/// Service locator for dependency injection.
/// 
/// Provides a centralized registry for all application services,
/// making it easy to access services throughout the app
/// and swap implementations for testing.
class ServiceLocator {
  /// Private constructor to prevent instantiation.
  ServiceLocator._();

  /// Singleton instance.
  static final ServiceLocator instance = ServiceLocator._();

  /// Local storage service.
  dynamic _localStorageService;

  /// Nostr service.
  dynamic _nostrService;

  /// Sync engine.
  dynamic _syncEngine;

  /// Firebase service.
  dynamic _firebaseService;

  /// Session service.
  dynamic _sessionService;

  /// Media service (Immich or Blossom).
  dynamic _mediaService;

  /// Recipe service.
  dynamic _recipeService;

  /// Theme notifier.
  dynamic _themeNotifier;

  /// Registers all services with the locator.
  /// 
  /// All services are optional and can be null if not configured.
  /// If a service is not provided, the existing value is preserved.
  void registerServices({
    dynamic localStorageService,
    dynamic nostrService,
    dynamic syncEngine,
    dynamic firebaseService,
    dynamic sessionService,
    dynamic mediaService,
    dynamic recipeService,
    dynamic themeNotifier,
  }) {
    if (localStorageService != null) _localStorageService = localStorageService;
    if (nostrService != null) _nostrService = nostrService;
    if (syncEngine != null) _syncEngine = syncEngine;
    if (firebaseService != null) _firebaseService = firebaseService;
    if (sessionService != null) _sessionService = sessionService;
    if (mediaService != null) _mediaService = mediaService;
    if (recipeService != null) _recipeService = recipeService;
    if (themeNotifier != null) _themeNotifier = themeNotifier;
  }

  /// Gets the local storage service.
  /// 
  /// Throws [StateError] if service is not registered.
  dynamic get localStorageService {
    if (_localStorageService == null) {
      throw StateError('LocalStorageService not registered');
    }
    return _localStorageService;
  }

  /// Gets the Nostr service (nullable).
  dynamic get nostrService => _nostrService;

  /// Gets the sync engine (nullable).
  dynamic get syncEngine => _syncEngine;

  /// Gets the Firebase service (nullable).
  dynamic get firebaseService => _firebaseService;

  /// Gets the session service (nullable).
  dynamic get sessionService => _sessionService;

  /// Gets the Media service (nullable) - Immich or Blossom.
  dynamic get mediaService => _mediaService;
  
  /// Gets the Immich service (nullable) - for backward compatibility.
  /// Returns null if Blossom is selected.
  dynamic get immichService {
    if (_mediaService != null && _mediaService.runtimeType.toString().contains('ImmichService')) {
      return _mediaService;
    }
    return null;
  }

  /// Gets the Recipe service (nullable).
  dynamic get recipeService => _recipeService;

  /// Gets the Theme notifier (nullable).
  dynamic get themeNotifier => _themeNotifier;

  /// Clears all registered services (useful for testing).
  void reset() {
    _localStorageService = null;
    _nostrService = null;
    _syncEngine = null;
    _firebaseService = null;
    _sessionService = null;
    _mediaService = null;
    _recipeService = null;
    _themeNotifier = null;
  }
}