path: root/REFACTORING.md

# Code Refactoring Summary

This document summarizes the refactoring changes made to the lsfg-vk plugin based on the code review.

## 🏗️ File Structure Changes

### Before (Single File)
```
main.py (500+ lines)
├── InstallationService
├── DllDetectionService  
├── ConfigurationService
└── Plugin
```

### After (Modular Package)
```
lsfg_vk/
├── __init__.py           # Package exports
├── constants.py          # All constants and configuration
├── types.py             # TypedDict definitions for responses
├── base_service.py      # Common functionality for all services
├── installation.py      # InstallationService
├── dll_detection.py     # DllDetectionService
├── configuration.py     # ConfigurationService
└── plugin.py            # Main Plugin class

tests/
├── conftest.py          # Test configuration and fixtures
├── test_installation.py # Tests for InstallationService
├── test_configuration.py # Tests for ConfigurationService
└── test_dll_detection.py # Tests for DllDetectionService

main.py                  # Simple import/export for Decky compatibility
requirements-test.txt    # Testing dependencies
```

## ✨ Key Improvements Implemented

### 1. **Single Responsibility & Modularity**
- Split monolithic file into focused modules
- Each service handles one concern
- Easier to navigate and maintain
- Reduced merge conflicts

### 2. **Constants Management**
- All hardcoded paths moved to `constants.py`
- Template-based script generation
- Environment variable names centralized
- Default values defined in one place

### 3. **Path Handling with `pathlib.Path`**
- Replaced `os.path.*` with `pathlib.Path`
- More declarative and robust path operations
- Built-in `.mkdir(parents=True, exist_ok=True)`
- Cross-platform compatibility

### 4. **Enhanced Error Handling**
- Specific exception catching (`OSError`, `zipfile.BadZipFile`, `shutil.Error`)
- Granular error reporting
- Consistent error response structure
- Better logging of specific failure points

### 5. **Type Safety with TypedDict**
- Defined response structures for all methods
- Consistent API contracts
- Better IDE support and documentation
- Runtime compatibility with `Dict[str, Any]`

### 6. **DRY Principle Implementation**
- `_remove_if_exists()` helper for file removal
- `_atomic_write()` for safe file writing
- `_ensure_directories()` for directory creation
- Unified file destination mapping

### 7. **Atomic File Operations**
- Safe script writing with temporary files
- Prevents corruption during writes
- Proper cleanup on failures
- Consistent file permissions

### 8. **Logger Injection**
- Services accept optional logger parameter
- Defaults to `decky.logger` when None
- Enables unit testing with mock loggers
- Better separation of concerns

### 9. **Robust Configuration Parsing**
- Regex-based parsing instead of string splitting
- Handles edge cases (extra spaces, comments)
- Template-based generation
- Roundtrip consistency testing

### 10. **Comprehensive Testing Framework**
- Unit tests for each service
- Mock filesystem with `pyfakefs`
- Mock logger injection
- Roundtrip testing for configuration
- Environment variable mocking

## 🧪 Testing

### Running Tests
```bash
# Install test dependencies
pip install -r requirements-test.txt

# Run all tests
pytest tests/

# Run with coverage
pytest tests/ --cov=lsfg_vk

# Run specific test file
pytest tests/test_installation.py
```

### Test Coverage
- **Installation Service**: ZIP extraction, file copying, installation checking
- **Configuration Service**: Script parsing, generation, roundtrip testing
- **DLL Detection Service**: Environment variable priority, path checking
- **Mock Integration**: All services work with mock loggers for testing

## 🔄 Migration Guide

### For Developers
The public API remains unchanged - all existing frontend code will continue to work:

```python
# These calls remain identical
plugin.install_lsfg_vk()
plugin.check_lsfg_vk_installed()
plugin.uninstall_lsfg_vk()
plugin.get_lsfg_config()
plugin.update_lsfg_config(...)
plugin.check_lossless_scaling_dll()
```

### For Maintainers
1. **Adding new features**: Add to appropriate service module
2. **Constants**: Define in `constants.py`
3. **New response types**: Add to `types.py`
4. **Testing**: Add tests for new functionality
5. **Common functionality**: Add to `base_service.py`

## 📋 Benefits Achieved

1. **Maintainability**: Easier to find and modify specific functionality
2. **Testability**: Comprehensive unit test coverage
3. **Reliability**: Atomic operations and better error handling
4. **Documentation**: Clear type definitions and API contracts
5. **Extensibility**: Easy to add new services or features
6. **Code Quality**: Follows Python best practices and patterns

## 🚀 Future Improvements

### Next Steps (Not Yet Implemented)
1. **Async/Sync Decision**: Evaluate if true async I/O is needed
2. **Configuration Schema**: JSON schema validation for config files
3. **Dependency Injection**: More sophisticated service container
4. **Integration Tests**: End-to-end testing with real files
5. **Performance Monitoring**: Metrics and logging for operations
6. **Error Recovery**: More sophisticated error handling and retry logic

### Potential Extensions
- Plugin settings persistence
- Multiple DLL version support
- Automatic updates checking
- Performance profiling integration
- Steam integration improvements

---

This refactoring maintains 100% backward compatibility while significantly improving code quality, maintainability, and testability.