Shrinkwrap - PDF Compression Tool

A modern, Kotlin-based desktop application for compressing PDF files using Ghostscript. Built with Compose Multiplatform for a native desktop experience.

🚀 Features

• Drag & Drop Interface: Simply drag PDF files onto the application
• Clipboard Support: Paste files directly with ⌘+V (macOS)
• Real-time Progress: Visual feedback for compression status
• Batch Processing: Handle multiple files simultaneously
• Compression Stats: Shows file size reduction percentages
• Finder Integration: Click files to reveal in Finder

🏗️ Architecture

The application follows a clean, modular architecture designed for maintainability and testability:

src/main/kotlin/
├── Main.kt                     # Application entry point & UI orchestration
├── MainViewModel.kt            # State management & coordination
├── domain/                     # Business logic layer
│   ├── CompressionService.kt   # PDF compression interface & implementation
│   └── FileProcessingState.kt  # Domain models & state
├── infrastructure/             # External dependencies
│   └── CommandExecutor.kt      # System command execution abstraction
├── ui/                        # User interface components
│   ├── components/
│   │   ├── DragDropArea.kt     # Drag & drop functionality
│   │   └── FileListItem.kt     # File list item component
│   └── DashedBorder.kt         # UI utility for dashed borders
└── utils/                     # Common utilities
    └── FileUtils.kt           # File operations & formatting

Key Architectural Principles

• Separation of Concerns: Domain, UI, and Infrastructure layers are clearly separated
• Dependency Injection: Services can be easily mocked and tested
• Interface Segregation: Clean interfaces enable easy testing and extension
• Single Responsibility: Each class has one clear purpose

🛠️ Getting Started

Prerequisites

• Kotlin/JVM: Project uses Kotlin with Compose Desktop

• Ghostscript: Required for PDF compression functionality

  # macOS
  brew install ghostscript
  
  # Ubuntu/Debian
  sudo apt-get install ghostscript
  

Building & Running

# Clone the repository
git clone <repository-url>
cd shrinkwrap

# Build the application
./gradlew build

# Run the application
./gradlew run

# Create native distribution
./gradlew createDistributable

🧪 Testing Strategy

The modular architecture enables comprehensive testing:

Unit Tests

// Service layer testing
class CompressionServiceTest {
    @Test
    fun `should compress valid PDF file`() {
        val mockCommandExecutor = mockk<CommandExecutor>()
        val service = GhostscriptCompressionService(mockCommandExecutor)
        // Test without system dependencies
    }
}

// State management testing
class MainViewModelTest {
    @Test
    fun `should update state when file is added`() {
        val mockService = mockk<CompressionService>()
        val viewModel = MainViewModel(mockService)
        // Test state transitions
    }
}

Integration Tests

• Test UI components with test state
• Test end-to-end file processing workflows
• Test error handling scenarios

🔮 Future Enhancements

High Priority

1. Compression Quality Settings

• Add UI controls for high/medium/low quality selection
• Remember user preferences
• Quality preview before compression

2. Enhanced Error Handling

• User-friendly error messages
• Retry mechanisms for failed compressions
• Better validation feedback

3. Progress & Performance

• Detailed progress bars for large files
• Compression speed metrics
• Estimated time remaining

Medium Priority

4. Multiple Compression Backends

// Easy to implement with current architecture
class PDFtkCompressionService : CompressionService { ... }
class ImageMagickCompressionService : CompressionService { ... }

5. Batch Operations

• Select compression quality per batch
• Pause/resume batch processing
• Export compression reports

6. File Management

• Original file backup options
• Custom output directory selection
• File name templates (e.g., {original}_compressed.pdf)

7. Advanced Features

• PDF optimization beyond compression
• Image quality adjustments within PDFs
• Metadata preservation options

Lower Priority

8. User Experience

• Dark/light theme toggle
• Keyboard shortcuts for common actions
• Recent files list
• Undo/redo functionality

9. Analytics & Reporting

• Compression statistics dashboard
• Export compression reports
• Historical data tracking

10. Cross-Platform Enhancements

• Windows Explorer integration
• Linux file manager integration
• Platform-specific optimizations

Technical Enhancements

11. Performance Optimizations

• Memory-efficient processing for large files
• Background compression queue
• Multi-threaded processing improvements

12. Configuration System

• Settings persistence
• Custom Ghostscript parameters
• Advanced user configurations

13. Plugin Architecture

• Custom compression algorithms
• Third-party integrations
• Extension marketplace

🤝 Contributing

Code Style

• Follow Kotlin coding conventions
• Use meaningful variable and function names
• Add KDoc comments for public APIs
• Keep functions focused and small

Testing Requirements

• Unit tests for all business logic
• UI tests for interactive components
• Integration tests for file operations
• Maintain >80% code coverage

Architecture Guidelines

• Keep domain logic pure (no UI or infrastructure dependencies)
• Use dependency injection for testability
• Create reusable UI components
• Handle errors gracefully with meaningful messages

📋 Implementation Notes

Adding New Compression Backends

1. Implement CompressionService interface
2. Add to dependency injection in MainViewModel
3. Add UI selection controls
4. Update tests

Adding New UI Components

1. Create in ui/components/ package
2. Follow existing component patterns
3. Make components reusable and configurable
4. Add preview functions for development

Performance Considerations

• Large files should be processed in chunks
• UI should remain responsive during processing
• Memory usage should be monitored for batch operations

📝 License

[Add your license information here]

🙏 Acknowledgments

• Compose Multiplatform for the UI framework
• Ghostscript for PDF compression engine