package ai.beans.mapswidget.location

import android.annotation.SuppressLint
import android.content.Context
import android.location.Location
import android.os.Looper
import com.google.android.gms.location.FusedLocationProviderClient
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.location.Priority

/**
 * Optional Play Services location source for [BeansLocationBridge].
 *
 * Drop this file in alongside `BeansLocationBridge.kt` when your app already
 * depends on Play Services location:
 *
 * ```
 * implementation("com.google.android.gms:play-services-location:21.0.1")
 * ```
 *
 * The bridge finds it by name and uses it automatically — no wiring needed. To be
 * explicit (or to force the platform provider), pass it yourself:
 *
 * ```
 * BeansLocationBridge.attach(webView, this, BeansLocationBridge.Options(
 *   locationSource = BeansFusedLocationSource(this)      // or PlatformLocationSource(this)
 * ))
 * ```
 *
 * Why prefer it: fused fixes blend GPS, wifi, cell and sensors, so a resident
 * walking a property gets smoother positions and usable bearings, at lower battery
 * cost than raw GPS. Requires `play-services-location` 20.0.0+ for
 * `LocationRequest.Builder` / `Priority`.
 *
 * Permission is already checked by the bridge before [start] is called, hence the
 * `@SuppressLint("MissingPermission")`.
 */
class BeansFusedLocationSource(context: Context) : BeansLocationSource {

    override val name = "FusedLocationProvider"

    private val client: FusedLocationProviderClient =
        LocationServices.getFusedLocationProviderClient(context.applicationContext)

    private var listener: BeansLocationSource.Listener? = null
    private var callback: LocationCallback? = null

    /**
     * Fused has no device-wide "off" signal to test cheaply; it reports failure
     * through the callback instead. Returning true keeps the bridge from
     * pre-emptively erroring — a real outage surfaces as `onUnavailable`.
     */
    override fun isUsable(): Boolean = true

    @SuppressLint("MissingPermission")
    override fun start(config: BeansLocationConfig, listener: BeansLocationSource.Listener) {
        this.listener = listener

        val priority =
            if (config.highAccuracy) Priority.PRIORITY_HIGH_ACCURACY
            else Priority.PRIORITY_BALANCED_POWER_ACCURACY

        val request = LocationRequest.Builder(priority, config.minIntervalMs)
            .setMinUpdateIntervalMillis(config.minIntervalMs)
            .setMinUpdateDistanceMeters(config.minDistanceM)
            // false on purpose: waiting for an accurate first fix leaves the map
            // without a user marker for seconds. Deliver early and let it refine.
            .setWaitForAccurateLocation(false)
            .build()

        val cb = object : LocationCallback() {
            override fun onLocationResult(result: LocationResult) {
                result.lastLocation?.let { this@BeansFusedLocationSource.listener?.onLocation(it) }
            }

            override fun onLocationAvailability(
                availability: com.google.android.gms.location.LocationAvailability
            ) {
                if (!availability.isLocationAvailable) {
                    this@BeansFusedLocationSource.listener
                        ?.onUnavailable(2, "Fused location temporarily unavailable")
                }
            }
        }
        callback = cb

        client.requestLocationUpdates(request, cb, Looper.getMainLooper())

        // Seed the marker from the cached fix. Asynchronous, so it arrives through
        // the listener rather than through lastKnown().
        client.lastLocation.addOnSuccessListener { cached ->
            if (cached != null && callback === cb) {
                this.listener?.onLocation(cached)
            }
        }
    }

    override fun stop() {
        callback?.let { client.removeLocationUpdates(it) }
        callback = null
        listener = null
    }

    /** Fused's cache is only reachable asynchronously; [start] seeds it instead. */
    override fun lastKnown(): Location? = null
}