import 'package:equatable/equatable.dart';

/// Base failure type for the application.
///
/// Uses a sealed class hierarchy so `switch` expressions are exhaustive.
sealed class Failure extends Equatable {
  final String message;
  const Failure(this.message);

  @override
  List<Object?> get props => [message];
}

/// Returned when the backend API responds with a non-2xx status.
class ServerFailure extends Failure {
  final int? statusCode;
  const ServerFailure(super.message, {this.statusCode});

  @override
  List<Object?> get props => [message, statusCode];
}

/// Returned when the device has no network connectivity.
class NetworkFailure extends Failure {
  const NetworkFailure([super.message = 'No internet connection. Your changes are saved locally.']);
}

/// Returned when reading / writing the local cache fails.
class CacheFailure extends Failure {
  const CacheFailure([super.message = 'Could not access local storage.']);
}

/// Returned for authentication problems (expired token, bad credentials, etc.).
class AuthFailure extends Failure {
  const AuthFailure([super.message = 'Authentication failed. Please sign in again.']);
}

/// Returned when user input does not pass validation.
class ValidationFailure extends Failure {
  final Map<String, String> fieldErrors;
  const ValidationFailure(super.message, {this.fieldErrors = const {}});

  @override
  List<Object?> get props => [message, fieldErrors];
}