# Coding Conventions

**Analysis Date:** 2026-04-16

## Overview

This is a Flutter plugin package (`ch34`) that provides USB-to-serial communication for WCH CH34X series chips. The codebase is written in Dart with Android native code (Java). The plugin follows the standard Flutter plugin federated architecture pattern.

## Naming Patterns

**Files:**
- Dart files use `snake_case`: `ch34_manager.dart`, `ch34_platform_interface.dart`, `ch34_method_channel.dart`, `ch34_types.dart`
- Test files mirror source file names: `ch34_test.dart`, `ch34_method_channel_test.dart`
- Java native files use `PascalCase`: `Ch34Plugin.java`, `Ch34UsbStateStreamHandler.java`

**Classes:**
- PascalCase with `Ch34` prefix for public API: `Ch34Manager`, `Ch34Platform`, `MethodChannelCh34`, `Ch34Exception`
- Domain models without prefix: `GpioStatus`, `SerialParameter`, `ModemStatus`, `UsbDeviceInfo`
- Enum naming: `DataBits`, `StopBits`, `Parity`, `GpioDirection`, `GpioValue`, `SerialErrorType`

**Functions/Methods:**
- camelCase for all methods: `getPlatformVersion()`, `enumDevice()`, `openDevice()`, `setSerialParameter()`
- Callback-style methods use descriptive names: `setUsbStateListener()`, `registerDataCallback()`, `registerModemStatusCallback()`
- Private methods use underscore prefix: `_cancelDataSubscription()`
- Private constructor pattern: `Ch34Manager._()` (static-only class)

**Variables:**
- camelCase: `deviceName`, `serialNumber`, `gpioIndex`, `onStateChanged`
- Private fields use underscore prefix: `_dataSubscription`, `_modemCallback`
- Constants use const: `const MethodChannel('ch34')`

**Parameters:**
- Named parameters use curly braces for optional: `{int timeout = 0}`
- Required named parameters use `required` keyword in data classes

## Code Style

**Formatting:**
- Uses `flutter_lints` package (`^3.0.0`) with default `flutter.yaml` ruleset
- Config: `D:/code/new_git_code/flutter/ch34/analysis_options.yaml`
- Example app config: `D:/code/new_git_code/flutter/ch34/example/analysis_options.yaml` (same base, with commented-out custom rules)
- No custom lint rules are enabled beyond the default Flutter set
- No `.prettierrc` or other formatter config (uses Dart formatter defaults)

**SDK Constraints:**
- SDK: `>=3.4.3 <4.0.0` (`D:/code/new_git_code/flutter/ch34/pubspec.yaml`)
- Flutter: `>=3.3.0`

**Import Organization:**
1. Dart SDK imports first: `import 'dart:typed_data';`, `import 'dart:async';`
2. Flutter framework imports: `import 'package:flutter/services.dart';`
3. Third-party package imports: `import 'package:plugin_platform_interface/plugin_platform_interface.dart';`
4. Relative local imports last: `import 'ch34_platform_interface.dart';`, `import 'types/ch34_types.dart';`
- Groups separated by blank lines

**Path Aliases:**
- No path aliases detected; all imports use relative paths within the package

## Patterns

**Static Manager Pattern:**
`D:/code/new_git_code/flutter/ch34/lib/src/ch34_manager.dart` uses a private constructor (`Ch34Manager._()`) with all static methods, delegating to `Ch34Platform.instance`. This provides a clean public API without requiring instantiation.

```dart
class Ch34Manager {
  Ch34Manager._();

  static Future<String?> getPlatformVersion() {
    return Ch34Platform.instance.getPlatformVersion();
  }
}
```

**Platform Interface (Federated Plugin):**
`D:/code/new_git_code/flutter/ch34/lib/src/ch34_platform_interface.dart` extends `PlatformInterface` from `plugin_platform_interface`. Uses token-based verification for instance safety:

```dart
abstract class Ch34Platform extends PlatformInterface {
  Ch34Platform() : super(token: _token);
  static final Object _token = Object();
  static Ch34Platform? _instance;

  static Ch34Platform get instance { ... }
  static set instance(Ch34Platform instance) { ... }
}
```

**MethodChannel + EventChannel Pattern:**
`D:/code/new_git_code/flutter/ch34/lib/src/ch34_method_channel.dart` uses:
- `MethodChannel` for request-response calls: `methodChannel.invokeMethod<bool>('openDevice', {...})`
- `EventChannel` for streaming data: `dataEventChannel.receiveBroadcastStream({'deviceName': deviceName}).listen(...)`
- `@visibleForTesting` annotation for testable fields (channel names)

**Data Class Pattern:**
`D:/code/new_git_code/flutter/ch34/lib/src/types/ch34_types.dart` uses immutable classes with:
- `const` constructors
- `fromMap()` factory for deserialization
- `toMap()` method for serialization
- `toString()` override for debugging
- `copyWith()` for mutable updates (e.g., `SerialParameter.copyWith()`)
- `==`/`hashCode` override for equality (e.g., `UsbDeviceInfo`)

```dart
class SerialParameter {
  const SerialParameter({
    this.baud = 115200,
    this.dataBits = DataBits.bits8,
    ...
  });

  factory SerialParameter.fromMap(Map<dynamic, dynamic> map) { ... }
  Map<String, dynamic> toMap() { ... }
  SerialParameter copyWith({ ... }) { ... }
}
```

**Enum with Associated Values:**
Enums use associated integer values with `fromValue()` factory:

```dart
enum DataBits {
  bits5(5), bits6(6), bits7(7), bits8(8);
  const DataBits(this.value);
  final int value;
  static DataBits fromValue(int value) =>
    DataBits.values.firstWhere((e) => e.value == value, orElse: () => DataBits.bits8);
}
```

**Null-Safe Default Handling:**
Method channel results consistently use null-coalescing for safe defaults:
```dart
return result ?? false;       // boolean methods
return result ?? 0;           // integer methods
return result ?? [];          // list methods
return result ?? Uint8List(0); // byte data
```

**Section Comments:**
Code is organized with clear separator comments:
```dart
/// ==================== 基础方法 ====================
/// ==================== 设备枚举与识别 ====================
/// ==================== 数据读写 ====================
```

## Error Handling

**Custom Exception:**
`D:/code/new_git_code/flutter/ch34/lib/src/ch34_method_channel.dart` defines `Ch34Exception`:
```dart
class Ch34Exception implements Exception {
  const Ch34Exception(this.message);
  final String message;
  @override
  String toString() => 'Ch34Exception: $message';
}
```

**Usage Patterns:**
- Platform interface methods document `@throws Ch34Exception` in JSDoc comments for methods that may fail
- Actual throwing is limited: only GPIO methods throw `Ch34Exception` when native returns null
- Most boolean methods return `false` on failure rather than throwing
- Example app uses generic `catch (e)` for error display in UI:
  ```dart
  } catch (e) {
    setState(() {
      _status = '扫描失败: $e';
    });
  }
  ```
- `StateError` thrown when platform instance not initialized:
  ```dart
  throw StateError('Ch34Platform.instance has not been initialized...');
  ```

**Stream Error Handling:**
EventChannel streams use `onError` callback with `debugPrint`:
```dart
onError: (error) {
  debugPrint('CH34 data callback error: $error');
}
```

## Logging

**Framework:** Flutter's `debugPrint` from `package:flutter/foundation.dart`

**Patterns:**
- Used only in error callbacks within the method channel implementation
- Log messages are descriptive with context prefix: `'CH34 USB state error: $error'`
- No logging framework beyond `debugPrint`
- Debug mode toggle available via `Ch34Manager.setDebug(bool)` (passes to native side)

## Comments & Documentation

**API Documentation:**
- All public methods have `///` Dart doc comments in Chinese
- Consistent param/return documentation using `@param` and `@return`
- Exception documentation using `@throws`
- Library-level docs at `D:/code/new_git_code/flutter/ch34/lib/ch34.dart` include usage example in code block

**Inline Comments:**
- Chinese section headers for method grouping
- Method-level comments explain purpose, parameters, and return values

**JSDoc/TSDoc Style:**
- Uses `///` (not `/** */`) for doc comments
- Parameter docs: `/// @param deviceName 设备名称。`
- Return docs: `/// @return \`true\` 成功，\`false\` 失败。`

## Module Design

**Exports:**
- Main entry `D:/code/new_git_code/flutter/ch34/lib/ch34.dart` exports all public types:
  ```dart
  export 'src/ch34_manager.dart';
  export 'src/types/ch34_types.dart';
  export 'src/ch34_platform_interface.dart' show Ch34Platform;
  export 'src/ch34_method_channel.dart' show Ch34Exception;
  ```
- Backward-compatible barrel files at `lib/` root:
  - `D:/code/new_git_code/flutter/ch34/lib/ch34_platform_interface.dart`
  - `D:/code/new_git_code/flutter/ch34/lib/ch34_method_channel.dart`

**Layer Separation:**
```
lib/ch34.dart                              -> Public API entry (exports)
lib/src/ch34_manager.dart                  -> Static facade (public-facing)
lib/src/ch34_platform_interface.dart       -> Abstract interface
lib/src/ch34_method_channel.dart           -> Concrete implementation
lib/src/types/ch34_types.dart              -> Data types and enums
```

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*Convention analysis: 2026-04-16*