// 自然写互动课堂平板端应用软件 V1.0
// repository/local_repository.dart - SQLite + Hive本地数据存储

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

/// 数据库表名常量
class PadDbTables {
  static const String homework = 'pad_homework';
  static const String homeworkQuestion = 'pad_homework_question';
  static const String answerProgress = 'pad_answer_progress';
  static const String errorBook = 'pad_error_book';
  static const String studyPlan = 'pad_study_plan';
  static const String studyTask = 'pad_study_task';
  static const String practiceRecord = 'pad_practice_record';
  static const String strokeCache = 'pad_stroke_cache';
  static const String offlineAction = 'pad_offline_action';
  static const String usageRecord = 'pad_usage_record';
}

/// 数据库版本
const int padDbVersion = 4;

/// 作业缓存模型
class CachedHomework {
  final String id;
  final String title;
  final String subject;
  final String teacherName;
  final String status;
  final String? deadline;
  final String? content;
  final int totalQuestions;
  final int answeredQuestions;
  final DateTime cachedAt;

  CachedHomework({
    required this.id,
    required this.title,
    required this.subject,
    required this.teacherName,
    required this.status,
    this.deadline,
    this.content,
    this.totalQuestions = 0,
    this.answeredQuestions = 0,
    required this.cachedAt,
  });

  Map<String, dynamic> toMap() => {
    'id': id,
    'title': title,
    'subject': subject,
    'teacher_name': teacherName,
    'status': status,
    'deadline': deadline,
    'content': content,
    'total_questions': totalQuestions,
    'answered_questions': answeredQuestions,
    'cached_at': cachedAt.toIso8601String(),
  };

  factory CachedHomework.fromMap(Map<String, dynamic> map) {
    return CachedHomework(
      id: map['id'],
      title: map['title'] ?? '',
      subject: map['subject'] ?? '',
      teacherName: map['teacher_name'] ?? '',
      status: map['status'] ?? 'pending',
      deadline: map['deadline'],
      content: map['content'],
      totalQuestions: map['total_questions'] ?? 0,
      answeredQuestions: map['answered_questions'] ?? 0,
      cachedAt: DateTime.parse(map['cached_at']),
    );
  }
}

/// 错题记录模型
class ErrorBookEntry {
  final String id;
  final String homeworkId;
  final String questionId;
  final String subject;
  final String? knowledgePoint;
  final String questionContent;
  final String? questionImageUrl;
  final String? studentAnswer;
  final String? correctAnswer;
  final String? errorReason;
  final int reviewCount;
  final DateTime createdAt;
  final DateTime? lastReviewAt;

  ErrorBookEntry({
    required this.id,
    required this.homeworkId,
    required this.questionId,
    required this.subject,
    this.knowledgePoint,
    required this.questionContent,
    this.questionImageUrl,
    this.studentAnswer,
    this.correctAnswer,
    this.errorReason,
    this.reviewCount = 0,
    required this.createdAt,
    this.lastReviewAt,
  });

  Map<String, dynamic> toMap() => {
    'id': id,
    'homework_id': homeworkId,
    'question_id': questionId,
    'subject': subject,
    'knowledge_point': knowledgePoint,
    'question_content': questionContent,
    'question_image_url': questionImageUrl,
    'student_answer': studentAnswer,
    'correct_answer': correctAnswer,
    'error_reason': errorReason,
    'review_count': reviewCount,
    'created_at': createdAt.toIso8601String(),
    'last_review_at': lastReviewAt?.toIso8601String(),
  };

  factory ErrorBookEntry.fromMap(Map<String, dynamic> map) {
    return ErrorBookEntry(
      id: map['id'],
      homeworkId: map['homework_id'] ?? '',
      questionId: map['question_id'] ?? '',
      subject: map['subject'] ?? '',
      knowledgePoint: map['knowledge_point'],
      questionContent: map['question_content'] ?? '',
      questionImageUrl: map['question_image_url'],
      studentAnswer: map['student_answer'],
      correctAnswer: map['correct_answer'],
      errorReason: map['error_reason'],
      reviewCount: map['review_count'] ?? 0,
      createdAt: DateTime.parse(map['created_at']),
      lastReviewAt: map['last_review_at'] != null
          ? DateTime.parse(map['last_review_at'])
          : null,
    );
  }
}

/// 学习计划模型
class StudyPlanEntry {
  final String id;
  final String title;
  final String type;
  final String? subject;
  final DateTime startDate;
  final DateTime endDate;
  final double progress;
  final int totalTasks;
  final int completedTasks;
  final bool isActive;

  StudyPlanEntry({
    required this.id,
    required this.title,
    required this.type,
    this.subject,
    required this.startDate,
    required this.endDate,
    this.progress = 0.0,
    this.totalTasks = 0,
    this.completedTasks = 0,
    this.isActive = true,
  });

  Map<String, dynamic> toMap() => {
    'id': id,
    'title': title,
    'type': type,
    'subject': subject,
    'start_date': startDate.toIso8601String(),
    'end_date': endDate.toIso8601String(),
    'progress': progress,
    'total_tasks': totalTasks,
    'completed_tasks': completedTasks,
    'is_active': isActive ? 1 : 0,
  };
}

/// 练字练习记录模型
class PracticeRecord {
  final String id;
  final String templateId;
  final String character;
  final int strokeScore;
  final int structureScore;
  final int overallScore;
  final String? strokeDataJson;
  final DateTime practiceAt;

  PracticeRecord({
    required this.id,
    required this.templateId,
    required this.character,
    this.strokeScore = 0,
    this.structureScore = 0,
    this.overallScore = 0,
    this.strokeDataJson,
    required this.practiceAt,
  });

  Map<String, dynamic> toMap() => {
    'id': id,
    'template_id': templateId,
    'character': character,
    'stroke_score': strokeScore,
    'structure_score': structureScore,
    'overall_score': overallScore,
    'stroke_data_json': strokeDataJson,
    'practice_at': practiceAt.toIso8601String(),
  };
}

/// 平板端本地数据存储仓库
/// 使用SQLite持久化存储 + Hive内存级KV缓存
/// 支持：作业缓存、错题本、学习计划、练字记录、离线操作队列、使用时长记录
class PadLocalRepository {
  /// 数据库实例（实际使用sqflite库）
  // late final Database _db;

  /// 单例
  static PadLocalRepository? _instance;
  static PadLocalRepository get instance {
    _instance ??= PadLocalRepository._internal();
    return _instance!;
  }

  PadLocalRepository._internal();

  /// 初始化数据库，创建表结构并执行版本迁移
  Future<void> initialize() async {
    // 实际调用: openDatabase(path, version: padDbVersion, ...)
    // 以下为建表SQL

    // V1: 基础表
    await _createTablesV1();

    // V2: 增加学习计划表
    await _createTablesV2();

    // V3: 增加使用时长记录表
    await _createTablesV3();

    // V4: 增加练字记录表和索引优化
    await _createTablesV4();
  }

  /// V1建表：作业缓存、作答进度、错题本、离线操作队列
  Future<void> _createTablesV1() async {
    // 作业缓存表
    const createHomework = '''
      CREATE TABLE IF NOT EXISTS ${PadDbTables.homework} (
        id TEXT PRIMARY KEY,
        title TEXT NOT NULL,
        subject TEXT NOT NULL,
        teacher_name TEXT,
        status TEXT DEFAULT 'pending',
        deadline TEXT,
        content TEXT,
        total_questions INTEGER DEFAULT 0,
        answered_questions INTEGER DEFAULT 0,
        cached_at TEXT NOT NULL
      )
    ''';

    // 作业题目缓存表
    const createQuestion = '''
      CREATE TABLE IF NOT EXISTS ${PadDbTables.homeworkQuestion} (
        id TEXT PRIMARY KEY,
        homework_id TEXT NOT NULL,
        question_index INTEGER,
        type TEXT DEFAULT 'write',
        content TEXT,
        image_url TEXT,
        options TEXT,
        correct_answer TEXT,
        FOREIGN KEY (homework_id) REFERENCES ${PadDbTables.homework}(id)
      )
    ''';

    // 作答进度暂存表
    const createProgress = '''
      CREATE TABLE IF NOT EXISTS ${PadDbTables.answerProgress} (
        id INTEGER PRIMARY KEY AUTOINCREMENT,
        homework_id TEXT NOT NULL,
        question_id TEXT NOT NULL,
        text_answer TEXT,
        stroke_data TEXT,
        saved_at TEXT NOT NULL,
        UNIQUE(homework_id, question_id)
      )
    ''';

    // 错题本表
    const createErrorBook = '''
      CREATE TABLE IF NOT EXISTS ${PadDbTables.errorBook} (
        id TEXT PRIMARY KEY,
        homework_id TEXT,
        question_id TEXT,
        subject TEXT NOT NULL,
        knowledge_point TEXT,
        question_content TEXT NOT NULL,
        question_image_url TEXT,
        student_answer TEXT,
        correct_answer TEXT,
        error_reason TEXT,
        review_count INTEGER DEFAULT 0,
        created_at TEXT NOT NULL,
        last_review_at TEXT
      )
    ''';

    // 离线操作队列表
    const createOffline = '''
      CREATE TABLE IF NOT EXISTS ${PadDbTables.offlineAction} (
        id INTEGER PRIMARY KEY AUTOINCREMENT,
        action_type TEXT NOT NULL,
        payload TEXT NOT NULL,
        retry_count INTEGER DEFAULT 0,
        created_at TEXT NOT NULL,
        status TEXT DEFAULT 'pending'
      )
    ''';

    // 笔迹暂存表
    const createStroke = '''
      CREATE TABLE IF NOT EXISTS ${PadDbTables.strokeCache} (
        id INTEGER PRIMARY KEY AUTOINCREMENT,
        homework_id TEXT,
        question_id TEXT,
        page_id TEXT,
        stroke_json TEXT NOT NULL,
        pen_mac TEXT,
        created_at TEXT NOT NULL
      )
    ''';

    // 实际执行建表SQL
    // await _db.execute(createHomework);
    // await _db.execute(createQuestion);
    // await _db.execute(createProgress);
    // await _db.execute(createErrorBook);
    // await _db.execute(createOffline);
    // await _db.execute(createStroke);
  }

  /// V2建表：学习计划与任务
  Future<void> _createTablesV2() async {
    const createPlan = '''
      CREATE TABLE IF NOT EXISTS ${PadDbTables.studyPlan} (
        id TEXT PRIMARY KEY,
        title TEXT NOT NULL,
        type TEXT NOT NULL,
        subject TEXT,
        start_date TEXT NOT NULL,
        end_date TEXT NOT NULL,
        progress REAL DEFAULT 0.0,
        total_tasks INTEGER DEFAULT 0,
        completed_tasks INTEGER DEFAULT 0,
        is_active INTEGER DEFAULT 1
      )
    ''';

    const createTask = '''
      CREATE TABLE IF NOT EXISTS ${PadDbTables.studyTask} (
        id TEXT PRIMARY KEY,
        plan_id TEXT NOT NULL,
        title TEXT NOT NULL,
        description TEXT,
        target_date TEXT,
        is_completed INTEGER DEFAULT 0,
        completed_at TEXT,
        FOREIGN KEY (plan_id) REFERENCES ${PadDbTables.studyPlan}(id)
      )
    ''';

    // await _db.execute(createPlan);
    // await _db.execute(createTask);
  }

  /// V3建表：使用时长记录
  Future<void> _createTablesV3() async {
    const createUsage = '''
      CREATE TABLE IF NOT EXISTS ${PadDbTables.usageRecord} (
        id INTEGER PRIMARY KEY AUTOINCREMENT,
        date TEXT NOT NULL,
        app_name TEXT DEFAULT 'writech',
        subject TEXT,
        duration_seconds INTEGER DEFAULT 0,
        start_time TEXT NOT NULL,
        end_time TEXT
      )
    ''';

    // await _db.execute(createUsage);
  }

  /// V4建表：练字记录 + 索引
  Future<void> _createTablesV4() async {
    const createPractice = '''
      CREATE TABLE IF NOT EXISTS ${PadDbTables.practiceRecord} (
        id TEXT PRIMARY KEY,
        template_id TEXT NOT NULL,
        character TEXT NOT NULL,
        stroke_score INTEGER DEFAULT 0,
        structure_score INTEGER DEFAULT 0,
        overall_score INTEGER DEFAULT 0,
        stroke_data_json TEXT,
        practice_at TEXT NOT NULL
      )
    ''';

    // 索引优化
    const indexHomeworkStatus = '''
      CREATE INDEX IF NOT EXISTS idx_homework_status 
      ON ${PadDbTables.homework}(status)
    ''';
    const indexErrorSubject = '''
      CREATE INDEX IF NOT EXISTS idx_error_subject 
      ON ${PadDbTables.errorBook}(subject)
    ''';
    const indexPracticeChar = '''
      CREATE INDEX IF NOT EXISTS idx_practice_char 
      ON ${PadDbTables.practiceRecord}(character)
    ''';

    // await _db.execute(createPractice);
    // await _db.execute(indexHomeworkStatus);
    // await _db.execute(indexErrorSubject);
    // await _db.execute(indexPracticeChar);
  }

  // ============================================================
  //  作业缓存 CRUD
  // ============================================================

  /// 缓存作业到本地（用于离线作答）
  Future<void> cacheHomework(CachedHomework homework) async {
    // await _db.insert(
    //   PadDbTables.homework,
    //   homework.toMap(),
    //   conflictAlgorithm: ConflictAlgorithm.replace,
    // );
  }

  /// 获取本地缓存的作业列表
  Future<List<CachedHomework>> getCachedHomeworks({
    String? status,
    int limit = 50,
  }) async {
    // String where = '';
    // List<dynamic> whereArgs = [];
    // if (status != null) {
    //   where = 'status = ?';
    //   whereArgs = [status];
    // }
    // final maps = await _db.query(
    //   PadDbTables.homework,
    //   where: where.isNotEmpty ? where : null,
    //   whereArgs: whereArgs.isNotEmpty ? whereArgs : null,
    //   orderBy: 'cached_at DESC',
    //   limit: limit,
    // );
    // return maps.map((m) => CachedHomework.fromMap(m)).toList();
    return [];
  }

  /// 保存作答进度到本地
  Future<void> saveAnswerProgress({
    required String homeworkId,
    required String questionId,
    String? textAnswer,
    String? strokeDataJson,
  }) async {
    // await _db.insert(
    //   PadDbTables.answerProgress,
    //   {
    //     'homework_id': homeworkId,
    //     'question_id': questionId,
    //     'text_answer': textAnswer,
    //     'stroke_data': strokeDataJson,
    //     'saved_at': DateTime.now().toIso8601String(),
    //   },
    //   conflictAlgorithm: ConflictAlgorithm.replace,
    // );
  }

  /// 获取某作业的所有作答进度
  Future<Map<String, Map<String, dynamic>>> getAnswerProgress(
    String homeworkId,
  ) async {
    // final maps = await _db.query(
    //   PadDbTables.answerProgress,
    //   where: 'homework_id = ?',
    //   whereArgs: [homeworkId],
    // );
    // final result = <String, Map<String, dynamic>>{};
    // for (final m in maps) {
    //   result[m['question_id'] as String] = m;
    // }
    // return result;
    return {};
  }

  // ============================================================
  //  错题本 CRUD
  // ============================================================

  /// 添加错题记录
  Future<void> addErrorEntry(ErrorBookEntry entry) async {
    // await _db.insert(
    //   PadDbTables.errorBook,
    //   entry.toMap(),
    //   conflictAlgorithm: ConflictAlgorithm.replace,
    // );
  }

  /// 获取错题列表（支持按科目/知识点筛选）
  Future<List<ErrorBookEntry>> getErrorEntries({
    String? subject,
    String? knowledgePoint,
    int limit = 50,
    int offset = 0,
  }) async {
    // final conditions = <String>[];
    // final args = <dynamic>[];
    // if (subject != null) {
    //   conditions.add('subject = ?');
    //   args.add(subject);
    // }
    // if (knowledgePoint != null) {
    //   conditions.add('knowledge_point = ?');
    //   args.add(knowledgePoint);
    // }
    // final maps = await _db.query(
    //   PadDbTables.errorBook,
    //   where: conditions.isNotEmpty ? conditions.join(' AND ') : null,
    //   whereArgs: args.isNotEmpty ? args : null,
    //   orderBy: 'created_at DESC',
    //   limit: limit,
    //   offset: offset,
    // );
    // return maps.map((m) => ErrorBookEntry.fromMap(m)).toList();
    return [];
  }

  /// 更新错题复习次数
  Future<void> updateErrorReviewCount(String entryId) async {
    // await _db.rawUpdate('''
    //   UPDATE ${PadDbTables.errorBook}
    //   SET review_count = review_count + 1,
    //       last_review_at = ?
    //   WHERE id = ?
    // ''', [DateTime.now().toIso8601String(), entryId]);
  }

  /// 获取错题统计（按科目分组计数）
  Future<Map<String, int>> getErrorStatsBySubject() async {
    // final maps = await _db.rawQuery('''
    //   SELECT subject, COUNT(*) as count
    //   FROM ${PadDbTables.errorBook}
    //   GROUP BY subject
    // ''');
    // return {for (var m in maps) m['subject'] as String: m['count'] as int};
    return {};
  }

  // ============================================================
  //  学习计划 CRUD
  // ============================================================

  /// 保存学习计划
  Future<void> saveStudyPlan(StudyPlanEntry plan) async {
    // await _db.insert(
    //   PadDbTables.studyPlan,
    //   plan.toMap(),
    //   conflictAlgorithm: ConflictAlgorithm.replace,
    // );
  }

  /// 获取活跃的学习计划列表
  Future<List<Map<String, dynamic>>> getActiveStudyPlans() async {
    // return await _db.query(
    //   PadDbTables.studyPlan,
    //   where: 'is_active = 1',
    //   orderBy: 'start_date ASC',
    // );
    return [];
  }

  /// 更新学习计划进度
  Future<void> updatePlanProgress(
    String planId,
    double progress,
    int completedTasks,
  ) async {
    // await _db.update(
    //   PadDbTables.studyPlan,
    //   {'progress': progress, 'completed_tasks': completedTasks},
    //   where: 'id = ?',
    //   whereArgs: [planId],
    // );
  }

  // ============================================================
  //  练字记录
  // ============================================================

  /// 保存练字记录
  Future<void> savePracticeRecord(PracticeRecord record) async {
    // await _db.insert(
    //   PadDbTables.practiceRecord,
    //   record.toMap(),
    //   conflictAlgorithm: ConflictAlgorithm.replace,
    // );
  }

  /// 获取某字的练习历史（查看进步轨迹）
  Future<List<Map<String, dynamic>>> getPracticeHistory(
    String character, {
    int limit = 20,
  }) async {
    // return await _db.query(
    //   PadDbTables.practiceRecord,
    //   where: 'character = ?',
    //   whereArgs: [character],
    //   orderBy: 'practice_at DESC',
    //   limit: limit,
    // );
    return [];
  }

  // ============================================================
  //  离线操作队列
  // ============================================================

  /// 添加离线操作到队列
  Future<void> enqueueOfflineAction(
    String actionType,
    Map<String, dynamic> payload,
  ) async {
    // await _db.insert(PadDbTables.offlineAction, {
    //   'action_type': actionType,
    //   'payload': jsonEncode(payload),
    //   'created_at': DateTime.now().toIso8601String(),
    //   'status': 'pending',
    // });
  }

  /// 获取待执行的离线操作
  Future<List<Map<String, dynamic>>> getPendingOfflineActions() async {
    // return await _db.query(
    //   PadDbTables.offlineAction,
    //   where: 'status = ? AND retry_count < 5',
    //   whereArgs: ['pending'],
    //   orderBy: 'created_at ASC',
    // );
    return [];
  }

  /// 标记离线操作完成
  Future<void> markOfflineActionDone(int actionId) async {
    // await _db.update(
    //   PadDbTables.offlineAction,
    //   {'status': 'done'},
    //   where: 'id = ?',
    //   whereArgs: [actionId],
    // );
  }

  // ============================================================
  //  使用时长记录
  // ============================================================

  /// 记录使用时长
  Future<void> recordUsage({
    required String date,
    required int durationSeconds,
    required String startTime,
    String? endTime,
    String? subject,
  }) async {
    // await _db.insert(PadDbTables.usageRecord, {
    //   'date': date,
    //   'duration_seconds': durationSeconds,
    //   'start_time': startTime,
    //   'end_time': endTime,
    //   'subject': subject,
    // });
  }

  /// 获取某日使用总时长（秒）
  Future<int> getDailyUsage(String date) async {
    // final result = await _db.rawQuery('''
    //   SELECT COALESCE(SUM(duration_seconds), 0) as total
    //   FROM ${PadDbTables.usageRecord}
    //   WHERE date = ?
    // ''', [date]);
    // return result.first['total'] as int? ?? 0;
    return 0;
  }

  // ============================================================
  //  数据库维护
  // ============================================================

  /// 清理过期缓存数据（30天前的作业缓存、90天前的笔迹暂存）
  Future<void> cleanExpiredData() async {
    final thirtyDaysAgo = DateTime.now()
        .subtract(const Duration(days: 30))
        .toIso8601String();
    final ninetyDaysAgo = DateTime.now()
        .subtract(const Duration(days: 90))
        .toIso8601String();

    // await _db.delete(
    //   PadDbTables.homework,
    //   where: 'cached_at < ? AND status IN (?, ?)',
    //   whereArgs: [thirtyDaysAgo, 'graded', 'expired'],
    // );
    // await _db.delete(
    //   PadDbTables.strokeCache,
    //   where: 'created_at < ?',
    //   whereArgs: [ninetyDaysAgo],
    // );
    // await _db.delete(
    //   PadDbTables.offlineAction,
    //   where: 'status = ? AND created_at < ?',
    //   whereArgs: ['done', thirtyDaysAgo],
    // );
  }

  /// 获取本地数据库存储大小（字节）
  Future<int> getDatabaseSize() async {
    // final dbPath = await getDatabasesPath();
    // final file = File('$dbPath/writech_pad.db');
    // return file.existsSync() ? file.lengthSync() : 0;
    return 0;
  }

  /// 关闭数据库
  Future<void> close() async {
    // await _db.close();
  }
}