import 'dart:convert';
import 'package:workmanager/workmanager.dart';
import 'package:shared_preferences/shared_preferences.dart';
import 'package:odoo_rpc/odoo_rpc.dart';
import 'notification_service.dart';

// NOTE: This key tracks what IDs have been shown as device tray notifications.
// It is separate from 'last_seen_notification_id' (which tracks what the user READ in-app).
const String _kLastDeviceNotifiedId = 'last_device_notified_id';

@pragma('vm:entry-point')
void callbackDispatcher() {
  Workmanager().executeTask((task, inputData) async {
    try {
      final prefs = await SharedPreferences.getInstance();
      final url = prefs.getString('odoo_url');
      final sessionStr = prefs.getString('odoo_session');

      if (url == null || sessionStr == null) {
        return Future.value(true); // Not logged in, nothing to do
      }

      final lastDeviceNotifiedId = prefs.getInt(_kLastDeviceNotifiedId) ?? 0;

      final sessionArgs = json.decode(sessionStr);
      final session = OdooSession.fromJson(
          Map<String, dynamic>.from(sessionArgs as Map));
      final client = OdooClient(url, sessionId: session);

      final response = await client.callRPC(
        '/api/loyalty/fetch_notifications',
        'call',
        {'last_id': 0},
      );

      client.close();

      if (response != null && response['status'] == 'success') {
        final List<dynamic> notifications =
            List<dynamic>.from(response['data'] ?? []);

        // Filter to only truly new ones not yet shown on device tray
        final newNotifs = notifications
            .where((n) => (n['id'] as int? ?? 0) > lastDeviceNotifiedId)
            .toList();

        final notifService = NotificationService();
        await notifService.initialize();

        if (newNotifs.isNotEmpty) {
          int highestId = lastDeviceNotifiedId;
          for (final notif in newNotifs) {
            final int notifId = notif['id'] as int? ?? 0;
            if (notifId > highestId) highestId = notifId;

            await notifService.showNotification(
              id: notifId,
              title: notif['title'] as String? ?? 'Mie Mapan',
              body: notif['body'] as String? ?? '',
            );
          }

          await prefs.setInt(_kLastDeviceNotifiedId, highestId);
        }

        // Always compute badge count based on read_notification_ids
        final readIds = prefs.getStringList('read_notification_ids');
        if (readIds == null) {
          // Initialize read list with all currently fetched notifications on first install/run
          final initialRead = notifications.map((n) => (n['id'] as int? ?? 0).toString()).toList();
          await prefs.setStringList('read_notification_ids', initialRead);
          await notifService.setBadge(0);
        } else {
          final unreadCount = notifications
              .where((n) => !readIds.contains((n['id'] as int? ?? 0).toString()))
              .length;
          await notifService.setBadge(unreadCount);
        }
      }
    } catch (_) {
      // Silently swallow — background isolate must never crash
    }
    return Future.value(true);
  });
}