fix(repository): Move backend code into subdirectory

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

backend/src/realtime/websocket/websocket.gateway.ts

@@ -0,0 +1,109 @@
+/*
+ * SPDX-FileCopyrightText: 2022 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+import { OnGatewayConnection, WebSocketGateway } from '@nestjs/websockets';
+import { IncomingMessage } from 'http';
+import WebSocket from 'ws';
+
+import { ConsoleLoggerService } from '../../logger/console-logger.service';
+import { NotesService } from '../../notes/notes.service';
+import { PermissionsService } from '../../permissions/permissions.service';
+import { SessionService } from '../../session/session.service';
+import { User } from '../../users/user.entity';
+import { UsersService } from '../../users/users.service';
+import { RealtimeNoteService } from '../realtime-note/realtime-note.service';
+import { WebsocketConnection } from '../realtime-note/websocket-connection';
+import { extractNoteIdFromRequestUrl } from './utils/extract-note-id-from-request-url';
+
+/**
+ * Gateway implementing the realtime logic required for realtime note editing.
+ */
+@WebSocketGateway({ path: '/realtime' })
+export class WebsocketGateway implements OnGatewayConnection {
+  constructor(
+    private readonly logger: ConsoleLoggerService,
+    private noteService: NotesService,
+    private realtimeNoteService: RealtimeNoteService,
+    private userService: UsersService,
+    private permissionsService: PermissionsService,
+    private sessionService: SessionService,
+  ) {
+    this.logger.setContext(WebsocketGateway.name);
+  }
+
+  /**
+   * Handler that is called for each new WebSocket client connection.
+   * Checks whether the requested URL path is valid, whether the requested note
+   * exists and whether the requesting user has access to the note.
+   * Closes the connection to the client if one of the conditions does not apply.
+   *
+   * @param clientSocket The WebSocket client object.
+   * @param request The underlying HTTP request of the WebSocket connection.
+   */
+  async handleConnection(
+    clientSocket: WebSocket,
+    request: IncomingMessage,
+  ): Promise<void> {
+    try {
+      const user = await this.findUserByRequestSession(request);
+      const note = await this.noteService.getNoteByIdOrAlias(
+        extractNoteIdFromRequestUrl(request),
+      );
+
+      if (!(await this.permissionsService.mayRead(user, note))) {
+        //TODO: [mrdrogdrog] inform client about reason of disconnect.
+        this.logger.log(
+          `Access denied to note '${note.id}' for user '${user.username}'`,
+          'handleConnection',
+        );
+        clientSocket.close();
+        return;
+      }
+
+      this.logger.debug(
+        `New realtime connection to note '${note.id}' (${
+          note.publicId
+        }) by user '${user.username}' from ${
+          request.socket.remoteAddress ?? 'unknown'
+        }`,
+      );
+
+      const realtimeNote =
+        await this.realtimeNoteService.getOrCreateRealtimeNote(note);
+
+      const connection = new WebsocketConnection(
+        clientSocket,
+        user,
+        realtimeNote,
+      );
+
+      realtimeNote.addClient(connection);
+    } catch (error: unknown) {
+      this.logger.error(
+        `Error occurred while initializing: ${(error as Error).message}`,
+        (error as Error).stack,
+        'handleConnection',
+      );
+      clientSocket.close();
+    }
+  }
+
+  /**
+   * Finds the {@link User} whose session cookie is saved in the given {@link IncomingMessage}.
+   *
+   * @param request The request that contains the session cookie
+   * @return The found user
+   */
+  private async findUserByRequestSession(
+    request: IncomingMessage,
+  ): Promise<User> {
+    const sessionId =
+      this.sessionService.extractVerifiedSessionIdFromRequest(request);
+    const username = await this.sessionService.fetchUsernameForSessionId(
+      sessionId,
+    );
+    return await this.userService.getUserByUsername(username);
+  }
+}