From 9f5bc9ddfe9741f863124a96e9afa903f483a2b3 Mon Sep 17 00:00:00 2001
From: Kevin Jahns <kevin.jahns@pm.me>
Date: Sun, 3 May 2020 16:10:58 +0200
Subject: [PATCH] change client id when duplicate content is detected

---
 src/index.js               |  1 +
 src/utils/Doc.js           |  4 +++-
 src/utils/Transaction.js   |  6 ++++++
 tests/consistency.tests.js | 19 +++++++++++++++++++
 tests/index.js             |  3 ++-
 5 files changed, 31 insertions(+), 2 deletions(-)
 create mode 100644 tests/consistency.tests.js

diff --git a/src/index.js b/src/index.js
index 2973dfb8..8fd0e0d4 100644
--- a/src/index.js
+++ b/src/index.js
@@ -47,6 +47,7 @@ export {
   typeMapGetSnapshot,
   iterateDeletedStructs,
   applyUpdate,
+  readUpdate,
   encodeStateAsUpdate,
   encodeStateVector,
   UndoManager,
diff --git a/src/utils/Doc.js b/src/utils/Doc.js
index 58c76467..4eab58f7 100644
--- a/src/utils/Doc.js
+++ b/src/utils/Doc.js
@@ -17,6 +17,8 @@ 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>
@@ -31,7 +33,7 @@ export class Doc extends Observable {
     super()
     this.gc = gc
     this.gcFilter = gcFilter
-    this.clientID = random.uint32()
+    this.clientID = generateNewClientId()
     /**
      * @type {Map<string, AbstractType<YEvent>>}
      */
diff --git a/src/utils/Transaction.js b/src/utils/Transaction.js
index 68459398..2fd0d598 100644
--- a/src/utils/Transaction.js
+++ b/src/utils/Transaction.js
@@ -10,6 +10,7 @@ import {
   findIndexSS,
   callEventHandlerListeners,
   Item,
+  generateNewClientId,
   StructStore, ID, AbstractType, AbstractStruct, YEvent, Doc // eslint-disable-line
 } from '../internals.js'
 
@@ -17,6 +18,7 @@ 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'
 
 /**
@@ -313,6 +315,10 @@ const cleanupTransactions = (transactionCleanups, i) => {
           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')) {
diff --git a/tests/consistency.tests.js b/tests/consistency.tests.js
new file mode 100644
index 00000000..4743ec74
--- /dev/null
+++ 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)
+}
diff --git a/tests/index.js b/tests/index.js
index 7d60fa26..279c4d53 100644
--- a/tests/index.js
+++ b/tests/index.js
@@ -5,6 +5,7 @@ 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'
@@ -14,7 +15,7 @@ if (isBrowser) {
   log.createVConsole(document.body)
 }
 runTests({
-  map, array, text, xml, encoding, undoredo
+  map, array, text, xml, consistency, encoding, undoredo
 }).then(success => {
   /* istanbul ignore next */
   if (isNode) {