Flutter's official architecture: UI and data layers

// ══ 1. data/services/product_api_client.dart ══ (state saxlamır)
class ProductApiClient {
  ProductApiClient({required http.Client client}) : _client = client;
  final http.Client _client;

  Future<List<ProductDto>> getActiveProducts() async {
    final response = await _client.get(
      Uri.parse('https://api.example.com/v1/products?active=true'),
    );
    if (response.statusCode != 200) {
      throw HttpException('status ${response.statusCode}');
    }
    final list = jsonDecode(response.body)['data'] as List<dynamic>;
    return list
        .map((e) => ProductDto.fromJson(e as Map<String, dynamic>))
        .toList();
  }
}

// ══ 2. data/repositories/product_repository_remote.dart ══ (həqiqətin mənbəyi)
class ProductRepositoryRemote implements ProductRepository {
  ProductRepositoryRemote({required ProductApiClient apiClient})
      : _apiClient = apiClient;
  final ProductApiClient _apiClient;

  @override
  Future<List<Product>> fetchActive() async {
    final dtos = await _apiClient.getActiveProducts();
    return dtos.map((dto) => dto.toDomain()).toList();  // DTO → domain
  }
}

// ══ 3. presentation/products/product_list_notifier.dart ══ (view model)
part 'product_list_notifier.g.dart';

@riverpod
ProductApiClient productApiClient(Ref ref) =>
    ProductApiClient(client: http.Client());

@riverpod
ProductRepository productRepository(Ref ref) =>
    ProductRepositoryRemote(apiClient: ref.watch(productApiClientProvider));

@riverpod
class ProductList extends _$ProductList {
  @override
  Future<List<Product>> build() =>
      ref.watch(productRepositoryProvider).fetchActive();

  // "Command": view yalnız bunu çağırır, necə işlədiyini bilmir.
  Future<void> refresh() => ref.refresh(productListProvider.future);
}

// ══ 4. presentation/products/products_page.dart ══ (view)
class ProductsPage extends ConsumerWidget {
  const ProductsPage({super.key});

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

    // AsyncValue Riverpod 3-də sealed-dir: switch tam yoxlanılır.
    return switch (state) {
      AsyncData(:final value) => RefreshIndicator(
          onRefresh: () =>
              ref.read(productListProvider.notifier).refresh(),
          child: ListView.builder(
            itemCount: value.length,
            itemBuilder: (_, i) => ProductTile(product: value[i]),
          ),
        ),
      AsyncError(:final error) => ErrorView(error: error),
      _ => const Center(child: CircularProgressIndicator()),
    };
  }
}