import 'dart:developer' as developer;
import 'dart:io';
import 'dart:math';

import 'package:flutter_background_geolocation/flutter_background_geolocation.dart' as bg;
import 'package:traccar_client/location_cache.dart';
import 'package:traccar_client/preferences.dart';
import 'package:wakelock_partial_android/wakelock_partial_android.dart';

class GeolocationService {
  static Future<void> init() async {
    await bg.BackgroundGeolocation.ready(Preferences.geolocationConfig());
    if (Platform.isAndroid) {
      await bg.BackgroundGeolocation.registerHeadlessTask(headlessTask);
    }
    bg.BackgroundGeolocation.onEnabledChange(onEnabledChange);
    bg.BackgroundGeolocation.onMotionChange(onMotionChange);
    bg.BackgroundGeolocation.onLocation(onLocation);
    bg.BackgroundGeolocation.onHeartbeat(onHeartbeat);
  }

  static Future<void> onEnabledChange(bool enabled) async {
    if (Preferences.instance.getBool(Preferences.wakelock) ?? false) {
      if (!enabled) {
        await WakelockPartialAndroid.release();
      }
    }
  }

  static Future<void> onMotionChange(bg.Location location) async {
    if (Preferences.instance.getBool(Preferences.wakelock) ?? false) {
      if (location.isMoving) {
        await WakelockPartialAndroid.acquire();
      } else {
        await WakelockPartialAndroid.release();
      }
    }
  }

  static Future<void> onLocation(bg.Location location) async {
    if (_shouldDelete(location)) {
      await bg.BackgroundGeolocation.destroyLocation(location.uuid);
    } else {
      LocationCache.set(location);
      try {
        await bg.BackgroundGeolocation.sync();
      } catch (error) {
        developer.log('Failed to send location', error: error);
      }
    }
  }

  static Future<void> onHeartbeat(bg.HeartbeatEvent event) async {
    await bg.BackgroundGeolocation.getCurrentPosition(samples: 1, persist: true, extras: {'heartbeat': true});
  }

  static bool _shouldDelete(bg.Location location) {
    if (!location.isMoving) return false;
    if (location.extras?.isNotEmpty == true) return false;

    final lastLocation = LocationCache.get();
    if (lastLocation == null) return false;

    final duration = DateTime.parse(location.timestamp).difference(DateTime.parse(lastLocation.timestamp)).inSeconds;

    final fastestInterval = Preferences.instance.getInt(Preferences.fastestInterval);
    if (fastestInterval != null && duration < fastestInterval) return true;

    final distance = _distance(lastLocation, location);

    final distanceFilter = Preferences.instance.getInt(Preferences.distance) ?? 0;
    if (distanceFilter > 0 && distance >= distanceFilter) return false;

    final isHighestAccuracy = Preferences.instance.getString(Preferences.accuracy) == 'highest';

    if (distanceFilter == 0 || isHighestAccuracy) {
      final intervalFilter = Preferences.instance.getInt(Preferences.interval) ?? 0;
      if (intervalFilter > 0 && duration >= intervalFilter) return false;
    }

    if (isHighestAccuracy && lastLocation.heading >= 0 && location.coords.heading > 0) {
      final angle = (location.coords.heading - lastLocation.heading).abs();
      final angleFilter = Preferences.instance.getInt(Preferences.angle) ?? 0;
      if (angleFilter > 0 && angle >= angleFilter) return false;
    }

    return true;
  }

  static double _distance(Location from, bg.Location to) {
    const earthRadius = 6371000; // meters
    final dLat = _degToRad(to.coords.latitude - from.latitude);
    final dLon = _degToRad(to.coords.longitude - from.longitude);
    final a = sin(dLat / 2) * sin(dLat / 2) +
        cos(_degToRad(from.latitude)) * cos(_degToRad(to.coords.latitude)) * sin(dLon / 2) * sin(dLon / 2);
    final c = 2 * atan2(sqrt(a), sqrt(1 - a));
    return earthRadius * c;
  }

  static double _degToRad(double degree) => degree * pi / 180.0;
}

@pragma('vm:entry-point')
void headlessTask(bg.HeadlessEvent headlessEvent) async {
  await Preferences.init();
  switch (headlessEvent.name) {
    case bg.Event.ENABLEDCHANGE:
      await GeolocationService.onEnabledChange(headlessEvent.event);
      break;
    case bg.Event.MOTIONCHANGE:
      await GeolocationService.onMotionChange(headlessEvent.event);
      break;
    case bg.Event.LOCATION:
      await GeolocationService.onLocation(headlessEvent.event);
      break;
    case bg.Event.HEARTBEAT:
      await GeolocationService.onHeartbeat(headlessEvent.event);
      break;
  }
}