import 'dart:async';

/// 消息推送服务（模拟）
/// 提供推送初始化、消息接收回调等功能
class PushService {
  static PushService? _instance;
  final StreamController<PushMessage> _messageController = StreamController.broadcast();

  /// 推送消息流
  Stream<PushMessage> get messageStream => _messageController.stream;

  PushService._internal();

  factory PushService() {
    _instance ??= PushService._internal();
    return _instance!;
  }

  /// 初始化推送服务
  Future<void> initialize() async {
    // TODO: 集成 flutter_local_notifications 或 firebase_messaging
    // 1. 初始化通知插件
    // 2. 请求通知权限
    // 3. 获取设备推送 Token
    // 4. 注册推送 Token 到后端
    print('[PushService] 推送服务已初始化（模拟）');

    // 模拟延迟推送消息
    _simulatePushMessages();
  }

  /// 获取设备推送 Token
  Future<String?> getDeviceToken() async {
    // TODO: 获取实际的推送 Token
    return 'mock_device_token_${DateTime.now().millisecondsSinceEpoch}';
  }

  /// 注册推送 Token 到后端
  Future<void> registerToken(String token) async {
    // TODO: 调用后端接口注册 Token
    print('[PushService] Token 已注册: $token');
  }

  /// 处理接收到的推送消息
  void onMessageReceived(Map<String, dynamic> data) {
    final message = PushMessage(
      id: data['id']?.toString() ?? '',
      title: data['title'] ?? '',
      body: data['body'] ?? '',
      type: data['type'] ?? 'general',
      data: data,
      timestamp: DateTime.now(),
    );
    _messageController.add(message);
  }

  /// 显示本地通知
  Future<void> showLocalNotification({
    required String title,
    required String body,
    String? payload,
  }) async {
    // TODO: 使用 flutter_local_notifications 显示本地通知
    print('[PushService] 本地通知: $title - $body');
  }

  /// 模拟推送消息
  void _simulatePushMessages() {
    Future.delayed(const Duration(seconds: 10), () {
      _messageController.add(PushMessage(
        id: 'mock_1',
        title: '巡检提醒',
        body: '您有一条新的巡检任务待执行',
        type: 'patrol',
        data: {},
        timestamp: DateTime.now(),
      ));
    });
  }

  /// 释放资源
  void dispose() {
    _messageController.close();
  }
}

/// 推送消息模型
class PushMessage {
  final String id;
  final String title;
  final String body;
  final String type;
  final Map<String, dynamic> data;
  final DateTime timestamp;

  PushMessage({
    required this.id,
    required this.title,
    required this.body,
    required this.type,
    required this.data,
    required this.timestamp,
  });
}