
-          yield* t._changed(transaction, delop)
-        }
-      }
-    }
-  }
-  getNextRequest () {
-    if (this.waitingTransactions.length === 0) {
-      this.transactionInProgress = false
-      return null
-    } else {
-      return this.waitingTransactions.shift()
-    }
-  }
-  requestTransaction (makeGen, callImmediately) {
-    if (callImmediately) {
-      this.transact(makeGen)
-    } else if (!this.transactionInProgress) {
-      this.transactionInProgress = true
-      var self = this
-      setTimeout(function () {
-        self.transact(makeGen)
-      }, 0)
-    } else {
-      this.waitingTransactions.push(makeGen)
-    }
-  }
-}
-Y.AbstractDatabase = AbstractDatabase
--- a/src/Database.spec.js
+++ b/src/Database.spec.js
@@ -1,351 +0,0 @@
-/* global Y, async, databases */
-/* eslint-env browser,jasmine,console */
-
-for (let database of databases) {
-  describe(`Database (${database})`, function () {
-    var store
-    describe('DeleteStore', function () {
-      describe('Basic', function () {
-        beforeEach(function () {
-          store = new Y[database](null, {
-            gcTimeout: -1,
-            namespace: 'testing'
-          })
-        })
-        afterEach(function (done) {
-          store.requestTransaction(function * () {
-            yield* this.store.destroy()
-            done()
-          })
-        })
-        it('Deleted operation is deleted', async(function * (done) {
-          store.requestTransaction(function * () {
-            yield* this.markDeleted(['u1', 10])
-            expect(yield* this.isDeleted(['u1', 10])).toBeTruthy()
-            expect(yield* this.getDeleteSet()).toEqual({'u1': [[10, 1, false]]})
-            done()
-          })
-        }))
-        it('Deleted operation extends other deleted operation', async(function * (done) {
-          store.requestTransaction(function * () {
-            yield* this.markDeleted(['u1', 10])
-            yield* this.markDeleted(['u1', 11])
-            expect(yield* this.isDeleted(['u1', 10])).toBeTruthy()
-            expect(yield* this.isDeleted(['u1', 11])).toBeTruthy()
-            expect(yield* this.getDeleteSet()).toEqual({'u1': [[10, 2, false]]})
-            done()
-          })
-        }))
-        it('Deleted operation extends other deleted operation', async(function * (done) {
-          store.requestTransaction(function * () {
-            yield* this.markDeleted(['0', 3])
-            yield* this.markDeleted(['0', 4])
-            yield* this.markDeleted(['0', 2])
-            expect(yield* this.getDeleteSet()).toEqual({'0': [[2, 3, false]]})
-            done()
-          })
-        }))
-        it('Debug #1', async(function * (done) {
-          store.requestTransaction(function * () {
-            yield* this.markDeleted(['166', 0])
-            yield* this.markDeleted(['166', 2])
-            yield* this.markDeleted(['166', 0])
-            yield* this.markDeleted(['166', 2])
-            yield* this.markGarbageCollected(['166', 2])
-            yield* this.markDeleted(['166', 1])
-            yield* this.markDeleted(['166', 3])
-            yield* this.markGarbageCollected(['166', 3])
-            yield* this.markDeleted(['166', 0])
-            expect(yield* this.getDeleteSet()).toEqual({'166': [[0, 2, false], [2, 2, true]]})
-            done()
-          })
-        }))
-        it('Debug #2', async(function * (done) {
-          store.requestTransaction(function * () {
-            yield* this.markDeleted(['293', 0])
-            yield* this.markDeleted(['291', 2])
-            yield* this.markDeleted(['291', 2])
-            yield* this.markGarbageCollected(['293', 0])
-            yield* this.markDeleted(['293', 1])
-            yield* this.markGarbageCollected(['291', 2])
-            expect(yield* this.getDeleteSet()).toEqual({'291': [[2, 1, true]], '293': [[0, 1, true], [1, 1, false]]})
-            done()
-          })
-        }))
-        it('Debug #3', async(function * (done) {
-          store.requestTransaction(function * () {
-            yield* this.markDeleted(['581', 0])
-            yield* this.markDeleted(['581', 1])
-            yield* this.markDeleted(['580', 0])
-            yield* this.markDeleted(['580', 0])
-            yield* this.markGarbageCollected(['581', 0])
-            yield* this.markDeleted(['581', 2])
-            yield* this.markDeleted(['580', 1])
-            yield* this.markDeleted(['580', 2])
-            yield* this.markDeleted(['580', 1])
-            yield* this.markDeleted(['580', 2])
-            yield* this.markGarbageCollected(['581', 2])
-            yield* this.markGarbageCollected(['581', 1])
-            yield* this.markGarbageCollected(['580', 1])
-            expect(yield* this.getDeleteSet()).toEqual({'580': [[0, 1, false], [1, 1, true], [2, 1, false]], '581': [[0, 3, true]]})
-            done()
-          })
-        }))
-        it('Debug #4', async(function * (done) {
-          store.requestTransaction(function * () {
-            yield* this.markDeleted(['544', 0])
-            yield* this.markDeleted(['543', 2])
-            yield* this.markDeleted(['544', 0])
-            yield* this.markDeleted(['543', 2])
-            yield* this.markGarbageCollected(['544', 0])
-            yield* this.markDeleted(['545', 1])
-            yield* this.markDeleted(['543', 4])
-            yield* this.markDeleted(['543', 3])
-            yield* this.markDeleted(['544', 1])
-            yield* this.markDeleted(['544', 2])
-            yield* this.markDeleted(['544', 1])
-            yield* this.markDeleted(['544', 2])
-            yield* this.markGarbageCollected(['543', 2])
-            yield* this.markGarbageCollected(['543', 4])
-            yield* this.markGarbageCollected(['544', 2])
-            yield* this.markGarbageCollected(['543', 3])
-            expect(yield* this.getDeleteSet()).toEqual({'543': [[2, 3, true]], '544': [[0, 1, true], [1, 1, false], [2, 1, true]], '545': [[1, 1, false]]})
-            done()
-          })
-        }))
-        it('Debug #5', async(function * (done) {
-          store.requestTransaction(function * () {
-            yield* this.applyDeleteSet({'16': [[1, 2, false]], '17': [[0, 1, true], [1, 3, false]]})
-            expect(yield* this.getDeleteSet()).toEqual({'16': [[1, 2, false]], '17': [[0, 1, true], [1, 3, false]]})
-            yield* this.applyDeleteSet({'16': [[1, 2, false]], '17': [[0, 4, true]]})
-            expect(yield* this.getDeleteSet()).toEqual({'16': [[1, 2, false]], '17': [[0, 4, true]]})
-            done()
-          })
-        }))
-        it('Debug #6', async(function * (done) {
-          store.requestTransaction(function * () {
-            yield* this.applyDeleteSet({'40': [[0, 3, false]]})
-            expect(yield* this.getDeleteSet()).toEqual({'40': [[0, 3, false]]})
-            yield* this.applyDeleteSet({'39': [[2, 2, false]], '40': [[0, 1, true], [1, 2, false]], '41': [[2, 1, false]]})
-            expect(yield* this.getDeleteSet()).toEqual({'39': [[2, 2, false]], '40': [[0, 1, true], [1, 2, false]], '41': [[2, 1, false]]})
-            done()
-          })
-        }))
-        it('Debug #7', async(function * (done) {
-          store.requestTransaction(function * () {
-            yield* this.markDeleted(['9', 2])
-            yield* this.markDeleted(['11', 2])
-            yield* this.markDeleted(['11', 4])
-            yield* this.markDeleted(['11', 1])
-            yield* this.markDeleted(['9', 4])
-            yield* this.markDeleted(['10', 0])
-            yield* this.markGarbageCollected(['11', 2])
-            yield* this.markDeleted(['11', 2])
-            yield* this.markGarbageCollected(['11', 3])
-            yield* this.markDeleted(['11', 3])
-            yield* this.markDeleted(['11', 3])
-            yield* this.markDeleted(['9', 4])
-            yield* this.markDeleted(['10', 0])
-            yield* this.markGarbageCollected(['11', 1])
-            yield* this.markDeleted(['11', 1])
-            expect(yield* this.getDeleteSet()).toEqual({'9': [[2, 1, false], [4, 1, false]], '10': [[0, 1, false]], '11': [[1, 3, true], [4, 1, false]]})
-            done()
-          })
-        }))
-      })
-    })
-    describe('OperationStore', function () {
-      describe('Basic Tests', function () {
-        beforeEach(function () {
-          store = new Y[database](null, {
-            gcTimeout: -1,
-            namespace: 'testing'
-          })
-        })
-        afterEach(function (done) {
-          store.requestTransaction(function * () {
-            yield* this.store.destroy()
-            done()
-          })
-        })
-        it('debug #1', function (done) {
-          store.requestTransaction(function * () {
-            yield* this.os.put({id: [2]})
-            yield* this.os.put({id: [0]})
-            yield* this.os.delete([2])
-            yield* this.os.put({id: [1]})
-            expect(yield* this.os.find([0])).toBeTruthy()
-            expect(yield* this.os.find([1])).toBeTruthy()
-            expect(yield* this.os.find([2])).toBeFalsy()
-            done()
-          })
-        })
-        it('can add&retrieve 5 elements', function (done) {
-          store.requestTransaction(function * () {
-            yield* this.os.put({val: 'four', id: [4]})
-            yield* this.os.put({val: 'one', id: [1]})
-            yield* this.os.put({val: 'three', id: [3]})
-            yield* this.os.put({val: 'two', id: [2]})
-            yield* this.os.put({val: 'five', id: [5]})
-            expect((yield* this.os.find([1])).val).toEqual('one')
-            expect((yield* this.os.find([2])).val).toEqual('two')
-            expect((yield* this.os.find([3])).val).toEqual('three')
-            expect((yield* this.os.find([4])).val).toEqual('four')
-            expect((yield* this.os.find([5])).val).toEqual('five')
-            done()
-          })
-        })
-        it('5 elements do not exist anymore after deleting them', function (done) {
-          store.requestTransaction(function * () {
-            yield* this.os.put({val: 'four', id: [4]})
-            yield* this.os.put({val: 'one', id: [1]})
-            yield* this.os.put({val: 'three', id: [3]})
-            yield* this.os.put({val: 'two', id: [2]})
-            yield* this.os.put({val: 'five', id: [5]})
-            yield* this.os.delete([4])
-            expect(yield* this.os.find([4])).not.toBeTruthy()
-            yield* this.os.delete([3])
-            expect(yield* this.os.find([3])).not.toBeTruthy()
-            yield* this.os.delete([2])
-            expect(yield* this.os.find([2])).not.toBeTruthy()
-            yield* this.os.delete([1])
-            expect(yield* this.os.find([1])).not.toBeTruthy()
-            yield* this.os.delete([5])
-            expect(yield* this.os.find([5])).not.toBeTruthy()
-            done()
-          })
-        })
-      })
-      var numberOfOSTests = 1000
-      describe(`Random Tests - after adding&deleting (0.8/0.2) ${numberOfOSTests} times`, function () {
-        var elements = []
-        beforeAll(function (done) {
-          store = new Y[database](null, {
-            gcTimeout: -1,
-            namespace: 'testing'
-          })
-          store.requestTransaction(function * () {
-            for (var i = 0; i < numberOfOSTests; i++) {
-              var r = Math.random()
-              if (r < 0.8) {
-                var obj = [Math.floor(Math.random() * numberOfOSTests * 10000)]
-                if (!(yield* this.os.find(obj))) {
-                  elements.push(obj)
-                  yield* this.os.put({id: obj})
-                }
-              } else if (elements.length > 0) {
-                var elemid = Math.floor(Math.random() * elements.length)
-                var elem = elements[elemid]
-                elements = elements.filter(function (e) {
-                  return !Y.utils.compareIds(e, elem)
-                })
-                yield* this.os.delete(elem)
-              }
-            }
-            done()
-          })
-        })
-        afterAll(function (done) {
-          store.requestTransaction(function * () {
-            yield* this.store.destroy()
-            done()
-          })
-        })
-        it('can find every object', function (done) {
-          store.requestTransaction(function * () {
-            for (var id of elements) {
-              expect((yield* this.os.find(id)).id).toEqual(id)
-            }
-            done()
-          })
-        })
-
-        it('can find every object with lower bound search', function (done) {
-          store.requestTransaction(function * () {
-            for (var id of elements) {
-              var e = yield* this.os.findWithLowerBound(id)
-              expect(e.id).toEqual(id)
-            }
-            done()
-          })
-        })
-
-        it('iterating over a tree with lower bound yields the right amount of results', function (done) {
-          var lowerBound = elements[Math.floor(Math.random() * elements.length)]
-          var expectedResults = elements.filter(function (e, pos) {
-            return (Y.utils.smaller(lowerBound, e) || Y.utils.compareIds(e, lowerBound)) && elements.indexOf(e) === pos
-          }).length
-
-          var actualResults = 0
-          store.requestTransaction(function * () {
-            yield* this.os.iterate(this, lowerBound, null, function * (val) {
-              expect(val).toBeDefined()
-              actualResults++
-            })
-            expect(expectedResults).toEqual(actualResults)
-            done()
-          })
-        })
-
-        it('iterating over a tree without bounds yield the right amount of results', function (done) {
-          var lowerBound = null
-          var expectedResults = elements.filter(function (e, pos) {
-            return elements.indexOf(e) === pos
-          }).length
-          var actualResults = 0
-          store.requestTransaction(function * () {
-            yield* this.os.iterate(this, lowerBound, null, function * (val) {
-              expect(val).toBeDefined()
-              actualResults++
-            })
-            expect(expectedResults).toEqual(actualResults)
-            done()
-          })
-        })
-
-        it('iterating over a tree with upper bound yields the right amount of results', function (done) {
-          var upperBound = elements[Math.floor(Math.random() * elements.length)]
-          var expectedResults = elements.filter(function (e, pos) {
-            return (Y.utils.smaller(e, upperBound) || Y.utils.compareIds(e, upperBound)) && elements.indexOf(e) === pos
-          }).length
-
-          var actualResults = 0
-          store.requestTransaction(function * () {
-            yield* this.os.iterate(this, null, upperBound, function * (val) {
-              expect(val).toBeDefined()
-              actualResults++
-            })
-            expect(expectedResults).toEqual(actualResults)
-            done()
-          })
-        })
-
-        it('iterating over a tree with upper and lower bounds yield the right amount of results', function (done) {
-          var b1 = elements[Math.floor(Math.random() * elements.length)]
-          var b2 = elements[Math.floor(Math.random() * elements.length)]
-          var upperBound, lowerBound
-          if (Y.utils.smaller(b1, b2)) {
-            lowerBound = b1
-            upperBound = b2
-          } else {
-            lowerBound = b2
-            upperBound = b1
-          }
-          var expectedResults = elements.filter(function (e, pos) {
-            return (Y.utils.smaller(lowerBound, e) || Y.utils.compareIds(e, lowerBound)) &&
-              (Y.utils.smaller(e, upperBound) || Y.utils.compareIds(e, upperBound)) && elements.indexOf(e) === pos
-          }).length
-          var actualResults = 0
-          store.requestTransaction(function * () {
-            yield* this.os.iterate(this, lowerBound, upperBound, function * (val) {
-              expect(val).toBeDefined()
-              actualResults++
-            })
-            expect(expectedResults).toEqual(actualResults)
-            done()
-          })
-        })
-      })
-    })
-  })
-}
--- a/src/Databases/IndexedDB.js
+++ b/src/Databases/IndexedDB.js
@@ -1,181 +0,0 @@
-/* global Y */
-
-'use strict'
-
-Y.IndexedDB = (function () {
-  class Store {
-    constructor (transaction, name) {
-      this.store = transaction.objectStore(name)
-    }
-    * find (id) {
-      return yield this.store.get(id)
-    }
-    * put (v) {
-      yield this.store.put(v)
-    }
-    * delete (id) {
-      yield this.store.delete(id)
-    }
-    * findWithLowerBound (start) {
-      return yield this.store.openCursor(window.IDBKeyRange.lowerBound(start))
-    }
-    * findWithUpperBound (end) {
-      return yield this.store.openCursor(window.IDBKeyRange.upperBound(end), 'prev')
-    }
-    * findNext (id) {
-      return yield* this.findWithLowerBound([id[0], id[1] + 1])
-    }
-    * findPrev (id) {
-      return yield* this.findWithUpperBound([id[0], id[1] - 1])
-    }
-    * iterate (t, start, end, gen) {
-      var range = null
-      if (start != null && end != null) {
-        range = window.IDBKeyRange.bound(start, end)
-      } else if (start != null) {
-        range = window.IDBKeyRange.lowerBound(start)
-      } else if (end != null) {
-        range = window.IDBKeyRange.upperBound(end)
-      }
-      var cursorResult = this.store.openCursor(range)
-      while ((yield cursorResult) != null) {
-        yield* gen.call(t, cursorResult.result.value)
-        cursorResult.result.continue()
-      }
-    }
-
-  }
-  class Transaction extends Y.Transaction {
-    constructor (store) {
-      super(store)
-      var transaction = store.db.transaction(['OperationStore', 'StateStore', 'DeleteStore'], 'readwrite')
-      this.store = store
-      this.ss = new Store(transaction, 'StateStore')
-      this.os = new Store(transaction, 'OperationStore')
-      this.ds = new Store(transaction, 'DeleteStore')
-    }
-  }
-  class OperationStore extends Y.AbstractDatabase {
-    constructor (y, opts) {
-      super(y, opts)
-      if (opts == null) {
-        opts = {}
-      }
-      if (opts.namespace == null || typeof opts.namespace !== 'string') {
-        throw new Error('IndexedDB: expect a string (opts.namespace)!')
-      } else {
-        this.namespace = opts.namespace
-      }
-      if (opts.idbVersion != null) {
-        this.idbVersion = opts.idbVersion
-      } else {
-        this.idbVersion = 5
-      }
-      var store = this
-      // initialize database!
-      this.requestTransaction(function * () {
-        store.db = yield window.indexedDB.open(opts.namespace, store.idbVersion)
-      })
-      if (opts.cleanStart) {
-        this.requestTransaction(function * () {
-          yield this.os.store.clear()
-          yield this.ds.store.clear()
-          yield this.ss.store.clear()
-        })
-      }
-      var operationsToAdd = []
-      window.addEventListener('storage', function (event) {
-        if (event.key === '__YJS__' + store.namespace) {
-          operationsToAdd.push(event.newValue)
-          if (operationsToAdd.length === 1) {
-            store.requestTransaction(function * () {
-              var add = operationsToAdd
-              operationsToAdd = []
-              for (var i in add) {
-                // don't call the localStorage event twice..
-                var op = JSON.parse(add[i])
-                if (op.struct !== 'Delete') {
-                  op = yield* this.getOperation(op.id)
-                }
-                yield* this.store.operationAdded(this, op, true)
-              }
-            })
-          }
-        }
-      }, false)
-    }
-    * operationAdded (transaction, op, noAdd) {
-      yield* super.operationAdded(transaction, op)
-      if (!noAdd) {
-        window.localStorage['__YJS__' + this.namespace] = JSON.stringify(op)
-      }
-    }
-    transact (makeGen) {
-      var transaction = this.db != null ? new Transaction(this) : null
-      var store = this
-
-      var gen = makeGen.call(transaction)
-      handleTransactions(gen.next())
-
-      function handleTransactions (result) {
-        var request = result.value
-        if (result.done) {
-          makeGen = store.getNextRequest()
-          if (makeGen != null) {
-            if (transaction == null && store.db != null) {
-              transaction = new Transaction(store)
-            }
-            gen = makeGen.call(transaction)
-            handleTransactions(gen.next())
-          } // else no transaction in progress!
-          return
-        }
-        if (request.constructor === window.IDBRequest) {
-          request.onsuccess = function () {
-            var res = request.result
-            if (res != null && res.constructor === window.IDBCursorWithValue) {
-              res = res.value
-            }
-            handleTransactions(gen.next(res))
-          }
-          request.onerror = function (err) {
-            gen.throw(err)
-          }
-        } else if (request.constructor === window.IDBCursor) {
-          request.onsuccess = function () {
-            handleTransactions(gen.next(request.result != null ? request.result.value : null))
-          }
-          request.onerror = function (err) {
-            gen.throw(err)
-          }
-        } else if (request.constructor === window.IDBOpenDBRequest) {
-          request.onsuccess = function (event) {
-            var db = event.target.result
-            handleTransactions(gen.next(db))
-          }
-          request.onerror = function () {
-            gen.throw("Couldn't open IndexedDB database!")
-          }
-          request.onupgradeneeded = function (event) {
-            var db = event.target.result
-            try {
-              db.createObjectStore('OperationStore', {keyPath: 'id'})
-              db.createObjectStore('DeleteStore', {keyPath: 'id'})
-              db.createObjectStore('StateStore', {keyPath: 'id'})
-            } catch (e) {
-              console.log('Store already exists!')
-            }
-          }
-        } else {
-          gen.throw('You must not yield this type!')
-        }
-      }
-    }
-    // TODO: implement "free"..
-    * destroy () {
-      this.db.close()
-      yield window.indexedDB.deleteDatabase(this.namespace)
-    }
-  }
-  return OperationStore
-})()
--- a/src/Databases/IndexedDB.spec.js
+++ b/src/Databases/IndexedDB.spec.js
@@ -1,19 +0,0 @@
-/* global Y */
-/* eslint-env browser,jasmine */
-
-if (typeof window !== 'undefined' && false) {
-  describe('IndexedDB', function () {
-    var ob
-    beforeAll(function () {
-      ob = new Y.IndexedDB(null, {namespace: 'Test', gcTimeout: -1})
-    })
-
-    afterAll(function (done) {
-      ob.requestTransaction(function *() {
-        yield* ob.removeDatabase()
-        ob = null
-        done()
-      })
-    })
-  })
-}
--- a/src/Databases/Memory.js
+++ b/src/Databases/Memory.js
@@ -1,63 +0,0 @@
-/* global Y */
-'use strict'
-
-Y.Memory = (function () {
-  class Transaction extends Y.Transaction {
-    constructor (store) {
-      super(store)
-      this.store = store
-      this.ss = store.ss
-      this.os = store.os
-      this.ds = store.ds
-    }
-  }
-  class Database extends Y.AbstractDatabase {
-    constructor (y, opts) {
-      super(y, opts)
-      this.os = new Y.utils.RBTree()
-      this.ds = new Y.utils.RBTree()
-      this.ss = new Y.utils.RBTree()
-    }
-    logTable () {
-      var self = this
-      self.requestTransaction(function * () {
-        console.log('User: ', this.store.y.connector.userId, "==============================") // eslint-disable-line
-        console.log("State Set (SS):", yield* this.getStateSet()) // eslint-disable-line
-        console.log("Operation Store (OS):") // eslint-disable-line
-        yield* this.os.logTable() // eslint-disable-line
-        console.log("Deletion Store (DS):") //eslint-disable-line
-        yield* this.ds.logTable() // eslint-disable-line
-        if (this.store.gc1.length > 0 || this.store.gc2.length > 0) {
-          console.warn('GC1|2 not empty!', this.store.gc1, this.store.gc2)
-        }
-        if (JSON.stringify(this.store.listenersById) !== '{}') {
-          console.warn('listenersById not empty!')
-        }
-        if (JSON.stringify(this.store.listenersByIdExecuteNow) !== '[]') {
-          console.warn('listenersByIdExecuteNow not empty!')
-        }
-        if (this.store.transactionInProgress) {
-          console.warn('Transaction still in progress!')
-        }
-      }, true)
-    }
-    transact (makeGen) {
-      var t = new Transaction(this)
-      while (makeGen !== null) {
-        var gen = makeGen.call(t)
-        var res = gen.next()
-        while (!res.done) {
-          res = gen.next(res.value)
-        }
-        makeGen = this.getNextRequest()
-      }
-    }
-    * destroy () {
-      super.destroy()
-      delete this.os
-      delete this.ss
-      delete this.ds
-    }
-  }
-  return Database
-})()
--- a/src/Databases/RedBlackTree.js
+++ b/src/Databases/RedBlackTree.js
@@ -1,489 +0,0 @@
-/* global Y */
-'use strict'
-
-/*
-  This file contains a not so fancy implemantion of a Red Black Tree.
-*/
-
-class N {
-  // A created node is always red!
-  constructor (val) {
-    this.val = val
-    this.color = true
-    this._left = null
-    this._right = null
-    this._parent = null
-    if (val.id === null) {
-      throw new Error('You must define id!')
-    }
-  }
-  isRed () { return this.color }
-  isBlack () { return !this.color }
-  redden () { this.color = true; return this }
-  blacken () { this.color = false; return this }
-  get grandparent () {
-    return this.parent.parent
-  }
-  get parent () {
-    return this._parent
-  }
-  get sibling () {
-    return (this === this.parent.left)
-      ? this.parent.right : this.parent.left
-  }
-  get left () {
-    return this._left
-  }
-  get right () {
-    return this._right
-  }
-  set left (n) {
-    if (n !== null) {
-      n._parent = this
-    }
-    this._left = n
-  }
-  set right (n) {
-    if (n !== null) {
-      n._parent = this
-    }
-    this._right = n
-  }
-  rotateLeft (tree) {
-    var parent = this.parent
-    var newParent = this.right
-    var newRight = this.right.left
-    newParent.left = this
-    this.right = newRight
-    if (parent === null) {
-      tree.root = newParent
-      newParent._parent = null
-    } else if (parent.left === this) {
-      parent.left = newParent
-    } else if (parent.right === this) {
-      parent.right = newParent
-    } else {
-      throw new Error('The elements are wrongly connected!')
-    }
-  }
-  next () {
-    if (this.right !== null) {
-      // search the most left node in the right tree
-      var o = this.right
-      while (o.left !== null) {
-        o = o.left
-      }
-      return o
-    } else {
-      var p = this
-      while (p.parent !== null && p !== p.parent.left) {
-        p = p.parent
-      }
-      return p.parent
-    }
-  }
-  prev () {
-    if (this.left !== null) {
-      // search the most right node in the left tree
-      var o = this.left
-      while (o.right !== null) {
-        o = o.right
-      }
-      return o
-    } else {
-      var p = this
-      while (p.parent !== null && p !== p.parent.right) {
-        p = p.parent
-      }
-      return p.parent
-    }
-  }
-  rotateRight (tree) {
-    var parent = this.parent
-    var newParent = this.left
-    var newLeft = this.left.right
-    newParent.right = this
-    this.left = newLeft
-    if (parent === null) {
-      tree.root = newParent
-      newParent._parent = null
-    } else if (parent.left === this) {
-      parent.left = newParent
-    } else if (parent.right === this) {
-      parent.right = newParent
-    } else {
-      throw new Error('The elements are wrongly connected!')
-    }
-  }
-  getUncle () {
-    // we can assume that grandparent exists when this is called!
-    if (this.parent === this.parent.parent.left) {
-      return this.parent.parent.right
-    } else {
-      return this.parent.parent.left
-    }
-  }
-}
-
-class RBTree {
-  constructor () {
-    this.root = null
-    this.length = 0
-  }
-  * findNext (id) {
-    return yield* this.findWithLowerBound([id[0], id[1] + 1])
-  }
-  * findPrev (id) {
-    return yield* this.findWithUpperBound([id[0], id[1] - 1])
-  }
-  findNodeWithLowerBound (from) {
-    if (from === void 0) {
-      throw new Error('You must define from!')
-    }
-    var o = this.root
-    if (o === null) {
-      return null
-    } else {
-      while (true) {
-        if ((from === null || Y.utils.smaller(from, o.val.id)) && o.left !== null) {
-          // o is included in the bound
-          // try to find an element that is closer to the bound
-          o = o.left
-        } else if (from !== null && Y.utils.smaller(o.val.id, from)) {
-          // o is not within the bound, maybe one of the right elements is..
-          if (o.right !== null) {
-            o = o.right
-          } else {
-            // there is no right element. Search for the next bigger element,
-            // this should be within the bounds
-            return o.next()
-          }
-        } else {
-          return o
-        }
-      }
-    }
-  }
-  findNodeWithUpperBound (to) {
-    if (to === void 0) {
-      throw new Error('You must define from!')
-    }
-    var o = this.root
-    if (o === null) {
-      return null
-    } else {
-      while (true) {
-        if ((to === null || Y.utils.smaller(o.val.id, to)) && o.right !== null) {
-          // o is included in the bound
-          // try to find an element that is closer to the bound
-          o = o.right
-        } else if (to !== null && Y.utils.smaller(to, o.val.id)) {
-          // o is not within the bound, maybe one of the left elements is..
-          if (o.left !== null) {
-            o = o.left
-          } else {
-            // there is no left element. Search for the prev smaller element,
-            // this should be within the bounds
-            return o.prev()
-          }
-        } else {
-          return o
-        }
-      }
-    }
-  }
-  * findWithLowerBound (from) {
-    var n = this.findNodeWithLowerBound(from)
-    return n == null ? null : n.val
-  }
-  * findWithUpperBound (to) {
-    var n = this.findNodeWithUpperBound(to)
-    return n == null ? null : n.val
-  }
-  * iterate (t, from, to, f) {
-    var o = this.findNodeWithLowerBound(from)
-    while (o !== null && (to === null || Y.utils.smaller(o.val.id, to) || Y.utils.compareIds(o.val.id, to))) {
-      yield* f.call(t, o.val)
-      o = o.next()
-    }
-    return true
-  }
-  * logTable (from, to, filter) {
-    if (filter == null) {
-      filter = function () {
-        return true
-      }
-    }
-    if (from == null) { from = null }
-    if (to == null) { to = null }
-    var os = []
-    yield* this.iterate(this, from, to, function * (o) {
-      if (filter(o)) {
-        var o_ = {}
-        for (var key in o) {
-          if (typeof o[key] === 'object') {
-            o_[key] = JSON.stringify(o[key])
-          } else {
-            o_[key] = o[key]
-          }
-        }
-        os.push(o_)
-      }
-    })
-    if (console.table != null) {
-      console.table(os)
-    }
-  }
-  * find (id) {
-    var n
-    return (n = this.findNode(id)) ? n.val : null
-  }
-  findNode (id) {
-    if (id == null || id.constructor !== Array) {
-      throw new Error('Expect id to be an array!')
-    }
-    var o = this.root
-    if (o === null) {
-      return false
-    } else {
-      while (true) {
-        if (o === null) {
-          return false
-        }
-        if (Y.utils.smaller(id, o.val.id)) {
-          o = o.left
-        } else if (Y.utils.smaller(o.val.id, id)) {
-          o = o.right
-        } else {
-          return o
-        }
-      }
-    }
-  }
-  * delete (id) {
-    if (id == null || id.constructor !== Array) {
-      throw new Error('id is expected to be an Array!')
-    }
-    var d = this.findNode(id)
-    if (d == null) {
-      throw new Error('Element does not exist!')
-    }
-    this.length--
-    if (d.left !== null && d.right !== null) {
-      // switch d with the greates element in the left subtree.
-      // o should have at most one child.
-      var o = d.left
-      // find
-      while (o.right !== null) {
-        o = o.right
-      }
-      // switch
-      d.val = o.val
-      d = o
-    }
-    // d has at most one child
-    // let n be the node that replaces d
-    var isFakeChild
-    var child = d.left || d.right
-    if (child === null) {
-      isFakeChild = true
-      child = new N({id: 0})
-      child.blacken()
-      d.right = child
-    } else {
-      isFakeChild = false
-    }
-
-    if (d.parent === null) {
-      if (!isFakeChild) {
-        this.root = child
-        child.blacken()
-        child._parent = null
-      } else {
-        this.root = null
-      }
-      return
-    } else if (d.parent.left === d) {
-      d.parent.left = child
-    } else if (d.parent.right === d) {
-      d.parent.right = child
-    } else {
-      throw new Error('Impossible!')
-    }
-    if (d.isBlack()) {
-      if (child.isRed()) {
-        child.blacken()
-      } else {
-        this._fixDelete(child)
-      }
-    }
-    this.root.blacken()
-    if (isFakeChild) {
-      if (child.parent.left === child) {
-        child.parent.left = null
-      } else if (child.parent.right === child) {
-        child.parent.right = null
-      } else {
-        throw new Error('Impossible #3')
-      }
-    }
-  }
-  _fixDelete (n) {
-    function isBlack (node) {
-      return node !== null ? node.isBlack() : true
-    }
-    function isRed (node) {
-      return node !== null ? node.isRed() : false
-    }
-    if (n.parent === null) {
-      // this can only be called after the first iteration of fixDelete.
-      return
-    }
-    // d was already replaced by the child
-    // d is not the root
-    // d and child are black
-    var sibling = n.sibling
-    if (isRed(sibling)) {
-      // make sibling the grandfather
-      n.parent.redden()
-      sibling.blacken()
-      if (n === n.parent.left) {
-        n.parent.rotateLeft(this)
-      } else if (n === n.parent.right) {
-        n.parent.rotateRight(this)
-      } else {
-        throw new Error('Impossible #2')
-      }
-      sibling = n.sibling
-    }
-    // parent, sibling, and children of n are black
-    if (n.parent.isBlack() &&
-      sibling.isBlack() &&
-      isBlack(sibling.left) &&
-      isBlack(sibling.right)
-    ) {
-      sibling.redden()
-      this._fixDelete(n.parent)
-    } else if (n.parent.isRed() &&
-      sibling.isBlack() &&
-      isBlack(sibling.left) &&
-      isBlack(sibling.right)
-    ) {
-      sibling.redden()
-      n.parent.blacken()
-    } else {
-      if (n === n.parent.left &&
-        sibling.isBlack() &&
-        isRed(sibling.left) &&
-        isBlack(sibling.right)
-      ) {
-        sibling.redden()
-        sibling.left.blacken()
-        sibling.rotateRight(this)
-        sibling = n.sibling
-      } else if (n === n.parent.right &&
-        sibling.isBlack() &&
-        isRed(sibling.right) &&
-        isBlack(sibling.left)
-      ) {
-        sibling.redden()
-        sibling.right.blacken()
-        sibling.rotateLeft(this)
-        sibling = n.sibling
-      }
-      sibling.color = n.parent.color
-      n.parent.blacken()
-      if (n === n.parent.left) {
-        sibling.right.blacken()
-        n.parent.rotateLeft(this)
-      } else {
-        sibling.left.blacken()
-        n.parent.rotateRight(this)
-      }
-    }
-  }
-  * put (v) {
-    if (v == null || v.id == null || v.id.constructor !== Array) {
-      throw new Error('v is expected to have an id property which is an Array!')
-    }
-    var node = new N(v)
-    if (this.root !== null) {
-      var p = this.root // p abbrev. parent
-      while (true) {
-        if (Y.utils.smaller(node.val.id, p.val.id)) {
-          if (p.left === null) {
-            p.left = node
-            break
-          } else {
-            p = p.left
-          }
-        } else if (Y.utils.smaller(p.val.id, node.val.id)) {
-          if (p.right === null) {
-            p.right = node
-            break
-          } else {
-            p = p.right
-          }
-        } else {
-          p.val = node.val
-          return p
-        }
-      }
-      this._fixInsert(node)
-    } else {
-      this.root = node
-    }
-    this.length++
-    this.root.blacken()
-    return node
-  }
-  _fixInsert (n) {
-    if (n.parent === null) {
-      n.blacken()
-      return
-    } else if (n.parent.isBlack()) {
-      return
-    }
-    var uncle = n.getUncle()
-    if (uncle !== null && uncle.isRed()) {
-      // Note: parent: red, uncle: red
-      n.parent.blacken()
-      uncle.blacken()
-      n.grandparent.redden()
-      this._fixInsert(n.grandparent)
-    } else {
-      // Note: parent: red, uncle: black or null
-      // Now we transform the tree in such a way that
-      // either of these holds:
-      //   1) grandparent.left.isRed
-      //     and grandparent.left.left.isRed
-      //   2) grandparent.right.isRed
-      //     and grandparent.right.right.isRed
-      if (n === n.parent.right && n.parent === n.grandparent.left) {
-        n.parent.rotateLeft(this)
-        // Since we rotated and want to use the previous
-        // cases, we need to set n in such a way that
-        // n.parent.isRed again
-        n = n.left
-      } else if (n === n.parent.left && n.parent === n.grandparent.right) {
-        n.parent.rotateRight(this)
-        // see above
-        n = n.right
-      }
-      // Case 1) or 2) hold from here on.
-      // Now traverse grandparent, make parent a black node
-      // on the highest level which holds two red nodes.
-      n.parent.blacken()
-      n.grandparent.redden()
-      if (n === n.parent.left) {
-        // Case 1
-        n.grandparent.rotateRight(this)
-      } else {
-        // Case 2
-        n.grandparent.rotateLeft(this)
-      }
-    }
-  }
-}
-
-Y.utils.RBTree = RBTree
--- a/src/Databases/RedBlackTree.spec.js
+++ b/src/Databases/RedBlackTree.spec.js
@@ -1,212 +0,0 @@
-/* global Y */
-/* eslint-env browser,jasmine,console */
-
-var numberOfRBTreeTests = 1000
-
-function itRedNodesDoNotHaveBlackChildren () {
-  it('Red nodes do not have black children', function () {
-    function traverse (n) {
-      if (n == null) {
-        return
-      }
-      if (n.isRed()) {
-        if (n.left != null) {
-          expect(n.left.isRed()).not.toBeTruthy()
-        }
-        if (n.right != null) {
-          expect(n.right.isRed()).not.toBeTruthy()
-        }
-      }
-      traverse(n.left)
-      traverse(n.right)
-    }
-    traverse(this.tree.root)
-  })
-}
-
-function itBlackHeightOfSubTreesAreEqual () {
-  it('Black-height of sub-trees are equal', function () {
-    function traverse (n) {
-      if (n == null) {
-        return 0
-      }
-      var sub1 = traverse(n.left)
-      var sub2 = traverse(n.right)
-      expect(sub1).toEqual(sub2)
-      if (n.isRed()) {
-        return sub1
-      } else {
-        return sub1 + 1
-      }
-    }
-    traverse(this.tree.root)
-  })
-}
-
-function itRootNodeIsBlack () {
-  it('root node is black', function () {
-    expect(this.tree.root == null || this.tree.root.isBlack()).toBeTruthy()
-  })
-}
-
-describe('RedBlack Tree', function () {
-  var tree, memory
-  describe('debug #2', function () {
-    beforeAll(function (done) {
-      this.memory = new Y.Memory(null, {
-        name: 'Memory',
-        gcTimeout: -1
-      })
-      this.tree = this.memory.os
-      tree = this.tree
-      memory = this.memory
-      memory.requestTransaction(function * () {
-        yield* tree.put({id: [8433]})
-        yield* tree.put({id: [12844]})
-        yield* tree.put({id: [1795]})
-        yield* tree.put({id: [30302]})
-        yield* tree.put({id: [64287]})
-        yield* tree.delete([8433])
-        yield* tree.put({id: [28996]})
-        yield* tree.delete([64287])
-        yield* tree.put({id: [22721]})
-        done()
-      })
-    })
-
-    itRootNodeIsBlack()
-    itBlackHeightOfSubTreesAreEqual([])
-  })
-
-  describe(`After adding&deleting (0.8/0.2) ${numberOfRBTreeTests} times`, function () {
-    var elements = []
-    beforeAll(function (done) {
-      this.memory = new Y.Memory(null, {
-        name: 'Memory',
-        gcTimeout: -1
-      })
-      this.tree = this.memory.os
-      tree = this.tree
-      memory = this.memory
-      memory.requestTransaction(function * () {
-        for (var i = 0; i < numberOfRBTreeTests; i++) {
-          var r = Math.random()
-          if (r < 0.8) {
-            var obj = [Math.floor(Math.random() * numberOfRBTreeTests * 10000)]
-            if (!tree.findNode(obj)) {
-              elements.push(obj)
-              yield* tree.put({id: obj})
-            }
-          } else if (elements.length > 0) {
-            var elemid = Math.floor(Math.random() * elements.length)
-            var elem = elements[elemid]
-            elements = elements.filter(function (e) {
-              return !Y.utils.compareIds(e, elem)
-            })
-            yield* tree.delete(elem)
-          }
-        }
-        done()
-      })
-    })
-
-    itRootNodeIsBlack()
-
-    it('can find every object', function (done) {
-      memory.requestTransaction(function * () {
-        for (var id of elements) {
-          expect((yield* tree.find(id)).id).toEqual(id)
-        }
-        done()
-      })
-    })
-
-    it('can find every object with lower bound search', function (done) {
-      this.memory.requestTransaction(function * () {
-        for (var id of elements) {
-          expect((yield* tree.findWithLowerBound(id)).id).toEqual(id)
-        }
-        done()
-      })
-    })
-    itRedNodesDoNotHaveBlackChildren()
-
-    itBlackHeightOfSubTreesAreEqual()
-
-    it('iterating over a tree with lower bound yields the right amount of results', function (done) {
-      var lowerBound = elements[Math.floor(Math.random() * elements.length)]
-      var expectedResults = elements.filter(function (e, pos) {
-        return (Y.utils.smaller(lowerBound, e) || Y.utils.compareIds(e, lowerBound)) && elements.indexOf(e) === pos
-      }).length
-
-      var actualResults = 0
-      this.memory.requestTransaction(function * () {
-        yield* tree.iterate(this, lowerBound, null, function * (val) {
-          expect(val).toBeDefined()
-          actualResults++
-        })
-        expect(expectedResults).toEqual(actualResults)
-        done()
-      })
-    })
-
-    it('iterating over a tree without bounds yield the right amount of results', function (done) {
-      var lowerBound = null
-      var expectedResults = elements.filter(function (e, pos) {
-        return elements.indexOf(e) === pos
-      }).length
-      var actualResults = 0
-      this.memory.requestTransaction(function * () {
-        yield* tree.iterate(this, lowerBound, null, function * (val) {
-          expect(val).toBeDefined()
-          actualResults++
-        })
-        expect(expectedResults).toEqual(actualResults)
-        done()
-      })
-    })
-
-    it('iterating over a tree with upper bound yields the right amount of results', function (done) {
-      var upperBound = elements[Math.floor(Math.random() * elements.length)]
-      var expectedResults = elements.filter(function (e, pos) {
-        return (Y.utils.smaller(e, upperBound) || Y.utils.compareIds(e, upperBound)) && elements.indexOf(e) === pos
-      }).length
-
-      var actualResults = 0
-      this.memory.requestTransaction(function * () {
-        yield* tree.iterate(this, null, upperBound, function * (val) {
-          expect(val).toBeDefined()
-          actualResults++
-        })
-        expect(expectedResults).toEqual(actualResults)
-        done()
-      })
-    })
-
-    it('iterating over a tree with upper and lower bounds yield the right amount of results', function (done) {
-      var b1 = elements[Math.floor(Math.random() * elements.length)]
-      var b2 = elements[Math.floor(Math.random() * elements.length)]
-      var upperBound, lowerBound
-      if (Y.utils.smaller(b1, b2)) {
-        lowerBound = b1
-        upperBound = b2
-      } else {
-        lowerBound = b2
-        upperBound = b1
-      }
-      var expectedResults = elements.filter(function (e, pos) {
-        return (Y.utils.smaller(lowerBound, e) || Y.utils.compareIds(e, lowerBound)) &&
-          (Y.utils.smaller(e, upperBound) || Y.utils.compareIds(e, upperBound)) && elements.indexOf(e) === pos
-      }).length
-      var actualResults = 0
-      this.memory.requestTransaction(function * () {
-        yield* tree.iterate(this, lowerBound, upperBound, function * (val) {
-          expect(val).toBeDefined()
-          actualResults++
-        })
-        expect(expectedResults).toEqual(actualResults)
-        done()
-      })
-    })
-  })
-})
--- a/src/Helper.spec.js
+++ b/src/Helper.spec.js
@@ -1,288 +0,0 @@
-/* global Y */
-/* eslint-env browser, jasmine */
-
-/*
-  This is just a compilation of functions that help to test this library!
-*/
-
-// When testing, you store everything on the global object. We call it g
-var g
-if (typeof global !== 'undefined') {
-  g = global
-} else if (typeof window !== 'undefined') {
-  g = window
-} else {
-  throw new Error('No global object?')
-}
-g.g = g
-
-g.YConcurrency_TestingMode = true
-
-jasmine.DEFAULT_TIMEOUT_INTERVAL = 20000
-
-g.describeManyTimes = function describeManyTimes (times, name, f) {
-  for (var i = 0; i < times; i++) {
-    describe(name, f)
-  }
-}
-
-/*
-  Wait for a specified amount of time (in ms). defaults to 5ms
-*/
-function wait (t) {
-  if (t == null) {
-    t = 80
-  }
-  return new Promise(function (resolve) {
-    setTimeout(function () {
-      resolve()
-    }, t * 2)
-  })
-}
-g.wait = wait
-
-g.databases = ['Memory']
-if (typeof window !== 'undefined') {
-  g.databases.push('IndexedDB')
-}
-
-/*
-  returns a random element of o.
-  works on Object, and Array
-*/
-function getRandom (o) {
-  if (o instanceof Array) {
-    return o[Math.floor(Math.random() * o.length)]
-  } else if (o.constructor === Object) {
-    var ks = []
-    for (var key in o) {
-      ks.push(key)
-    }
-    return o[getRandom(ks)]
-  }
-}
-g.getRandom = getRandom
-
-function getRandomNumber (n) {
-  if (n == null) {
-    n = 9999
-  }
-  return Math.floor(Math.random() * n)
-}
-g.getRandomNumber = getRandomNumber
-
-function * applyTransactions (relAmount, numberOfTransactions, objects, users, transactions) {
-  function randomTransaction (root) {
-    var f = getRandom(transactions)
-    f(root)
-  }
-  for (var i = 0; i < numberOfTransactions * relAmount + 1; i++) {
-    var r = Math.random()
-    if (r >= 0.5) {
-      // 50% chance to flush
-      users[0].connector.flushOne() // flushes for some user.. (not necessarily 0)
-    } else if (r >= 0.05) {
-      // 45% chance to create operation
-      randomTransaction(getRandom(objects))
-    } else {
-      // 5% chance to disconnect/reconnect
-      var u = getRandom(users)
-      if (u.connector.isDisconnected()) {
-        yield u.reconnect()
-      } else {
-        yield u.disconnect()
-      }
-    }
-    yield wait()
-  }
-}
-
-g.applyRandomTransactionsAllRejoinNoGC = async(function * applyRandomTransactions (users, objects, transactions, numberOfTransactions) {
-  yield* applyTransactions(1, numberOfTransactions, objects, users, transactions)
-  yield users[0].connector.flushAll()
-  yield wait()
-  for (var u in users) {
-    yield users[u].reconnect()
-  }
-  yield wait(100)
-  yield users[0].connector.flushAll()
-  yield g.garbageCollectAllUsers(users)
-})
-
-g.applyRandomTransactionsWithGC = async(function * applyRandomTransactions (users, objects, transactions, numberOfTransactions) {
-  yield* applyTransactions(1, numberOfTransactions, objects, users.slice(1), transactions)
-  yield users[0].connector.flushAll()
-  yield g.garbageCollectAllUsers(users)
-  yield wait(100)
-  for (var u in users) {
-    // TODO: here, we enforce that two users never sync at the same time with u[0]
-    //       enforce that in the connector itself!
-    yield users[u].reconnect()
-  }
-  yield wait(100)
-  yield users[0].connector.flushAll()
-  yield wait(100)
-  yield g.garbageCollectAllUsers(users)
-})
-
-g.garbageCollectAllUsers = async(function * garbageCollectAllUsers (users) {
-  // gc two times because of the two gc phases (really collect everything)
-  yield wait(100)
-  for (var i in users) {
-    yield users[i].db.garbageCollect()
-    yield users[i].db.garbageCollect()
-  }
-  yield wait(100)
-})
-
-g.compareAllUsers = async(function * compareAllUsers (users) {
-  var s1, s2 // state sets
-  var ds1, ds2 // delete sets
-  var allDels1, allDels2 // all deletions
-  var db1 = [] // operation store of user1
-
-  // t1 and t2 basically do the same. They define t[1,2], ds[1,2], and allDels[1,2]
-  function * t1 () {
-    s1 = yield* this.getStateSet()
-    ds1 = yield* this.getDeleteSet()
-    allDels1 = []
-    yield* this.ds.iterate(this, null, null, function * (d) {
-      allDels1.push(d)
-    })
-  }
-  function * t2 () {
-    s2 = yield* this.getStateSet()
-    ds2 = yield* this.getDeleteSet()
-    allDels2 = []
-    yield* this.ds.iterate(this, null, null, function * (d) {
-      allDels2.push(d)
-    })
-  }
-  yield users[0].connector.flushAll()
-  yield wait()
-  yield g.garbageCollectAllUsers(users)
-
-  for (var uid = 0; uid < users.length; uid++) {
-    var u = users[uid]
-    u.db.requestTransaction(function * () {
-      // compare deleted ops against deleteStore
-      yield* this.os.iterate(this, null, null, function * (o) {
-        if (o.deleted === true) {
-          expect(yield* this.isDeleted(o.id)).toBeTruthy()
-        }
-      })
-      // compare deleteStore against deleted ops
-      var ds = []
-      yield* this.ds.iterate(this, null, null, function * (d) {
-        ds.push(d)
-      })
-      for (var j in ds) {
-        var d = ds[j]
-        for (var i = 0; i < d.len; i++) {
-          var o = yield* this.getOperation([d.id[0], d.id[1] + i])
-          // gc'd or deleted
-          if (d.gc) {
-            expect(o).toBeFalsy()
-          } else {
-            expect(o.deleted).toBeTruthy()
-          }
-        }
-      }
-    })
-    // compare allDels tree
-    yield wait()
-    if (s1 == null) {
-      u.db.requestTransaction(function * () {
-        yield* t1.call(this)
-        yield* this.os.iterate(this, null, null, function * (o) {
-          o = Y.utils.copyObject(o)
-          delete o.origin
-          db1.push(o)
-        })
-      })
-      yield wait()
-    } else {
-      // TODO: make requestTransaction return a promise..
-      u.db.requestTransaction(function * () {
-        yield* t2.call(this)
-        expect(s1).toEqual(s2)
-        expect(allDels1).toEqual(allDels2) // inner structure
-        expect(ds1).toEqual(ds2) // exported structure
-        var count = 0
-        yield* this.os.iterate(this, null, null, function * (o) {
-          o = Y.utils.copyObject(o)
-          delete o.origin
-          expect(db1[count++]).toEqual(o)
-        })
-      })
-      yield wait()
-    }
-  }
-})
-
-g.createUsers = async(function * createUsers (self, numberOfUsers, database) {
-  if (Y.utils.globalRoom.users[0] != null) {
-    yield Y.utils.globalRoom.users[0].flushAll()
-  }
-  // destroy old users
-  for (var u in Y.utils.globalRoom.users) {
-    Y.utils.globalRoom.users[u].y.destroy()
-  }
-  self.users = null
-
-  var promises = []
-  for (var i = 0; i < numberOfUsers; i++) {
-    promises.push(Y({
-      db: {
-        name: database,
-        namespace: 'User ' + i,
-        cleanStart: true,
-        gcTimeout: -1
-      },
-      connector: {
-        name: 'Test',
-        debug: false
-      }
-    }))
-  }
-  self.users = yield Promise.all(promises)
-  return self.users
-})
-
-/*
-  Until async/await arrives in js, we use this function to wait for promises
-  by yielding them.
-*/
-function async (makeGenerator) {
-  return function (arg) {
-    var generator = makeGenerator.apply(this, arguments)
-
-    function handle (result) {
-      if (result.done) return Promise.resolve(result.value)
-
-      return Promise.resolve(result.value).then(function (res) {
-        return handle(generator.next(res))
-      }, function (err) {
-        return handle(generator.throw(err))
-      })
-    }
-    try {
-      return handle(generator.next())
-    } catch (ex) {
-      generator.throw(ex)
-      // return Promise.reject(ex)
-    }
-  }
-}
-g.async = async
-
-function logUsers (self) {
-  if (self.constructor === Array) {
-    self = {users: self}
-  }
-  self.users[0].db.logTable()
-  self.users[1].db.logTable()
-  self.users[2].db.logTable()
-}
-
-g.logUsers = logUsers
--- a/src/Notes.md
+++ b/src/Notes.md
@@ -1,12 +0,0 @@
-
-# Notes
-
-### Terminology
-
-* DB: DataBase that holds all the information of the shared object. It is devided into the OS, DS, and SS. This can be a persistent database or an in-memory database. Depending on the type of database, it could make sense to store OS, DS, and SS in different tables, or maybe different databases.
-* OS: OperationStore holds all the operations. An operation is a js object with a fixed number of name fields.
-* DS: DeleteStore holds the information about which operations are deleted and which operations were garbage collected (no longer available in the OS).
-* SS: StateSet holds the current state of the OS. SS.getState(username) refers to the amount of operations that were received by that respective user.
-* Op: Operation defines an action on a shared type. But it is also the format in which we store the model of a type. This is why it is also called a Struct/Structure.
-* Type and Structure: We crearly distinguish between type and structure. Short explanation: A type (e.g. Strings, Numbers) have a number of functions that you can apply on them. (+) is well defined on both of them. They are *modeled* by a structure - the functions really change the structure of a type. Types can be implemented differently but still provide the same functionality. In Yjs, almost all types are realized as a doubly linked list (on which Yjs can provide eventual convergence)
-*
--- a/src/Struct.js
+++ b/src/Struct.js
@@ -1,336 +0,0 @@
-/* global Y */
-'use strict'
-
-/*
- An operation also defines the structure of a type. This is why operation and
- structure are used interchangeably here.
-
- It must be of the type Object. I hope to achieve some performance
- improvements when working on databases that support the json format.
-
- An operation must have the following properties:
-
- * encode
-     - Encode the structure in a readable format (preferably string- todo)
- * decode (todo)
-     - decode structure to json
- * execute
-     - Execute the semantics of an operation.
- * requiredOps
-     - Operations that are required to execute this operation.
-*/
-
-var Struct = {
-  /* This is the only operation that is actually not a structure, because
-  it is not stored in the OS. This is why it _does not_ have an id
-
-  op = {
-    target: Id
-  }
-  */
-  Delete: {
-    encode: function (op) {
-      return op
-    },
-    requiredOps: function (op) {
-      return [] // [op.target]
-    },
-    execute: function * (op) {
-      return yield* this.deleteOperation(op.target)
-    }
-  },
-  Insert: {
-    /* {
-        content: any,
-        id: Id,
-        left: Id,
-        origin: Id,
-        right: Id,
-        parent: Id,
-        parentSub: string (optional), // child of Map type
-      }
-    */
-    encode: function (op) {
-      // TODO: you could not send the "left" property, then you also have to
-      // "op.left = null" in $execute or $decode
-      var e = {
-        id: op.id,
-        left: op.left,
-        right: op.right,
-        origin: op.origin,
-        parent: op.parent,
-        struct: op.struct
-      }
-      if (op.parentSub != null) {
-        e.parentSub = op.parentSub
-      }
-      if (op.opContent != null) {
-        e.opContent = op.opContent
-      } else {
-        e.content = op.content
-      }
-
-      return e
-    },
-    requiredOps: function (op) {
-      var ids = []
-      if (op.left != null) {
-        ids.push(op.left)
-      }
-      if (op.right != null) {
-        ids.push(op.right)
-      }
-      if (op.origin != null && !Y.utils.compareIds(op.left, op.origin)) {
-        ids.push(op.origin)
-      }
-      // if (op.right == null && op.left == null) {
-      ids.push(op.parent)
-
-      if (op.opContent != null) {
-        ids.push(op.opContent)
-      }
-      return ids
-    },
-    getDistanceToOrigin: function * (op) {
-      if (op.left == null) {
-        return 0
-      } else {
-        var d = 0
-        var o = yield* this.getOperation(op.left)
-        while (!Y.utils.compareIds(op.origin, (o ? o.id : null))) {
-          d++
-          if (o.left == null) {
-            break
-          } else {
-            o = yield* this.getOperation(o.left)
-          }
-        }
-        return d
-      }
-    },
-    /*
-    # $this has to find a unique position between origin and the next known character
-    # case 1: $origin equals $o.origin: the $creator parameter decides if left or right
-    #         let $OL= [o1,o2,o3,o4], whereby $this is to be inserted between o1 and o4
-    #         o2,o3 and o4 origin is 1 (the position of o2)
-    #         there is the case that $this.creator < o2.creator, but o3.creator < $this.creator
-    #         then o2 knows o3. Since on another client $OL could be [o1,o3,o4] the problem is complex
-    #         therefore $this would be always to the right of o3
-    # case 2: $origin < $o.origin
-    #         if current $this insert_position > $o origin: $this ins
-    #         else $insert_position will not change
-    #         (maybe we encounter case 1 later, then this will be to the right of $o)
-    # case 3: $origin > $o.origin
-    #         $this insert_position is to the left of $o (forever!)
-    */
-    execute: function *(op) {
-      var i // loop counter
-      var distanceToOrigin = i = yield* Struct.Insert.getDistanceToOrigin.call(this, op) // most cases: 0 (starts from 0)
-      var o
-      var parent
-      var start
-
-      // find o. o is the first conflicting operation
-      if (op.left != null) {
-        o = yield* this.getOperation(op.left)
-        o = (o.right == null) ? null : yield* this.getOperation(o.right)
-      } else { // left == null
-        parent = yield* this.getOperation(op.parent)
-        let startId = op.parentSub ? parent.map[op.parentSub] : parent.start
-        start = startId == null ? null : yield* this.getOperation(startId)
-        o = start
-      }
-
-      // handle conflicts
-      while (true) {
-        if (o != null && !Y.utils.compareIds(o.id, op.right)) {
-          var oOriginDistance = yield* Struct.Insert.getDistanceToOrigin.call(this, o)
-          if (oOriginDistance === i) {
-            // case 1
-            if (o.id[0] < op.id[0]) {
-              op.left = o.id
-              distanceToOrigin = i + 1
-            }
-          } else if (oOriginDistance < i) {
-            // case 2
-            if (i - distanceToOrigin <= oOriginDistance) {
-              op.left = o.id
-              distanceToOrigin = i + 1
-            }
-          } else {
-            break
-          }
-          i++
-          o = o.right ? yield* this.getOperation(o.right) : null
-        } else {
-          break
-        }
-      }
-
-      // reconnect..
-      var left = null
-      var right = null
-      parent = parent || (yield* this.getOperation(op.parent))
-
-      // reconnect left and set right of op
-      if (op.left != null) {
-        left = yield* this.getOperation(op.left)
-        op.right = left.right
-        left.right = op.id
-
-        yield* this.setOperation(left)
-      } else {
-        op.right = op.parentSub ? parent.map[op.parentSub] || null : parent.start
-      }
-      // reconnect right
-      if (op.right != null) {
-        right = yield* this.getOperation(op.right)
-        right.left = op.id
-
-        // if right exists, and it is supposed to be gc'd. Remove it from the gc
-        if (right.gc != null) {
-          this.store.removeFromGarbageCollector(right)
-        }
-        yield* this.setOperation(right)
-      }
-
-      // update parents .map/start/end properties
-      if (op.parentSub != null) {
-        if (left == null) {
-          parent.map[op.parentSub] = op.id
-          yield* this.setOperation(parent)
-        }
-        // is a child of a map struct.
-        // Then also make sure that only the most left element is not deleted
-        if (op.right != null) {
-          yield* this.deleteOperation(op.right, true)
-        }
-        if (op.left != null) {
-          yield* this.deleteOperation(op.id, true)
-        }
-      } else {
-        if (right == null || left == null) {
-          if (right == null) {
-            parent.end = op.id
-          }
-          if (left == null) {
-            parent.start = op.id
-          }
-          yield* this.setOperation(parent)
-        }
-      }
-    }
-  },
-  List: {
-    /*
-    {
-      start: null,
-      end: null,
-      struct: "List",
-      type: "",
-      id: this.os.getNextOpId()
-    }
-    */
-    encode: function (op) {
-      return {
-        struct: 'List',
-        id: op.id,
-        type: op.type
-      }
-    },
-    requiredOps: function () {
-      /*
-      var ids = []
-      if (op.start != null) {
-        ids.push(op.start)
-      }
-      if (op.end != null){
-        ids.push(op.end)
-      }
-      return ids
-      */
-      return []
-    },
-    execute: function * (op) {
-      op.start = null
-      op.end = null
-    },
-    ref: function * (op, pos) {
-      if (op.start == null) {
-        return null
-      }
-      var res = null
-      var o = yield* this.getOperation(op.start)
-
-      while (true) {
-        if (!o.deleted) {
-          res = o
-          pos--
-        }
-        if (pos >= 0 && o.right != null) {
-          o = (yield* this.getOperation(o.right))
-        } else {
-          break
-        }
-      }
-      return res
-    },
-    map: function * (o, f) {
-      o = o.start
-      var res = []
-      while (o != null) { // TODO: change to != (at least some convention)
-        var operation = yield* this.getOperation(o)
-        if (!operation.deleted) {
-          res.push(f(operation))
-        }
-        o = operation.right
-      }
-      return res
-    }
-  },
-  Map: {
-    /*
-      {
-        map: {},
-        struct: "Map",
-        type: "",
-        id: this.os.getNextOpId()
-      }
-    */
-    encode: function (op) {
-      return {
-        struct: 'Map',
-        type: op.type,
-        id: op.id,
-        map: {} // overwrite map!!
-      }
-    },
-    requiredOps: function () {
-      return []
-    },
-    execute: function * () {},
-    /*
-      Get a property by name
-    */
-    get: function * (op, name) {
-      var oid = op.map[name]
-      if (oid != null) {
-        var res = yield* this.getOperation(oid)
-        return (res == null || res.deleted) ? void 0 : (res.opContent == null
-          ? res.content : yield* this.getType(res.opContent))
-      }
-    },
-    /*
-      Delete a property by name
-    */
-    delete: function * (op, name) {
-      var v = op.map[name] || null
-      if (v != null) {
-        yield* Struct.Delete.create.call(this, {
-          target: v
-        })
-      }
-    }
-  }
-}
-Y.Struct = Struct
--- a/src/Transaction.js
+++ b/src/Transaction.js
@@ -1,653 +0,0 @@
-/* global Y */
-'use strict'
-
-/*
-  Partial definition of a transaction
-
-  A transaction provides all the the async functionality on a database.
-
-  By convention, a transaction has the following properties:
-  * ss for StateSet
-  * os for OperationStore
-  * ds for DeleteStore
-
-  A transaction must also define the following methods:
-  * checkDeleteStoreForState(state)
-    - When increasing the state of a user, an operation with an higher id
-      may already be garbage collected, and therefore it will never be received.
-      update the state to reflect this knowledge. This won't call a method to save the state!
-  * getDeleteSet(id)
-    - Get the delete set in a readable format:
-      {
-        "userX": [
-          [5,1], // starting from position 5, one operations is deleted
-          [9,4]  // starting from position 9, four operations are deleted
-        ],
-        "userY": ...
-      }
-  * getOpsFromDeleteSet(ds) -- TODO: just call this.deleteOperation(id) here
-    - get a set of deletions that need to be applied in order to get to
-      achieve the state of the supplied ds
-  * setOperation(op)
-    - write `op` to the database.
-      Note: this is allowed to return an in-memory object.
-      E.g. the Memory adapter returns the object that it has in-memory.
-      Changing values on this object will be stored directly in the database
-      without calling this function. Therefore,
-      setOperation may have no functionality in some adapters. This also has
-      implications on the way we use operations that were served from the database.
-      We try not to call copyObject, if not necessary.
-  * addOperation(op)
-    - add an operation to the database.
-      This may only be called once for every op.id
-      Must return a function that returns the next operation in the database (ordered by id)
-  * getOperation(id)
-  * removeOperation(id)
-    - remove an operation from the database. This is called when an operation
-      is garbage collected.
-  * setState(state)
-    - `state` is of the form
-      {
-        user: "1",
-        clock: 4
-      } <- meaning that we have four operations from user "1"
-           (with these id's respectively: 0, 1, 2, and 3)
-  * getState(user)
-  * getStateVector()
-    - Get the state of the OS in the form
-    [{
-      user: "userX",
-      clock: 11
-    },
-     ..
-    ]
-  * getStateSet()
-    - Get the state of the OS in the form
-    {
-      "userX": 11,
-      "userY": 22
-    }
-   * getOperations(startSS)
-     - Get the all the operations that are necessary in order to achive the
-       stateSet of this user, starting from a stateSet supplied by another user
-   * makeOperationReady(ss, op)
-     - this is called only by `getOperations(startSS)`. It makes an operation
-       applyable on a given SS.
-*/
-class Transaction {
-  /*
-    Get a type based on the id of its model.
-    If it does not exist yes, create it.
-    TODO: delete type from store.initializedTypes[id] when corresponding id was deleted!
-  */
-  * getType (id) {
-    var sid = JSON.stringify(id)
-    var t = this.store.initializedTypes[sid]
-    if (t == null) {
-      var op = yield* this.getOperation(id)
-      if (op != null) {
-        t = yield* Y[op.type].initType.call(this, this.store, op)
-        this.store.initializedTypes[sid] = t
-      }
-    }
-    return t
-  }
-  /*
-    Apply operations that this user created (no remote ones!)
-      * does not check for Struct.*.requiredOps()
-      * also broadcasts it through the connector
-  */
-  * applyCreatedOperations (ops) {
-    var send = []
-    for (var i = 0; i < ops.length; i++) {
-      var op = ops[i]
-      yield* this.store.tryExecute.call(this, op)
-      send.push(Y.Struct[op.struct].encode(op))
-    }
-    if (!this.store.y.connector.isDisconnected()) {
-      this.store.y.connector.broadcast({
-        type: 'update',
-        ops: send
-      })
-    }
-  }
-
-  * deleteList (start) {
-    if (this.store.y.connector.isSynced) {
-      while (start != null && this.store.y.connector.isSynced) {
-        start = (yield* this.getOperation(start))
-        start.gc = true
-        yield* this.setOperation(start)
-        // TODO: will always reset the parent..
-        this.store.gc1.push(start.id)
-        start = start.right
-      }
-    } else {
-      // TODO: when not possible??? do later in (gcWhenSynced)
-    }
-  }
-
-  /*
-    Mark an operation as deleted, and add it to the GC, if possible.
-  */
-  * deleteOperation (targetId, preventCallType) {
-    var target = yield* this.getOperation(targetId)
-    var callType = false
-
-    if (target == null || !target.deleted) {
-      yield* this.markDeleted(targetId)
-    }
-
-    if (target != null && target.gc == null) {
-      if (!target.deleted) {
-        callType = true
-        // set deleted & notify type
-        target.deleted = true
-        /*
-        if (!preventCallType) {
-          var type = this.store.initializedTypes[JSON.stringify(target.parent)]
-          if (type != null) {
-            yield* type._changed(this, {
-              struct: 'Delete',
-              target: targetId
-            })
-          }
-        }
-        */
-        // delete containing lists
-        if (target.start != null) {
-          // TODO: don't do it like this .. -.-
-          yield* this.deleteList(target.start)
-          yield* this.deleteList(target.id)
-        }
-        if (target.map != null) {
-          for (var name in target.map) {
-            yield* this.deleteList(target.map[name])
-          }
-          // TODO: here to..  (see above)
-          yield* this.deleteList(target.id)
-        }
-        if (target.opContent != null) {
-          yield* this.deleteOperation(target.opContent)
-          target.opContent = null
-        }
-      }
-      var left = target.left != null ? yield* this.getOperation(target.left) : null
-
-      this.store.addToGarbageCollector(target, left)
-
-      // set here because it was deleted and/or gc'd
-      yield* this.setOperation(target)
-
-      /*
-        Check if it is possible to add right to the gc.
-        Because this delete can't be responsible for left being gc'd,
-        we don't have to add left to the gc..
-      */
-      var right = target.right != null ? yield* this.getOperation(target.right) : null
-      if (
-        right != null &&
-        this.store.addToGarbageCollector(right, target)
-      ) {
-        yield* this.setOperation(right)
-      }
-      return callType
-    }
-  }
-  /*
-    Mark an operation as deleted&gc'd
-  */
-  * markGarbageCollected (id) {
-    // this.mem.push(["gc", id]);
-    var n = yield* this.markDeleted(id)
-    if (!n.gc) {
-      if (n.id[1] < id[1]) {
-        // un-extend left
-        var newlen = n.len - (id[1] - n.id[1])
-        n.len -= newlen
-        yield* this.ds.put(n)
-        n = {id: id, len: newlen, gc: false}
-        yield* this.ds.put(n)
-      }
-      // get prev&next before adding a new operation
-      var prev = yield* this.ds.findPrev(id)
-      var next = yield* this.ds.findNext(id)
-
-      if (id[1] < n.id[1] + n.len - 1) {
-        // un-extend right
-        yield* this.ds.put({id: [id[0], id[1] + 1], len: n.len - 1, gc: false})
-        n.len = 1
-      }
-      // set gc'd
-      n.gc = true
-      // can extend left?
-      if (
-        prev != null &&
-        prev.gc &&
-        Y.utils.compareIds([prev.id[0], prev.id[1] + prev.len], n.id)
-      ) {
-        prev.len += n.len
-        yield* this.ds.delete(n.id)
-        n = prev
-        // ds.put n here?
-      }
-      // can extend right?
-      if (
-        next != null &&
-        next.gc &&
-        Y.utils.compareIds([n.id[0], n.id[1] + n.len], next.id)
-      ) {
-        n.len += next.len
-        yield* this.ds.delete(next.id)
-      }
-      yield* this.ds.put(n)
-    }
-  }
-  /*
-    Mark an operation as deleted.
-
-    returns the delete node
-  */
-  * markDeleted (id) {
-    // this.mem.push(["del", id]);
-    var n = yield* this.ds.findWithUpperBound(id)
-    if (n != null && n.id[0] === id[0]) {
-      if (n.id[1] <= id[1] && id[1] < n.id[1] + n.len) {
-        // already deleted
-        return n
-      } else if (n.id[1] + n.len === id[1] && !n.gc) {
-        // can extend existing deletion
-        n.len++
-      } else {
-        // cannot extend left
-        n = {id: id, len: 1, gc: false}
-        yield* this.ds.put(n)
-      }
-    } else {
-      // cannot extend left
-      n = {id: id, len: 1, gc: false}
-      yield* this.ds.put(n)
-    }
-    // can extend right?
-    var next = yield* this.ds.findNext(n.id)
-    if (
-      next != null &&
-      Y.utils.compareIds([n.id[0], n.id[1] + n.len], next.id) &&
-      !next.gc
-    ) {
-      n.len = n.len + next.len
-      yield* this.ds.delete(next.id)
-    }
-    yield* this.ds.put(n)
-    return n
-  }
-  /*
-    Call this method when the client is connected&synced with the
-    other clients (e.g. master). This will query the database for
-    operations that can be gc'd and add them to the garbage collector.
-  */
-  * garbageCollectAfterSync () {
-    yield* this.os.iterate(this, null, null, function * (op) {
-      if (op.deleted && op.left != null) {
-        var left = yield* this.getOperation(op.left)
-        this.store.addToGarbageCollector(op, left)
-      }
-    })
-  }
-  /*
-    Really remove an op and all its effects.
-    The complicated case here is the Insert operation:
-    * reset left
-    * reset right
-    * reset parent.start
-    * reset parent.end
-    * reset origins of all right ops
-  */
-  * garbageCollectOperation (id) {
-    this.store.addToDebug('yield* this.garbageCollectOperation(', id, ')')
-    // check to increase the state of the respective user
-    var state = yield* this.getState(id[0])
-    if (state.clock === id[1]) {
-      state.clock++
-      // also check if more expected operations were gc'd
-      yield* this.checkDeleteStoreForState(state)
-      // then set the state
-      yield* this.setState(state)
-    }
-    yield* this.markGarbageCollected(id)
-
-    // if op exists, then clean that mess up..
-    var o = yield* this.getOperation(id)
-    if (o != null) {
-      /*
-      if (!o.deleted) {
-        yield* this.deleteOperation(id)
-        o = yield* this.getOperation(id)
-      }
-      */
-
-      // remove gc'd op from the left op, if it exists
-      if (o.left != null) {
-        var left = yield* this.getOperation(o.left)
-        left.right = o.right
-        yield* this.setOperation(left)
-      }
-      // remove gc'd op from the right op, if it exists
-      // also reset origins of right ops
-      if (o.right != null) {
-        var right = yield* this.getOperation(o.right)
-        right.left = o.left
-        if (Y.utils.compareIds(right.origin, o.id)) { // rights origin is o
-          // find new origin of right ops
-          // origin is the first left deleted operation
-          var neworigin = o.left
-          while (neworigin != null) {
-            var neworigin_ = yield* this.getOperation(neworigin)
-            if (neworigin_.deleted) {
-              break
-            }
-            neworigin = neworigin_.left
-          }
-
-          // reset origin of right
-          right.origin = neworigin
-
-          // reset origin of all right ops (except first right - duh!),
-          // until you find origin pointer to the left of o
-          var i = right.right == null ? null : yield* this.getOperation(right.right)
-          var ids = [o.id, o.right]
-          while (i != null && ids.some(function (id) {
-            return Y.utils.compareIds(id, i.origin)
-          })) {
-            if (Y.utils.compareIds(i.origin, o.id)) {
-              // reset origin of i
-              i.origin = neworigin
-              yield* this.setOperation(i)
-            }
-            // get next i
-            i = i.right == null ? null : yield* this.getOperation(i.right)
-          }
-        } /* otherwise, rights origin is to the left of o,
-             then there is no right op (from o), that origins in o */
-        yield* this.setOperation(right)
-      }
-
-      if (o.parent != null) {
-        // remove gc'd op from parent, if it exists
-        var parent = yield* this.getOperation(o.parent)
-        var setParent = false // whether to save parent to the os
-        if (o.parentSub != null) {
-          if (Y.utils.compareIds(parent.map[o.parentSub], o.id)) {
-            setParent = true
-            parent.map[o.parentSub] = o.right
-          }
-        } else {
-          if (Y.utils.compareIds(parent.start, o.id)) {
-            // gc'd op is the start
-            setParent = true
-            parent.start = o.right
-          }
-          if (Y.utils.compareIds(parent.end, o.id)) {
-            // gc'd op is the end
-            setParent = true
-            parent.end = o.left
-          }
-        }
-        if (setParent) {
-          yield* this.setOperation(parent)
-        }
-      }
-      // finally remove it from the os
-      yield* this.removeOperation(o.id)
-    }
-  }
-  * checkDeleteStoreForState (state) {
-    var n = yield* this.ds.findWithUpperBound([state.user, state.clock])
-    if (n != null && n.id[0] === state.user && n.gc) {
-      state.clock = Math.max(state.clock, n.id[1] + n.len)
-    }
-  }
-  /*
-    apply a delete set in order to get
-    the state of the supplied ds
-  */
-  * applyDeleteSet (ds) {
-    var deletions = []
-    function createDeletions (user, start, len, gc) {
-      for (var c = start; c < start + len; c++) {
-        deletions.push([user, c, gc])
-      }
-    }
-
-    for (var user in ds) {
-      var dv = ds[user]
-      var pos = 0
-      var d = dv[pos]
-      yield* this.ds.iterate(this, [user, 0], [user, Number.MAX_VALUE], function * (n) {
-        // cases:
-        // 1. d deletes something to the right of n
-        //  => go to next n (break)
-        // 2. d deletes something to the left of n
-        //  => create deletions
-        //  => reset d accordingly
-        //  *)=> if d doesn't delete anything anymore, go to next d (continue)
-        // 3. not 2) and d deletes something that also n deletes
-        //  => reset d so that it doesn't contain n's deletion
-        //  *)=> if d does not delete anything anymore, go to next d (continue)
-        while (d != null) {
-          var diff = 0 // describe the diff of length in 1) and 2)
-          if (n.id[1] + n.len <= d[0]) {
-            // 1)
-            break
-          } else if (d[0] < n.id[1]) {
-            // 2)
-            // delete maximum the len of d
-            // else delete as much as possible
-            diff = Math.min(n.id[1] - d[0], d[1])
-            createDeletions(user, d[0], diff, d[2])
-          } else {
-            // 3)
-            diff = n.id[1] + n.len - d[0] // never null (see 1)
-            if (d[2] && !n.gc) {
-              // d marks as gc'd but n does not
-              // then delete either way
-              createDeletions(user, d[0], Math.min(diff, d[1]), d[2])
-            }
-          }
-          if (d[1] <= diff) {
-            // d doesn't delete anything anymore
-            d = dv[++pos]
-          } else {
-            d[0] = d[0] + diff // reset pos
-            d[1] = d[1] - diff // reset length
-          }
-        }
-      })
-      // for the rest.. just apply it
-      for (; pos < dv.length; pos++) {
-        d = dv[pos]
-        createDeletions(user, d[0], d[1], d[2])
-      }
-    }
-    for (var i in deletions) {
-      var del = deletions[i]
-      var id = [del[0], del[1]]
-      // always try to delete..
-      var addOperation = yield* this.deleteOperation(id)
-      if (addOperation) {
-        // TODO:.. really .. here? You could prevent calling all these functions in operationAdded
-        yield* this.store.operationAdded(this, {struct: 'Delete', target: id})
-      }
-      if (del[2]) {
-        // gc
-        yield* this.garbageCollectOperation(id)
-      }
-    }
-  }
-  * isGarbageCollected (id) {
-    var n = yield* this.ds.findWithUpperBound(id)
-    return n != null && n.id[0] === id[0] && id[1] < n.id[1] + n.len && n.gc
-  }
-  /*
-    A DeleteSet (ds) describes all the deleted ops in the OS
-  */
-  * getDeleteSet () {
-    var ds = {}
-    yield* this.ds.iterate(this, null, null, function * (n) {
-      var user = n.id[0]
-      var counter = n.id[1]
-      var len = n.len
-      var gc = n.gc
-      var dv = ds[user]
-      if (dv === void 0) {
-        dv = []
-        ds[user] = dv
-      }
-      dv.push([counter, len, gc])
-    })
-    return ds
-  }
-  * isDeleted (id) {
-    var n = yield* this.ds.findWithUpperBound(id)
-    return n != null && n.id[0] === id[0] && id[1] < n.id[1] + n.len
-  }
-  * setOperation (op) {
-    yield* this.os.put(op)
-    return op
-  }
-  * addOperation (op) {
-    yield* this.os.put(op)
-  }
-  * getOperation (id) {
-    return yield* this.os.find(id)
-  }
-  * removeOperation (id) {
-    yield* this.os.delete(id)
-  }
-  * setState (state) {
-    var val = {
-      id: [state.user],
-      clock: state.clock
-    }
-    // TODO: find a way to skip this step.. (after implementing some dbs..)
-    if (yield* this.ss.find([state.user])) {
-      yield* this.ss.put(val)
-    } else {
-      yield* this.ss.put(val)
-    }
-  }
-  * getState (user) {
-    var n
-    var clock = (n = yield* this.ss.find([user])) == null ? null : n.clock
-    if (clock == null) {
-      clock = 0
-    }
-    return {
-      user: user,
-      clock: clock
-    }
-  }
-  * getStateVector () {
-    var stateVector = []
-    yield* this.ss.iterate(this, null, null, function * (n) {
-      stateVector.push({
-        user: n.id[0],
-        clock: n.clock
-      })
-    })
-    return stateVector
-  }
-  * getStateSet () {
-    var ss = {}
-    yield* this.ss.iterate(this, null, null, function * (n) {
-      ss[n.id[0]] = n.clock
-    })
-    return ss
-  }
-  * getOperations (startSS) {
-    // TODO: use bounds here!
-    if (startSS == null) {
-      startSS = {}
-    }
-    var ops = []
-
-    var endSV = yield* this.getStateVector()
-    for (var endState of endSV) {
-      var user = endState.user
-      if (user === '_') {
-        continue
-      }
-      var startPos = startSS[user] || 0
-
-      yield* this.os.iterate(this, [user, startPos], [user, Number.MAX_VALUE], function * (op) {
-        ops.push(op)
-      })
-    }
-    var res = []
-    for (var op of ops) {
-      res.push(yield* this.makeOperationReady(startSS, op))
-    }
-    return res
-  }
-  /*
-    Here, we make op executable for the receiving user.
-
-    Notes:
-      startSS: denotes to the SV that the remote user sent
-      currSS:  denotes to the state vector that the user should have if he
-               applies all already sent operations (increases is each step)
-
-    We face several problems:
-    * Execute op as is won't work because ops depend on each other
-     -> find a way so that they do not anymore
-    * When changing left, must not go more to the left than the origin
-    * When changing right, you have to consider that other ops may have op
-      as their origin, this means that you must not set one of these ops
-      as the new right (interdependencies of ops)
-    * can't just go to the right until you find the first known operation,
-      With currSS
-        -> interdependency of ops is a problem
-      With startSS
-        -> leads to inconsistencies when two users join at the same time.
-           Then the position depends on the order of execution -> error!
-
-      Solution:
-      -> re-create originial situation
-        -> set op.left = op.origin (which never changes)
-        -> set op.right
-             to the first operation that is known (according to startSS)
-             or to the first operation that has an origin that is not to the
-             right of op.
-        -> Enforces unique execution order -> happy user
-
-      Improvements: TODO
-        * Could set left to origin, or the first known operation
-          (startSS or currSS.. ?)
-          -> Could be necessary when I turn GC again.
-          -> Is a bad(ish) idea because it requires more computation
-  */
-  * makeOperationReady (startSS, op) {
-    op = Y.Struct[op.struct].encode(op)
-    op = Y.utils.copyObject(op)
-    var o = op
-    var ids = [op.id]
-    // search for the new op.right
-    // it is either the first known op (according to startSS)
-    // or the o that has no origin to the right of op
-    // (this is why we use the ids array)
-    while (o.right != null) {
-      var right = yield* this.getOperation(o.right)
-      if (o.right[1] < (startSS[o.right[0]] || 0) || !ids.some(function (id) {
-        return Y.utils.compareIds(id, right.origin)
-      })) {
-        break
-      }
-      ids.push(o.right)
-      o = right
-    }
-    op.right = o.right
-    op.left = op.origin
-    return op
-  }
-}
-Y.Transaction = Transaction
--- a/src/Types/Array.js
+++ b/src/Types/Array.js
@@ -1,192 +0,0 @@
-/* global Y */
-'use strict'
-
-;(function () {
-  class YArray {
-    constructor (os, _model, idArray, valArray) {
-      this.os = os
-      this._model = _model
-      // Array of all the operation id's
-      this.idArray = idArray
-      // Array of all the values
-      this.valArray = valArray
-      this.eventHandler = new Y.utils.EventHandler(ops => {
-        var userEvents = []
-        for (var i in ops) {
-          var op = ops[i]
-          if (op.struct === 'Insert') {
-            let pos
-            // we check op.left only!,
-            // because op.right might not be defined when this is called
-            if (op.left === null) {
-              pos = 0
-            } else {
-              var sid = JSON.stringify(op.left)
-              pos = this.idArray.indexOf(sid) + 1
-              if (pos <= 0) {
-                throw new Error('Unexpected operation!')
-              }
-            }
-            this.idArray.splice(pos, 0, JSON.stringify(op.id))
-            this.valArray.splice(pos, 0, op.content)
-            userEvents.push({
-              type: 'insert',
-              object: this,
-              index: pos,
-              length: 1
-            })
-          } else if (op.struct === 'Delete') {
-            let pos = this.idArray.indexOf(JSON.stringify(op.target))
-            if (pos >= 0) {
-              this.idArray.splice(pos, 1)
-              this.valArray.splice(pos, 1)
-              userEvents.push({
-                type: 'delete',
-                object: this,
-                index: pos,
-                length: 1
-              })
-            }
-          } else {
-            throw new Error('Unexpected struct!')
-          }
-        }
-        this.eventHandler.callEventListeners(userEvents)
-      })
-    }
-    get length () {
-      return this.idArray.length
-    }
-    get (pos) {
-      if (pos == null || typeof pos !== 'number') {
-        throw new Error('pos must be a number!')
-      }
-      return this.valArray[pos]
-    }
-    toArray () {
-      return this.valArray.slice()
-    }
-    insert (pos, contents) {
-      if (typeof pos !== 'number') {
-        throw new Error('pos must be a number!')
-      }
-      if (!(contents instanceof Array)) {
-        throw new Error('contents must be an Array of objects!')
-      }
-      if (contents.length === 0) {
-        return
-      }
-      if (pos > this.idArray.length || pos < 0) {
-        throw new Error('This position exceeds the range of the array!')
-      }
-      var mostLeft = pos === 0 ? null : JSON.parse(this.idArray[pos - 1])
-
-      var ops = []
-      var prevId = mostLeft
-      for (var i = 0; i < contents.length; i++) {
-        var op = {
-          left: prevId,
-          origin: prevId,
-          // right: mostRight,
-          // NOTE: I intentionally do not define right here, because it could be deleted
-          // at the time of creating this operation, and is therefore not defined in idArray
-          parent: this._model,
-          content: contents[i],
-          struct: 'Insert',
-          id: this.os.getNextOpId()
-        }
-        ops.push(op)
-        prevId = op.id
-      }
-      var eventHandler = this.eventHandler
-      eventHandler.awaitAndPrematurelyCall(ops)
-      this.os.requestTransaction(function *() {
-        // now we can set the right reference.
-        var mostRight
-        if (mostLeft != null) {
-          mostRight = (yield* this.getOperation(mostLeft)).right
-        } else {
-          mostRight = (yield* this.getOperation(ops[0].parent)).start
-        }
-        for (var j in ops) {
-          ops[j].right = mostRight
-        }
-        yield* this.applyCreatedOperations(ops)
-        eventHandler.awaitedInserts(ops.length)
-      })
-    }
-    delete (pos, length) {
-      if (length == null) { length = 1 }
-      if (typeof length !== 'number') {
-        throw new Error('pos must be a number!')
-      }
-      if (typeof pos !== 'number') {
-        throw new Error('pos must be a number!')
-      }
-      if (pos + length > this.idArray.length || pos < 0 || length < 0) {
-        throw new Error('The deletion range exceeds the range of the array!')
-      }
-      if (length === 0) {
-        return
-      }
-      var eventHandler = this.eventHandler
-      var newLeft = pos > 0 ? JSON.parse(this.idArray[pos - 1]) : null
-      var dels = []
-      for (var i = 0; i < length; i++) {
-        dels.push({
-          target: JSON.parse(this.idArray[pos + i]),
-          struct: 'Delete'
-        })
-      }
-      eventHandler.awaitAndPrematurelyCall(dels)
-      this.os.requestTransaction(function *() {
-        yield* this.applyCreatedOperations(dels)
-        eventHandler.awaitedDeletes(dels.length, newLeft)
-      })
-    }
-    observe (f) {
-      this.eventHandler.addEventListener(f)
-    }
-    * _changed (transaction, op) {
-      if (!op.deleted) {
-        if (op.struct === 'Insert') {
-          var l = op.left
-          var left
-          while (l != null) {
-            left = yield* transaction.getOperation(l)
-            if (!left.deleted) {
-              break
-            }
-            l = left.left
-          }
-          op.left = l
-        }
-        this.eventHandler.receivedOp(op)
-      }
-    }
-  }
-
-  Y.Array = new Y.utils.CustomType({
-    class: YArray,
-    createType: function * YArrayCreator () {
-      var modelid = this.store.getNextOpId()
-      var model = {
-        struct: 'List',
-        type: 'Array',
-        start: null,
-        end: null,
-        id: modelid
-      }
-      yield* this.applyCreatedOperations([model])
-      return modelid
-    },
-    initType: function * YArrayInitializer (os, model) {
-      var valArray = []
-      var idArray = yield* Y.Struct.List.map.call(this, model, function (c) {
-        valArray.push(c.content)
-        return JSON.stringify(c.id)
-      })
-      return new YArray(os, model.id, idArray, valArray)
-    }
-  })
-})()
--- a/src/Types/Array.spec.js
+++ b/src/Types/Array.spec.js
@@ -1,310 +0,0 @@
-/* global createUsers, databases, wait, Y, compareAllUsers, getRandomNumber, applyRandomTransactionsAllRejoinNoGC, applyRandomTransactionsWithGC, async, garbageCollectAllUsers, describeManyTimes */
-/* eslint-env browser,jasmine */
-
-var numberOfYArrayTests = 50
-var repeatArrayTests = 2
-
-for (let database of databases) {
-  describe(`Array Type (DB: ${database})`, function () {
-    var y1, y2, y3, yconfig1, yconfig2, yconfig3, flushAll
-
-    beforeEach(async(function * (done) {
-      yield createUsers(this, 3, database)
-      y1 = (yconfig1 = this.users[0]).root
-      y2 = (yconfig2 = this.users[1]).root
-      y3 = (yconfig3 = this.users[2]).root
-      flushAll = this.users[0].connector.flushAll
-      yield wait(10)
-      done()
-    }))
-    afterEach(async(function * (done) {
-      yield compareAllUsers(this.users)
-      done()
-    }))
-
-    describe('Basic tests', function () {
-      it('insert three elements, try re-get property', async(function * (done) {
-        var array = yield y1.set('Array', Y.Array)
-        array.insert(0, [1, 2, 3])
-        array = yield y1.get('Array') // re-get property
-        expect(array.toArray()).toEqual([1, 2, 3])
-        done()
-      }))
-      it('Basic insert in array (handle three conflicts)', async(function * (done) {
-        yield y1.set('Array', Y.Array)
-        yield flushAll()
-        var l1 = yield y1.get('Array')
-        l1.insert(0, [0])
-        var l2 = yield y2.get('Array')
-        l2.insert(0, [1])
-        var l3 = yield y3.get('Array')
-        l3.insert(0, [2])
-        yield flushAll()
-        expect(l1.toArray()).toEqual(l2.toArray())
-        expect(l2.toArray()).toEqual(l3.toArray())
-        done()
-      }))
-      it('Basic insert&delete in array (handle three conflicts)', async(function * (done) {
-        var l1, l2, l3
-        l1 = yield y1.set('Array', Y.Array)
-        l1.insert(0, ['x', 'y', 'z'])
-        yield flushAll()
-        l1.insert(1, [0])
-        l2 = yield y2.get('Array')
-        l2.delete(0)
-        l2.delete(1)
-        l3 = yield y3.get('Array')
-        l3.insert(1, [2])
-        yield flushAll()
-        expect(l1.toArray()).toEqual(l2.toArray())
-        expect(l2.toArray()).toEqual(l3.toArray())
-        expect(l2.toArray()).toEqual([0, 2, 'y'])
-        done()
-      }))
-      it('Handles getOperations ascending ids bug in late sync', async(function * (done) {
-        var l1, l2
-        l1 = yield y1.set('Array', Y.Array)
-        l1.insert(0, ['x', 'y'])
-        yield flushAll()
-        yconfig3.disconnect()
-        yconfig2.disconnect()
-        yield wait()
-        l2 = yield y2.get('Array')
-        l2.insert(1, [2])
-        l2.insert(1, [3])
-        yield yconfig2.reconnect()
-        yield yconfig3.reconnect()
-        expect(l1.toArray()).toEqual(l2.toArray())
-        done()
-      }))
-      it('Handles deletions in late sync', async(function * (done) {
-        var l1, l2
-        l1 = yield y1.set('Array', Y.Array)
-        l1.insert(0, ['x', 'y'])
-        yield flushAll()
-        yield yconfig2.disconnect()
-        yield wait()
-        l2 = yield y2.get('Array')
-        l2.delete(1, 1)
-        l1.delete(0, 2)
-        yield yconfig2.reconnect()
-        expect(l1.toArray()).toEqual(l2.toArray())
-        done()
-      }))
-      it('Handles deletions in late sync (2)', async(function * (done) {
-        var l1, l2
-        l1 = yield y1.set('Array', Y.Array)
-        yield flushAll()
-        l2 = yield y2.get('Array')
-        l1.insert(0, ['x', 'y'])
-        l1.delete(0, 2)
-        yield flushAll()
-        expect(l1.toArray()).toEqual(l2.toArray())
-        done()
-      }))
-      it('Basic insert. Then delete the whole array', async(function * (done) {
-        var l1, l2, l3
-        l1 = yield y1.set('Array', Y.Array)
-        l1.insert(0, ['x', 'y', 'z'])
-        yield flushAll()
-        l1.delete(0, 3)
-        l2 = yield y2.get('Array')
-        l3 = yield y3.get('Array')
-        yield flushAll()
-        expect(l1.toArray()).toEqual(l2.toArray())
-        expect(l2.toArray()).toEqual(l3.toArray())
-        expect(l2.toArray()).toEqual([])
-        done()
-      }))
-      it('Basic insert. Then delete the whole array (merge listeners on late sync)', async(function * (done) {
-        var l1, l2, l3
-        l1 = yield y1.set('Array', Y.Array)
-        l1.insert(0, ['x', 'y', 'z'])
-        yield flushAll()
-        yconfig2.disconnect()
-        l1.delete(0, 3)
-        l2 = yield y2.get('Array')
-        yield wait()
-        yield yconfig2.reconnect()
-        yield wait()
-        l3 = yield y3.get('Array')
-        yield flushAll()
-        expect(l1.toArray()).toEqual(l2.toArray())
-        expect(l2.toArray()).toEqual(l3.toArray())
-        expect(l2.toArray()).toEqual([])
-        done()
-      }))
-      // TODO?
-      /* it('Basic insert. Then delete the whole array (merge deleter on late sync)', async(function * (done) {
-        var l1, l2, l3
-        l1 = yield y1.set('Array', Y.Array)
-        l1.insert(0, ['x', 'y', 'z'])
-        yield flushAll()
-        yconfig1.disconnect()
-        l1.delete(0, 3)
-        l2 = yield y2.get('Array')
-        yield yconfig1.reconnect()
-        l3 = yield y3.get('Array')
-        yield flushAll()
-        expect(l1.toArray()).toEqual(l2.toArray())
-        expect(l2.toArray()).toEqual(l3.toArray())
-        expect(l2.toArray()).toEqual([])
-        done()
-      })) */
-      it('throw insert & delete events', async(function * (done) {
-        var array = yield this.users[0].root.set('array', Y.Array)
-        var event
-        array.observe(function (e) {
-          event = e
-        })
-        array.insert(0, [0])
-        expect(event).toEqual([{
-          type: 'insert',
-          object: array,
-          index: 0,
-          length: 1
-        }])
-        array.delete(0)
-        expect(event).toEqual([{
-          type: 'delete',
-          object: array,
-          index: 0,
-          length: 1
-        }])
-        yield wait(50)
-        done()
-      }))
-      it('garbage collects', async(function * (done) {
-        var l1, l2, l3
-        l1 = yield y1.set('Array', Y.Array)
-        l1.insert(0, ['x', 'y', 'z'])
-        yield flushAll()
-        yconfig1.disconnect()
-        l1.delete(0, 3)
-        l2 = yield y2.get('Array')
-        yield wait()
-        yield yconfig1.reconnect()
-        yield wait()
-        l3 = yield y3.get('Array')
-        yield flushAll()
-        yield garbageCollectAllUsers(this.users)
-        expect(l1.toArray()).toEqual(l2.toArray())
-        expect(l2.toArray()).toEqual(l3.toArray())
-        expect(l2.toArray()).toEqual([])
-        done()
-      }))
-      it('debug right not existend in Insert.execute', async(function * (done) {
-        yconfig1.db.requestTransaction(function * () {
-          var ops = [{'struct':'Map','type':'Map','id':['130',0],'map':{}},{'id':['130',1],'left':null,'right':null,'origin':null,'parent':['_',0],'struct':'Insert','parentSub':'Map','opContent':['130',0]},{'struct':'Map','type':'Map','id':['130',0],'map':{}},{'id':['130',1],'left':null,'right':null,'origin':null,'parent':['_',0],'struct':'Insert','parentSub':'Map','opContent':['130',0]},{'struct':'Map','type':'Map','id':['130',0],'map':{}},{'id':['130',1],'left':null,'right':null,'origin':null,'parent':['_',0],'struct':'Insert','parentSub':'Map','opContent':['130',0]},{'left':null,'right':null,'origin':null,'parent':['130',0],'parentSub':'somekey','struct':'Insert','content':512,'id':['133',0]},{'id':['130',2],'left':null,'right':null,'origin':null,'parent':['130',0],'struct':'Insert','parentSub':'somekey','content':1131},{'id':['130',3],'left':null,'right':['130',2],'origin':null,'parent':['130',0],'struct':'Insert','parentSub':'somekey','content':4196},{'id':['131',3],'left':null,'right':null,'origin':null,'parent':['130',0],'struct':'Insert','parentSub':'somekey','content':5022}]//eslint-disable-line
-
-          for (var o of ops) {
-            yield* this.store.tryExecute.call(this, o)
-          }
-        })
-        yield wait()
-        yield yconfig3.disconnect()
-        yield yconfig2.disconnect()
-        yield flushAll()
-        wait()
-        yield yconfig3.reconnect()
-        yield yconfig2.reconnect()
-        yield wait()
-        yield flushAll()
-        done()
-      }))
-      it('debug right not existend in Insert.execute (2)', async(function * (done) {
-        yconfig1.db.requestTransaction(function * () {
-          yield* this.store.tryExecute.call(this, {'struct': 'Map', 'type': 'Map', 'id': ['153', 0], 'map': {}})
-          yield* this.store.tryExecute.call(this, {'id': ['153', 1], 'left': null, 'right': null, 'origin': null, 'parent': ['_', 0], 'struct': 'Insert', 'parentSub': 'Map', 'opContent': ['153', 0]})
-          yield* this.store.tryExecute.call(this, {'struct': 'Map', 'type': 'Map', 'id': ['153', 0], 'map': {}})
-          yield* this.store.tryExecute.call(this, {'id': ['153', 1], 'left': null, 'right': null, 'origin': null, 'parent': ['_', 0], 'struct': 'Insert', 'parentSub': 'Map', 'opContent': ['153', 0]})
-          yield* this.store.tryExecute.call(this, {'struct': 'Map', 'type': 'Map', 'id': ['153', 0], 'map': {}})
-          yield* this.store.tryExecute.call(this, {'id': ['153', 1], 'left': null, 'right': null, 'origin': null, 'parent': ['_', 0], 'struct': 'Insert', 'parentSub': 'Map', 'opContent': ['153', 0]})
-          yield* this.store.tryExecute.call(this, {'left': null, 'right': null, 'origin': null, 'parent': ['153', 0], 'parentSub': 'somekey', 'struct': 'Insert', 'content': 3784, 'id': ['154', 0]})
-          yield* this.store.tryExecute.call(this, {'left': null, 'right': ['154', 0], 'origin': null, 'parent': ['153', 0], 'parentSub': 'somekey', 'struct': 'Insert', 'content': 8217, 'id': ['154', 1]})
-          yield* this.store.tryExecute.call(this, {'left': null, 'right': ['154', 1], 'origin': null, 'parent': ['153', 0], 'parentSub': 'somekey', 'struct': 'Insert', 'content': 5036, 'id': ['154', 2]})
-          yield* this.store.tryExecute.call(this, {'id': ['153', 2], 'left': null, 'right': null, 'origin': null, 'parent': ['153', 0], 'struct': 'Insert', 'parentSub': 'somekey', 'content': 417})
-          yield* this.store.tryExecute.call(this, {'id': ['155', 0], 'left': null, 'right': null, 'origin': null, 'parent': ['153', 0], 'struct': 'Insert', 'parentSub': 'somekey', 'content': 2202})
-          yield* this.garbageCollectOperation(['153', 2])
-          yield* this.garbageCollectOperation(['154', 0])
-          yield* this.garbageCollectOperation(['154', 1])
-          yield* this.garbageCollectOperation(['154', 2])
-          yield* this.garbageCollectOperation(['155', 0])
-          yield* this.garbageCollectOperation(['156', 0])
-          yield* this.garbageCollectOperation(['157', 0])
-          yield* this.garbageCollectOperation(['157', 1])
-          yield* this.store.tryExecute.call(this, {'id': ['153', 3], 'left': null, 'right': null, 'origin': null, 'parent': ['153', 0], 'struct': 'Insert', 'parentSub': 'somekey', 'content': 4372})
-        })
-        yield wait()
-        yield yconfig3.disconnect()
-        yield yconfig2.disconnect()
-        yield flushAll()
-        wait()
-        yield yconfig3.reconnect()
-        yield yconfig2.reconnect()
-        yield wait()
-        yield flushAll()
-        done()
-      }))
-    })
-    describeManyTimes(repeatArrayTests, `Random tests`, function () {
-      var randomArrayTransactions = [
-        function insert (array) {
-          array.insert(getRandomNumber(array.toArray().length), [getRandomNumber()])
-        },
-        function _delete (array) {
-          var length = array.toArray().length
-          if (length > 0) {
-            array.delete(getRandomNumber(length - 1))
-          }
-        }
-      ]
-      function compareArrayValues (arrays) {
-        var firstArray
-        for (var l of arrays) {
-          var val = l.toArray()
-          if (firstArray == null) {
-            firstArray = val
-          } else {
-            expect(val).toEqual(firstArray)
-          }
-        }
-      }
-      beforeEach(async(function * (done) {
-        yield this.users[0].root.set('Array', Y.Array)
-        yield flushAll()
-
-        var promises = []
-        for (var u = 0; u < this.users.length; u++) {
-          promises.push(this.users[u].root.get('Array'))
-        }
-        this.arrays = yield Promise.all(promises)
-        done()
-      }))
-      it('arrays.length equals users.length', async(function * (done) {
-        expect(this.arrays.length).toEqual(this.users.length)
-        done()
-      }))
-      it(`succeed after ${numberOfYArrayTests} actions, no GC, all users disconnecting/reconnecting`, async(function * (done) {
-        for (var u of this.users) {
-          u.connector.debug = true
-        }
-        yield applyRandomTransactionsAllRejoinNoGC(this.users, this.arrays, randomArrayTransactions, numberOfYArrayTests)
-        yield flushAll()
-        yield compareArrayValues(this.arrays)
-        yield compareAllUsers(this.users)
-        done()
-      }))
-      it(`succeed after ${numberOfYArrayTests} actions, GC, user[0] is not disconnecting`, async(function * (done) {
-        for (var u of this.users) {
-          u.connector.debug = true
-        }
-        yield applyRandomTransactionsWithGC(this.users, this.arrays, randomArrayTransactions, numberOfYArrayTests)
-        yield flushAll()
-        yield compareArrayValues(this.arrays)
-        yield compareAllUsers(this.users)
-        done()
-      }))
-    })
-  })
-}
--- a/src/Types/Map.js
+++ b/src/Types/Map.js
@@ -1,295 +0,0 @@
-/* global Y */
-'use strict'
-
-;(function () {
-  class YMap {
-    constructor (os, model, contents, opContents) {
-      this._model = model.id
-      this.os = os
-      this.map = Y.utils.copyObject(model.map)
-      this.contents = contents
-      this.opContents = opContents
-      this.eventHandler = new Y.utils.EventHandler(ops => {
-        var userEvents = []
-        for (var i in ops) {
-          var op = ops[i]
-          var oldValue
-          // key is the name to use to access (op)content
-          var key = op.struct === 'Delete' ? op.key : op.parentSub
-
-          // compute oldValue
-          if (this.opContents[key] != null) {
-            let prevType = this.opContents[key]
-            oldValue = () => {// eslint-disable-line
-              return new Promise((resolve) => {
-                this.os.requestTransaction(function *() {// eslint-disable-line
-                  resolve(yield* this.getType(prevType))
-                })
-              })
-            }
-          } else {
-            oldValue = this.contents[key]
-          }
-          // compute op event
-          if (op.struct === 'Insert') {
-            if (op.left === null) {
-              if (op.opContent != null) {
-                delete this.contents[key]
-                if (op.deleted) {
-                  delete this.opContents[key]
-                } else {
-                  this.opContents[key] = op.opContent
-                }
-              } else {
-                delete this.opContents[key]
-                if (op.deleted) {
-                  delete this.contents[key]
-                } else {
-                  this.contents[key] = op.content
-                }
-              }
-              this.map[key] = op.id
-              var insertEvent = {
-                name: key,
-                object: this
-              }
-              if (oldValue === undefined) {
-                insertEvent.type = 'add'
-              } else {
-                insertEvent.type = 'update'
-                insertEvent.oldValue = oldValue
-              }
-              userEvents.push(insertEvent)
-            }
-          } else if (op.struct === 'Delete') {
-            if (Y.utils.compareIds(this.map[key], op.target)) {
-              delete this.opContents[key]
-              delete this.contents[key]
-              var deleteEvent = {
-                name: key,
-                object: this,
-                oldValue: oldValue,
-                type: 'delete'
-              }
-              userEvents.push(deleteEvent)
-            }
-          } else {
-            throw new Error('Unexpected Operation!')
-          }
-        }
-        this.eventHandler.callEventListeners(userEvents)
-      })
-    }
-    get (key) {
-      // return property.
-      // if property does not exist, return null
-      // if property is a type, return a promise
-      if (key == null) {
-        throw new Error('You must specify key!')
-      }
-      if (this.opContents[key] == null) {
-        return this.contents[key]
-      } else {
-        return new Promise((resolve) => {
-          var oid = this.opContents[key]
-          this.os.requestTransaction(function *() {
-            resolve(yield* this.getType(oid))
-          })
-        })
-      }
-    }
-    /*
-      If there is a primitive (not a custom type), then return it.
-      Returns all primitive values, if propertyName is specified!
-      Note: modifying the return value could result in inconsistencies!
-        -- so make sure to copy it first!
-    */
-    getPrimitive (key) {
-      if (key == null) {
-        return Y.utils.copyObject(this.contents)
-      } else {
-        return this.contents[key]
-      }
-    }
-    delete (key) {
-      var right = this.map[key]
-      if (right != null) {
-        var del = {
-          target: right,
-          struct: 'Delete'
-        }
-        var eventHandler = this.eventHandler
-        var modDel = Y.utils.copyObject(del)
-        modDel.key = key
-        eventHandler.awaitAndPrematurelyCall([modDel])
-        this.os.requestTransaction(function *() {
-          yield* this.applyCreatedOperations([del])
-          eventHandler.awaitedDeletes(1)
-        })
-      }
-    }
-    set (key, value) {
-      // set property.
-      // if property is a type, return a promise
-      // if not, apply immediately on this type an call event
-
-      var right = this.map[key] || null
-      var insert = {
-        left: null,
-        right: right,
-        origin: null,
-        parent: this._model,
-        parentSub: key,
-        struct: 'Insert'
-      }
-      return new Promise((resolve) => {
-        if (value instanceof Y.utils.CustomType) {
-          // construct a new type
-          this.os.requestTransaction(function *() {
-            var typeid = yield* value.createType.call(this)
-            var type = yield* this.getType(typeid)
-            insert.opContent = typeid
-            insert.id = this.store.getNextOpId()
-            yield* this.applyCreatedOperations([insert])
-            resolve(type)
-          })
-        } else {
-          insert.content = value
-          insert.id = this.os.getNextOpId()
-          var eventHandler = this.eventHandler
-          eventHandler.awaitAndPrematurelyCall([insert])
-
-          this.os.requestTransaction(function *() {
-            yield* this.applyCreatedOperations([insert])
-            eventHandler.awaitedInserts(1)
-          })
-          resolve(value)
-        }
-      })
-    }
-    observe (f) {
-      this.eventHandler.addEventListener(f)
-    }
-    unobserve (f) {
-      this.eventHandler.removeEventListener(f)
-    }
-    /*
-      Observe a path.
-
-      E.g.
-      ```
-      o.set('textarea', Y.TextBind)
-      o.observePath(['textarea'], function(t){
-        // is called whenever textarea is replaced
-        t.bind(textarea)
-      })
-
-      returns a Promise that contains a function that removes the observer from the path.
-    */
-    observePath (path, f) {
-      var self = this
-      function observeProperty (events) {
-        // call f whenever path changes
-        for (var i = 0; i < events.length; i++) {
-          var event = events[i]
-          if (event.name === propertyName) {
-            // call this also for delete events!
-            var property = self.get(propertyName)
-            if (property instanceof Promise) {
-              property.then(f)
-            } else {
-              f(property)
-            }
-          }
-        }
-      }
-
-      if (path.length < 1) {
-        throw new Error('Path must contain at least one element!')
-      } else if (path.length === 1) {
-        var propertyName = path[0]
-        var property = self.get(propertyName)
-        if (property instanceof Promise) {
-          property.then(f)
-        } else {
-          f(property)
-        }
-        this.observe(observeProperty)
-        return Promise.resolve(function () {
-          self.unobserve(f)
-        })
-      } else {
-        var deleteChildObservers
-        var resetObserverPath = function () {
-          var promise = self.get(path[0])
-          if (!promise instanceof Promise) {
-            // its either not defined or a primitive value
-            promise = self.set(path[0], Y.Map)
-          }
-          return promise.then(function (map) {
-            return map.observePath(path.slice(1), f)
-          }).then(function (_deleteChildObservers) {
-            // update deleteChildObservers
-            deleteChildObservers = _deleteChildObservers
-            return Promise.resolve() // Promise does not return anything
-          })
-        }
-        var observer = function (events) {
-          for (var e in events) {
-            var event = events[e]
-            if (event.name === path[0]) {
-              deleteChildObservers()
-              if (event.type === 'add' || event.type === 'update') {
-                resetObserverPath()
-              }
-              // TODO: what about the delete events?
-            }
-          }
-        }
-        self.observe(observer)
-        return resetObserverPath().then(
-          // this promise contains a function that deletes all the child observers
-          // and how to unobserve the observe from this object
-          Promise.resolve(function () {
-            deleteChildObservers()
-            self.unobserve(observer)
-          })
-        )
-      }
-    }
-    * _changed (transaction, op) {
-      if (op.struct === 'Delete') {
-        op.key = (yield* transaction.getOperation(op.target)).parentSub
-      }
-      this.eventHandler.receivedOp(op)
-    }
-  }
-  Y.Map = new Y.utils.CustomType({
-    class: YMap,
-    createType: function * YMapCreator () {
-      var modelid = this.store.getNextOpId()
-      var model = {
-        map: {},
-        struct: 'Map',
-        type: 'Map',
-        id: modelid
-      }
-      yield* this.applyCreatedOperations([model])
-      return modelid
-    },
-    initType: function * YMapInitializer (os, model) {
-      var contents = {}
-      var opContents = {}
-      var map = model.map
-      for (var name in map) {
-        var op = yield* this.getOperation(map[name])
-        if (op.opContent != null) {
-          opContents[name] = op.opContent
-        } else {
-          contents[name] = op.content
-        }
-      }
-      return new YMap(os, model, contents, opContents)
-    }
-  })
-})()
--- a/src/Types/Map.spec.js
+++ b/src/Types/Map.spec.js
@@ -1,219 +0,0 @@
-/* global createUsers, Y, databases, compareAllUsers, getRandomNumber, applyRandomTransactionsAllRejoinNoGC, applyRandomTransactionsWithGC, async, describeManyTimes */
-/* eslint-env browser,jasmine */
-
-var numberOfYMapTests = 40
-var repeatMapTeasts = 2
-
-for (let database of databases) {
-  describe(`Map Type (DB: ${database})`, function () {
-    var y1, y2, y3, y4, flushAll
-
-    beforeEach(async(function * (done) {
-      yield createUsers(this, 5, database)
-      y1 = this.users[0].root
-      y2 = this.users[1].root
-      y3 = this.users[2].root
-      y4 = this.users[3].root
-      flushAll = this.users[0].connector.flushAll
-      done()
-    }))
-    afterEach(async(function * (done) {
-      yield compareAllUsers(this.users)
-      done()
-    }), 5000)
-
-    describe('Basic tests', function () {
-      it('Basic get&set of Map property (converge via sync)', async(function * (done) {
-        y1.set('stuff', 'stuffy')
-        expect(y1.get('stuff')).toEqual('stuffy')
-        yield flushAll()
-        for (var key in this.users) {
-          var u = this.users[key].root
-          expect(u.get('stuff')).toEqual('stuffy')
-        }
-        done()
-      }))
-      it('Map can set custom types (Map)', async(function * (done) {
-        var map = yield y1.set('Map', Y.Map)
-        map.set('one', 1)
-        map = yield y1.get('Map')
-        expect(map.get('one')).toEqual(1)
-        done()
-      }))
-      it('Map can set custom types (Array)', async(function * (done) {
-        var array = yield y1.set('Array', Y.Array)
-        array.insert(0, [1, 2, 3])
-        array = yield y1.get('Array')
-        expect(array.toArray()).toEqual([1, 2, 3])
-        done()
-      }))
-      it('Basic get&set of Map property (converge via update)', async(function * (done) {
-        yield flushAll()
-        y1.set('stuff', 'stuffy')
-        expect(y1.get('stuff')).toEqual('stuffy')
-
-        yield flushAll()
-        for (var key in this.users) {
-          var r = this.users[key].root
-          expect(r.get('stuff')).toEqual('stuffy')
-        }
-        done()
-      }))
-      it('Basic get&set of Map property (handle conflict)', async(function * (done) {
-        yield flushAll()
-        y1.set('stuff', 'c0')
-        y2.set('stuff', 'c1')
-
-        yield flushAll()
-        for (var key in this.users) {
-          var u = this.users[key]
-          expect(u.root.get('stuff')).toEqual('c0')
-        }
-        done()
-      }))
-      it('Basic get&set&delete of Map property (handle conflict)', async(function * (done) {
-        yield flushAll()
-        y1.set('stuff', 'c0')
-        y1.delete('stuff')
-        y2.set('stuff', 'c1')
-        yield flushAll()
-
-        for (var key in this.users) {
-          var u = this.users[key]
-          expect(u.root.get('stuff')).toBeUndefined()
-        }
-        done()
-      }))
-      it('Basic get&set of Map property (handle three conflicts)', async(function * (done) {
-        yield flushAll()
-        y1.set('stuff', 'c0')
-        y2.set('stuff', 'c1')
-        y2.set('stuff', 'c2')
-        y3.set('stuff', 'c3')
-        yield flushAll()
-
-        for (var key in this.users) {
-          var u = this.users[key]
-          expect(u.root.get('stuff')).toEqual('c0')
-        }
-        done()
-      }))
-      it('Basic get&set&delete of Map property (handle three conflicts)', async(function * (done) {
-        yield flushAll()
-        y1.set('stuff', 'c0')
-        y2.set('stuff', 'c1')
-        y2.set('stuff', 'c2')
-        y3.set('stuff', 'c3')
-        yield flushAll()
-        y1.set('stuff', 'deleteme')
-        y1.delete('stuff')
-        y2.set('stuff', 'c1')
-        y3.set('stuff', 'c2')
-        y4.set('stuff', 'c3')
-        yield flushAll()
-
-        for (var key in this.users) {
-          var u = this.users[key]
-          expect(u.root.get('stuff')).toBeUndefined()
-        }
-        done()
-      }))
-      it('observePath properties', async(function * (done) {
-        y1.observePath(['map'], function (map) {
-          if (map != null) {
-            map.set('yay', 4)
-          }
-        })
-        yield y2.set('map', Y.Map)
-        yield flushAll()
-        var map = yield y3.get('map')
-        expect(map.get('yay')).toEqual(4)
-        done()
-      }))
-      it('throws add & update & delete events (with type and primitive content)', async(function * (done) {
-        var event
-        yield flushAll()
-        y1.observe(function (e) {
-          event = e // just put it on event, should be thrown synchronously anyway
-        })
-        y1.set('stuff', 4)
-        expect(event).toEqual([{
-          type: 'add',
-          object: y1,
-          name: 'stuff'
-        }])
-        // update, oldValue is in contents
-        yield y1.set('stuff', Y.Array)
-        expect(event).toEqual([{
-          type: 'update',
-          object: y1,
-          name: 'stuff',
-          oldValue: 4
-        }])
-        y1.get('stuff').then(function (replacedArray) {
-          // update, oldValue is in opContents
-          y1.set('stuff', 5)
-          var getYArray = event[0].oldValue
-          expect(typeof getYArray.constructor === 'function').toBeTruthy()
-          getYArray().then(function (array) {
-            expect(array).toEqual(replacedArray)
-
-            // delete
-            y1.delete('stuff')
-            expect(event).toEqual([{
-              type: 'delete',
-              name: 'stuff',
-              object: y1,
-              oldValue: 5
-            }])
-            done()
-          })
-        })
-      }))
-    })
-    describeManyTimes(repeatMapTeasts, `${numberOfYMapTests} Random tests`, function () {
-      var randomMapTransactions = [
-        function set (map) {
-          map.set('somekey', getRandomNumber())
-        },
-        function delete_ (map) {
-          map.delete('somekey')
-        }
-      ]
-      function compareMapValues (maps) {
-        var firstMap
-        for (var map of maps) {
-          var val = map.getPrimitive()
-          if (firstMap == null) {
-            firstMap = val
-          } else {
-            expect(val).toEqual(firstMap)
-          }
-        }
-      }
-      beforeEach(async(function * (done) {
-        yield y1.set('Map', Y.Map)
-        yield flushAll()
-
-        var promises = []
-        for (var u = 0; u < this.users.length; u++) {
-          promises.push(this.users[u].root.get('Map'))
-        }
-        this.maps = yield Promise.all(promises)
-        done()
-      }))
-      it(`succeed after ${numberOfYMapTests} actions, no GC, all users disconnecting/reconnecting`, async(function * (done) {
-        yield applyRandomTransactionsAllRejoinNoGC(this.users, this.maps, randomMapTransactions, numberOfYMapTests)
-        yield flushAll()
-        yield compareMapValues(this.maps)
-        done()
-      }))
-      it(`succeed after ${numberOfYMapTests} actions, GC, user[0] is not disconnecting`, async(function * (done) {
-        yield applyRandomTransactionsWithGC(this.users, this.maps, randomMapTransactions, numberOfYMapTests)
-        yield flushAll()
-        yield compareMapValues(this.maps)
-        done()
-      }))
-    })
-  })
-}
--- a/src/Types/TextBind.js
+++ b/src/Types/TextBind.js
@@ -1,290 +0,0 @@
-/* global Y */
-'use strict'
-
-;(function () {
-  class YTextBind extends Y.Array['class'] {
-    constructor (os, _model, idArray, valArray) {
-      super(os, _model, idArray, valArray)
-      this.textfields = []
-    }
-    toString () {
-      return this.valArray.join('')
-    }
-    insert (pos, content) {
-      super.insert(pos, content.split(''))
-    }
-    bind (textfield, domRoot) {
-      domRoot = domRoot || window; // eslint-disable-line
-      if (domRoot.getSelection == null) {
-        domRoot = window;// eslint-disable-line
-      }
-
-      // don't duplicate!
-      for (var t in this.textfields) {
-        if (this.textfields[t] === textfield) {
-          return
-        }
-      }
-      var creatorToken = false
-
-      var word = this
-      textfield.value = this.toString()
-      this.textfields.push(textfield)
-      var createRange, writeRange, writeContent
-      if (textfield.selectionStart != null && textfield.setSelectionRange != null) {
-        createRange = function (fix) {
-          var left = textfield.selectionStart
-          var right = textfield.selectionEnd
-          if (fix != null) {
-            left = fix(left)
-            right = fix(right)
-          }
-          return {
-            left: left,
-            right: right
-          }
-        }
-        writeRange = function (range) {
-          writeContent(word.toString())
-          textfield.setSelectionRange(range.left, range.right)
-        }
-        writeContent = function (content) {
-          textfield.value = content
-        }
-      } else {
-        createRange = function (fix) {
-          var range = {}
-          var s = domRoot.getSelection()
-          var clength = textfield.textContent.length
-          range.left = Math.min(s.anchorOffset, clength)
-          range.right = Math.min(s.focusOffset, clength)
-          if (fix != null) {
-            range.left = fix(range.left)
-            range.right = fix(range.right)
-          }
-          var editedElement = s.focusNode
-          if (editedElement === textfield || editedElement === textfield.childNodes[0]) {
-            range.isReal = true
-          } else {
-            range.isReal = false
-          }
-          return range
-        }
-
-        writeRange = function (range) {
-          writeContent(word.toString())
-          var textnode = textfield.childNodes[0]
-          if (range.isReal && textnode != null) {
-            if (range.left < 0) {
-              range.left = 0
-            }
-            range.right = Math.max(range.left, range.right)
-            if (range.right > textnode.length) {
-              range.right = textnode.length
-            }
-            range.left = Math.min(range.left, range.right)
-            var r = document.createRange(); // eslint-disable-line
-            r.setStart(textnode, range.left)
-            r.setEnd(textnode, range.right)
-            var s = window.getSelection(); // eslint-disable-line
-            s.removeAllRanges()
-            s.addRange(r)
-          }
-        }
-        writeContent = function (content) {
-          var contentArray = content.replace(new RegExp('\n', 'g'), ' ').split(' ');// eslint-disable-line
-          textfield.innerText = ''
-          for (var i in contentArray) {
-            var c = contentArray[i]
-            textfield.innerText += c
-            if (i !== contentArray.length - 1) {
-              textfield.innerHTML += '&nbsp;'
-            }
-          }
-        }
-      }
-      writeContent(this.toString())
-
-      this.observe(function (events) {
-        for (var e in events) {
-          var event = events[e]
-          if (!creatorToken) {
-            var oPos, fix
-            if (event.type === 'insert') {
-              oPos = event.index
-              fix = function (cursor) {// eslint-disable-line
-                if (cursor <= oPos) {
-                  return cursor
-                } else {
-                  cursor += 1
-                  return cursor
-                }
-              }
-              var r = createRange(fix)
-              writeRange(r)
-            } else if (event.type === 'delete') {
-              oPos = event.index
-              fix = function (cursor) {// eslint-disable-line
-                if (cursor < oPos) {
-                  return cursor
-                } else {
-                  cursor -= 1
-                  return cursor
-                }
-              }
-              r = createRange(fix)
-              writeRange(r)
-            }
-          }
-        }
-      })
-      // consume all text-insert changes.
-      textfield.onkeypress = function (event) {
-        if (word.is_deleted) {
-          // if word is deleted, do not do anything ever again
-          textfield.onkeypress = null
-          return true
-        }
-        creatorToken = true
-        var char
-        if (event.keyCode === 13) {
-          char = '\n'
-        } else if (event.key != null) {
-          if (event.charCode === 32) {
-            char = ' '
-          } else {
-            char = event.key
-          }
-        } else {
-          char = window.String.fromCharCode(event.keyCode); // eslint-disable-line
-        }
-        if (char.length > 1) {
-          return true
-        } else if (char.length > 0) {
-          var r = createRange()
-          var pos = Math.min(r.left, r.right, word.length)
-          var diff = Math.abs(r.right - r.left)
-          word.delete(pos, diff)
-          word.insert(pos, char)
-          r.left = pos + char.length
-          r.right = r.left
-          writeRange(r)
-        }
-        event.preventDefault()
-        creatorToken = false
-        return false
-      }
-      textfield.onpaste = function (event) {
-        if (word.is_deleted) {
-          // if word is deleted, do not do anything ever again
-          textfield.onpaste = null
-          return true
-        }
-        event.preventDefault()
-      }
-      textfield.oncut = function (event) {
-        if (word.is_deleted) {
-          // if word is deleted, do not do anything ever again
-          textfield.oncut = null
-          return true
-        }
-        event.preventDefault()
-      }
-      //
-      // consume deletes. Note that
-      //   chrome: won't consume deletions on keypress event.
-      //   keyCode is deprecated. BUT: I don't see another way.
-      //     since event.key is not implemented in the current version of chrome.
-      //     Every browser supports keyCode. Let's stick with it for now..
-      //
-      textfield.onkeydown = function (event) {
-        creatorToken = true
-        if (word.is_deleted) {
-          // if word is deleted, do not do anything ever again
-          textfield.onkeydown = null
-          return true
-        }
-        var r = createRange()
-        var pos = Math.min(r.left, r.right, word.toString().length)
-        var diff = Math.abs(r.left - r.right)
-        if (event.keyCode != null && event.keyCode === 8) { // Backspace
-          if (diff > 0) {
-            word.delete(pos, diff)
-            r.left = pos
-            r.right = pos
-            writeRange(r)
-          } else {
-            if (event.ctrlKey != null && event.ctrlKey) {
-              var val = word.toString()
-              var newPos = pos
-              var delLength = 0
-              if (pos > 0) {
-                newPos--
-                delLength++
-              }
-              while (newPos > 0 && val[newPos] !== ' ' && val[newPos] !== '\n') {
-                newPos--
-                delLength++
-              }
-              word.delete(newPos, pos - newPos)
-              r.left = newPos
-              r.right = newPos
-              writeRange(r)
-            } else {
-              if (pos > 0) {
-                word.delete(pos - 1, 1)
-                r.left = pos - 1
-                r.right = pos - 1
-                writeRange(r)
-              }
-            }
-          }
-          event.preventDefault()
-          creatorToken = false
-          return false
-        } else if (event.keyCode != null && event.keyCode === 46) { // Delete
-          if (diff > 0) {
-            word.delete(pos, diff)
-            r.left = pos
-            r.right = pos
-            writeRange(r)
-          } else {
-            word.delete(pos, 1)
-            r.left = pos
-            r.right = pos
-            writeRange(r)
-          }
-          event.preventDefault()
-          creatorToken = false
-          return false
-        } else {
-          creatorToken = false
-          return true
-        }
-      }
-    }
-  }
-  Y.TextBind = new Y.utils.CustomType({
-    class: YTextBind,
-    createType: function * YTextBindCreator () {
-      var modelid = this.store.getNextOpId()
-      var model = {
-        start: null,
-        end: null,
-        struct: 'List',
-        type: 'TextBind',
-        id: modelid
-      }
-      yield* this.applyCreatedOperations([model])
-      return modelid
-    },
-    initType: function * YTextBindInitializer (os, model) {
-      var valArray = []
-      var idArray = yield* Y.Struct.List.map.call(this, model, function (c) {
-        valArray.push(c.content)
-        return JSON.stringify(c.id)
-      })
-      return new YTextBind(os, model.id, idArray, valArray)
-    }
-  })
-})()
--- a/src/Utils.js
+++ b/src/Utils.js
@@ -1,198 +0,0 @@
-/* global Y */
-'use strict'
-
-/*
-  EventHandler is an helper class for constructing custom types.
-
-  Why: When constructing custom types, you sometimes want your types to work
-  synchronous: E.g.
-  ``` Synchronous
-  mytype.setSomething("yay")
-  mytype.getSomething() === "yay"
-  ```
-  ``` Asynchronous
-  mytype.setSomething("yay")
-  mytype.getSomething() === undefined
-  mytype.waitForSomething().then(function(){
-    mytype.getSomething() === "yay"
-  })
-
-  The structures usually work asynchronously (you have to wait for the
-  database request to finish). EventHandler will help you to make your type
-  synchronously.
-*/
-class EventHandler {
-  /*
-    onevent: is called when the structure changes.
-
-    Note: "awaiting opertations" is used to denote operations that were
-    prematurely called. Events for received operations can not be executed until
-    all prematurely called operations were executed ("waiting operations")
-  */
-  constructor (onevent) {
-    this.waiting = []
-    this.awaiting = 0
-    this.onevent = onevent
-    this.eventListeners = []
-  }
-  /*
-    Call this when a new operation arrives. It will be executed right away if
-    there are no waiting operations, that you prematurely executed
-  */
-  receivedOp (op) {
-    if (this.awaiting <= 0) {
-      this.onevent([op])
-    } else {
-      this.waiting.push(Y.utils.copyObject(op))
-    }
-  }
-  /*
-    You created some operations, and you want the `onevent` function to be
-    called right away. Received operations will not be executed untill all
-    prematurely called operations are executed
-  */
-  awaitAndPrematurelyCall (ops) {
-    this.awaiting++
-    this.onevent(ops)
-  }
-  /*
-    Basic event listener boilerplate...
-    TODO: maybe put this in a different type..
-  */
-  addEventListener (f) {
-    this.eventListeners.push(f)
-  }
-  removeEventListener (f) {
-    this.eventListeners = this.eventListeners.filter(function (g) {
-      return f !== g
-    })
-  }
-  removeAllEventListeners () {
-    this.eventListeners = []
-  }
-  callEventListeners (event) {
-    for (var i in this.eventListeners) {
-      try {
-        this.eventListeners[i](event)
-      } catch (e) {
-        console.log('User events must not throw Errors!') // eslint-disable-line
-      }
-    }
-  }
-  /*
-    Call this when you successfully awaited the execution of n Insert operations
-  */
-  awaitedInserts (n) {
-    var ops = this.waiting.splice(this.waiting.length - n)
-    for (var oid = 0; oid < ops.length; oid++) {
-      var op = ops[oid]
-      for (var i = this.waiting.length - 1; i >= 0; i--) {
-        let w = this.waiting[i]
-        if (Y.utils.compareIds(op.left, w.id)) {
-          // include the effect of op in w
-          w.right = op.id
-          // exclude the effect of w in op
-          op.left = w.left
-        } else if (Y.utils.compareIds(op.right, w.id)) {
-          // similar..
-          w.left = op.id
-          op.right = w.right
-        }
-      }
-    }
-    this._tryCallEvents()
-  }
-  /*
-    Call this when you successfully awaited the execution of n Delete operations
-  */
-  awaitedDeletes (n, newLeft) {
-    var ops = this.waiting.splice(this.waiting.length - n)
-    for (var j in ops) {
-      var del = ops[j]
-      if (newLeft != null) {
-        for (var i in this.waiting) {
-          let w = this.waiting[i]
-          // We will just care about w.left
-          if (Y.utils.compareIds(del.target, w.left)) {
-            del.left = newLeft
-          }
-        }
-      }
-    }
-    this._tryCallEvents()
-  }
-  /* (private)
-    Try to execute the events for the waiting operations
-  */
-  _tryCallEvents () {
-    this.awaiting--
-    if (this.awaiting <= 0 && this.waiting.length > 0) {
-      var events = this.waiting
-      this.waiting = []
-      this.onevent(events)
-    }
-  }
-}
-Y.utils.EventHandler = EventHandler
-
-/*
-  A wrapper for the definition of a custom type.
-  Every custom type must have three properties:
-
-  * createType
-    - Defines the model of a newly created custom type and returns the type
-  * initType
-    - Given a model, creates a custom type
-  * class
-    - the constructor of the custom type (e.g. in order to inherit from a type)
-*/
-class CustomType { // eslint-disable-line
-  constructor (def) {
-    if (def.createType == null ||
-      def.initType == null ||
-      def.class == null
-    ) {
-      throw new Error('Custom type was not initialized correctly!')
-    }
-    this.createType = def.createType
-    this.initType = def.initType
-    this.class = def.class
-  }
-}
-Y.utils.CustomType = CustomType
-
-/*
-  Make a flat copy of an object
-  (just copy properties)
-*/
-function copyObject (o) {
-  var c = {}
-  for (var key in o) {
-    c[key] = o[key]
-  }
-  return c
-}
-Y.utils.copyObject = copyObject
-
-/*
-  Defines a smaller relation on Id's
-*/
-function smaller (a, b) {
-  return a[0] < b[0] || (a[0] === b[0] && a[1] < b[1])
-}
-Y.utils.smaller = smaller
-
-function compareIds (id1, id2) {
-  if (id1 == null || id2 == null) {
-    if (id1 == null && id2 == null) {
-      return true
-    }
-    return false
-  }
-  if (id1[0] === id2[0] && id1[1] === id2[1]) {
-    return true
-  } else {
-    return false
-  }
-}
-Y.utils.compareIds = compareIds
--- a/src/index.js
+++ b/src/index.js
@@ -0,0 +1,63 @@
+
+export {
+  Doc,
+  Transaction,
+  YArray as Array,
+  YMap as Map,
+  YText as Text,
+  YXmlText as XmlText,
+  YXmlHook as XmlHook,
+  YXmlElement as XmlElement,
+  YXmlFragment as XmlFragment,
+  YXmlEvent,
+  YMapEvent,
+  YArrayEvent,
+  YEvent,
+  Item,
+  AbstractStruct,
+  GC,
+  ContentBinary,
+  ContentDeleted,
+  ContentEmbed,
+  ContentFormat,
+  ContentJSON,
+  ContentAny,
+  ContentString,
+  ContentType,
+  AbstractType,
+  RelativePosition,
+  getTypeChildren,
+  createRelativePositionFromTypeIndex,
+  createRelativePositionFromJSON,
+  createAbsolutePositionFromRelativePosition,
+  compareRelativePositions,
+  writeRelativePosition,
+  readRelativePosition,
+  ID,
+  createID,
+  compareIDs,
+  getState,
+  Snapshot,
+  createSnapshot,
+  createDeleteSet,
+  createDeleteSetFromStructStore,
+  snapshot,
+  emptySnapshot,
+  findRootTypeKey,
+  typeListToArraySnapshot,
+  typeMapGetSnapshot,
+  iterateDeletedStructs,
+  applyUpdate,
+  readUpdate,
+  encodeStateAsUpdate,
+  encodeStateVector,
+  UndoManager,
+  decodeSnapshot,
+  encodeSnapshot,
+  isDeleted,
+  isParentOf,
+  equalSnapshots,
+  PermanentUserData, // @TODO experimental
+  tryGc,
+  transact
+} from './internals.js'
--- a/src/internals.js
+++ b/src/internals.js
@@ -0,0 +1,36 @@
+
+export * from './utils/DeleteSet.js'
+export * from './utils/Doc.js'
+export * from './utils/encoding.js'
+export * from './utils/EventHandler.js'
+export * from './utils/ID.js'
+export * from './utils/isParentOf.js'
+export * from './utils/PermanentUserData.js'
+export * from './utils/RelativePosition.js'
+export * from './utils/Snapshot.js'
+export * from './utils/StructStore.js'
+export * from './utils/Transaction.js'
+export * from './utils/UndoManager.js'
+export * from './utils/YEvent.js'
+
+export * from './types/AbstractType.js'
+export * from './types/YArray.js'
+export * from './types/YMap.js'
+export * from './types/YText.js'
+export * from './types/YXmlFragment.js'
+export * from './types/YXmlElement.js'
+export * from './types/YXmlEvent.js'
+export * from './types/YXmlHook.js'
+export * from './types/YXmlText.js'
+
+export * from './structs/AbstractStruct.js'
+export * from './structs/GC.js'
+export * from './structs/ContentBinary.js'
+export * from './structs/ContentDeleted.js'
+export * from './structs/ContentEmbed.js'
+export * from './structs/ContentFormat.js'
+export * from './structs/ContentJSON.js'
+export * from './structs/ContentAny.js'
+export * from './structs/ContentString.js'
+export * from './structs/ContentType.js'
+export * from './structs/Item.js'
--- a/src/structs/AbstractStruct.js
+++ b/src/structs/AbstractStruct.js
@@ -0,0 +1,53 @@
+
+import {
+  StructStore, ID, Transaction // eslint-disable-line
+} from '../internals.js'
+
+import * as encoding from 'lib0/encoding.js' // eslint-disable-line
+import * as error from 'lib0/error.js'
+
+export class AbstractStruct {
+  /**
+   * @param {ID} id
+   * @param {number} length
+   */
+  constructor (id, length) {
+    this.id = id
+    this.length = length
+  }
+
+  /**
+   * @type {boolean}
+   */
+  get deleted () {
+    throw error.methodUnimplemented()
+  }
+
+  /**
+   * Merge this struct with the item to the right.
+   * This method is already assuming that `this.id.clock + this.length === this.id.clock`.
+   * Also this method does *not* remove right from StructStore!
+   * @param {AbstractStruct} right
+   * @return {boolean} wether this merged with right
+   */
+  mergeWith (right) {
+    return false
+  }
+
+  /**
+   * @param {encoding.Encoder} encoder The encoder to write data to.
+   * @param {number} offset
+   * @param {number} encodingRef
+   */
+  write (encoder, offset, encodingRef) {
+    throw error.methodUnimplemented()
+  }
+
+  /**
+   * @param {Transaction} transaction
+   * @param {number} offset
+   */
+  integrate (transaction, offset) {
+    throw error.methodUnimplemented()
+  }
+}
--- a/src/structs/ContentAny.js
+++ b/src/structs/ContentAny.js
@@ -0,0 +1,111 @@
+import {
+  Transaction, Item, StructStore // eslint-disable-line
+} from '../internals.js'
+
+import * as encoding from 'lib0/encoding.js'
+import * as decoding from 'lib0/decoding.js'
+
+export class ContentAny {
+  /**
+   * @param {Array<any>} arr
+   */
+  constructor (arr) {
+    /**
+     * @type {Array<any>}
+     */
+    this.arr = arr
+  }
+
+  /**
+   * @return {number}
+   */
+  getLength () {
+    return this.arr.length
+  }
+
+  /**
+   * @return {Array<any>}
+   */
+  getContent () {
+    return this.arr
+  }
+
+  /**
+   * @return {boolean}
+   */
+  isCountable () {
+    return true
+  }
+
+  /**
+   * @return {ContentAny}
+   */
+  copy () {
+    return new ContentAny(this.arr)
+  }
+
+  /**
+   * @param {number} offset
+   * @return {ContentAny}
+   */
+  splice (offset) {
+    const right = new ContentAny(this.arr.slice(offset))
+    this.arr = this.arr.slice(0, offset)
+    return right
+  }
+
+  /**
+   * @param {ContentAny} right
+   * @return {boolean}
+   */
+  mergeWith (right) {
+    this.arr = this.arr.concat(right.arr)
+    return true
+  }
+
+  /**
+   * @param {Transaction} transaction
+   * @param {Item} item
+   */
+  integrate (transaction, item) {}
+  /**
+   * @param {Transaction} transaction
+   */
+  delete (transaction) {}
+  /**
+   * @param {StructStore} store
+   */
+  gc (store) {}
+  /**
+   * @param {encoding.Encoder} encoder
+   * @param {number} offset
+   */
+  write (encoder, offset) {
+    const len = this.arr.length
+    encoding.writeVarUint(encoder, len - offset)
+    for (let i = offset; i < len; i++) {
+      const c = this.arr[i]
+      encoding.writeAny(encoder, c)
+    }
+  }
+
+  /**
+   * @return {number}
+   */
+  getRef () {
+    return 8
+  }
+}
+
+/**
+ * @param {decoding.Decoder} decoder
+ * @return {ContentAny}
+ */
+export const readContentAny = decoder => {
+  const len = decoding.readVarUint(decoder)
+  const cs = []
+  for (let i = 0; i < len; i++) {
+    cs.push(decoding.readAny(decoder))
+  }
+  return new ContentAny(cs)
+}
--- a/src/structs/ContentBinary.js
+++ b/src/structs/ContentBinary.js
@@ -0,0 +1,95 @@
+import {
+  StructStore, Item, Transaction // eslint-disable-line
+} from '../internals.js'
+
+import * as encoding from 'lib0/encoding.js'
+import * as decoding from 'lib0/decoding.js'
+import * as buffer from 'lib0/buffer.js'
+import * as error from 'lib0/error.js'
+
+export class ContentBinary {
+  /**
+   * @param {Uint8Array} content
+   */
+  constructor (content) {
+    this.content = content
+  }
+
+  /**
+   * @return {number}
+   */
+  getLength () {
+    return 1
+  }
+
+  /**
+   * @return {Array<any>}
+   */
+  getContent () {
+    return [this.content]
+  }
+
+  /**
+   * @return {boolean}
+   */
+  isCountable () {
+    return true
+  }
+
+  /**
+   * @return {ContentBinary}
+   */
+  copy () {
+    return new ContentBinary(this.content)
+  }
+
+  /**
+   * @param {number} offset
+   * @return {ContentBinary}
+   */
+  splice (offset) {
+    throw error.methodUnimplemented()
+  }
+
+  /**
+   * @param {ContentBinary} right
+   * @return {boolean}
+   */
+  mergeWith (right) {
+    return false
+  }
+
+  /**
+   * @param {Transaction} transaction
+   * @param {Item} item
+   */
+  integrate (transaction, item) {}
+  /**
+   * @param {Transaction} transaction
+   */
+  delete (transaction) {}
+  /**
+   * @param {StructStore} store
+   */
+  gc (store) {}
+  /**
+   * @param {encoding.Encoder} encoder
+   * @param {number} offset
+   */
+  write (encoder, offset) {
+    encoding.writeVarUint8Array(encoder, this.content)
+  }
+
+  /**
+   * @return {number}
+   */
+  getRef () {
+    return 3
+  }
+}
+
+/**
+ * @param {decoding.Decoder} decoder
+ * @return {ContentBinary}
+ */
+export const readContentBinary = decoder => new ContentBinary(buffer.copyUint8Array(decoding.readVarUint8Array(decoder)))
--- a/src/structs/ContentDeleted.js
+++ b/src/structs/ContentDeleted.js
@@ -0,0 +1,104 @@
+
+import {
+  addToDeleteSet,
+  StructStore, Item, Transaction // eslint-disable-line
+} from '../internals.js'
+
+import * as encoding from 'lib0/encoding.js'
+import * as decoding from 'lib0/decoding.js'
+
+export class ContentDeleted {
+  /**
+   * @param {number} len
+   */
+  constructor (len) {
+    this.len = len
+  }
+
+  /**
+   * @return {number}
+   */
+  getLength () {
+    return this.len
+  }
+
+  /**
+   * @return {Array<any>}
+   */
+  getContent () {
+    return []
+  }
+
+  /**
+   * @return {boolean}
+   */
+  isCountable () {
+    return false
+  }
+
+  /**
+   * @return {ContentDeleted}
+   */
+  copy () {
+    return new ContentDeleted(this.len)
+  }
+
+  /**
+   * @param {number} offset
+   * @return {ContentDeleted}
+   */
+  splice (offset) {
+    const right = new ContentDeleted(this.len - offset)
+    this.len = offset
+    return right
+  }
+
+  /**
+   * @param {ContentDeleted} right
+   * @return {boolean}
+   */
+  mergeWith (right) {
+    this.len += right.len
+    return true
+  }
+
+  /**
+   * @param {Transaction} transaction
+   * @param {Item} item
+   */
+  integrate (transaction, item) {
+    addToDeleteSet(transaction.deleteSet, item.id, this.len)
+    item.markDeleted()
+  }
+
+  /**
+   * @param {Transaction} transaction
+   */
+  delete (transaction) {}
+  /**
+   * @param {StructStore} store
+   */
+  gc (store) {}
+  /**
+   * @param {encoding.Encoder} encoder
+   * @param {number} offset
+   */
+  write (encoder, offset) {
+    encoding.writeVarUint(encoder, this.len - offset)
+  }
+
+  /**
+   * @return {number}
+   */
+  getRef () {
+    return 1
+  }
+}
+
+/**
+ * @private
+ *
+ * @param {decoding.Decoder} decoder
+ * @return {ContentDeleted}
+ */
+export const readContentDeleted = decoder => new ContentDeleted(decoding.readVarUint(decoder))
--- a/src/structs/ContentEmbed.js
+++ b/src/structs/ContentEmbed.js
@@ -0,0 +1,100 @@
+
+import {
+  StructStore, Item, Transaction // eslint-disable-line
+} from '../internals.js'
+
+import * as encoding from 'lib0/encoding.js'
+import * as decoding from 'lib0/decoding.js'
+import * as error from 'lib0/error.js'
+
+/**
+ * @private
+ */
+export class ContentEmbed {
+  /**
+   * @param {Object} embed
+   */
+  constructor (embed) {
+    this.embed = embed
+  }
+
+  /**
+   * @return {number}
+   */
+  getLength () {
+    return 1
+  }
+
+  /**
+   * @return {Array<any>}
+   */
+  getContent () {
+    return [this.embed]
+  }
+
+  /**
+   * @return {boolean}
+   */
+  isCountable () {
+    return true
+  }
+
+  /**
+   * @return {ContentEmbed}
+   */
+  copy () {
+    return new ContentEmbed(this.embed)
+  }
+
+  /**
+   * @param {number} offset
+   * @return {ContentEmbed}
+   */
+  splice (offset) {
+    throw error.methodUnimplemented()
+  }
+
+  /**
+   * @param {ContentEmbed} right
+   * @return {boolean}
+   */
+  mergeWith (right) {
+    return false
+  }
+
+  /**
+   * @param {Transaction} transaction
+   * @param {Item} item
+   */
+  integrate (transaction, item) {}
+  /**
+   * @param {Transaction} transaction
+   */
+  delete (transaction) {}
+  /**
+   * @param {StructStore} store
+   */
+  gc (store) {}
+  /**
+   * @param {encoding.Encoder} encoder
+   * @param {number} offset
+   */
+  write (encoder, offset) {
+    encoding.writeVarString(encoder, JSON.stringify(this.embed))
+  }
+
+  /**
+   * @return {number}
+   */
+  getRef () {
+    return 5
+  }
+}
+
+/**
+ * @private
+ *
+ * @param {decoding.Decoder} decoder
+ * @return {ContentEmbed}
+ */
+export const readContentEmbed = decoder => new ContentEmbed(JSON.parse(decoding.readVarString(decoder)))
--- a/src/structs/ContentFormat.js
+++ b/src/structs/ContentFormat.js
@@ -0,0 +1,101 @@
+
+import {
+  Item, StructStore, Transaction // eslint-disable-line
+} from '../internals.js'
+
+import * as encoding from 'lib0/encoding.js'
+import * as decoding from 'lib0/decoding.js'
+import * as error from 'lib0/error.js'
+
+/**
+ * @private
+ */
+export class ContentFormat {
+  /**
+   * @param {string} key
+   * @param {Object} value
+   */
+  constructor (key, value) {
+    this.key = key
+    this.value = value
+  }
+
+  /**
+   * @return {number}
+   */
+  getLength () {
+    return 1
+  }
+
+  /**
+   * @return {Array<any>}
+   */
+  getContent () {
+    return []
+  }
+
+  /**
+   * @return {boolean}
+   */
+  isCountable () {
+    return false
+  }
+
+  /**
+   * @return {ContentFormat}
+   */
+  copy () {
+    return new ContentFormat(this.key, this.value)
+  }
+
+  /**
+   * @param {number} offset
+   * @return {ContentFormat}
+   */
+  splice (offset) {
+    throw error.methodUnimplemented()
+  }
+
+  /**
+   * @param {ContentFormat} right
+   * @return {boolean}
+   */
+  mergeWith (right) {
+    return false
+  }
+
+  /**
+   * @param {Transaction} transaction
+   * @param {Item} item
+   */
+  integrate (transaction, item) {}
+  /**
+   * @param {Transaction} transaction
+   */
+  delete (transaction) {}
+  /**
+   * @param {StructStore} store
+   */
+  gc (store) {}
+  /**
+   * @param {encoding.Encoder} encoder
+   * @param {number} offset
+   */
+  write (encoder, offset) {
+    encoding.writeVarString(encoder, this.key)
+    encoding.writeVarString(encoder, JSON.stringify(this.value))
+  }
+
+  /**
+   * @return {number}
+   */
+  getRef () {
+    return 6
+  }
+}
+
+/**
+ * @param {decoding.Decoder} decoder
+ * @return {ContentFormat}
+ */
+export const readContentFormat = decoder => new ContentFormat(decoding.readVarString(decoder), JSON.parse(decoding.readVarString(decoder)))
--- a/src/structs/ContentJSON.js
+++ b/src/structs/ContentJSON.js
@@ -0,0 +1,121 @@
+import {
+  Transaction, Item, StructStore // eslint-disable-line
+} from '../internals.js'
+
+import * as encoding from 'lib0/encoding.js'
+import * as decoding from 'lib0/decoding.js'
+
+/**
+ * @private
+ */
+export class ContentJSON {
+  /**
+   * @param {Array<any>} arr
+   */
+  constructor (arr) {
+    /**
+     * @type {Array<any>}
+     */
+    this.arr = arr
+  }
+
+  /**
+   * @return {number}
+   */
+  getLength () {
+    return this.arr.length
+  }
+
+  /**
+   * @return {Array<any>}
+   */
+  getContent () {
+    return this.arr
+  }
+
+  /**
+   * @return {boolean}
+   */
+  isCountable () {
+    return true
+  }
+
+  /**
+   * @return {ContentJSON}
+   */
+  copy () {
+    return new ContentJSON(this.arr)
+  }
+
+  /**
+   * @param {number} offset
+   * @return {ContentJSON}
+   */
+  splice (offset) {
+    const right = new ContentJSON(this.arr.slice(offset))
+    this.arr = this.arr.slice(0, offset)
+    return right
+  }
+
+  /**
+   * @param {ContentJSON} right
+   * @return {boolean}
+   */
+  mergeWith (right) {
+    this.arr = this.arr.concat(right.arr)
+    return true
+  }
+
+  /**
+   * @param {Transaction} transaction
+   * @param {Item} item
+   */
+  integrate (transaction, item) {}
+  /**
+   * @param {Transaction} transaction
+   */
+  delete (transaction) {}
+  /**
+   * @param {StructStore} store
+   */
+  gc (store) {}
+  /**
+   * @param {encoding.Encoder} encoder
+   * @param {number} offset
+   */
+  write (encoder, offset) {
+    const len = this.arr.length
+    encoding.writeVarUint(encoder, len - offset)
+    for (let i = offset; i < len; i++) {
+      const c = this.arr[i]
+      encoding.writeVarString(encoder, c === undefined ? 'undefined' : JSON.stringify(c))
+    }
+  }
+
+  /**
+   * @return {number}
+   */
+  getRef () {
+    return 2
+  }
+}
+
+/**
+ * @private
+ *
+ * @param {decoding.Decoder} decoder
+ * @return {ContentJSON}
+ */
+export const readContentJSON = decoder => {
+  const len = decoding.readVarUint(decoder)
+  const cs = []
+  for (let i = 0; i < len; i++) {
+    const c = decoding.readVarString(decoder)
+    if (c === 'undefined') {
+      cs.push(undefined)
+    } else {
+      cs.push(JSON.parse(c))
+    }
+  }
+  return new ContentJSON(cs)
+}
--- a/src/structs/ContentString.js
+++ b/src/structs/ContentString.js
@@ -0,0 +1,104 @@
+import {
+  Transaction, Item, StructStore // eslint-disable-line
+} from '../internals.js'
+
+import * as encoding from 'lib0/encoding.js'
+import * as decoding from 'lib0/decoding.js'
+
+/**
+ * @private
+ */
+export class ContentString {
+  /**
+   * @param {string} str
+   */
+  constructor (str) {
+    /**
+     * @type {string}
+     */
+    this.str = str
+  }
+
+  /**
+   * @return {number}
+   */
+  getLength () {
+    return this.str.length
+  }
+
+  /**
+   * @return {Array<any>}
+   */
+  getContent () {
+    return this.str.split('')
+  }
+
+  /**
+   * @return {boolean}
+   */
+  isCountable () {
+    return true
+  }
+
+  /**
+   * @return {ContentString}
+   */
+  copy () {
+    return new ContentString(this.str)
+  }
+
+  /**
+   * @param {number} offset
+   * @return {ContentString}
+   */
+  splice (offset) {
+    const right = new ContentString(this.str.slice(offset))
+    this.str = this.str.slice(0, offset)
+    return right
+  }
+
+  /**
+   * @param {ContentString} right
+   * @return {boolean}
+   */
+  mergeWith (right) {
+    this.str += right.str
+    return true
+  }
+
+  /**
+   * @param {Transaction} transaction
+   * @param {Item} item
+   */
+  integrate (transaction, item) {}
+  /**
+   * @param {Transaction} transaction
+   */
+  delete (transaction) {}
+  /**
+   * @param {StructStore} store
+   */
+  gc (store) {}
+  /**
+   * @param {encoding.Encoder} encoder
+   * @param {number} offset
+   */
+  write (encoder, offset) {
+    encoding.writeVarString(encoder, offset === 0 ? this.str : this.str.slice(offset))
+  }
+
+  /**
+   * @return {number}
+   */
+  getRef () {
+    return 4
+  }
+}
+
+/**
+ * @private
+ *
+ * @param {decoding.Decoder} decoder
+ * @return {ContentString}
+ */
+export const readContentString = decoder => new ContentString(decoding.readVarString(decoder))
--- a/src/structs/ContentType.js
+++ b/src/structs/ContentType.js
@@ -0,0 +1,174 @@
+
+import {
+  readYArray,
+  readYMap,
+  readYText,
+  readYXmlElement,
+  readYXmlFragment,
+  readYXmlHook,
+  readYXmlText,
+  ID, StructStore, Transaction, Item, YEvent, AbstractType // eslint-disable-line
+} from '../internals.js'
+
+import * as encoding from 'lib0/encoding.js' // eslint-disable-line
+import * as decoding from 'lib0/decoding.js'
+import * as error from 'lib0/error.js'
+
+/**
+ * @type {Array<function(decoding.Decoder):AbstractType<any>>}
+ * @private
+ */
+export const typeRefs = [
+  readYArray,
+  readYMap,
+  readYText,
+  readYXmlElement,
+  readYXmlFragment,
+  readYXmlHook,
+  readYXmlText
+]
+
+export const YArrayRefID = 0
+export const YMapRefID = 1
+export const YTextRefID = 2
+export const YXmlElementRefID = 3
+export const YXmlFragmentRefID = 4
+export const YXmlHookRefID = 5
+export const YXmlTextRefID = 6
+
+/**
+ * @private
+ */
+export class ContentType {
+  /**
+   * @param {AbstractType<YEvent>} type
+   */
+  constructor (type) {
+    /**
+     * @type {AbstractType<any>}
+     */
+    this.type = type
+  }
+
+  /**
+   * @return {number}
+   */
+  getLength () {
+    return 1
+  }
+
+  /**
+   * @return {Array<any>}
+   */
+  getContent () {
+    return [this.type]
+  }
+
+  /**
+   * @return {boolean}
+   */
+  isCountable () {
+    return true
+  }
+
+  /**
+   * @return {ContentType}
+   */
+  copy () {
+    return new ContentType(this.type._copy())
+  }
+
+  /**
+   * @param {number} offset
+   * @return {ContentType}
+   */
+  splice (offset) {
+    throw error.methodUnimplemented()
+  }
+
+  /**
+   * @param {ContentType} right
+   * @return {boolean}
+   */
+  mergeWith (right) {
+    return false
+  }
+
+  /**
+   * @param {Transaction} transaction
+   * @param {Item} item
+   */
+  integrate (transaction, item) {
+    this.type._integrate(transaction.doc, item)
+  }
+
+  /**
+   * @param {Transaction} transaction
+   */
+  delete (transaction) {
+    let item = this.type._start
+    while (item !== null) {
+      if (!item.deleted) {
+        item.delete(transaction)
+      } else {
+        // Whis will be gc'd later and we want to merge it if possible
+        // We try to merge all deleted items after each transaction,
+        // but we have no knowledge about that this needs to be merged
+        // since it is not in transaction.ds. Hence we add it to transaction._mergeStructs
+        transaction._mergeStructs.push(item)
+      }
+      item = item.right
+    }
+    this.type._map.forEach(item => {
+      if (!item.deleted) {
+        item.delete(transaction)
+      } else {
+        // same as above
+        transaction._mergeStructs.push(item)
+      }
+    })
+    transaction.changed.delete(this.type)
+  }
+
+  /**
+   * @param {StructStore} store
+   */
+  gc (store) {
+    let item = this.type._start
+    while (item !== null) {
+      item.gc(store, true)
+      item = item.right
+    }
+    this.type._start = null
+    this.type._map.forEach(/** @param {Item | null} item */ (item) => {
+      while (item !== null) {
+        item.gc(store, true)
+        item = item.left
+      }
+    })
+    this.type._map = new Map()
+  }
+
+  /**
+   * @param {encoding.Encoder} encoder
+   * @param {number} offset
+   */
+  write (encoder, offset) {
+    this.type._write(encoder)
+  }
+
+  /**
+   * @return {number}
+   */
+  getRef () {
+    return 7
+  }
+}
+
+/**
+ * @private
+ *
+ * @param {decoding.Decoder} decoder
+ * @return {ContentType}
+ */
+export const readContentType = decoder => new ContentType(typeRefs[decoding.readVarUint(decoder)](decoder))
--- a/src/structs/GC.js
+++ b/src/structs/GC.js
@@ -0,0 +1,60 @@
+
+import {
+  AbstractStruct,
+  addStruct,
+  StructStore, Transaction, ID // eslint-disable-line
+} from '../internals.js'
+
+import * as encoding from 'lib0/encoding.js'
+
+export const structGCRefNumber = 0
+
+/**
+ * @private
+ */
+export class GC extends AbstractStruct {
+  get deleted () {
+    return true
+  }
+
+  delete () {}
+
+  /**
+   * @param {GC} right
+   * @return {boolean}
+   */
+  mergeWith (right) {
+    this.length += right.length
+    return true
+  }
+
+  /**
+   * @param {Transaction} transaction
+   * @param {number} offset
+   */
+  integrate (transaction, offset) {
+    if (offset > 0) {
+      this.id.clock += offset
+      this.length -= offset
+    }
+    addStruct(transaction.doc.store, this)
+  }
+
+  /**
+   * @param {encoding.Encoder} encoder
+   * @param {number} offset
+   */
+  write (encoder, offset) {
+    encoding.writeUint8(encoder, structGCRefNumber)
+    encoding.writeVarUint(encoder, this.length - offset)
+  }
+
+  /**
+   * @param {Transaction} transaction
+   * @param {StructStore} store
+   * @return {null | number}
+   */
+  getMissing (transaction, store) {
+    return null
+  }
+}
--- a/src/structs/Item.js
+++ b/src/structs/Item.js
@@ -0,0 +1,785 @@
+
+import {
+  readID,
+  writeID,
+  GC,
+  getState,
+  AbstractStruct,
+  replaceStruct,
+  addStruct,
+  addToDeleteSet,
+  findRootTypeKey,
+  compareIDs,
+  getItem,
+  getItemCleanEnd,
+  getItemCleanStart,
+  readContentDeleted,
+  readContentBinary,
+  readContentJSON,
+  readContentAny,
+  readContentString,
+  readContentEmbed,
+  createID,
+  readContentFormat,
+  readContentType,
+  addChangedTypeToTransaction,
+  Doc, ContentType, ContentDeleted, StructStore, ID, AbstractType, Transaction // eslint-disable-line
+} from '../internals.js'
+
+import * as error from 'lib0/error.js'
+import * as encoding from 'lib0/encoding.js'
+import * as decoding from 'lib0/decoding.js'
+import * as maplib from 'lib0/map.js'
+import * as set from 'lib0/set.js'
+import * as binary from 'lib0/binary.js'
+
+/**
+ * @todo This should return several items
+ *
+ * @param {StructStore} store
+ * @param {ID} id
+ * @return {{item:Item, diff:number}}
+ */
+export const followRedone = (store, id) => {
+  /**
+   * @type {ID|null}
+   */
+  let nextID = id
+  let diff = 0
+  let item
+  do {
+    if (diff > 0) {
+      nextID = createID(nextID.client, nextID.clock + diff)
+    }
+    item = getItem(store, nextID)
+    diff = nextID.clock - item.id.clock
+    nextID = item.redone
+  } while (nextID !== null && item instanceof Item)
+  return {
+    item, diff
+  }
+}
+
+/**
+ * Make sure that neither item nor any of its parents is ever deleted.
+ *
+ * This property does not persist when storing it into a database or when
+ * sending it to other peers
+ *
+ * @param {Item|null} item
+ * @param {boolean} keep
+ */
+export const keepItem = (item, keep) => {
+  while (item !== null && item.keep !== keep) {
+    item.keep = keep
+    item = /** @type {AbstractType<any>} */ (item.parent)._item
+  }
+}
+
+/**
+ * Split leftItem into two items
+ * @param {Transaction} transaction
+ * @param {Item} leftItem
+ * @param {number} diff
+ * @return {Item}
+ *
+ * @function
+ * @private
+ */
+export const splitItem = (transaction, leftItem, diff) => {
+  // create rightItem
+  const { client, clock } = leftItem.id
+  const rightItem = new Item(
+    createID(client, clock + diff),
+    leftItem,
+    createID(client, clock + diff - 1),
+    leftItem.right,
+    leftItem.rightOrigin,
+    leftItem.parent,
+    leftItem.parentSub,
+    leftItem.content.splice(diff)
+  )
+  if (leftItem.deleted) {
+    rightItem.markDeleted()
+  }
+  if (leftItem.keep) {
+    rightItem.keep = true
+  }
+  if (leftItem.redone !== null) {
+    rightItem.redone = createID(leftItem.redone.client, leftItem.redone.clock + diff)
+  }
+  // update left (do not set leftItem.rightOrigin as it will lead to problems when syncing)
+  leftItem.right = rightItem
+  // update right
+  if (rightItem.right !== null) {
+    rightItem.right.left = rightItem
+  }
+  // right is more specific.
+  transaction._mergeStructs.push(rightItem)
+  // update parent._map
+  if (rightItem.parentSub !== null && rightItem.right === null) {
+    /** @type {AbstractType<any>} */ (rightItem.parent)._map.set(rightItem.parentSub, rightItem)
+  }
+  leftItem.length = diff
+  return rightItem
+}
+
+/**
+ * Redoes the effect of this operation.
+ *
+ * @param {Transaction} transaction The Yjs instance.
+ * @param {Item} item
+ * @param {Set<Item>} redoitems
+ *
+ * @return {Item|null}
+ *
+ * @private
+ */
+export const redoItem = (transaction, item, redoitems) => {
+  const doc = transaction.doc
+  const store = doc.store
+  const ownClientID = doc.clientID
+  const redone = item.redone
+  if (redone !== null) {
+    return getItemCleanStart(transaction, redone)
+  }
+  let parentItem = /** @type {AbstractType<any>} */ (item.parent)._item
+  /**
+   * @type {Item|null}
+   */
+  let left
+  /**
+   * @type {Item|null}
+   */
+  let right
+  if (item.parentSub === null) {
+    // Is an array item. Insert at the old position
+    left = item.left
+    right = item
+  } else {
+    // Is a map item. Insert as current value
+    left = item
+    while (left.right !== null) {
+      left = left.right
+      if (left.id.client !== ownClientID) {
+        // It is not possible to redo this item because it conflicts with a
+        // change from another client
+        return null
+      }
+    }
+    if (left.right !== null) {
+      left = /** @type {Item} */ (/** @type {AbstractType<any>} */ (item.parent)._map.get(item.parentSub))
+    }
+    right = null
+  }
+  // make sure that parent is redone
+  if (parentItem !== null && parentItem.deleted === true && parentItem.redone === null) {
+    // try to undo parent if it will be undone anyway
+    if (!redoitems.has(parentItem) || redoItem(transaction, parentItem, redoitems) === null) {
+      return null
+    }
+  }
+  if (parentItem !== null && parentItem.redone !== null) {
+    while (parentItem.redone !== null) {
+      parentItem = getItemCleanStart(transaction, parentItem.redone)
+    }
+    // find next cloned_redo items
+    while (left !== null) {
+      /**
+       * @type {Item|null}
+       */
+      let leftTrace = left
+      // trace redone until parent matches
+      while (leftTrace !== null && /** @type {AbstractType<any>} */ (leftTrace.parent)._item !== parentItem) {
+        leftTrace = leftTrace.redone === null ? null : getItemCleanStart(transaction, leftTrace.redone)
+      }
+      if (leftTrace !== null && /** @type {AbstractType<any>} */ (leftTrace.parent)._item === parentItem) {
+        left = leftTrace
+        break
+      }
+      left = left.left
+    }
+    while (right !== null) {
+      /**
+       * @type {Item|null}
+       */
+      let rightTrace = right
+      // trace redone until parent matches
+      while (rightTrace !== null && /** @type {AbstractType<any>} */ (rightTrace.parent)._item !== parentItem) {
+        rightTrace = rightTrace.redone === null ? null : getItemCleanStart(transaction, rightTrace.redone)
+      }
+      if (rightTrace !== null && /** @type {AbstractType<any>} */ (rightTrace.parent)._item === parentItem) {
+        right = rightTrace
+        break
+      }
+      right = right.right
+    }
+  }
+  const nextClock = getState(store, ownClientID)
+  const nextId = createID(ownClientID, nextClock)
+  const redoneItem = new Item(
+    nextId,
+    left, left && left.lastId,
+    right, right && right.id,
+    parentItem === null ? item.parent : /** @type {ContentType} */ (parentItem.content).type,
+    item.parentSub,
+    item.content.copy()
+  )
+  item.redone = nextId
+  keepItem(redoneItem, true)
+  redoneItem.integrate(transaction, 0)
+  return redoneItem
+}
+
+/**
+ * Abstract class that represents any content.
+ */
+export class Item extends AbstractStruct {
+  /**
+   * @param {ID} id
+   * @param {Item | null} left
+   * @param {ID | null} origin
+   * @param {Item | null} right
+   * @param {ID | null} rightOrigin
+   * @param {AbstractType<any>|ID|null} parent Is a type if integrated, is null if it is possible to copy parent from left or right, is ID before integration to search for it.
+   * @param {string | null} parentSub
+   * @param {AbstractContent} content
+   */
+  constructor (id, left, origin, right, rightOrigin, parent, parentSub, content) {
+    super(id, content.getLength())
+    /**
+     * The item that was originally to the left of this item.
+     * @type {ID | null}
+     */
+    this.origin = origin
+    /**
+     * The item that is currently to the left of this item.
+     * @type {Item | null}
+     */
+    this.left = left
+    /**
+     * The item that is currently to the right of this item.
+     * @type {Item | null}
+     */
+    this.right = right
+    /**
+     * The item that was originally to the right of this item.
+     * @type {ID | null}
+     */
+    this.rightOrigin = rightOrigin
+    /**
+     * @type {AbstractType<any>|ID|null}
+     */
+    this.parent = parent
+    /**
+     * If the parent refers to this item with some kind of key (e.g. YMap, the
+     * key is specified here. The key is then used to refer to the list in which
+     * to insert this item. If `parentSub = null` type._start is the list in
+     * which to insert to. Otherwise it is `parent._map`.
+     * @type {String | null}
+     */
+    this.parentSub = parentSub
+    /**
+     * If this type's effect is reundone this type refers to the type that undid
+     * this operation.
+     * @type {ID | null}
+     */
+    this.redone = null
+    /**
+     * @type {AbstractContent}
+     */
+    this.content = content
+    this.info = this.content.isCountable() ? binary.BIT2 : 0
+  }
+
+  /**
+   * If true, do not garbage collect this Item.
+   */
+  get keep () {
+    return (this.info & binary.BIT1) > 0
+  }
+
+  set keep (doKeep) {
+    if (this.keep !== doKeep) {
+      this.info ^= binary.BIT1
+    }
+  }
+
+  get countable () {
+    return (this.info & binary.BIT2) > 0
+  }
+
+  /**
+   * Whether this item was deleted or not.
+   * @type {Boolean}
+   */
+  get deleted () {
+    return (this.info & binary.BIT3) > 0
+  }
+
+  set deleted (doDelete) {
+    if (this.deleted !== doDelete) {
+      this.info ^= binary.BIT3
+    }
+  }
+
+  markDeleted () {
+    this.info |= binary.BIT3
+  }
+
+  /**
+   * Return the creator clientID of the missing op or define missing items and return null.
+   *
+   * @param {Transaction} transaction
+   * @param {StructStore} store
+   * @return {null | number}
+   */
+  getMissing (transaction, store) {
+    if (this.origin && this.origin.client !== this.id.client && this.origin.clock >= getState(store, this.origin.client)) {
+      return this.origin.client
+    }
+    if (this.rightOrigin && this.rightOrigin.client !== this.id.client && this.rightOrigin.clock >= getState(store, this.rightOrigin.client)) {
+      return this.rightOrigin.client
+    }
+    if (this.parent && this.parent.constructor === ID && this.id.client !== this.parent.client && this.parent.clock >= getState(store, this.parent.client)) {
+      return this.parent.client
+    }
+
+    // We have all missing ids, now find the items
+
+    if (this.origin) {
+      this.left = getItemCleanEnd(transaction, store, this.origin)
+      this.origin = this.left.lastId
+    }
+    if (this.rightOrigin) {
+      this.right = getItemCleanStart(transaction, this.rightOrigin)
+      this.rightOrigin = this.right.id
+    }
+    // only set parent if this shouldn't be garbage collected
+    if (!this.parent) {
+      if (this.left && this.left.constructor === Item) {
+        this.parent = this.left.parent
+        this.parentSub = this.left.parentSub
+      }
+      if (this.right && this.right.constructor === Item) {
+        this.parent = this.right.parent
+        this.parentSub = this.right.parentSub
+      }
+    } else if (this.parent.constructor === ID) {
+      const parentItem = getItem(store, this.parent)
+      if (parentItem.constructor === GC) {
+        this.parent = null
+      } else {
+        this.parent = /** @type {ContentType} */ (parentItem.content).type
+      }
+    }
+    return null
+  }
+
+  /**
+   * @param {Transaction} transaction
+   * @param {number} offset
+   */
+  integrate (transaction, offset) {
+    if (offset > 0) {
+      this.id.clock += offset
+      this.left = getItemCleanEnd(transaction, transaction.doc.store, createID(this.id.client, this.id.clock - 1))
+      this.origin = this.left.lastId
+      this.content = this.content.splice(offset)
+      this.length -= offset
+    }
+
+    if (this.parent) {
+      if ((!this.left && (!this.right || this.right.left !== null)) || (this.left && this.left.right !== this.right)) {
+        /**
+         * @type {Item|null}
+         */
+        let left = this.left
+
+        /**
+         * @type {Item|null}
+         */
+        let o
+        // set o to the first conflicting item
+        if (left !== null) {
+          o = left.right
+        } else if (this.parentSub !== null) {
+          o = /** @type {AbstractType<any>} */ (this.parent)._map.get(this.parentSub) || null
+          while (o !== null && o.left !== null) {
+            o = o.left
+          }
+        } else {
+          o = /** @type {AbstractType<any>} */ (this.parent)._start
+        }
+        // TODO: use something like DeleteSet here (a tree implementation would be best)
+        // @todo use global set definitions
+        /**
+         * @type {Set<Item>}
+         */
+        const conflictingItems = new Set()
+        /**
+         * @type {Set<Item>}
+         */
+        const itemsBeforeOrigin = new Set()
+        // Let c in conflictingItems, b in itemsBeforeOrigin
+        // ***{origin}bbbb{this}{c,b}{c,b}{o}***
+        // Note that conflictingItems is a subset of itemsBeforeOrigin
+        while (o !== null && o !== this.right) {
+          itemsBeforeOrigin.add(o)
+          conflictingItems.add(o)
+          if (compareIDs(this.origin, o.origin)) {
+            // case 1
+            if (o.id.client < this.id.client) {
+              left = o
+              conflictingItems.clear()
+            }
+          } else if (o.origin !== null && itemsBeforeOrigin.has(getItem(transaction.doc.store, o.origin))) {
+            // case 2
+            if (o.origin === null || !conflictingItems.has(getItem(transaction.doc.store, o.origin))) {
+              left = o
+              conflictingItems.clear()
+            }
+          } else {
+            break
+          }
+          o = o.right
+        }
+        this.left = left
+      }
+      // reconnect left/right + update parent map/start if necessary
+      if (this.left !== null) {
+        const right = this.left.right
+        this.right = right
+        this.left.right = this
+      } else {
+        let r
+        if (this.parentSub !== null) {
+          r = /** @type {AbstractType<any>} */ (this.parent)._map.get(this.parentSub) || null
+          while (r !== null && r.left !== null) {
+            r = r.left
+          }
+        } else {
+          r = /** @type {AbstractType<any>} */ (this.parent)._start
+          ;/** @type {AbstractType<any>} */ (this.parent)._start = this
+        }
+        this.right = r
+      }
+      if (this.right !== null) {
+        this.right.left = this
+      } else if (this.parentSub !== null) {
+        // set as current parent value if right === null and this is parentSub
+        /** @type {AbstractType<any>} */ (this.parent)._map.set(this.parentSub, this)
+        if (this.left !== null) {
+          // this is the current attribute value of parent. delete right
+          this.left.delete(transaction)
+        }
+      }
+      // adjust length of parent
+      if (this.parentSub === null && this.countable && !this.deleted) {
+        /** @type {AbstractType<any>} */ (this.parent)._length += this.length
+      }
+      addStruct(transaction.doc.store, this)
+      this.content.integrate(transaction, this)
+      // add parent to transaction.changed
+      addChangedTypeToTransaction(transaction, /** @type {AbstractType<any>} */ (this.parent), this.parentSub)
+      if ((/** @type {AbstractType<any>} */ (this.parent)._item !== null && /** @type {AbstractType<any>} */ (this.parent)._item.deleted) || (this.right !== null && this.parentSub !== null)) {
+        // delete if parent is deleted or if this is not the current attribute value of parent
+        this.delete(transaction)
+      }
+    } else {
+      // parent is not defined. Integrate GC struct instead
+      new GC(this.id, this.length).integrate(transaction, 0)
+    }
+  }
+
+  /**
+   * Returns the next non-deleted item
+   */
+  get next () {
+    let n = this.right
+    while (n !== null && n.deleted) {
+      n = n.right
+    }
+    return n
+  }
+
+  /**
+   * Returns the previous non-deleted item
+   */
+  get prev () {
+    let n = this.left
+    while (n !== null && n.deleted) {
+      n = n.left
+    }
+    return n
+  }
+
+  /**
+   * Computes the last content address of this Item.
+   */
+  get lastId () {
+    // allocating ids is pretty costly because of the amount of ids created, so we try to reuse whenever possible
+    return this.length === 1 ? this.id : createID(this.id.client, this.id.clock + this.length - 1)
+  }
+
+  /**
+   * Try to merge two items
+   *
+   * @param {Item} right
+   * @return {boolean}
+   */
+  mergeWith (right) {
+    if (
+      compareIDs(right.origin, this.lastId) &&
+      this.right === right &&
+      compareIDs(this.rightOrigin, right.rightOrigin) &&
+      this.id.client === right.id.client &&
+      this.id.clock + this.length === right.id.clock &&
+      this.deleted === right.deleted &&
+      this.redone === null &&
+      right.redone === null &&
+      this.content.constructor === right.content.constructor &&
+      this.content.mergeWith(right.content)
+    ) {
+      if (right.keep) {
+        this.keep = true
+      }
+      this.right = right.right
+      if (this.right !== null) {
+        this.right.left = this
+      }
+      this.length += right.length
+      return true
+    }
+    return false
+  }
+
+  /**
+   * Mark this Item as deleted.
+   *
+   * @param {Transaction} transaction
+   */
+  delete (transaction) {
+    if (!this.deleted) {
+      const parent = /** @type {AbstractType<any>} */ (this.parent)
+      // adjust the length of parent
+      if (this.countable && this.parentSub === null) {
+        parent._length -= this.length
+      }
+      this.markDeleted()
+      addToDeleteSet(transaction.deleteSet, this.id, this.length)
+      maplib.setIfUndefined(transaction.changed, parent, set.create).add(this.parentSub)
+      this.content.delete(transaction)
+    }
+  }
+
+  /**
+   * @param {StructStore} store
+   * @param {boolean} parentGCd
+   */
+  gc (store, parentGCd) {
+    if (!this.deleted) {
+      throw error.unexpectedCase()
+    }
+    this.content.gc(store)
+    if (parentGCd) {
+      replaceStruct(store, this, new GC(this.id, this.length))
+    } else {
+      this.content = new ContentDeleted(this.length)
+    }
+  }
+
+  /**
+   * Transform the properties of this type to binary and write it to an
+   * BinaryEncoder.
+   *
+   * This is called when this Item is sent to a remote peer.
+   *
+   * @param {encoding.Encoder} encoder The encoder to write data to.
+   * @param {number} offset
+   */
+  write (encoder, offset) {
+    const origin = offset > 0 ? createID(this.id.client, this.id.clock + offset - 1) : this.origin
+    const rightOrigin = this.rightOrigin
+    const parentSub = this.parentSub
+    const info = (this.content.getRef() & binary.BITS5) |
+      (origin === null ? 0 : binary.BIT8) | // origin is defined
+      (rightOrigin === null ? 0 : binary.BIT7) | // right origin is defined
+      (parentSub === null ? 0 : binary.BIT6) // parentSub is non-null
+    encoding.writeUint8(encoder, info)
+    if (origin !== null) {
+      writeID(encoder, origin)
+    }
+    if (rightOrigin !== null) {
+      writeID(encoder, rightOrigin)
+    }
+    if (origin === null && rightOrigin === null) {
+      const parent = /** @type {AbstractType<any>} */ (this.parent)
+      const parentItem = parent._item
+      if (parentItem === null) {
+        // parent type on y._map
+        // find the correct key
+        const ykey = findRootTypeKey(parent)
+        encoding.writeVarUint(encoder, 1) // write parentYKey
+        encoding.writeVarString(encoder, ykey)
+      } else {
+        encoding.writeVarUint(encoder, 0) // write parent id
+        writeID(encoder, parentItem.id)
+      }
+      if (parentSub !== null) {
+        encoding.writeVarString(encoder, parentSub)
+      }
+    }
+    this.content.write(encoder, offset)
+  }
+}
+
+/**
+ * @param {decoding.Decoder} decoder
+ * @param {number} info
+ */
+const readItemContent = (decoder, info) => contentRefs[info & binary.BITS5](decoder)
+
+/**
+ * A lookup map for reading Item content.
+ *
+ * @type {Array<function(decoding.Decoder):AbstractContent>}
+ */
+export const contentRefs = [
+  () => { throw error.unexpectedCase() }, // GC is not ItemContent
+  readContentDeleted,
+  readContentJSON,
+  readContentBinary,
+  readContentString,
+  readContentEmbed,
+  readContentFormat,
+  readContentType,
+  readContentAny
+]
+
+/**
+ * Do not implement this class!
+ */
+export class AbstractContent {
+  /**
+   * @return {number}
+   */
+  getLength () {
+    throw error.methodUnimplemented()
+  }
+
+  /**
+   * @return {Array<any>}
+   */
+  getContent () {
+    throw error.methodUnimplemented()
+  }
+
+  /**
+   * Should return false if this Item is some kind of meta information
+   * (e.g. format information).
+   *
+   * * Whether this Item should be addressable via `yarray.get(i)`
+   * * Whether this Item should be counted when computing yarray.length
+   *
+   * @return {boolean}
+   */
+  isCountable () {
+    throw error.methodUnimplemented()
+  }
+
+  /**
+   * @return {AbstractContent}
+   */
+  copy () {
+    throw error.methodUnimplemented()
+  }
+
+  /**
+   * @param {number} offset
+   * @return {AbstractContent}
+   */
+  splice (offset) {
+    throw error.methodUnimplemented()
+  }
+
+  /**
+   * @param {AbstractContent} right
+   * @return {boolean}
+   */
+  mergeWith (right) {
+    throw error.methodUnimplemented()
+  }
+
+  /**
+   * @param {Transaction} transaction
+   * @param {Item} item
+   */
+  integrate (transaction, item) {
+    throw error.methodUnimplemented()
+  }
+
+  /**
+   * @param {Transaction} transaction
+   */
+  delete (transaction) {
+    throw error.methodUnimplemented()
+  }
+
+  /**
+   * @param {StructStore} store
+   */
+  gc (store) {
+    throw error.methodUnimplemented()
+  }
+
+  /**
+   * @param {encoding.Encoder} encoder
+   * @param {number} offset
+   */
+  write (encoder, offset) {
+    throw error.methodUnimplemented()
+  }
+
+  /**
+   * @return {number}
+   */
+  getRef () {
+    throw error.methodUnimplemented()
+  }
+}
+
+/**
+ * @param {decoding.Decoder} decoder
+ * @param {ID} id
+ * @param {number} info
+ * @param {Doc} doc
+ */
+export const readItem = (decoder, id, info, doc) => {
+  /**
+   * The item that was originally to the left of this item.
+   * @type {ID | null}
+   */
+  const origin = (info & binary.BIT8) === binary.BIT8 ? readID(decoder) : null
+  /**
+   * The item that was originally to the right of this item.
+   * @type {ID | null}
+   */
+  const rightOrigin = (info & binary.BIT7) === binary.BIT7 ? readID(decoder) : null
+  const canCopyParentInfo = (info & (binary.BIT7 | binary.BIT8)) === 0
+  const hasParentYKey = canCopyParentInfo ? decoding.readVarUint(decoder) === 1 : false
+  /**
+   * If parent = null and neither left nor right are defined, then we know that `parent` is child of `y`
+   * and we read the next string as parentYKey.
+   * It indicates how we store/retrieve parent from `y.share`
+   * @type {string|null}
+   */
+  const parentYKey = canCopyParentInfo && hasParentYKey ? decoding.readVarString(decoder) : null
+
+  return new Item(
+    id, null, origin, null, rightOrigin,
+    canCopyParentInfo && !hasParentYKey ? readID(decoder) : (parentYKey ? doc.get(parentYKey) : null), // parent
+    canCopyParentInfo && (info & binary.BIT6) === binary.BIT6 ? decoding.readVarString(decoder) : null, // parentSub
+    /** @type {AbstractContent} */ (readItemContent(decoder, info)) // item content
+  )
+}
--- a/src/types/AbstractType.js
+++ b/src/types/AbstractType.js
@@ -0,0 +1,613 @@
+
+import {
+  removeEventHandlerListener,
+  callEventHandlerListeners,
+  addEventHandlerListener,
+  createEventHandler,
+  getState,
+  isVisible,
+  ContentType,
+  createID,
+  ContentAny,
+  ContentBinary,
+  getItemCleanStart,
+  ID, Doc, Snapshot, Transaction, EventHandler, YEvent, Item, // eslint-disable-line
+} from '../internals.js'
+
+import * as map from 'lib0/map.js'
+import * as iterator from 'lib0/iterator.js'
+import * as error from 'lib0/error.js'
+import * as encoding from 'lib0/encoding.js' // eslint-disable-line
+
+/**
+ * Accumulate all (list) children of a type and return them as an Array.
+ *
+ * @param {AbstractType<any>} t
+ * @return {Array<Item>}
+ */
+export const getTypeChildren = t => {
+  let s = t._start
+  const arr = []
+  while (s) {
+    arr.push(s)
+    s = s.right
+  }
+  return arr
+}
+
+/**
+ * Call event listeners with an event. This will also add an event to all
+ * parents (for `.observeDeep` handlers).
+ *
+ * @template EventType
+ * @param {AbstractType<EventType>} type
+ * @param {Transaction} transaction
+ * @param {EventType} event
+ */
+export const callTypeObservers = (type, transaction, event) => {
+  const changedType = type
+  const changedParentTypes = transaction.changedParentTypes
+  while (true) {
+    // @ts-ignore
+    map.setIfUndefined(changedParentTypes, type, () => []).push(event)
+    if (type._item === null) {
+      break
+    }
+    type = /** @type {AbstractType<any>} */ (type._item.parent)
+  }
+  callEventHandlerListeners(changedType._eH, event, transaction)
+}
+
+/**
+ * @template EventType
+ * Abstract Yjs Type class
+ */
+export class AbstractType {
+  constructor () {
+    /**
+     * @type {Item|null}
+     */
+    this._item = null
+    /**
+     * @type {Map<string,Item>}
+     */
+    this._map = new Map()
+    /**
+     * @type {Item|null}
+     */
+    this._start = null
+    /**
+     * @type {Doc|null}
+     */
+    this.doc = null
+    this._length = 0
+    /**
+     * Event handlers
+     * @type {EventHandler<EventType,Transaction>}
+     */
+    this._eH = createEventHandler()
+    /**
+     * Deep event handlers
+     * @type {EventHandler<Array<YEvent>,Transaction>}
+     */
+    this._dEH = createEventHandler()
+  }
+
+  /**
+   * Integrate this type into the Yjs instance.
+   *
+   * * Save this struct in the os
+   * * This type is sent to other client
+   * * Observer functions are fired
+   *
+   * @param {Doc} y The Yjs instance
+   * @param {Item|null} item
+   */
+  _integrate (y, item) {
+    this.doc = y
+    this._item = item
+  }
+
+  /**
+   * @return {AbstractType<EventType>}
+   */
+  _copy () {
+    throw error.methodUnimplemented()
+  }
+
+  /**
+   * @param {encoding.Encoder} encoder
+   */
+  _write (encoder) { }
+
+  /**
+   * The first non-deleted item
+   */
+  get _first () {
+    let n = this._start
+    while (n !== null && n.deleted) {
+      n = n.right
+    }
+    return n
+  }
+
+  /**
+   * Creates YEvent and calls all type observers.
+   * Must be implemented by each type.
+   *
+   * @param {Transaction} transaction
+   * @param {Set<null|string>} parentSubs Keys changed on this type. `null` if list was modified.
+   */
+  _callObserver (transaction, parentSubs) { /* skip if no type is specified */ }
+
+  /**
+   * Observe all events that are created on this type.
+   *
+   * @param {function(EventType, Transaction):void} f Observer function
+   */
+  observe (f) {
+    addEventHandlerListener(this._eH, f)
+  }
+
+  /**
+   * Observe all events that are created by this type and its children.
+   *
+   * @param {function(Array<YEvent>,Transaction):void} f Observer function
+   */
+  observeDeep (f) {
+    addEventHandlerListener(this._dEH, f)
+  }
+
+  /**
+   * Unregister an observer function.
+   *
+   * @param {function(EventType,Transaction):void} f Observer function
+   */
+  unobserve (f) {
+    removeEventHandlerListener(this._eH, f)
+  }
+
+  /**
+   * Unregister an observer function.
+   *
+   * @param {function(Array<YEvent>,Transaction):void} f Observer function
+   */
+  unobserveDeep (f) {
+    removeEventHandlerListener(this._dEH, f)
+  }
+
+  /**
+   * @abstract
+   * @return {any}
+   */
+  toJSON () {}
+}
+
+/**
+ * @param {AbstractType<any>} type
+ * @return {Array<any>}
+ *
+ * @private
+ * @function
+ */
+export const typeListToArray = type => {
+  const cs = []
+  let n = type._start
+  while (n !== null) {
+    if (n.countable && !n.deleted) {
+      const c = n.content.getContent()
+      for (let i = 0; i < c.length; i++) {
+        cs.push(c[i])
+      }
+    }
+    n = n.right
+  }
+  return cs
+}
+
+/**
+ * @param {AbstractType<any>} type
+ * @param {Snapshot} snapshot
+ * @return {Array<any>}
+ *
+ * @private
+ * @function
+ */
+export const typeListToArraySnapshot = (type, snapshot) => {
+  const cs = []
+  let n = type._start
+  while (n !== null) {
+    if (n.countable && isVisible(n, snapshot)) {
+      const c = n.content.getContent()
+      for (let i = 0; i < c.length; i++) {
+        cs.push(c[i])
+      }
+    }
+    n = n.right
+  }
+  return cs
+}
+
+/**
+ * Executes a provided function on once on overy element of this YArray.
+ *
+ * @param {AbstractType<any>} type
+ * @param {function(any,number,any):void} f A function to execute on every element of this YArray.
+ *
+ * @private
+ * @function
+ */
+export const typeListForEach = (type, f) => {
+  let index = 0
+  let n = type._start
+  while (n !== null) {
+    if (n.countable && !n.deleted) {
+      const c = n.content.getContent()
+      for (let i = 0; i < c.length; i++) {
+        f(c[i], index++, type)
+      }
+    }
+    n = n.right
+  }
+}
+
+/**
+ * @template C,R
+ * @param {AbstractType<any>} type
+ * @param {function(C,number,AbstractType<any>):R} f
+ * @return {Array<R>}
+ *
+ * @private
+ * @function
+ */
+export const typeListMap = (type, f) => {
+  /**
+   * @type {Array<any>}
+   */
+  const result = []
+  typeListForEach(type, (c, i) => {
+    result.push(f(c, i, type))
+  })
+  return result
+}
+
+/**
+ * @param {AbstractType<any>} type
+ * @return {IterableIterator<any>}
+ *
+ * @private
+ * @function
+ */
+export const typeListCreateIterator = type => {
+  let n = type._start
+  /**
+   * @type {Array<any>|null}
+   */
+  let currentContent = null
+  let currentContentIndex = 0
+  return {
+    [Symbol.iterator] () {
+      return this
+    },
+    next: () => {
+      // find some content
+      if (currentContent === null) {
+        while (n !== null && n.deleted) {
+          n = n.right
+        }
+        // check if we reached the end, no need to check currentContent, because it does not exist
+        if (n === null) {
+          return {
+            done: true,
+            value: undefined
+          }
+        }
+        // we found n, so we can set currentContent
+        currentContent = n.content.getContent()
+        currentContentIndex = 0
+        n = n.right // we used the content of n, now iterate to next
+      }
+      const value = currentContent[currentContentIndex++]
+      // check if we need to empty currentContent
+      if (currentContent.length <= currentContentIndex) {
+        currentContent = null
+      }
+      return {
+        done: false,
+        value
+      }
+    }
+  }
+}
+
+/**
+ * Executes a provided function on once on overy element of this YArray.
+ * Operates on a snapshotted state of the document.
+ *
+ * @param {AbstractType<any>} type
+ * @param {function(any,number,AbstractType<any>):void} f A function to execute on every element of this YArray.
+ * @param {Snapshot} snapshot
+ *
+ * @private
+ * @function
+ */
+export const typeListForEachSnapshot = (type, f, snapshot) => {
+  let index = 0
+  let n = type._start
+  while (n !== null) {
+    if (n.countable && isVisible(n, snapshot)) {
+      const c = n.content.getContent()
+      for (let i = 0; i < c.length; i++) {
+        f(c[i], index++, type)
+      }
+    }
+    n = n.right
+  }
+}
+
+/**
+ * @param {AbstractType<any>} type
+ * @param {number} index
+ * @return {any}
+ *
+ * @private
+ * @function
+ */
+export const typeListGet = (type, index) => {
+  for (let n = type._start; n !== null; n = n.right) {
+    if (!n.deleted && n.countable) {
+      if (index < n.length) {
+        return n.content.getContent()[index]
+      }
+      index -= n.length
+    }
+  }
+}
+
+/**
+ * @param {Transaction} transaction
+ * @param {AbstractType<any>} parent
+ * @param {Item?} referenceItem
+ * @param {Array<Object<string,any>|Array<any>|boolean|number|string|Uint8Array>} content
+ *
+ * @private
+ * @function
+ */
+export const typeListInsertGenericsAfter = (transaction, parent, referenceItem, content) => {
+  let left = referenceItem
+  const doc = transaction.doc
+  const ownClientId = doc.clientID
+  const store = doc.store
+  const right = referenceItem === null ? parent._start : referenceItem.right
+  /**
+   * @type {Array<Object|Array<any>|number>}
+   */
+  let jsonContent = []
+  const packJsonContent = () => {
+    if (jsonContent.length > 0) {
+      left = new Item(createID(ownClientId, getState(store, ownClientId)), left, left && left.lastId, right, right && right.id, parent, null, new ContentAny(jsonContent))
+      left.integrate(transaction, 0)
+      jsonContent = []
+    }
+  }
+  content.forEach(c => {
+    switch (c.constructor) {
+      case Number:
+      case Object:
+      case Boolean:
+      case Array:
+      case String:
+        jsonContent.push(c)
+        break
+      default:
+        packJsonContent()
+        switch (c.constructor) {
+          case Uint8Array:
+          case ArrayBuffer:
+            left = new Item(createID(ownClientId, getState(store, ownClientId)), left, left && left.lastId, right, right && right.id, parent, null, new ContentBinary(new Uint8Array(/** @type {Uint8Array} */ (c))))
+            left.integrate(transaction, 0)
+            break
+          default:
+            if (c instanceof AbstractType) {
+              left = new Item(createID(ownClientId, getState(store, ownClientId)), left, left && left.lastId, right, right && right.id, parent, null, new ContentType(c))
+              left.integrate(transaction, 0)
+            } else {
+              throw new Error('Unexpected content type in insert operation')
+            }
+        }
+    }
+  })
+  packJsonContent()
+}
+
+/**
+ * @param {Transaction} transaction
+ * @param {AbstractType<any>} parent
+ * @param {number} index
+ * @param {Array<Object<string,any>|Array<any>|number|string|Uint8Array>} content
+ *
+ * @private
+ * @function
+ */
+export const typeListInsertGenerics = (transaction, parent, index, content) => {
+  if (index === 0) {
+    return typeListInsertGenericsAfter(transaction, parent, null, content)
+  }
+  let n = parent._start
+  for (; n !== null; n = n.right) {
+    if (!n.deleted && n.countable) {
+      if (index <= n.length) {
+        if (index < n.length) {
+          // insert in-between
+          getItemCleanStart(transaction, createID(n.id.client, n.id.clock + index))
+        }
+        break
+      }
+      index -= n.length
+    }
+  }
+  return typeListInsertGenericsAfter(transaction, parent, n, content)
+}
+
+/**
+ * @param {Transaction} transaction
+ * @param {AbstractType<any>} parent
+ * @param {number} index
+ * @param {number} length
+ *
+ * @private
+ * @function
+ */
+export const typeListDelete = (transaction, parent, index, length) => {
+  if (length === 0) { return }
+  let n = parent._start
+  // compute the first item to be deleted
+  for (; n !== null && index > 0; n = n.right) {
+    if (!n.deleted && n.countable) {
+      if (index < n.length) {
+        getItemCleanStart(transaction, createID(n.id.client, n.id.clock + index))
+      }
+      index -= n.length
+    }
+  }
+  // delete all items until done
+  while (length > 0 && n !== null) {
+    if (!n.deleted) {
+      if (length < n.length) {
+        getItemCleanStart(transaction, createID(n.id.client, n.id.clock + length))
+      }
+      n.delete(transaction)
+      length -= n.length
+    }
+    n = n.right
+  }
+  if (length > 0) {
+    throw error.create('array length exceeded')
+  }
+}
+
+/**
+ * @param {Transaction} transaction
+ * @param {AbstractType<any>} parent
+ * @param {string} key
+ *
+ * @private
+ * @function
+ */
+export const typeMapDelete = (transaction, parent, key) => {
+  const c = parent._map.get(key)
+  if (c !== undefined) {
+    c.delete(transaction)
+  }
+}
+
+/**
+ * @param {Transaction} transaction
+ * @param {AbstractType<any>} parent
+ * @param {string} key
+ * @param {Object|number|Array<any>|string|Uint8Array|AbstractType<any>} value
+ *
+ * @private
+ * @function
+ */
+export const typeMapSet = (transaction, parent, key, value) => {
+  const left = parent._map.get(key) || null
+  const doc = transaction.doc
+  const ownClientId = doc.clientID
+  let content
+  if (value == null) {
+    content = new ContentAny([value])
+  } else {
+    switch (value.constructor) {
+      case Number:
+      case Object:
+      case Boolean:
+      case Array:
+      case String:
+        content = new ContentAny([value])
+        break
+      case Uint8Array:
+        content = new ContentBinary(/** @type {Uint8Array} */ (value))
+        break
+      default:
+        if (value instanceof AbstractType) {
+          content = new ContentType(value)
+        } else {
+          throw new Error('Unexpected content type')
+        }
+    }
+  }
+  new Item(createID(ownClientId, getState(doc.store, ownClientId)), left, left && left.lastId, null, null, parent, key, content).integrate(transaction, 0)
+}
+
+/**
+ * @param {AbstractType<any>} parent
+ * @param {string} key
+ * @return {Object<string,any>|number|Array<any>|string|Uint8Array|AbstractType<any>|undefined}
+ *
+ * @private
+ * @function
+ */
+export const typeMapGet = (parent, key) => {
+  const val = parent._map.get(key)
+  return val !== undefined && !val.deleted ? val.content.getContent()[val.length - 1] : undefined
+}
+
+/**
+ * @param {AbstractType<any>} parent
+ * @return {Object<string,Object<string,any>|number|Array<any>|string|Uint8Array|AbstractType<any>|undefined>}
+ *
+ * @private
+ * @function
+ */
+export const typeMapGetAll = (parent) => {
+  /**
+   * @type {Object<string,any>}
+   */
+  const res = {}
+  for (const [key, value] of parent._map) {
+    if (!value.deleted) {
+      res[key] = value.content.getContent()[value.length - 1]
+    }
+  }
+  return res
+}
+
+/**
+ * @param {AbstractType<any>} parent
+ * @param {string} key
+ * @return {boolean}
+ *
+ * @private
+ * @function
+ */
+export const typeMapHas = (parent, key) => {
+  const val = parent._map.get(key)
+  return val !== undefined && !val.deleted
+}
+
+/**
+ * @param {AbstractType<any>} parent
+ * @param {string} key
+ * @param {Snapshot} snapshot
+ * @return {Object<string,any>|number|Array<any>|string|Uint8Array|AbstractType<any>|undefined}
+ *
+ * @private
+ * @function
+ */
+export const typeMapGetSnapshot = (parent, key, snapshot) => {
+  let v = parent._map.get(key) || null
+  while (v !== null && (!snapshot.sv.has(v.id.client) || v.id.clock >= (snapshot.sv.get(v.id.client) || 0))) {
+    v = v.left
+  }
+  return v !== null && isVisible(v, snapshot) ? v.content.getContent()[v.length - 1] : undefined
+}
+
+/**
+ * @param {Map<string,Item>} map
+ * @return {IterableIterator<Array<any>>}
+ *
+ * @private
+ * @function
+ */
+export const createMapIterator = map => iterator.iteratorFilter(map.entries(), /** @param {any} entry */ entry => !entry[1].deleted)
--- a/src/types/YArray.js
+++ b/src/types/YArray.js
@@ -0,0 +1,220 @@
+/**
+ * @module YArray
+ */
+
+import {
+  YEvent,
+  AbstractType,
+  typeListGet,
+  typeListToArray,
+  typeListForEach,
+  typeListCreateIterator,
+  typeListInsertGenerics,
+  typeListDelete,
+  typeListMap,
+  YArrayRefID,
+  callTypeObservers,
+  transact,
+  Doc, Transaction, Item // eslint-disable-line
+} from '../internals.js'
+
+import * as decoding from 'lib0/decoding.js' // eslint-disable-line
+import * as encoding from 'lib0/encoding.js'
+
+/**
+ * Event that describes the changes on a YArray
+ * @template T
+ */
+export class YArrayEvent extends YEvent {
+  /**
+   * @param {YArray<T>} yarray The changed type
+   * @param {Transaction} transaction The transaction object
+   */
+  constructor (yarray, transaction) {
+    super(yarray, transaction)
+    this._transaction = transaction
+  }
+}
+
+/**
+ * A shared Array implementation.
+ * @template T
+ * @extends AbstractType<YArrayEvent<T>>
+ * @implements {Iterable<T>}
+ */
+export class YArray extends AbstractType {
+  constructor () {
+    super()
+    /**
+     * @type {Array<any>?}
+     * @private
+     */
+    this._prelimContent = []
+  }
+
+  /**
+   * Integrate this type into the Yjs instance.
+   *
+   * * Save this struct in the os
+   * * This type is sent to other client
+   * * Observer functions are fired
+   *
+   * @param {Doc} y The Yjs instance
+   * @param {Item} item
+   */
+  _integrate (y, item) {
+    super._integrate(y, item)
+    this.insert(0, /** @type {Array<any>} */ (this._prelimContent))
+    this._prelimContent = null
+  }
+
+  _copy () {
+    return new YArray()
+  }
+
+  get length () {
+    return this._prelimContent === null ? this._length : this._prelimContent.length
+  }
+
+  /**
+   * Creates YArrayEvent and calls observers.
+   *
+   * @param {Transaction} transaction
+   * @param {Set<null|string>} parentSubs Keys changed on this type. `null` if list was modified.
+   */
+  _callObserver (transaction, parentSubs) {
+    callTypeObservers(this, transaction, new YArrayEvent(this, transaction))
+  }
+
+  /**
+   * Inserts new content at an index.
+   *
+   * Important: This function expects an array of content. Not just a content
+   * object. The reason for this "weirdness" is that inserting several elements
+   * is very efficient when it is done as a single operation.
+   *
+   * @example
+   *  // Insert character 'a' at position 0
+   *  yarray.insert(0, ['a'])
+   *  // Insert numbers 1, 2 at position 1
+   *  yarray.insert(1, [1, 2])
+   *
+   * @param {number} index The index to insert content at.
+   * @param {Array<T>} content The array of content
+   */
+  insert (index, content) {
+    if (this.doc !== null) {
+      transact(this.doc, transaction => {
+        typeListInsertGenerics(transaction, this, index, content)
+      })
+    } else {
+      /** @type {Array<any>} */ (this._prelimContent).splice(index, 0, ...content)
+    }
+  }
+
+  /**
+   * Appends content to this YArray.
+   *
+   * @param {Array<T>} content Array of content to append.
+   */
+  push (content) {
+    this.insert(this.length, content)
+  }
+
+  /**
+   * Preppends content to this YArray.
+   *
+   * @param {Array<T>} content Array of content to preppend.
+   */
+  unshift (content) {
+    this.insert(0, content)
+  }
+
+  /**
+   * Deletes elements starting from an index.
+   *
+   * @param {number} index Index at which to start deleting elements
+   * @param {number} length The number of elements to remove. Defaults to 1.
+   */
+  delete (index, length = 1) {
+    if (this.doc !== null) {
+      transact(this.doc, transaction => {
+        typeListDelete(transaction, this, index, length)
+      })
+    } else {
+      /** @type {Array<any>} */ (this._prelimContent).splice(index, length)
+    }
+  }
+
+  /**
+   * Returns the i-th element from a YArray.
+   *
+   * @param {number} index The index of the element to return from the YArray
+   * @return {T}
+   */
+  get (index) {
+    return typeListGet(this, index)
+  }
+
+  /**
+   * Transforms this YArray to a JavaScript Array.
+   *
+   * @return {Array<T>}
+   */
+  toArray () {
+    return typeListToArray(this)
+  }
+
+  /**
+   * Transforms this Shared Type to a JSON object.
+   *
+   * @return {Array<any>}
+   */
+  toJSON () {
+    return this.map(c => c instanceof AbstractType ? c.toJSON() : c)
+  }
+
+  /**
+   * Returns an Array with the result of calling a provided function on every
+   * element of this YArray.
+   *
+   * @template T,M
+   * @param {function(T,number,YArray<T>):M} f Function that produces an element of the new Array
+   * @return {Array<M>} A new array with each element being the result of the
+   *                 callback function
+   */
+  map (f) {
+    return typeListMap(this, /** @type {any} */ (f))
+  }
+
+  /**
+   * Executes a provided function on once on overy element of this YArray.
+   *
+   * @param {function(T,number,YArray<T>):void} f A function to execute on every element of this YArray.
+   */
+  forEach (f) {
+    typeListForEach(this, f)
+  }
+
+  /**
+   * @return {IterableIterator<T>}
+   */
+  [Symbol.iterator] () {
+    return typeListCreateIterator(this)
+  }
+
+  /**
+   * @param {encoding.Encoder} encoder
+   */
+  _write (encoder) {
+    encoding.writeVarUint(encoder, YArrayRefID)
+  }
+}
+
+/**
+ * @param {decoding.Decoder} decoder
+ *
+ * @private
+ * @function
+ */
+export const readYArray = decoder => new YArray()
--- a/src/types/YMap.js
+++ b/src/types/YMap.js
@@ -0,0 +1,245 @@
+
+/**
+ * @module YMap
+ */
+
+import {
+  YEvent,
+  AbstractType,
+  typeMapDelete,
+  typeMapSet,
+  typeMapGet,
+  typeMapHas,
+  createMapIterator,
+  YMapRefID,
+  callTypeObservers,
+  transact,
+  Doc, Transaction, Item // eslint-disable-line
+} from '../internals.js'
+
+import * as encoding from 'lib0/encoding.js'
+import * as decoding from 'lib0/decoding.js' // eslint-disable-line
+import * as iterator from 'lib0/iterator.js'
+
+/**
+ * @template T
+ * Event that describes the changes on a YMap.
+ */
+export class YMapEvent extends YEvent {
+  /**
+   * @param {YMap<T>} ymap The YArray that changed.
+   * @param {Transaction} transaction
+   * @param {Set<any>} subs The keys that changed.
+   */
+  constructor (ymap, transaction, subs) {
+    super(ymap, transaction)
+    this.keysChanged = subs
+  }
+}
+
+/**
+ * @template T number|string|Object|Array|Uint8Array
+ * A shared Map implementation.
+ *
+ * @extends AbstractType<YMapEvent<T>>
+ * @implements {Iterable<T>}
+ */
+export class YMap extends AbstractType {
+  /**
+   *
+   * @param {Iterable<readonly [string, any]>=} entries - an optional iterable to initialize the YMap
+   */
+  constructor (entries) {
+    super()
+    /**
+     * @type {Map<string,any>?}
+     * @private
+     */
+    this._prelimContent = null
+
+    if (entries === undefined) {
+      this._prelimContent = new Map()
+    } else {
+      this._prelimContent = new Map(entries)
+    }
+  }
+
+  /**
+   * Integrate this type into the Yjs instance.
+   *
+   * * Save this struct in the os
+   * * This type is sent to other client
+   * * Observer functions are fired
+   *
+   * @param {Doc} y The Yjs instance
+   * @param {Item} item
+   */
+  _integrate (y, item) {
+    super._integrate(y, item)
+    for (const [key, value] of /** @type {Map<string, any>} */ (this._prelimContent)) {
+      this.set(key, value)
+    }
+    this._prelimContent = null
+  }
+
+  _copy () {
+    return new YMap()
+  }
+
+  /**
+   * Creates YMapEvent and calls observers.
+   *
+   * @param {Transaction} transaction
+   * @param {Set<null|string>} parentSubs Keys changed on this type. `null` if list was modified.
+   */
+  _callObserver (transaction, parentSubs) {
+    callTypeObservers(this, transaction, new YMapEvent(this, transaction, parentSubs))
+  }
+
+  /**
+   * Transforms this Shared Type to a JSON object.
+   *
+   * @return {Object<string,T>}
+   */
+  toJSON () {
+    /**
+     * @type {Object<string,T>}
+     */
+    const map = {}
+    for (const [key, item] of this._map) {
+      if (!item.deleted) {
+        const v = item.content.getContent()[item.length - 1]
+        map[key] = v instanceof AbstractType ? v.toJSON() : v
+      }
+    }
+    return map
+  }
+
+  /**
+   * Returns the size of the YMap (count of key/value pairs)
+   *
+   * @return {number}
+   */
+  get size () {
+    return [...createMapIterator(this._map)].length
+  }
+
+  /**
+   * Returns the keys for each element in the YMap Type.
+   *
+   * @return {IterableIterator<string>}
+   */
+  keys () {
+    return iterator.iteratorMap(createMapIterator(this._map), /** @param {any} v */ v => v[0])
+  }
+
+  /**
+   * Returns the keys for each element in the YMap Type.
+   *
+   * @return {IterableIterator<string>}
+   */
+  values () {
+    return iterator.iteratorMap(createMapIterator(this._map), /** @param {any} v */ v => v[1].content.getContent()[v[1].length - 1])
+  }
+
+  /**
+   * Returns an Iterator of [key, value] pairs
+   *
+   * @return {IterableIterator<any>}
+   */
+  entries () {
+    return iterator.iteratorMap(createMapIterator(this._map), /** @param {any} v */ v => [v[0], v[1].content.getContent()[v[1].length - 1]])
+  }
+
+  /**
+   * Executes a provided function on once on every key-value pair.
+   *
+   * @param {function(T,string,YMap<T>):void} f A function to execute on every element of this YArray.
+   */
+  forEach (f) {
+    /**
+     * @type {Object<string,T>}
+     */
+    const map = {}
+    for (const [key, item] of this._map) {
+      if (!item.deleted) {
+        f(item.content.getContent()[item.length - 1], key, this)
+      }
+    }
+    return map
+  }
+
+  /**
+   * @return {IterableIterator<T>}
+   */
+  [Symbol.iterator] () {
+    return this.entries()
+  }
+
+  /**
+   * Remove a specified element from this YMap.
+   *
+   * @param {string} key The key of the element to remove.
+   */
+  delete (key) {
+    if (this.doc !== null) {
+      transact(this.doc, transaction => {
+        typeMapDelete(transaction, this, key)
+      })
+    } else {
+      /** @type {Map<string, any>} */ (this._prelimContent).delete(key)
+    }
+  }
+
+  /**
+   * Adds or updates an element with a specified key and value.
+   *
+   * @param {string} key The key of the element to add to this YMap
+   * @param {T} value The value of the element to add
+   */
+  set (key, value) {
+    if (this.doc !== null) {
+      transact(this.doc, transaction => {
+        typeMapSet(transaction, this, key, value)
+      })
+    } else {
+      /** @type {Map<string, any>} */ (this._prelimContent).set(key, value)
+    }
+    return value
+  }
+
+  /**
+   * Returns a specified element from this YMap.
+   *
+   * @param {string} key
+   * @return {T|undefined}
+   */
+  get (key) {
+    return /** @type {any} */ (typeMapGet(this, key))
+  }
+
+  /**
+   * Returns a boolean indicating whether the specified key exists or not.
+   *
+   * @param {string} key The key to test.
+   * @return {boolean}
+   */
+  has (key) {
+    return typeMapHas(this, key)
+  }
+
+  /**
+   * @param {encoding.Encoder} encoder
+   */
+  _write (encoder) {
+    encoding.writeVarUint(encoder, YMapRefID)
+  }
+}
+
+/**
+ * @param {decoding.Decoder} decoder
+ *
+ * @private
+ * @function
+ */
+export const readYMap = decoder => new YMap()
--- a/src/types/YText.js
+++ b/src/types/YText.js
--- a/src/types/YXmlElement.js
+++ b/src/types/YXmlElement.js
@@ -0,0 +1,198 @@
+
+import {
+  YXmlFragment,
+  transact,
+  typeMapDelete,
+  typeMapSet,
+  typeMapGet,
+  typeMapGetAll,
+  typeListForEach,
+  YXmlElementRefID,
+  Snapshot, Doc, Item // eslint-disable-line
+} from '../internals.js'
+
+import * as encoding from 'lib0/encoding.js'
+import * as decoding from 'lib0/decoding.js'
+
+/**
+ * An YXmlElement imitates the behavior of a
+ * {@link https://developer.mozilla.org/en-US/docs/Web/API/Element|Dom Element}.
+ *
+ * * An YXmlElement has attributes (key value pairs)
+ * * An YXmlElement has childElements that must inherit from YXmlElement
+ */
+export class YXmlElement extends YXmlFragment {
+  constructor (nodeName = 'UNDEFINED') {
+    super()
+    this.nodeName = nodeName
+    /**
+     * @type {Map<string, any>|null}
+     */
+    this._prelimAttrs = new Map()
+  }
+
+  /**
+   * Integrate this type into the Yjs instance.
+   *
+   * * Save this struct in the os
+   * * This type is sent to other client
+   * * Observer functions are fired
+   *
+   * @param {Doc} y The Yjs instance
+   * @param {Item} item
+   */
+  _integrate (y, item) {
+    super._integrate(y, item)
+    ;(/** @type {Map<string, any>} */ (this._prelimAttrs)).forEach((value, key) => {
+      this.setAttribute(key, value)
+    })
+    this._prelimAttrs = null
+  }
+
+  /**
+   * Creates an Item with the same effect as this Item (without position effect)
+   *
+   * @return {YXmlElement}
+   */
+  _copy () {
+    return new YXmlElement(this.nodeName)
+  }
+
+  /**
+   * Returns the XML serialization of this YXmlElement.
+   * The attributes are ordered by attribute-name, so you can easily use this
+   * method to compare YXmlElements
+   *
+   * @return {string} The string representation of this type.
+   *
+   * @public
+   */
+  toString () {
+    const attrs = this.getAttributes()
+    const stringBuilder = []
+    const keys = []
+    for (const key in attrs) {
+      keys.push(key)
+    }
+    keys.sort()
+    const keysLen = keys.length
+    for (let i = 0; i < keysLen; i++) {
+      const key = keys[i]
+      stringBuilder.push(key + '="' + attrs[key] + '"')
+    }
+    const nodeName = this.nodeName.toLocaleLowerCase()
+    const attrsString = stringBuilder.length > 0 ? ' ' + stringBuilder.join(' ') : ''
+    return `<${nodeName}${attrsString}>${super.toString()}</${nodeName}>`
+  }
+
+  /**
+   * Removes an attribute from this YXmlElement.
+   *
+   * @param {String} attributeName The attribute name that is to be removed.
+   *
+   * @public
+   */
+  removeAttribute (attributeName) {
+    if (this.doc !== null) {
+      transact(this.doc, transaction => {
+        typeMapDelete(transaction, this, attributeName)
+      })
+    } else {
+      /** @type {Map<string,any>} */ (this._prelimAttrs).delete(attributeName)
+    }
+  }
+
+  /**
+   * Sets or updates an attribute.
+   *
+   * @param {String} attributeName The attribute name that is to be set.
+   * @param {String} attributeValue The attribute value that is to be set.
+   *
+   * @public
+   */
+  setAttribute (attributeName, attributeValue) {
+    if (this.doc !== null) {
+      transact(this.doc, transaction => {
+        typeMapSet(transaction, this, attributeName, attributeValue)
+      })
+    } else {
+      /** @type {Map<string, any>} */ (this._prelimAttrs).set(attributeName, attributeValue)
+    }
+  }
+
+  /**
+   * Returns an attribute value that belongs to the attribute name.
+   *
+   * @param {String} attributeName The attribute name that identifies the
+   *                               queried value.
+   * @return {String} The queried attribute value.
+   *
+   * @public
+   */
+  getAttribute (attributeName) {
+    return /** @type {any} */ (typeMapGet(this, attributeName))
+  }
+
+  /**
+   * Returns all attribute name/value pairs in a JSON Object.
+   *
+   * @param {Snapshot} [snapshot]
+   * @return {Object<string, any>} A JSON Object that describes the attributes.
+   *
+   * @public
+   */
+  getAttributes (snapshot) {
+    return typeMapGetAll(this)
+  }
+
+  /**
+   * Creates a Dom Element that mirrors this YXmlElement.
+   *
+   * @param {Document} [_document=document] The document object (you must define
+   *                                        this when calling this method in
+   *                                        nodejs)
+   * @param {Object<string, any>} [hooks={}] Optional property to customize how hooks
+   *                                             are presented in the DOM
+   * @param {any} [binding] You should not set this property. This is
+   *                               used if DomBinding wants to create a
+   *                               association to the created DOM type.
+   * @return {Node} The {@link https://developer.mozilla.org/en-US/docs/Web/API/Element|Dom Element}
+   *
+   * @public
+   */
+  toDOM (_document = document, hooks = {}, binding) {
+    const dom = _document.createElement(this.nodeName)
+    const attrs = this.getAttributes()
+    for (const key in attrs) {
+      dom.setAttribute(key, attrs[key])
+    }
+    typeListForEach(this, yxml => {
+      dom.appendChild(yxml.toDOM(_document, hooks, binding))
+    })
+    if (binding !== undefined) {
+      binding._createAssociation(dom, this)
+    }
+    return dom
+  }
+
+  /**
+   * Transform the properties of this type to binary and write it to an
+   * BinaryEncoder.
+   *
+   * This is called when this Item is sent to a remote peer.
+   *
+   * @param {encoding.Encoder} encoder The encoder to write data to.
+   */
+  _write (encoder) {
+    encoding.writeVarUint(encoder, YXmlElementRefID)
+    encoding.writeVarString(encoder, this.nodeName)
+  }
+}
+
+/**
+ * @param {decoding.Decoder} decoder
+ * @return {YXmlElement}
+ *
+ * @function
+ */
+export const readYXmlElement = decoder => new YXmlElement(decoding.readVarString(decoder))
--- a/src/types/YXmlEvent.js
+++ b/src/types/YXmlEvent.js
@@ -0,0 +1,39 @@
+
+import {
+  YEvent,
+  YXmlElement, YXmlFragment, Transaction // eslint-disable-line
+} from '../internals.js'
+
+/**
+ * An Event that describes changes on a YXml Element or Yxml Fragment
+ */
+export class YXmlEvent extends YEvent {
+  /**
+   * @param {YXmlElement|YXmlFragment} target The target on which the event is created.
+   * @param {Set<string|null>} subs The set of changed attributes. `null` is included if the
+   *                   child list changed.
+   * @param {Transaction} transaction The transaction instance with wich the
+   *                                  change was created.
+   */
+  constructor (target, subs, transaction) {
+    super(target, transaction)
+    /**
+     * Whether the children changed.
+     * @type {Boolean}
+     * @private
+     */
+    this.childListChanged = false
+    /**
+     * Set of all changed attributes.
+     * @type {Set<string|null>}
+     */
+    this.attributesChanged = new Set()
+    subs.forEach((sub) => {
+      if (sub === null) {
+        this.childListChanged = true
+      } else {
+        this.attributesChanged.add(sub)
+      }
+    })
+  }
+}
--- a/src/types/YXmlFragment.js
+++ b/src/types/YXmlFragment.js
@@ -0,0 +1,342 @@
+/**
+ * @module YXml
+ */
+
+import {
+  YXmlEvent,
+  YXmlElement,
+  AbstractType,
+  typeListMap,
+  typeListForEach,
+  typeListInsertGenerics,
+  typeListDelete,
+  typeListToArray,
+  YXmlFragmentRefID,
+  callTypeObservers,
+  transact,
+  Doc, ContentType, Transaction, Item, YXmlText, YXmlHook, Snapshot // eslint-disable-line
+} from '../internals.js'
+
+import * as encoding from 'lib0/encoding.js'
+import * as decoding from 'lib0/decoding.js' // eslint-disable-line
+
+/**
+ * Define the elements to which a set of CSS queries apply.
+ * {@link https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Selectors|CSS_Selectors}
+ *
+ * @example
+ *   query = '.classSelector'
+ *   query = 'nodeSelector'
+ *   query = '#idSelector'
+ *
+ * @typedef {string} CSS_Selector
+ */
+
+/**
+ * Dom filter function.
+ *
+ * @callback domFilter
+ * @param {string} nodeName The nodeName of the element
+ * @param {Map} attributes The map of attributes.
+ * @return {boolean} Whether to include the Dom node in the YXmlElement.
+ */
+
+/**
+ * Represents a subset of the nodes of a YXmlElement / YXmlFragment and a
+ * position within them.
+ *
+ * Can be created with {@link YXmlFragment#createTreeWalker}
+ *
+ * @public
+ * @implements {Iterable<YXmlElement|YXmlText|YXmlElement|YXmlHook>}
+ */
+export class YXmlTreeWalker {
+  /**
+   * @param {YXmlFragment | YXmlElement} root
+   * @param {function(AbstractType<any>):boolean} [f]
+   */
+  constructor (root, f = () => true) {
+    this._filter = f
+    this._root = root
+    /**
+     * @type {Item}
+     */
+    this._currentNode = /** @type {Item} */ (root._start)
+    this._firstCall = true
+  }
+
+  [Symbol.iterator] () {
+    return this
+  }
+
+  /**
+   * Get the next node.
+   *
+   * @return {IteratorResult<YXmlElement|YXmlText|YXmlHook>} The next node.
+   *
+   * @public
+   */
+  next () {
+    /**
+     * @type {Item|null}
+     */
+    let n = this._currentNode
+    let type = /** @type {any} */ (n.content).type
+    if (n !== null && (!this._firstCall || n.deleted || !this._filter(type))) { // if first call, we check if we can use the first item
+      do {
+        type = /** @type {any} */ (n.content).type
+        if (!n.deleted && (type.constructor === YXmlElement || type.constructor === YXmlFragment) && type._start !== null) {
+          // walk down in the tree
+          n = type._start
+        } else {
+          // walk right or up in the tree
+          while (n !== null) {
+            if (n.right !== null) {
+              n = n.right
+              break
+            } else if (n.parent === this._root) {
+              n = null
+            } else {
+              n = /** @type {AbstractType<any>} */ (n.parent)._item
+            }
+          }
+        }
+      } while (n !== null && (n.deleted || !this._filter(/** @type {ContentType} */ (n.content).type)))
+    }
+    this._firstCall = false
+    if (n === null) {
+      // @ts-ignore
+      return { value: undefined, done: true }
+    }
+    this._currentNode = n
+    return { value: /** @type {any} */ (n.content).type, done: false }
+  }
+}
+
+/**
+ * Represents a list of {@link YXmlElement}.and {@link YXmlText} types.
+ * A YxmlFragment is similar to a {@link YXmlElement}, but it does not have a
+ * nodeName and it does not have attributes. Though it can be bound to a DOM
+ * element - in this case the attributes and the nodeName are not shared.
+ *
+ * @public
+ * @extends AbstractType<YXmlEvent>
+ */
+export class YXmlFragment extends AbstractType {
+  constructor () {
+    super()
+    /**
+     * @type {Array<any>|null}
+     */
+    this._prelimContent = []
+  }
+
+  /**
+   * Integrate this type into the Yjs instance.
+   *
+   * * Save this struct in the os
+   * * This type is sent to other client
+   * * Observer functions are fired
+   *
+   * @param {Doc} y The Yjs instance
+   * @param {Item} item
+   */
+  _integrate (y, item) {
+    super._integrate(y, item)
+    this.insert(0, /** @type {Array<any>} */ (this._prelimContent))
+    this._prelimContent = null
+  }
+
+  _copy () {
+    return new YXmlFragment()
+  }
+
+  get length () {
+    return this._prelimContent === null ? this._length : this._prelimContent.length
+  }
+
+  /**
+   * Create a subtree of childNodes.
+   *
+   * @example
+   * const walker = elem.createTreeWalker(dom => dom.nodeName === 'div')
+   * for (let node in walker) {
+   *   // `node` is a div node
+   *   nop(node)
+   * }
+   *
+   * @param {function(AbstractType<any>):boolean} filter Function that is called on each child element and
+   *                          returns a Boolean indicating whether the child
+   *                          is to be included in the subtree.
+   * @return {YXmlTreeWalker} A subtree and a position within it.
+   *
+   * @public
+   */
+  createTreeWalker (filter) {
+    return new YXmlTreeWalker(this, filter)
+  }
+
+  /**
+   * Returns the first YXmlElement that matches the query.
+   * Similar to DOM's {@link querySelector}.
+   *
+   * Query support:
+   *   - tagname
+   * TODO:
+   *   - id
+   *   - attribute
+   *
+   * @param {CSS_Selector} query The query on the children.
+   * @return {YXmlElement|YXmlText|YXmlHook|null} The first element that matches the query or null.
+   *
+   * @public
+   */
+  querySelector (query) {
+    query = query.toUpperCase()
+    // @ts-ignore
+    const iterator = new YXmlTreeWalker(this, element => element.nodeName && element.nodeName.toUpperCase() === query)
+    const next = iterator.next()
+    if (next.done) {
+      return null
+    } else {
+      return next.value
+    }
+  }
+
+  /**
+   * Returns all YXmlElements that match the query.
+   * Similar to Dom's {@link querySelectorAll}.
+   *
+   * @todo Does not yet support all queries. Currently only query by tagName.
+   *
+   * @param {CSS_Selector} query The query on the children
+   * @return {Array<YXmlElement|YXmlText|YXmlHook|null>} The elements that match this query.
+   *
+   * @public
+   */
+  querySelectorAll (query) {
+    query = query.toUpperCase()
+    // @ts-ignore
+    return Array.from(new YXmlTreeWalker(this, element => element.nodeName && element.nodeName.toUpperCase() === query))
+  }
+
+  /**
+   * Creates YXmlEvent and calls observers.
+   *
+   * @param {Transaction} transaction
+   * @param {Set<null|string>} parentSubs Keys changed on this type. `null` if list was modified.
+   */
+  _callObserver (transaction, parentSubs) {
+    callTypeObservers(this, transaction, new YXmlEvent(this, parentSubs, transaction))
+  }
+
+  /**
+   * Get the string representation of all the children of this YXmlFragment.
+   *
+   * @return {string} The string representation of all children.
+   */
+  toString () {
+    return typeListMap(this, xml => xml.toString()).join('')
+  }
+
+  /**
+   * @return {string}
+   */
+  toJSON () {
+    return this.toString()
+  }
+
+  /**
+   * Creates a Dom Element that mirrors this YXmlElement.
+   *
+   * @param {Document} [_document=document] The document object (you must define
+   *                                        this when calling this method in
+   *                                        nodejs)
+   * @param {Object<string, any>} [hooks={}] Optional property to customize how hooks
+   *                                             are presented in the DOM
+   * @param {any} [binding] You should not set this property. This is
+   *                               used if DomBinding wants to create a
+   *                               association to the created DOM type.
+   * @return {Node} The {@link https://developer.mozilla.org/en-US/docs/Web/API/Element|Dom Element}
+   *
+   * @public
+   */
+  toDOM (_document = document, hooks = {}, binding) {
+    const fragment = _document.createDocumentFragment()
+    if (binding !== undefined) {
+      binding._createAssociation(fragment, this)
+    }
+    typeListForEach(this, xmlType => {
+      fragment.insertBefore(xmlType.toDOM(_document, hooks, binding), null)
+    })
+    return fragment
+  }
+
+  /**
+   * Inserts new content at an index.
+   *
+   * @example
+   *  // Insert character 'a' at position 0
+   *  xml.insert(0, [new Y.XmlText('text')])
+   *
+   * @param {number} index The index to insert content at
+   * @param {Array<YXmlElement|YXmlText>} content The array of content
+   */
+  insert (index, content) {
+    if (this.doc !== null) {
+      transact(this.doc, transaction => {
+        typeListInsertGenerics(transaction, this, index, content)
+      })
+    } else {
+      // @ts-ignore _prelimContent is defined because this is not yet integrated
+      this._prelimContent.splice(index, 0, ...content)
+    }
+  }
+
+  /**
+   * Deletes elements starting from an index.
+   *
+   * @param {number} index Index at which to start deleting elements
+   * @param {number} [length=1] The number of elements to remove. Defaults to 1.
+   */
+  delete (index, length = 1) {
+    if (this.doc !== null) {
+      transact(this.doc, transaction => {
+        typeListDelete(transaction, this, index, length)
+      })
+    } else {
+      // @ts-ignore _prelimContent is defined because this is not yet integrated
+      this._prelimContent.splice(index, length)
+    }
+  }
+
+  /**
+   * Transforms this YArray to a JavaScript Array.
+   *
+   * @return {Array<YXmlElement|YXmlText|YXmlHook>}
+   */
+  toArray () {
+    return typeListToArray(this)
+  }
+
+  /**
+   * Transform the properties of this type to binary and write it to an
+   * BinaryEncoder.
+   *
+   * This is called when this Item is sent to a remote peer.
+   *
+   * @param {encoding.Encoder} encoder The encoder to write data to.
+   */
+  _write (encoder) {
+    encoding.writeVarUint(encoder, YXmlFragmentRefID)
+  }
+}
+
+/**
+ * @param {decoding.Decoder} decoder
+ * @return {YXmlFragment}
+ *
+ * @private
+ * @function
+ */
+export const readYXmlFragment = decoder => new YXmlFragment()
--- a/src/types/YXmlHook.js
+++ b/src/types/YXmlHook.js
@@ -0,0 +1,86 @@
+
+import {
+  YMap,
+  YXmlHookRefID
+} from '../internals.js'
+import * as encoding from 'lib0/encoding.js'
+import * as decoding from 'lib0/decoding.js'
+
+/**
+ * You can manage binding to a custom type with YXmlHook.
+ *
+ * @extends {YMap<any>}
+ */
+export class YXmlHook extends YMap {
+  /**
+   * @param {string} hookName nodeName of the Dom Node.
+   */
+  constructor (hookName) {
+    super()
+    /**
+     * @type {string}
+     */
+    this.hookName = hookName
+  }
+
+  /**
+   * Creates an Item with the same effect as this Item (without position effect)
+   */
+  _copy () {
+    return new YXmlHook(this.hookName)
+  }
+
+  /**
+   * Creates a Dom Element that mirrors this YXmlElement.
+   *
+   * @param {Document} [_document=document] The document object (you must define
+   *                                        this when calling this method in
+   *                                        nodejs)
+   * @param {Object.<string, any>} [hooks] Optional property to customize how hooks
+   *                                             are presented in the DOM
+   * @param {any} [binding] You should not set this property. This is
+   *                               used if DomBinding wants to create a
+   *                               association to the created DOM type
+   * @return {Element} The {@link https://developer.mozilla.org/en-US/docs/Web/API/Element|Dom Element}
+   *
+   * @public
+   */
+  toDOM (_document = document, hooks = {}, binding) {
+    const hook = hooks[this.hookName]
+    let dom
+    if (hook !== undefined) {
+      dom = hook.createDom(this)
+    } else {
+      dom = document.createElement(this.hookName)
+    }
+    dom.setAttribute('data-yjs-hook', this.hookName)
+    if (binding !== undefined) {
+      binding._createAssociation(dom, this)
+    }
+    return dom
+  }
+
+  /**
+   * Transform the properties of this type to binary and write it to an
+   * BinaryEncoder.
+   *
+   * This is called when this Item is sent to a remote peer.
+   *
+   * @param {encoding.Encoder} encoder The encoder to write data to.
+   */
+  _write (encoder) {
+    super._write(encoder)
+    encoding.writeVarUint(encoder, YXmlHookRefID)
+    encoding.writeVarString(encoder, this.hookName)
+  }
+}
+
+/**
+ * @param {decoding.Decoder} decoder
+ * @return {YXmlHook}
+ *
+ * @private
+ * @function
+ */
+export const readYXmlHook = decoder =>
+  new YXmlHook(decoding.readVarString(decoder))
--- a/src/types/YXmlText.js
+++ b/src/types/YXmlText.js
@@ -0,0 +1,95 @@
+
+import { YText, YXmlTextRefID } from '../internals.js'
+
+import * as encoding from 'lib0/encoding.js'
+import * as decoding from 'lib0/decoding.js' // eslint-disable-line
+
+/**
+ * Represents text in a Dom Element. In the future this type will also handle
+ * simple formatting information like bold and italic.
+ */
+export class YXmlText extends YText {
+  _copy () {
+    return new YXmlText()
+  }
+
+  /**
+   * Creates a Dom Element that mirrors this YXmlText.
+   *
+   * @param {Document} [_document=document] The document object (you must define
+   *                                        this when calling this method in
+   *                                        nodejs)
+   * @param {Object<string, any>} [hooks] Optional property to customize how hooks
+   *                                             are presented in the DOM
+   * @param {any} [binding] You should not set this property. This is
+   *                               used if DomBinding wants to create a
+   *                               association to the created DOM type.
+   * @return {Text} The {@link https://developer.mozilla.org/en-US/docs/Web/API/Element|Dom Element}
+   *
+   * @public
+   */
+  toDOM (_document = document, hooks, binding) {
+    const dom = _document.createTextNode(this.toString())
+    if (binding !== undefined) {
+      binding._createAssociation(dom, this)
+    }
+    return dom
+  }
+
+  toString () {
+    // @ts-ignore
+    return this.toDelta().map(delta => {
+      const nestedNodes = []
+      for (const nodeName in delta.attributes) {
+        const attrs = []
+        for (const key in delta.attributes[nodeName]) {
+          attrs.push({ key, value: delta.attributes[nodeName][key] })
+        }
+        // sort attributes to get a unique order
+        attrs.sort((a, b) => a.key < b.key ? -1 : 1)
+        nestedNodes.push({ nodeName, attrs })
+      }
+      // sort node order to get a unique order
+      nestedNodes.sort((a, b) => a.nodeName < b.nodeName ? -1 : 1)
+      // now convert to dom string
+      let str = ''
+      for (let i = 0; i < nestedNodes.length; i++) {
+        const node = nestedNodes[i]
+        str += `<${node.nodeName}`
+        for (let j = 0; j < node.attrs.length; j++) {
+          const attr = node.attrs[j]
+          str += ` ${attr.key}="${attr.value}"`
+        }
+        str += '>'
+      }
+      str += delta.insert
+      for (let i = nestedNodes.length - 1; i >= 0; i--) {
+        str += `</${nestedNodes[i].nodeName}>`
+      }
+      return str
+    }).join('')
+  }
+
+  /**
+   * @return {string}
+   */
+  toJSON () {
+    return this.toString()
+  }
+
+  /**
+   * @param {encoding.Encoder} encoder
+   */
+  _write (encoder) {
+    encoding.writeVarUint(encoder, YXmlTextRefID)
+  }
+}
+
+/**
+ * @param {decoding.Decoder} decoder
+ * @return {YXmlText}
+ *
+ * @private
+ * @function
+ */
+export const readYXmlText = decoder => new YXmlText()
--- a/src/utils/DeleteSet.js
+++ b/src/utils/DeleteSet.js
@@ -0,0 +1,313 @@
+
+import {
+  findIndexSS,
+  getState,
+  splitItem,
+  createID,
+  iterateStructs,
+  Item, AbstractStruct, GC, StructStore, Transaction, ID // eslint-disable-line
+} from '../internals.js'
+
+import * as array from 'lib0/array.js'
+import * as math from 'lib0/math.js'
+import * as map from 'lib0/map.js'
+import * as encoding from 'lib0/encoding.js'
+import * as decoding from 'lib0/decoding.js'
+
+export class DeleteItem {
+  /**
+   * @param {number} clock
+   * @param {number} len
+   */
+  constructor (clock, len) {
+    /**
+     * @type {number}
+     */
+    this.clock = clock
+    /**
+     * @type {number}
+     */
+    this.len = len
+  }
+}
+
+/**
+ * We no longer maintain a DeleteStore. DeleteSet is a temporary object that is created when needed.
+ * - When created in a transaction, it must only be accessed after sorting, and merging
+ *   - This DeleteSet is send to other clients
+ * - We do not create a DeleteSet when we send a sync message. The DeleteSet message is created directly from StructStore
+ * - We read a DeleteSet as part of a sync/update message. In this case the DeleteSet is already sorted and merged.
+ */
+export class DeleteSet {
+  constructor () {
+    /**
+     * @type {Map<number,Array<DeleteItem>>}
+     */
+    this.clients = new Map()
+  }
+}
+
+/**
+ * Iterate over all structs that the DeleteSet gc's.
+ *
+ * @param {Transaction} transaction
+ * @param {DeleteSet} ds
+ * @param {function(GC|Item):void} f
+ *
+ * @function
+ */
+export const iterateDeletedStructs = (transaction, ds, f) =>
+  ds.clients.forEach((deletes, clientid) => {
+    const structs = /** @type {Array<GC|Item>} */ (transaction.doc.store.clients.get(clientid))
+    for (let i = 0; i < deletes.length; i++) {
+      const del = deletes[i]
+      iterateStructs(transaction, structs, del.clock, del.len, f)
+    }
+  })
+
+/**
+ * @param {Array<DeleteItem>} dis
+ * @param {number} clock
+ * @return {number|null}
+ *
+ * @private
+ * @function
+ */
+export const findIndexDS = (dis, clock) => {
+  let left = 0
+  let right = dis.length - 1
+  while (left <= right) {
+    const midindex = math.floor((left + right) / 2)
+    const mid = dis[midindex]
+    const midclock = mid.clock
+    if (midclock <= clock) {
+      if (clock < midclock + mid.len) {
+        return midindex
+      }
+      left = midindex + 1
+    } else {
+      right = midindex - 1
+    }
+  }
+  return null
+}
+
+/**
+ * @param {DeleteSet} ds
+ * @param {ID} id
+ * @return {boolean}
+ *
+ * @private
+ * @function
+ */
+export const isDeleted = (ds, id) => {
+  const dis = ds.clients.get(id.client)
+  return dis !== undefined && findIndexDS(dis, id.clock) !== null
+}
+
+/**
+ * @param {DeleteSet} ds
+ *
+ * @private
+ * @function
+ */
+export const sortAndMergeDeleteSet = ds => {
+  ds.clients.forEach(dels => {
+    dels.sort((a, b) => a.clock - b.clock)
+    // merge items without filtering or splicing the array
+    // i is the current pointer
+    // j refers to the current insert position for the pointed item
+    // try to merge dels[i] into dels[j-1] or set dels[j]=dels[i]
+    let i, j
+    for (i = 1, j = 1; i < dels.length; i++) {
+      const left = dels[j - 1]
+      const right = dels[i]
+      if (left.clock + left.len === right.clock) {
+        left.len += right.len
+      } else {
+        if (j < i) {
+          dels[j] = right
+        }
+        j++
+      }
+    }
+    dels.length = j
+  })
+}
+
+/**
+ * @param {Array<DeleteSet>} dss
+ * @return {DeleteSet} A fresh DeleteSet
+ */
+export const mergeDeleteSets = dss => {
+  const merged = new DeleteSet()
+  for (let dssI = 0; dssI < dss.length; dssI++) {
+    dss[dssI].clients.forEach((delsLeft, client) => {
+      if (!merged.clients.has(client)) {
+        // Write all missing keys from current ds and all following.
+        // If merged already contains `client` current ds has already been added.
+        /**
+         * @type {Array<DeleteItem>}
+         */
+        const dels = delsLeft.slice()
+        for (let i = dssI + 1; i < dss.length; i++) {
+          array.appendTo(dels, dss[i].clients.get(client) || [])
+        }
+        merged.clients.set(client, dels)
+      }
+    })
+  }
+  sortAndMergeDeleteSet(merged)
+  return merged
+}
+
+/**
+ * @param {DeleteSet} ds
+ * @param {ID} id
+ * @param {number} length
+ *
+ * @private
+ * @function
+ */
+export const addToDeleteSet = (ds, id, length) => {
+  map.setIfUndefined(ds.clients, id.client, () => []).push(new DeleteItem(id.clock, length))
+}
+
+export const createDeleteSet = () => new DeleteSet()
+
+/**
+ * @param {StructStore} ss
+ * @return {DeleteSet} Merged and sorted DeleteSet
+ *
+ * @private
+ * @function
+ */
+export const createDeleteSetFromStructStore = ss => {
+  const ds = createDeleteSet()
+  ss.clients.forEach((structs, client) => {
+    /**
+     * @type {Array<DeleteItem>}
+     */
+    const dsitems = []
+    for (let i = 0; i < structs.length; i++) {
+      const struct = structs[i]
+      if (struct.deleted) {
+        const clock = struct.id.clock
+        let len = struct.length
+        if (i + 1 < structs.length) {
+          for (let next = structs[i + 1]; i + 1 < structs.length && next.id.clock === clock + len && next.deleted; next = structs[++i + 1]) {
+            len += next.length
+          }
+        }
+        dsitems.push(new DeleteItem(clock, len))
+      }
+    }
+    if (dsitems.length > 0) {
+      ds.clients.set(client, dsitems)
+    }
+  })
+  return ds
+}
+
+/**
+ * @param {encoding.Encoder} encoder
+ * @param {DeleteSet} ds
+ *
+ * @private
+ * @function
+ */
+export const writeDeleteSet = (encoder, ds) => {
+  encoding.writeVarUint(encoder, ds.clients.size)
+  ds.clients.forEach((dsitems, client) => {
+    encoding.writeVarUint(encoder, client)
+    const len = dsitems.length
+    encoding.writeVarUint(encoder, len)
+    for (let i = 0; i < len; i++) {
+      const item = dsitems[i]
+      encoding.writeVarUint(encoder, item.clock)
+      encoding.writeVarUint(encoder, item.len)
+    }
+  })
+}
+
+/**
+ * @param {decoding.Decoder} decoder
+ * @return {DeleteSet}
+ *
+ * @private
+ * @function
+ */
+export const readDeleteSet = decoder => {
+  const ds = new DeleteSet()
+  const numClients = decoding.readVarUint(decoder)
+  for (let i = 0; i < numClients; i++) {
+    const client = decoding.readVarUint(decoder)
+    const numberOfDeletes = decoding.readVarUint(decoder)
+    for (let i = 0; i < numberOfDeletes; i++) {
+      addToDeleteSet(ds, createID(client, decoding.readVarUint(decoder)), decoding.readVarUint(decoder))
+    }
+  }
+  return ds
+}
+
+/**
+ * @param {decoding.Decoder} decoder
+ * @param {Transaction} transaction
+ * @param {StructStore} store
+ *
+ * @private
+ * @function
+ */
+export const readAndApplyDeleteSet = (decoder, transaction, store) => {
+  const unappliedDS = new DeleteSet()
+  const numClients = decoding.readVarUint(decoder)
+  for (let i = 0; i < numClients; i++) {
+    const client = decoding.readVarUint(decoder)
+    const numberOfDeletes = decoding.readVarUint(decoder)
+    const structs = store.clients.get(client) || []
+    const state = getState(store, client)
+    for (let i = 0; i < numberOfDeletes; i++) {
+      const clock = decoding.readVarUint(decoder)
+      const len = decoding.readVarUint(decoder)
+      if (clock < state) {
+        if (state < clock + len) {
+          addToDeleteSet(unappliedDS, createID(client, state), clock + len - state)
+        }
+        let index = findIndexSS(structs, clock)
+        /**
+         * We can ignore the case of GC and Delete structs, because we are going to skip them
+         * @type {Item}
+         */
+        // @ts-ignore
+        let struct = structs[index]
+        // split the first item if necessary
+        if (!struct.deleted && struct.id.clock < clock) {
+          structs.splice(index + 1, 0, splitItem(transaction, struct, clock - struct.id.clock))
+          index++ // increase we now want to use the next struct
+        }
+        while (index < structs.length) {
+          // @ts-ignore
+          struct = structs[index++]
+          if (struct.id.clock < clock + len) {
+            if (!struct.deleted) {
+              if (clock + len < struct.id.clock + struct.length) {
+                structs.splice(index, 0, splitItem(transaction, struct, clock + len - struct.id.clock))
+              }
+              struct.delete(transaction)
+            }
+          } else {
+            break
+          }
+        }
+      } else {
+        addToDeleteSet(unappliedDS, createID(client, clock), len)
+      }
+    }
+  }
+  if (unappliedDS.clients.size > 0) {
+    // TODO: no need for encoding+decoding ds anymore
+    const unappliedDSEncoder = encoding.createEncoder()
+    writeDeleteSet(unappliedDSEncoder, unappliedDS)
+    store.pendingDeleteReaders.push(decoding.createDecoder(encoding.toUint8Array(unappliedDSEncoder)))
+  }
+}
--- a/src/utils/Doc.js
+++ b/src/utils/Doc.js
@@ -0,0 +1,195 @@
+/**
+ * @module Y
+ */
+
+import {
+  StructStore,
+  AbstractType,
+  YArray,
+  YText,
+  YMap,
+  YXmlFragment,
+  transact,
+  Item, Transaction, YEvent // eslint-disable-line
+} from '../internals.js'
+
+import { Observable } from 'lib0/observable.js'
+import * as random from 'lib0/random.js'
+import * as map from 'lib0/map.js'
+
+export const generateNewClientId = random.uint32
+
+/**
+ * A Yjs instance handles the state of shared data.
+ * @extends Observable<string>
+ */
+export class Doc extends Observable {
+  /**
+   * @param {Object} conf configuration
+   * @param {boolean} [conf.gc] Disable garbage collection (default: gc=true)
+   * @param {function(Item):boolean} [conf.gcFilter] Will be called before an Item is garbage collected. Return false to keep the Item.
+   */
+  constructor ({ gc = true, gcFilter = () => true } = {}) {
+    super()
+    this.gc = gc
+    this.gcFilter = gcFilter
+    this.clientID = generateNewClientId()
+    /**
+     * @type {Map<string, AbstractType<YEvent>>}
+     */
+    this.share = new Map()
+    this.store = new StructStore()
+    /**
+     * @type {Transaction | null}
+     */
+    this._transaction = null
+    /**
+     * @type {Array<Transaction>}
+     */
+    this._transactionCleanups = []
+  }
+
+  /**
+   * Changes that happen inside of a transaction are bundled. This means that
+   * the observer fires _after_ the transaction is finished and that all changes
+   * that happened inside of the transaction are sent as one message to the
+   * other peers.
+   *
+   * @param {function(Transaction):void} f The function that should be executed as a transaction
+   * @param {any} [origin] Origin of who started the transaction. Will be stored on transaction.origin
+   *
+   * @public
+   */
+  transact (f, origin = null) {
+    transact(this, f, origin)
+  }
+
+  /**
+   * Get a shared data type by name. If it does not yet exist, define its type.
+   *
+   * Multiple calls of `y.get(name, TypeConstructor)` yield the same result
+   * and do not overwrite each other, i.e.
+   *   `y.get(name, Y.Array) === y.get(name, Y.Array)`
+   *
+   * After this method is called, the type is also available on `y.share.get(name)`.
+   *
+   * *Best Practices:*
+   * Define all types right after the Yjs instance is created and store them in a separate object.
+   * Also use the typed methods `getText(name)`, `getArray(name)`, `getMap(name)`, etc.
+   *
+   * @example
+   *   const y = new Y(..)
+   *   const appState = {
+   *     document: y.getText('document')
+   *     comments: y.getArray('comments')
+   *   }
+   *
+   * @param {string} name
+   * @param {Function} TypeConstructor The constructor of the type definition. E.g. Y.Text, Y.Array, Y.Map, ...
+   * @return {AbstractType<any>} The created type. Constructed with TypeConstructor
+   *
+   * @public
+   */
+  get (name, TypeConstructor = AbstractType) {
+    const type = map.setIfUndefined(this.share, name, () => {
+      // @ts-ignore
+      const t = new TypeConstructor()
+      t._integrate(this, null)
+      return t
+    })
+    const Constr = type.constructor
+    if (TypeConstructor !== AbstractType && Constr !== TypeConstructor) {
+      if (Constr === AbstractType) {
+        // @ts-ignore
+        const t = new TypeConstructor()
+        t._map = type._map
+        type._map.forEach(/** @param {Item?} n */ n => {
+          for (; n !== null; n = n.left) {
+            // @ts-ignore
+            n.parent = t
+          }
+        })
+        t._start = type._start
+        for (let n = t._start; n !== null; n = n.right) {
+          n.parent = t
+        }
+        t._length = type._length
+        this.share.set(name, t)
+        t._integrate(this, null)
+        return t
+      } else {
+        throw new Error(`Type with the name ${name} has already been defined with a different constructor`)
+      }
+    }
+    return type
+  }
+
+  /**
+   * @template T
+   * @param {string} name
+   * @return {YArray<T>}
+   *
+   * @public
+   */
+  getArray (name) {
+    // @ts-ignore
+    return this.get(name, YArray)
+  }
+
+  /**
+   * @param {string} name
+   * @return {YText}
+   *
+   * @public
+   */
+  getText (name) {
+    // @ts-ignore
+    return this.get(name, YText)
+  }
+
+  /**
+   * @param {string} name
+   * @return {YMap<any>}
+   *
+   * @public
+   */
+  getMap (name) {
+    // @ts-ignore
+    return this.get(name, YMap)
+  }
+
+  /**
+   * @param {string} name
+   * @return {YXmlFragment}
+   *
+   * @public
+   */
+  getXmlFragment (name) {
+    // @ts-ignore
+    return this.get(name, YXmlFragment)
+  }
+
+  /**
+   * Emit `destroy` event and unregister all event handlers.
+   */
+  destroy () {
+    this.emit('destroyed', [true])
+    super.destroy()
+  }
+
+  /**
+   * @param {string} eventName
+   * @param {function} f
+   */
+  on (eventName, f) {
+    super.on(eventName, f)
+  }
+
+  /**
+   * @param {string} eventName
+   * @param {function} f
+   */
+  off (eventName, f) {
+    super.off(eventName, f)
+  }
+}
--- a/src/utils/EventHandler.js
+++ b/src/utils/EventHandler.js
@@ -0,0 +1,82 @@
+import * as f from 'lib0/function.js'
+
+/**
+ * General event handler implementation.
+ *
+ * @template ARG0, ARG1
+ *
+ * @private
+ */
+export class EventHandler {
+  constructor () {
+    /**
+     * @type {Array<function(ARG0, ARG1):void>}
+     */
+    this.l = []
+  }
+}
+
+/**
+ * @template ARG0,ARG1
+ * @returns {EventHandler<ARG0,ARG1>}
+ *
+ * @private
+ * @function
+ */
+export const createEventHandler = () => new EventHandler()
+
+/**
+ * Adds an event listener that is called when
+ * {@link EventHandler#callEventListeners} is called.
+ *
+ * @template ARG0,ARG1
+ * @param {EventHandler<ARG0,ARG1>} eventHandler
+ * @param {function(ARG0,ARG1):void} f The event handler.
+ *
+ * @private
+ * @function
+ */
+export const addEventHandlerListener = (eventHandler, f) =>
+  eventHandler.l.push(f)
+
+/**
+ * Removes an event listener.
+ *
+ * @template ARG0,ARG1
+ * @param {EventHandler<ARG0,ARG1>} eventHandler
+ * @param {function(ARG0,ARG1):void} f The event handler that was added with
+ *                     {@link EventHandler#addEventListener}
+ *
+ * @private
+ * @function
+ */
+export const removeEventHandlerListener = (eventHandler, f) => {
+  eventHandler.l = eventHandler.l.filter(g => f !== g)
+}
+
+/**
+ * Removes all event listeners.
+ * @template ARG0,ARG1
+ * @param {EventHandler<ARG0,ARG1>} eventHandler
+ *
+ * @private
+ * @function
+ */
+export const removeAllEventHandlerListeners = eventHandler => {
+  eventHandler.l.length = 0
+}
+
+/**
+ * Call all event listeners that were added via
+ * {@link EventHandler#addEventListener}.
+ *
+ * @template ARG0,ARG1
+ * @param {EventHandler<ARG0,ARG1>} eventHandler
+ * @param {ARG0} arg0
+ * @param {ARG1} arg1
+ *
+ * @private
+ * @function
+ */
+export const callEventHandlerListeners = (eventHandler, arg0, arg1) =>
+  f.callAll(eventHandler.l, [arg0, arg1])
--- a/src/utils/ID.js
+++ b/src/utils/ID.js
@@ -0,0 +1,90 @@
+
+import { AbstractType } from '../internals.js' // eslint-disable-line
+
+import * as decoding from 'lib0/decoding.js'
+import * as encoding from 'lib0/encoding.js'
+import * as error from 'lib0/error.js'
+
+export class ID {
+  /**
+   * @param {number} client client id
+   * @param {number} clock unique per client id, continuous number
+   */
+  constructor (client, clock) {
+    /**
+     * Client id
+     * @type {number}
+     */
+    this.client = client
+    /**
+     * unique per client id, continuous number
+     * @type {number}
+     */
+    this.clock = clock
+  }
+}
+
+/**
+ * @param {ID | null} a
+ * @param {ID | null} b
+ * @return {boolean}
+ *
+ * @function
+ */
+export const compareIDs = (a, b) => a === b || (a !== null && b !== null && a.client === b.client && a.clock === b.clock)
+
+/**
+ * @param {number} client
+ * @param {number} clock
+ *
+ * @private
+ * @function
+ */
+export const createID = (client, clock) => new ID(client, clock)
+
+/**
+ * @param {encoding.Encoder} encoder
+ * @param {ID} id
+ *
+ * @private
+ * @function
+ */
+export const writeID = (encoder, id) => {
+  encoding.writeVarUint(encoder, id.client)
+  encoding.writeVarUint(encoder, id.clock)
+}
+
+/**
+ * Read ID.
+ * * If first varUint read is 0xFFFFFF a RootID is returned.
+ * * Otherwise an ID is returned
+ *
+ * @param {decoding.Decoder} decoder
+ * @return {ID}
+ *
+ * @private
+ * @function
+ */
+export const readID = decoder =>
+  createID(decoding.readVarUint(decoder), decoding.readVarUint(decoder))
+
+/**
+ * The top types are mapped from y.share.get(keyname) => type.
+ * `type` does not store any information about the `keyname`.
+ * This function finds the correct `keyname` for `type` and throws otherwise.
+ *
+ * @param {AbstractType<any>} type
+ * @return {string}
+ *
+ * @private
+ * @function
+ */
+export const findRootTypeKey = type => {
+  // @ts-ignore _y must be defined, otherwise unexpected case
+  for (const [key, value] of type.doc.share) {
+    if (value === type) {
+      return key
+    }
+  }
+  throw error.unexpectedCase()
+}
--- a/src/utils/PermanentUserData.js
+++ b/src/utils/PermanentUserData.js
@@ -0,0 +1,142 @@
+
+import {
+  YArray,
+  YMap,
+  readDeleteSet,
+  writeDeleteSet,
+  createDeleteSet,
+  ID, DeleteSet, YArrayEvent, Transaction, Doc // eslint-disable-line
+} from '../internals.js'
+
+import * as decoding from 'lib0/decoding.js'
+import * as encoding from 'lib0/encoding.js'
+import { mergeDeleteSets, isDeleted } from './DeleteSet.js'
+
+export class PermanentUserData {
+  /**
+   * @param {Doc} doc
+   * @param {YMap<any>} [storeType]
+   */
+  constructor (doc, storeType = doc.getMap('users')) {
+    /**
+     * @type {Map<string,DeleteSet>}
+     */
+    const dss = new Map()
+    this.yusers = storeType
+    this.doc = doc
+    /**
+     * Maps from clientid to userDescription
+     *
+     * @type {Map<number,string>}
+     */
+    this.clients = new Map()
+    this.dss = dss
+    /**
+     * @param {YMap<any>} user
+     * @param {string} userDescription
+     */
+    const initUser = (user, userDescription) => {
+      /**
+       * @type {YArray<Uint8Array>}
+       */
+      const ds = user.get('ds')
+      const ids = user.get('ids')
+      const addClientId = /** @param {number} clientid */ clientid => this.clients.set(clientid, userDescription)
+      ds.observe(/** @param {YArrayEvent<any>} event */ event => {
+        event.changes.added.forEach(item => {
+          item.content.getContent().forEach(encodedDs => {
+            if (encodedDs instanceof Uint8Array) {
+              this.dss.set(userDescription, mergeDeleteSets([this.dss.get(userDescription) || createDeleteSet(), readDeleteSet(decoding.createDecoder(encodedDs))]))
+            }
+          })
+        })
+      })
+      this.dss.set(userDescription, mergeDeleteSets(ds.map(encodedDs => readDeleteSet(decoding.createDecoder(encodedDs)))))
+      ids.observe(/** @param {YArrayEvent<any>} event */ event =>
+        event.changes.added.forEach(item => item.content.getContent().forEach(addClientId))
+      )
+      ids.forEach(addClientId)
+    }
+    // observe users
+    storeType.observe(event => {
+      event.keysChanged.forEach(userDescription =>
+        initUser(storeType.get(userDescription), userDescription)
+      )
+    })
+    // add intial data
+    storeType.forEach(initUser)
+  }
+
+  /**
+   * @param {Doc} doc
+   * @param {number} clientid
+   * @param {string} userDescription
+   * @param {Object} [conf]
+   * @param {function(Transaction, DeleteSet):boolean} [conf.filter]
+   */
+  setUserMapping (doc, clientid, userDescription, { filter = () => true } = {}) {
+    const users = this.yusers
+    let user = users.get(userDescription)
+    if (!user) {
+      user = new YMap()
+      user.set('ids', new YArray())
+      user.set('ds', new YArray())
+      users.set(userDescription, user)
+    }
+    user.get('ids').push([clientid])
+    users.observe(event => {
+      setTimeout(() => {
+        const userOverwrite = users.get(userDescription)
+        if (userOverwrite !== user) {
+          // user was overwritten, port all data over to the next user object
+          // @todo Experiment with Y.Sets here
+          user = userOverwrite
+          // @todo iterate over old type
+          this.clients.forEach((_userDescription, clientid) => {
+            if (userDescription === _userDescription) {
+              user.get('ids').push([clientid])
+            }
+          })
+          const encoder = encoding.createEncoder()
+          const ds = this.dss.get(userDescription)
+          if (ds) {
+            writeDeleteSet(encoder, ds)
+            user.get('ds').push([encoding.toUint8Array(encoder)])
+          }
+        }
+      }, 0)
+    })
+    doc.on('afterTransaction', /** @param {Transaction} transaction */ transaction => {
+      setTimeout(() => {
+        const yds = user.get('ds')
+        const ds = transaction.deleteSet
+        if (transaction.local && ds.clients.size > 0 && filter(transaction, ds)) {
+          const encoder = encoding.createEncoder()
+          writeDeleteSet(encoder, ds)
+          yds.push([encoding.toUint8Array(encoder)])
+        }
+      })
+    })
+  }
+
+  /**
+   * @param {number} clientid
+   * @return {any}
+   */
+  getUserByClientId (clientid) {
+    return this.clients.get(clientid) || null
+  }
+
+  /**
+   * @param {ID} id
+   * @return {string | null}
+   */
+  getUserByDeletedId (id) {
+    for (const [userDescription, ds] of this.dss) {
+      if (isDeleted(ds, id)) {
+        return userDescription
+      }
+    }
+    return null
+  }
+}
--- a/src/utils/RelativePosition.js
+++ b/src/utils/RelativePosition.js
@@ -0,0 +1,272 @@
+
+import {
+  writeID,
+  readID,
+  compareIDs,
+  getState,
+  findRootTypeKey,
+  Item,
+  createID,
+  ContentType,
+  followRedone,
+  ID, Doc, AbstractType // eslint-disable-line
+} from '../internals.js'
+
+import * as encoding from 'lib0/encoding.js'
+import * as decoding from 'lib0/decoding.js'
+import * as error from 'lib0/error.js'
+
+/**
+ * A relative position is based on the Yjs model and is not affected by document changes.
+ * E.g. If you place a relative position before a certain character, it will always point to this character.
+ * If you place a relative position at the end of a type, it will always point to the end of the type.
+ *
+ * A numeric position is often unsuited for user selections, because it does not change when content is inserted
+ * before or after.
+ *
+ * ```Insert(0, 'x')('a|bc') = 'xa|bc'``` Where | is the relative position.
+ *
+ * One of the properties must be defined.
+ *
+ * @example
+ *   // Current cursor position is at position 10
+ *   const relativePosition = createRelativePositionFromIndex(yText, 10)
+ *   // modify yText
+ *   yText.insert(0, 'abc')
+ *   yText.delete(3, 10)
+ *   // Compute the cursor position
+ *   const absolutePosition = createAbsolutePositionFromRelativePosition(y, relativePosition)
+ *   absolutePosition.type === yText // => true
+ *   console.log('cursor location is ' + absolutePosition.index) // => cursor location is 3
+ *
+ */
+export class RelativePosition {
+  /**
+   * @param {ID|null} type
+   * @param {string|null} tname
+   * @param {ID|null} item
+   */
+  constructor (type, tname, item) {
+    /**
+     * @type {ID|null}
+     */
+    this.type = type
+    /**
+     * @type {string|null}
+     */
+    this.tname = tname
+    /**
+     * @type {ID | null}
+     */
+    this.item = item
+  }
+}
+
+/**
+ * @param {any} json
+ * @return {RelativePosition}
+ *
+ * @function
+ */
+export const createRelativePositionFromJSON = json => new RelativePosition(json.type == null ? null : createID(json.type.client, json.type.clock), json.tname || null, json.item == null ? null : createID(json.item.client, json.item.clock))
+
+export class AbsolutePosition {
+  /**
+   * @param {AbstractType<any>} type
+   * @param {number} index
+   */
+  constructor (type, index) {
+    /**
+     * @type {AbstractType<any>}
+     */
+    this.type = type
+    /**
+     * @type {number}
+     */
+    this.index = index
+  }
+}
+
+/**
+ * @param {AbstractType<any>} type
+ * @param {number} index
+ *
+ * @function
+ */
+export const createAbsolutePosition = (type, index) => new AbsolutePosition(type, index)
+
+/**
+ * @param {AbstractType<any>} type
+ * @param {ID|null} item
+ *
+ * @function
+ */
+export const createRelativePosition = (type, item) => {
+  let typeid = null
+  let tname = null
+  if (type._item === null) {
+    tname = findRootTypeKey(type)
+  } else {
+    typeid = createID(type._item.id.client, type._item.id.clock)
+  }
+  return new RelativePosition(typeid, tname, item)
+}
+
+/**
+ * Create a relativePosition based on a absolute position.
+ *
+ * @param {AbstractType<any>} type The base type (e.g. YText or YArray).
+ * @param {number} index The absolute position.
+ * @return {RelativePosition}
+ *
+ * @function
+ */
+export const createRelativePositionFromTypeIndex = (type, index) => {
+  let t = type._start
+  while (t !== null) {
+    if (!t.deleted && t.countable) {
+      if (t.length > index) {
+        // case 1: found position somewhere in the linked list
+        return createRelativePosition(type, createID(t.id.client, t.id.clock + index))
+      }
+      index -= t.length
+    }
+    t = t.right
+  }
+  return createRelativePosition(type, null)
+}
+
+/**
+ * @param {encoding.Encoder} encoder
+ * @param {RelativePosition} rpos
+ *
+ * @function
+ */
+export const writeRelativePosition = (encoder, rpos) => {
+  const { type, tname, item } = rpos
+  if (item !== null) {
+    encoding.writeVarUint(encoder, 0)
+    writeID(encoder, item)
+  } else if (tname !== null) {
+    // case 2: found position at the end of the list and type is stored in y.share
+    encoding.writeUint8(encoder, 1)
+    encoding.writeVarString(encoder, tname)
+  } else if (type !== null) {
+    // case 3: found position at the end of the list and type is attached to an item
+    encoding.writeUint8(encoder, 2)
+    writeID(encoder, type)
+  } else {
+    throw error.unexpectedCase()
+  }
+  return encoder
+}
+
+/**
+ * @param {RelativePosition} rpos
+ * @return {Uint8Array}
+ */
+export const encodeRelativePosition = rpos => {
+  const encoder = encoding.createEncoder()
+  writeRelativePosition(encoder, rpos)
+  return encoding.toUint8Array(encoder)
+}
+
+/**
+ * @param {decoding.Decoder} decoder
+ * @return {RelativePosition|null}
+ *
+ * @function
+ */
+export const readRelativePosition = decoder => {
+  let type = null
+  let tname = null
+  let itemID = null
+  switch (decoding.readVarUint(decoder)) {
+    case 0:
+      // case 1: found position somewhere in the linked list
+      itemID = readID(decoder)
+      break
+    case 1:
+      // case 2: found position at the end of the list and type is stored in y.share
+      tname = decoding.readVarString(decoder)
+      break
+    case 2: {
+      // case 3: found position at the end of the list and type is attached to an item
+      type = readID(decoder)
+    }
+  }
+  return new RelativePosition(type, tname, itemID)
+}
+
+/**
+ * @param {Uint8Array} uint8Array
+ * @return {RelativePosition|null}
+ */
+export const decodeRelativePosition = uint8Array => readRelativePosition(decoding.createDecoder(uint8Array))
+
+/**
+ * @param {RelativePosition} rpos
+ * @param {Doc} doc
+ * @return {AbsolutePosition|null}
+ *
+ * @function
+ */
+export const createAbsolutePositionFromRelativePosition = (rpos, doc) => {
+  const store = doc.store
+  const rightID = rpos.item
+  const typeID = rpos.type
+  const tname = rpos.tname
+  let type = null
+  let index = 0
+  if (rightID !== null) {
+    if (getState(store, rightID.client) <= rightID.clock) {
+      return null
+    }
+    const res = followRedone(store, rightID)
+    const right = res.item
+    if (!(right instanceof Item)) {
+      return null
+    }
+    type = /** @type {AbstractType<any>} */ (right.parent)
+    if (type._item === null || !type._item.deleted) {
+      index = right.deleted || !right.countable ? 0 : res.diff
+      let n = right.left
+      while (n !== null) {
+        if (!n.deleted && n.countable) {
+          index += n.length
+        }
+        n = n.left
+      }
+    }
+  } else {
+    if (tname !== null) {
+      type = doc.get(tname)
+    } else if (typeID !== null) {
+      if (getState(store, typeID.client) <= typeID.clock) {
+        // type does not exist yet
+        return null
+      }
+      const { item } = followRedone(store, typeID)
+      if (item instanceof Item && item.content instanceof ContentType) {
+        type = item.content.type
+      } else {
+        // struct is garbage collected
+        return null
+      }
+    } else {
+      throw error.unexpectedCase()
+    }
+    index = type._length
+  }
+  return createAbsolutePosition(type, index)
+}
+
+/**
+ * @param {RelativePosition|null} a
+ * @param {RelativePosition|null} b
+ *
+ * @function
+ */
+export const compareRelativePositions = (a, b) => a === b || (
+  a !== null && b !== null && a.tname === b.tname && compareIDs(a.item, b.item) && compareIDs(a.type, b.type)
+)
--- a/src/utils/Snapshot.js
+++ b/src/utils/Snapshot.js
@@ -0,0 +1,138 @@
+
+import {
+  isDeleted,
+  createDeleteSetFromStructStore,
+  getStateVector,
+  getItemCleanStart,
+  iterateDeletedStructs,
+  writeDeleteSet,
+  writeStateVector,
+  readDeleteSet,
+  readStateVector,
+  createDeleteSet,
+  createID,
+  getState,
+  Transaction, Doc, DeleteSet, Item // eslint-disable-line
+} from '../internals.js'
+
+import * as map from 'lib0/map.js'
+import * as set from 'lib0/set.js'
+import * as encoding from 'lib0/encoding.js'
+import * as decoding from 'lib0/decoding.js'
+
+export class Snapshot {
+  /**
+   * @param {DeleteSet} ds
+   * @param {Map<number,number>} sv state map
+   */
+  constructor (ds, sv) {
+    /**
+     * @type {DeleteSet}
+     */
+    this.ds = ds
+    /**
+     * State Map
+     * @type {Map<number,number>}
+     */
+    this.sv = sv
+  }
+}
+
+/**
+ * @param {Snapshot} snap1
+ * @param {Snapshot} snap2
+ * @return {boolean}
+ */
+export const equalSnapshots = (snap1, snap2) => {
+  const ds1 = snap1.ds.clients
+  const ds2 = snap2.ds.clients
+  const sv1 = snap1.sv
+  const sv2 = snap2.sv
+  if (sv1.size !== sv2.size || ds1.size !== ds2.size) {
+    return false
+  }
+  for (const [key, value] of sv1) {
+    if (sv2.get(key) !== value) {
+      return false
+    }
+  }
+  for (const [client, dsitems1] of ds1) {
+    const dsitems2 = ds2.get(client) || []
+    if (dsitems1.length !== dsitems2.length) {
+      return false
+    }
+    for (let i = 0; i < dsitems1.length; i++) {
+      const dsitem1 = dsitems1[i]
+      const dsitem2 = dsitems2[i]
+      if (dsitem1.clock !== dsitem2.clock || dsitem1.len !== dsitem2.len) {
+        return false
+      }
+    }
+  }
+  return true
+}
+
+/**
+ * @param {Snapshot} snapshot
+ * @return {Uint8Array}
+ */
+export const encodeSnapshot = snapshot => {
+  const encoder = encoding.createEncoder()
+  writeDeleteSet(encoder, snapshot.ds)
+  writeStateVector(encoder, snapshot.sv)
+  return encoding.toUint8Array(encoder)
+}
+
+/**
+ * @param {Uint8Array} buf
+ * @return {Snapshot}
+ */
+export const decodeSnapshot = buf => {
+  const decoder = decoding.createDecoder(buf)
+  return new Snapshot(readDeleteSet(decoder), readStateVector(decoder))
+}
+
+/**
+ * @param {DeleteSet} ds
+ * @param {Map<number,number>} sm
+ * @return {Snapshot}
+ */
+export const createSnapshot = (ds, sm) => new Snapshot(ds, sm)
+
+export const emptySnapshot = createSnapshot(createDeleteSet(), new Map())
+
+/**
+ * @param {Doc} doc
+ * @return {Snapshot}
+ */
+export const snapshot = doc => createSnapshot(createDeleteSetFromStructStore(doc.store), getStateVector(doc.store))
+
+/**
+ * @param {Item} item
+ * @param {Snapshot|undefined} snapshot
+ *
+ * @protected
+ * @function
+ */
+export const isVisible = (item, snapshot) => snapshot === undefined ? !item.deleted : (
+  snapshot.sv.has(item.id.client) && (snapshot.sv.get(item.id.client) || 0) > item.id.clock && !isDeleted(snapshot.ds, item.id)
+)
+
+/**
+ * @param {Transaction} transaction
+ * @param {Snapshot} snapshot
+ */
+export const splitSnapshotAffectedStructs = (transaction, snapshot) => {
+  const meta = map.setIfUndefined(transaction.meta, splitSnapshotAffectedStructs, set.create)
+  const store = transaction.doc.store
+  // check if we already split for this snapshot
+  if (!meta.has(snapshot)) {
+    snapshot.sv.forEach((clock, client) => {
+      if (clock < getState(store, client)) {
+        getItemCleanStart(transaction, createID(client, clock))
+      }
+    })
+    iterateDeletedStructs(transaction, snapshot.ds, item => {})
+    meta.add(snapshot)
+  }
+}
--- a/src/utils/StructStore.js
+++ b/src/utils/StructStore.js
@@ -0,0 +1,274 @@
+
+import {
+  GC,
+  splitItem,
+  AbstractStruct, Transaction, ID, Item // eslint-disable-line
+} from '../internals.js'
+
+import * as math from 'lib0/math.js'
+import * as error from 'lib0/error.js'
+import * as decoding from 'lib0/decoding.js' // eslint-disable-line
+
+export class StructStore {
+  constructor () {
+    /**
+     * @type {Map<number,Array<GC|Item>>}
+     */
+    this.clients = new Map()
+    /**
+     * Store incompleted struct reads here
+     * `i` denotes to the next read operation
+     * We could shift the array of refs instead, but shift is incredible
+     * slow in Chrome for arrays with more than 100k elements
+     * @see tryResumePendingStructRefs
+     * @type {Map<number,{i:number,refs:Array<GC|Item>}>}
+     */
+    this.pendingClientsStructRefs = new Map()
+    /**
+     * Stack of pending structs waiting for struct dependencies
+     * Maximum length of stack is structReaders.size
+     * @type {Array<GC|Item>}
+     */
+    this.pendingStack = []
+    /**
+     * @type {Array<decoding.Decoder>}
+     */
+    this.pendingDeleteReaders = []
+  }
+}
+
+/**
+ * Return the states as a Map<client,clock>.
+ * Note that clock refers to the next expected clock id.
+ *
+ * @param {StructStore} store
+ * @return {Map<number,number>}
+ *
+ * @public
+ * @function
+ */
+export const getStateVector = store => {
+  const sm = new Map()
+  store.clients.forEach((structs, client) => {
+    const struct = structs[structs.length - 1]
+    sm.set(client, struct.id.clock + struct.length)
+  })
+  return sm
+}
+
+/**
+ * @param {StructStore} store
+ * @param {number} client
+ * @return {number}
+ *
+ * @public
+ * @function
+ */
+export const getState = (store, client) => {
+  const structs = store.clients.get(client)
+  if (structs === undefined) {
+    return 0
+  }
+  const lastStruct = structs[structs.length - 1]
+  return lastStruct.id.clock + lastStruct.length
+}
+
+/**
+ * @param {StructStore} store
+ *
+ * @private
+ * @function
+ */
+export const integretyCheck = store => {
+  store.clients.forEach(structs => {
+    for (let i = 1; i < structs.length; i++) {
+      const l = structs[i - 1]
+      const r = structs[i]
+      if (l.id.clock + l.length !== r.id.clock) {
+        throw new Error('StructStore failed integrety check')
+      }
+    }
+  })
+}
+
+/**
+ * @param {StructStore} store
+ * @param {GC|Item} struct
+ *
+ * @private
+ * @function
+ */
+export const addStruct = (store, struct) => {
+  let structs = store.clients.get(struct.id.client)
+  if (structs === undefined) {
+    structs = []
+    store.clients.set(struct.id.client, structs)
+  } else {
+    const lastStruct = structs[structs.length - 1]
+    if (lastStruct.id.clock + lastStruct.length !== struct.id.clock) {
+      throw error.unexpectedCase()
+    }
+  }
+  structs.push(struct)
+}
+
+/**
+ * Perform a binary search on a sorted array
+ * @param {Array<Item|GC>} structs
+ * @param {number} clock
+ * @return {number}
+ *
+ * @private
+ * @function
+ */
+export const findIndexSS = (structs, clock) => {
+  let left = 0
+  let right = structs.length - 1
+  let mid = structs[right]
+  let midclock = mid.id.clock
+  if (midclock === clock) {
+    return right
+  }
+  // @todo does it even make sense to pivot the search?
+  // If a good split misses, it might actually increase the time to find the correct item.
+  // Currently, the only advantage is that search with pivoting might find the item on the first try.
+  let midindex = math.floor((clock / (midclock + mid.length - 1)) * right) // pivoting the search
+  while (left <= right) {
+    mid = structs[midindex]
+    midclock = mid.id.clock
+    if (midclock <= clock) {
+      if (clock < midclock + mid.length) {
+        return midindex
+      }
+      left = midindex + 1
+    } else {
+      right = midindex - 1
+    }
+    midindex = math.floor((left + right) / 2)
+  }
+  // Always check state before looking for a struct in StructStore
+  // Therefore the case of not finding a struct is unexpected
+  throw error.unexpectedCase()
+}
+
+/**
+ * Expects that id is actually in store. This function throws or is an infinite loop otherwise.
+ *
+ * @param {StructStore} store
+ * @param {ID} id
+ * @return {GC|Item}
+ *
+ * @private
+ * @function
+ */
+export const find = (store, id) => {
+  /**
+   * @type {Array<GC|Item>}
+   */
+  // @ts-ignore
+  const structs = store.clients.get(id.client)
+  return structs[findIndexSS(structs, id.clock)]
+}
+
+/**
+ * Expects that id is actually in store. This function throws or is an infinite loop otherwise.
+ * @private
+ * @function
+ */
+export const getItem = /** @type {function(StructStore,ID):Item} */ (find)
+
+/**
+ * @param {Transaction} transaction
+ * @param {Array<Item|GC>} structs
+ * @param {number} clock
+ */
+export const findIndexCleanStart = (transaction, structs, clock) => {
+  const index = findIndexSS(structs, clock)
+  const struct = structs[index]
+  if (struct.id.clock < clock && struct instanceof Item) {
+    structs.splice(index + 1, 0, splitItem(transaction, struct, clock - struct.id.clock))
+    return index + 1
+  }
+  return index
+}
+
+/**
+ * Expects that id is actually in store. This function throws or is an infinite loop otherwise.
+ *
+ * @param {Transaction} transaction
+ * @param {ID} id
+ * @return {Item}
+ *
+ * @private
+ * @function
+ */
+export const getItemCleanStart = (transaction, id) => {
+  const structs = /** @type {Array<Item>} */ (transaction.doc.store.clients.get(id.client))
+  return structs[findIndexCleanStart(transaction, structs, id.clock)]
+}
+
+/**
+ * Expects that id is actually in store. This function throws or is an infinite loop otherwise.
+ *
+ * @param {Transaction} transaction
+ * @param {StructStore} store
+ * @param {ID} id
+ * @return {Item}
+ *
+ * @private
+ * @function
+ */
+export const getItemCleanEnd = (transaction, store, id) => {
+  /**
+   * @type {Array<Item>}
+   */
+  // @ts-ignore
+  const structs = store.clients.get(id.client)
+  const index = findIndexSS(structs, id.clock)
+  const struct = structs[index]
+  if (id.clock !== struct.id.clock + struct.length - 1 && struct.constructor !== GC) {
+    structs.splice(index + 1, 0, splitItem(transaction, struct, id.clock - struct.id.clock + 1))
+  }
+  return struct
+}
+
+/**
+ * Replace `item` with `newitem` in store
+ * @param {StructStore} store
+ * @param {GC|Item} struct
+ * @param {GC|Item} newStruct
+ *
+ * @private
+ * @function
+ */
+export const replaceStruct = (store, struct, newStruct) => {
+  const structs = /** @type {Array<GC|Item>} */ (store.clients.get(struct.id.client))
+  structs[findIndexSS(structs, struct.id.clock)] = newStruct
+}
+
+/**
+ * Iterate over a range of structs
+ *
+ * @param {Transaction} transaction
+ * @param {Array<Item|GC>} structs
+ * @param {number} clockStart Inclusive start
+ * @param {number} len
+ * @param {function(GC|Item):void} f
+ *
+ * @function
+ */
+export const iterateStructs = (transaction, structs, clockStart, len, f) => {
+  if (len === 0) {
+    return
+  }
+  const clockEnd = clockStart + len
+  let index = findIndexCleanStart(transaction, structs, clockStart)
+  let struct
+  do {
+    struct = structs[index++]
+    if (clockEnd < struct.id.clock + struct.length) {
+      findIndexCleanStart(transaction, structs, clockEnd)
+    }
+    f(struct)
+  } while (index < structs.length && structs[index].id.clock < clockEnd)
+}
--- a/src/utils/Transaction.js
+++ b/src/utils/Transaction.js
@@ -0,0 +1,372 @@
+
+import {
+  getState,
+  writeStructsFromTransaction,
+  writeDeleteSet,
+  DeleteSet,
+  sortAndMergeDeleteSet,
+  getStateVector,
+  findIndexSS,
+  callEventHandlerListeners,
+  Item,
+  generateNewClientId,
+  createID,
+  GC, StructStore, ID, AbstractType, AbstractStruct, YEvent, Doc // eslint-disable-line
+} from '../internals.js'
+
+import * as encoding from 'lib0/encoding.js'
+import * as map from 'lib0/map.js'
+import * as math from 'lib0/math.js'
+import * as set from 'lib0/set.js'
+import * as logging from 'lib0/logging.js'
+import { callAll } from 'lib0/function.js'
+
+/**
+ * A transaction is created for every change on the Yjs model. It is possible
+ * to bundle changes on the Yjs model in a single transaction to
+ * minimize the number on messages sent and the number of observer calls.
+ * If possible the user of this library should bundle as many changes as
+ * possible. Here is an example to illustrate the advantages of bundling:
+ *
+ * @example
+ * const map = y.define('map', YMap)
+ * // Log content when change is triggered
+ * map.observe(() => {
+ *   console.log('change triggered')
+ * })
+ * // Each change on the map type triggers a log message:
+ * map.set('a', 0) // => "change triggered"
+ * map.set('b', 0) // => "change triggered"
+ * // When put in a transaction, it will trigger the log after the transaction:
+ * y.transact(() => {
+ *   map.set('a', 1)
+ *   map.set('b', 1)
+ * }) // => "change triggered"
+ *
+ * @public
+ */
+export class Transaction {
+  /**
+   * @param {Doc} doc
+   * @param {any} origin
+   * @param {boolean} local
+   */
+  constructor (doc, origin, local) {
+    /**
+     * The Yjs instance.
+     * @type {Doc}
+     */
+    this.doc = doc
+    /**
+     * Describes the set of deleted items by ids
+     * @type {DeleteSet}
+     */
+    this.deleteSet = new DeleteSet()
+    /**
+     * Holds the state before the transaction started.
+     * @type {Map<Number,Number>}
+     */
+    this.beforeState = getStateVector(doc.store)
+    /**
+     * Holds the state after the transaction.
+     * @type {Map<Number,Number>}
+     */
+    this.afterState = new Map()
+    /**
+     * All types that were directly modified (property added or child
+     * inserted/deleted). New types are not included in this Set.
+     * Maps from type to parentSubs (`item.parentSub = null` for YArray)
+     * @type {Map<AbstractType<YEvent>,Set<String|null>>}
+     */
+    this.changed = new Map()
+    /**
+     * Stores the events for the types that observe also child elements.
+     * It is mainly used by `observeDeep`.
+     * @type {Map<AbstractType<YEvent>,Array<YEvent>>}
+     */
+    this.changedParentTypes = new Map()
+    /**
+     * @type {Array<AbstractStruct>}
+     */
+    this._mergeStructs = []
+    /**
+     * @type {any}
+     */
+    this.origin = origin
+    /**
+     * Stores meta information on the transaction
+     * @type {Map<any,any>}
+     */
+    this.meta = new Map()
+    /**
+     * Whether this change originates from this doc.
+     * @type {boolean}
+     */
+    this.local = local
+  }
+}
+
+/**
+ * @param {Transaction} transaction
+ */
+export const computeUpdateMessageFromTransaction = transaction => {
+  if (transaction.deleteSet.clients.size === 0 && !map.any(transaction.afterState, (clock, client) => transaction.beforeState.get(client) !== clock)) {
+    return null
+  }
+  const encoder = encoding.createEncoder()
+  sortAndMergeDeleteSet(transaction.deleteSet)
+  writeStructsFromTransaction(encoder, transaction)
+  writeDeleteSet(encoder, transaction.deleteSet)
+  return encoder
+}
+
+/**
+ * @param {Transaction} transaction
+ *
+ * @private
+ * @function
+ */
+export const nextID = transaction => {
+  const y = transaction.doc
+  return createID(y.clientID, getState(y.store, y.clientID))
+}
+
+/**
+ * If `type.parent` was added in current transaction, `type` technically
+ * did not change, it was just added and we should not fire events for `type`.
+ *
+ * @param {Transaction} transaction
+ * @param {AbstractType<YEvent>} type
+ * @param {string|null} parentSub
+ */
+export const addChangedTypeToTransaction = (transaction, type, parentSub) => {
+  const item = type._item
+  if (item === null || (item.id.clock < (transaction.beforeState.get(item.id.client) || 0) && !item.deleted)) {
+    map.setIfUndefined(transaction.changed, type, set.create).add(parentSub)
+  }
+}
+
+/**
+ * @param {Array<AbstractStruct>} structs
+ * @param {number} pos
+ */
+const tryToMergeWithLeft = (structs, pos) => {
+  const left = structs[pos - 1]
+  const right = structs[pos]
+  if (left.deleted === right.deleted && left.constructor === right.constructor) {
+    if (left.mergeWith(right)) {
+      structs.splice(pos, 1)
+      if (right instanceof Item && right.parentSub !== null && /** @type {AbstractType<any>} */ (right.parent)._map.get(right.parentSub) === right) {
+        /** @type {AbstractType<any>} */ (right.parent)._map.set(right.parentSub, /** @type {Item} */ (left))
+      }
+    }
+  }
+}
+
+/**
+ * @param {DeleteSet} ds
+ * @param {StructStore} store
+ * @param {function(Item):boolean} gcFilter
+ */
+const tryGcDeleteSet = (ds, store, gcFilter) => {
+  for (const [client, deleteItems] of ds.clients) {
+    const structs = /** @type {Array<GC|Item>} */ (store.clients.get(client))
+    for (let di = deleteItems.length - 1; di >= 0; di--) {
+      const deleteItem = deleteItems[di]
+      const endDeleteItemClock = deleteItem.clock + deleteItem.len
+      for (
+        let si = findIndexSS(structs, deleteItem.clock), struct = structs[si];
+        si < structs.length && struct.id.clock < endDeleteItemClock;
+        struct = structs[++si]
+      ) {
+        const struct = structs[si]
+        if (deleteItem.clock + deleteItem.len <= struct.id.clock) {
+          break
+        }
+        if (struct instanceof Item && struct.deleted && !struct.keep && gcFilter(struct)) {
+          struct.gc(store, false)
+        }
+      }
+    }
+  }
+}
+
+/**
+ * @param {DeleteSet} ds
+ * @param {StructStore} store
+ */
+const tryMergeDeleteSet = (ds, store) => {
+  // try to merge deleted / gc'd items
+  // merge from right to left for better efficiecy and so we don't miss any merge targets
+  for (const [client, deleteItems] of ds.clients) {
+    const structs = /** @type {Array<GC|Item>} */ (store.clients.get(client))
+    for (let di = deleteItems.length - 1; di >= 0; di--) {
+      const deleteItem = deleteItems[di]
+      // start with merging the item next to the last deleted item
+      const mostRightIndexToCheck = math.min(structs.length - 1, 1 + findIndexSS(structs, deleteItem.clock + deleteItem.len - 1))
+      for (
+        let si = mostRightIndexToCheck, struct = structs[si];
+        si > 0 && struct.id.clock >= deleteItem.clock;
+        struct = structs[--si]
+      ) {
+        tryToMergeWithLeft(structs, si)
+      }
+    }
+  }
+}
+
+/**
+ * @param {DeleteSet} ds
+ * @param {StructStore} store
+ * @param {function(Item):boolean} gcFilter
+ */
+export const tryGc = (ds, store, gcFilter) => {
+  tryGcDeleteSet(ds, store, gcFilter)
+  tryMergeDeleteSet(ds, store)
+}
+
+/**
+ * @param {Array<Transaction>} transactionCleanups
+ * @param {number} i
+ */
+const cleanupTransactions = (transactionCleanups, i) => {
+  if (i < transactionCleanups.length) {
+    const transaction = transactionCleanups[i]
+    const doc = transaction.doc
+    const store = doc.store
+    const ds = transaction.deleteSet
+    const mergeStructs = transaction._mergeStructs
+    try {
+      sortAndMergeDeleteSet(ds)
+      transaction.afterState = getStateVector(transaction.doc.store)
+      doc._transaction = null
+      doc.emit('beforeObserverCalls', [transaction, doc])
+      /**
+       * An array of event callbacks.
+       *
+       * Each callback is called even if the other ones throw errors.
+       *
+       * @type {Array<function():void>}
+       */
+      const fs = []
+      // observe events on changed types
+      transaction.changed.forEach((subs, itemtype) =>
+        fs.push(() => {
+          if (itemtype._item === null || !itemtype._item.deleted) {
+            itemtype._callObserver(transaction, subs)
+          }
+        })
+      )
+      fs.push(() => {
+        // deep observe events
+        transaction.changedParentTypes.forEach((events, type) =>
+          fs.push(() => {
+            // We need to think about the possibility that the user transforms the
+            // Y.Doc in the event.
+            if (type._item === null || !type._item.deleted) {
+              events = events
+                .filter(event =>
+                  event.target._item === null || !event.target._item.deleted
+                )
+              events
+                .forEach(event => {
+                  event.currentTarget = type
+                })
+              // We don't need to check for events.length
+              // because we know it has at least one element
+              callEventHandlerListeners(type._dEH, events, transaction)
+            }
+          })
+        )
+        fs.push(() => doc.emit('afterTransaction', [transaction, doc]))
+      })
+      callAll(fs, [])
+    } finally {
+      // Replace deleted items with ItemDeleted / GC.
+      // This is where content is actually remove from the Yjs Doc.
+      if (doc.gc) {
+        tryGcDeleteSet(ds, store, doc.gcFilter)
+      }
+      tryMergeDeleteSet(ds, store)
+
+      // on all affected store.clients props, try to merge
+      for (const [client, clock] of transaction.afterState) {
+        const beforeClock = transaction.beforeState.get(client) || 0
+        if (beforeClock !== clock) {
+          const structs = /** @type {Array<GC|Item>} */ (store.clients.get(client))
+          // we iterate from right to left so we can safely remove entries
+          const firstChangePos = math.max(findIndexSS(structs, beforeClock), 1)
+          for (let i = structs.length - 1; i >= firstChangePos; i--) {
+            tryToMergeWithLeft(structs, i)
+          }
+        }
+      }
+      // try to merge mergeStructs
+      // @todo: it makes more sense to transform mergeStructs to a DS, sort it, and merge from right to left
+      //        but at the moment DS does not handle duplicates
+      for (let i = 0; i < mergeStructs.length; i++) {
+        const { client, clock } = mergeStructs[i].id
+        const structs = /** @type {Array<GC|Item>} */ (store.clients.get(client))
+        const replacedStructPos = findIndexSS(structs, clock)
+        if (replacedStructPos + 1 < structs.length) {
+          tryToMergeWithLeft(structs, replacedStructPos + 1)
+        }
+        if (replacedStructPos > 0) {
+          tryToMergeWithLeft(structs, replacedStructPos)
+        }
+      }
+      if (!transaction.local && transaction.afterState.get(doc.clientID) !== transaction.beforeState.get(doc.clientID)) {
+        doc.clientID = generateNewClientId()
+        logging.print(logging.ORANGE, logging.BOLD, '[yjs] ', logging.UNBOLD, logging.RED, 'Changed the client-id because another client seems to be using it.')
+      }
+      // @todo Merge all the transactions into one and provide send the data as a single update message
+      doc.emit('afterTransactionCleanup', [transaction, doc])
+      if (doc._observers.has('update')) {
+        const updateMessage = computeUpdateMessageFromTransaction(transaction)
+        if (updateMessage !== null) {
+          doc.emit('update', [encoding.toUint8Array(updateMessage), transaction.origin, doc])
+        }
+      }
+      if (transactionCleanups.length <= i + 1) {
+        doc._transactionCleanups = []
+      } else {
+        cleanupTransactions(transactionCleanups, i + 1)
+      }
+    }
+  }
+}
+
+/**
+ * Implements the functionality of `y.transact(()=>{..})`
+ *
+ * @param {Doc} doc
+ * @param {function(Transaction):void} f
+ * @param {any} [origin=true]
+ *
+ * @function
+ */
+export const transact = (doc, f, origin = null, local = true) => {
+  const transactionCleanups = doc._transactionCleanups
+  let initialCall = false
+  if (doc._transaction === null) {
+    initialCall = true
+    doc._transaction = new Transaction(doc, origin, local)
+    transactionCleanups.push(doc._transaction)
+    doc.emit('beforeTransaction', [doc._transaction, doc])
+  }
+  try {
+    f(doc._transaction)
+  } finally {
+    if (initialCall && transactionCleanups[0] === doc._transaction) {
+      // The first transaction ended, now process observer calls.
+      // Observer call may create new transactions for which we need to call the observers and do cleanup.
+      // We don't want to nest these calls, so we execute these calls one after
+      // another.
+      // Also we need to ensure that all cleanups are called, even if the
+      // observes throw errors.
+      // This file is full of hacky try {} finally {} blocks to ensure that an
+      // event can throw errors and also that the cleanup is called.
+      cleanupTransactions(transactionCleanups, 0)
+    }
+  }
+}
--- a/src/utils/UndoManager.js
+++ b/src/utils/UndoManager.js
@@ -0,0 +1,293 @@
+import {
+  mergeDeleteSets,
+  iterateDeletedStructs,
+  keepItem,
+  transact,
+  createID,
+  redoItem,
+  iterateStructs,
+  isParentOf,
+  followRedone,
+  getItemCleanStart,
+  getState,
+  ID, Transaction, Doc, Item, GC, DeleteSet, AbstractType // eslint-disable-line
+} from '../internals.js'
+
+import * as time from 'lib0/time.js'
+import { Observable } from 'lib0/observable.js'
+
+class StackItem {
+  /**
+   * @param {DeleteSet} ds
+   * @param {Map<number,number>} beforeState
+   * @param {Map<number,number>} afterState
+   */
+  constructor (ds, beforeState, afterState) {
+    this.ds = ds
+    this.beforeState = beforeState
+    this.afterState = afterState
+    /**
+     * Use this to save and restore metadata like selection range
+     */
+    this.meta = new Map()
+  }
+}
+
+/**
+ * @param {UndoManager} undoManager
+ * @param {Array<StackItem>} stack
+ * @param {string} eventType
+ * @return {StackItem?}
+ */
+const popStackItem = (undoManager, stack, eventType) => {
+  /**
+   * Whether a change happened
+   * @type {StackItem?}
+   */
+  let result = null
+  const doc = undoManager.doc
+  const scope = undoManager.scope
+  transact(doc, transaction => {
+    while (stack.length > 0 && result === null) {
+      const store = doc.store
+      const stackItem = /** @type {StackItem} */ (stack.pop())
+      /**
+       * @type {Set<Item>}
+       */
+      const itemsToRedo = new Set()
+      /**
+       * @type {Array<Item>}
+       */
+      const itemsToDelete = []
+      let performedChange = false
+      stackItem.afterState.forEach((endClock, client) => {
+        const startClock = stackItem.beforeState.get(client) || 0
+        const len = endClock - startClock
+        // @todo iterateStructs should not need the structs parameter
+        const structs = /** @type {Array<GC|Item>} */ (store.clients.get(client))
+        if (startClock !== endClock) {
+          // make sure structs don't overlap with the range of created operations [stackItem.start, stackItem.start + stackItem.end)
+          // this must be executed before deleted structs are iterated.
+          getItemCleanStart(transaction, createID(client, startClock))
+          if (endClock < getState(doc.store, client)) {
+            getItemCleanStart(transaction, createID(client, endClock))
+          }
+          iterateStructs(transaction, structs, startClock, len, struct => {
+            if (struct instanceof Item) {
+              if (struct.redone !== null) {
+                let { item, diff } = followRedone(store, struct.id)
+                if (diff > 0) {
+                  item = getItemCleanStart(transaction, createID(item.id.client, item.id.clock + diff))
+                }
+                if (item.length > len) {
+                  getItemCleanStart(transaction, createID(item.id.client, endClock))
+                }
+                struct = item
+              }
+              if (!struct.deleted && scope.some(type => isParentOf(type, /** @type {Item} */ (struct)))) {
+                itemsToDelete.push(struct)
+              }
+            }
+          })
+        }
+      })
+      iterateDeletedStructs(transaction, stackItem.ds, struct => {
+        const id = struct.id
+        const clock = id.clock
+        const client = id.client
+        const startClock = stackItem.beforeState.get(client) || 0
+        const endClock = stackItem.afterState.get(client) || 0
+        if (
+          struct instanceof Item &&
+          scope.some(type => isParentOf(type, struct)) &&
+          // Never redo structs in [stackItem.start, stackItem.start + stackItem.end) because they were created and deleted in the same capture interval.
+          !(clock >= startClock && clock < endClock)
+        ) {
+          itemsToRedo.add(struct)
+        }
+      })
+      itemsToRedo.forEach(struct => {
+        performedChange = redoItem(transaction, struct, itemsToRedo) !== null || performedChange
+      })
+      // We want to delete in reverse order so that children are deleted before
+      // parents, so we have more information available when items are filtered.
+      for (let i = itemsToDelete.length - 1; i >= 0; i--) {
+        const item = itemsToDelete[i]
+        if (undoManager.deleteFilter(item)) {
+          item.delete(transaction)
+          performedChange = true
+        }
+      }
+      result = stackItem
+      if (result != null) {
+        undoManager.emit('stack-item-popped', [{ stackItem: result, type: eventType }, undoManager])
+      }
+    }
+  }, undoManager)
+  return result
+}
+
+/**
+ * @typedef {Object} UndoManagerOptions
+ * @property {number} [UndoManagerOptions.captureTimeout=500]
+ * @property {function(Item):boolean} [UndoManagerOptions.deleteFilter=()=>true] Sometimes
+ * it is necessary to filter whan an Undo/Redo operation can delete. If this
+ * filter returns false, the type/item won't be deleted even it is in the
+ * undo/redo scope.
+ * @property {Set<any>} [UndoManagerOptions.trackedOrigins=new Set([null])]
+ */
+
+/**
+ * Fires 'stack-item-added' event when a stack item was added to either the undo- or
+ * the redo-stack. You may store additional stack information via the
+ * metadata property on `event.stackItem.meta` (it is a `Map` of metadata properties).
+ * Fires 'stack-item-popped' event when a stack item was popped from either the
+ * undo- or the redo-stack. You may restore the saved stack information from `event.stackItem.meta`.
+ *
+ * @extends {Observable<'stack-item-added'|'stack-item-popped'>}
+ */
+export class UndoManager extends Observable {
+  /**
+   * @param {AbstractType<any>|Array<AbstractType<any>>} typeScope Accepts either a single type, or an array of types
+   * @param {UndoManagerOptions} options
+   */
+  constructor (typeScope, { captureTimeout, deleteFilter = () => true, trackedOrigins = new Set([null]) } = {}) {
+    if (captureTimeout == null) {
+      captureTimeout = 500
+    }
+    super()
+    this.scope = typeScope instanceof Array ? typeScope : [typeScope]
+    this.deleteFilter = deleteFilter
+    trackedOrigins.add(this)
+    this.trackedOrigins = trackedOrigins
+    /**
+     * @type {Array<StackItem>}
+     */
+    this.undoStack = []
+    /**
+     * @type {Array<StackItem>}
+     */
+    this.redoStack = []
+    /**
+     * Whether the client is currently undoing (calling UndoManager.undo)
+     *
+     * @type {boolean}
+     */
+    this.undoing = false
+    this.redoing = false
+    this.doc = /** @type {Doc} */ (this.scope[0].doc)
+    this.lastChange = 0
+    this.doc.on('afterTransaction', /** @param {Transaction} transaction */ transaction => {
+      // Only track certain transactions
+      if (!this.scope.some(type => transaction.changedParentTypes.has(type)) || (!this.trackedOrigins.has(transaction.origin) && (!transaction.origin || !this.trackedOrigins.has(transaction.origin.constructor)))) {
+        return
+      }
+      const undoing = this.undoing
+      const redoing = this.redoing
+      const stack = undoing ? this.redoStack : this.undoStack
+      if (undoing) {
+        this.stopCapturing() // next undo should not be appended to last stack item
+      } else if (!redoing) {
+        // neither undoing nor redoing: delete redoStack
+        this.redoStack = []
+      }
+      const beforeState = transaction.beforeState
+      const afterState = transaction.afterState
+      const now = time.getUnixTime()
+      if (now - this.lastChange < captureTimeout && stack.length > 0 && !undoing && !redoing) {
+        // append change to last stack op
+        const lastOp = stack[stack.length - 1]
+        lastOp.ds = mergeDeleteSets([lastOp.ds, transaction.deleteSet])
+        lastOp.afterState = afterState
+      } else {
+        // create a new stack op
+        stack.push(new StackItem(transaction.deleteSet, beforeState, afterState))
+      }
+      if (!undoing && !redoing) {
+        this.lastChange = now
+      }
+      // make sure that deleted structs are not gc'd
+      iterateDeletedStructs(transaction, transaction.deleteSet, /** @param {Item|GC} item */ item => {
+        if (item instanceof Item && this.scope.some(type => isParentOf(type, item))) {
+          keepItem(item, true)
+        }
+      })
+      this.emit('stack-item-added', [{ stackItem: stack[stack.length - 1], origin: transaction.origin, type: undoing ? 'redo' : 'undo' }, this])
+    })
+  }
+
+  clear () {
+    this.doc.transact(transaction => {
+      /**
+       * @param {StackItem} stackItem
+       */
+      const clearItem = stackItem => {
+        iterateDeletedStructs(transaction, stackItem.ds, item => {
+          if (item instanceof Item && this.scope.some(type => isParentOf(type, item))) {
+            keepItem(item, false)
+          }
+        })
+      }
+      this.undoStack.forEach(clearItem)
+      this.redoStack.forEach(clearItem)
+    })
+    this.undoStack = []
+    this.redoStack = []
+  }
+
+  /**
+   * UndoManager merges Undo-StackItem if they are created within time-gap
+   * smaller than `options.captureTimeout`. Call `um.stopCapturing()` so that the next
+   * StackItem won't be merged.
+   *
+   *
+   * @example
+   *     // without stopCapturing
+   *     ytext.insert(0, 'a')
+   *     ytext.insert(1, 'b')
+   *     um.undo()
+   *     ytext.toString() // => '' (note that 'ab' was removed)
+   *     // with stopCapturing
+   *     ytext.insert(0, 'a')
+   *     um.stopCapturing()
+   *     ytext.insert(0, 'b')
+   *     um.undo()
+   *     ytext.toString() // => 'a' (note that only 'b' was removed)
+   *
+   */
+  stopCapturing () {
+    this.lastChange = 0
+  }
+
+  /**
+   * Undo last changes on type.
+   *
+   * @return {StackItem?} Returns StackItem if a change was applied
+   */
+  undo () {
+    this.undoing = true
+    let res
+    try {
+      res = popStackItem(this, this.undoStack, 'undo')
+    } finally {
+      this.undoing = false
+    }
+    return res
+  }
+
+  /**
+   * Redo last undo operation.
+   *
+   * @return {StackItem?} Returns StackItem if a change was applied
+   */
+  redo () {
+    this.redoing = true
+    let res
+    try {
+      res = popStackItem(this, this.redoStack, 'redo')
+    } finally {
+      this.redoing = false
+    }
+    return res
+  }
+}
--- a/src/utils/YEvent.js
+++ b/src/utils/YEvent.js
@@ -0,0 +1,226 @@
+
+import {
+  isDeleted,
+  Item, AbstractType, Transaction, AbstractStruct // eslint-disable-line
+} from '../internals.js'
+
+import * as set from 'lib0/set.js'
+import * as array from 'lib0/array.js'
+
+/**
+ * YEvent describes the changes on a YType.
+ */
+export class YEvent {
+  /**
+   * @param {AbstractType<any>} target The changed type.
+   * @param {Transaction} transaction
+   */
+  constructor (target, transaction) {
+    /**
+     * The type on which this event was created on.
+     * @type {AbstractType<any>}
+     */
+    this.target = target
+    /**
+     * The current target on which the observe callback is called.
+     * @type {AbstractType<any>}
+     */
+    this.currentTarget = target
+    /**
+     * The transaction that triggered this event.
+     * @type {Transaction}
+     */
+    this.transaction = transaction
+    /**
+     * @type {Object|null}
+     */
+    this._changes = null
+  }
+
+  /**
+   * Computes the path from `y` to the changed type.
+   *
+   * The following property holds:
+   * @example
+   *   let type = y
+   *   event.path.forEach(dir => {
+   *     type = type.get(dir)
+   *   })
+   *   type === event.target // => true
+   */
+  get path () {
+    // @ts-ignore _item is defined because target is integrated
+    return getPathTo(this.currentTarget, this.target)
+  }
+
+  /**
+   * Check if a struct is deleted by this event.
+   *
+   * In contrast to change.deleted, this method also returns true if the struct was added and then deleted.
+   *
+   * @param {AbstractStruct} struct
+   * @return {boolean}
+   */
+  deletes (struct) {
+    return isDeleted(this.transaction.deleteSet, struct.id)
+  }
+
+  /**
+   * Check if a struct is added by this event.
+   *
+   * In contrast to change.deleted, this method also returns true if the struct was added and then deleted.
+   *
+   * @param {AbstractStruct} struct
+   * @return {boolean}
+   */
+  adds (struct) {
+    return struct.id.clock >= (this.transaction.beforeState.get(struct.id.client) || 0)
+  }
+
+  /**
+   * @return {{added:Set<Item>,deleted:Set<Item>,delta:Array<{insert:Array<any>}|{delete:number}|{retain:number}>}}
+   */
+  get changes () {
+    let changes = this._changes
+    if (changes === null) {
+      const target = this.target
+      const added = set.create()
+      const deleted = set.create()
+      /**
+       * @type {Array<{insert:Array<any>}|{delete:number}|{retain:number}>}
+       */
+      const delta = []
+      /**
+       * @type {Map<string,{ action: 'add' | 'update' | 'delete', oldValue: any}>}
+       */
+      const keys = new Map()
+      changes = {
+        added, deleted, delta, keys
+      }
+      const changed = /** @type Set<string|null> */ (this.transaction.changed.get(target))
+      if (changed.has(null)) {
+        /**
+         * @type {any}
+         */
+        let lastOp = null
+        const packOp = () => {
+          if (lastOp) {
+            delta.push(lastOp)
+          }
+        }
+        for (let item = target._start; item !== null; item = item.right) {
+          if (item.deleted) {
+            if (this.deletes(item) && !this.adds(item)) {
+              if (lastOp === null || lastOp.delete === undefined) {
+                packOp()
+                lastOp = { delete: 0 }
+              }
+              lastOp.delete += item.length
+              deleted.add(item)
+            } // else nop
+          } else {
+            if (this.adds(item)) {
+              if (lastOp === null || lastOp.insert === undefined) {
+                packOp()
+                lastOp = { insert: [] }
+              }
+              lastOp.insert = lastOp.insert.concat(item.content.getContent())
+              added.add(item)
+            } else {
+              if (lastOp === null || lastOp.retain === undefined) {
+                packOp()
+                lastOp = { retain: 0 }
+              }
+              lastOp.retain += item.length
+            }
+          }
+        }
+        if (lastOp !== null && lastOp.retain === undefined) {
+          packOp()
+        }
+      }
+      changed.forEach(key => {
+        if (key !== null) {
+          const item = /** @type {Item} */ (target._map.get(key))
+          /**
+           * @type {'delete' | 'add' | 'update'}
+           */
+          let action
+          let oldValue
+          if (this.adds(item)) {
+            let prev = item.left
+            while (prev !== null && this.adds(prev)) {
+              prev = prev.left
+            }
+            if (this.deletes(item)) {
+              if (prev !== null && this.deletes(prev)) {
+                action = 'delete'
+                oldValue = array.last(prev.content.getContent())
+              } else {
+                return
+              }
+            } else {
+              if (prev !== null && this.deletes(prev)) {
+                action = 'update'
+                oldValue = array.last(prev.content.getContent())
+              } else {
+                action = 'add'
+                oldValue = undefined
+              }
+            }
+          } else {
+            if (this.deletes(item)) {
+              action = 'delete'
+              oldValue = array.last(/** @type {Item} */ item.content.getContent())
+            } else {
+              return // nop
+            }
+          }
+          keys.set(key, { action, oldValue })
+        }
+      })
+      this._changes = changes
+    }
+    return /** @type {any} */ (changes)
+  }
+}
+
+/**
+ * Compute the path from this type to the specified target.
+ *
+ * @example
+ *   // `child` should be accessible via `type.get(path[0]).get(path[1])..`
+ *   const path = type.getPathTo(child)
+ *   // assuming `type instanceof YArray`
+ *   console.log(path) // might look like => [2, 'key1']
+ *   child === type.get(path[0]).get(path[1])
+ *
+ * @param {AbstractType<any>} parent
+ * @param {AbstractType<any>} child target
+ * @return {Array<string|number>} Path to the target
+ *
+ * @private
+ * @function
+ */
+const getPathTo = (parent, child) => {
+  const path = []
+  while (child._item !== null && child !== parent) {
+    if (child._item.parentSub !== null) {
+      // parent is map-ish
+      path.unshift(child._item.parentSub)
+    } else {
+      // parent is array-ish
+      let i = 0
+      let c = /** @type {AbstractType<any>} */ (child._item.parent)._start
+      while (c !== child._item && c !== null) {
+        if (!c.deleted) {
+          i++
+        }
+        c = c.right
+      }
+      path.unshift(i)
+    }
+    child = /** @type {AbstractType<any>} */ (child._item.parent)
+  }
+  return path
+}
--- a/src/utils/encoding.js
+++ b/src/utils/encoding.js
@@ -0,0 +1,426 @@
+
+/**
+ * @module encoding
+ *
+ * We use the first five bits in the info flag for determining the type of the struct.
+ *
+ * 0: GC
+ * 1: Item with Deleted content
+ * 2: Item with JSON content
+ * 3: Item with Binary content
+ * 4: Item with String content
+ * 5: Item with Embed content (for richtext content)
+ * 6: Item with Format content (a formatting marker for richtext content)
+ * 7: Item with Type
+ */
+
+import {
+  findIndexSS,
+  writeID,
+  readID,
+  getState,
+  createID,
+  getStateVector,
+  readAndApplyDeleteSet,
+  writeDeleteSet,
+  createDeleteSetFromStructStore,
+  transact,
+  readItem,
+  Doc, Transaction, GC, Item, StructStore, ID // eslint-disable-line
+} from '../internals.js'
+
+import * as encoding from 'lib0/encoding.js'
+import * as decoding from 'lib0/decoding.js'
+import * as binary from 'lib0/binary.js'
+
+/**
+ * @param {encoding.Encoder} encoder
+ * @param {Array<GC|Item>} structs All structs by `client`
+ * @param {number} client
+ * @param {number} clock write structs starting with `ID(client,clock)`
+ *
+ * @function
+ */
+const writeStructs = (encoder, structs, client, clock) => {
+  // write first id
+  const startNewStructs = findIndexSS(structs, clock)
+  // write # encoded structs
+  encoding.writeVarUint(encoder, structs.length - startNewStructs)
+  writeID(encoder, createID(client, clock))
+  const firstStruct = structs[startNewStructs]
+  // write first struct with an offset
+  firstStruct.write(encoder, clock - firstStruct.id.clock)
+  for (let i = startNewStructs + 1; i < structs.length; i++) {
+    structs[i].write(encoder, 0)
+  }
+}
+
+/**
+ * @param {encoding.Encoder} encoder
+ * @param {StructStore} store
+ * @param {Map<number,number>} _sm
+ *
+ * @private
+ * @function
+ */
+export const writeClientsStructs = (encoder, store, _sm) => {
+  // we filter all valid _sm entries into sm
+  const sm = new Map()
+  _sm.forEach((clock, client) => {
+    // only write if new structs are available
+    if (getState(store, client) > clock) {
+      sm.set(client, clock)
+    }
+  })
+  getStateVector(store).forEach((clock, client) => {
+    if (!_sm.has(client)) {
+      sm.set(client, 0)
+    }
+  })
+  // write # states that were updated
+  encoding.writeVarUint(encoder, sm.size)
+  // Write items with higher client ids first
+  // This heavily improves the conflict algorithm.
+  Array.from(sm.entries()).sort((a, b) => b[0] - a[0]).forEach(([client, clock]) => {
+    // @ts-ignore
+    writeStructs(encoder, store.clients.get(client), client, clock)
+  })
+}
+
+/**
+ * @param {decoding.Decoder} decoder The decoder object to read data from.
+ * @param {Map<number,Array<GC|Item>>} clientRefs
+ * @param {Doc} doc
+ * @return {Map<number,Array<GC|Item>>}
+ *
+ * @private
+ * @function
+ */
+export const readClientsStructRefs = (decoder, clientRefs, doc) => {
+  const numOfStateUpdates = decoding.readVarUint(decoder)
+  for (let i = 0; i < numOfStateUpdates; i++) {
+    const numberOfStructs = decoding.readVarUint(decoder)
+    /**
+     * @type {Array<GC|Item>}
+     */
+    const refs = []
+    let { client, clock } = readID(decoder)
+    let info, struct
+    clientRefs.set(client, refs)
+    for (let i = 0; i < numberOfStructs; i++) {
+      info = decoding.readUint8(decoder)
+      struct = (binary.BITS5 & info) === 0 ? new GC(createID(client, clock), decoding.readVarUint(decoder)) : readItem(decoder, createID(client, clock), info, doc)
+      refs.push(struct)
+      clock += struct.length
+    }
+  }
+  return clientRefs
+}
+
+/**
+ * Resume computing structs generated by struct readers.
+ *
+ * While there is something to do, we integrate structs in this order
+ * 1. top element on stack, if stack is not empty
+ * 2. next element from current struct reader (if empty, use next struct reader)
+ *
+ * If struct causally depends on another struct (ref.missing), we put next reader of
+ * `ref.id.client` on top of stack.
+ *
+ * At some point we find a struct that has no causal dependencies,
+ * then we start emptying the stack.
+ *
+ * It is not possible to have circles: i.e. struct1 (from client1) depends on struct2 (from client2)
+ * depends on struct3 (from client1). Therefore the max stack size is eqaul to `structReaders.length`.
+ *
+ * This method is implemented in a way so that we can resume computation if this update
+ * causally depends on another update.
+ *
+ * @param {Transaction} transaction
+ * @param {StructStore} store
+ *
+ * @private
+ * @function
+ */
+const resumeStructIntegration = (transaction, store) => {
+  const stack = store.pendingStack
+  const clientsStructRefs = store.pendingClientsStructRefs
+  // sort them so that we take the higher id first, in case of conflicts the lower id will probably not conflict with the id from the higher user.
+  const clientsStructRefsIds = Array.from(clientsStructRefs.keys()).sort((a, b) => a - b)
+  let curStructsTarget = /** @type {{i:number,refs:Array<GC|Item>}} */ (clientsStructRefs.get(clientsStructRefsIds[clientsStructRefsIds.length - 1]))
+  // iterate over all struct readers until we are done
+  while (stack.length !== 0 || clientsStructRefsIds.length > 0) {
+    if (stack.length === 0) {
+      // take any first struct from clientsStructRefs and put it on the stack
+      if (curStructsTarget.i < curStructsTarget.refs.length) {
+        stack.push(curStructsTarget.refs[curStructsTarget.i++])
+      } else {
+        clientsStructRefsIds.pop()
+        if (clientsStructRefsIds.length > 0) {
+          curStructsTarget = /** @type {{i:number,refs:Array<GC|Item>}} */ (clientsStructRefs.get(clientsStructRefsIds[clientsStructRefsIds.length - 1]))
+        }
+        continue
+      }
+    }
+    const ref = stack[stack.length - 1]
+    const refID = ref.id
+    const client = refID.client
+    const refClock = refID.clock
+    const localClock = getState(store, client)
+    const offset = refClock < localClock ? localClock - refClock : 0
+    if (refClock + offset !== localClock) {
+      // A previous message from this client is missing
+      // check if there is a pending structRef with a smaller clock and switch them
+      const structRefs = clientsStructRefs.get(client) || { refs: [], i: 0 }
+      if (structRefs.refs.length !== structRefs.i) {
+        const r = structRefs.refs[structRefs.i]
+        if (r.id.clock < refClock) {
+          // put ref with smaller clock on stack instead and continue
+          structRefs.refs[structRefs.i] = ref
+          stack[stack.length - 1] = r
+          // sort the set because this approach might bring the list out of order
+          structRefs.refs = structRefs.refs.slice(structRefs.i).sort((r1, r2) => r1.id.clock - r2.id.clock)
+          structRefs.i = 0
+          continue
+        }
+      }
+      // wait until missing struct is available
+      return
+    }
+    const missing = ref.getMissing(transaction, store)
+    if (missing !== null) {
+      // get the struct reader that has the missing struct
+      const structRefs = clientsStructRefs.get(missing) || { refs: [], i: 0 }
+      if (structRefs.refs.length === structRefs.i) {
+        // This update message causally depends on another update message.
+        return
+      }
+      stack.push(structRefs.refs[structRefs.i++])
+    } else {
+      if (offset < ref.length) {
+        ref.integrate(transaction, offset)
+      }
+      stack.pop()
+    }
+  }
+  store.pendingClientsStructRefs.clear()
+}
+
+/**
+ * @param {Transaction} transaction
+ * @param {StructStore} store
+ *
+ * @private
+ * @function
+ */
+export const tryResumePendingDeleteReaders = (transaction, store) => {
+  const pendingReaders = store.pendingDeleteReaders
+  store.pendingDeleteReaders = []
+  for (let i = 0; i < pendingReaders.length; i++) {
+    readAndApplyDeleteSet(pendingReaders[i], transaction, store)
+  }
+}
+
+/**
+ * @param {encoding.Encoder} encoder
+ * @param {Transaction} transaction
+ *
+ * @private
+ * @function
+ */
+export const writeStructsFromTransaction = (encoder, transaction) => writeClientsStructs(encoder, transaction.doc.store, transaction.beforeState)
+
+/**
+ * @param {StructStore} store
+ * @param {Map<number, Array<GC|Item>>} clientsStructsRefs
+ *
+ * @private
+ * @function
+ */
+const mergeReadStructsIntoPendingReads = (store, clientsStructsRefs) => {
+  const pendingClientsStructRefs = store.pendingClientsStructRefs
+  for (const [client, structRefs] of clientsStructsRefs) {
+    const pendingStructRefs = pendingClientsStructRefs.get(client)
+    if (pendingStructRefs === undefined) {
+      pendingClientsStructRefs.set(client, { refs: structRefs, i: 0 })
+    } else {
+      // merge into existing structRefs
+      const merged = pendingStructRefs.i > 0 ? pendingStructRefs.refs.slice(pendingStructRefs.i) : pendingStructRefs.refs
+      for (let i = 0; i < structRefs.length; i++) {
+        merged.push(structRefs[i])
+      }
+      pendingStructRefs.i = 0
+      pendingStructRefs.refs = merged.sort((r1, r2) => r1.id.clock - r2.id.clock)
+    }
+  }
+}
+
+/**
+ * @param {Map<number,{refs:Array<GC|Item>,i:number}>} pendingClientsStructRefs
+ */
+const cleanupPendingStructs = pendingClientsStructRefs => {
+  // cleanup pendingClientsStructs if not fully finished
+  for (const [client, refs] of pendingClientsStructRefs) {
+    if (refs.i === refs.refs.length) {
+      pendingClientsStructRefs.delete(client)
+    } else {
+      refs.refs.splice(0, refs.i)
+      refs.i = 0
+    }
+  }
+}
+
+/**
+ * Read the next Item in a Decoder and fill this Item with the read data.
+ *
+ * This is called when data is received from a remote peer.
+ *
+ * @param {decoding.Decoder} decoder The decoder object to read data from.
+ * @param {Transaction} transaction
+ * @param {StructStore} store
+ *
+ * @private
+ * @function
+ */
+export const readStructs = (decoder, transaction, store) => {
+  const clientsStructRefs = new Map()
+  readClientsStructRefs(decoder, clientsStructRefs, transaction.doc)
+  mergeReadStructsIntoPendingReads(store, clientsStructRefs)
+  resumeStructIntegration(transaction, store)
+  cleanupPendingStructs(store.pendingClientsStructRefs)
+  tryResumePendingDeleteReaders(transaction, store)
+}
+
+/**
+ * Read and apply a document update.
+ *
+ * This function has the same effect as `applyUpdate` but accepts an decoder.
+ *
+ * @param {decoding.Decoder} decoder
+ * @param {Doc} ydoc
+ * @param {any} [transactionOrigin] This will be stored on `transaction.origin` and `.on('update', (update, origin))`
+ *
+ * @function
+ */
+export const readUpdate = (decoder, ydoc, transactionOrigin) =>
+  transact(ydoc, transaction => {
+    readStructs(decoder, transaction, ydoc.store)
+    readAndApplyDeleteSet(decoder, transaction, ydoc.store)
+  }, transactionOrigin, false)
+
+/**
+ * Apply a document update created by, for example, `y.on('update', update => ..)` or `update = encodeStateAsUpdate()`.
+ *
+ * This function has the same effect as `readUpdate` but accepts an Uint8Array instead of a Decoder.
+ *
+ * @param {Doc} ydoc
+ * @param {Uint8Array} update
+ * @param {any} [transactionOrigin] This will be stored on `transaction.origin` and `.on('update', (update, origin))`
+ *
+ * @function
+ */
+export const applyUpdate = (ydoc, update, transactionOrigin) =>
+  readUpdate(decoding.createDecoder(update), ydoc, transactionOrigin)
+
+/**
+ * Write all the document as a single update message. If you specify the state of the remote client (`targetStateVector`) it will
+ * only write the operations that are missing.
+ *
+ * @param {encoding.Encoder} encoder
+ * @param {Doc} doc
+ * @param {Map<number,number>} [targetStateVector] The state of the target that receives the update. Leave empty to write all known structs
+ *
+ * @function
+ */
+export const writeStateAsUpdate = (encoder, doc, targetStateVector = new Map()) => {
+  writeClientsStructs(encoder, doc.store, targetStateVector)
+  writeDeleteSet(encoder, createDeleteSetFromStructStore(doc.store))
+}
+
+/**
+ * Write all the document as a single update message that can be applied on the remote document. If you specify the state of the remote client (`targetState`) it will
+ * only write the operations that are missing.
+ *
+ * Use `writeStateAsUpdate` instead if you are working with lib0/encoding.js#Encoder
+ *
+ * @param {Doc} doc
+ * @param {Uint8Array} [encodedTargetStateVector] The state of the target that receives the update. Leave empty to write all known structs
+ * @return {Uint8Array}
+ *
+ * @function
+ */
+export const encodeStateAsUpdate = (doc, encodedTargetStateVector) => {
+  const encoder = encoding.createEncoder()
+  const targetStateVector = encodedTargetStateVector == null ? new Map() : decodeStateVector(encodedTargetStateVector)
+  writeStateAsUpdate(encoder, doc, targetStateVector)
+  return encoding.toUint8Array(encoder)
+}
+
+/**
+ * Read state vector from Decoder and return as Map
+ *
+ * @param {decoding.Decoder} decoder
+ * @return {Map<number,number>} Maps `client` to the number next expected `clock` from that client.
+ *
+ * @function
+ */
+export const readStateVector = decoder => {
+  const ss = new Map()
+  const ssLength = decoding.readVarUint(decoder)
+  for (let i = 0; i < ssLength; i++) {
+    const client = decoding.readVarUint(decoder)
+    const clock = decoding.readVarUint(decoder)
+    ss.set(client, clock)
+  }
+  return ss
+}
+
+/**
+ * Read decodedState and return State as Map.
+ *
+ * @param {Uint8Array} decodedState
+ * @return {Map<number,number>} Maps `client` to the number next expected `clock` from that client.
+ *
+ * @function
+ */
+export const decodeStateVector = decodedState => readStateVector(decoding.createDecoder(decodedState))
+
+/**
+ * Write State Vector to `lib0/encoding.js#Encoder`.
+ *
+ * @param {encoding.Encoder} encoder
+ * @param {Map<number,number>} sv
+ * @function
+ */
+export const writeStateVector = (encoder, sv) => {
+  encoding.writeVarUint(encoder, sv.size)
+  sv.forEach((clock, client) => {
+    encoding.writeVarUint(encoder, client)
+    encoding.writeVarUint(encoder, clock)
+  })
+  return encoder
+}
+
+/**
+ * Write State Vector to `lib0/encoding.js#Encoder`.
+ *
+ * @param {encoding.Encoder} encoder
+ * @param {Doc} doc
+ *
+ * @function
+ */
+export const writeDocumentStateVector = (encoder, doc) => writeStateVector(encoder, getStateVector(doc.store))
+
+/**
+ * Encode State as Uint8Array.
+ *
+ * @param {Doc} doc
+ * @return {Uint8Array}
+ *
+ * @function
+ */
+export const encodeStateVector = doc => {
+  const encoder = encoding.createEncoder()
+  writeDocumentStateVector(encoder, doc)
+  return encoding.toUint8Array(encoder)
+}
--- a/src/utils/isParentOf.js
+++ b/src/utils/isParentOf.js
@@ -0,0 +1,22 @@
+
+import { AbstractType, Item } from '../internals.js' // eslint-disable-line
+
+/**
+ * Check if `parent` is a parent of `child`.
+ *
+ * @param {AbstractType<any>} parent
+ * @param {Item|null} child
+ * @return {Boolean} Whether `parent` is a parent of `child`.
+ *
+ * @private
+ * @function
+ */
+export const isParentOf = (parent, child) => {
+  while (child !== null) {
+    if (child.parent === parent) {
+      return true
+    }
+    child = /** @type {AbstractType<any>} */ (child.parent)._item
+  }
+  return false
+}
--- a/src/y.js
+++ b/src/y.js
@@ -1,53 +0,0 @@
-/* @flow */
-'use strict'
-
-function Y (opts) {
-  return new Promise(function (resolve) {
-    var yconfig = new YConfig(opts, function () {
-      yconfig.db.whenUserIdSet(function () {
-        resolve(yconfig)
-      })
-    })
-  })
-}
-
-class YConfig {
-  constructor (opts, callback) {
-    this.db = new Y[opts.db.name](this, opts.db)
-    this.connector = new Y[opts.connector.name](this, opts.connector)
-    this.db.requestTransaction(function * requestTransaction () {
-      // create initial Map type
-      var model = {
-        id: ['_', 0],
-        struct: 'Map',
-        type: 'Map',
-        map: {}
-      }
-      yield* this.store.tryExecute.call(this, model)
-      var root = yield* this.getType(model.id)
-      this.store.y.root = root
-      callback()
-    })
-  }
-  isConnected () {
-    return this.connector.isSynced
-  }
-  disconnect () {
-    return this.connector.disconnect()
-  }
-  reconnect () {
-    return this.connector.reconnect()
-  }
-  destroy () {
-    this.disconnect()
-    this.db.destroy()
-    this.connector = null
-    this.db = null
-  }
-}
-
-if (typeof YConcurrency_TestingMode !== 'undefined') {
-  g.Y = Y //eslint-disable-line
-  // debugger //eslint-disable-line
-}
-Y.utils = {}
--- a/test.html
+++ b/test.html
@@ -0,0 +1,9 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <title>Testing Yjs</title>
+</head>
+<body>
+  <script type="module" src="./dist/tests.js"></script>
+</body>
+</html>
--- a/tests/consistency.tests.js
+++ b/tests/consistency.tests.js
@@ -0,0 +1,19 @@
+
+import * as Y from '../src/index.js'
+import * as t from 'lib0/testing.js'
+
+/**
+ * Client id should be changed when an instance receives updates from another client using the same client id.
+ *
+ * @param {t.TestCase} tc
+ */
+export const testClientIdDuplicateChange = tc => {
+  const doc1 = new Y.Doc()
+  doc1.clientID = 0
+  const doc2 = new Y.Doc()
+  doc2.clientID = 0
+  t.assert(doc2.clientID === doc1.clientID)
+  doc1.getArray('a').insert(0, [1, 2])
+  Y.applyUpdate(doc2, Y.encodeStateAsUpdate(doc1))
+  t.assert(doc2.clientID !== doc1.clientID)
+}
--- a/tests/encoding.tests.js
+++ b/tests/encoding.tests.js
@@ -0,0 +1,28 @@
+import * as t from 'lib0/testing.js'
+
+import {
+  contentRefs,
+  readContentBinary,
+  readContentDeleted,
+  readContentString,
+  readContentJSON,
+  readContentEmbed,
+  readContentType,
+  readContentFormat,
+  readContentAny
+} from '../src/internals.js'
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testStructReferences = tc => {
+  t.assert(contentRefs.length === 9)
+  t.assert(contentRefs[1] === readContentDeleted)
+  t.assert(contentRefs[2] === readContentJSON) // TODO: deprecate content json?
+  t.assert(contentRefs[3] === readContentBinary)
+  t.assert(contentRefs[4] === readContentString)
+  t.assert(contentRefs[5] === readContentEmbed)
+  t.assert(contentRefs[6] === readContentFormat)
+  t.assert(contentRefs[7] === readContentType)
+  t.assert(contentRefs[8] === readContentAny)
+}
--- a/tests/index.js
+++ b/tests/index.js
@@ -0,0 +1,24 @@
+
+import * as array from './y-array.tests.js'
+import * as map from './y-map.tests.js'
+import * as text from './y-text.tests.js'
+import * as xml from './y-xml.tests.js'
+import * as encoding from './encoding.tests.js'
+import * as undoredo from './undo-redo.tests.js'
+import * as consistency from './consistency.tests.js'
+
+import { runTests } from 'lib0/testing.js'
+import { isBrowser, isNode } from 'lib0/environment.js'
+import * as log from 'lib0/logging.js'
+
+if (isBrowser) {
+  log.createVConsole(document.body)
+}
+runTests({
+  map, array, text, xml, consistency, encoding, undoredo
+}).then(success => {
+  /* istanbul ignore next */
+  if (isNode) {
+    process.exit(success ? 0 : 1)
+  }
+})
--- a/tests/testHelper.js
+++ b/tests/testHelper.js
@@ -0,0 +1,417 @@
+import * as Y from '../src/index.js'
+
+import {
+  createDeleteSetFromStructStore,
+  getStateVector,
+  Item,
+  DeleteItem, DeleteSet, StructStore, Doc // eslint-disable-line
+} from '../src/internals.js'
+
+import * as t from 'lib0/testing.js'
+import * as prng from 'lib0/prng.js'
+import * as encoding from 'lib0/encoding.js'
+import * as decoding from 'lib0/decoding.js'
+import * as syncProtocol from 'y-protocols/sync.js'
+import * as object from 'lib0/object.js'
+export * from '../src/internals.js'
+
+/**
+ * @param {TestYInstance} y // publish message created by `y` to all other online clients
+ * @param {Uint8Array} m
+ */
+const broadcastMessage = (y, m) => {
+  if (y.tc.onlineConns.has(y)) {
+    y.tc.onlineConns.forEach(remoteYInstance => {
+      if (remoteYInstance !== y) {
+        remoteYInstance._receive(m, y)
+      }
+    })
+  }
+}
+
+export class TestYInstance extends Doc {
+  /**
+   * @param {TestConnector} testConnector
+   * @param {number} clientID
+   */
+  constructor (testConnector, clientID) {
+    super()
+    this.userID = clientID // overwriting clientID
+    /**
+     * @type {TestConnector}
+     */
+    this.tc = testConnector
+    /**
+     * @type {Map<TestYInstance, Array<Uint8Array>>}
+     */
+    this.receiving = new Map()
+    testConnector.allConns.add(this)
+    // set up observe on local model
+    this.on('update', /** @param {Uint8Array} update @param {any} origin */ (update, origin) => {
+      if (origin !== testConnector) {
+        const encoder = encoding.createEncoder()
+        syncProtocol.writeUpdate(encoder, update)
+        broadcastMessage(this, encoding.toUint8Array(encoder))
+      }
+    })
+    this.connect()
+  }
+
+  /**
+   * Disconnect from TestConnector.
+   */
+  disconnect () {
+    this.receiving = new Map()
+    this.tc.onlineConns.delete(this)
+  }
+
+  /**
+   * Append yourself to the list of known Y instances in testconnector.
+   * Also initiate sync with all clients.
+   */
+  connect () {
+    if (!this.tc.onlineConns.has(this)) {
+      this.tc.onlineConns.add(this)
+      const encoder = encoding.createEncoder()
+      syncProtocol.writeSyncStep1(encoder, this)
+      // publish SyncStep1
+      broadcastMessage(this, encoding.toUint8Array(encoder))
+      this.tc.onlineConns.forEach(remoteYInstance => {
+        if (remoteYInstance !== this) {
+          // remote instance sends instance to this instance
+          const encoder = encoding.createEncoder()
+          syncProtocol.writeSyncStep1(encoder, remoteYInstance)
+          this._receive(encoding.toUint8Array(encoder), remoteYInstance)
+        }
+      })
+    }
+  }
+
+  /**
+   * Receive a message from another client. This message is only appended to the list of receiving messages.
+   * TestConnector decides when this client actually reads this message.
+   *
+   * @param {Uint8Array} message
+   * @param {TestYInstance} remoteClient
+   */
+  _receive (message, remoteClient) {
+    let messages = this.receiving.get(remoteClient)
+    if (messages === undefined) {
+      messages = []
+      this.receiving.set(remoteClient, messages)
+    }
+    messages.push(message)
+  }
+}
+
+/**
+ * Keeps track of TestYInstances.
+ *
+ * The TestYInstances add/remove themselves from the list of connections maiained in this object.
+ * I think it makes sense. Deal with it.
+ */
+export class TestConnector {
+  /**
+   * @param {prng.PRNG} gen
+   */
+  constructor (gen) {
+    /**
+     * @type {Set<TestYInstance>}
+     */
+    this.allConns = new Set()
+    /**
+     * @type {Set<TestYInstance>}
+     */
+    this.onlineConns = new Set()
+    /**
+     * @type {prng.PRNG}
+     */
+    this.prng = gen
+  }
+
+  /**
+   * Create a new Y instance and add it to the list of connections
+   * @param {number} clientID
+   */
+  createY (clientID) {
+    return new TestYInstance(this, clientID)
+  }
+
+  /**
+   * Choose random connection and flush a random message from a random sender.
+   *
+   * If this function was unable to flush a message, because there are no more messages to flush, it returns false. true otherwise.
+   * @return {boolean}
+   */
+  flushRandomMessage () {
+    const gen = this.prng
+    const conns = Array.from(this.onlineConns).filter(conn => conn.receiving.size > 0)
+    if (conns.length > 0) {
+      const receiver = prng.oneOf(gen, conns)
+      const [sender, messages] = prng.oneOf(gen, Array.from(receiver.receiving))
+      const m = messages.shift()
+      if (messages.length === 0) {
+        receiver.receiving.delete(sender)
+      }
+      if (m === undefined) {
+        return this.flushRandomMessage()
+      }
+      const encoder = encoding.createEncoder()
+      // console.log('receive (' + sender.userID + '->' + receiver.userID + '):\n', syncProtocol.stringifySyncMessage(decoding.createDecoder(m), receiver))
+      // do not publish data created when this function is executed (could be ss2 or update message)
+      syncProtocol.readSyncMessage(decoding.createDecoder(m), encoder, receiver, receiver.tc)
+      if (encoding.length(encoder) > 0) {
+        // send reply message
+        sender._receive(encoding.toUint8Array(encoder), receiver)
+      }
+      return true
+    }
+    return false
+  }
+
+  /**
+   * @return {boolean} True iff this function actually flushed something
+   */
+  flushAllMessages () {
+    let didSomething = false
+    while (this.flushRandomMessage()) {
+      didSomething = true
+    }
+    return didSomething
+  }
+
+  reconnectAll () {
+    this.allConns.forEach(conn => conn.connect())
+  }
+
+  disconnectAll () {
+    this.allConns.forEach(conn => conn.disconnect())
+  }
+
+  syncAll () {
+    this.reconnectAll()
+    this.flushAllMessages()
+  }
+
+  /**
+   * @return {boolean} Whether it was possible to disconnect a randon connection.
+   */
+  disconnectRandom () {
+    if (this.onlineConns.size === 0) {
+      return false
+    }
+    prng.oneOf(this.prng, Array.from(this.onlineConns)).disconnect()
+    return true
+  }
+
+  /**
+   * @return {boolean} Whether it was possible to reconnect a random connection.
+   */
+  reconnectRandom () {
+    /**
+     * @type {Array<TestYInstance>}
+     */
+    const reconnectable = []
+    this.allConns.forEach(conn => {
+      if (!this.onlineConns.has(conn)) {
+        reconnectable.push(conn)
+      }
+    })
+    if (reconnectable.length === 0) {
+      return false
+    }
+    prng.oneOf(this.prng, reconnectable).connect()
+    return true
+  }
+}
+
+/**
+ * @template T
+ * @param {t.TestCase} tc
+ * @param {{users?:number}} conf
+ * @param {InitTestObjectCallback<T>} [initTestObject]
+ * @return {{testObjects:Array<any>,testConnector:TestConnector,users:Array<TestYInstance>,array0:Y.Array<any>,array1:Y.Array<any>,array2:Y.Array<any>,map0:Y.Map<any>,map1:Y.Map<any>,map2:Y.Map<any>,map3:Y.Map<any>,text0:Y.Text,text1:Y.Text,text2:Y.Text,xml0:Y.XmlElement,xml1:Y.XmlElement,xml2:Y.XmlElement}}
+ */
+export const init = (tc, { users = 5 } = {}, initTestObject) => {
+  /**
+   * @type {Object<string,any>}
+   */
+  const result = {
+    users: []
+  }
+  const gen = tc.prng
+  const testConnector = new TestConnector(gen)
+  result.testConnector = testConnector
+  for (let i = 0; i < users; i++) {
+    const y = testConnector.createY(i)
+    y.clientID = i
+    result.users.push(y)
+    result['array' + i] = y.get('array', Y.Array)
+    result['map' + i] = y.get('map', Y.Map)
+    result['xml' + i] = y.get('xml', Y.XmlElement)
+    result['text' + i] = y.get('text', Y.Text)
+  }
+  testConnector.syncAll()
+  result.testObjects = result.users.map(initTestObject || (() => null))
+  return /** @type {any} */ (result)
+}
+
+/**
+ * 1. reconnect and flush all
+ * 2. user 0 gc
+ * 3. get type content
+ * 4. disconnect & reconnect all (so gc is propagated)
+ * 5. compare os, ds, ss
+ *
+ * @param {Array<TestYInstance>} users
+ */
+export const compare = users => {
+  users.forEach(u => u.connect())
+  while (users[0].tc.flushAllMessages()) {}
+  const userArrayValues = users.map(u => u.getArray('array').toJSON())
+  const userMapValues = users.map(u => u.getMap('map').toJSON())
+  const userXmlValues = users.map(u => u.get('xml', Y.XmlElement).toString())
+  const userTextValues = users.map(u => u.getText('text').toDelta())
+  for (const u of users) {
+    t.assert(u.store.pendingDeleteReaders.length === 0)
+    t.assert(u.store.pendingStack.length === 0)
+    t.assert(u.store.pendingClientsStructRefs.size === 0)
+  }
+  // Test Array iterator
+  t.compare(users[0].getArray('array').toArray(), Array.from(users[0].getArray('array')))
+  // Test Map iterator
+  const ymapkeys = Array.from(users[0].getMap('map').keys())
+  t.assert(ymapkeys.length === Object.keys(userMapValues[0]).length)
+  ymapkeys.forEach(key => t.assert(object.hasProperty(userMapValues[0], key)))
+  /**
+   * @type {Object<string,any>}
+   */
+  const mapRes = {}
+  for (const [k, v] of users[0].getMap('map')) {
+    mapRes[k] = v instanceof Y.AbstractType ? v.toJSON() : v
+  }
+  t.compare(userMapValues[0], mapRes)
+  // Compare all users
+  for (let i = 0; i < users.length - 1; i++) {
+    t.compare(userArrayValues[i].length, users[i].getArray('array').length)
+    t.compare(userArrayValues[i], userArrayValues[i + 1])
+    t.compare(userMapValues[i], userMapValues[i + 1])
+    t.compare(userXmlValues[i], userXmlValues[i + 1])
+    t.compare(userTextValues[i].map(/** @param {any} a */ a => typeof a.insert === 'string' ? a.insert : ' ').join('').length, users[i].getText('text').length)
+    t.compare(userTextValues[i], userTextValues[i + 1])
+    t.compare(getStateVector(users[i].store), getStateVector(users[i + 1].store))
+    compareDS(createDeleteSetFromStructStore(users[i].store), createDeleteSetFromStructStore(users[i + 1].store))
+    compareStructStores(users[i].store, users[i + 1].store)
+  }
+  users.map(u => u.destroy())
+}
+
+/**
+ * @param {Item?} a
+ * @param {Item?} b
+ * @return {boolean}
+ */
+export const compareItemIDs = (a, b) => a === b || (a !== null && b != null && Y.compareIDs(a.id, b.id))
+
+/**
+ * @param {StructStore} ss1
+ * @param {StructStore} ss2
+ */
+export const compareStructStores = (ss1, ss2) => {
+  t.assert(ss1.clients.size === ss2.clients.size)
+  for (const [client, structs1] of ss1.clients) {
+    const structs2 = /** @type {Array<Y.AbstractStruct>} */ (ss2.clients.get(client))
+    t.assert(structs2 !== undefined && structs1.length === structs2.length)
+    for (let i = 0; i < structs1.length; i++) {
+      const s1 = structs1[i]
+      const s2 = structs2[i]
+      // checks for abstract struct
+      if (
+        s1.constructor !== s2.constructor ||
+        !Y.compareIDs(s1.id, s2.id) ||
+        s1.deleted !== s2.deleted ||
+        // @ts-ignore
+        s1.length !== s2.length
+      ) {
+        t.fail('Structs dont match')
+      }
+      if (s1 instanceof Item) {
+        if (
+          !(s2 instanceof Item) ||
+          !((s1.left === null && s2.left === null) || (s1.left !== null && s2.left !== null && Y.compareIDs(s1.left.lastId, s2.left.lastId))) ||
+          !compareItemIDs(s1.right, s2.right) ||
+          !Y.compareIDs(s1.origin, s2.origin) ||
+          !Y.compareIDs(s1.rightOrigin, s2.rightOrigin) ||
+          s1.parentSub !== s2.parentSub
+        ) {
+          return t.fail('Items dont match')
+        }
+        // make sure that items are connected correctly
+        t.assert(s1.left === null || s1.left.right === s1)
+        t.assert(s1.right === null || s1.right.left === s1)
+        t.assert(s2.left === null || s2.left.right === s2)
+        t.assert(s2.right === null || s2.right.left === s2)
+      }
+    }
+  }
+}
+
+/**
+ * @param {DeleteSet} ds1
+ * @param {DeleteSet} ds2
+ */
+export const compareDS = (ds1, ds2) => {
+  t.assert(ds1.clients.size === ds2.clients.size)
+  for (const [client, deleteItems1] of ds1.clients) {
+    const deleteItems2 = /** @type {Array<DeleteItem>} */ (ds2.clients.get(client))
+    t.assert(deleteItems2 !== undefined && deleteItems1.length === deleteItems2.length)
+    for (let i = 0; i < deleteItems1.length; i++) {
+      const di1 = deleteItems1[i]
+      const di2 = deleteItems2[i]
+      if (di1.clock !== di2.clock || di1.len !== di2.len) {
+        t.fail('DeleteSets dont match')
+      }
+    }
+  }
+}
+
+/**
+ * @template T
+ * @callback InitTestObjectCallback
+ * @param {TestYInstance} y
+ * @return {T}
+ */
+
+/**
+ * @template T
+ * @param {t.TestCase} tc
+ * @param {Array<function(Y.Doc,prng.PRNG,T):void>} mods
+ * @param {number} iterations
+ * @param {InitTestObjectCallback<T>} [initTestObject]
+ */
+export const applyRandomTests = (tc, mods, iterations, initTestObject) => {
+  const gen = tc.prng
+  const result = init(tc, { users: 5 }, initTestObject)
+  const { testConnector, users } = result
+  for (let i = 0; i < iterations; i++) {
+    if (prng.int31(gen, 0, 100) <= 2) {
+      // 2% chance to disconnect/reconnect a random user
+      if (prng.bool(gen)) {
+        testConnector.disconnectRandom()
+      } else {
+        testConnector.reconnectRandom()
+      }
+    } else if (prng.int31(gen, 0, 100) <= 1) {
+      // 1% chance to flush all
+      testConnector.flushAllMessages()
+    } else if (prng.int31(gen, 0, 100) <= 50) {
+      // 50% chance to flush a random message
+      testConnector.flushRandomMessage()
+    }
+    const user = prng.int31(gen, 0, users.length - 1)
+    const test = prng.oneOf(gen, mods)
+    test(users[user], gen, result.testObjects[user])
+  }
+  compare(users)
+  return result
+}
--- a/tests/undo-redo.tests.js
+++ b/tests/undo-redo.tests.js
@@ -0,0 +1,248 @@
+import { init, compare, applyRandomTests, Doc } from './testHelper.js' // eslint-disable-line
+
+import {
+  UndoManager
+} from '../src/internals.js'
+
+import * as Y from '../src/index.js'
+import * as t from 'lib0/testing.js'
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testUndoText = tc => {
+  const { testConnector, text0, text1 } = init(tc, { users: 3 })
+  const undoManager = new UndoManager(text0)
+
+  // items that are added & deleted in the same transaction won't be undo
+  text0.insert(0, 'test')
+  text0.delete(0, 4)
+  undoManager.undo()
+  t.assert(text0.toString() === '')
+
+  // follow redone items
+  text0.insert(0, 'a')
+  undoManager.stopCapturing()
+  text0.delete(0, 1)
+  undoManager.stopCapturing()
+  undoManager.undo()
+  t.assert(text0.toString() === 'a')
+  undoManager.undo()
+  t.assert(text0.toString() === '')
+
+  text0.insert(0, 'abc')
+  text1.insert(0, 'xyz')
+  testConnector.syncAll()
+  undoManager.undo()
+  t.assert(text0.toString() === 'xyz')
+  undoManager.redo()
+  t.assert(text0.toString() === 'abcxyz')
+  testConnector.syncAll()
+  text1.delete(0, 1)
+  testConnector.syncAll()
+  undoManager.undo()
+  t.assert(text0.toString() === 'xyz')
+  undoManager.redo()
+  t.assert(text0.toString() === 'bcxyz')
+  // test marks
+  text0.format(1, 3, { bold: true })
+  t.compare(text0.toDelta(), [{ insert: 'b' }, { insert: 'cxy', attributes: { bold: true } }, { insert: 'z' }])
+  undoManager.undo()
+  t.compare(text0.toDelta(), [{ insert: 'bcxyz' }])
+  undoManager.redo()
+  t.compare(text0.toDelta(), [{ insert: 'b' }, { insert: 'cxy', attributes: { bold: true } }, { insert: 'z' }])
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testUndoMap = tc => {
+  const { testConnector, map0, map1 } = init(tc, { users: 2 })
+  map0.set('a', 0)
+  const undoManager = new UndoManager(map0)
+  map0.set('a', 1)
+  undoManager.undo()
+  t.assert(map0.get('a') === 0)
+  undoManager.redo()
+  t.assert(map0.get('a') === 1)
+  // testing sub-types and if it can restore a whole type
+  const subType = new Y.Map()
+  map0.set('a', subType)
+  subType.set('x', 42)
+  t.compare(map0.toJSON(), /** @type {any} */ ({ a: { x: 42 } }))
+  undoManager.undo()
+  t.assert(map0.get('a') === 1)
+  undoManager.redo()
+  t.compare(map0.toJSON(), /** @type {any} */ ({ a: { x: 42 } }))
+  testConnector.syncAll()
+  // if content is overwritten by another user, undo operations should be skipped
+  map1.set('a', 44)
+  testConnector.syncAll()
+  undoManager.undo()
+  t.assert(map0.get('a') === 44)
+  undoManager.redo()
+  t.assert(map0.get('a') === 44)
+
+  // test setting value multiple times
+  map0.set('b', 'initial')
+  undoManager.stopCapturing()
+  map0.set('b', 'val1')
+  map0.set('b', 'val2')
+  undoManager.stopCapturing()
+  undoManager.undo()
+  t.assert(map0.get('b') === 'initial')
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testUndoArray = tc => {
+  const { testConnector, array0, array1 } = init(tc, { users: 3 })
+  const undoManager = new UndoManager(array0)
+  array0.insert(0, [1, 2, 3])
+  array1.insert(0, [4, 5, 6])
+  testConnector.syncAll()
+  t.compare(array0.toArray(), [1, 2, 3, 4, 5, 6])
+  undoManager.undo()
+  t.compare(array0.toArray(), [4, 5, 6])
+  undoManager.redo()
+  t.compare(array0.toArray(), [1, 2, 3, 4, 5, 6])
+  testConnector.syncAll()
+  array1.delete(0, 1) // user1 deletes [1]
+  testConnector.syncAll()
+  undoManager.undo()
+  t.compare(array0.toArray(), [4, 5, 6])
+  undoManager.redo()
+  t.compare(array0.toArray(), [2, 3, 4, 5, 6])
+  array0.delete(0, 5)
+  // test nested structure
+  const ymap = new Y.Map()
+  array0.insert(0, [ymap])
+  t.compare(array0.toJSON(), [{}])
+  undoManager.stopCapturing()
+  ymap.set('a', 1)
+  t.compare(array0.toJSON(), [{ a: 1 }])
+  undoManager.undo()
+  t.compare(array0.toJSON(), [{}])
+  undoManager.undo()
+  t.compare(array0.toJSON(), [2, 3, 4, 5, 6])
+  undoManager.redo()
+  t.compare(array0.toJSON(), [{}])
+  undoManager.redo()
+  t.compare(array0.toJSON(), [{ a: 1 }])
+  testConnector.syncAll()
+  array1.get(0).set('b', 2)
+  testConnector.syncAll()
+  t.compare(array0.toJSON(), [{ a: 1, b: 2 }])
+  undoManager.undo()
+  t.compare(array0.toJSON(), [{ b: 2 }])
+  undoManager.undo()
+  t.compare(array0.toJSON(), [2, 3, 4, 5, 6])
+  undoManager.redo()
+  t.compare(array0.toJSON(), [{ b: 2 }])
+  undoManager.redo()
+  t.compare(array0.toJSON(), [{ a: 1, b: 2 }])
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testUndoXml = tc => {
+  const { xml0 } = init(tc, { users: 3 })
+  const undoManager = new UndoManager(xml0)
+  const child = new Y.XmlElement('p')
+  xml0.insert(0, [child])
+  const textchild = new Y.XmlText('content')
+  child.insert(0, [textchild])
+  t.assert(xml0.toString() === '<undefined><p>content</p></undefined>')
+  // format textchild and revert that change
+  undoManager.stopCapturing()
+  textchild.format(3, 4, { bold: {} })
+  t.assert(xml0.toString() === '<undefined><p>con<bold>tent</bold></p></undefined>')
+  undoManager.undo()
+  t.assert(xml0.toString() === '<undefined><p>content</p></undefined>')
+  undoManager.redo()
+  t.assert(xml0.toString() === '<undefined><p>con<bold>tent</bold></p></undefined>')
+  xml0.delete(0, 1)
+  t.assert(xml0.toString() === '<undefined></undefined>')
+  undoManager.undo()
+  t.assert(xml0.toString() === '<undefined><p>con<bold>tent</bold></p></undefined>')
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testUndoEvents = tc => {
+  const { text0 } = init(tc, { users: 3 })
+  const undoManager = new UndoManager(text0)
+  let counter = 0
+  let receivedMetadata = -1
+  undoManager.on('stack-item-added', /** @param {any} event */ event => {
+    t.assert(event.type != null)
+    event.stackItem.meta.set('test', counter++)
+  })
+  undoManager.on('stack-item-popped', /** @param {any} event */ event => {
+    t.assert(event.type != null)
+    receivedMetadata = event.stackItem.meta.get('test')
+  })
+  text0.insert(0, 'abc')
+  undoManager.undo()
+  t.assert(receivedMetadata === 0)
+  undoManager.redo()
+  t.assert(receivedMetadata === 1)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testTrackClass = tc => {
+  const { users, text0 } = init(tc, { users: 3 })
+  // only track origins that are numbers
+  const undoManager = new UndoManager(text0, { trackedOrigins: new Set([Number]) })
+  users[0].transact(() => {
+    text0.insert(0, 'abc')
+  }, 42)
+  t.assert(text0.toString() === 'abc')
+  undoManager.undo()
+  t.assert(text0.toString() === '')
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testTypeScope = tc => {
+  const { array0 } = init(tc, { users: 3 })
+  // only track origins that are numbers
+  const text0 = new Y.Text()
+  const text1 = new Y.Text()
+  array0.insert(0, [text0, text1])
+  const undoManager = new UndoManager(text0)
+  const undoManagerBoth = new UndoManager([text0, text1])
+  text1.insert(0, 'abc')
+  t.assert(undoManager.undoStack.length === 0)
+  t.assert(undoManagerBoth.undoStack.length === 1)
+  t.assert(text1.toString() === 'abc')
+  undoManager.undo()
+  t.assert(text1.toString() === 'abc')
+  undoManagerBoth.undo()
+  t.assert(text1.toString() === '')
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testUndoDeleteFilter = tc => {
+  /**
+   * @type {Array<Y.Map<any>>}
+   */
+  const array0 = /** @type {any} */ (init(tc, { users: 3 }).array0)
+  const undoManager = new UndoManager(array0, { deleteFilter: item => !(item instanceof Y.Item) || (item.content instanceof Y.ContentType && item.content.type._map.size === 0) })
+  const map0 = new Y.Map()
+  map0.set('hi', 1)
+  const map1 = new Y.Map()
+  array0.insert(0, [map0, map1])
+  undoManager.undo()
+  t.assert(array0.length === 1)
+  array0.get(0)
+  t.assert(Array.from(array0.get(0).keys()).length === 1)
+}
--- a/tests/y-array.tests.js
+++ b/tests/y-array.tests.js
@@ -0,0 +1,494 @@
+import { init, compare, applyRandomTests, Doc } from './testHelper.js' // eslint-disable-line
+
+import * as Y from '../src/index.js'
+import * as t from 'lib0/testing.js'
+import * as prng from 'lib0/prng.js'
+import * as math from 'lib0/math.js'
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testDeleteInsert = tc => {
+  const { users, array0 } = init(tc, { users: 2 })
+  array0.delete(0, 0)
+  t.describe('Does not throw when deleting zero elements with position 0')
+  t.fails(() => {
+    array0.delete(1, 1)
+  })
+  array0.insert(0, ['A'])
+  array0.delete(1, 0)
+  t.describe('Does not throw when deleting zero elements with valid position 1')
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testInsertThreeElementsTryRegetProperty = tc => {
+  const { testConnector, users, array0, array1 } = init(tc, { users: 2 })
+  array0.insert(0, [1, true, false])
+  t.compare(array0.toJSON(), [1, true, false], '.toJSON() works')
+  testConnector.flushAllMessages()
+  t.compare(array1.toJSON(), [1, true, false], '.toJSON() works after sync')
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testConcurrentInsertWithThreeConflicts = tc => {
+  var { users, array0, array1, array2 } = init(tc, { users: 3 })
+  array0.insert(0, [0])
+  array1.insert(0, [1])
+  array2.insert(0, [2])
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testConcurrentInsertDeleteWithThreeConflicts = tc => {
+  const { testConnector, users, array0, array1, array2 } = init(tc, { users: 3 })
+  array0.insert(0, ['x', 'y', 'z'])
+  testConnector.flushAllMessages()
+  array0.insert(1, [0])
+  array1.delete(0)
+  array1.delete(1, 1)
+  array2.insert(1, [2])
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testInsertionsInLateSync = tc => {
+  const { testConnector, users, array0, array1, array2 } = init(tc, { users: 3 })
+  array0.insert(0, ['x', 'y'])
+  testConnector.flushAllMessages()
+  users[1].disconnect()
+  users[2].disconnect()
+  array0.insert(1, ['user0'])
+  array1.insert(1, ['user1'])
+  array2.insert(1, ['user2'])
+  users[1].connect()
+  users[2].connect()
+  testConnector.flushAllMessages()
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testDisconnectReallyPreventsSendingMessages = tc => {
+  var { testConnector, users, array0, array1 } = init(tc, { users: 3 })
+  array0.insert(0, ['x', 'y'])
+  testConnector.flushAllMessages()
+  users[1].disconnect()
+  users[2].disconnect()
+  array0.insert(1, ['user0'])
+  array1.insert(1, ['user1'])
+  t.compare(array0.toJSON(), ['x', 'user0', 'y'])
+  t.compare(array1.toJSON(), ['x', 'user1', 'y'])
+  users[1].connect()
+  users[2].connect()
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testDeletionsInLateSync = tc => {
+  const { testConnector, users, array0, array1 } = init(tc, { users: 2 })
+  array0.insert(0, ['x', 'y'])
+  testConnector.flushAllMessages()
+  users[1].disconnect()
+  array1.delete(1, 1)
+  array0.delete(0, 2)
+  users[1].connect()
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testInsertThenMergeDeleteOnSync = tc => {
+  const { testConnector, users, array0, array1 } = init(tc, { users: 2 })
+  array0.insert(0, ['x', 'y', 'z'])
+  testConnector.flushAllMessages()
+  users[0].disconnect()
+  array1.delete(0, 3)
+  users[0].connect()
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testInsertAndDeleteEvents = tc => {
+  const { array0, users } = init(tc, { users: 2 })
+  /**
+   * @type {Object<string,any>?}
+   */
+  let event = null
+  array0.observe(e => {
+    event = e
+  })
+  array0.insert(0, [0, 1, 2])
+  t.assert(event !== null)
+  event = null
+  array0.delete(0)
+  t.assert(event !== null)
+  event = null
+  array0.delete(0, 2)
+  t.assert(event !== null)
+  event = null
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testNestedObserverEvents = tc => {
+  const { array0, users } = init(tc, { users: 2 })
+  /**
+   * @type {Array<number>}
+   */
+  const vals = []
+  array0.observe(e => {
+    if (array0.length === 1) {
+      // inserting, will call this observer again
+      // we expect that this observer is called after this event handler finishedn
+      array0.insert(1, [1])
+      vals.push(0)
+    } else {
+      // this should be called the second time an element is inserted (above case)
+      vals.push(1)
+    }
+  })
+  array0.insert(0, [0])
+  t.compareArrays(vals, [0, 1])
+  t.compareArrays(array0.toArray(), [0, 1])
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testInsertAndDeleteEventsForTypes = tc => {
+  const { array0, users } = init(tc, { users: 2 })
+  /**
+   * @type {Object<string,any>|null}
+   */
+  let event = null
+  array0.observe(e => {
+    event = e
+  })
+  array0.insert(0, [new Y.Array()])
+  t.assert(event !== null)
+  event = null
+  array0.delete(0)
+  t.assert(event !== null)
+  event = null
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testChangeEvent = tc => {
+  const { array0, users } = init(tc, { users: 2 })
+  /**
+   * @type {any}
+   */
+  let changes = null
+  array0.observe(e => {
+    changes = e.changes
+  })
+  const newArr = new Y.Array()
+  array0.insert(0, [newArr, 4, 'dtrn'])
+  t.assert(changes !== null && changes.added.size === 2 && changes.deleted.size === 0)
+  t.compare(changes.delta, [{ insert: [newArr, 4, 'dtrn'] }])
+  changes = null
+  array0.delete(0, 2)
+  t.assert(changes !== null && changes.added.size === 0 && changes.deleted.size === 2)
+  t.compare(changes.delta, [{ delete: 2 }])
+  changes = null
+  array0.insert(1, [0.1])
+  t.assert(changes !== null && changes.added.size === 1 && changes.deleted.size === 0)
+  t.compare(changes.delta, [{ retain: 1 }, { insert: [0.1] }])
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testInsertAndDeleteEventsForTypes2 = tc => {
+  const { array0, users } = init(tc, { users: 2 })
+  /**
+   * @type {Array<Object<string,any>>}
+   */
+  const events = []
+  array0.observe(e => {
+    events.push(e)
+  })
+  array0.insert(0, ['hi', new Y.Map()])
+  t.assert(events.length === 1, 'Event is triggered exactly once for insertion of two elements')
+  array0.delete(1)
+  t.assert(events.length === 2, 'Event is triggered exactly once for deletion')
+  compare(users)
+}
+
+/**
+ * This issue has been reported here https://github.com/yjs/yjs/issues/155
+ * @param {t.TestCase} tc
+ */
+export const testNewChildDoesNotEmitEventInTransaction = tc => {
+  const { array0, users } = init(tc, { users: 2 })
+  let fired = false
+  users[0].transact(() => {
+    const newMap = new Y.Map()
+    newMap.observe(() => {
+      fired = true
+    })
+    array0.insert(0, [newMap])
+    newMap.set('tst', 42)
+  })
+  t.assert(!fired, 'Event does not trigger')
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testGarbageCollector = tc => {
+  const { testConnector, users, array0 } = init(tc, { users: 3 })
+  array0.insert(0, ['x', 'y', 'z'])
+  testConnector.flushAllMessages()
+  users[0].disconnect()
+  array0.delete(0, 3)
+  users[0].connect()
+  testConnector.flushAllMessages()
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testEventTargetIsSetCorrectlyOnLocal = tc => {
+  const { array0, users } = init(tc, { users: 3 })
+  /**
+   * @type {any}
+   */
+  let event
+  array0.observe(e => {
+    event = e
+  })
+  array0.insert(0, ['stuff'])
+  t.assert(event.target === array0, '"target" property is set correctly')
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testEventTargetIsSetCorrectlyOnRemote = tc => {
+  const { testConnector, array0, array1, users } = init(tc, { users: 3 })
+  /**
+   * @type {any}
+   */
+  let event
+  array0.observe(e => {
+    event = e
+  })
+  array1.insert(0, ['stuff'])
+  testConnector.flushAllMessages()
+  t.assert(event.target === array0, '"target" property is set correctly')
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testIteratingArrayContainingTypes = tc => {
+  const y = new Y.Doc()
+  const arr = y.getArray('arr')
+  const numItems = 10
+  for (let i = 0; i < numItems; i++) {
+    const map = new Y.Map()
+    map.set('value', i)
+    arr.push([map])
+  }
+  let cnt = 0
+  for (const item of arr) {
+    t.assert(item.get('value') === cnt++, 'value is correct')
+  }
+  y.destroy()
+}
+
+let _uniqueNumber = 0
+const getUniqueNumber = () => _uniqueNumber++
+
+/**
+ * @type {Array<function(Doc,prng.PRNG,any):void>}
+ */
+const arrayTransactions = [
+  function insert (user, gen) {
+    const yarray = user.getArray('array')
+    var uniqueNumber = getUniqueNumber()
+    var content = []
+    var len = prng.int31(gen, 1, 4)
+    for (var i = 0; i < len; i++) {
+      content.push(uniqueNumber)
+    }
+    var pos = prng.int31(gen, 0, yarray.length)
+    yarray.insert(pos, content)
+  },
+  function insertTypeArray (user, gen) {
+    const yarray = user.getArray('array')
+    var pos = prng.int31(gen, 0, yarray.length)
+    yarray.insert(pos, [new Y.Array()])
+    var array2 = yarray.get(pos)
+    array2.insert(0, [1, 2, 3, 4])
+  },
+  function insertTypeMap (user, gen) {
+    const yarray = user.getArray('array')
+    var pos = prng.int31(gen, 0, yarray.length)
+    yarray.insert(pos, [new Y.Map()])
+    var map = yarray.get(pos)
+    map.set('someprop', 42)
+    map.set('someprop', 43)
+    map.set('someprop', 44)
+  },
+  function _delete (user, gen) {
+    const yarray = user.getArray('array')
+    var length = yarray.length
+    if (length > 0) {
+      var somePos = prng.int31(gen, 0, length - 1)
+      var delLength = prng.int31(gen, 1, math.min(2, length - somePos))
+      if (prng.bool(gen)) {
+        var type = yarray.get(somePos)
+        if (type.length > 0) {
+          somePos = prng.int31(gen, 0, type.length - 1)
+          delLength = prng.int31(gen, 0, math.min(2, type.length - somePos))
+          type.delete(somePos, delLength)
+        }
+      } else {
+        yarray.delete(somePos, delLength)
+      }
+    }
+  }
+]
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYarrayTests4 = tc => {
+  applyRandomTests(tc, arrayTransactions, 4)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYarrayTests40 = tc => {
+  applyRandomTests(tc, arrayTransactions, 40)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYarrayTests42 = tc => {
+  applyRandomTests(tc, arrayTransactions, 42)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYarrayTests43 = tc => {
+  applyRandomTests(tc, arrayTransactions, 43)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYarrayTests44 = tc => {
+  applyRandomTests(tc, arrayTransactions, 44)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYarrayTests45 = tc => {
+  applyRandomTests(tc, arrayTransactions, 45)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYarrayTests46 = tc => {
+  applyRandomTests(tc, arrayTransactions, 46)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYarrayTests300 = tc => {
+  applyRandomTests(tc, arrayTransactions, 300)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYarrayTests400 = tc => {
+  applyRandomTests(tc, arrayTransactions, 400)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYarrayTests500 = tc => {
+  applyRandomTests(tc, arrayTransactions, 500)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYarrayTests600 = tc => {
+  applyRandomTests(tc, arrayTransactions, 600)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYarrayTests1000 = tc => {
+  applyRandomTests(tc, arrayTransactions, 1000)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYarrayTests1800 = tc => {
+  applyRandomTests(tc, arrayTransactions, 1800)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYarrayTests3000 = tc => {
+  t.skip(!t.production)
+  applyRandomTests(tc, arrayTransactions, 3000)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYarrayTests5000 = tc => {
+  t.skip(!t.production)
+  applyRandomTests(tc, arrayTransactions, 5000)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYarrayTests30000 = tc => {
+  t.skip(!t.production)
+  applyRandomTests(tc, arrayTransactions, 30000)
+}
--- a/tests/y-map.tests.js
+++ b/tests/y-map.tests.js
@@ -0,0 +1,609 @@
+import { init, compare, applyRandomTests, Doc } from './testHelper.js' // eslint-disable-line
+
+import {
+  compareIDs
+} from '../src/internals.js'
+
+import * as Y from '../src/index.js'
+import * as t from 'lib0/testing.js'
+import * as prng from 'lib0/prng.js'
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testMapHavingIterableAsConstructorParamTests = tc => {
+  const { map0 } = init(tc, { users: 1 })
+
+  const m1 = new Y.Map(Object.entries({ number: 1, string: 'hello' }))
+  map0.set('m1', m1)
+  t.assert(m1.get('number') === 1)
+  t.assert(m1.get('string') === 'hello')
+
+  const m2 = new Y.Map([
+    ['object', { x: 1 }],
+    ['boolean', true]
+  ])
+  map0.set('m2', m2)
+  t.assert(m2.get('object').x === 1)
+  t.assert(m2.get('boolean') === true)
+
+  const m3 = new Y.Map([...m1, ...m2])
+  map0.set('m3', m3)
+  t.assert(m3.get('number') === 1)
+  t.assert(m3.get('string') === 'hello')
+  t.assert(m3.get('object').x === 1)
+  t.assert(m3.get('boolean') === true)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testBasicMapTests = tc => {
+  const { testConnector, users, map0, map1, map2 } = init(tc, { users: 3 })
+  users[2].disconnect()
+
+  map0.set('number', 1)
+  map0.set('string', 'hello Y')
+  map0.set('object', { key: { key2: 'value' } })
+  map0.set('y-map', new Y.Map())
+  map0.set('boolean1', true)
+  map0.set('boolean0', false)
+  const map = map0.get('y-map')
+  map.set('y-array', new Y.Array())
+  const array = map.get('y-array')
+  array.insert(0, [0])
+  array.insert(0, [-1])
+
+  t.assert(map0.get('number') === 1, 'client 0 computed the change (number)')
+  t.assert(map0.get('string') === 'hello Y', 'client 0 computed the change (string)')
+  t.assert(map0.get('boolean0') === false, 'client 0 computed the change (boolean)')
+  t.assert(map0.get('boolean1') === true, 'client 0 computed the change (boolean)')
+  t.compare(map0.get('object'), { key: { key2: 'value' } }, 'client 0 computed the change (object)')
+  t.assert(map0.get('y-map').get('y-array').get(0) === -1, 'client 0 computed the change (type)')
+  t.assert(map0.size === 6, 'client 0 map has correct size')
+
+  users[2].connect()
+  testConnector.flushAllMessages()
+
+  t.assert(map1.get('number') === 1, 'client 1 received the update (number)')
+  t.assert(map1.get('string') === 'hello Y', 'client 1 received the update (string)')
+  t.assert(map1.get('boolean0') === false, 'client 1 computed the change (boolean)')
+  t.assert(map1.get('boolean1') === true, 'client 1 computed the change (boolean)')
+  t.compare(map1.get('object'), { key: { key2: 'value' } }, 'client 1 received the update (object)')
+  t.assert(map1.get('y-map').get('y-array').get(0) === -1, 'client 1 received the update (type)')
+  t.assert(map1.size === 6, 'client 1 map has correct size')
+
+  // compare disconnected user
+  t.assert(map2.get('number') === 1, 'client 2 received the update (number) - was disconnected')
+  t.assert(map2.get('string') === 'hello Y', 'client 2 received the update (string) - was disconnected')
+  t.assert(map2.get('boolean0') === false, 'client 2 computed the change (boolean)')
+  t.assert(map2.get('boolean1') === true, 'client 2 computed the change (boolean)')
+  t.compare(map2.get('object'), { key: { key2: 'value' } }, 'client 2 received the update (object) - was disconnected')
+  t.assert(map2.get('y-map').get('y-array').get(0) === -1, 'client 2 received the update (type) - was disconnected')
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testGetAndSetOfMapProperty = tc => {
+  const { testConnector, users, map0 } = init(tc, { users: 2 })
+  map0.set('stuff', 'stuffy')
+  map0.set('undefined', undefined)
+  map0.set('null', null)
+  t.compare(map0.get('stuff'), 'stuffy')
+
+  testConnector.flushAllMessages()
+
+  for (const user of users) {
+    const u = user.getMap('map')
+    t.compare(u.get('stuff'), 'stuffy')
+    t.assert(u.get('undefined') === undefined, 'undefined')
+    t.compare(u.get('null'), null, 'null')
+  }
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testYmapSetsYmap = tc => {
+  const { users, map0 } = init(tc, { users: 2 })
+  const map = map0.set('Map', new Y.Map())
+  t.assert(map0.get('Map') === map)
+  map.set('one', 1)
+  t.compare(map.get('one'), 1)
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testYmapSetsYarray = tc => {
+  const { users, map0 } = init(tc, { users: 2 })
+  const array = map0.set('Array', new Y.Array())
+  t.assert(array === map0.get('Array'))
+  array.insert(0, [1, 2, 3])
+  // @ts-ignore
+  t.compare(map0.toJSON(), { Array: [1, 2, 3] })
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testGetAndSetOfMapPropertySyncs = tc => {
+  const { testConnector, users, map0 } = init(tc, { users: 2 })
+  map0.set('stuff', 'stuffy')
+  t.compare(map0.get('stuff'), 'stuffy')
+  testConnector.flushAllMessages()
+  for (const user of users) {
+    var u = user.getMap('map')
+    t.compare(u.get('stuff'), 'stuffy')
+  }
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testGetAndSetOfMapPropertyWithConflict = tc => {
+  const { testConnector, users, map0, map1 } = init(tc, { users: 3 })
+  map0.set('stuff', 'c0')
+  map1.set('stuff', 'c1')
+  testConnector.flushAllMessages()
+  for (const user of users) {
+    var u = user.getMap('map')
+    t.compare(u.get('stuff'), 'c1')
+  }
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testSizeAndDeleteOfMapProperty = tc => {
+  const { map0 } = init(tc, { users: 1 })
+  map0.set('stuff', 'c0')
+  map0.set('otherstuff', 'c1')
+  t.assert(map0.size === 2, `map size is ${map0.size} expected 2`)
+  map0.delete('stuff')
+  t.assert(map0.size === 1, `map size after delete is ${map0.size}, expected 1`)
+  map0.delete('otherstuff')
+  t.assert(map0.size === 0, `map size after delete is ${map0.size}, expected 0`)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testGetAndSetAndDeleteOfMapProperty = tc => {
+  const { testConnector, users, map0, map1 } = init(tc, { users: 3 })
+  map0.set('stuff', 'c0')
+  map1.set('stuff', 'c1')
+  map1.delete('stuff')
+  testConnector.flushAllMessages()
+  for (const user of users) {
+    var u = user.getMap('map')
+    t.assert(u.get('stuff') === undefined)
+  }
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testGetAndSetOfMapPropertyWithThreeConflicts = tc => {
+  const { testConnector, users, map0, map1, map2 } = init(tc, { users: 3 })
+  map0.set('stuff', 'c0')
+  map1.set('stuff', 'c1')
+  map1.set('stuff', 'c2')
+  map2.set('stuff', 'c3')
+  testConnector.flushAllMessages()
+  for (const user of users) {
+    var u = user.getMap('map')
+    t.compare(u.get('stuff'), 'c3')
+  }
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testGetAndSetAndDeleteOfMapPropertyWithThreeConflicts = tc => {
+  const { testConnector, users, map0, map1, map2, map3 } = init(tc, { users: 4 })
+  map0.set('stuff', 'c0')
+  map1.set('stuff', 'c1')
+  map1.set('stuff', 'c2')
+  map2.set('stuff', 'c3')
+  testConnector.flushAllMessages()
+  map0.set('stuff', 'deleteme')
+  map1.set('stuff', 'c1')
+  map2.set('stuff', 'c2')
+  map3.set('stuff', 'c3')
+  map3.delete('stuff')
+  testConnector.flushAllMessages()
+  for (const user of users) {
+    var u = user.getMap('map')
+    t.assert(u.get('stuff') === undefined)
+  }
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testObserveDeepProperties = tc => {
+  const { testConnector, users, map1, map2, map3 } = init(tc, { users: 4 })
+  const _map1 = map1.set('map', new Y.Map())
+  let calls = 0
+  let dmapid
+  map1.observeDeep(events => {
+    events.forEach(event => {
+      calls++
+      // @ts-ignore
+      t.assert(event.keysChanged.has('deepmap'))
+      t.assert(event.path.length === 1)
+      t.assert(event.path[0] === 'map')
+      // @ts-ignore
+      dmapid = event.target.get('deepmap')._item.id
+    })
+  })
+  testConnector.flushAllMessages()
+  const _map3 = map3.get('map')
+  _map3.set('deepmap', new Y.Map())
+  testConnector.flushAllMessages()
+  const _map2 = map2.get('map')
+  _map2.set('deepmap', new Y.Map())
+  testConnector.flushAllMessages()
+  const dmap1 = _map1.get('deepmap')
+  const dmap2 = _map2.get('deepmap')
+  const dmap3 = _map3.get('deepmap')
+  t.assert(calls > 0)
+  t.assert(compareIDs(dmap1._item.id, dmap2._item.id))
+  t.assert(compareIDs(dmap1._item.id, dmap3._item.id))
+  // @ts-ignore we want the possibility of dmapid being undefined
+  t.assert(compareIDs(dmap1._item.id, dmapid))
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testObserversUsingObservedeep = tc => {
+  const { users, map0 } = init(tc, { users: 2 })
+  /**
+   * @type {Array<Array<string|number>>}
+   */
+  const pathes = []
+  let calls = 0
+  map0.observeDeep(events => {
+    events.forEach(event => {
+      pathes.push(event.path)
+    })
+    calls++
+  })
+  map0.set('map', new Y.Map())
+  map0.get('map').set('array', new Y.Array())
+  map0.get('map').get('array').insert(0, ['content'])
+  t.assert(calls === 3)
+  t.compare(pathes, [[], ['map'], ['map', 'array']])
+  compare(users)
+}
+
+// TODO: Test events in Y.Map
+/**
+ * @param {Object<string,any>} is
+ * @param {Object<string,any>} should
+ */
+const compareEvent = (is, should) => {
+  for (var key in should) {
+    t.compare(should[key], is[key])
+  }
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testThrowsAddAndUpdateAndDeleteEvents = tc => {
+  const { users, map0 } = init(tc, { users: 2 })
+  /**
+   * @type {Object<string,any>}
+   */
+  let event = {}
+  map0.observe(e => {
+    event = e // just put it on event, should be thrown synchronously anyway
+  })
+  map0.set('stuff', 4)
+  compareEvent(event, {
+    target: map0,
+    keysChanged: new Set(['stuff'])
+  })
+  // update, oldValue is in contents
+  map0.set('stuff', new Y.Array())
+  compareEvent(event, {
+    target: map0,
+    keysChanged: new Set(['stuff'])
+  })
+  // update, oldValue is in opContents
+  map0.set('stuff', 5)
+  // delete
+  map0.delete('stuff')
+  compareEvent(event, {
+    keysChanged: new Set(['stuff']),
+    target: map0
+  })
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testChangeEvent = tc => {
+  const { map0, users } = init(tc, { users: 2 })
+  /**
+   * @type {any}
+   */
+  let changes = null
+  /**
+   * @type {any}
+   */
+  let keyChange = null
+  map0.observe(e => {
+    changes = e.changes
+  })
+  map0.set('a', 1)
+  keyChange = changes.keys.get('a')
+  t.assert(changes !== null && keyChange.action === 'add' && keyChange.oldValue === undefined)
+  map0.set('a', 2)
+  keyChange = changes.keys.get('a')
+  t.assert(changes !== null && keyChange.action === 'update' && keyChange.oldValue === 1)
+  users[0].transact(() => {
+    map0.set('a', 3)
+    map0.set('a', 4)
+  })
+  keyChange = changes.keys.get('a')
+  t.assert(changes !== null && keyChange.action === 'update' && keyChange.oldValue === 2)
+  users[0].transact(() => {
+    map0.set('b', 1)
+    map0.set('b', 2)
+  })
+  keyChange = changes.keys.get('b')
+  t.assert(changes !== null && keyChange.action === 'add' && keyChange.oldValue === undefined)
+  users[0].transact(() => {
+    map0.set('c', 1)
+    map0.delete('c')
+  })
+  t.assert(changes !== null && changes.keys.size === 0)
+  users[0].transact(() => {
+    map0.set('d', 1)
+    map0.set('d', 2)
+  })
+  keyChange = changes.keys.get('d')
+  t.assert(changes !== null && keyChange.action === 'add' && keyChange.oldValue === undefined)
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testYmapEventExceptionsShouldCompleteTransaction = tc => {
+  const doc = new Y.Doc()
+  const map = doc.getMap('map')
+
+  let updateCalled = false
+  let throwingObserverCalled = false
+  let throwingDeepObserverCalled = false
+  doc.on('update', () => {
+    updateCalled = true
+  })
+
+  const throwingObserver = () => {
+    throwingObserverCalled = true
+    throw new Error('Failure')
+  }
+
+  const throwingDeepObserver = () => {
+    throwingDeepObserverCalled = true
+    throw new Error('Failure')
+  }
+
+  map.observe(throwingObserver)
+  map.observeDeep(throwingDeepObserver)
+
+  t.fails(() => {
+    map.set('y', '2')
+  })
+
+  t.assert(updateCalled)
+  t.assert(throwingObserverCalled)
+  t.assert(throwingDeepObserverCalled)
+
+  // check if it works again
+  updateCalled = false
+  throwingObserverCalled = false
+  throwingDeepObserverCalled = false
+  t.fails(() => {
+    map.set('z', '3')
+  })
+
+  t.assert(updateCalled)
+  t.assert(throwingObserverCalled)
+  t.assert(throwingDeepObserverCalled)
+
+  t.assert(map.get('z') === '3')
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testYmapEventHasCorrectValueWhenSettingAPrimitive = tc => {
+  const { users, map0 } = init(tc, { users: 3 })
+  /**
+   * @type {Object<string,any>}
+   */
+  let event = {}
+  map0.observe(e => {
+    event = e
+  })
+  map0.set('stuff', 2)
+  t.compare(event.value, event.target.get(event.name))
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testYmapEventHasCorrectValueWhenSettingAPrimitiveFromOtherUser = tc => {
+  const { users, map0, map1, testConnector } = init(tc, { users: 3 })
+  /**
+   * @type {Object<string,any>}
+   */
+  let event = {}
+  map0.observe(e => {
+    event = e
+  })
+  map1.set('stuff', 2)
+  testConnector.flushAllMessages()
+  t.compare(event.value, event.target.get(event.name))
+  compare(users)
+}
+
+/**
+ * @type {Array<function(Doc,prng.PRNG):void>}
+ */
+const mapTransactions = [
+  function set (user, gen) {
+    const key = prng.oneOf(gen, ['one', 'two'])
+    var value = prng.utf16String(gen)
+    user.getMap('map').set(key, value)
+  },
+  function setType (user, gen) {
+    const key = prng.oneOf(gen, ['one', 'two'])
+    var type = prng.oneOf(gen, [new Y.Array(), new Y.Map()])
+    user.getMap('map').set(key, type)
+    if (type instanceof Y.Array) {
+      type.insert(0, [1, 2, 3, 4])
+    } else {
+      type.set('deepkey', 'deepvalue')
+    }
+  },
+  function _delete (user, gen) {
+    const key = prng.oneOf(gen, ['one', 'two'])
+    user.getMap('map').delete(key)
+  }
+]
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYmapTests10 = tc => {
+  applyRandomTests(tc, mapTransactions, 3)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYmapTests40 = tc => {
+  applyRandomTests(tc, mapTransactions, 40)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYmapTests42 = tc => {
+  applyRandomTests(tc, mapTransactions, 42)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYmapTests43 = tc => {
+  applyRandomTests(tc, mapTransactions, 43)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYmapTests44 = tc => {
+  applyRandomTests(tc, mapTransactions, 44)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYmapTests45 = tc => {
+  applyRandomTests(tc, mapTransactions, 45)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYmapTests46 = tc => {
+  applyRandomTests(tc, mapTransactions, 46)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYmapTests300 = tc => {
+  applyRandomTests(tc, mapTransactions, 300)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYmapTests400 = tc => {
+  applyRandomTests(tc, mapTransactions, 400)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYmapTests500 = tc => {
+  applyRandomTests(tc, mapTransactions, 500)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYmapTests600 = tc => {
+  applyRandomTests(tc, mapTransactions, 600)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYmapTests1000 = tc => {
+  applyRandomTests(tc, mapTransactions, 1000)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYmapTests1800 = tc => {
+  applyRandomTests(tc, mapTransactions, 1800)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYmapTests5000 = tc => {
+  t.skip(!t.production)
+  applyRandomTests(tc, mapTransactions, 5000)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYmapTests10000 = tc => {
+  t.skip(!t.production)
+  applyRandomTests(tc, mapTransactions, 10000)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGeneratingYmapTests100000 = tc => {
+  t.skip(!t.production)
+  applyRandomTests(tc, mapTransactions, 100000)
+}
--- a/tests/y-text.tests.js
+++ b/tests/y-text.tests.js
@@ -0,0 +1,408 @@
+import * as Y from './testHelper.js'
+import * as t from 'lib0/testing.js'
+import * as prng from 'lib0/prng.js'
+import * as math from 'lib0/math.js'
+
+const { init, compare } = Y
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testBasicInsertAndDelete = tc => {
+  const { users, text0 } = init(tc, { users: 2 })
+  let delta
+
+  text0.observe(event => {
+    delta = event.delta
+  })
+
+  text0.delete(0, 0)
+  t.assert(true, 'Does not throw when deleting zero elements with position 0')
+
+  text0.insert(0, 'abc')
+  t.assert(text0.toString() === 'abc', 'Basic insert works')
+  t.compare(delta, [{ insert: 'abc' }])
+
+  text0.delete(0, 1)
+  t.assert(text0.toString() === 'bc', 'Basic delete works (position 0)')
+  t.compare(delta, [{ delete: 1 }])
+
+  text0.delete(1, 1)
+  t.assert(text0.toString() === 'b', 'Basic delete works (position 1)')
+  t.compare(delta, [{ retain: 1 }, { delete: 1 }])
+
+  users[0].transact(() => {
+    text0.insert(0, '1')
+    text0.delete(0, 1)
+  })
+  t.compare(delta, [])
+
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testBasicFormat = tc => {
+  const { users, text0 } = init(tc, { users: 2 })
+  let delta
+  text0.observe(event => {
+    delta = event.delta
+  })
+  text0.insert(0, 'abc', { bold: true })
+  t.assert(text0.toString() === 'abc', 'Basic insert with attributes works')
+  t.compare(text0.toDelta(), [{ insert: 'abc', attributes: { bold: true } }])
+  t.compare(delta, [{ insert: 'abc', attributes: { bold: true } }])
+  text0.delete(0, 1)
+  t.assert(text0.toString() === 'bc', 'Basic delete on formatted works (position 0)')
+  t.compare(text0.toDelta(), [{ insert: 'bc', attributes: { bold: true } }])
+  t.compare(delta, [{ delete: 1 }])
+  text0.delete(1, 1)
+  t.assert(text0.toString() === 'b', 'Basic delete works (position 1)')
+  t.compare(text0.toDelta(), [{ insert: 'b', attributes: { bold: true } }])
+  t.compare(delta, [{ retain: 1 }, { delete: 1 }])
+  text0.insert(0, 'z', { bold: true })
+  t.assert(text0.toString() === 'zb')
+  t.compare(text0.toDelta(), [{ insert: 'zb', attributes: { bold: true } }])
+  t.compare(delta, [{ insert: 'z', attributes: { bold: true } }])
+  // @ts-ignore
+  t.assert(text0._start.right.right.right.content.str === 'b', 'Does not insert duplicate attribute marker')
+  text0.insert(0, 'y')
+  t.assert(text0.toString() === 'yzb')
+  t.compare(text0.toDelta(), [{ insert: 'y' }, { insert: 'zb', attributes: { bold: true } }])
+  t.compare(delta, [{ insert: 'y' }])
+  text0.format(0, 2, { bold: null })
+  t.assert(text0.toString() === 'yzb')
+  t.compare(text0.toDelta(), [{ insert: 'yz' }, { insert: 'b', attributes: { bold: true } }])
+  t.compare(delta, [{ retain: 1 }, { retain: 1, attributes: { bold: null } }])
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testGetDeltaWithEmbeds = tc => {
+  const { text0 } = init(tc, { users: 1 })
+  text0.applyDelta([{
+    insert: { linebreak: 's' }
+  }])
+  t.compare(text0.toDelta(), [{
+    insert: { linebreak: 's' }
+  }])
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testSnapshot = tc => {
+  const { text0 } = init(tc, { users: 1 })
+  const doc0 = /** @type {Y.Doc} */ (text0.doc)
+  doc0.gc = false
+  text0.applyDelta([{
+    insert: 'abcd'
+  }])
+  const snapshot1 = Y.snapshot(doc0)
+  text0.applyDelta([{
+    retain: 1
+  }, {
+    insert: 'x'
+  }, {
+    delete: 1
+  }])
+  const snapshot2 = Y.snapshot(doc0)
+  text0.applyDelta([{
+    retain: 2
+  }, {
+    delete: 3
+  }, {
+    insert: 'x'
+  }, {
+    delete: 1
+  }])
+  const state1 = text0.toDelta(snapshot1)
+  t.compare(state1, [{ insert: 'abcd' }])
+  const state2 = text0.toDelta(snapshot2)
+  t.compare(state2, [{ insert: 'axcd' }])
+  const state2Diff = text0.toDelta(snapshot2, snapshot1)
+  // @ts-ignore Remove userid info
+  state2Diff.forEach(v => {
+    if (v.attributes && v.attributes.ychange) {
+      delete v.attributes.ychange.user
+    }
+  })
+  t.compare(state2Diff, [{ insert: 'a' }, { insert: 'x', attributes: { ychange: { type: 'added' } } }, { insert: 'b', attributes: { ychange: { type: 'removed' } } }, { insert: 'cd' }])
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testSnapshotDeleteAfter = tc => {
+  const { text0 } = init(tc, { users: 1 })
+  const doc0 = /** @type {Y.Doc} */ (text0.doc)
+  doc0.gc = false
+  text0.applyDelta([{
+    insert: 'abcd'
+  }])
+  const snapshot1 = Y.snapshot(doc0)
+  text0.applyDelta([{
+    retain: 4
+  }, {
+    insert: 'e'
+  }])
+  const state1 = text0.toDelta(snapshot1)
+  t.compare(state1, [{ insert: 'abcd' }])
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testToJson = tc => {
+  const { text0 } = init(tc, { users: 1 })
+  text0.insert(0, 'abc', { bold: true })
+  t.assert(text0.toJSON() === 'abc', 'toJSON returns the unformatted text')
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testToDeltaEmbedAttributes = tc => {
+  const { text0 } = init(tc, { users: 1 })
+  text0.insert(0, 'ab', { bold: true })
+  text0.insertEmbed(1, { image: 'imageSrc.png' }, { width: 100 })
+  const delta0 = text0.toDelta()
+  t.compare(delta0, [{ insert: 'a', attributes: { bold: true } }, { insert: { image: 'imageSrc.png' }, attributes: { width: 100 } }, { insert: 'b', attributes: { bold: true } }])
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testToDeltaEmbedNoAttributes = tc => {
+  const { text0 } = init(tc, { users: 1 })
+  text0.insert(0, 'ab', { bold: true })
+  text0.insertEmbed(1, { image: 'imageSrc.png' })
+  const delta0 = text0.toDelta()
+  t.compare(delta0, [{ insert: 'a', attributes: { bold: true } }, { insert: { image: 'imageSrc.png' } }, { insert: 'b', attributes: { bold: true } }], 'toDelta does not set attributes key when no attributes are present')
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testFormattingRemoved = tc => {
+  const { text0 } = init(tc, { users: 1 })
+  text0.insert(0, 'ab', { bold: true })
+  text0.delete(0, 2)
+  t.assert(Y.getTypeChildren(text0).length === 1)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testFormattingRemovedInMidText = tc => {
+  const { text0 } = init(tc, { users: 1 })
+  text0.insert(0, '1234')
+  text0.insert(2, 'ab', { bold: true })
+  text0.delete(2, 2)
+  t.assert(Y.getTypeChildren(text0).length === 3)
+}
+
+const tryGc = () => {
+  if (typeof global !== 'undefined' && global.gc) {
+    global.gc()
+  }
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testLargeFragmentedDocument = tc => {
+  const itemsToInsert = 2000000
+  let update = /** @type {any} */ (null)
+  ;(() => {
+    const doc1 = new Y.Doc()
+    const text0 = doc1.getText('txt')
+    tryGc()
+    t.measureTime(`time to insert ${itemsToInsert} items`, () => {
+      doc1.transact(() => {
+        for (let i = 0; i < itemsToInsert; i++) {
+          text0.insert(0, '0')
+        }
+      })
+    })
+    tryGc()
+    t.measureTime('time to encode document', () => {
+      update = Y.encodeStateAsUpdate(doc1)
+    })
+  })()
+  ;(() => {
+    const doc2 = new Y.Doc()
+    tryGc()
+    t.measureTime(`time to apply ${itemsToInsert} updates`, () => {
+      Y.applyUpdate(doc2, update)
+    })
+  })()
+}
+
+// RANDOM TESTS
+
+let charCounter = 0
+
+const marks = [
+  { bold: true },
+  { italic: true },
+  { italic: true, color: '#888' }
+]
+
+const marksChoices = [
+  undefined,
+  ...marks
+]
+
+/**
+ * @type Array<function(any,prng.PRNG):void>
+ */
+const qChanges = [
+  /**
+   * @param {Y.Doc} y
+   * @param {prng.PRNG} gen
+   */
+  (y, gen) => { // insert text
+    const ytext = y.getText('text')
+    const insertPos = prng.int32(gen, 0, ytext.toString().length)
+    const attrs = prng.oneOf(gen, marksChoices)
+    const text = charCounter++ + prng.word(gen)
+    ytext.insert(insertPos, text, attrs)
+  },
+  /**
+   * @param {Y.Doc} y
+   * @param {prng.PRNG} gen
+   */
+  (y, gen) => { // insert embed
+    const ytext = y.getText('text')
+    const insertPos = prng.int32(gen, 0, ytext.toString().length)
+    ytext.insertEmbed(insertPos, { image: 'https://user-images.githubusercontent.com/5553757/48975307-61efb100-f06d-11e8-9177-ee895e5916e5.png' })
+  },
+  /**
+   * @param {Y.Doc} y
+   * @param {prng.PRNG} gen
+   */
+  (y, gen) => { // delete text
+    const ytext = y.getText('text')
+    const contentLen = ytext.toString().length
+    const insertPos = prng.int32(gen, 0, contentLen)
+    const overwrite = math.min(prng.int32(gen, 0, contentLen - insertPos), 2)
+    ytext.delete(insertPos, overwrite)
+  },
+  /**
+   * @param {Y.Doc} y
+   * @param {prng.PRNG} gen
+   */
+  (y, gen) => { // format text
+    const ytext = y.getText('text')
+    const contentLen = ytext.toString().length
+    const insertPos = prng.int32(gen, 0, contentLen)
+    const overwrite = math.min(prng.int32(gen, 0, contentLen - insertPos), 2)
+    const format = prng.oneOf(gen, marks)
+    ytext.format(insertPos, overwrite, format)
+  },
+  /**
+   * @param {Y.Doc} y
+   * @param {prng.PRNG} gen
+   */
+  (y, gen) => { // insert codeblock
+    const ytext = y.getText('text')
+    const insertPos = prng.int32(gen, 0, ytext.toString().length)
+    const text = charCounter++ + prng.word(gen)
+    const ops = []
+    if (insertPos > 0) {
+      ops.push({ retain: insertPos })
+    }
+    ops.push({ insert: text }, { insert: '\n', format: { 'code-block': true } })
+    ytext.applyDelta(ops)
+  }
+]
+
+/**
+ * @param {any} result
+ */
+const checkResult = result => {
+  for (let i = 1; i < result.testObjects.length; i++) {
+    const p1 = result.users[i].getText('text').toDelta()
+    const p2 = result.users[i].getText('text').toDelta()
+    t.compare(p1, p2)
+  }
+  // Uncomment this to find formatting-cleanup issues
+  // const cleanups = Y.cleanupYTextFormatting(result.users[0].getText('text'))
+  // t.assert(cleanups === 0)
+  return result
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGenerateQuillChanges1 = tc => {
+  const { users } = checkResult(Y.applyRandomTests(tc, qChanges, 1))
+  const cleanups = Y.cleanupYTextFormatting(users[0].getText('text'))
+  t.assert(cleanups === 0)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGenerateQuillChanges2 = tc => {
+  const { users } = checkResult(Y.applyRandomTests(tc, qChanges, 2))
+  const cleanups = Y.cleanupYTextFormatting(users[0].getText('text'))
+  t.assert(cleanups === 0)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGenerateQuillChanges2Repeat = tc => {
+  for (let i = 0; i < 1000; i++) {
+    const { users } = checkResult(Y.applyRandomTests(tc, qChanges, 2))
+    const cleanups = Y.cleanupYTextFormatting(users[0].getText('text'))
+    t.assert(cleanups === 0)
+  }
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGenerateQuillChanges3 = tc => {
+  checkResult(Y.applyRandomTests(tc, qChanges, 3))
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGenerateQuillChanges30 = tc => {
+  checkResult(Y.applyRandomTests(tc, qChanges, 30))
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGenerateQuillChanges40 = tc => {
+  checkResult(Y.applyRandomTests(tc, qChanges, 40))
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGenerateQuillChanges70 = tc => {
+  checkResult(Y.applyRandomTests(tc, qChanges, 70))
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGenerateQuillChanges100 = tc => {
+  checkResult(Y.applyRandomTests(tc, qChanges, 100))
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testRepeatGenerateQuillChanges300 = tc => {
+  checkResult(Y.applyRandomTests(tc, qChanges, 300))
+}
--- a/tests/y-xml.tests.js
+++ b/tests/y-xml.tests.js
@@ -0,0 +1,75 @@
+import { init, compare } from './testHelper.js'
+import * as Y from '../src/index.js'
+
+import * as t from 'lib0/testing.js'
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testSetProperty = tc => {
+  const { testConnector, users, xml0, xml1 } = init(tc, { users: 2 })
+  xml0.setAttribute('height', '10')
+  t.assert(xml0.getAttribute('height') === '10', 'Simple set+get works')
+  testConnector.flushAllMessages()
+  t.assert(xml1.getAttribute('height') === '10', 'Simple set+get works (remote)')
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testEvents = tc => {
+  const { testConnector, users, xml0, xml1 } = init(tc, { users: 2 })
+  /**
+   * @type {any}
+   */
+  let event
+  /**
+   * @type {any}
+   */
+  let remoteEvent
+  xml0.observe(e => {
+    event = e
+  })
+  xml1.observe(e => {
+    remoteEvent = e
+  })
+  xml0.setAttribute('key', 'value')
+  t.assert(event.attributesChanged.has('key'), 'YXmlEvent.attributesChanged on updated key')
+  testConnector.flushAllMessages()
+  t.assert(remoteEvent.attributesChanged.has('key'), 'YXmlEvent.attributesChanged on updated key (remote)')
+  // check attributeRemoved
+  xml0.removeAttribute('key')
+  t.assert(event.attributesChanged.has('key'), 'YXmlEvent.attributesChanged on removed attribute')
+  testConnector.flushAllMessages()
+  t.assert(remoteEvent.attributesChanged.has('key'), 'YXmlEvent.attributesChanged on removed attribute (remote)')
+  xml0.insert(0, [new Y.XmlText('some text')])
+  t.assert(event.childListChanged, 'YXmlEvent.childListChanged on inserted element')
+  testConnector.flushAllMessages()
+  t.assert(remoteEvent.childListChanged, 'YXmlEvent.childListChanged on inserted element (remote)')
+  // test childRemoved
+  xml0.delete(0)
+  t.assert(event.childListChanged, 'YXmlEvent.childListChanged on deleted element')
+  testConnector.flushAllMessages()
+  t.assert(remoteEvent.childListChanged, 'YXmlEvent.childListChanged on deleted element (remote)')
+  compare(users)
+}
+
+/**
+ * @param {t.TestCase} tc
+ */
+export const testTreewalker = tc => {
+  const { users, xml0 } = init(tc, { users: 3 })
+  const paragraph1 = new Y.XmlElement('p')
+  const paragraph2 = new Y.XmlElement('p')
+  const text1 = new Y.XmlText('init')
+  const text2 = new Y.XmlText('text')
+  paragraph1.insert(0, [text1, text2])
+  xml0.insert(0, [paragraph1, paragraph2, new Y.XmlElement('img')])
+  const allParagraphs = xml0.querySelectorAll('p')
+  t.assert(allParagraphs.length === 2, 'found exactly two paragraphs')
+  t.assert(allParagraphs[0] === paragraph1, 'querySelectorAll found paragraph1')
+  t.assert(allParagraphs[1] === paragraph2, 'querySelectorAll found paragraph2')
+  t.assert(xml0.querySelector('p') === paragraph1, 'querySelector found paragraph1')
+  compare(users)
+}
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -0,0 +1,64 @@
+{
+  "compilerOptions": {
+    /* Basic Options */
+    "target": "es2018",
+    "lib": ["es2018", "dom"],                             /* Specify library files to be included in the compilation. */
+    "allowJs": true,                       /* Allow javascript files to be compiled. */
+    "checkJs": true,                       /* Report errors in .js files. */
+    // "jsx": "preserve",                     /* Specify JSX code generation: 'preserve', 'react-native', or 'react'. */
+    "declaration": true,                   /* Generates corresponding '.d.ts' file. */
+    // "declarationMap": true,                /* Generates a sourcemap for each corresponding '.d.ts' file. */
+    // "sourceMap": true,                     /* Generates corresponding '.map' file. */
+    // "outFile": "./dist/yjs.js",                       /* Concatenate and emit output to single file. */
+    "outDir": "./dist",                        /* Redirect output structure to the directory. */
+    "rootDir": "./",                       /* Specify the root directory of input files. Use to control the output directory structure with --outDir. */
+    // "composite": true,                     /* Enable project compilation */
+    // "removeComments": true,                /* Do not emit comments to output. */
+    // "noEmit": true,                        /* Do not emit outputs. */
+    // "importHelpers": true,                 /* Import emit helpers from 'tslib'. */
+    // "downlevelIteration": true,            /* Provide full support for iterables in 'for-of', spread, and destructuring when targeting 'ES5' or 'ES3'. */
+    // "isolatedModules": true,               /* Transpile each file as a separate module (similar to 'ts.transpileModule'). */
+
+    /* Strict Type-Checking Options */
+    "strict": true,                           /* Enable all strict type-checking options. */
+    "noImplicitAny": true,                 /* Raise error on expressions and declarations with an implied 'any' type. */
+    "emitDeclarationOnly": true,
+    // "strictNullChecks": true,              /* Enable strict null checks. */
+    // "strictFunctionTypes": true,           /* Enable strict checking of function types. */
+    // "strictPropertyInitialization": true,  /* Enable strict checking of property initialization in classes. */
+    // "noImplicitThis": true,                /* Raise error on 'this' expressions with an implied 'any' type. */
+    // "alwaysStrict": true,                  /* Parse in strict mode and emit "use strict" for each source file. */
+
+    /* Additional Checks */
+    // "noUnusedLocals": true,                /* Report errors on unused locals. */
+    // "noUnusedParameters": true,            /* Report errors on unused parameters. */
+    // "noImplicitReturns": true,             /* Report error when not all code paths in function return a value. */
+    // "noFallthroughCasesInSwitch": true,    /* Report errors for fallthrough cases in switch statement. */
+
+    /* Module Resolution Options */
+    "moduleResolution": "node",            /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */
+    "baseUrl": "./",                       /* Base directory to resolve non-absolute module names. */
+    "paths": {
+      "yjs": ["./src/index.js"]
+    },                           /* A series of entries which re-map imports to lookup locations relative to the 'baseUrl'. */
+    // "rootDirs": [],                        /* List of root folders whose combined content represents the structure of the project at runtime. */
+    // "typeRoots": [],                       /* List of folders to include type definitions from. */
+    // "types": [],                           /* Type declaration files to be included in compilation. */
+    // "allowSyntheticDefaultImports": true,  /* Allow default imports from modules with no default export. This does not affect code emit, just typechecking. */
+    "esModuleInterop": true,                   /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */
+    // "preserveSymlinks": true,              /* Do not resolve the real path of symlinks. */
+
+    /* Source Map Options */
+    // "sourceRoot": "",                      /* Specify the location where debugger should locate TypeScript files instead of source locations. */
+    // "mapRoot": "",                         /* Specify the location where debugger should locate map files instead of generated locations. */
+    // "inlineSourceMap": true,               /* Emit a single file with source maps instead of having a separate file. */
+    // "inlineSources": true,                 /* Emit the source alongside the sourcemaps within a single file; requires '--inlineSourceMap' or '--sourceMap' to be set. */
+
+    /* Experimental Options */
+    // "experimentalDecorators": true,        /* Enables experimental support for ES7 decorators. */
+    // "emitDecoratorMetadata": true,         /* Enables experimental support for emitting type metadata for decorators. */
+    // "maxNodeModuleJsDepth": 0,
+    // "types": ["./src/utils/typedefs.js"]
+  },
+  "include": ["./src/**/*.js", "./tests/**/*.js"]
+}