Live coding və code review ssenariləri

// 1) Model: mümkün olmayan vəziyyətlər ifadə edilə bilməz.
// AsyncValue loading/error/data-nı özü daşıyır, ona görə əlavə model lazım deyil.

// 2) State qatı.
class Articles extends AsyncNotifier<List<Article>> {
  @override
  Future<List<Article>> build() {
    return ref.watch(articleRepositoryProvider).fetchAll();
  }

  Future<void> refresh() async {
    state = const AsyncLoading<List<Article>>().copyWithPrevious(state);
    state = await AsyncValue.guard(
      () => ref.read(articleRepositoryProvider).fetchAll(),
    );
  }
}

final articlesProvider =
    AsyncNotifierProvider<Articles, List<Article>>(Articles.new);

// 3) UI: dörd hal — data, boş, xəta, ilk yükləmə.
class ArticlesPage extends ConsumerWidget {
  const ArticlesPage({super.key});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final articles = ref.watch(articlesProvider);

    return Scaffold(
      body: RefreshIndicator(
        onRefresh: () => ref.refresh(articlesProvider.future),
        child: switch (articles) {
          AsyncValue(:final value?) when value.isEmpty =>
            const EmptyView(message: 'Hələ məqalə yoxdur'),
          AsyncValue(:final value?) => ArticleListView(items: value),
          AsyncValue(:final error?) => ErrorView(
              message: '$error',
              onRetry: () => ref.invalidate(articlesProvider),
            ),
          _ => const ArticleSkeleton(),
        },
      ),
    );
  }
}

enum ArticlesStatus { initial, loading, success, failure }

final class ArticlesState extends Equatable {
  const ArticlesState({
    this.status = ArticlesStatus.initial,
    this.items = const [],
    this.error,
  });

  final ArticlesStatus status;
  final List<Article> items;
  final String? error;

  ArticlesState copyWith({
    ArticlesStatus? status,
    List<Article>? items,
    String? error,
  }) => ArticlesState(
        status: status ?? this.status,
        items: items ?? this.items,
        error: error,
      );

  @override
  List<Object?> get props => [status, items, error];
}

sealed class ArticlesEvent {}
final class ArticlesStarted extends ArticlesEvent {}
final class ArticlesRefreshRequested extends ArticlesEvent {}

class ArticlesBloc extends Bloc<ArticlesEvent, ArticlesState> {
  ArticlesBloc(this._repository) : super(const ArticlesState()) {
    on<ArticlesStarted>(_onLoad);
    // Təkrar sorğuların qarşısını alır.
    on<ArticlesRefreshRequested>(_onLoad, transformer: droppable());
  }

  final ArticleRepository _repository;

  Future<void> _onLoad(ArticlesEvent event, Emitter<ArticlesState> emit) async {
    emit(state.copyWith(status: ArticlesStatus.loading, error: null));
    try {
      final items = await _repository.fetchAll();
      emit(state.copyWith(status: ArticlesStatus.success, items: items));
    } catch (error) {
      // Köhnə items saxlanılır: ekran boşalmır.
      emit(state.copyWith(status: ArticlesStatus.failure, error: '$error'));
    }
  }
}