# Warehouse Feature

Complete implementation of the warehouse feature following **Clean Architecture** principles.

## Architecture Overview

This feature follows a three-layer clean architecture pattern:

```
Presentation Layer (UI)
    ↓ (uses)
Domain Layer (Business Logic)
    ↓ (uses)
Data Layer (API & Data Sources)
```

### Key Principles

- **Separation of Concerns**: Each layer has a single responsibility
- **Dependency Inversion**: Outer layers depend on inner layers, not vice versa
- **Testability**: Each layer can be tested independently
- **Maintainability**: Changes in one layer don't affect others

## Project Structure

```
lib/features/warehouse/
├── data/
│   ├── datasources/
│   │   └── warehouse_remote_datasource.dart    # API calls using ApiClient
│   ├── models/
│   │   └── warehouse_model.dart                # Data transfer objects with JSON serialization
│   └── repositories/
│       └── warehouse_repository_impl.dart      # Repository implementation
├── domain/
│   ├── entities/
│   │   └── warehouse_entity.dart               # Pure business models
│   ├── repositories/
│   │   └── warehouse_repository.dart           # Repository interface/contract
│   └── usecases/
│       └── get_warehouses_usecase.dart         # Business logic use cases
├── presentation/
│   ├── pages/
│   │   └── warehouse_selection_page.dart       # Main warehouse selection screen
│   ├── providers/
│   │   └── warehouse_provider.dart             # Riverpod state management
│   └── widgets/
│       └── warehouse_card.dart                 # Reusable warehouse card widget
├── warehouse_exports.dart                       # Barrel file for clean imports
├── warehouse_provider_setup_example.dart        # Provider setup guide
└── README.md                                    # This file
```

## Layer Details

### 1. Domain Layer (Core Business Logic)

The innermost layer that contains business entities, repository interfaces, and use cases. **No dependencies on external frameworks or packages** (except dartz for Either).

#### Entities

`domain/entities/warehouse_entity.dart`

- Pure Dart class representing a warehouse
- No JSON serialization logic
- Contains business rules and validations
- Extends Equatable for value comparison

```dart
class WarehouseEntity extends Equatable {
  final int id;
  final String name;
  final String code;
  final String? description;
  final bool isNGWareHouse;
  final int totalCount;

  bool get hasItems => totalCount > 0;
  bool get isNGType => isNGWareHouse;
}
```

#### Repository Interface

`domain/repositories/warehouse_repository.dart`

- Abstract interface defining data operations
- Returns `Either<Failure, T>` for error handling
- Implementation is provided by the data layer

```dart
abstract class WarehouseRepository {
  Future<Either<Failure, List<WarehouseEntity>>> getWarehouses();
}
```

#### Use Cases

`domain/usecases/get_warehouses_usecase.dart`

- Single responsibility: fetch warehouses
- Encapsulates business logic
- Depends only on repository interface

```dart
class GetWarehousesUseCase {
  final WarehouseRepository repository;

  Future<Either<Failure, List<WarehouseEntity>>> call() async {
    return await repository.getWarehouses();
  }
}
```

### 2. Data Layer (External Data Management)

Handles all data operations including API calls, JSON serialization, and error handling.

#### Models

`data/models/warehouse_model.dart`

- Extends domain entity
- Adds JSON serialization (`fromJson`, `toJson`)
- Maps API response format to domain entities
- Matches API field naming (PascalCase)

```dart
class WarehouseModel extends WarehouseEntity {
  factory WarehouseModel.fromJson(Map<String, dynamic> json) {
    return WarehouseModel(
      id: json['Id'] ?? 0,
      name: json['Name'] ?? '',
      code: json['Code'] ?? '',
      description: json['Description'],
      isNGWareHouse: json['IsNGWareHouse'] ?? false,
      totalCount: json['TotalCount'] ?? 0,
    );
  }
}
```

#### Data Sources

`data/datasources/warehouse_remote_datasource.dart`

- Interface + implementation pattern
- Makes API calls using `ApiClient`
- Parses `ApiResponse` wrapper
- Throws typed exceptions (`ServerException`, `NetworkException`)

```dart
class WarehouseRemoteDataSourceImpl implements WarehouseRemoteDataSource {
  Future<List<WarehouseModel>> getWarehouses() async {
    final response = await apiClient.get('/warehouses');
    final apiResponse = ApiResponse.fromJson(
      response.data,
      (json) => (json as List).map((e) => WarehouseModel.fromJson(e)).toList(),
    );

    if (apiResponse.isSuccess && apiResponse.value != null) {
      return apiResponse.value!;
    } else {
      throw ServerException(apiResponse.errors.first);
    }
  }
}
```

#### Repository Implementation

`data/repositories/warehouse_repository_impl.dart`

- Implements domain repository interface
- Coordinates data sources
- Converts exceptions to failures
- Maps models to entities

```dart
class WarehouseRepositoryImpl implements WarehouseRepository {
  @override
  Future<Either<Failure, List<WarehouseEntity>>> getWarehouses() async {
    try {
      final warehouses = await remoteDataSource.getWarehouses();
      final entities = warehouses.map((model) => model.toEntity()).toList();
      return Right(entities);
    } on ServerException catch (e) {
      return Left(ServerFailure(e.message));
    } on NetworkException catch (e) {
      return Left(NetworkFailure(e.message));
    }
  }
}
```

### 3. Presentation Layer (UI & State Management)

Handles UI rendering, user interactions, and state management using Riverpod.

#### State Management

`presentation/providers/warehouse_provider.dart`

- `WarehouseState`: Immutable state class
  - `warehouses`: List of warehouses
  - `selectedWarehouse`: Currently selected warehouse
  - `isLoading`: Loading indicator
  - `error`: Error message

- `WarehouseNotifier`: StateNotifier managing state
  - `loadWarehouses()`: Fetch warehouses from API
  - `selectWarehouse()`: Select a warehouse
  - `refresh()`: Reload warehouses
  - `clearError()`: Clear error state

```dart
class WarehouseState {
  final List<WarehouseEntity> warehouses;
  final WarehouseEntity? selectedWarehouse;
  final bool isLoading;
  final String? error;
}

class WarehouseNotifier extends StateNotifier<WarehouseState> {
  Future<void> loadWarehouses() async {
    state = state.setLoading();
    final result = await getWarehousesUseCase();
    result.fold(
      (failure) => state = state.setError(failure.message),
      (warehouses) => state = state.setSuccess(warehouses),
    );
  }
}
```

#### Pages

`presentation/pages/warehouse_selection_page.dart`

- ConsumerStatefulWidget using Riverpod
- Loads warehouses on initialization
- Displays different UI states:
  - Loading: CircularProgressIndicator
  - Error: Error message with retry button
  - Empty: No warehouses message
  - Success: List of warehouse cards
- Pull-to-refresh support
- Navigation to operations page on selection

#### Widgets

`presentation/widgets/warehouse_card.dart`

- Reusable warehouse card component
- Displays:
  - Warehouse name (title)
  - Code (with QR icon)
  - Total items count (with inventory icon)
  - Description (if available)
  - NG warehouse badge (if applicable)
- Material Design 3 styling
- Tap to select functionality

## API Integration

### Endpoint

```
GET /warehouses
```

### Request

```bash
curl -X GET https://api.example.com/warehouses \
  -H "Authorization: Bearer {access_token}"
```

### Response Format

```json
{
  "Value": [
    {
      "Id": 1,
      "Name": "Kho nguyên vật liệu",
      "Code": "001",
      "Description": "Kho chứa nguyên vật liệu",
      "IsNGWareHouse": false,
      "TotalCount": 8
    },
    {
      "Id": 2,
      "Name": "Kho bán thành phẩm công đoạn",
      "Code": "002",
      "Description": null,
      "IsNGWareHouse": false,
      "TotalCount": 12
    }
  ],
  "IsSuccess": true,
  "IsFailure": false,
  "Errors": [],
  "ErrorCodes": []
}
```

## Setup & Integration

### 1. Install Dependencies

Ensure your `pubspec.yaml` includes:

```yaml
dependencies:
  flutter_riverpod: ^2.4.9
  dio: ^5.3.2
  dartz: ^0.10.1
  equatable: ^2.0.5
  flutter_secure_storage: ^9.0.0
```

### 2. Set Up Providers

Create or update your provider configuration file (e.g., `lib/core/di/providers.dart`):

```dart
import 'package:flutter_riverpod/flutter_riverpod.dart';
import '../features/warehouse/warehouse_exports.dart';

// Core providers (if not already set up)
final secureStorageProvider = Provider<SecureStorage>((ref) {
  return SecureStorage();
});

final apiClientProvider = Provider<ApiClient>((ref) {
  final secureStorage = ref.watch(secureStorageProvider);
  return ApiClient(secureStorage);
});

// Warehouse data layer providers
final warehouseRemoteDataSourceProvider = Provider<WarehouseRemoteDataSource>((ref) {
  final apiClient = ref.watch(apiClientProvider);
  return WarehouseRemoteDataSourceImpl(apiClient);
});

final warehouseRepositoryProvider = Provider((ref) {
  final remoteDataSource = ref.watch(warehouseRemoteDataSourceProvider);
  return WarehouseRepositoryImpl(remoteDataSource);
});

// Warehouse domain layer providers
final getWarehousesUseCaseProvider = Provider((ref) {
  final repository = ref.watch(warehouseRepositoryProvider);
  return GetWarehousesUseCase(repository);
});

// Warehouse presentation layer providers
final warehouseProvider = StateNotifierProvider<WarehouseNotifier, WarehouseState>((ref) {
  final getWarehousesUseCase = ref.watch(getWarehousesUseCaseProvider);
  return WarehouseNotifier(getWarehousesUseCase);
});
```

### 3. Update WarehouseSelectionPage

Replace the TODO comments in `warehouse_selection_page.dart`:

```dart
@override
void initState() {
  super.initState();
  WidgetsBinding.instance.addPostFrameCallback((_) {
    ref.read(warehouseProvider.notifier).loadWarehouses();
  });
}

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

  // Rest of the implementation...
}
```

### 4. Add to Router

Using go_router:

```dart
GoRoute(
  path: '/warehouses',
  name: 'warehouses',
  builder: (context, state) => const WarehouseSelectionPage(),
),
GoRoute(
  path: '/operations',
  name: 'operations',
  builder: (context, state) {
    final warehouse = state.extra as WarehouseEntity;
    return OperationSelectionPage(warehouse: warehouse);
  },
),
```

### 5. Navigate to Warehouse Page

```dart
// From login page after successful authentication
context.go('/warehouses');

// Or using Navigator
Navigator.of(context).pushNamed('/warehouses');
```

## Usage Examples

### Loading Warehouses

```dart
// In a widget
ElevatedButton(
  onPressed: () {
    ref.read(warehouseProvider.notifier).loadWarehouses();
  },
  child: const Text('Load Warehouses'),
)
```

### Watching State

```dart
// In a ConsumerWidget
@override
Widget build(BuildContext context, WidgetRef ref) {
  final state = ref.watch(warehouseProvider);

  if (state.isLoading) {
    return const CircularProgressIndicator();
  }

  if (state.error != null) {
    return Text('Error: ${state.error}');
  }

  return ListView.builder(
    itemCount: state.warehouses.length,
    itemBuilder: (context, index) {
      final warehouse = state.warehouses[index];
      return ListTile(title: Text(warehouse.name));
    },
  );
}
```

### Selecting a Warehouse

```dart
// Select warehouse and navigate
void onWarehouseTap(WarehouseEntity warehouse) {
  ref.read(warehouseProvider.notifier).selectWarehouse(warehouse);
  context.push('/operations', extra: warehouse);
}
```

### Pull to Refresh

```dart
RefreshIndicator(
  onRefresh: () => ref.read(warehouseProvider.notifier).refresh(),
  child: ListView(...),
)
```

### Accessing Selected Warehouse

```dart
// In another page
final state = ref.watch(warehouseProvider);
final selectedWarehouse = state.selectedWarehouse;

if (selectedWarehouse != null) {
  Text('Current: ${selectedWarehouse.name}');
}
```

## Error Handling

The feature uses dartz's `Either` type for functional error handling:

```dart
// In use case or repository
Future<Either<Failure, List<WarehouseEntity>>> getWarehouses() async {
  try {
    final warehouses = await remoteDataSource.getWarehouses();
    return Right(warehouses); // Success
  } on ServerException catch (e) {
    return Left(ServerFailure(e.message)); // Failure
  }
}

// In presentation layer
result.fold(
  (failure) => print('Error: ${failure.message}'),
  (warehouses) => print('Success: ${warehouses.length} items'),
);
```

### Failure Types

- `ServerFailure`: API errors, HTTP errors
- `NetworkFailure`: Connection issues, timeouts
- `CacheFailure`: Local storage errors (if implemented)

## Testing

### Unit Tests

**Test Use Case:**
```dart
test('should get warehouses from repository', () async {
  // Arrange
  when(mockRepository.getWarehouses())
      .thenAnswer((_) async => Right(mockWarehouses));

  // Act
  final result = await useCase();

  // Assert
  expect(result, Right(mockWarehouses));
  verify(mockRepository.getWarehouses());
});
```

**Test Repository:**
```dart
test('should return warehouses when remote call is successful', () async {
  // Arrange
  when(mockRemoteDataSource.getWarehouses())
      .thenAnswer((_) async => mockWarehouseModels);

  // Act
  final result = await repository.getWarehouses();

  // Assert
  expect(result.isRight(), true);
});
```

**Test Notifier:**
```dart
test('should emit loading then success when warehouses are loaded', () async {
  // Arrange
  when(mockUseCase()).thenAnswer((_) async => Right(mockWarehouses));

  // Act
  await notifier.loadWarehouses();

  // Assert
  expect(notifier.state.isLoading, false);
  expect(notifier.state.warehouses, mockWarehouses);
});
```

### Widget Tests

```dart
testWidgets('should display warehouse list when loaded', (tester) async {
  // Arrange
  final container = ProviderContainer(
    overrides: [
      warehouseProvider.overrideWith((ref) => MockWarehouseNotifier()),
    ],
  );

  // Act
  await tester.pumpWidget(
    UncontrolledProviderScope(
      container: container,
      child: const WarehouseSelectionPage(),
    ),
  );

  // Assert
  expect(find.byType(WarehouseCard), findsWidgets);
});
```

## Best Practices

1. **Always use Either for error handling** - Don't throw exceptions across layers
2. **Keep domain layer pure** - No Flutter/external dependencies
3. **Use value objects** - Entities should be immutable
4. **Single responsibility** - Each class has one reason to change
5. **Dependency inversion** - Depend on abstractions, not concretions
6. **Test each layer independently** - Use mocks and test doubles

## Common Issues

### Provider Not Found

**Error:** `ProviderNotFoundException`

**Solution:** Make sure you've set up all providers in your provider configuration file and wrapped your app with `ProviderScope`.

### Null Safety Issues

**Error:** `Null check operator used on a null value`

**Solution:** Always check for null before accessing optional fields:
```dart
if (warehouse.description != null) {
  Text(warehouse.description!);
}
```

### API Response Format Mismatch

**Error:** `ServerException: Invalid response format`

**Solution:** Verify that the API response matches the expected format in `ApiResponse.fromJson` and `WarehouseModel.fromJson`.

## Future Enhancements

- [ ] Add caching with Hive for offline support
- [ ] Implement warehouse search functionality
- [ ] Add warehouse filtering (by type, name, etc.)
- [ ] Add pagination for large warehouse lists
- [ ] Implement warehouse CRUD operations
- [ ] Add warehouse analytics and statistics

## Related Features

- **Authentication**: `/lib/features/auth/` - User login and token management
- **Operations**: `/lib/features/operation/` - Import/Export selection
- **Products**: `/lib/features/products/` - Product listing per warehouse

## References

- [Clean Architecture by Uncle Bob](https://blog.cleancoder.com/uncle-bob/2012/08/13/the-clean-architecture.html)
- [Flutter Riverpod Documentation](https://riverpod.dev/)
- [Dartz Package for Functional Programming](https://pub.dev/packages/dartz)
- [Material Design 3](https://m3.material.io/)

---

**Last Updated:** 2025-10-27
**Version:** 1.0.0
**Author:** Claude Code