import 'dart:developer' as developer;
import 'dart:io';
import 'dart:async';
import 'package:path_provider/path_provider.dart';
import 'package:intl/intl.dart';

/// 日志级别
enum LogLevel {
  debug,
  info,
  warning,
  error,
}

/// 日志工具类
///
/// 提供统一的日志记录接口，支持控制台输出和文件存储
class Logger {
  /// 当前日志级别，低于此级别的日志不会被输出
  static LogLevel _currentLevel = LogLevel.debug;

  /// 默认标签
  static const String _defaultTag = 'App';

  /// 文件日志相关
  static IOSink? _logSink;
  static File? _currentLogFile;
  static bool _fileLogEnabled = false;
  static String? _logDirPath;
  static final DateFormat _dateFormat = DateFormat('yyyy-MM-dd HH:mm:ss.SSS');
  static final DateFormat _fileDateFormat = DateFormat('yyyy-MM-dd');

  /// 最大单个日志文件大小 (2MB)
  static const int _maxFileSize = 2 * 1024 * 1024;

  /// 最多保留日志文件数量
  static const int _maxLogFiles = 7;

  /// 写入计数器，用于节流轮转检查和刷盘
  static int _writeCount = 0;

  /// 轮转检查间隔（每 100 次写入检查一次）
  static const int _rotationCheckInterval = 100;

  /// 刷盘间隔（每 50 次写入刷一次）
  static const int _flushInterval = 50;

  /// 轮转锁，防止并发轮转
  static bool _isRotating = false;

  /// 当前日志文件的日期标识，用于快速判断是否需要换天
  static String _currentFileDate = '';

  /// 初始化文件日志
  static Future<void> initFileLog() async {
    try {
      final dir = await getApplicationDocumentsDirectory();
      _logDirPath = '${dir.path}/logs';
      final logDir = Directory(_logDirPath!);
      if (!await logDir.exists()) {
        await logDir.create(recursive: true);
      }
      await _openLogFile();
      _fileLogEnabled = true;
      Logger.i('Logger', '文件日志初始化成功: $_logDirPath');
    } catch (e) {
      developer.log('[Logger] 文件日志初始化失败: $e');
    }
  }

  /// 打开/创建当前日志文件
  static Future<void> _openLogFile() async {
    final today = _fileDateFormat.format(DateTime.now());
    final filePath = '$_logDirPath/app_$today.log';
    _currentLogFile = File(filePath);
    // 先关闭旧 sink，必须 await 确保关闭完成
    await _logSink?.flush();
    await _logSink?.close();
    _logSink = _currentLogFile!.openWrite(mode: FileMode.append);
    _currentFileDate = today;
  }

  /// 检查日志文件是否需要轮转（受节流和锁保护）
  static Future<void> _checkRotation() async {
    if (_isRotating || _currentLogFile == null) return;
    _isRotating = true;
    try {
      // 检查日期是否变更
      final today = _fileDateFormat.format(DateTime.now());
      if (_currentFileDate != today) {
        await _openLogFile();
      }
      // 检查文件大小
      if (await _currentLogFile!.exists()) {
        final size = await _currentLogFile!.length();
        if (size > _maxFileSize) {
          final now = DateTime.now();
          final suffix = DateFormat('HHmmss').format(now);
          final todayStr = _fileDateFormat.format(now);
          final newPath = '$_logDirPath/app_${todayStr}_$suffix.log';
          await _logSink?.flush();
          await _logSink?.close();
          _currentLogFile = File(newPath);
          _logSink = _currentLogFile!.openWrite(mode: FileMode.append);
        }
      }
      // 清理旧日志文件
      await _cleanOldLogs();
    } catch (_) {} finally {
      _isRotating = false;
    }
  }

  /// 清理旧日志文件，保留最近 _maxLogFiles 个
  static Future<void> _cleanOldLogs() async {
    if (_logDirPath == null) return;
    try {
      final logDir = Directory(_logDirPath!);
      final files = await logDir
          .list()
          .where((e) => e is File && e.path.endsWith('.log'))
          .cast<File>()
          .toList();
      if (files.length > _maxLogFiles) {
        files.sort((a, b) => a.path.compareTo(b.path));
        final toDelete = files.sublist(0, files.length - _maxLogFiles);
        for (final f in toDelete) {
          await f.delete();
        }
      }
    } catch (_) {}
  }

  /// 单行最大字符数，超过则分批写入
  static const int _maxLineLength = 4000;

  /// 写入日志到文件
  static void _writeToFile(String level, String tag, String message) {
    if (!_fileLogEnabled || _logSink == null) return;
    try {
      final timestamp = _dateFormat.format(DateTime.now());
      if (message.length <= _maxLineLength) {
        _logSink!.writeln('$timestamp [$level][$tag] $message');
      } else {
        final totalParts = (message.length + _maxLineLength - 1) ~/ _maxLineLength;
        for (var i = 0; i < totalParts; i++) {
          final start = i * _maxLineLength;
          final end = start + _maxLineLength > message.length ? message.length : start + _maxLineLength;
          final chunk = message.substring(start, end);
          _logSink!.writeln('$timestamp [$level][$tag] [${i + 1}/$totalParts] $chunk');
        }
      }
      _writeCount++;

      // 定期刷盘，确保数据写入磁盘
      if (_writeCount % _flushInterval == 0) {
        _logSink!.flush();
      }

      // 定期检查轮转（节流，不是每次写入都检查）
      if (_writeCount % _rotationCheckInterval == 0) {
        _checkRotation();
      }
    } catch (e) {
      // 文件写入失败不应影响业务逻辑（尤其是 Dio 拦截器链）
      developer.log('[Logger] 文件写入失败: $e');
    }
  }

  /// 获取日志目录路径
  static String? get logDirPath => _logDirPath;

  /// 获取所有日志文件列表
  static Future<List<File>> getLogFiles() async {
    if (_logDirPath == null) return [];
    final logDir = Directory(_logDirPath!);
    if (!await logDir.exists()) return [];
    final files = await logDir
        .list()
        .where((e) => e is File && e.path.endsWith('.log'))
        .cast<File>()
        .toList();
    files.sort((a, b) => b.path.compareTo(a.path)); // 最新在前
    return files;
  }

  /// 刷新缓冲区（导出前调用）
  static Future<void> flush() async {
    await _logSink?.flush();
  }

  /// 设置日志级别
  static void setLevel(LogLevel level) {
    _currentLevel = level;
  }

  /// 输出调试日志 (不带标签版本)
  static void debug(String message) {
    if (_currentLevel.index <= LogLevel.debug.index) {
      _log('DEBUG', _defaultTag, message);
    }
  }

  /// 输出调试日志
  static void d(String tag, String message) {
    if (_currentLevel.index <= LogLevel.debug.index) {
      _log('DEBUG', tag, message);
    }
  }

  /// 输出信息日志 (不带标签版本)
  static void info(String message) {
    if (_currentLevel.index <= LogLevel.info.index) {
      _log('INFO', _defaultTag, message);
    }
  }

  /// 输出信息日志
  static void i(String tag, String message) {
    if (_currentLevel.index <= LogLevel.info.index) {
      _log('INFO', tag, message);
    }
  }

  /// 输出警告日志 (不带标签版本)
  static void warning(String message) {
    if (_currentLevel.index <= LogLevel.warning.index) {
      _log('WARNING', _defaultTag, message);
    }
  }

  /// 输出警告日志
  static void w(String tag, String message) {
    if (_currentLevel.index <= LogLevel.warning.index) {
      _log('WARNING', tag, message);
    }
  }

  /// 输出错误日志 (不带标签版本)
  static void error(String message, [dynamic error, StackTrace? stackTrace]) {
    if (_currentLevel.index <= LogLevel.error.index) {
      _log('ERROR', _defaultTag, message);
      if (error != null) {
        _log('ERROR', _defaultTag, 'Original error: $error');
      }
      if (stackTrace != null) {
        _log('ERROR', _defaultTag, 'Stack trace: $stackTrace');
      }
    }
  }

  /// 输出错误日志
  static void e(String tag, String message, [dynamic error, StackTrace? stackTrace]) {
    if (_currentLevel.index <= LogLevel.error.index) {
      _log('ERROR', tag, message);
      if (error != null) {
        _log('ERROR', tag, 'Original error: $error');
      }
      if (stackTrace != null) {
        _log('ERROR', tag, 'Stack trace: $stackTrace');
      }
    }
  }

  /// 内部日志输出方法
  static void _log(String level, String tag, String message) {
    if (message.length <= _maxLineLength) {
      developer.log('[$tag]: $message');
    } else {
      final totalParts = (message.length + _maxLineLength - 1) ~/ _maxLineLength;
      for (var i = 0; i < totalParts; i++) {
        final start = i * _maxLineLength;
        final end = start + _maxLineLength > message.length ? message.length : start + _maxLineLength;
        developer.log('[$tag]: [${i + 1}/$totalParts] ${message.substring(start, end)}');
      }
    }
    _writeToFile(level, tag, message);
  }
}