PR Bot Reviewer

An automated GitHub webhook handler that triggers AI code reviews when bots open pull requests. Built for Val Town deployment.

The PR Bot Reviewer automatically detects when a bot opens a pull request and posts a standardized comment to trigger multiple AI code review services. This ensures consistent code quality checks for automated PRs without manual intervention.

• 🤖 Smart Bot Detection: Identifies bot users by GitHub type or login pattern
• 🔄 Multi-Service Reviews: Triggers 4 different AI review services simultaneously
• 🛡️ Robust Error Handling: Comprehensive error handling with detailed logging
• 🚀 Val Town Ready: Optimized for serverless deployment on Val Town
• 📝 TypeScript: Fully typed with comprehensive interfaces

Set the required environment variable in your Val Town project:

GITHUB_TOKEN=your_github_personal_access_token_here

GitHub Token Requirements:

• Must be a Personal Access Token (PAT)
• Requires repo scope for posting comments on pull requests
• Should have access to the repositories where you want to enable bot PR reviews

1. Create a new HTTP Val in Val Town
2. Copy the contents of webhook-handler.http.ts into your Val
3. Set the GITHUB_TOKEN environment variable
4. Save and deploy your Val

1. Go to your repository settings → Webhooks
2. Click "Add webhook"
3. Set the Payload URL to your Val Town endpoint: https://[username]-[valname].web.val.run
4. Set Content type to application/json
5. Select "Let me select individual events" and choose:
   • ✅ Pull requests
6. Ensure the webhook is Active
7. Click "Add webhook"

graph LR
    A[Bot opens PR] --> B[GitHub Webhook]
    B --> C[Val Town Handler]
    C --> D{Is Bot User?}
    D -->|Yes| E[Post Review Comment]
    D -->|No| F[Skip Processing]
    E --> G[AI Reviews Triggered]

The system identifies bot users using two criteria:

• Type-based: Users with type: "Bot" in GitHub API
• Login-based: Users with login ending in [bot] (e.g., dependabot[bot])

When a bot PR is detected, the following review triggers are posted:

@coderabbitai review
/gemini review
@cubic-dev-ai review
@greptile review

1. Go to GitHub Settings → Developer settings → Personal access tokens → Tokens (classic)
2. Click "Generate new token (classic)"
3. Set expiration and select scopes:
   • ✅ repo (Full control of private repositories)
4. Click "Generate token"
5. Copy the token immediately (you won't see it again)

The handler expects GitHub webhook payloads with the following structure:

interface WebhookPayload {
  action: string;           // Must be "opened"
  number: number;          // PR number
  pull_request: {
    user: {
      login: string;       // GitHub username
      type: string;        // User type ("Bot" or "User")
      id: number;         // User ID
    };
  };
  repository: {
    full_name: string;     // Repository name (owner/repo)
  };
}

Success Response (200):

{
  "success": true,
  "message": "Review comment posted successfully for bot PR #123 by dependabot[bot]",
  "timestamp": "2024-01-01T12:00:00.000Z"
}

Error Response (4xx/5xx):

{
  "error": "ERROR_CODE",
  "message": "Human readable error message",
  "timestamp": "2024-01-01T12:00:00.000Z"
}

The system provides comprehensive error handling for various scenarios:

Webhook not triggering:

1. Check webhook configuration in repository settings
2. Verify webhook URL points to your Val Town endpoint
3. Ensure webhook is set to send "Pull requests" events

Authentication errors:

1. Verify GITHUB_TOKEN is set correctly
2. Check token has repo scope
3. Ensure token hasn't expired

Comments not posting:

1. Check repository permissions for the token
2. Verify PR number and repository name in logs
3. Check GitHub API status

├── webhook-handler.http.ts    # Main webhook handler (Val Town entry point)
├── README.md                  # This documentation
└── .kiro/specs/              # Feature specifications
    └── pr-bot-reviewer/
        ├── requirements.md    # Feature requirements
        ├── design.md         # Technical design
        └── tasks.md          # Implementation tasks

• BotDetector: Identifies bot users from GitHub data
• GitHubApiClient: Handles GitHub API authentication and requests
• CommentService: Generates and posts review comments
• WebhookHandler: Main request processing logic

The project includes comprehensive test coverage:

• Unit tests for individual components
• Property-based tests for universal behaviors
• Integration tests for end-to-end workflows

• Val Town account with HTTP trigger support
• Environment variable configuration capability
• Internet access for GitHub API calls

1. Create New Val: Create an HTTP trigger Val in Val Town
2. Copy Code: Paste the webhook handler code
3. Set Environment: Configure GITHUB_TOKEN in Val settings
4. Test Endpoint: Verify the Val responds to HTTP requests
5. Configure Webhook: Point GitHub webhook to your Val URL

• Uses Deno.env.get() for environment variables
• Exports default function as HTTP handler entry point
• Includes proper error handling for serverless environment
• Optimized for Val Town's execution model

• ✅ Never hardcode GitHub tokens in source code
• ✅ Use environment variables for sensitive configuration
• ✅ Validate all incoming webhook payloads
• ✅ Implement proper error handling to prevent information leakage
• ✅ Use HTTPS endpoints for webhook URLs

• Store tokens as environment variables only
• Use tokens with minimal required permissions (repo scope)
• Regularly rotate Personal Access Tokens
• Monitor token usage in GitHub settings

The system provides detailed logging for troubleshooting:

// Example log output
{
  "error": "GitHub API authentication failed",
  "timestamp": "2024-01-01T12:00:00.000Z",
  "url": "https://api.github.com/repos/owner/repo/issues/123/comments",
  "status": 401
}

Monitor these indicators for system health:

• Webhook delivery success rate in GitHub settings
• Error rates in Val Town logs
• GitHub API rate limit usage
• Response time metrics

1. Fork the repository
2. Create a feature branch
3. Make your changes
4. Add tests for new functionality
5. Submit a pull request

This project is open source and available under the MIT License.

For issues and questions:

1. Check the troubleshooting section above
2. Review Val Town documentation for deployment issues
3. Check GitHub webhook documentation for configuration help
4. Open an issue in the repository for bugs or feature requests