import 'dart:math';
import 'package:flutter/foundation.dart';
import 'package:flutter_local_notifications/flutter_local_notifications.dart';
import 'package:timezone/timezone.dart' as tz;
import 'package:timezone/data/latest_all.dart' as tz;

/// 알림 서비스 싱글톤 클래스
class NotificationService {
  // 싱글톤 인스턴스
  static final NotificationService _instance = NotificationService._internal();
  factory NotificationService() => _instance;
  NotificationService._internal();

  // Flutter Local Notifications 플러그인
  final FlutterLocalNotificationsPlugin _notifications = FlutterLocalNotificationsPlugin();
  
  // 알림 채널 정보
  static const String _channelId = 'lunchpick_visit_reminder';
  static const String _channelName = '방문 확인 알림';
  static const String _channelDescription = '점심 식사 후 방문을 확인하는 알림입니다.';
  
  // 알림 ID (방문 확인용)
  static const int _visitReminderNotificationId = 1;

  /// 알림 서비스 초기화
  Future<bool> initialize() async {
    // 시간대 초기화
    tz.initializeTimeZones();
    
    // Android 초기화 설정
    const androidInitSettings = AndroidInitializationSettings('@mipmap/ic_launcher');
    
    // iOS 초기화 설정
    final iosInitSettings = DarwinInitializationSettings(
      requestAlertPermission: true,
      requestBadgePermission: true,
      requestSoundPermission: true,
      onDidReceiveLocalNotification: (id, title, body, payload) async {
        // iOS 9 이하 버전 대응
      },
    );
    
    // macOS 초기화 설정
    final macOSInitSettings = DarwinInitializationSettings(
      requestAlertPermission: true,
      requestBadgePermission: true,
      requestSoundPermission: true,
    );
    
    // 플랫폼별 초기화 설정 통합
    final initSettings = InitializationSettings(
      android: androidInitSettings,
      iOS: iosInitSettings,
      macOS: macOSInitSettings,
    );
    
    // 알림 플러그인 초기화
    final initialized = await _notifications.initialize(
      initSettings,
      onDidReceiveNotificationResponse: _onNotificationTap,
      onDidReceiveBackgroundNotificationResponse: _onBackgroundNotificationTap,
    );
    
    // Android 알림 채널 생성 (웹이 아닌 경우에만)
    if (!kIsWeb && defaultTargetPlatform == TargetPlatform.android) {
      await _createNotificationChannel();
    }
    
    return initialized ?? false;
  }

  /// Android 알림 채널 생성
  Future<void> _createNotificationChannel() async {
    const androidChannel = AndroidNotificationChannel(
      _channelId,
      _channelName,
      description: _channelDescription,
      importance: Importance.high,
      playSound: true,
      enableVibration: true,
    );
    
    await _notifications
        .resolvePlatformSpecificImplementation<AndroidFlutterLocalNotificationsPlugin>()
        ?.createNotificationChannel(androidChannel);
  }

  /// 알림 권한 요청
  Future<bool> requestPermission() async {
    if (!kIsWeb && defaultTargetPlatform == TargetPlatform.android) {
      final androidImplementation = _notifications
          .resolvePlatformSpecificImplementation<AndroidFlutterLocalNotificationsPlugin>();
      
      if (androidImplementation != null) {
        // Android 13 (API 33) 이상에서는 권한 요청이 필요
        if (!kIsWeb && (true /* 웹에서는 버전 체크 불가 */)) {
          final granted = await androidImplementation.requestNotificationsPermission();
          return granted ?? false;
        }
        // Android 12 이하는 자동 허용
        return true;
      }
    } else if (!kIsWeb && (defaultTargetPlatform == TargetPlatform.iOS || defaultTargetPlatform == TargetPlatform.macOS)) {
      final iosImplementation = _notifications
          .resolvePlatformSpecificImplementation<IOSFlutterLocalNotificationsPlugin>();
      final macosImplementation = _notifications
          .resolvePlatformSpecificImplementation<MacOSFlutterLocalNotificationsPlugin>();
      
      if (iosImplementation != null) {
        final granted = await iosImplementation.requestPermissions(
          alert: true,
          badge: true,
          sound: true,
        );
        return granted ?? false;
      }
      
      if (macosImplementation != null) {
        final granted = await macosImplementation.requestPermissions(
          alert: true,
          badge: true,
          sound: true,
        );
        return granted ?? false;
      }
    }
    
    return false;
  }

  /// 권한 상태 확인
  Future<bool> checkPermission() async {
    if (!kIsWeb && defaultTargetPlatform == TargetPlatform.android) {
      final androidImplementation = _notifications
          .resolvePlatformSpecificImplementation<AndroidFlutterLocalNotificationsPlugin>();
      
      if (androidImplementation != null) {
        // Android 13 이상에서만 권한 확인
        if (!kIsWeb && (true /* 웹에서는 버전 체크 불가 */)) {
          final granted = await androidImplementation.areNotificationsEnabled();
          return granted ?? false;
        }
        // Android 12 이하는 자동 허용
        return true;
      }
    }
    
    // iOS/macOS는 설정에서 확인
    return true;
  }

  // 알림 탭 콜백
  static void Function(NotificationResponse)? onNotificationTap;
  
  /// 방문 확인 알림 예약
  Future<void> scheduleVisitReminder({
    required String restaurantId,
    required String restaurantName,
    required DateTime recommendationTime,
  }) async {
    try {
      // 1.5~2시간 사이의 랜덤 시간 계산 (90~120분)
      final randomMinutes = 90 + Random().nextInt(31); // 90 + 0~30분
      final scheduledTime = tz.TZDateTime.now(tz.local).add(
        Duration(minutes: randomMinutes),
      );
      
      // 알림 상세 설정
      final androidDetails = AndroidNotificationDetails(
        _channelId,
        _channelName,
        channelDescription: _channelDescription,
        importance: Importance.high,
        priority: Priority.high,
        ticker: '방문 확인',
        icon: '@mipmap/ic_launcher',
        autoCancel: true,
        enableVibration: true,
        playSound: true,
      );
      
      const iosDetails = DarwinNotificationDetails(
        presentAlert: true,
        presentBadge: true,
        presentSound: true,
        sound: 'default',
      );
      
      final notificationDetails = NotificationDetails(
        android: androidDetails,
        iOS: iosDetails,
        macOS: iosDetails,
      );
      
      // 알림 예약
      await _notifications.zonedSchedule(
        _visitReminderNotificationId,
        '다녀왔음? 🍴',
        '$restaurantName 어땠어요? 방문 기록을 남겨주세요!',
        scheduledTime,
        notificationDetails,
        androidScheduleMode: AndroidScheduleMode.exactAllowWhileIdle,
        uiLocalNotificationDateInterpretation:
            UILocalNotificationDateInterpretation.absoluteTime,
        payload: 'visit_reminder|$restaurantId|$restaurantName|${recommendationTime.toIso8601String()}',
      );
      
      if (kDebugMode) {
        print('알림 예약됨: ${scheduledTime.toLocal()} ($randomMinutes분 후)');
      }
    } catch (e) {
      if (kDebugMode) {
        print('알림 예약 실패: $e');
      }
    }
  }

  /// 예약된 방문 확인 알림 취소
  Future<void> cancelVisitReminder() async {
    await _notifications.cancel(_visitReminderNotificationId);
  }

  /// 모든 알림 취소
  Future<void> cancelAllNotifications() async {
    await _notifications.cancelAll();
  }

  /// 예약된 알림 목록 조회
  Future<List<PendingNotificationRequest>> getPendingNotifications() async {
    return await _notifications.pendingNotificationRequests();
  }

  /// 알림 탭 이벤트 처리
  void _onNotificationTap(NotificationResponse response) {
    if (onNotificationTap != null) {
      onNotificationTap!(response);
    } else if (response.payload != null) {
      if (kDebugMode) {
        print('알림 탭: ${response.payload}');
      }
    }
  }

  /// 백그라운드 알림 탭 이벤트 처리
  @pragma('vm:entry-point')
  static void _onBackgroundNotificationTap(NotificationResponse response) {
    if (onNotificationTap != null) {
      onNotificationTap!(response);
    } else if (response.payload != null) {
      if (kDebugMode) {
        print('백그라운드 알림 탭: ${response.payload}');
      }
    }
  }

  /// 즉시 알림 표시 (테스트용)
  Future<void> showImmediateNotification({
    required String title,
    required String body,
  }) async {
    const androidDetails = AndroidNotificationDetails(
      _channelId,
      _channelName,
      channelDescription: _channelDescription,
      importance: Importance.high,
      priority: Priority.high,
    );
    
    const iosDetails = DarwinNotificationDetails();
    
    const notificationDetails = NotificationDetails(
      android: androidDetails,
      iOS: iosDetails,
      macOS: iosDetails,
    );
    
    await _notifications.show(
      0,
      title,
      body,
      notificationDetails,
    );
  }
}