feat: adds Document.lastChangeTime, which is set to Date.now() whenever a change on the documment has been detected

Author: janthurau

packages/server/src/Document.ts

@@ -1,14 +1,14 @@
+import { Mutex } from "async-mutex";
 import type WebSocket from "ws";
 import {
 	Awareness,
-	removeAwarenessStates,
 	applyAwarenessUpdate,
+	removeAwarenessStates,
 } from "y-protocols/awareness";
-import { applyUpdate, Doc, encodeStateAsUpdate } from "yjs";
-import type { AwarenessUpdate } from "./types.ts";
+import { Doc, applyUpdate, encodeStateAsUpdate } from "yjs";
 import type Connection from "./Connection.ts";
 import { OutgoingMessage } from "./OutgoingMessage.ts";
-import { Mutex } from "async-mutex";
+import type { AwarenessUpdate } from "./types.ts";
 
 export class Document extends Doc {
 	awareness: Awareness;
@@ -42,6 +42,8 @@ export class Document extends Doc {
 
 	saveMutex = new Mutex();
 
+	lastChangeTime = 0;
+
 	/**
 	 * Constructor.
 	 */

packages/server/src/Hocuspocus.ts

@@ -382,6 +382,8 @@ export class Hocuspocus {
 
 		document.onUpdate(
 			(document: Document, connection: Connection, update: Uint8Array) => {
+				document.lastChangeTime = Date.now();
+
 				this.handleDocumentUpdate(
 					document,
 					connection,