// lib/services/app_lifecycle_manager.dart
import 'dart:async';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:media_kit/media_kit.dart';

/// App 生命周期状态（扩展了 Flutter 原生状态）
enum AppLifecycleStatus {
  /// 应用正在启动（初始化阶段）
  launching,

  /// 应用在前台，用户可交互
  resumed,

  /// 应用在前台但不可交互（如：来电、系统弹窗）
  inactive,

  /// 应用在后台
  paused,

  /// 应用即将被销毁
  detached,

  /// 应用已进入后台且播放停止（自定义，用于播放策略）
  backgroundIdle,
}

/// App 生命周期管理器
///
/// 职责：
/// 1. 统一监听 Flutter 的 AppLifecycleState
/// 2. 管理播放器在前后台的行为
/// 3. 管理渲染调度器的运行状态
/// 4. 管理 WebDAV 的缓存策略
class AppLifecycleManager extends ChangeNotifier {
  static final AppLifecycleManager _instance = AppLifecycleManager._internal();
  factory AppLifecycleManager() => _instance;
  AppLifecycleManager._internal();

  // ---- 当前状态 ----
  AppLifecycleStatus _status = AppLifecycleStatus.launching;
  AppLifecycleStatus get status => _status;

  // ---- 上次进入后台的时间 ----
  DateTime? _backgroundedAt;
  DateTime? get backgroundedAt => _backgroundedAt;

  // ---- 是否在后台 ----
  bool get isInBackground =>
      _status == AppLifecycleStatus.paused ||
      _status == AppLifecycleStatus.inactive ||
      _status == AppLifecycleStatus.detached;

  bool get isInForeground => _status == AppLifecycleStatus.resumed;

  // ---- 后台时长 ----
  Duration get backgroundDuration {
    if (_backgroundedAt == null) return Duration.zero;
    return DateTime.now().difference(_backgroundedAt!);
  }

  // ---- 是否处于"长后台"（超过 5 分钟） ----
  bool get isLongBackground => backgroundDuration > const Duration(minutes: 5);

  // ---- 监听器 ----
  final List<void Function(AppLifecycleStatus)> _listeners = [];

  // ---- Flutter 原生生命周期订阅 ----
  late final WidgetsBindingObserver _observer;
  bool _isObserving = false;

  // ---- 初始化 ----
  void init() {
    if (_isObserving) return;
    _isObserving = true;

    _observer = _AppLifecycleObserver(this);
    WidgetsBinding.instance.addObserver(_observer);

    // 获取初始状态
    _updateStatus(AppLifecycleStatus.resumed);

    debugPrint('📱 AppLifecycleManager 已初始化');
  }

  // ---- 状态更新 ----
  void _handleNativeState(AppLifecycleState state) {
    final newStatus = _convertNativeState(state);

    // 状态变化时更新
    if (newStatus != _status) {
      _updateStatus(newStatus);
    }

    // 记录进入后台的时间
    if (newStatus == AppLifecycleStatus.paused ||
        newStatus == AppLifecycleStatus.inactive) {
      if (_backgroundedAt == null) {
        _backgroundedAt = DateTime.now();
        debugPrint('📱 App 进入后台: ${_backgroundedAt}');
      }
    }

    // 回到前台时，如果是长后台，触发通知
    if (newStatus == AppLifecycleStatus.resumed) {
      if (_backgroundedAt != null) {
        final duration = backgroundDuration;
        debugPrint('📱 App 回到前台，后台时长: ${duration.inMinutes}分钟');
        _backgroundedAt = null;

        // 如果是长后台，通知监听器做重连等操作
        if (duration > const Duration(minutes: 5)) {
          _notifyListeners(AppLifecycleStatus.backgroundIdle);
        }
      }
    }
  }

  void _updateStatus(AppLifecycleStatus newStatus) {
    final oldStatus = _status;
    _status = newStatus;
    debugPrint('📱 生命周期状态变化: $oldStatus → $newStatus');
    notifyListeners();
    _notifyListeners(newStatus);
  }

  AppLifecycleStatus _convertNativeState(AppLifecycleState state) {
    switch (state) {
      case AppLifecycleState.resumed:
        return AppLifecycleStatus.resumed;
      case AppLifecycleState.inactive:
        return AppLifecycleStatus.inactive;
      case AppLifecycleState.paused:
        return AppLifecycleStatus.paused;
      case AppLifecycleState.detached:
        return AppLifecycleStatus.detached;
      default:
        return AppLifecycleStatus.paused;
    }
  }

  // ---- 自定义监听器管理 ----
  void addListenerToManager(void Function(AppLifecycleStatus) listener) {
    _listeners.add(listener);
  }

  void removeListenerFromManager(void Function(AppLifecycleStatus) listener) {
    _listeners.remove(listener);
  }

  void _notifyListeners(AppLifecycleStatus status) {
    for (final listener in _listeners) {
      try {
        listener(status);
      } catch (e) {
        debugPrint('❌ 生命周期监听器执行失败: $e');
      }
    }
  }

  // ---- 检查是否需要重新连接 WebDAV ----
  bool get shouldRecheckWebDAV {
    if (!isInForeground) return false;
    if (_backgroundedAt == null) return false;
    return isLongBackground;
  }

  // ---- 释放 ----
  void dispose() {
    if (_isObserving) {
      WidgetsBinding.instance.removeObserver(_observer);
      _isObserving = false;
    }
    _listeners.clear();
    super.dispose();
  }
}

/// 内部观察者（绑定 WidgetsBinding）
class _AppLifecycleObserver extends WidgetsBindingObserver {
  final AppLifecycleManager _manager;

  _AppLifecycleObserver(this._manager);

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    _manager._handleNativeState(state);
  }
}