enum ErrorScope { local, global }
enum ErrorType  { network, auth, business, unknown }

class AppError {
  final String code;      // unique ID for deduplication
  final String message;   // user-facing text
  final ErrorScope scope; // local = inline UI, global = snackbar
  final ErrorType type;
}

class GlobalErrorCubit extends Cubit<AppError?> {
  final _seen = <String>{};

  GlobalErrorCubit() : super(null);

  void emitError(AppError error) {
    if (_seen.contains(error.code)) return; // deduplicate
    _seen.add(error.code);
    emit(error);
  }

  void clear() {
    _seen.clear();
    emit(null);
  }
}

class AuthInterceptor extends Interceptor {
  bool _isRefreshing = false;
  Completer<String?>? _refreshCompleter;

  @override
  Future<void> onError(DioException err, ErrorInterceptorHandler handler) async {
    if (err.response?.statusCode != 401) return handler.next(err);

    if (_isRefreshing) {
      // already refreshing — wait, then retry
      final newToken = await _refreshCompleter!.future;
      if (newToken != null) {
        err.requestOptions.headers['Authorization'] = 'Bearer $newToken';
        return handler.resolve(await _retry(err.requestOptions));
      }
      return handler.next(err);
    }

    _isRefreshing = true;
    _refreshCompleter = Completer<String?>();

    final newToken = await _doRefresh();
    _refreshCompleter!.complete(newToken);  // all waiters get the token
    _isRefreshing = false;
    _refreshCompleter = null;

    if (newToken != null) {
      err.requestOptions.headers['Authorization'] = 'Bearer $newToken';
      return handler.resolve(await _retry(err.requestOptions));
    }

    await sl<TokenManager>().clearTokens();
    handler.next(err);
  }
}

// In app.dart — wraps entire app. One listener, zero duplication.
BlocListener<GlobalErrorCubit, AppError?>(
  listener: (context, error) {
    if (error != null) {
      ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(content: Text(error.message)),
      );
      context.read<GlobalErrorCubit>().clear();
    }
  },
  child: child,
);