import Foundation

#if os(iOS)
import CoreLocation
#endif

final class LocationService: NSObject {
    typealias LocationResult = Result<(Double, Double), LocationError>

#if os(iOS)
    enum LocationError: Error {
        case servicesDisabled
        case denied
        case unavailable
    }
#else
    enum LocationError: Error {
        case denied
        case unavailable
    }
#endif

#if os(iOS)
    private let manager = CLLocationManager()
    private var completion: ((LocationResult) -> Void)?
#endif

    override init() {
        super.init()
#if os(iOS)
        manager.delegate = self
        manager.desiredAccuracy = kCLLocationAccuracyHundredMeters
#endif
    }

    func requestLocation(_ completion: @escaping (LocationResult) -> Void) {
#if os(iOS)
        guard CLLocationManager.locationServicesEnabled() else {
            completion(.failure(.servicesDisabled))
            return
        }
        self.completion = completion
        manager.requestWhenInUseAuthorization()
        manager.requestLocation()
#else
        let defaults = UserDefaults.standard
        if defaults.bool(forKey: "location_permission_denied") {
            completion(.failure(.denied))
            return
        }

        guard let latRaw = defaults.string(forKey: "last_location_lat"),
              let lngRaw = defaults.string(forKey: "last_location_lng"),
              let lat = Double(latRaw),
              let lng = Double(lngRaw) else {
            completion(.failure(.unavailable))
            return
        }
        completion(.success((lat, lng)))
#endif
    }
}

#if os(iOS)
extension LocationService: CLLocationManagerDelegate {
    func locationManagerDidChangeAuthorization(_ manager: CLLocationManager) {
        let status = manager.authorizationStatus
        if status == .denied || status == .restricted {
            completion?(.failure(.denied))
            completion = nil
        }
    }

    func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
        guard let location = locations.first else { return }
        completion?(.success((location.coordinate.latitude, location.coordinate.longitude)))
        completion = nil
    }

    func locationManager(_ manager: CLLocationManager, didFailWithError error: Error) {
        completion?(.failure(.unavailable))
        completion = nil
    }
}
#endif