import 'package:flutter/material.dart';
import 'package:flutter_local_notifications/flutter_local_notifications.dart';
import 'package:timezone/timezone.dart' as tz;

class NotificationService {
  static final _plugin = FlutterLocalNotificationsPlugin();
  static bool _initialised = false;

  static const _channelId = 'daily_reminder';
  static const _notificationId = 0;

  static Future<void> init() async {
    if (_initialised) return;
    const android = AndroidInitializationSettings('@mipmap/ic_launcher');
    await _plugin.initialize(
      settings: const InitializationSettings(android: android),
    );
    _initialised = true;
  }

  static Future<bool> requestPermission() async {
    final android = _plugin.resolvePlatformSpecificImplementation<
        AndroidFlutterLocalNotificationsPlugin>();
    return (await android?.requestNotificationsPermission()) ?? false;
  }

  static Future<void> scheduleDaily(TimeOfDay time) async {
    await _plugin.cancelAll();
    const details = NotificationDetails(
      android: AndroidNotificationDetails(
        _channelId,
        'Daily reminder',
        channelDescription: 'Reminds you to log your mood',
        importance: Importance.defaultImportance,
        priority: Priority.defaultPriority,
      ),
    );
    await _plugin.zonedSchedule(
      id: _notificationId,
      title: 'DailyYou',
      body: 'Time to log your mood!',
      scheduledDate: _nextInstanceOfTime(time.hour, time.minute),
      notificationDetails: details,
      androidScheduleMode: AndroidScheduleMode.inexactAllowWhileIdle,
      matchDateTimeComponents: DateTimeComponents.time,
    );
  }

  static Future<void> cancelAll() => _plugin.cancelAll();

  static tz.TZDateTime _nextInstanceOfTime(int hour, int minute) {
    final now = tz.TZDateTime.now(tz.UTC);
    final offset = DateTime.now().timeZoneOffset;
    var targetMinutes = hour * 60 + minute - offset.inMinutes;
    // Normalise into [0, 24*60)
    targetMinutes = ((targetMinutes % (24 * 60)) + 24 * 60) % (24 * 60);
    final utcHour = targetMinutes ~/ 60;
    final utcMin = targetMinutes % 60;
    var scheduled =
        tz.TZDateTime(tz.UTC, now.year, now.month, now.day, utcHour, utcMin);
    if (scheduled.isBefore(now)) {
      scheduled = scheduled.add(const Duration(days: 1));
    }
    return scheduled;
  }
}