import 'dart:async';
import 'dart:math' as math;
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:sensors_plus/sensors_plus.dart';

final compassServiceProvider = Provider<CompassService>((ref) {
  return CompassService();
});

final headingStreamProvider = StreamProvider<double>((ref) {
  return ref.watch(compassServiceProvider).headingStream;
});

class CompassService {
  final _headingController = StreamController<double>.broadcast();
  StreamSubscription? _magSub;

  Stream<double> get headingStream => _headingController.stream;

  CompassService() {
    _startSensors();
  }

  void _startSensors() {
    _magSub = magnetometerEventStream(samplingPeriod: const Duration(milliseconds: 200)).listen((MagnetometerEvent event) {
      // Calculate heading from magnetometer (X and Y components).
      // Note: For a phone mounted vertically on a motorcycle, the axes might need mapping.
      // This calculates basic 2D heading assuming phone is flat. 
      // Full tilt-compensated compass requires accelerometer fusion.
      
      double heading = math.atan2(event.y, event.x) * (180.0 / math.pi);
      
      // Adjust to 0-360 degrees
      if (heading < 0) {
        heading += 360;
      }
      
      _headingController.add(heading);
    });
  }

  String getHeadingString(double heading) {
    const directions = ['N', 'NE', 'E', 'SE', 'S', 'SW', 'W', 'NW'];
    final index = ((heading + 22.5) % 360 / 45).floor();
    return directions[index];
  }

  void dispose() {
    _magSub?.cancel();
    _headingController.close();
  }
}