import 'dart:async';
import 'dart:typed_data';
import 'package:get/get.dart';
import 'package:just_audio/just_audio.dart';
import 'package:flutter_azure_tts/flutter_azure_tts.dart';
import 'package:audio_session/audio_session.dart';
import 'package:flutter_dotenv/flutter_dotenv.dart';

/// A custom AudioSource that reads audio data from a byte array
class BytesAudioSource extends StreamAudioSource {
  final Uint8List _bytes;
  static const int _recommendedBufferSize = 8192;  // 使用推荐的缓冲区大小

  BytesAudioSource(this._bytes);

  @override
  Future<StreamAudioResponse> request([int? start, int? end]) async {
    start = start ?? 0;
    end = end ?? _bytes.length;

    try {
      // 确保缓冲区大小至少为推荐值
      final bufferSize = (end - start) < _recommendedBufferSize 
          ? _recommendedBufferSize 
          : end - start;

      final subData = _bytes.sublist(start, end);
      
      return StreamAudioResponse(
        sourceLength: _bytes.length,
        contentLength: subData.length,
        offset: start,
        stream: Stream.value(subData),
        contentType: 'audio/mpeg',
      );
    } catch (e) {
      print('BytesAudioSource request error: $e');
      rethrow;
    }
  }

  @override
  Future<int> get length => Future.value(_bytes.length);
}

/// Azure TTS Service，支持将文本转换为语音并以流式方式边下载边播放
class AzureTtsService extends GetxService {
  static bool _isInitialized = false;
  final _audioPlayer = AudioPlayer();
  final ConcatenatingAudioSource _playlist = ConcatenatingAudioSource(children: []);
  final isEnabled = false.obs;
  final isPlaying = false.obs;
  StreamSubscription? _playbackEventSubscription;
  StreamSubscription? _playerStateSubscription;
  AudioSession? _audioSession;

  // Azure 配置
  final String _azureKey;
  final String _azureRegion;

  // 句子管理
  String _pendingText = '';
  final List<String> _sentenceQueue = [];
  static final _sentenceBreaks = RegExp(r'[。！？.!?]');

  // 状态
  bool _isFetching = false;
  late Voice _selectedVoice;
  bool _isDisposed = false;

  AzureTtsService() : 
    _azureKey = dotenv.env['AZURE_TTS_KEY'] ?? '',
    _azureRegion = dotenv.env['AZURE_TTS_REGION'] ?? '' {
    if (_azureKey.isEmpty || _azureRegion.isEmpty) {
      throw Exception('Azure TTS配置信息不完整，请检查环境变量');
    }
  }

  @override
  Future<void> onInit() async {
    super.onInit();
    try {
      // 初始化音频会话
      _audioSession = await AudioSession.instance;
      await _audioSession?.configure(AudioSessionConfiguration(
        avAudioSessionCategory: AVAudioSessionCategory.playback,
        androidAudioAttributes: const AndroidAudioAttributes(
          contentType: AndroidAudioContentType.speech,
          usage: AndroidAudioUsage.media,
          flags: AndroidAudioFlags.audibilityEnforced,
        ),
        androidAudioFocusGainType: AndroidAudioFocusGainType.gain,
      ));

      // 设置音频播放器
      if (!_isDisposed) {
        await _audioPlayer.setVolume(1.0);
        await _audioPlayer.setLoopMode(LoopMode.off);
        await _audioPlayer.setAudioSource(
          _playlist,
          initialPosition: Duration.zero,
          preload: false,
        );
        
        _playbackEventSubscription = _audioPlayer.playbackEventStream.listen(
          (event) {
            if (_isDisposed) return;
            print('播放事件: $event');
            if (event.processingState == ProcessingState.completed) {
              _tryPlayNext();
            }
          },
          onError: (error) {
            if (_isDisposed) return;
            print('播放错误: $error');
            _handlePlaybackError(error);
          },
        );

        _playerStateSubscription = _audioPlayer.playerStateStream.listen((state) {
          if (_isDisposed) return;
          print('播放器状态变化: playing=${state.playing},processingState=${state.processingState}');
          isPlaying.value = state.playing;
          
          if (state.processingState == ProcessingState.completed) {
            _tryPlayNext();
          }
        });
      }

      // 初始化 Azure TTS (只初始化一次)
      if (!_isInitialized && !_isDisposed) {
        FlutterAzureTts.init(
          subscriptionKey: _azureKey,
          region: _azureRegion,
          withLogs: true,
        );
        _isInitialized = true;
      }

      // 获取可用语音列表并设置默认语音
      if (!_isDisposed) {
        final voicesResponse = await FlutterAzureTts.getAvailableVoices();
        _selectedVoice = voicesResponse.voices.firstWhere(
          (v) => v.shortName == 'zh-CN-YunxiNeural',
          orElse: () => voicesResponse.voices.first,
        );
        print('已选择语音: ${_selectedVoice.shortName}');
      }
    } catch (e, stackTrace) {
      print('初始化TTS服务失败: $e');
      print('Stack trace: $stackTrace');
    }
  }

  Future<void> _cleanupResources() async {
    _isDisposed = true;
    await _playbackEventSubscription?.cancel();
    await _playerStateSubscription?.cancel();
    await _audioSession?.setActive(false);
    await stop();
    await _audioPlayer.dispose();
  }

  @override
  void onClose() async {
    print('关闭TTS服务');
    await _cleanupResources();
    super.onClose();
  }

  void _handlePlaybackError(dynamic error) {
    print('处理播放错误: $error');
    // 尝试重新初始化播放器
    _reinitializePlayer();
  }

  Future<void> _reinitializePlayer() async {
    try {
      await _audioPlayer.stop();
      await _playlist.clear();
      await _audioPlayer.setAudioSource(_playlist);
      print('播放器重新初始化成功');
    } catch (e) {
      print('播放器重新初始化失败: $e');
    }
  }

  void _tryPlayNext() async {
    if (_playlist.length > 0 && !_audioPlayer.playing) {
      try {
        await _audioPlayer.seek(Duration.zero, index: 0);
        await _audioPlayer.play();
      } catch (e) {
        print('尝试播放下一段失败: $e');
      }
    }
  }

  Future<void> speak(String text) async {
    if (!isEnabled.value) {
      print('TTS 未启用，跳过播放。');
      return;
    }

    try {
      print('准备播放文本: $text');
      _pendingText += text;
      _extractFullSentences();
      await _startPreloadIfNeeded();

      if (!_audioPlayer.playing && _playlist.length > 0) {
        print('开始播放音频');
        await _audioPlayer.play();
      }
    } catch (e) {
      print('播放文本失败: $e');
    }
  }

  void _extractFullSentences() {
    if (_pendingText.isEmpty) return;

    final matches = _sentenceBreaks.allMatches(_pendingText).toList();
    if (matches.isEmpty) return;

    int lastPos = 0;
    for (final match in matches) {
      final end = match.end;
      final sentence = _pendingText.substring(lastPos, end).trim();
      if (sentence.isNotEmpty) {
        _sentenceQueue.add(sentence);
      }
      lastPos = end;
    }

    if (lastPos > 0) {
      _pendingText = _pendingText.substring(lastPos);
    }
  }

  Future<void> _startPreloadIfNeeded() async {
    if (_isFetching) return;
    if (_sentenceQueue.isEmpty) return;

    _isFetching = true;
    await _fetchNextSegment();
  }

  Future<void> _fetchNextSegment() async {
    if (_sentenceQueue.isEmpty) {
      _isFetching = false;
      return;
    }

    final sentence = _sentenceQueue.removeAt(0);
    print('获取音频片段: $sentence');

    try {
      final params = TtsParams(
        voice: _selectedVoice,
        audioFormat: AudioOutputFormat.audio16khz32kBitrateMonoMp3,
        rate: 1.0,
        text: sentence,
      );

      final ttsResponse = await FlutterAzureTts.getTts(params);
      if (ttsResponse.audio != null && ttsResponse.audio.isNotEmpty) {
        print('成功获取音频数据: ${ttsResponse.audio.length} bytes');
        
        try {
          final audioSource = BytesAudioSource(ttsResponse.audio);
          await _playlist.add(audioSource);
          print('音频片段已添加到播放列表');
          
          if (!_audioPlayer.playing && _playlist.length == 1) {
            await _audioPlayer.setVolume(1.0);
            await _audioPlayer.seek(Duration.zero, index: 0);
            await Future.delayed(const Duration(milliseconds: 100));
            await _audioPlayer.play();
          }
        } catch (e) {
          print('添加音频源失败: $e');
        }
      } else {
        print('获取音频数据失败: 返回为空或长度为0');
      }
    } catch (e, stackTrace) {
      print('获取音频失败: $e');
      print('Stack trace: $stackTrace');
    }

    await _fetchNextSegment();
  }

  Future<void> stop() async {
    try {
      print('停止播放');
      await _audioPlayer.stop();
      await _playlist.clear();
      _pendingText = '';
      _sentenceQueue.clear();
      _isFetching = false;
      isPlaying.value = false;
    } catch (e) {
      print('停止播放失败: $e');
    }
  }

  void toggleEnabled() {
    isEnabled.toggle();
    if (!isEnabled.value) {
      stop();
    }
  }
}