import 'dart:async';
import 'dart:math';

import 'package:gps/utils/environment.dart';
import 'package:location/location.dart';
import 'package:wakelock/wakelock.dart';

class GpsUtils {
  _Stream s;

  GpsUtils()
      : s = Environment.hasRealGps
            ? _RealGpsStream()
            : _FakeGpsStream(49.4833, 8.4667, Duration(milliseconds: 100));

  Stream<LocationData> get stream => s.getStream();
}

mixin _Stream {
  Stream<LocationData> getStream();
}

class _RealGpsStream implements _Stream {
  // Really, really ugly
  // - Location package should have been encapsulated
  // - Permissions do not belong here
  Stream<LocationData> getStream() {
    final Location location = Location();

    location.serviceEnabled().then((_serviceEnabled) => {
          if (!_serviceEnabled) {location.requestService()}
        });
    location.hasPermission().then((_permissionGranted) => {
          if (_permissionGranted == PermissionStatus.denied)
            {location.requestPermission()}
        });
    location.changeSettings(
        accuracy: LocationAccuracy.high, interval: 100, distanceFilter: 0.0);
    Wakelock.enable();
    return location.onLocationChanged;
  }
}

class _FakeGpsStream implements _Stream {
  double lat;
  double lon;
  Duration dur;

  _FakeGpsStream(this.lat, this.lon, [this.dur = const Duration(seconds: 1)]);

  /// Generator which creates GPS coordinates around the given location.
  Stream<LocationData> getStream() async* {
    Map<String, dynamic> gpsPoint = {
      'accuracy': 20.0,
      'altitude': 100.0,
      'speed': 1.0,
      'speed_accuracy': 1.0,
      'isMock': 1,
      'verticalAccuracy': 20.0,
      'headingAccuracy': 1.0,
      'elapsedRealtimeNanos': 1000.0,
      'elapsedRealtimeUncertaintyNanos': 2000.0,
      'satelliteNumber': 0,
      'provider': "dummy"
    };

    double degree = 0.0;
    while (true) {
      await Future.delayed(dur);
      gpsPoint['time'] = DateTime.now().millisecondsSinceEpoch + 0.0;
      double rad = degree * pi / 180;
      gpsPoint['latitude'] = lat + cos(rad);
      gpsPoint['longitude'] = lon + sin(rad);
      gpsPoint['heading'] = degree;
      gpsPoint['altitude'] = degree;
      degree = (degree + 1) % 360;
      yield LocationData.fromMap(gpsPoint);
    }
  }
}