ai_english/client/lib/features/speaking/services/speech_recognition_service.dart

import 'dart:async';
import 'dart:math';
import '../models/pronunciation_item.dart';

/// 语音识别和评分服务
class SpeechRecognitionService {
  static final SpeechRecognitionService _instance = SpeechRecognitionService._internal();
  factory SpeechRecognitionService() => _instance;
  SpeechRecognitionService._internal();

  bool _isListening = false;
  StreamController<double>? _volumeController;
  StreamController<String>? _recognitionController;

  /// 获取音量流
  Stream<double> get volumeStream => _volumeController?.stream ?? const Stream.empty();

  /// 获取识别结果流
  Stream<String> get recognitionStream => _recognitionController?.stream ?? const Stream.empty();

  /// 是否正在监听
  bool get isListening => _isListening;

  /// 开始语音识别
  Future<bool> startListening() async {
    if (_isListening) return false;

    try {
      _isListening = true;
      _volumeController = StreamController<double>.broadcast();
      _recognitionController = StreamController<String>.broadcast();

      // TODO: 实现真实的语音识别
      // 这里应该调用语音识别API，如Google Speech-to-Text、百度语音识别等
      
      // 模拟音量变化
      _simulateVolumeChanges();
      
      return true;
    } catch (e) {
      _isListening = false;
      return false;
    }
  }

  /// 停止语音识别
  Future<void> stopListening() async {
    if (!_isListening) return;

    _isListening = false;
    await _volumeController?.close();
    await _recognitionController?.close();
    _volumeController = null;
    _recognitionController = null;
  }

  /// 分析发音并评分
  Future<PronunciationResult> analyzePronunciation(
    String recordedText,
    PronunciationItem targetItem,
  ) async {
    // TODO: 实现真实的发音分析
    // 这里应该调用发音评估API，如科大讯飞语音评测、腾讯云语音评测等
    
    // 模拟分析过程
    await Future.delayed(const Duration(milliseconds: 1500));
    
    return _simulateAnalysis(recordedText, targetItem);
  }

  /// 模拟音量变化
  void _simulateVolumeChanges() {
    Timer.periodic(const Duration(milliseconds: 100), (timer) {
      if (!_isListening) {
        timer.cancel();
        return;
      }
      
      // 生成随机音量值
      final volume = Random().nextDouble() * 0.8 + 0.1;
      _volumeController?.add(volume);
    });
  }

  /// 模拟发音分析
  PronunciationResult _simulateAnalysis(String recordedText, PronunciationItem targetItem) {
    final random = Random();
    
    // 基础分数
    double baseScore = 60.0 + random.nextDouble() * 30;
    
    // 根据文本相似度调整分数
    final similarity = _calculateSimilarity(recordedText.toLowerCase(), targetItem.text.toLowerCase());
    final adjustedScore = baseScore + (similarity * 20);
    
    // 确保分数在合理范围内
    final finalScore = adjustedScore.clamp(0.0, 100.0);
    
    return PronunciationResult(
      score: finalScore,
      accuracy: _getAccuracyLevel(finalScore),
      feedback: _generateFeedback(finalScore, targetItem),
      detailedAnalysis: _generateDetailedAnalysis(finalScore, targetItem),
      suggestions: _generateSuggestions(finalScore, targetItem),
      recognizedText: recordedText,
    );
  }

  /// 计算文本相似度
  double _calculateSimilarity(String text1, String text2) {
    if (text1 == text2) return 1.0;
    
    final words1 = text1.split(' ');
    final words2 = text2.split(' ');
    
    int matches = 0;
    final maxLength = max(words1.length, words2.length);
    
    for (int i = 0; i < min(words1.length, words2.length); i++) {
      if (words1[i] == words2[i]) {
        matches++;
      }
    }
    
    return matches / maxLength;
  }

  /// 获取准确度等级
  AccuracyLevel _getAccuracyLevel(double score) {
    if (score >= 90) return AccuracyLevel.excellent;
    if (score >= 80) return AccuracyLevel.good;
    if (score >= 70) return AccuracyLevel.fair;
    if (score >= 60) return AccuracyLevel.needsImprovement;
    return AccuracyLevel.poor;
  }

  /// 生成反馈
  String _generateFeedback(double score, PronunciationItem item) {
    if (score >= 90) {
      return '发音非常标准！语调和节奏都很自然。';
    } else if (score >= 80) {
      return '发音很好，只需要在个别音素上稍作调整。';
    } else if (score >= 70) {
      return '发音基本正确，建议多练习重音和语调。';
    } else if (score >= 60) {
      return '发音需要改进，请注意音素的准确性。';
    } else {
      return '发音需要大幅改进，建议从基础音素开始练习。';
    }
  }

  /// 生成详细分析
  Map<String, double> _generateDetailedAnalysis(double score, PronunciationItem item) {
    final random = Random();
    final baseVariation = (score - 70) / 30; // 基于总分的变化
    
    return {
      '音素准确度': (70 + baseVariation * 20 + random.nextDouble() * 10).clamp(0, 100),
      '语调自然度': (65 + baseVariation * 25 + random.nextDouble() * 15).clamp(0, 100),
      '语速适中度': (75 + baseVariation * 15 + random.nextDouble() * 10).clamp(0, 100),
      '重音正确度': (70 + baseVariation * 20 + random.nextDouble() * 10).clamp(0, 100),
      '流畅度': (60 + baseVariation * 30 + random.nextDouble() * 15).clamp(0, 100),
    };
  }

  /// 生成改进建议
  List<String> _generateSuggestions(double score, PronunciationItem item) {
    List<String> suggestions = [];
    
    if (score < 80) {
      suggestions.addAll([
        '多听标准发音，模仿语调变化',
        '注意重音位置，突出重读音节',
      ]);
    }
    
    if (score < 70) {
      suggestions.addAll([
        '放慢语速，确保每个音素清晰',
        '练习困难音素的发音方法',
      ]);
    }
    
    if (score < 60) {
      suggestions.addAll([
        '从基础音标开始系统学习',
        '使用镜子观察口型变化',
      ]);
    }
    
    // 根据练习类型添加特定建议
    switch (item.type) {
      case PronunciationType.word:
        suggestions.add('分解单词，逐个音节练习');
        break;
      case PronunciationType.sentence:
        suggestions.add('注意句子的语调起伏和停顿');
        break;
      case PronunciationType.phrase:
        suggestions.add('练习短语内部的连读现象');
        break;
      case PronunciationType.phoneme:
        suggestions.add('重点练习该音素的舌位和口型');
        break;
    }
    
    return suggestions;
  }

  /// 获取发音提示
  List<String> getPronunciationTips(PronunciationItem item) {
    return item.tips;
  }

  /// 播放标准发音
  Future<void> playStandardAudio(String audioUrl) async {
    // TODO: 实现音频播放功能
    // 这里应该使用音频播放插件，如audioplayers
    
    // 模拟播放时间
    await Future.delayed(const Duration(seconds: 2));
  }

  /// 检查麦克风权限
  Future<bool> checkMicrophonePermission() async {
    // TODO: 实现权限检查
    // 这里应该使用权限插件，如permission_handler
    
    // 模拟权限检查
    return true;
  }

  /// 请求麦克风权限
  Future<bool> requestMicrophonePermission() async {
    // TODO: 实现权限请求
    // 这里应该使用权限插件，如permission_handler
    
    // 模拟权限请求
    return true;
  }
}

/// 发音分析结果
class PronunciationResult {
  final double score;
  final AccuracyLevel accuracy;
  final String feedback;
  final Map<String, double> detailedAnalysis;
  final List<String> suggestions;
  final String recognizedText;

  PronunciationResult({
    required this.score,
    required this.accuracy,
    required this.feedback,
    required this.detailedAnalysis,
    required this.suggestions,
    required this.recognizedText,
  });
}

/// 准确度等级
enum AccuracyLevel {
  excellent,
  good,
  fair,
  needsImprovement,
  poor,
}

extension AccuracyLevelExtension on AccuracyLevel {
  String get displayName {
    switch (this) {
      case AccuracyLevel.excellent:
        return '优秀';
      case AccuracyLevel.good:
        return '良好';
      case AccuracyLevel.fair:
        return '一般';
      case AccuracyLevel.needsImprovement:
        return '需要改进';
      case AccuracyLevel.poor:
        return '较差';
    }
  }

  String get description {
    switch (this) {
      case AccuracyLevel.excellent:
        return '发音非常标准，语调自然';
      case AccuracyLevel.good:
        return '发音准确，略有改进空间';
      case AccuracyLevel.fair:
        return '发音基本正确，需要练习';
      case AccuracyLevel.needsImprovement:
        return '发音有明显问题，需要改进';
      case AccuracyLevel.poor:
        return '发音问题较多，需要系统练习';
    }
  }

  String get emoji {
    switch (this) {
      case AccuracyLevel.excellent:
        return '🌟';
      case AccuracyLevel.good:
        return '👍';
      case AccuracyLevel.fair:
        return '👌';
      case AccuracyLevel.needsImprovement:
        return '📈';
      case AccuracyLevel.poor:
        return '💪';
    }
  }
}