dnnai/flutter_asr_client/lib/services/livekit_service.dart

import 'dart:async';
import 'dart:convert';

import 'package:dart_jsonwebtoken/dart_jsonwebtoken.dart';
import 'package:flutter/foundation.dart';
import 'package:livekit_client/livekit_client.dart';
import 'package:asr_client/models/websocket_message.dart';

/// Wraps LiveKit Room connection and relays transcription data messages.
abstract interface class LiveKitService {
  Stream<ServerMessage> get messageStream;
  bool get isConnected;

  Future<void> connect({required String url, required String room, required String identity});
  Future<void> disconnect();
}

final class LiveKitServiceImpl implements LiveKitService {
  LiveKitServiceImpl({Room? room}) : _room = room ?? Room();

  final Room _room;
  final _messageController = StreamController<ServerMessage>.broadcast();
  var _connected = false;
  EventsListener<RoomEvent>? _listener;

  @override
  Stream<ServerMessage> get messageStream => _messageController.stream;

  @override
  bool get isConnected => _connected;

  @override
  Future<void> connect({
    required String url,
    required String room,
    required String identity,
  }) async {
    if (_connected) return;

    final token = _makeToken(room, identity);
    debugPrint('[lk] connecting to $url room=$room');

    // Listen for room events (including connection failures)
    _listener = _room.createListener()
      ..on<DataReceivedEvent>((e) {
        debugPrint('[lk] data received topic=${e.topic} bytes=${e.data.length}');
        if (e.topic == 'transcription') {
          try {
            final json = jsonDecode(utf8.decode(e.data)) as Map<String, dynamic>;
            final message = ServerMessage.fromJson(json);
            _messageController.add(message);
          } catch (ex) {
            debugPrint('[lk] bad data: $ex');
          }
        }
      })
      ..on<RoomDisconnectedEvent>((e) {
        debugPrint('[lk] disconnected: ${e.reason}');
        _connected = false;
      })
      ..on<RoomReconnectingEvent>((e) {
        debugPrint('[lk] reconnecting');
      })
      ..on<RoomReconnectedEvent>((e) {
        debugPrint('[lk] reconnected');
      });

    try {
      await _room.connect(
        '$url',
        token,
      );
    } catch (e, st) {
      debugPrint('[lk] connect failed: $e');
      debugPrint('[lk] stack: $st');
      rethrow;
    }

    debugPrint('[lk] connected, publishing mic...');

    try {
      await _room.localParticipant!.setMicrophoneEnabled(true);
      debugPrint('[lk] mic published');
    } catch (e, st) {
      debugPrint('[lk] mic FAILED: $e\n$st');
    }

    _connected = true;
    _messageController.add(const ConnectedMessage(model: {}));
  }

  @override
  Future<void> disconnect() async {
    if (!_connected) return;
    _connected = false;
    _listener?.dispose();
    _listener = null;
    await _room.disconnect();
  }

  String _makeToken(String room, String identity) {
    // Dev token: for localhost LiveKit Server with key "devkey"
    // In production, tokens should be generated server-side.
    const key = 'devkey';
    const secret = 'secretsecretsecretsecretsecret12';

    final jwt = JWT(
      {
        'iss': key,
        'sub': identity,
        'name': identity,
        'nbf': DateTime.now()
            .subtract(const Duration(minutes: 1))
            .millisecondsSinceEpoch ~/
            1000,
        'exp': DateTime.now()
            .add(const Duration(hours: 6))
            .millisecondsSinceEpoch ~/
            1000,
        'video': {
          'roomJoin': true,
          'room': room,
          'canPublish': true,
          'canSubscribe': true,
          'canPublishData': true,
        },
      },
    );
    return jwt.sign(SecretKey(secret));
  }
}