refactor: save ydoc state in the database, so it can be restored easier

By storing the ydoc state in the database we can reconnect lost clients easier
and enable offline editing because we continue using the crdt data that has been
used by the client before the connection loss.

Signed-off-by: Tilman Vatteroth <git@tilmanvatteroth.de>

backend/src/realtime/realtime-note/realtime-connection.spec.ts

@@ -27,11 +27,7 @@ jest.mock(
     ({
       ...jest.requireActual('@hedgedoc/commons'),
       // eslint-disable-next-line @typescript-eslint/naming-convention
-      YDocSyncServerAdapter: jest.fn(() =>
-        Mock.of<YDocSyncServerAdapter>({
-          setYDoc: jest.fn(),
-        }),
-      ),
+      YDocSyncServerAdapter: jest.fn(() => Mock.of<YDocSyncServerAdapter>({})),
     } as Record<string, unknown>),
 );
 
@@ -86,9 +82,7 @@ describe('websocket connection', () => {
   });
 
   it('returns the correct sync adapter', () => {
-    const yDocSyncServerAdapter = Mock.of<YDocSyncServerAdapter>({
-      setYDoc: jest.fn(),
-    });
+    const yDocSyncServerAdapter = Mock.of<YDocSyncServerAdapter>({});
     jest
       .spyOn(HedgeDocCommonsModule, 'YDocSyncServerAdapter')
       .mockImplementation(() => yDocSyncServerAdapter);

backend/src/realtime/realtime-note/realtime-connection.ts

@@ -41,8 +41,10 @@ export class RealtimeConnection {
     this.transporter.on('disconnected', () => {
       realtimeNote.removeClient(this);
     });
-    this.yDocSyncAdapter = new YDocSyncServerAdapter(this.transporter);
-    this.yDocSyncAdapter.setYDoc(realtimeNote.getRealtimeDoc());
+    this.yDocSyncAdapter = new YDocSyncServerAdapter(
+      this.transporter,
+      realtimeNote.getRealtimeDoc(),
+    );
     this.realtimeUserStateAdapter = new RealtimeUserStatusAdapter(
       this.user?.username ?? null,
       this.getDisplayName(),

backend/src/realtime/realtime-note/realtime-note-store.spec.ts

@@ -41,6 +41,23 @@ describe('RealtimeNoteStore', () => {
     expect(realtimeNoteConstructorSpy).toHaveBeenCalledWith(
       mockedNote,
       mockedContent,
+      undefined,
+    );
+    expect(realtimeNoteStore.find(mockedNoteId)).toBe(mockedRealtimeNote);
+    expect(realtimeNoteStore.getAllRealtimeNotes()).toStrictEqual([
+      mockedRealtimeNote,
+    ]);
+  });
+
+  it("can create a new realtime note with a yjs state if it doesn't exist yet", () => {
+    const initialYjsState = [1, 2, 3];
+    expect(
+      realtimeNoteStore.create(mockedNote, mockedContent, initialYjsState),
+    ).toBe(mockedRealtimeNote);
+    expect(realtimeNoteConstructorSpy).toHaveBeenCalledWith(
+      mockedNote,
+      mockedContent,
+      initialYjsState,
     );
     expect(realtimeNoteStore.find(mockedNoteId)).toBe(mockedRealtimeNote);
     expect(realtimeNoteStore.getAllRealtimeNotes()).toStrictEqual([

backend/src/realtime/realtime-note/realtime-note-store.ts

@@ -16,15 +16,24 @@ export class RealtimeNoteStore {
    * Creates a new {@link RealtimeNote} for the given {@link Note} and memorizes it.
    *
    * @param note The note for which the realtime note should be created
-   * @param initialContent The initial content for the realtime note
+   * @param initialTextContent the initial text content of realtime doc
+   * @param initialYjsState the initial yjs state. If provided this will be used instead of the text content
    * @throws Error if there is already an realtime note for the given note.
    * @return The created realtime note
    */
-  public create(note: Note, initialContent: string): RealtimeNote {
+  public create(
+    note: Note,
+    initialTextContent: string,
+    initialYjsState?: number[],
+  ): RealtimeNote {
     if (this.noteIdToRealtimeNote.has(note.id)) {
       throw new Error(`Realtime note for note ${note.id} already exists.`);
     }
-    const realtimeNote = new RealtimeNote(note, initialContent);
+    const realtimeNote = new RealtimeNote(
+      note,
+      initialTextContent,
+      initialYjsState,
+    );
     realtimeNote.on('destroy', () => {
       this.noteIdToRealtimeNote.delete(note.id);
     });

backend/src/realtime/realtime-note/realtime-note.service.spec.ts

@@ -17,6 +17,7 @@ import { RealtimeNoteService } from './realtime-note.service';
 
 describe('RealtimeNoteService', () => {
   const mockedContent = 'mockedContent';
+  const mockedYjsState = [1, 2, 3];
   const mockedNoteId = 4711;
   let note: Note;
   let realtimeNote: RealtimeNote;
@@ -37,7 +38,10 @@ describe('RealtimeNoteService', () => {
     jest.useFakeTimers();
   });
 
-  function mockGetLatestRevision(latestRevisionExists: boolean) {
+  function mockGetLatestRevision(
+    latestRevisionExists: boolean,
+    hasYjsState = false,
+  ) {
     jest
       .spyOn(revisionsService, 'getLatestRevision')
       .mockImplementation((note: Note) =>
@@ -45,6 +49,7 @@ describe('RealtimeNoteService', () => {
           ? Promise.resolve(
               Mock.of<Revision>({
                 content: mockedContent,
+                ...(hasYjsState ? { yjsStateVector: mockedYjsState } : {}),
               }),
             )
           : Promise.reject('Revision for note mockedNoteId not found.'),
@@ -106,7 +111,32 @@ describe('RealtimeNoteService', () => {
     ).resolves.toBe(realtimeNote);
 
     expect(realtimeNoteStore.find).toHaveBeenCalledWith(mockedNoteId);
-    expect(realtimeNoteStore.create).toHaveBeenCalledWith(note, mockedContent);
+    expect(realtimeNoteStore.create).toHaveBeenCalledWith(
+      note,
+      mockedContent,
+      undefined,
+    );
+    expect(setIntervalSpy).not.toHaveBeenCalled();
+  });
+
+  it("creates a new realtime note with a yjs state if it doesn't exist yet", async () => {
+    mockGetLatestRevision(true, true);
+    jest.spyOn(realtimeNoteStore, 'find').mockImplementation(() => undefined);
+    jest
+      .spyOn(realtimeNoteStore, 'create')
+      .mockImplementation(() => realtimeNote);
+    mockedAppConfig.persistInterval = 0;
+
+    await expect(
+      realtimeNoteService.getOrCreateRealtimeNote(note),
+    ).resolves.toBe(realtimeNote);
+
+    expect(realtimeNoteStore.find).toHaveBeenCalledWith(mockedNoteId);
+    expect(realtimeNoteStore.create).toHaveBeenCalledWith(
+      note,
+      mockedContent,
+      mockedYjsState,
+    );
     expect(setIntervalSpy).not.toHaveBeenCalled();
   });
 
@@ -192,7 +222,11 @@ describe('RealtimeNoteService', () => {
       .mockImplementation(() => Promise.resolve(Mock.of<Revision>()));
 
     realtimeNote.emit('beforeDestroy');
-    expect(createRevisionSpy).toHaveBeenCalledWith(note, mockedContent);
+    expect(createRevisionSpy).toHaveBeenCalledWith(
+      note,
+      mockedContent,
+      expect.any(Array),
+    );
   });
 
   it('destroys every realtime note on application shutdown', () => {

backend/src/realtime/realtime-note/realtime-note.service.ts

@@ -43,6 +43,7 @@ export class RealtimeNoteService implements BeforeApplicationShutdown {
       .createRevision(
         realtimeNote.getNote(),
         realtimeNote.getRealtimeDoc().getCurrentContent(),
+        realtimeNote.getRealtimeDoc().encodeStateAsUpdate(),
       )
       .catch((reason) => this.logger.error(reason));
   }
@@ -68,9 +69,12 @@ export class RealtimeNoteService implements BeforeApplicationShutdown {
    * @return The created realtime note
    */
   private async createNewRealtimeNote(note: Note): Promise<RealtimeNote> {
-    const initialContent = (await this.revisionsService.getLatestRevision(note))
-      .content;
-    const realtimeNote = this.realtimeNoteStore.create(note, initialContent);
+    const lastRevision = await this.revisionsService.getLatestRevision(note);
+    const realtimeNote = this.realtimeNoteStore.create(
+      note,
+      lastRevision.content,
+      lastRevision.yjsStateVector ?? undefined,
+    );
     realtimeNote.on('beforeDestroy', () => {
       this.saveRealtimeNote(realtimeNote);
     });

backend/src/realtime/realtime-note/realtime-note.spec.ts

@@ -4,15 +4,12 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 import { MessageType, RealtimeDoc } from '@hedgedoc/commons';
-import * as hedgedocCommonsModule from '@hedgedoc/commons';
 import { Mock } from 'ts-mockery';
 
 import { Note } from '../../notes/note.entity';
 import { RealtimeNote } from './realtime-note';
 import { MockConnectionBuilder } from './test-utils/mock-connection';
 
-jest.mock('@hedgedoc/commons');
-
 describe('realtime note', () => {
   let mockedNote: Note;
 
@@ -40,18 +37,13 @@ describe('realtime note', () => {
     expect(sut.hasConnections()).toBeFalsy();
   });
 
-  it('creates a y-doc', () => {
+  it('creates a realtime doc', () => {
     const initialContent = 'nothing';
-    const mockedDoc = new RealtimeDoc(initialContent);
-    const docSpy = jest
-      .spyOn(hedgedocCommonsModule, 'RealtimeDoc')
-      .mockReturnValue(mockedDoc);
     const sut = new RealtimeNote(mockedNote, initialContent);
-    expect(docSpy).toHaveBeenCalledWith(initialContent);
-    expect(sut.getRealtimeDoc()).toBe(mockedDoc);
+    expect(sut.getRealtimeDoc() instanceof RealtimeDoc).toBeTruthy();
   });
 
-  it('destroys y-doc on self-destruction', () => {
+  it('destroys realtime doc on self-destruction', () => {
     const sut = new RealtimeNote(mockedNote, 'nothing');
     const docDestroy = jest.spyOn(sut.getRealtimeDoc(), 'destroy');
     sut.destroy();

backend/src/realtime/realtime-note/realtime-note.ts

@@ -28,12 +28,17 @@ export class RealtimeNote extends EventEmitter2<RealtimeNoteEventMap> {
   private readonly clients = new Set<RealtimeConnection>();
   private isClosing = false;
 
-  constructor(private readonly note: Note, initialContent: string) {
+  constructor(
+    private readonly note: Note,
+    initialTextContent: string,
+    initialYjsState?: number[],
+  ) {
     super();
     this.logger = new Logger(`${RealtimeNote.name} ${note.id}`);
-    this.doc = new RealtimeDoc(initialContent);
+    this.doc = new RealtimeDoc(initialTextContent, initialYjsState);
+    const length = this.doc.getCurrentContent().length;
     this.logger.debug(
-      `New realtime session for note ${note.id} created. Length of initial content: ${initialContent.length} characters`,
+      `New realtime session for note ${note.id} created. Length of initial content: ${length} characters`,
     );
   }
 

backend/src/revisions/revision.entity.ts

@@ -48,6 +48,9 @@ export class Revision {
   @Column()
   length: number;
 
+  @Column('simple-array', { nullable: true })
+  yjsStateVector: null | number[];
+
   /**
    * Date at which the revision was created.
    */
@@ -74,6 +77,7 @@ export class Revision {
     content: string,
     patch: string,
     note: Note,
+    yjsStateVector?: number[],
   ): Omit<Revision, 'id' | 'createdAt'> {
     const newRevision = new Revision();
     newRevision.patch = patch;
@@ -81,6 +85,7 @@ export class Revision {
     newRevision.length = content.length;
     newRevision.note = Promise.resolve(note);
     newRevision.edits = Promise.resolve([]);
+    newRevision.yjsStateVector = yjsStateVector ?? null;
     return newRevision;
   }
 }

backend/src/revisions/revisions.service.ts

@@ -145,6 +145,7 @@ export class RevisionsService {
   async createRevision(
     note: Note,
     newContent: string,
+    yjsStateVector?: number[],
   ): Promise<Revision | undefined> {
     // TODO: Save metadata
     const latestRevision = await this.getLatestRevision(note);
@@ -157,7 +158,7 @@ export class RevisionsService {
       latestRevision.content,
       newContent,
     );
-    const revision = Revision.create(newContent, patch, note);
+    const revision = Revision.create(newContent, patch, note, yjsStateVector);
     return await this.revisionRepository.save(revision);
   }
 }

commons/src/message-transporters/mocked-backend-message-transporter.ts

@@ -6,14 +6,13 @@
 import { RealtimeDoc } from '../y-doc-sync/realtime-doc.js'
 import { ConnectionState, MessageTransporter } from './message-transporter.js'
 import { Message, MessageType } from './message.js'
-import { Doc, encodeStateAsUpdate } from 'yjs'
 
 /**
  * A mocked connection that doesn't send or receive any data and is instantly ready.
  * The only exception is the note content state request that is answered with the given initial content.
  */
 export class MockedBackendMessageTransporter extends MessageTransporter {
-  private readonly doc: Doc
+  private readonly doc: RealtimeDoc
 
   private connected = true
 
@@ -41,10 +40,10 @@ export class MockedBackendMessageTransporter extends MessageTransporter {
   sendMessage<M extends MessageType>(content: Message<M>) {
     if (content.type === MessageType.NOTE_CONTENT_STATE_REQUEST) {
       setTimeout(() => {
-        const payload = Array.from(
-          encodeStateAsUpdate(this.doc, new Uint8Array(content.payload))
-        )
-        this.receiveMessage({ type: MessageType.NOTE_CONTENT_UPDATE, payload })
+        this.receiveMessage({
+          type: MessageType.NOTE_CONTENT_UPDATE,
+          payload: this.doc.encodeStateAsUpdate(content.payload)
+        })
       }, 10)
     }
   }

commons/src/y-doc-sync/realtime-doc.test.ts

@@ -6,11 +6,31 @@
 import { RealtimeDoc } from './realtime-doc.js'
 import { describe, expect, it } from '@jest/globals'
 
-describe('websocket-doc', () => {
-  it('saves the initial content', () => {
+describe('realtime doc', () => {
+  it('saves an initial text content correctly', () => {
     const textContent = 'textContent'
-    const websocketDoc = new RealtimeDoc(textContent)
+    const realtimeDoc = new RealtimeDoc(textContent)
+    expect(realtimeDoc.getCurrentContent()).toBe(textContent)
+  })
 
-    expect(websocketDoc.getCurrentContent()).toBe(textContent)
+  it('will initialize an empty text if no initial content is given', () => {
+    const realtimeDoc = new RealtimeDoc()
+    expect(realtimeDoc.getCurrentContent()).toBe('')
+  })
+
+  it('restores a yjs state vector update correctly', () => {
+    const realtimeDoc = new RealtimeDoc(
+      'notTheVectorText',
+      [
+        1, 1, 221, 208, 165, 230, 3, 0, 4, 1, 15, 109, 97, 114, 107, 100, 111,
+        119, 110, 67, 111, 110, 116, 101, 110, 116, 32, 116, 101, 120, 116, 67,
+        111, 110, 116, 101, 110, 116, 70, 114, 111, 109, 83, 116, 97, 116, 101,
+        86, 101, 99, 116, 111, 114, 85, 112, 100, 97, 116, 101, 0
+      ]
+    )
+
+    expect(realtimeDoc.getCurrentContent()).toBe(
+      'textContentFromStateVectorUpdate'
+    )
   })
 })

commons/src/y-doc-sync/realtime-doc.ts

@@ -3,27 +3,52 @@
  *
  * SPDX-License-Identifier: AGPL-3.0-only
  */
-import { Doc } from 'yjs'
-import { Text as YText } from 'yjs'
+import { EventEmitter2 } from 'eventemitter2'
+import type { EventMap } from 'eventemitter2'
+import {
+  applyUpdate,
+  Doc,
+  encodeStateAsUpdate,
+  encodeStateVector,
+  Text as YText
+} from 'yjs'
 
 const MARKDOWN_CONTENT_CHANNEL_NAME = 'markdownContent'
 
+export interface RealtimeDocEvents extends EventMap {
+  update: (update: number[], origin: unknown) => void
+}
+
 /**
  * This is the implementation of {@link Doc YDoc} which includes additional handlers for message sending and receiving.
  */
-export class RealtimeDoc extends Doc {
+export class RealtimeDoc extends EventEmitter2<RealtimeDocEvents> {
+  private doc: Doc = new Doc()
+  private readonly docUpdateListener: (
+    update: Uint8Array,
+    origin: unknown
+  ) => void
+
   /**
    * Creates a new instance.
    *
    * The new instance is filled with the given initial content.
    *
-   * @param initialContent - the initial content of the {@link Doc YDoc}
+   * @param initialTextContent the initial text content of the {@link Doc YDoc}
+   * @param initialYjsState the initial yjs state. If provided this will be used instead of the text content
    */
-  constructor(initialContent?: string) {
+  constructor(initialTextContent?: string, initialYjsState?: number[]) {
     super()
-    if (initialContent) {
-      this.getMarkdownContentChannel().insert(0, initialContent)
+    if (initialYjsState) {
+      this.applyUpdate(initialYjsState, this)
+    } else if (initialTextContent) {
+      this.getMarkdownContentChannel().insert(0, initialTextContent)
     }
+
+    this.docUpdateListener = (update, origin) => {
+      this.emit('update', Array.from(update), origin)
+    }
+    this.doc.on('update', this.docUpdateListener)
   }
 
   /**
@@ -32,7 +57,7 @@ export class RealtimeDoc extends Doc {
    * @return The markdown channel
    */
   public getMarkdownContentChannel(): YText {
-    return this.getText(MARKDOWN_CONTENT_CHANNEL_NAME)
+    return this.doc.getText(MARKDOWN_CONTENT_CHANNEL_NAME)
   }
 
   /**
@@ -45,4 +70,35 @@ export class RealtimeDoc extends Doc {
   public getCurrentContent(): string {
     return this.getMarkdownContentChannel().toString()
   }
+
+  /**
+   * Encodes the current state of the doc as update so it can be applied to other y-docs.
+   *
+   * @param encodedTargetStateVector The current state vector of the other y-doc. If provided the update will contain only the differences.
+   */
+  public encodeStateAsUpdate(encodedTargetStateVector?: number[]): number[] {
+    const update = encodedTargetStateVector
+      ? new Uint8Array(encodedTargetStateVector)
+      : undefined
+    return Array.from(encodeStateAsUpdate(this.doc, update))
+  }
+
+  public destroy(): void {
+    this.doc.off('update', this.docUpdateListener)
+    this.doc.destroy()
+  }
+
+  /**
+   * Applies an update to the y-doc.
+   *
+   * @param payload The update to apply
+   * @param origin A reference that triggered the update
+   */
+  public applyUpdate(payload: number[], origin: unknown): void {
+    applyUpdate(this.doc, new Uint8Array(payload), origin)
+  }
+
+  public encodeStateVector(): number[] {
+    return Array.from(encodeStateVector(this.doc))
+  }
 }

commons/src/y-doc-sync/y-doc-sync-adapter.test.ts

@@ -68,10 +68,10 @@ describe('message transporter', () => {
       console.debug('s>2 is connected')
     )
 
-    docServer.on('update', (update: Uint8Array, origin: unknown) => {
+    docServer.on('update', (update: number[], origin: unknown) => {
       const message: Message<MessageType.NOTE_CONTENT_UPDATE> = {
         type: MessageType.NOTE_CONTENT_UPDATE,
-        payload: Array.from(update)
+        payload: update
       }
       if (origin !== transporterServerTo1) {
         console.debug('YDoc on Server updated. Sending to Client 1')
@@ -82,32 +82,35 @@ describe('message transporter', () => {
         transporterServerTo2.sendMessage(message)
       }
     })
-    docClient1.on('update', (update: Uint8Array, origin: unknown) => {
+    docClient1.on('update', (update: number[], origin: unknown) => {
       if (origin !== transporterClient1) {
         console.debug('YDoc on client 1 updated. Sending to Server')
       }
     })
-    docClient2.on('update', (update: Uint8Array, origin: unknown) => {
+    docClient2.on('update', (update: number[], origin: unknown) => {
       if (origin !== transporterClient2) {
         console.debug('YDoc on client 2 updated. Sending to Server')
       }
     })
 
-    const yDocSyncAdapter1 = new YDocSyncClientAdapter(transporterClient1)
-    yDocSyncAdapter1.setYDoc(docClient1)
-
-    const yDocSyncAdapter2 = new YDocSyncClientAdapter(transporterClient2)
-    yDocSyncAdapter2.setYDoc(docClient2)
+    const yDocSyncAdapter1 = new YDocSyncClientAdapter(
+      transporterClient1,
+      docClient1
+    )
+    const yDocSyncAdapter2 = new YDocSyncClientAdapter(
+      transporterClient2,
+      docClient2
+    )
 
     const yDocSyncAdapterServerTo1 = new YDocSyncServerAdapter(
-      transporterServerTo1
+      transporterServerTo1,
+      docServer
     )
-    yDocSyncAdapterServerTo1.setYDoc(docServer)
 
     const yDocSyncAdapterServerTo2 = new YDocSyncServerAdapter(
-      transporterServerTo2
+      transporterServerTo2,
+      docServer
     )
-    yDocSyncAdapterServerTo2.setYDoc(docServer)
 
     const waitForClient1Sync = new Promise<void>((resolve) => {
       yDocSyncAdapter1.doAsSoonAsSynced(() => {

commons/src/y-doc-sync/y-doc-sync-adapter.ts

@@ -5,26 +5,37 @@
  */
 import { MessageTransporter } from '../message-transporters/message-transporter.js'
 import { Message, MessageType } from '../message-transporters/message.js'
+import { RealtimeDoc } from './realtime-doc.js'
 import { Listener } from 'eventemitter2'
 import { EventEmitter2 } from 'eventemitter2'
-import { applyUpdate, Doc, encodeStateAsUpdate, encodeStateVector } from 'yjs'
 
 type EventMap = Record<'synced' | 'desynced', () => void>
 
 /**
- * Sends and processes messages that are used to first-synchronize and update a {@link Doc y-doc}.
+ * Sends and processes messages that are used to first-synchronize and update a {@link RealtimeDoc y-doc}.
  */
 export abstract class YDocSyncAdapter {
   public readonly eventEmitter = new EventEmitter2<EventMap>()
 
-  protected doc: Doc | undefined
-
-  private destroyYDocUpdateCallback: undefined | (() => void)
-  private destroyEventListenerCallback: undefined | (() => void)
+  private readonly yDocUpdateListener: Listener
+  private readonly destroyEventListenerCallback: undefined | (() => void)
   private synced = false
 
-  constructor(protected readonly messageTransporter: MessageTransporter) {
-    this.bindDocumentSyncMessageEvents()
+  constructor(
+    protected readonly messageTransporter: MessageTransporter,
+    protected readonly doc: RealtimeDoc
+  ) {
+    this.yDocUpdateListener = doc.on(
+      'update',
+      (update, origin) => {
+        this.processDocUpdate(update, origin)
+      },
+      {
+        objectify: true
+      }
+    ) as Listener
+
+    this.destroyEventListenerCallback = this.bindDocumentSyncMessageEvents()
   }
 
   /**
@@ -51,39 +62,19 @@ export abstract class YDocSyncAdapter {
     return this.synced
   }
 
-  /**
-   * Sets the {@link Doc y-doc} that should be synchronized.
-   *
-   * @param doc the doc to synchronize.
-   */
-  public setYDoc(doc: Doc | undefined): void {
-    this.doc = doc
-
-    this.destroyYDocUpdateCallback?.()
-    if (!doc) {
-      return
-    }
-    const yDocUpdateCallback = this.processDocUpdate.bind(this)
-    doc.on('update', yDocUpdateCallback)
-    this.destroyYDocUpdateCallback = () => doc.off('update', yDocUpdateCallback)
-    this.eventEmitter.emit('desynced')
-  }
-
   public destroy(): void {
-    this.destroyYDocUpdateCallback?.()
+    this.yDocUpdateListener.off()
     this.destroyEventListenerCallback?.()
   }
 
-  protected bindDocumentSyncMessageEvents(): void {
+  protected bindDocumentSyncMessageEvents(): () => void {
     const stateRequestListener = this.messageTransporter.on(
       MessageType.NOTE_CONTENT_STATE_REQUEST,
       (payload) => {
         if (this.doc) {
           this.messageTransporter.sendMessage({
             type: MessageType.NOTE_CONTENT_UPDATE,
-            payload: Array.from(
-              encodeStateAsUpdate(this.doc, new Uint8Array(payload.payload))
-            )
+            payload: this.doc.encodeStateAsUpdate(payload.payload)
           })
         }
       },
@@ -95,35 +86,30 @@ export abstract class YDocSyncAdapter {
       () => {
         this.synced = false
         this.eventEmitter.emit('desynced')
-        this.destroy()
       },
       { objectify: true }
     ) as Listener
 
     const noteContentUpdateListener = this.messageTransporter.on(
       MessageType.NOTE_CONTENT_UPDATE,
-      (payload) => {
-        if (this.doc) {
-          applyUpdate(this.doc, new Uint8Array(payload.payload), this)
-        }
-      },
+      (payload) => this.doc.applyUpdate(payload.payload, this),
       { objectify: true }
     ) as Listener
 
-    this.destroyEventListenerCallback = () => {
+    return () => {
       stateRequestListener.off()
       disconnectedListener.off()
       noteContentUpdateListener.off()
     }
   }
 
-  private processDocUpdate(update: Uint8Array, origin: unknown): void {
+  private processDocUpdate(update: number[], origin: unknown): void {
     if (!this.isSynced() || origin === this) {
       return
     }
     const message: Message<MessageType.NOTE_CONTENT_UPDATE> = {
       type: MessageType.NOTE_CONTENT_UPDATE,
-      payload: Array.from(update)
+      payload: update
     }
 
     this.messageTransporter.sendMessage(message)
@@ -141,7 +127,7 @@ export abstract class YDocSyncAdapter {
     if (this.doc) {
       this.messageTransporter.sendMessage({
         type: MessageType.NOTE_CONTENT_STATE_REQUEST,
-        payload: Array.from(encodeStateVector(this.doc))
+        payload: this.doc.encodeStateVector()
       })
     }
   }

commons/src/y-doc-sync/y-doc-sync-client-adapter.ts

@@ -5,13 +5,23 @@
  */
 import { MessageType } from '../message-transporters/message.js'
 import { YDocSyncAdapter } from './y-doc-sync-adapter.js'
+import { Listener } from 'eventemitter2'
 
 export class YDocSyncClientAdapter extends YDocSyncAdapter {
   protected bindDocumentSyncMessageEvents() {
-    super.bindDocumentSyncMessageEvents()
+    const destroyCallback = super.bindDocumentSyncMessageEvents()
 
-    this.messageTransporter.on(MessageType.NOTE_CONTENT_UPDATE, () => {
-      this.markAsSynced()
-    })
+    const noteContentUpdateListener = this.messageTransporter.on(
+      MessageType.NOTE_CONTENT_UPDATE,
+      () => {
+        this.markAsSynced()
+      },
+      { objectify: true }
+    ) as Listener
+
+    return () => {
+      destroyCallback()
+      noteContentUpdateListener.off()
+    }
   }
 }

commons/src/y-doc-sync/y-doc-sync-server-adapter.ts

@@ -4,11 +4,15 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 import { MessageTransporter } from '../message-transporters/message-transporter.js'
+import { RealtimeDoc } from './realtime-doc.js'
 import { YDocSyncAdapter } from './y-doc-sync-adapter.js'
 
 export class YDocSyncServerAdapter extends YDocSyncAdapter {
-  constructor(readonly messageTransporter: MessageTransporter) {
-    super(messageTransporter)
+  constructor(
+    readonly messageTransporter: MessageTransporter,
+    readonly doc: RealtimeDoc
+  ) {
+    super(messageTransporter, doc)
     this.markAsSynced()
   }
 }

frontend/src/components/editor-page/editor-pane/codemirror-extensions/document-sync/y-text-sync-view-plugin.ts

@@ -17,7 +17,6 @@ const syncAnnotation = Annotation.define()
  */
 export class YTextSyncViewPlugin implements PluginValue {
   private readonly observer: YTextSyncViewPlugin['onYTextUpdate']
-  private firstUpdate = true
 
   constructor(private view: EditorView, private readonly yText: YText, pluginLoaded: () => void) {
     this.observer = this.onYTextUpdate.bind(this)
@@ -47,16 +46,7 @@ export class YTextSyncViewPlugin implements PluginValue {
       },
       [[], 0] as [ChangeSpec[], number]
     )
-    return this.addDeleteAllChanges(changes)
-  }
-
-  private addDeleteAllChanges(changes: ChangeSpec[]): ChangeSpec[] {
-    if (this.firstUpdate) {
-      this.firstUpdate = false
-      return [{ from: 0, to: this.view.state.doc.length, insert: '' }, ...changes]
-    } else {
-      return changes
-    }
+    return changes
   }
 
   public update(update: ViewUpdate): void {

frontend/src/components/editor-page/editor-pane/editor-pane.tsx

@@ -21,12 +21,11 @@ import { useCursorActivityCallback } from './hooks/use-cursor-activity-callback'
 import { useUpdateCodeMirrorReference } from './hooks/use-update-code-mirror-reference'
 import { useBindYTextToRedux } from './hooks/yjs/use-bind-y-text-to-redux'
 import { useCodeMirrorYjsExtension } from './hooks/yjs/use-code-mirror-yjs-extension'
-import { useMarkdownContentYText } from './hooks/yjs/use-markdown-content-y-text'
 import { useOnMetadataUpdated } from './hooks/yjs/use-on-metadata-updated'
 import { useOnNoteDeleted } from './hooks/yjs/use-on-note-deleted'
 import { useRealtimeConnection } from './hooks/yjs/use-realtime-connection'
+import { useRealtimeDoc } from './hooks/yjs/use-realtime-doc'
 import { useReceiveRealtimeUsers } from './hooks/yjs/use-receive-realtime-users'
-import { useYDoc } from './hooks/yjs/use-y-doc'
 import { useYDocSyncClientAdapter } from './hooks/yjs/use-y-doc-sync-client-adapter'
 import { useLinter } from './linter/linter'
 import { MaxLengthWarning } from './max-length-warning/max-length-warning'
@@ -57,8 +56,7 @@ export const EditorPane: React.FC<EditorPaneProps> = ({ scrollState, onScroll, o
   useApplyScrollState(scrollState)
 
   const messageTransporter = useRealtimeConnection()
-  const yDoc = useYDoc(messageTransporter)
-  const yText = useMarkdownContentYText(yDoc)
+  const realtimeDoc = useRealtimeDoc()
   const editorScrollExtension = useCodeMirrorScrollWatchExtension(onScroll)
   const tablePasteExtensions = useCodeMirrorTablePasteExtension()
   const fileInsertExtension = useCodeMirrorFileInsertExtension()
@@ -70,13 +68,13 @@ export const EditorPane: React.FC<EditorPaneProps> = ({ scrollState, onScroll, o
 
   const linterExtension = useLinter()
 
-  const syncAdapter = useYDocSyncClientAdapter(messageTransporter, yDoc)
-  const yjsExtension = useCodeMirrorYjsExtension(yText, syncAdapter)
+  const syncAdapter = useYDocSyncClientAdapter(messageTransporter, realtimeDoc)
+  const yjsExtension = useCodeMirrorYjsExtension(realtimeDoc, syncAdapter)
 
   useOnMetadataUpdated(messageTransporter)
   useOnNoteDeleted(messageTransporter)
 
-  useBindYTextToRedux(yText)
+  useBindYTextToRedux(realtimeDoc)
   useReceiveRealtimeUsers(messageTransporter)
 
   const extensions = useMemo(

frontend/src/components/editor-page/editor-pane/hooks/yjs/use-bind-y-text-to-redux.ts

@@ -4,21 +4,19 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 import { setNoteContent } from '../../../../../redux/note-details/methods'
+import type { RealtimeDoc } from '@hedgedoc/commons'
 import { useEffect } from 'react'
-import type { YText } from 'yjs/dist/src/types/YText'
 
 /**
- * One-Way-synchronizes the text of the given {@link YText y-text} into the global application state.
+ * One-Way-synchronizes the text of the markdown content channel from the given {@link RealtimeDoc realtime doc} into the global application state.
  *
- * @param yText The source text
+ * @param realtimeDoc The {@link RealtimeDoc realtime doc} that contains the markdown content
  */
-export const useBindYTextToRedux = (yText: YText | undefined): void => {
+export const useBindYTextToRedux = (realtimeDoc: RealtimeDoc): void => {
   useEffect(() => {
-    if (!yText) {
-      return
-    }
+    const yText = realtimeDoc.getMarkdownContentChannel()
     const yTextCallback = () => setNoteContent(yText.toString())
     yText.observe(yTextCallback)
     return () => yText.unobserve(yTextCallback)
-  }, [yText])
+  }, [realtimeDoc])
 }

frontend/src/components/editor-page/editor-pane/hooks/yjs/use-code-mirror-yjs-extension.ts

@@ -8,30 +8,33 @@ import { YTextSyncViewPlugin } from '../../codemirror-extensions/document-sync/y
 import type { Extension } from '@codemirror/state'
 import { ViewPlugin } from '@codemirror/view'
 import type { YDocSyncClientAdapter } from '@hedgedoc/commons'
+import type { RealtimeDoc } from '@hedgedoc/commons'
 import { useEffect, useMemo, useState } from 'react'
-import type { Text as YText } from 'yjs'
 
 /**
  * Creates a {@link Extension code mirror extension} that synchronizes an editor with the given {@link YText ytext}.
  *
- * @param yText The source and target for the editor content
+ * @param doc The {@link RealtimeDoc realtime doc} that contains the markdown content text channel
  * @param syncAdapter The sync adapter that processes the communication for content synchronisation.
  * @return the created extension
  */
-export const useCodeMirrorYjsExtension = (yText: YText | undefined, syncAdapter: YDocSyncClientAdapter): Extension => {
+export const useCodeMirrorYjsExtension = (doc: RealtimeDoc, syncAdapter: YDocSyncClientAdapter): Extension => {
   const [editorReady, setEditorReady] = useState(false)
   const synchronized = useApplicationState((state) => state.realtimeStatus.isSynced)
   const connected = useApplicationState((state) => state.realtimeStatus.isConnected)
 
   useEffect(() => {
-    if (editorReady && connected && !synchronized && yText) {
+    if (editorReady && connected && !synchronized) {
       syncAdapter.requestDocumentState()
     }
-  }, [connected, editorReady, syncAdapter, synchronized, yText])
+  }, [connected, editorReady, syncAdapter, synchronized])
 
   return useMemo(
-    () =>
-      yText ? [ViewPlugin.define((view) => new YTextSyncViewPlugin(view, yText, () => setEditorReady(true)))] : [],
-    [yText]
+    () => [
+      ViewPlugin.define(
+        (view) => new YTextSyncViewPlugin(view, doc.getMarkdownContentChannel(), () => setEditorReady(true))
+      )
+    ],
+    [doc]
   )
 }

frontend/src/components/editor-page/editor-pane/hooks/yjs/use-markdown-content-y-text.ts

@@ -1,18 +0,0 @@
-/*
- * SPDX-FileCopyrightText: 2022 The HedgeDoc developers (see AUTHORS file)
- *
- * SPDX-License-Identifier: AGPL-3.0-only
- */
-import type { RealtimeDoc } from '@hedgedoc/commons'
-import { useMemo } from 'react'
-import type { Text as YText } from 'yjs'
-
-/**
- * Extracts the y-text channel that saves the markdown content from the given yDoc.
- *
- * @param yDoc The yjs document from which the yText should be extracted
- * @return the extracted yText channel
- */
-export const useMarkdownContentYText = (yDoc: RealtimeDoc | undefined): YText | undefined => {
-  return useMemo(() => yDoc?.getMarkdownContentChannel(), [yDoc])
-}

frontend/src/components/editor-page/editor-pane/hooks/yjs/use-realtime-connection.ts

@@ -95,7 +95,7 @@ export const useRealtimeConnection = (): MessageTransporter => {
   }, [messageTransporter])
 
   useEffect(() => {
-    const connectedListener = messageTransporter.doAsSoonAsConnected(() => setRealtimeConnectionState(true))
+    const connectedListener = messageTransporter.doAsSoonAsReady(() => setRealtimeConnectionState(true))
     const disconnectedListener = messageTransporter.on('disconnected', () => setRealtimeConnectionState(false), {
       objectify: true
     }) as Listener

frontend/src/components/editor-page/editor-pane/hooks/yjs/use-realtime-doc.ts

@@ -0,0 +1,20 @@
+/*
+ * SPDX-FileCopyrightText: 2022 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+import { RealtimeDoc } from '@hedgedoc/commons'
+import { useEffect, useMemo } from 'react'
+
+/**
+ * Creates a new {@link RealtimeDoc y-doc}.
+ *
+ * @return The created {@link RealtimeDoc y-doc}
+ */
+export const useRealtimeDoc = (): RealtimeDoc => {
+  const doc = useMemo(() => new RealtimeDoc(), [])
+
+  useEffect(() => () => doc.destroy(), [doc])
+
+  return doc
+}

frontend/src/components/editor-page/editor-pane/hooks/yjs/use-y-doc-sync-client-adapter.ts

@@ -5,11 +5,10 @@
  */
 import { setRealtimeSyncedState } from '../../../../../redux/realtime/methods'
 import { Logger } from '../../../../../utils/logger'
-import type { MessageTransporter } from '@hedgedoc/commons'
+import type { MessageTransporter, RealtimeDoc } from '@hedgedoc/commons'
 import { YDocSyncClientAdapter } from '@hedgedoc/commons'
 import type { Listener } from 'eventemitter2'
 import { useEffect, useMemo } from 'react'
-import type { Doc } from 'yjs'
 
 const logger = new Logger('useYDocSyncClient')
 
@@ -17,18 +16,14 @@ const logger = new Logger('useYDocSyncClient')
  * Creates a {@link YDocSyncClientAdapter} and mirrors its sync state to the global application state.
  *
  * @param messageTransporter The {@link MessageTransporter message transporter} that sends and receives messages for the synchronisation
- * @param yDoc The {@link Doc y-doc} that should be synchronized
+ * @param doc The {@link RealtimeDoc realtime doc} that should be synchronized
  * @return the created adapter
  */
 export const useYDocSyncClientAdapter = (
   messageTransporter: MessageTransporter,
-  yDoc: Doc | undefined
+  doc: RealtimeDoc
 ): YDocSyncClientAdapter => {
-  const syncAdapter = useMemo(() => new YDocSyncClientAdapter(messageTransporter), [messageTransporter])
-
-  useEffect(() => {
-    syncAdapter.setYDoc(yDoc)
-  }, [syncAdapter, yDoc])
+  const syncAdapter = useMemo(() => new YDocSyncClientAdapter(messageTransporter, doc), [doc, messageTransporter])
 
   useEffect(() => {
     const onceSyncedListener = syncAdapter.doAsSoonAsSynced(() => {

frontend/src/components/editor-page/editor-pane/hooks/yjs/use-y-doc.ts

@@ -1,30 +0,0 @@
-/*
- * SPDX-FileCopyrightText: 2022 The HedgeDoc developers (see AUTHORS file)
- *
- * SPDX-License-Identifier: AGPL-3.0-only
- */
-import type { MessageTransporter } from '@hedgedoc/commons'
-import { RealtimeDoc } from '@hedgedoc/commons'
-import { useEffect, useState } from 'react'
-
-/**
- * Creates a new {@link RealtimeDoc y-doc}.
- *
- * @return The created {@link RealtimeDoc y-doc}
- */
-export const useYDoc = (messageTransporter: MessageTransporter): RealtimeDoc | undefined => {
-  const [yDoc, setYDoc] = useState<RealtimeDoc>()
-
-  useEffect(() => {
-    messageTransporter.doAsSoonAsConnected(() => {
-      setYDoc(new RealtimeDoc())
-    })
-    messageTransporter.on('disconnected', () => {
-      setYDoc(undefined)
-    })
-  }, [messageTransporter])
-
-  useEffect(() => () => yDoc?.destroy(), [yDoc])
-
-  return yDoc
-}