supplements/lib/services/notification_service.dart

import 'package:flutter_local_notifications/flutter_local_notifications.dart';
import 'package:timezone/timezone.dart' as tz;
import 'package:timezone/data/latest.dart' as tz;
import '../models/supplement.dart';

class NotificationService {
  static final NotificationService _instance = NotificationService._internal();
  factory NotificationService() => _instance;
  NotificationService._internal();

  final FlutterLocalNotificationsPlugin _notifications = FlutterLocalNotificationsPlugin();

  Future<void> initialize() async {
    tz.initializeTimeZones();
    
    const AndroidInitializationSettings androidSettings = AndroidInitializationSettings('@mipmap/ic_launcher');
    const DarwinInitializationSettings iosSettings = DarwinInitializationSettings(
      requestAlertPermission: true,
      requestBadgePermission: true,
      requestSoundPermission: true,
    );

    const InitializationSettings initSettings = InitializationSettings(
      android: androidSettings,
      iOS: iosSettings,
    );

    await _notifications.initialize(initSettings);
  }

  Future<bool> requestPermissions() async {
    final androidPlugin = _notifications.resolvePlatformSpecificImplementation<AndroidFlutterLocalNotificationsPlugin>();
    if (androidPlugin != null) {
      await androidPlugin.requestNotificationsPermission();
    }
    
    final iosPlugin = _notifications.resolvePlatformSpecificImplementation<IOSFlutterLocalNotificationsPlugin>();
    if (iosPlugin != null) {
      await iosPlugin.requestPermissions(
        alert: true,
        badge: true,
        sound: true,
      );
    }
    
    return true;
  }

  Future<void> scheduleSupplementReminders(Supplement supplement) async {
    // Cancel existing notifications for this supplement
    await cancelSupplementReminders(supplement.id!);

    for (int i = 0; i < supplement.reminderTimes.length; i++) {
      final timeStr = supplement.reminderTimes[i];
      final timeParts = timeStr.split(':');
      final hour = int.parse(timeParts[0]);
      final minute = int.parse(timeParts[1]);

      final notificationId = supplement.id! * 100 + i; // Unique ID for each reminder

      await _notifications.zonedSchedule(
        notificationId,
        'Time for ${supplement.name}',
        'Take ${supplement.dosage} ${supplement.unit}',
        _nextInstanceOfTime(hour, minute),
        const NotificationDetails(
          android: AndroidNotificationDetails(
            'supplement_reminders',
            'Supplement Reminders',
            channelDescription: 'Notifications for supplement intake reminders',
            importance: Importance.high,
            priority: Priority.high,
          ),
          iOS: DarwinNotificationDetails(),
        ),
        androidScheduleMode: AndroidScheduleMode.exactAllowWhileIdle,
        matchDateTimeComponents: DateTimeComponents.time,
      );
    }
  }

  Future<void> cancelSupplementReminders(int supplementId) async {
    // Cancel all notifications for this supplement (up to 10 possible reminders)
    for (int i = 0; i < 10; i++) {
      final notificationId = supplementId * 100 + i;
      await _notifications.cancel(notificationId);
    }
  }

  Future<void> cancelAllReminders() async {
    await _notifications.cancelAll();
  }

  tz.TZDateTime _nextInstanceOfTime(int hour, int minute) {
    final tz.TZDateTime now = tz.TZDateTime.now(tz.local);
    tz.TZDateTime scheduledDate = tz.TZDateTime(tz.local, now.year, now.month, now.day, hour, minute);
    
    if (scheduledDate.isBefore(now)) {
      scheduledDate = scheduledDate.add(const Duration(days: 1));
    }
    
    return scheduledDate;
  }

  Future<void> showInstantNotification(String title, String body) async {
    const NotificationDetails notificationDetails = NotificationDetails(
      android: AndroidNotificationDetails(
        'instant_notifications',
        'Instant Notifications',
        channelDescription: 'Instant notifications for supplement app',
        importance: Importance.high,
        priority: Priority.high,
      ),
      iOS: DarwinNotificationDetails(),
    );

    await _notifications.show(
      DateTime.now().millisecondsSinceEpoch ~/ 1000,
      title,
      body,
      notificationDetails,
    );
  }
}