import 'package:flutter_local_notifications/flutter_local_notifications.dart';
import 'package:supplements/logging.dart';
import 'package:timezone/data/latest.dart' as tzdata;
import 'package:timezone/timezone.dart' as tz;
import 'dart:convert';
import 'package:supplements/services/notification_router.dart';

import '../models/supplement.dart';

/// A minimal notification scheduler focused purely on:
/// - Initialization
/// - Permission requests
/// - Scheduling daily notifications for supplements
/// - Canceling scheduled notifications
///
/// No retries, no snooze, no database logic.
class SimpleNotificationService {
  SimpleNotificationService._internal();
  static final SimpleNotificationService instance =
      SimpleNotificationService._internal();

  final FlutterLocalNotificationsPlugin _plugin =
      FlutterLocalNotificationsPlugin();

  bool _initialized = false;

  // Channel IDs
  static const String _channelDailyId = 'supplement_reminders';
  static const String _channelDailyName = 'Supplement Reminders';
  static const String _channelDailyDescription = 'Daily supplement intake reminders';

  /// Initialize timezone data and the notifications plugin.
  ///
  /// Note: This does not request runtime permissions. Call [requestPermissions]
  /// to prompt the user for notification permissions.
  Future<void> initialize() async {
    if (_initialized) return;

    // Initialize timezone database and set a sane default.
    // If you prefer, replace 'Europe/Amsterdam' with your preferred default,
    // or integrate a platform timezone resolver.
    tzdata.initializeTimeZones();
    tz.setLocalLocation(tz.getLocation('Europe/Amsterdam'));

    const androidSettings = AndroidInitializationSettings('@mipmap/ic_launcher');
    final iosSettings = DarwinInitializationSettings(
      requestAlertPermission: false,
      requestBadgePermission: false,
      requestSoundPermission: false,
      notificationCategories: [
        DarwinNotificationCategory(
          'single',
          actions: [
            DarwinNotificationAction.plain('take_single', 'Take'),
          ],
        ),
        DarwinNotificationCategory(
          'group',
          actions: [
            DarwinNotificationAction.plain('take_group', 'Take All'),
          ],
        ),
      ],
    );
    const linuxSettings = LinuxInitializationSettings(
      defaultActionName: 'Open notification',
    );

    final initSettings = InitializationSettings(
      android: androidSettings,
      iOS: iosSettings,
      linux: linuxSettings,
    );

    await _plugin.initialize(
      initSettings,
      onDidReceiveNotificationResponse: (response) {
        NotificationRouter.instance.handleNotificationResponse(response);
      },
    );

    _initialized = true;
  }

  /// Request runtime notification permissions.
  ///
  /// On Android 13+, this will prompt for POST_NOTIFICATIONS. On older Android,
  /// this is a no-op. On iOS, it requests alert/badge/sound.
  Future<bool> requestPermissions() async {
    // Ensure the plugin is ready before requesting permissions.
    if (!_initialized) {
      await initialize();
    }

    bool granted = true;

    final androidPlugin = _plugin
        .resolvePlatformSpecificImplementation<
            AndroidFlutterLocalNotificationsPlugin>();
    if (androidPlugin != null) {
      final ok = await androidPlugin.requestNotificationsPermission();
      granted = granted && (ok == true);
    }

    final iosPlugin = _plugin
        .resolvePlatformSpecificImplementation<
            IOSFlutterLocalNotificationsPlugin>();
    if (iosPlugin != null) {
      final ok = await iosPlugin.requestPermissions(
        alert: true,
        badge: true,
        sound: true,
      );
      granted = granted && (ok == true);
    }

    return granted;
  }

  /// Schedule grouped daily reminders for a list of supplements.
  ///
  /// - Groups supplements by HH:mm and schedules one notification per time slot.
  /// - Uses daily recurrence via matchDateTimeComponents: DateTimeComponents.time.
  /// - Keeps iOS pending notifications well below the 64 limit.
  ///
  /// IDs:
  /// - Group ID per time slot: 40000 + hour*60 + minute.
  /// - Stable and predictable for cancel/update operations.
  Future<void> scheduleDailyGroupedReminders(List<Supplement> supplements) async {
    if (!_initialized) {
      await initialize();
    }

    printLog('🛠 scheduleDailyGroupedReminders -> ${supplements.length} supplements');

    // Clear everything first to avoid duplicates or stale schedules
    await cancelAll();
    printLog('🧹 Cleared all existing notifications before scheduling groups');

    // Build groups: HH:mm -> list<Supplement>
    final Map<String, List<Supplement>> groups = {};
    for (final s in supplements.where((s) => s.isActive && s.reminderTimes.isNotEmpty && s.id != null)) {
      for (final timeStr in s.reminderTimes) {
        final parts = timeStr.split(':');
        if (parts.length != 2) continue;
        final hour = int.tryParse(parts[0]);
        final minute = int.tryParse(parts[1]);
        if (hour == null || minute == null) continue;

        final key = '${hour.toString().padLeft(2, '0')}:${minute.toString().padLeft(2, '0')}';
        groups.putIfAbsent(key, () => []).add(s);
      }
    }

    printLog('⏱ Found ${groups.length} time group(s): ${groups.keys.toList()}');

    if (groups.isEmpty) {
      printLog('⚠️ No groups to schedule (no active supplements with reminder times)');
      return;
    }

    // Schedule one notification per time group
    for (final entry in groups.entries) {
      final timeKey = entry.key; // HH:mm
      final items = entry.value;

      final parts = timeKey.split(':');
      final hour = int.parse(parts[0]);
      final minute = int.parse(parts[1]);

      final when = _nextInstanceOfTime(hour, minute);
      final id = 40000 + (hour * 60) + minute;

      final count = items.length;
      final title = count == 1
          ? 'Time for ${items.first.name}'
          : 'Time for $count supplements';

      // Build body that lists each supplement concisely
      final bodyLines = items.map((s) {
        final units = s.numberOfUnits;
        final unitType = s.unitType;
        final perUnit = s.ingredientsPerUnit;
        return '${s.name} — $units $unitType (${perUnit})';
      }).toList();
      final body = bodyLines.join('\n');

      printLog('📅 Scheduling group $timeKey (count=$count) id=$id');
      printLog('🕒 Now=${tz.TZDateTime.now(tz.local)} | When=$when');

      // Use BigTextStyle/InboxStyle for Android to show multiple lines
      final bool isSingle = count == 1;
      final String payloadStr = isSingle
          ? jsonEncode({"type": "single", "id": items.first.id})
          : jsonEncode({"type": "group", "time": timeKey});

      final androidDetails = AndroidNotificationDetails(
        _channelDailyId,
        _channelDailyName,
        channelDescription: _channelDailyDescription,
        importance: Importance.high,
        priority: Priority.high,
        styleInformation: BigTextStyleInformation(
          body,
          contentTitle: title,
          htmlFormatContentTitle: false,
        ),
        actions: [
          if (isSingle)
            AndroidNotificationAction(
              'take_single',
              'Take',
              showsUserInterface: true,
              cancelNotification: true,
            )
          else
            AndroidNotificationAction(
              'take_group',
              'Take All',
              showsUserInterface: true,
              cancelNotification: true,
            ),
        ],
      );

      final iosDetails = DarwinNotificationDetails(
        categoryIdentifier: isSingle ? 'single' : 'group',
      );

      await _plugin.zonedSchedule(
        id,
        title,
        isSingle ? body : 'Tap to see details',
        when,
        NotificationDetails(
          android: androidDetails,
          iOS: iosDetails,
        ),
        androidScheduleMode: AndroidScheduleMode.inexactAllowWhileIdle,
        matchDateTimeComponents: DateTimeComponents.time,
        payload: payloadStr,
      );

      printLog('✅ Scheduled group $timeKey with ID $id');
    }

    // Log what the system reports as pending
    try {
      final pending = await _plugin.pendingNotificationRequests();
      printLog('📋 Pending notifications after scheduling: ${pending.length}');
      for (final p in pending) {
        printLog('  - ID=${p.id}, Title=${p.title}, BodyLen=${p.body?.length ?? 0}');
      }
    } catch (e) {
      printLog('⚠️ Could not fetch pending notifications: $e');
    }
  }

  /// Convenience to schedule grouped reminders for today and tomorrow.
  ///
  /// For iOS’s 64 limit, we stick to one day for recurring (matchDateTimeComponents)
  /// which already repeats every day without needing to schedule future dates.
  /// If you want an extra safety net, you could schedule tomorrow’s one-offs,
  /// but with daily components this is unnecessary and risks hitting iOS limits.
  Future<void> scheduleDailyGroupedRemindersSafe(List<Supplement> supplements) async {
    // For now, just schedule today’s recurring groups.
    await scheduleDailyGroupedReminders(supplements);
  }

  /// Cancel all scheduled reminders for a given [supplementId].
  ///
  /// We assume up to 100 slots per supplement (00-99). This is simple and safe.
  Future<void> cancelSupplementReminders(int supplementId) async {
    if (!_initialized) {
      await initialize();
    }

    for (int i = 0; i < 100; i++) {
      await _plugin.cancel(supplementId * 100 + i);
    }
  }

  /// Cancel all scheduled notifications.
  Future<void> cancelAll() async {
    if (!_initialized) {
      await initialize();
    }
    await _plugin.cancelAll();
  }

  /// Show an immediate notification. Useful for quick diagnostics.
  Future<void> showInstant({
    required String title,
    required String body,
    String? payload,
  }) async {
    if (!_initialized) {
      await initialize();
    }

    await _plugin.show(
      DateTime.now().millisecondsSinceEpoch ~/ 1000,
      title,
      body,
      const NotificationDetails(
        android: AndroidNotificationDetails(
          'instant_notifications',
          'Instant Notifications',
          channelDescription: 'One-off or immediate notifications',
          importance: Importance.high,
          priority: Priority.high,
        ),
        iOS: DarwinNotificationDetails(),
      ),
      payload: payload,
    );
  }

  Future<NotificationAppLaunchDetails?> getLaunchDetails() async {
    if (!_initialized) {
      await initialize();
    }
    try {
      final details = await _plugin.getNotificationAppLaunchDetails();
      return details;
    } catch (e) {
      printLog('⚠️ getLaunchDetails error: $e');
      return null;
    }
  }

  /// Helper to compute the next instance of [hour]:[minute] in the local tz.
  tz.TZDateTime _nextInstanceOfTime(int hour, int minute) {
    final now = tz.TZDateTime.now(tz.local);
    var scheduled =
        tz.TZDateTime(tz.local, now.year, now.month, now.day, hour, minute);

    if (scheduled.isBefore(now)) {
      scheduled = scheduled.add(const Duration(days: 1));
      printLog('⏭ Scheduling for tomorrow at ${scheduled.toString()} (${scheduled.timeZoneName})');
    } else {
      printLog('⏲ Scheduling for today at ${scheduled.toString()} (${scheduled.timeZoneName})');
    }
    return scheduled;
  }

  /// Debug helper to fetch and log all pending notifications.
  Future<List<PendingNotificationRequest>> getPendingNotifications() async {
    if (!_initialized) {
      await initialize();
    }
    final list = await _plugin.pendingNotificationRequests();
    printLog('🧾 getPendingNotifications -> ${list.length} pending');
    for (final p in list) {
      printLog('  • ID=${p.id}, Title=${p.title}, Payload=${p.payload}');
    }
    return list;
  }
}