deepvoice_client/lib/data/services/volcano_tts_api_service.dart

import 'dart:async';
import 'dart:convert';
import 'dart:typed_data';
import 'dart:io' as io;
import 'dart:math' as math;
import 'package:flutter/foundation.dart';
import 'package:get/get.dart';
import 'package:flutter_dotenv/flutter_dotenv.dart';
import 'package:web_socket_channel/web_socket_channel.dart';
import 'package:web_socket_channel/io.dart';
import 'package:uuid/uuid.dart';
import 'package:just_audio/just_audio.dart';
import 'package:path_provider/path_provider.dart';

/// 火山语音合成双向流式API服务
class VolcanoTtsApiService extends GetxController {
  // 协议常量
  static const int _protocolVersion = 0x0001;
  static const int _defaultHeaderSize = 0x0001;
  
  // 消息类型
  static const int _fullClientRequest = 0x0001;
  static const int _audioOnlyResponse = 0x000B;
  static const int _fullServerResponse = 0x0009;
  static const int _errorInformation = 0x000F;
  
  // 消息类型特定标志
  static const int _msgTypeFlagNoSeq = 0x0000;
  static const int _msgTypeFlagPositiveSeq = 0x0001;
  static const int _msgTypeFlagLastNoSeq = 0x0002;
  static const int _msgTypeFlagNegativeSeq = 0x0003;
  static const int _msgTypeFlagWithEvent = 0x0004;
  
  // 消息序列化
  static const int _noSerialization = 0x0000;
  static const int _jsonSerialization = 0x0001;
  
  // 消息压缩
  static const int _compressionNo = 0x0000;
  static const int _compressionGzip = 0x0001;
  
  // 事件类型
  static const int eventNone = 0;
  static const int eventStartConnection = 1;
  static const int eventFinishConnection = 2;
  static const int eventConnectionStarted = 50;
  static const int eventConnectionFailed = 51;
  static const int eventConnectionFinished = 52;
  static const int eventStartSession = 100;
  static const int eventFinishSession = 102;
  static const int eventSessionStarted = 150;
  static const int eventSessionFinished = 152;
  static const int eventSessionFailed = 153;
  static const int eventTaskRequest = 200;
  static const int eventTtsSentenceStart = 350;
  static const int eventTtsSentenceEnd = 351;
  static const int eventTtsResponse = 352;
  
  // 服务URL
  static const String _serviceUrl = 'wss://openspeech.bytedance.com/api/v3/tts/bidirection';
  
  // 配置参数
  final String _appId;
  final String _token;
  final String _resourceId;
  
  // WebSocket连接
  WebSocketChannel? _channel;
  
  // 会话ID
  String? _sessionId;
  String? _connectionId;
  
  // 状态控制
  bool _isConnected = false;
  bool _isSessionActive = false;
  
  // 音频数据控制器
  final _audioDataController = StreamController<Uint8List>.broadcast();
  Stream<Uint8List> get audioStream => _audioDataController.stream;
  
  // 事件控制器
  final _eventController = StreamController<Map<String, dynamic>>.broadcast();
  Stream<Map<String, dynamic>> get eventStream => _eventController.stream;
  
  // 当前状态
  final isConnecting = false.obs;
  final isConnected = false.obs;
  final isSynthesizing = false.obs;
  
  // 音频播放器
  final AudioPlayer _audioPlayer = AudioPlayer();
  
  // 播放列表 - 用于连续播放
  final ConcatenatingAudioSource _playlist = ConcatenatingAudioSource(children: []);
  bool _playlistInitialized = false;
  
  // 音频数据控制器 - 用于流式播放
  final StreamController<List<int>> _audioStreamController = StreamController<List<int>>();
  
  // 是否正在播放
  final RxBool _isPlaying = false.obs;
  bool get isPlaying => _isPlaying.value;
  
  // 默认发音人 - 使用预定义的值
  final String defaultSpeaker = 'zh_female_yuanqinvyou_moon_bigtts';
  
  // 音频缓冲区
  final List<Uint8List> _audioBuffer = [];
  
  // 检查是否需要准备下一个音频项目
  DateTime? _lastCheckTime;
  int? _lastCheckedIndex;
  
  // 构造函数
  VolcanoTtsApiService() : 
    _appId = dotenv.env['VOLCANO_TTS_APP_ID'] ?? '',
    _token = dotenv.env['VOLCANO_TTS_APP_TOKEN'] ?? '',
    _resourceId = dotenv.env['VOLCANO_TTS_RESOURCE_ID'] ?? '' {
    if (_appId.isEmpty || _token.isEmpty) {
      throw Exception('火山语音配置信息不完整，请检查环境变量 VOLCANO_TTS_APP_ID 和 VOLCANO_TTS_APP_TOKEN');
    }
  }
  
  @override
  void onInit() {
    super.onInit();
    // 初始化时不自动连接，等待需要时再连接
    
    // 设置音频播放器状态监听
    _setupAudioPlayerListeners();
    
    // 初始化播放列表
    _initializePlaylist();
  }
  
  /// 初始化播放列表
  Future<void> _initializePlaylist() async {
    try {
      if (!_playlistInitialized) {
        // 设置音频属性，启用无缝播放
        await _audioPlayer.setLoopMode(LoopMode.off);
        await _audioPlayer.setShuffleModeEnabled(false);
        
        // 设置自动连续播放
        await _audioPlayer.setAutomaticallyWaitsToMinimizeStalling(false);
        
        // 设置音频源
        await _audioPlayer.setAudioSource(_playlist, initialIndex: 0, initialPosition: Duration.zero);
        
        _playlistInitialized = true;
        if (kDebugMode) {
          print('播放列表初始化成功');
        }
      }
    } catch (e) {
      if (kDebugMode) {
        print('初始化播放列表失败: $e');
      }
      // 不抛出异常，避免中断整个流程
    }
  }
  
  /// 设置音频播放器状态监听
  void _setupAudioPlayerListeners() {
    _audioPlayer.playerStateStream.listen((state) {
      final processingState = state.processingState;
      final playing = state.playing;
      
      if (processingState == ProcessingState.ready && playing) {
        _isPlaying.value = true;
      } else {
        _isPlaying.value = false;
      }
    });
    
    _audioPlayer.processingStateStream.listen((state) {
      if (state == ProcessingState.completed) {
        // 播放完成后检查播放列表是否为空
        if (_playlist.length > 0) {
          final currentIndex = _audioPlayer.currentIndex;
          
          // 自动播放下一个项目
          _advanceToNextItem();
        } else {
          // 播放列表为空，标记为未播放状态
          _isPlaying.value = false;
        }
      }
    });
    
    // 监听序列状态变化
    _audioPlayer.sequenceStateStream.listen((sequenceState) {
      if (sequenceState == null) return;
      
      // 如果当前是最后一个项目且播放已完成，标记播放完成
      if (sequenceState.currentIndex == sequenceState.sequence.length - 1 && 
          _audioPlayer.processingState == ProcessingState.completed) {
        _isPlaying.value = false;
      }
    });
    
    // 监听位置变化，但减少检查频率
    DateTime _lastPositionCheck = DateTime.now();
    _audioPlayer.positionStream.listen((position) {
      // 限制检查频率，每500毫秒检查一次
      final now = DateTime.now();
      if (now.difference(_lastPositionCheck).inMilliseconds >= 500) {
        _lastPositionCheck = now;
        _checkForNextItem(position);
      }
    });
  }
  
  /// 检查是否需要准备下一个音频项目
  Future<void> _checkForNextItem(Duration position) async {
    // 只有在播放中且有下一个项目时才检查
    if (!_isPlaying.value || _audioPlayer.currentIndex == null) return;
    
    final currentIndex = _audioPlayer.currentIndex!;
    final sequenceState = _audioPlayer.sequenceState;
    
    // 如果没有序列状态，则不需要准备
    if (sequenceState == null) return;
    
    // 防抖动：如果在短时间内（200毫秒）对同一个索引进行了检查，则跳过
    final now = DateTime.now();
    if (_lastCheckTime != null && 
        _lastCheckedIndex == currentIndex && 
        now.difference(_lastCheckTime!) < const Duration(milliseconds: 200)) {
      return;
    }
    
    // 更新最后检查时间和索引
    _lastCheckTime = now;
    _lastCheckedIndex = currentIndex;
    
    // 获取当前项目的总时长
    final duration = _audioPlayer.duration;
    if (duration == null) return;
    
    // 如果是最后一个项目，不需要预加载
    final isLastItem = currentIndex >= sequenceState.sequence.length - 1;
    
    // 如果接近结束（剩余时间小于200毫秒），准备下一个项目或完成播放
    if (duration - position <= const Duration(milliseconds: 200) && !isLastItem) {
      // 让播放器自然过渡到下一个项目
    }
  }
  
  /// 前进到播放列表中的下一个项目
  Future<void> _advanceToNextItem() async {
    try {
      if (_playlist.length == 0) return;
      
      // 获取当前索引和序列状态
      final currentIndex = _audioPlayer.currentIndex;
      final sequenceState = _audioPlayer.sequenceState;
      
      if (sequenceState == null) {
        // 如果没有序列状态，直接开始播放
        await _audioPlayer.seek(Duration.zero, index: 0);
        await _audioPlayer.play();
        return;
      }
      
      // 如果当前索引无效，从头开始播放
      if (currentIndex == null || currentIndex < 0) {
        await _audioPlayer.seek(Duration.zero, index: 0);
        await _audioPlayer.play();
        return;
      }
      
      // 计算下一个索引
      final nextIndex = currentIndex + 1;
      
      // 检查是否还有下一个项目
      if (nextIndex < sequenceState.sequence.length) {
        // 跳转到下一个项目并开始播放
        await _audioPlayer.seek(Duration.zero, index: nextIndex);
        await _audioPlayer.play();
      } else {
        // 已经是最后一个项目
        
        // 确保最后一个项目播放完成
        if (_audioPlayer.position < _audioPlayer.duration!) {
          await _audioPlayer.seek(_audioPlayer.duration!);
        }
      }
    } catch (e) {
      // 简单记录错误，不做复杂处理
    }
  }
  
  /// 连接到火山语音服务
  Future<bool> connect() async {
    if (_isConnected) {
      return true; // 已经连接
    }
    print('连接');

    try {
      isConnecting.value = true;
      

      
      // 生成连接ID
      _connectionId = const Uuid().v4();
      
      // 创建WebSocket连接
      final uri = Uri.parse(_serviceUrl);
      
      if (!kIsWeb && (io.Platform.isAndroid || io.Platform.isIOS || io.Platform.isMacOS || io.Platform.isLinux || io.Platform.isWindows)) {
        // 移动平台和桌面平台 - 使用IOWebSocketChannel

        
        _channel = IOWebSocketChannel.connect(
          uri,
          headers: {
            'X-Api-App-Key': _appId,
            'X-Api-Access-Key': _token,
            'X-Api-Resource-Id': _resourceId,
            'X-Api-Connect-Id': _connectionId!,
          },
        );
      } else {
        // Web平台 - 使用WebSocketChannel
        // 注意：在Web平台上，我们无法直接设置WebSocket头部
        // 这可能会导致认证失败，需要与服务提供商确认Web平台的认证方式

        _channel = WebSocketChannel.connect(uri);
      }
      
      // 监听消息
      _channel!.stream.listen(
        _handleMessage,
        onError: _handleError,
        onDone: _handleDone,
        cancelOnError: false,
      );
      

      
      // 发送开始连接事件
      await _startConnection();
      
      // 等待连接成功
      final completer = Completer<bool>();
      
      // 设置超时
      final timeout = Timer(const Duration(seconds: 10), () {
        if (!completer.isCompleted) {
          completer.complete(false);
          _handleError(Exception('连接超时'));
        }
      });
      
      
      // 监听连接事件
      final subscription = eventStream.listen((event) {

        if (event['eventType'] == 'connectionStarted') {
          if (!completer.isCompleted) {
            if (kDebugMode) {
              print('连接成功');
            }
            completer.complete(true);
            timeout.cancel();
          }
        } else if (event['eventType'] == 'connectionFailed') {
          if (!completer.isCompleted) {
            if (kDebugMode) {
              print('连接失败: ${event['error']}');
            }
            completer.complete(false);
            timeout.cancel();
          }
        }
      });
      
      // 等待连接结果
      final result = await completer.future;
      subscription.cancel();
      
      if (result) {
        _isConnected = true;
        isConnected.value = true;

      } 
      return result;
    } catch (e) {
      if (kDebugMode) {
        print('连接过程中发生异常: $e');
      }
      _handleError(e);
      return false;
    } finally {
      isConnecting.value = false;
    }
  }
  
  /// 开始TTS会话
  Future<bool> startSession(String speaker) async {
    print('开始会话');
    if (!_isConnected) {
      final connected = await connect();
      if (!connected) return false;
    }
    
    if (_isSessionActive) {
      return true; // 会话已经活跃
    }
    
    try {
      // 生成会话ID
      _sessionId = const Uuid().v4().replaceAll('-', '');
      
      // 发送开始会话事件
      await _startTtsSession(speaker);
      
      // 等待会话开始
      final completer = Completer<bool>();
      
      // 设置超时
      final timeout = Timer(const Duration(seconds: 10), () {
        if (!completer.isCompleted) {
          completer.complete(false);
          _handleError(Exception('会话开始超时'));
        }
      });
      
      // 监听会话事件
      final subscription = eventStream.listen((event) {
        if (event['eventType'] == 'sessionStarted') {
          if (!completer.isCompleted) {
            completer.complete(true);
            timeout.cancel();
          }
        } else if (event['eventType'] == 'sessionFailed') {
          if (!completer.isCompleted) {
            completer.complete(false);
            timeout.cancel();
          }
        }
      });
      
      // 等待会话结果
      final result = await completer.future;
      subscription.cancel();
      
      if (result) {
        _isSessionActive = true;
      }
      
      return result;
    } catch (e) {
      _handleError(e);
      return false;
    }
  }
  
  /// 合成文本
  Future<bool> synthesize(String text, String speaker) async {
    if (!_isConnected) {
      final connected = await connect();
      if (!connected) return false;
    }
    
    if (!_isSessionActive) {
      final sessionStarted = await startSession(speaker);
      if (!sessionStarted) return false;
    }
    
    try {
      isSynthesizing.value = true;
      
      // 发送合成请求
      await _sendTtsMessage(speaker, text);
      
      return true;
    } catch (e) {
      _handleError(e);
      return false;
    }
  }
  
  /// 结束会话
  Future<bool> endSession() async {
    if (!_isSessionActive) {
      return true; // 没有活跃会话
    }
    print('结束会话');
  
    try {
      // 发送结束会话事件
      await _finishSession();
      
      // 等待会话结束
      final completer = Completer<bool>();
      
      // 设置超时
      final timeout = Timer(const Duration(seconds: 5), () {
        if (!completer.isCompleted) {
          completer.complete(true); // 超时也认为成功
        }
      });
      
      // 监听会话事件
      final subscription = eventStream.listen((event) {
        if (event['eventType'] == 'sessionFinished') {
          if (!completer.isCompleted) {
            completer.complete(true);
            timeout.cancel();
          }
        }
      });
      
      // 等待会话结果
      final result = await completer.future;
      subscription.cancel();
      
      _isSessionActive = false;
      isSynthesizing.value = false;
      
      return result;
    } catch (e) {
      _handleError(e);
      return false;
    }
  }
  
  /// 断开连接
  Future<bool> disconnect() async {

    print('断开连接');
    if (!_isConnected) {
      return true; // 已经断开
    }
    
    try {
      // 如果有活跃会话，先结束会话
      if (_isSessionActive) {
        await endSession();
      }
      
      // 发送结束连接事件
      await _finishConnection();
      
      // 等待连接结束
      final completer = Completer<bool>();
      
      // 设置超时
      final timeout = Timer(const Duration(seconds: 5), () {
        if (!completer.isCompleted) {
          completer.complete(true); // 超时也认为成功
        }
      });
      
      // 监听连接事件
      final subscription = eventStream.listen((event) {
        if (event['eventType'] == 'connectionFinished') {
          if (!completer.isCompleted) {
            completer.complete(true);
            timeout.cancel();
          }
        }
      });
      
      // 等待连接结果
      final result = await completer.future;
      subscription.cancel();
      
      // 关闭WebSocket连接
      await _channel?.sink.close();
      _channel = null;
      
      _isConnected = false;
      _isSessionActive = false;
      isConnected.value = false;
      isSynthesizing.value = false;
      
      return result;
    } catch (e) {
      _handleError(e);
      return false;
    }
  }
  
  /// 处理接收到的消息
  void _handleMessage(dynamic message) {
    try {
      if (message is! List<int>) {
        _handleError(Exception('收到非二进制消息: $message'));
        return;
      }
      
      // 转换为Uint8List以提高处理效率
      final messageData = Uint8List.fromList(message);
      
      final response = _parseResponse(messageData);
      if (response == null) {
        _handleError(Exception('解析响应失败'));
        return;
      }
      
      // 处理事件
      final event = response['event'] as int?;
      if (event != null) {
        switch (event) {
          case eventConnectionStarted:
            _eventController.add({'eventType': 'connectionStarted'});
            break;
          case eventConnectionFailed:
            _eventController.add({
              'eventType': 'connectionFailed',
              'error': response['errorDetails'] ?? '连接失败'
            });
            break;
          case eventSessionStarted:
            _eventController.add({'eventType': 'sessionStarted'});
            break;
          case eventSessionFailed:
            _eventController.add({
              'eventType': 'sessionFailed',
              'error': response['errorDetails'] ?? '会话失败'
            });
            break;
          case eventTtsSentenceStart:
            _eventController.add({'eventType': 'ttsSentenceStart'});
            _prepareAudioStream();
            break;
          case eventTtsSentenceEnd:
            _eventController.add({'eventType': 'ttsSentenceEnd'});
            // 结束音频流
            _finishAudioStream();
            break;
          case eventTtsResponse:
            // 处理音频数据
            final payload = response['payload'] as Uint8List?;
            if (payload != null && payload.isNotEmpty) {
              try {
                _eventController.add({'eventType': 'ttsResponse'});
                _audioDataController.add(payload);
                
                // 将音频数据添加到流中
                _addAudioData(payload);
              } catch (audioError) {
                // 继续处理，不中断整个流程
              }
            }
            break;
          case eventSessionFinished:
            _eventController.add({'eventType': 'sessionFinished'});
            break;
          case eventConnectionFinished:
            _eventController.add({'eventType': 'connectionFinished'});
            break;
          default:
            _eventController.add({'eventType': 'unknown', 'eventCode': event});
            break;
        }
      }
    } catch (e) {
      _handleError(e);
    }
  }
  
  /// 准备音频流
  void _prepareAudioStream() {
    try {
      // 清空音频缓冲区
      _audioBuffer.clear();

    } catch (e) {
      if (kDebugMode) {
        print('准备音频流时发生错误: $e');
      }
    }
  }
  
  /// 添加音频数据到流
  void _addAudioData(Uint8List data) {
    try {
      // 将音频数据添加到缓冲区
      if (data.isNotEmpty) {
        _audioBuffer.add(data);

      }
    } catch (e) {
      if (kDebugMode) {
        print('添加音频数据到流时发生错误: $e');
      }
      // 不抛出异常，继续处理
    }
  }
  
  /// 结束音频流
  void _finishAudioStream() {
    try {
      if (_audioBuffer.isNotEmpty) {

        
        // 合并所有音频数据
        final totalSize = _audioBuffer.fold<int>(0, (sum, data) => sum + data.length);
        final mergedData = Uint8List(totalSize);
        
        int offset = 0;
        for (final data in _audioBuffer) {
          mergedData.setRange(offset, offset + data.length, data);
          offset += data.length;
        }
        
        // 清空缓冲区
        _audioBuffer.clear();
        
        // 将合并后的数据添加到播放列表
        _addToPlaylist(mergedData);
      } else {

      }
    } catch (e) {
      if (kDebugMode) {
        print('结束音频流时发生错误: $e');
      }
      // 不抛出异常，避免中断整个流程
    }
  }
  
  /// 将音频数据添加到播放列表
  Future<void> _addToPlaylist(Uint8List audioData) async {
    try {
      if (audioData.isEmpty) return;
      
      // 确保播放列表已初始化
      if (!_playlistInitialized) {
        await _initializePlaylist();
      }
      
      // 创建音频源
      final audioSource = BytesAudioSource(audioData);
      
      // 添加到播放列表
      await _playlist.add(audioSource);
      
      // 如果当前没有播放，开始播放
      if (!_isPlaying.value) {
        await _startPlayback();
      } else if (_audioPlayer.processingState == ProcessingState.completed) {
        // 如果播放已完成但状态还没更新，手动前进到下一个
        await _advanceToNextItem();
      }
    } catch (e) {
      // 直接报告错误，不尝试恢复
      _eventController.add({
        'eventType': 'playbackError',
        'error': '添加音频到播放列表失败: $e'
      });
    }
  }
  
  /// 开始播放收集到的音频数据
  Future<void> _startPlayback() async {
    try {
      if (!_playlistInitialized || _playlist.length == 0) {
        return;
      }
      
      // 检查当前播放状态
      final processingState = _audioPlayer.processingState;
      
      // 如果已经播放完成，需要重新设置位置到第一个未播放的项目
      if (processingState == ProcessingState.completed) {
        // 找到第一个未播放的项目
        int nextIndex = 0;
        if (_audioPlayer.currentIndex != null) {
          nextIndex = math.min(_audioPlayer.currentIndex! + 1, _playlist.length - 1);
        }
        
        // 跳转到下一个项目
        await _audioPlayer.seek(Duration.zero, index: nextIndex);
      }
      
      // 开始播放
      await _audioPlayer.play();
    } catch (e) {
      // 直接报告错误，不尝试恢复
      _eventController.add({
        'eventType': 'playbackError',
        'error': '开始播放失败: $e'
      });
    }
  }
  
  /// 处理错误
  void _handleError(dynamic error) {
    _eventController.add({
      'eventType': 'error',
      'error': error.toString()
    });
    
    if (kDebugMode) {
      print('火山语音WebSocket错误: $error');
    }
  }
  
  /// 处理连接关闭
  void _handleDone() {
    _isConnected = false;
    _isSessionActive = false;
    isConnected.value = false;
    isSynthesizing.value = false;
    
    _eventController.add({'eventType': 'disconnected'});
    

  }
  
  /// 解析响应
  Map<String, dynamic>? _parseResponse(Uint8List data) {
    try {
      if (data.length < 4) {
        return null;
      }
      
      // 解析头部
      final header = {
        'protocol_version': (data[0] >> 4) & 0x0F,
        'header_size': data[0] & 0x0F,
        'message_type': (data[1] >> 4) & 0x0F,
        'message_type_specific_flags': data[1] & 0x0F,
        'serialization_method': (data[2] >> 4) & 0x0F,
        'message_compression': data[2] & 0x0F,
        'reserved': data[3],
      };
      
      final result = <String, dynamic>{
        'header': header,
      };
      
      int offset = 4;
      
      // 解析事件
      if (header['message_type_specific_flags'] == _msgTypeFlagWithEvent) {
        if (data.length < offset + 4) {
          return result;
        }
        
        final event = _bytesToInt(data.sublist(offset, offset + 4));
        result['event'] = event;
        offset += 4;
      }
      
      // 根据消息类型和事件类型解析剩余数据
      final messageType = header['message_type'];
      final event = result['event'] as int?;
      
      if (messageType == _fullServerResponse || messageType == _audioOnlyResponse) {
        if (event != null) {
          switch (event) {
            case eventConnectionStarted:
              if (data.length < offset + 4) break;
              
              final connectionIdSize = _bytesToInt(data.sublist(offset, offset + 4));
              offset += 4;
              
              if (data.length < offset + connectionIdSize) break;
              
              final connectionId = String.fromCharCodes(data.sublist(offset, offset + connectionIdSize));
              result['connectionId'] = connectionId;
              offset += connectionIdSize;
              break;
              
            case eventConnectionFailed:
              if (data.length < offset + 4) break;
              
              final metaSize = _bytesToInt(data.sublist(offset, offset + 4));
              offset += 4;
              
              if (data.length < offset + metaSize) break;
              
              final metaJson = String.fromCharCodes(data.sublist(offset, offset + metaSize));
              result['meta'] = metaJson;
              offset += metaSize;
              
              try {
                final meta = jsonDecode(metaJson);
                result['errorDetails'] = meta['error_msg'] ?? 'Unknown error';
              } catch (_) {}
              break;
              
            case eventSessionStarted:
            case eventSessionFailed:
            case eventSessionFinished:
              // 读取会话ID
              if (data.length < offset + 4) break;
              
              final sessionIdSize = _bytesToInt(data.sublist(offset, offset + 4));
              offset += 4;
              
              if (data.length < offset + sessionIdSize) break;
              
              final sessionId = String.fromCharCodes(data.sublist(offset, offset + sessionIdSize));
              result['sessionId'] = sessionId;
              offset += sessionIdSize;
              
              // 读取元数据
              if (data.length < offset + 4) break;
              
              final metaSize = _bytesToInt(data.sublist(offset, offset + 4));
              offset += 4;
              
              if (data.length < offset + metaSize) break;
              
              final metaJson = String.fromCharCodes(data.sublist(offset, offset + metaSize));
              result['meta'] = metaJson;
              offset += metaSize;
              
              try {
                final meta = jsonDecode(metaJson);
                if (meta['error_msg'] != null) {
                  result['errorDetails'] = meta['error_msg'];
                }
              } catch (_) {}
              break;
              
            default:
              // 读取会话ID
              if (data.length < offset + 4) break;
              
              final sessionIdSize = _bytesToInt(data.sublist(offset, offset + 4));
              offset += 4;
              
              if (data.length < offset + sessionIdSize) break;
              
              final sessionId = String.fromCharCodes(data.sublist(offset, offset + sessionIdSize));
              result['sessionId'] = sessionId;
              offset += sessionIdSize;
              
              // 读取序列号
              if (header['message_type_specific_flags'] == _msgTypeFlagNegativeSeq ||
                  header['message_type_specific_flags'] == _msgTypeFlagPositiveSeq) {
                if (data.length < offset + 4) break;
                
                final sequence = _bytesToInt(data.sublist(offset, offset + 4));
                result['sequence'] = sequence;
                offset += 4;
              }
              
              // 读取负载
              if (data.length < offset + 4) break;
              
              final payloadSize = _bytesToInt(data.sublist(offset, offset + 4));
              offset += 4;
              
              if (data.length < offset + payloadSize) break;
              
              final payload = data.sublist(offset, offset + payloadSize);
              result['payload'] = payload;
              
              if (messageType == _fullServerResponse) {
                try {
                  final payloadStr = String.fromCharCodes(payload);
                  result['payloadJson'] = payloadStr;
                } catch (_) {}
              }
              break;
          }
        }
      } else if (messageType == _errorInformation) {
        if (data.length < offset + 4) {
          return result;
        }
        
        final errorCode = _bytesToInt(data.sublist(offset, offset + 4));
        result['errorCode'] = errorCode;
        offset += 4;
        
        // 读取负载
        if (data.length < offset + 4) {
          return result;
        }
        
        final payloadSize = _bytesToInt(data.sublist(offset, offset + 4));
        offset += 4;
        
        if (data.length < offset + payloadSize) {
          return result;
        }
        
        final payload = data.sublist(offset, offset + payloadSize);
        try {
          final payloadStr = String.fromCharCodes(payload);
          result['errorDetails'] = payloadStr;
        } catch (_) {}
      }
      
      return result;
    } catch (e) {
      if (kDebugMode) {
        print('解析响应失败: $e');
      }
      return null;
    }
  }
  
  /// 开始连接
  Future<void> _startConnection() async {
    final header = _createHeader(
      _fullClientRequest,
      _msgTypeFlagWithEvent,
      _jsonSerialization,
      _compressionNo
    );
    
    final optional = _createOptional(eventStartConnection, null, -1);
    final payload = utf8.encode('{}');
    
    await _sendEvent(header, optional, payload);
  }
  
  /// 结束连接
  Future<void> _finishConnection() async {
    final header = _createHeader(
      _fullClientRequest,
      _msgTypeFlagWithEvent,
      _jsonSerialization,
      _compressionNo
    );
    
    final optional = _createOptional(eventFinishConnection, null, -1);
    final payload = utf8.encode('{}');
    
    await _sendEvent(header, optional, payload);
  }
  
  /// 开始TTS会话
  Future<void> _startTtsSession(String speaker) async {
    final header = _createHeader(
      _fullClientRequest,
      _msgTypeFlagWithEvent,
      _jsonSerialization,
      _compressionNo
    );
    
    final optional = _createOptional(eventStartSession, _sessionId, -1);
    
    // 创建会话参数
    final payloadMap = {
      'user': {'uid': '123456'},
      'event': eventStartSession,
      'namespace': 'BidirectionalTTS',
      'req_params': {
        'speaker': speaker,
        'audio_params': {
          'format': 'mp3',
          'sample_rate': 24000
        }
      }
    };
    
    final payload = utf8.encode(jsonEncode(payloadMap));
    
    await _sendEvent(header, optional, payload);
  }
  
  /// 发送TTS消息
  Future<void> _sendTtsMessage(String speaker, String text) async {
    final header = _createHeader(
      _fullClientRequest,
      _msgTypeFlagWithEvent,
      _jsonSerialization,
      _compressionNo
    );
    
    final optional = _createOptional(eventTaskRequest, _sessionId, -1);
    
    // 创建任务参数
    final payloadMap = {
      'user': {'uid': '123456'},
      'event': eventTaskRequest,
      'namespace': 'BidirectionalTTS',
      'req_params': {
        'text': text,
        'speaker': speaker,
        'audio_params': {
          'format': 'mp3',
          'sample_rate': 24000
        }
      }
    };
    
    final payload = utf8.encode(jsonEncode(payloadMap));
    
    await _sendEvent(header, optional, payload);
  }
  
  /// 结束会话
  Future<void> _finishSession() async {
    final header = _createHeader(
      _fullClientRequest,
      _msgTypeFlagWithEvent,
      _jsonSerialization,
      _compressionNo
    );
    
    final optional = _createOptional(eventFinishSession, _sessionId, -1);
    final payload = utf8.encode('{}');
    
    await _sendEvent(header, optional, payload);
  }
  
  /// 创建头部
  Uint8List _createHeader(
    int messageType,
    int messageTypeSpecificFlags,
    int serializationMethod,
    int messageCompression
  ) {
    return Uint8List.fromList([
      // Protocol version | Header size
      ((_protocolVersion << 4) | _defaultHeaderSize) & 0xFF,
      // Message type | Message type specific flags
      ((messageType << 4) | messageTypeSpecificFlags) & 0xFF,
      // Serialization method | Compression method
      ((serializationMethod << 4) | messageCompression) & 0xFF,
      // Reserved
      0
    ]);
  }
  
  /// 创建可选部分
  Uint8List _createOptional(int event, String? sessionId, int sequence) {
    final buffer = BytesBuilder();
    
    // 添加事件
    if (event != eventNone) {
      buffer.add(_intToBytes(event));
    }
    
    // 添加会话ID
    if (sessionId != null) {
      final sessionIdBytes = utf8.encode(sessionId);
      buffer.add(_intToBytes(sessionIdBytes.length));
      buffer.add(sessionIdBytes);
    }
    
    // 添加序列号
    if (sequence >= 0) {
      buffer.add(_intToBytes(sequence));
    }
    
    return buffer.toBytes();
  }
  
  /// 发送事件
  Future<void> _sendEvent(Uint8List header, Uint8List optional, List<int> payload) async {
    if (_channel == null) {
      throw Exception('WebSocket未连接');
    }
    
    final buffer = BytesBuilder();
    
    // 添加头部
    buffer.add(header);
    
    // 添加可选部分
    if (optional.isNotEmpty) {
      buffer.add(optional);
    }
    
    // 添加负载大小
    buffer.add(_intToBytes(payload.length));
    
    // 添加负载
    buffer.add(payload);
    
    // 发送数据
    _channel!.sink.add(buffer.toBytes());
  }
  
  /// 整数转字节数组
  Uint8List _intToBytes(int value) {
    return Uint8List(4)
      ..[0] = (value >> 24) & 0xFF
      ..[1] = (value >> 16) & 0xFF
      ..[2] = (value >> 8) & 0xFF
      ..[3] = value & 0xFF;
  }
  
  /// 字节数组转整数
  int _bytesToInt(Uint8List bytes) {
    if (bytes.length != 4) {
      throw ArgumentError('字节数组长度必须为4');
    }
    
    return ((bytes[0] & 0xFF) << 24) |
           ((bytes[1] & 0xFF) << 16) |
           ((bytes[2] & 0xFF) << 8) |
           (bytes[3] & 0xFF);
  }
  
  /// 释放资源
  @override
  void onClose() async {
    await disconnect();
    _audioDataController.close();
    _eventController.close();
    
    // 释放资源
    _audioPlayer.dispose();
    
    super.onClose();
  }

  /// 合成并播放文本
  Future<bool> speak(String text, {String? speaker}) async {
    if (text.isEmpty) return false;
    
    try {
      // 使用默认发音人
      final actualSpeaker = speaker ?? defaultSpeaker;
      
      // 合成文本
      final success = await synthesize(text, actualSpeaker);
      
      if (!success) {
        if (kDebugMode) {
          print('合成文本失败');
        }
      }
      
      return success;
    } catch (e) {
      _handleError(e);
      return false;
    }
  }
  
  /// 停止播放
  Future<void> stop() async {
    try {
      // 停止音频播放
      await _audioPlayer.stop();
      
      // 清空播放列表
      await _playlist.clear();
      
      // 结束当前会话
      await endSession();
      
      // 清空音频缓冲区
      _audioBuffer.clear();
    } catch (e) {
      _handleError(e);
    }
  }
  
  /// 检查是否正在播放
  bool isActuallyPlaying() {
    return _isPlaying.value;
  }
  
  /// 设置音量
  Future<void> setVolume(double volume) async {
    try {
      await _audioPlayer.setVolume(volume.clamp(0.0, 1.0));
    } catch (e) {
      _handleError(e);
    }
  }
  
  /// 设置播放速度
  Future<void> setSpeed(double speed) async {
    try {
      await _audioPlayer.setSpeed(speed.clamp(0.5, 2.0));
    } catch (e) {
      _handleError(e);
    }
  }
  
  /// 切换启用状态
  void toggleEnabled() {
    // 这个方法在当前实现中不需要特殊处理
  }
  
  /// 单句合成辅助函数
  /// 
  /// 一次性完成连接、会话创建、合成和播放的过程
  /// 适合单句或少量文本的快速合成场景
  /// 
  /// [text] 要合成的文本
  /// [speaker] 发音人，如果为null则使用默认发音人
  /// [autoDisconnect] 合成完成后是否自动断开连接，默认为false
  /// 
  /// 返回合成是否成功
  Future<bool> speakSingle(String text, {String? speaker}) async {
    if (text.isEmpty) return false;
    
    try {
      // 使用默认发音人
      final actualSpeaker = speaker ?? defaultSpeaker;
      
      // 1. 确保连接
      if (!_isConnected) {
        final connected = await connect();
        if (!connected) return false;
      }
      
      // 2. 确保会话已开始
      if (!_isSessionActive) {
        final sessionStarted = await startSession(actualSpeaker);
        if (!sessionStarted) return false;
      }
      
      // 3. 合成文本
      isSynthesizing.value = true;
      final success = await synthesize(text, actualSpeaker);
      
      // 不再自动断开连接，让调用者决定何时结束会话和断开连接
      await endSession();
      
      return success;
    } catch (e) {
      _handleError(e);
      
      return false;
    }
  }
}

/// 使用 BytesAudioSource 进行音频播放
/// 这种方式更简单可靠，适合已经收集完整的音频数据
class BytesAudioSource extends StreamAudioSource {
  final Uint8List _bytes;
  final String _contentType;
  static const int _bufferSize = 4096;  // 4KB buffer size for better Android compatibility
  
  BytesAudioSource(List<int> bytes, {String contentType = 'audio/mpeg'}) 
      : _bytes = bytes is Uint8List ? bytes : Uint8List.fromList(bytes),
        _contentType = contentType;
  
  @override
  Future<StreamAudioResponse> request([int? start, int? end]) async {
    try {
      start = start ?? 0;
      end = end ?? _bytes.length;
      
      // 确保范围有效
      final int validStart = math.min(math.max(0, start), _bytes.length);
      final int validEnd = math.min(math.max(validStart, end), _bytes.length);
      
      // 提取请求的数据范围
      final data = _bytes.sublist(validStart, validEnd);
      
      if (kDebugMode && data.length > 1024) {
        print('BytesAudioSource 请求数据: $validStart-$validEnd (${data.length} 字节)');
      }
      
      // 使用固定大小的块进行流式传输，提高兼容性
      final chunks = <List<int>>[];
      var offset = 0;
      while (offset < data.length) {
        final chunkSize = math.min(_bufferSize, data.length - offset);
        chunks.add(data.sublist(offset, offset + chunkSize));
        offset += chunkSize;
      }
      
      return StreamAudioResponse(
        sourceLength: _bytes.length,
        contentLength: data.length,
        offset: validStart,
        stream: Stream.fromIterable(chunks),
        contentType: _contentType,
      );
    } catch (e) {
      if (kDebugMode) {
        print('BytesAudioSource 请求处理错误: $e');
      }
      // 返回一个空响应而不是抛出异常，提高容错性
      return StreamAudioResponse(
        sourceLength: _bytes.length,
        contentLength: 0,
        offset: 0,
        stream: Stream.value(Uint8List(0)),
        contentType: _contentType,
      );
    }
  }
  
  @override
  Future<int> get length => Future.value(_bytes.length);
}