11. webSocketGateway를 사용한 알림 기능

@WebSocketGateway({
  namespace: 'notification',
  cors: {
    origin: ['http://localhost:3000', 'http://localhost:3001'],
    credentials: true,
  },
})
export class NotificationGateway implements OnGatewayDisconnect {
  @WebSocketServer()
  server: Server;
}

async function bootstrap() {
  const app = await NestFactory.create(AppModule);

  app.useWebSocketAdapter(new IoAdapter(app));
  await app.listen(3000);
}
bootstrap();

export class NotificationGateway implements OnGatewayDisconnect {
  @WebSocketServer()
  server: Server;

  private clients: Map<string, Socket> = new Map();

  @SubscribeMessage('userConnect')
  handleUserConnect(client: Socket, { userId }: { userId: string }) {
    client.data.userId = userId;
    this.clients.set(userId, client);

    console.log(`userId ${userId} connected`);
    return 'webSocket Connected';
  }

  handleDisconnect(client: Socket) {
    const { userId } = client.data;

    if (userId) {
      this.clients.delete(userId);
      console.log(`userId ${userId} disconnected`);
    }
  }
}

export class NotificationGateway implements OnGatewayDisconnect {
  @WebSocketServer()
  server: Server;

  private clients: Map<string, Socket> = new Map();

  sendMessage(userId: string, notification: Notification) {
    const client = this.clients.get(userId);

    if (client) {
      console.log(`emit ${notification.type} to ${userId}`);
      client.emit('notification', notification);
    } else {
      console.log(`Client not connected: ${userId}`);
    }
  }
}

@Controller('comments')
export class CommentsController {
  constructor(
    private reportService: ReportService,
    private commentService: CommentService,
    private notificationService: NotificationService,
    private notificationGateway: NotificationGateway,
  ) {}

  async sendNotification(parentId, userId) {
    const report = await this.reportService.getReport(parentId);

    if (report.user.id !== userId) {
      const noti = await this.notificationService.createNotification(
        report.user.id,
        {
          senderId: userId,
          reportId: parentId,
          type: 'NEW_COMMENT_ON_REPORT',
        },
      );

      this.notificationGateway.sendMessage(report.user.id, noti);
    }
  }
}