Architectural Refactoring

[rmottanet]

Monolithic to Layered Architecture

This PR implements a comprehensive architectural refactoring of the Branch Spawn GitHub Action, transitioning from a monolithic structure to a modular, layered architecture following SOLID principles and clean code practices.

Changes

🏗 Architectural Transformation

• Before: Single monolithic index.ts handling configuration, business logic, and GitHub API operations
• After: Clear separation of concerns with dedicated layers for configuration, services, and orchestration

📁 New Module Structure

src/
├── main.ts          # Pure orchestrator - workflow coordination only
├── config.ts        # Input validation and configuration management
└── services/
    └── github.service.ts  # GitHub API operations layer

🔧 Technical Improvements

1. Single Responsibility Principle (SRP)

• ConfigManager: Exclusive responsibility for input validation and configuration
• GitHubService: Dedicated to GitHub API operations with typed Octokit client
• main.ts: Pure orchestration and error handling

2. Type Safety & Validation

// Immutable input interface
export interface ActionInputs {
  readonly owner: string;
  readonly repo: string;
  readonly baseBranch: string;
  readonly newBranch: string;
  readonly githubToken: string;
}

// Centralized validation
private static validate(inputs: ActionInputs): void

3. Dependency Injection & Testability

// Manual dependency injection for better testability
const gitService = new GitHubService(inputs.githubToken);

4. Clean Error Handling

• Structured error classification with proper type checking
• Early validation failures before API operations
• Descriptive error messages for better debugging

🛡 Security & Robustness

• Input sanitization and trimming
• Branch naming validation with regex patterns
• Duplicate branch name prevention
• Token validation before API usage

📦 Build & Distribution

• Updated build artifacts to reflect new architecture
• Maintained backward compatibility with existing Action API
• Updated package.json entry points

Benefits

🎯 Immediate Impact

• Better Maintainability: Clear module boundaries and responsibilities
• Enhanced Testability: Isolated components enable unit testing
• Improved Debugging: Structured error handling and validation
• Type Safety: Full TypeScript integration with Octokit SDK

🔮 Future Extensibility

• Easy addition of new GitHub API operations
• Simplified configuration expansion
• Straightforward testing strategy implementation
• Clean foundation for additional features

Migration Notes

✅ Backward Compatibility

• External Action interface remains unchanged
• Input parameters and behavior preserved
• Existing workflows continue working without modification

🔄 Code Quality Metrics

• Reduced cyclomatic complexity through separation
• Improved cohesion within each module
• Reduced coupling between components
• Enhanced code readability and documentation

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This refactoring establishes a professional, enterprise-ready foundation for future development while maintaining full compatibility with existing implementations.