enh(y-websocket): always send full diff to server state

Keep an internal ydoc tracking updates that came from the server.
Send updates, that would sync this doc with the current doc state.

Signed-off-by: Max <[email protected]>

src/helpers/yjs.js

@@ -88,6 +88,7 @@ export function applyUpdateMessage(ydoc, updateMessage, origin = 'origin') {
 export function getSteps(queue) {
 	return queue.map(s => encodeArrayBuffer(s))
 		.filter(s => s < 'AQ')
+		.slice(-1)
 }
 
 /**

src/services/y-websocket.js

@@ -37,14 +37,31 @@ messageHandlers[messageSync] = (
 	_messageType,
 ) => {
 	encoding.writeVarUint(encoder, messageSync)
+	const decoderForRemote = decoding.clone(decoder)
 	const syncMessageType = syncProtocol.readSyncMessage(
 		decoder,
 		encoder,
 		provider.doc,
 		provider,
 	)
+	// Message came from the broadcast channel
+	// Do not track in this.remote and do not emit sync.
+	if (!emitSynced) {
+		return
+	}
 	if (
-		emitSynced && syncMessageType === syncProtocol.messageYjsSyncStep2
+		syncMessageType === syncProtocol.messageYjsSyncStep2
+	|| syncMessageType === syncProtocol.messageYjsUpdate
+	) {
+		syncProtocol.readSyncMessage(
+			decoderForRemote,
+			encoding.createEncoder(),
+			provider.remote,
+			provider,
+		)
+	}
+	if (
+		syncMessageType === syncProtocol.messageYjsSyncStep2
     && !provider.synced
 	) {
 		provider.synced = true
@@ -289,6 +306,10 @@ export class WebsocketProvider extends Observable {
 		this.disableBc = disableBc
 		this.wsUnsuccessfulReconnects = 0
 		this.messageHandlers = messageHandlers.slice()
+		/**
+		 * @type {Y.Doc}
+		 */
+		this.remote = new Y.Doc()
 		/**
 		 * @type {boolean}
 		 */
@@ -334,14 +355,17 @@ export class WebsocketProvider extends Observable {
 		}
 		/**
 		 * Listens to Yjs updates and sends them to remote peers (ws and broadcastchannel)
-		 * @param {Uint8Array} update
+		 * @param {Uint8Array} _update
 		 * @param {any} origin
+		 * @param {Y.Doc} doc
 		 */
-		this._updateHandler = (update, origin) => {
+		this._updateHandler = (_update, origin, doc) => {
 			if (origin !== this) {
+				const from = Y.encodeStateVector(this.remote)
+				const fullUpdate = Y.encodeStateAsUpdate(doc, from)
 				const encoder = encoding.createEncoder()
 				encoding.writeVarUint(encoder, messageSync)
-				syncProtocol.writeUpdate(encoder, update)
+				syncProtocol.writeUpdate(encoder, fullUpdate)
 				broadcastMessage(this, encoding.toUint8Array(encoder))
 			}
 		}