import 'dart:async';
import 'package:flutter/services.dart';
import 'package:flutter_dotenv/flutter_dotenv.dart';

/// 微软语音识别服务
/// 
/// 该服务提供了通过平台通道与 Android 上的 Microsoft Speech SDK 交互的接口
class VoiceRecognitionService {
  static const MethodChannel _channel = MethodChannel('com.example.deep_voice/speech_recognition');
  static const EventChannel _eventChannel = EventChannel('com.example.deep_voice/speech_recognition_events');
  
  bool _isInitialized = false;
  late final String _subscriptionKey;
  late final String _serviceRegion;
  
  // 连续识别相关
  bool _isContinuousRecognitionActive = false;
  StreamController<RecognitionEvent>? _eventStreamController;
  StreamSubscription? _eventSubscription;
  
  // 公开的事件流
  Stream<RecognitionEvent>? _recognitionStream;
  Stream<RecognitionEvent>? get recognitionStream => _recognitionStream;
  
  // 最新的识别结果
  String _latestRecognizedText = '';
  String get latestRecognizedText => _latestRecognizedText;
  
  VoiceRecognitionService() {
    _loadConfig();
  }
  
  /// 从环境变量加载配置
  void _loadConfig() {
    _subscriptionKey = dotenv.env['AZURE_SPEECH_KEY'] ?? '';
    _serviceRegion = dotenv.env['AZURE_SPEECH_REGION'] ?? '';
    
    if (_subscriptionKey.isEmpty || _serviceRegion.isEmpty) {
      throw Exception('未找到 Azure 语音服务配置。请在 .env 文件中设置 AZURE_SPEECH_KEY 和 AZURE_SPEECH_REGION');
    }
  }
  
  /// 初始化微软语音识别 SDK
  /// 
  /// 返回 true 表示初始化成功，否则抛出 PlatformException
  Future<bool> initialize() async {
    if (_isInitialized) return true;
    
    try {
      final bool result = await _channel.invokeMethod('initialize', {
        'subscriptionKey': _subscriptionKey,
        'serviceRegion': _serviceRegion,
      });
      _isInitialized = result;
      return result;
    } on PlatformException catch (e) {
      print('语音识别初始化失败: ${e.message}');
      _isInitialized = false;
      throw e;
    }
  }
  
  /// 执行一次性语音识别
  /// 
  /// 返回识别的文本，如果识别失败则抛出 PlatformException
  Future<String> recognizeSpeech() async {
    if (!_isInitialized) {
      throw Exception('语音识别服务未初始化，请先调用 initialize()');
    }
    
    try {
      final String result = await _channel.invokeMethod('recognizeOnce');
      return result;
    } on PlatformException catch (e) {
      print('语音识别失败: ${e.message}');
      throw e;
    }
  }
  
  /// 开始连续语音识别
  /// 
  /// 返回一个包含识别事件的流，如果开始失败则抛出 PlatformException
  Future<Stream<RecognitionEvent>> startContinuousRecognition() async {
    if (!_isInitialized) {
      throw Exception('语音识别服务未初始化，请先调用 initialize()');
    }
    
    if (_isContinuousRecognitionActive) {
      throw Exception('连续语音识别已经在进行中');
    }
    
    try {
      // 创建事件流控制器
      _eventStreamController = StreamController<RecognitionEvent>.broadcast();
      
      // 设置事件监听
      _eventSubscription = _eventChannel
          .receiveBroadcastStream()
          .listen(_handleRecognitionEvent, onError: _handleRecognitionError);
      
      // 开始连续识别
      final bool result = await _channel.invokeMethod('startContinuousRecognition');
      _isContinuousRecognitionActive = result;
      
      // 设置公开的流
      _recognitionStream = _eventStreamController!.stream;
      
      return _recognitionStream!;
    } on PlatformException catch (e) {
      print('开始连续语音识别失败: ${e.message}');
      _cleanupEventStream();
      throw e;
    }
  }
  
  /// 停止连续语音识别
  /// 
  /// 返回 true 表示停止成功，否则抛出 PlatformException
  Future<bool> stopContinuousRecognition() async {
    if (!_isInitialized) {
      throw Exception('语音识别服务未初始化，请先调用 initialize()');
    }
    
    if (!_isContinuousRecognitionActive) {
      return true; // 已经停止，直接返回成功
    }
    
    try {
      final bool result = await _channel.invokeMethod('stopContinuousRecognition');
      _isContinuousRecognitionActive = !result;
      
      // 清理事件流
      _cleanupEventStream();
      
      return result;
    } on PlatformException catch (e) {
      print('停止连续语音识别失败: ${e.message}');
      throw e;
    }
  }
  
  /// 检查连续识别是否活跃
  bool isContinuousRecognitionActive() {
    return _isContinuousRecognitionActive;
  }
  
  /// 处理来自原生端的识别事件
  void _handleRecognitionEvent(dynamic event) {
    if (event is! Map) return;
    
    final Map<dynamic, dynamic> eventMap = event;
    final String eventType = eventMap['eventType'] as String? ?? '';
    
    switch (eventType) {
      case 'finalResult':
        final String text = eventMap['text'] as String? ?? '';
        _latestRecognizedText = text;
        _eventStreamController?.add(RecognitionEvent(
          type: RecognitionEventType.finalResult,
          text: text,
        ));
        break;
        
      case 'intermediateResult':
        final String text = eventMap['text'] as String? ?? '';
        _eventStreamController?.add(RecognitionEvent(
          type: RecognitionEventType.intermediateResult,
          text: text,
        ));
        break;
        
      case 'sessionStarted':
        _eventStreamController?.add(RecognitionEvent(
          type: RecognitionEventType.sessionStarted,
        ));
        break;
        
      case 'sessionStopped':
        _isContinuousRecognitionActive = false;
        _eventStreamController?.add(RecognitionEvent(
          type: RecognitionEventType.sessionStopped,
        ));
        break;
        
      case 'canceled':
        _isContinuousRecognitionActive = false;
        final String reason = eventMap['reason'] as String? ?? '';
        final String errorDetails = eventMap['errorDetails'] as String? ?? '';
        _eventStreamController?.add(RecognitionEvent(
          type: RecognitionEventType.canceled,
          error: '$reason: $errorDetails',
        ));
        break;
        
      case 'error':
        final String error = eventMap['error'] as String? ?? '';
        _eventStreamController?.add(RecognitionEvent(
          type: RecognitionEventType.error,
          error: error,
        ));
        break;
    }
  }
  
  /// 处理识别事件流错误
  void _handleRecognitionError(Object error) {
    _eventStreamController?.addError(error);
    _cleanupEventStream();
  }
  
  /// 清理事件流资源
  void _cleanupEventStream() {
    _eventSubscription?.cancel();
    _eventSubscription = null;
    
    _eventStreamController?.close();
    _eventStreamController = null;
    
    _recognitionStream = null;
    _isContinuousRecognitionActive = false;
  }
  
  /// 释放资源
  Future<void> dispose() async {
    try {
      if (_isContinuousRecognitionActive) {
        await stopContinuousRecognition();
      }
      
      await _channel.invokeMethod('dispose');
      _cleanupEventStream();
      _isInitialized = false;
    } catch (e) {
      print('释放语音识别资源失败: $e');
    }
  }
}

/// 识别事件类型
enum RecognitionEventType {
  /// 最终识别结果
  finalResult,
  
  /// 中间识别结果（实时反馈）
  intermediateResult,
  
  /// 会话开始
  sessionStarted,
  
  /// 会话结束
  sessionStopped,
  
  /// 识别取消
  canceled,
  
  /// 识别错误
  error,
}

/// 识别事件
class RecognitionEvent {
  /// 事件类型
  final RecognitionEventType type;
  
  /// 识别文本（仅在 finalResult 和 intermediateResult 类型中有效）
  final String text;
  
  /// 错误信息（仅在 error 和 canceled 类型中有效）
  final String error;
  
  RecognitionEvent({
    required this.type,
    this.text = '',
    this.error = '',
  });
  
  @override
  String toString() {
    return 'RecognitionEvent{type: $type, text: $text, error: $error}';
  }
}