service-teams-browser-bot/src/server/gatewayClient.ts

import WebSocket from 'ws';
import { Logger } from 'winston';
import { 
  GatewayToBot, 
  BotToGateway, 
  TranscriptMessage, 
  StatusMessage,
  BotState 
} from '../types';
import { logger } from '../utils/logger';

export interface GatewayClientCallbacks {
  onJoinMeeting: (sessionId: string, meetingUrl: string, botName?: string) => void;
  onLeaveMeeting: (sessionId: string) => void;
  onPlayAudio: (sessionId: string, audioData: string, format: 'mp3' | 'wav' | 'pcm') => void;
  onDisconnect: () => void;
}

/**
 * WebSocket client that connects to the Gateway.
 * Receives commands (join, leave, play audio) and sends events (transcript, status).
 */
export class GatewayClient {
  private _wsUrl: string;
  private _ws: WebSocket | null = null;
  private _callbacks: GatewayClientCallbacks;
  private _logger: Logger;
  private _reconnectAttempts: number = 0;
  private _maxReconnectAttempts: number = 10;
  private _reconnectDelay: number = 1000;
  private _isConnecting: boolean = false;
  private _shouldReconnect: boolean = true;

  constructor(wsUrl: string, callbacks: GatewayClientCallbacks) {
    this._wsUrl = wsUrl;
    this._callbacks = callbacks;
    this._logger = logger.child({ component: 'GatewayClient' });
  }

  /**
   * Connect to the Gateway WebSocket.
   */
  async connect(): Promise<void> {
    if (this._isConnecting || (this._ws && this._ws.readyState === WebSocket.OPEN)) {
      return;
    }

    this._isConnecting = true;
    this._shouldReconnect = true;

    return new Promise((resolve, reject) => {
      this._logger.info(`Connecting to Gateway: ${this._wsUrl}`);

      this._ws = new WebSocket(this._wsUrl);

      this._ws.on('open', () => {
        this._logger.info('Connected to Gateway');
        this._isConnecting = false;
        this._reconnectAttempts = 0;
        resolve();
      });

      this._ws.on('message', (data) => {
        this._handleMessage(data.toString());
      });

      this._ws.on('close', (code, reason) => {
        this._logger.warn(`Gateway connection closed: ${code} - ${reason}`);
        this._isConnecting = false;
        this._ws = null;
        this._callbacks.onDisconnect();

        if (this._shouldReconnect) {
          this._scheduleReconnect();
        }
      });

      this._ws.on('error', (error) => {
        this._logger.error('Gateway WebSocket error:', error);
        this._isConnecting = false;

        if (this._reconnectAttempts === 0) {
          reject(error);
        }
      });
    });
  }

  /**
   * Disconnect from the Gateway.
   */
  disconnect(): void {
    this._shouldReconnect = false;

    if (this._ws) {
      this._ws.close(1000, 'Client disconnecting');
      this._ws = null;
    }
  }

  /**
   * Send a transcript to the Gateway.
   */
  sendTranscript(
    sessionId: string,
    speaker: string,
    text: string,
    isFinal: boolean = true
  ): void {
    const message: TranscriptMessage = {
      type: 'transcript',
      sessionId,
      transcript: {
        speaker,
        text,
        timestamp: new Date().toISOString(),
        isFinal,
      },
    };

    this._send(message);
  }

  /**
   * Send a status update to the Gateway.
   */
  sendStatus(
    sessionId: string,
    status: StatusMessage['status'],
    message?: string
  ): void {
    const statusMessage: StatusMessage = {
      type: 'status',
      sessionId,
      status,
      message,
    };

    this._send(statusMessage);
  }

  /**
   * Map BotState to StatusMessage status.
   */
  mapStateToStatus(state: BotState): StatusMessage['status'] {
    switch (state) {
      case 'launching':
      case 'navigating':
        return 'connecting';
      case 'in_lobby':
        return 'in_lobby';
      case 'in_meeting':
        return 'joined';
      case 'leaving':
      case 'disconnected':
        return 'left';
      case 'error':
        return 'error';
      default:
        return 'connecting';
    }
  }

  /**
   * Handle incoming messages from the Gateway.
   */
  private _handleMessage(data: string): void {
    try {
      const message = JSON.parse(data) as GatewayToBot;

      this._logger.debug('Received message:', { type: message.type });

      switch (message.type) {
        case 'joinMeeting':
          this._callbacks.onJoinMeeting(
            message.sessionId,
            message.meetingUrl,
            message.botName
          );
          break;

        case 'leaveMeeting':
          this._callbacks.onLeaveMeeting(message.sessionId);
          break;

        case 'playAudio':
          this._callbacks.onPlayAudio(
            message.sessionId,
            message.audio.data,
            message.audio.format
          );
          break;

        default:
          this._logger.warn('Unknown message type:', (message as any).type);
      }
    } catch (error) {
      this._logger.error('Error parsing Gateway message:', error);
    }
  }

  /**
   * Send a message to the Gateway.
   */
  private _send(message: BotToGateway): void {
    if (!this._ws || this._ws.readyState !== WebSocket.OPEN) {
      this._logger.warn('Cannot send message - not connected');
      return;
    }

    try {
      this._ws.send(JSON.stringify(message));
    } catch (error) {
      this._logger.error('Error sending message:', error);
    }
  }

  /**
   * Schedule a reconnection attempt.
   */
  private _scheduleReconnect(): void {
    if (this._reconnectAttempts >= this._maxReconnectAttempts) {
      this._logger.error('Max reconnection attempts reached');
      return;
    }

    this._reconnectAttempts++;
    const delay = this._reconnectDelay * Math.pow(2, this._reconnectAttempts - 1);

    this._logger.info(`Reconnecting in ${delay}ms (attempt ${this._reconnectAttempts}/${this._maxReconnectAttempts})`);

    setTimeout(() => {
      this.connect().catch((error) => {
        this._logger.error('Reconnection failed:', error);
      });
    }, delay);
  }
}