Y.Text snapshot support (toDelta)

src/utils/Snapshot.js

@@ -1,9 +1,17 @@
 
 import {
   isDeleted,
-  DeleteSet, Item // eslint-disable-line
+  createDeleteSetFromStructStore,
+  getStateVector,
+  getItemCleanStart,
+  createID,
+  iterateDeletedStructs,
+  Transaction, Doc, DeleteSet, Item // eslint-disable-line
 } from '../internals.js'
 
+import * as map from 'lib0/map.js'
+import * as set from 'lib0/set.js'
+
 export class Snapshot {
   /**
    * @param {DeleteSet} ds
@@ -27,9 +35,16 @@ export class Snapshot {
 /**
  * @param {DeleteSet} ds
  * @param {Map<number,number>} sm
+ * @return {Snapshot}
  */
 export const createSnapshot = (ds, sm) => new Snapshot(ds, sm)
 
+/**
+ * @param {Doc} doc
+ * @return {Snapshot}
+ */
+export const createSnapshotFromDoc = doc => createSnapshot(createDeleteSetFromStructStore(doc.store), getStateVector(doc.store))
+
 /**
  * @param {Item} item
  * @param {Snapshot|undefined} snapshot
@@ -40,3 +55,20 @@ export const createSnapshot = (ds, sm) => new Snapshot(ds, sm)
 export const isVisible = (item, snapshot) => snapshot === undefined ? !item.deleted : (
   snapshot.sm.has(item.id.client) && (snapshot.sm.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.sm.forEach((clock, client) => {
+      getItemCleanStart(transaction, store, createID(client, clock))
+    })
+    iterateDeletedStructs(transaction, snapshot.ds, store, item => {})
+    meta.add(snapshot)
+  }
+}

src/utils/Transaction.js

@@ -90,6 +90,11 @@ export class Transaction {
      * @type {any}
      */
     this.origin = origin
+    /**
+     * Stores meta information on the transaction
+     * @type {Map<any,any>}
+     */
+    this.meta = new Map()
   }
 }