# Coding Conventions

**Analysis Date:** 2026-03-30

## Naming Patterns

**Files:**
- Dart: lowercase with underscores (`arc.dart`, `arc_platform_interface.dart`, `arc_method_channel.dart`)
- Java: PascalCase matching class name (`ArcPlugin.java`, `FaceEngineManager.java`)

**Classes:**
- PascalCase: `Arc`, `ArcPlatform`, `MethodChannelArc`, `FaceEngineManager`, `FaceErrorCode`

**Methods/Functions:**
- camelCase: `getPlatformVersion`, `activeOnline`, `detectFaces`, `extractFaceFeature`

**Variables:**
- Private Dart members: underscore prefix (`_token`, `_instance`, `_isDetecting`)
- Java: `private` keyword with camelCase: `faceEngine`, `isInitialized`, `lastRgbLiveness`

**Constants:**
- Dart: `static final` with underscore for private: `static final Object _token = Object();`
- Java enum: uppercase with underscores: `MOK`, `MERR_UNKNOWN`, `ENGINE_NOT_INITIALIZED`

## Code Style

**Formatting:**
- Dart: `flutter_lints ^5.0.0` via `analysis_options.yaml`
- Config: `include: package:flutter_lints/flutter.yaml`
- Java: Standard Android/Java conventions

**Linting:**
- Dart: flutter_lints package rules
- Java: No explicit linting config detected

## Import Organization

**Dart Order:**
1. SDK imports (`dart:typed_data`)
2. Package imports (`package:plugin_platform_interface/plugin_platform_interface.dart`)
3. Relative imports (`arc_method_channel.dart`)

**Example:**
```dart
import 'dart:typed_data';

import 'package:plugin_platform_interface/plugin_platform_interface.dart';

import 'arc_method_channel.dart';
```

**Java Order:**
1. Package declaration
2. Android SDK imports
3. Third-party imports
4. JUnit/Mockito imports (in tests)

## Error Handling

**Dart Patterns:**
- Platform interface throws `UnimplementedError` for abstract methods:
```dart
Future<String?> getPlatformVersion() {
  throw UnimplementedError('platformVersion() has not been implemented.');
}
```
- Method channel calls wrapped in try-catch with `PlatformException`
- Return `Map<String, dynamic>?` with `success`, `errorCode`, `message` keys

**Java Patterns:**
- Parameter validation before processing
- Error codes via `FaceErrorCode` enum
- Result Map with consistent keys: `success`, `errorCode`, `message`
- Logging with `android.util.Log.e()` for errors

**Return Format:**
All API methods return consistent Map structure:
```dart
{
  'success': bool,      // Operation success status
  'errorCode': int,     // Error code (0 = success)
  'message': String,    // Error/success message
  // Additional data keys based on method
}
```

## Documentation

**Dart Comments:**
- Triple-slash `///` for method documentation
- Chinese descriptions required
- Parameter documentation: `[paramName] description`
- Return documentation after parameters

**Example:**
```dart
/// 激活 SDK（在线激活）
/// [appId] 应用 ID（从虹软控制台获取）
/// [sdkKey] SDK 密钥（从虹软控制台获取）
/// [activeKey] 激活密钥
/// 返回包含 success, errorCode, message 的 Map
Future<Map<String, dynamic>?> activeOnline({
  required String appId,
  required String sdkKey,
  required String activeKey,
})
```

**Java Comments:**
- Javadoc `/** */` format
- `@param` and `@return` tags
- Chinese descriptions

**Example:**
```java
/**
 * 激活 SDK（在线激活方式）
 * @param context Android 上下文
 * @param appId 应用 ID（从虹软控制台获取）
 * @param sdkKey SDK 密钥（从虹软控制台获取）
 * @param activeKey 激活密钥
 * @return 错误码（0 表示成功）
 */
public int activeOnline(Context context, String appId, String sdkKey, String activeKey)
```

## Logging

**Dart:**
- `debugPrint()` for development logging
- Located in: `example/lib/main.dart`

**Java:**
- `android.util.Log.i()` for info
- `android.util.Log.e()` for errors
- `android.util.Log.w()` for warnings
- Tag: `"FaceEngineManager"`

**Example:**
```java
android.util.Log.i("FaceEngineManager", "引擎初始化成功！");
android.util.Log.e("FaceEngineManager", "引擎初始化失败，错误码: " + result);
```

## Function Design

**Parameters:**
- Dart: Named parameters with `required` keyword
- Optional parameters have default values

**Example:**
```dart
Future<Map<String, dynamic>?> detectFaces({
  required Uint8List data,
  required int width,
  required int height,
  int format = 2050,  // Optional with default
})
```

**Return Values:**
- All async methods return `Future<Map<String, dynamic>?>`
- Null-safe with nullable type annotation `?`

## Module Design

**Platform Interface Pattern:**
- Abstract class extends `PlatformInterface`
- Static instance getter/setter
- Token verification for platform registration

**Example Structure:**
```dart
abstract class ArcPlatform extends PlatformInterface {
  ArcPlatform() : super(token: _token);
  static final Object _token = Object();
  static ArcPlatform _instance = MethodChannelArc();
  static ArcPlatform get instance => _instance;
  static set instance(ArcPlatform instance) {
    PlatformInterface.verifyToken(instance, _token);
    _instance = instance;
  }
}
```

**Method Channel Implementation:**
- Class extends platform interface
- `@visibleForTesting` annotation for test exposure
- Method channel with constant name: `'arc'`

**Singleton Pattern (Java):**
```java
public class FaceEngineManager {
    private static FaceEngineManager instance;
    private FaceEngineManager() {}
    public static synchronized FaceEngineManager getInstance() {
        if (instance == null) {
            instance = new FaceEngineManager();
        }
        return instance;
    }
}
```

## State Management

**Flutter Widget State:**
- Private state variables with underscore prefix
- `StatefulWidget` with corresponding `State` class
- `mounted` check before `setState`

**Example:**
```dart
class _HomePageState extends State<HomePage> {
  String _platformVersion = 'Unknown';
  bool _isActivated = false;

  if (!mounted) return;
  setState(() {
    _platformVersion = platformVersion;
  });
}
```

## Key Files

**Core Dart Files:**
- `lib/arc.dart` - Main API class
- `lib/arc_platform_interface.dart` - Abstract platform interface
- `lib/arc_method_channel.dart` - Method channel implementation

**Core Java Files:**
- `android/src/main/java/com/xiarui/arc/ArcPlugin.java` - Flutter plugin entry
- `android/src/main/java/com/xiarui/arc/FaceEngineManager.java` - Engine singleton
- `android/src/main/java/com/xiarui/arc/FaceErrorCode.java` - Error code enum

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*Convention analysis: 2026-03-30*