dart

import 'dart:async';
import 'dart:math';
import 'package:flutter/material.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';
import 'package:location/location.dart';
import 'package:flutter_local_notifications/flutter_local_notifications.dart';

class SimpleMap extends StatefulWidget {
  const SimpleMap({super.key});

  @override
  State<SimpleMap> createState() => _SimpleMapState();
}

class _SimpleMapState extends State<SimpleMap> {
  final LatLng destinationLocation = LatLng(-1.9501, 30.0589); // Example coordinates for KK 561 St
  final Completer<GoogleMapController> _controller = Completer();

  Set<Marker> _markers = {}; // Initialize an empty set of markers
  LatLng? currentLocation; // Assuming you have a way to get the current location
  Location location = Location();
  StreamSubscription<LocationData>? _locationSubscription;

  bool _notificationSentOutSide = false;
  bool _notificationSentInSide = false;

  FlutterLocalNotificationsPlugin flutterLocalNotificationsPlugin = FlutterLocalNotificationsPlugin();

  @override
  void initState() {
    super.initState();
    _initializeNotifications();
    getCurrentLocation();
  }

  void _initializeNotifications() {
    const AndroidInitializationSettings initializationSettingsAndroid =
        AndroidInitializationSettings('@mipmap/ic_launcher');

    final InitializationSettings initializationSettings = InitializationSettings(
      android: initializationSettingsAndroid,
    );

    flutterLocalNotificationsPlugin.initialize(initializationSettings);
  }

  void getCurrentLocation() async {
    currentLocation = await location.getLocation().then((value) {
      currentLocation = LatLng(value.latitude!, value.longitude!);
      addCurrentLocMarker(currentLocation!);
      return currentLocation;
    });

    _locationSubscription = location.onLocationChanged.listen((newLoc) {
      setState(() {
        currentLocation = LatLng(newLoc.latitude!, newLoc.longitude!);
        addCurrentLocMarker(currentLocation!);
        _checkGeofenceStatus(newLoc.latitude!, newLoc.longitude!);
      });
    });
  }

  void addCurrentLocMarker(LatLng location) {
    Marker currentLocMarker = Marker(
      markerId: MarkerId('currentLocation'),
      icon: BitmapDescriptor.defaultMarker,
      position: location,
      infoWindow: InfoWindow(title: 'Current Location', snippet: 'You are here'),
    );
    setState(() {
      _markers.add(currentLocMarker);
    });
  }

  void addDestinationMarker() {
    Marker destinationMarker = Marker(
      markerId: MarkerId('destinationLocation'),
      icon: BitmapDescriptor.defaultMarkerWithHue(BitmapDescriptor.hueBlue),
      position: destinationLocation,
      infoWindow: InfoWindow(title: 'Destination Location', snippet: 'Destination location...'),
    );
    setState(() {
      _markers.add(destinationMarker);
    });
  }

  void _checkGeofenceStatus(double latitude, double longitude) {
    bool insideGeofence = _isLocationInsideGeofence(latitude, longitude);

    if (insideGeofence && !_notificationSentInSide) {
      _triggerInSideNotification();
      _notificationSentInSide = true;
      _notificationSentOutSide = false;
    } else if (!insideGeofence && !_notificationSentOutSide) {
      _triggerOutSideNotification();
      _notificationSentOutSide = true;
      _notificationSentInSide = false;
    }
  }

  bool _isLocationInsideGeofence(double latitude, double longitude) {
    // Define your geofence boundaries, for example, a 500m radius around the destination
    double radiusInMeters = 500.0;
    double distance = _calculateDistance(latitude, longitude, destinationLocation.latitude, destinationLocation.longitude);
    return distance <= radiusInMeters;
  }

  double _calculateDistance(double lat1, double lon1, double lat2, double lon2) {
    const double p = 0.017453292519943295; // PI / 180
    final double a = 0.5 -
        cos((lat2 - lat1) * p) / 2 +
        cos(lat1 * p) * cos(lat2 * p) *
        (1 - cos((lon2 - lon1) * p)) / 2;
    return 12742 * asin(sqrt(a)) * 1000; // 2 * R; R = 6371 km
  }

  Future<void> _triggerInSideNotification() async {
    const AndroidNotificationDetails androidPlatformChannelSpecifics =
        AndroidNotificationDetails(
      'geo_fence_channel',
      'Geofence Notifications',
      importance: Importance.max,
      priority: Priority.high,
    );
    const NotificationDetails platformChannelSpecifics =
        NotificationDetails(android: androidPlatformChannelSpecifics);
    await flutterLocalNotificationsPlugin.show(
      0,
      'Inside Geofence',
      'You are inside the geofence area.',
      platformChannelSpecifics,
    );
    print('Inside geofence notification sent');
  }

  Future<void> _triggerOutSideNotification() async {
    const AndroidNotificationDetails androidPlatformChannelSpecifics =
        AndroidNotificationDetails(
      'geo_fence_channel',
      'Geofence Notifications',
      importance: Importance.max,
      priority: Priority.high,
    );
    const NotificationDetails platformChannelSpecifics =
        NotificationDetails(android: androidPlatformChannelSpecifics);
    await flutterLocalNotificationsPlugin.show(
      0,
      'Outside Geofence',
      'You are outside the geofence area.',
      platformChannelSpecifics,
    );
    print('Outside geofence notification sent');
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text("Simple Google Map"),
        centerTitle: true,
      ),
      body: GoogleMap(
        initialCameraPosition: CameraPosition(
          target: currentLocation ?? destinationLocation,
          zoom: 13,
        ),
        markers: _markers,
        onMapCreated: (GoogleMapController controller) {
          _controller.complete(controller);
          addDestinationMarker();
        },
      ),
    );
  }

  @override
  void dispose() {
    _locationSubscription?.cancel();
    super.dispose();
  }
}