LocationService.kt

import android.annotation.SuppressLint
import android.content.Context
import android.os.Looper
import com.google.android.gms.location.LocationCallback
import com.google.android.gms.location.LocationRequest
import com.google.android.gms.location.LocationResult
import com.google.android.gms.location.LocationServices
import com.google.android.gms.maps.model.LatLng
import io.reactivex.BackpressureStrategy
import io.reactivex.Flowable
import io.reactivex.disposables.Disposables
import javax.inject.Inject
import javax.inject.Singleton

/**
 * Class that keeps track of all location updates while the Application is running.
 */
@SuppressLint("MissingPermission")
@Singleton
class LocationService @Inject constructor(private val context: Context) {

    val locationUpdateStream: Flowable<LocationPoint> = Flowable.create<LocationPoint>({ emitter ->
        val client = LocationServices.getFusedLocationProviderClient(context)
        val locationCallback = object : LocationCallback() {
            override fun onLocationResult(locationResult: LocationResult?) {
                locationResult?.lastLocation?.let { location ->
                    if (!emitter.isCancelled) {
                        emitter.onNext(LocationPoint(
                                location = LatLng(location.latitude, location.longitude),
                                time = location.time,
                                speed = location.speed.toDouble(),
                                accuracy = location.accuracy.toDouble()))
                    }
                }
            }
        }
        client.requestLocationUpdates(LocationRequest.create().apply {
            priority = LocationRequest.PRIORITY_HIGH_ACCURACY
            interval = 1000
            fastestInterval = 500
            smallestDisplacement = 1.0f
        }, locationCallback, Looper.getMainLooper())
        if (!emitter.isCancelled) {
            emitter.setDisposable(Disposables.fromAction {
                client.removeLocationUpdates(locationCallback)
            })
        }
    }, BackpressureStrategy.LATEST)
            .share()
}