import 'dart:typed_data';
import 'package:firebase_core/firebase_core.dart';
import 'package:firebase_messaging/firebase_messaging.dart';
import 'package:flutter/foundation.dart';
import 'package:flutter_local_notifications/flutter_local_notifications.dart';

/// Notification ID for queue alerts (fixed so we can cancel it).
const int _queueAlertNotificationId = 9001;

/// Background handler -- must be top-level function.
@pragma('vm:entry-point')
Future<void> _firebaseMessagingBackgroundHandler(RemoteMessage message) async {
  await Firebase.initializeApp();
  final data = message.data;
  final type = data['type'];

  if (type == 'queue_alert') {
    await _showQueueAlertNotification(data);
  } else if (type == 'queue_alert_cancel') {
    final plugin = FlutterLocalNotificationsPlugin();
    await plugin.cancel(_queueAlertNotificationId);
  }
}

/// Show an insistent queue alert notification (works from background handler too).
Future<void> _showQueueAlertNotification(Map<String, dynamic> data) async {
  final plugin = FlutterLocalNotificationsPlugin();

  final title = data['title'] ?? 'Call Waiting';
  final body = data['body'] ?? 'New call in queue';

  final androidDetails = AndroidNotificationDetails(
    'twp_queue_alerts',
    'Queue Alerts',
    channelDescription: 'Alerts when calls are waiting in queue',
    importance: Importance.max,
    priority: Priority.max,
    playSound: true,
    sound: const RawResourceAndroidNotificationSound('queue_alert'),
    enableVibration: true,
    vibrationPattern: Int64List.fromList([0, 500, 200, 500, 200, 500]),
    ongoing: true,
    autoCancel: false,
    category: AndroidNotificationCategory.alarm,
    additionalFlags: Int32List.fromList([4]), // FLAG_INSISTENT = 4
    fullScreenIntent: true,
    visibility: NotificationVisibility.public,
  );

  await plugin.show(
    _queueAlertNotificationId,
    title,
    body,
    NotificationDetails(android: androidDetails),
  );
}

/// Push notification service for queue alerts and general notifications.
///
/// FCM token registration is handled via the WebView JavaScript bridge
/// instead of a REST API call. The token is exposed via [fcmToken] and
/// injected into the web page by [PhoneScreen].
class PushNotificationService {
  final FirebaseMessaging _messaging = FirebaseMessaging.instance;
  final FlutterLocalNotificationsPlugin _localNotifications =
      FlutterLocalNotificationsPlugin();
  String? _fcmToken;

  String? get fcmToken => _fcmToken;

  Future<void> initialize() async {
    FirebaseMessaging.onBackgroundMessage(_firebaseMessagingBackgroundHandler);

    await _messaging.requestPermission(
      alert: true,
      badge: true,
      sound: true,
      criticalAlert: true,
    );

    // Initialize local notifications
    const androidSettings =
        AndroidInitializationSettings('@mipmap/ic_launcher');
    const initSettings = InitializationSettings(android: androidSettings);
    await _localNotifications.initialize(initSettings);

    // Get FCM token
    final token = await _messaging.getToken();
    debugPrint(
        'FCM token: ${token != null ? "${token.substring(0, 20)}..." : "NULL"}');
    if (token != null) {
      _fcmToken = token;
    } else {
      debugPrint(
          'FCM: Failed to get token - Firebase may not be configured correctly');
    }

    // Listen for token refresh
    _messaging.onTokenRefresh.listen((token) {
      _fcmToken = token;
    });

    // Handle foreground messages
    FirebaseMessaging.onMessage.listen(_handleForegroundMessage);
  }

  void _handleForegroundMessage(RemoteMessage message) {
    final data = message.data;
    final type = data['type'];

    // Queue alert -- show insistent notification
    if (type == 'queue_alert') {
      _showQueueAlertNotification(data);
      return;
    }

    // Queue alert cancel -- dismiss notification
    if (type == 'queue_alert_cancel') {
      _localNotifications.cancel(_queueAlertNotificationId);
      return;
    }

    // Show local notification for other types (missed call, etc.)
    _localNotifications.show(
      message.hashCode,
      data['title'] ?? 'TWP Softphone',
      data['body'] ?? '',
      const NotificationDetails(
        android: AndroidNotificationDetails(
          'twp_general',
          'General Notifications',
          importance: Importance.high,
          priority: Priority.high,
        ),
      ),
    );
  }

  /// Cancel any active queue alert.
  void cancelQueueAlert() {
    _localNotifications.cancel(_queueAlertNotificationId);
  }
}