# Development Guide

## Prerequisites

- Node.js 18 or higher
- Linux operating system (for full functionality)
- Basic understanding of procfs and Linux system internals
- TypeScript knowledge

## Setup Development Environment

```bash
# Clone the repository
git clone https://github.com/cameronrye/activitypub-mcp.git
cd activitypub-mcp/mcp-proc

# Install dependencies
npm install

# Build the project
npm run build
```

## Project Structure

```
mcp-proc/
├── src/
│   ├── lib/                    # Core library code
│   │   ├── procfs-reader.ts   # ProcFS reading logic
│   │   └── procfs-writer.ts   # ProcFS writing logic
│   ├── types/                  # Type definitions
│   │   ├── procfs.ts          # ProcFS types
│   │   ├── mcp.ts             # MCP protocol types
│   │   └── schemas.ts         # Zod validation schemas
│   ├── server.ts              # MCP JSON-RPC server
│   ├── server-sse.ts          # HTTP/SSE server
│   ├── cli.ts                 # CLI for JSON-RPC server
│   ├── cli-sse.ts             # CLI for HTTP server
│   └── index.ts               # Main exports
├── examples/                   # Usage examples
├── scripts/                    # Build and setup scripts
├── tests/                      # Test files
└── docs/                       # Documentation
```

## Development Workflow

### Running in Development Mode

```bash
# Watch mode with hot reload
npm run dev

# For HTTP/SSE server
npm run start:sse
```

### Building

```bash
# Compile TypeScript
npm run build

# Clean build
rm -rf dist/ && npm run build
```

### Testing

```bash
# Run all tests
npm test

# Watch mode
npm run test:watch

# Coverage report
npm run test:coverage
```

### Linting and Formatting

```bash
# Check code style
npm run lint

# Format code
npm run format
```

## Adding New Features

### Adding a New ProcFS Reader

1. Add the method to `src/lib/procfs-reader.ts`:

```typescript
async getNewMetric(): Promise<NewMetricType> {
  const content = await this.readRaw('path/to/file');
  // Parse content
  return parsedData;
}
```

2. Add the type definition in `src/types/procfs.ts`:

```typescript
export interface NewMetricType {
  field1: string;
  field2: number;
}
```

3. Add validation schema in `src/types/schemas.ts`:

```typescript
export const NewMetricRequestSchema = z.object({
  param: z.string(),
});
```

4. Add tool definition in `src/server.ts`:

```typescript
{
  name: 'get_new_metric',
  description: 'Get new metric',
  inputSchema: {
    type: 'object',
    properties: {
      param: { type: 'string' }
    }
  }
}
```

5. Add HTTP endpoint in `src/server-sse.ts`:

```typescript
this.app.get('/api/new-metric', async (req, res) => {
  try {
    const data = await this.reader.getNewMetric();
    res.json({ success: true, data });
  } catch (error) {
    res.status(500).json({ 
      success: false, 
      error: (error as Error).message 
    });
  }
});
```

### Adding Tests

Create test file in `tests/`:

```typescript
import { ProcFSReader } from '../src/lib/procfs-reader';

describe('ProcFSReader', () => {
  let reader: ProcFSReader;

  beforeEach(() => {
    reader = new ProcFSReader();
  });

  test('should read CPU info', async () => {
    const info = await reader.getCPUInfo();
    expect(info).toHaveProperty('model');
    expect(info).toHaveProperty('cores');
  });
});
```

## Code Style Guidelines

- Use TypeScript strict mode
- Follow ESLint rules
- Use Prettier for formatting
- Add JSDoc comments for public APIs
- Use async/await for asynchronous code
- Handle errors gracefully
- Validate inputs with Zod schemas

## Debugging

### Debug MCP Server

```bash
# With debug output
DEBUG=* npm start
```

### Debug HTTP Server

```bash
# Check server logs
npm run start:sse

# Test endpoints
curl http://localhost:3000/health
```

### Using VS Code Debugger

Create `.vscode/launch.json`:

```json
{
  "version": "0.2.0",
  "configurations": [
    {
      "type": "node",
      "request": "launch",
      "name": "Debug Server",
      "program": "${workspaceFolder}/src/cli.ts",
      "preLaunchTask": "npm: build",
      "outFiles": ["${workspaceFolder}/dist/**/*.js"]
    }
  ]
}
```

## Common Issues

### Permission Errors

Some operations require elevated permissions:

```bash
# Run with sudo (not recommended for development)
sudo npm start

# Better: Use capabilities
sudo setcap cap_sys_nice,cap_sys_admin+ep $(which node)
```

### TypeScript Errors

```bash
# Clean and rebuild
rm -rf dist/ node_modules/
npm install
npm run build
```

### Port Already in Use

```bash
# Change port
PORT=8080 npm run start:sse

# Kill process using port 3000
lsof -ti:3000 | xargs kill -9
```

## Contributing

1. Fork the repository
2. Create a feature branch
3. Make your changes
4. Add tests
5. Run linting and tests
6. Submit a pull request

### Commit Message Format

```
type(scope): subject

body

footer
```

Types:
- `feat`: New feature
- `fix`: Bug fix
- `docs`: Documentation
- `style`: Formatting
- `refactor`: Code restructuring
- `test`: Adding tests
- `chore`: Maintenance

Example:
```
feat(procfs): add disk temperature reading

Add support for reading disk temperature from /sys/class/hwmon.
Includes new getDiskTemperature() method in ProcFSReader.

Closes #123
```

## Release Process

1. Update version in `package.json`
2. Update `CHANGELOG.md`
3. Run tests: `npm test`
4. Build: `npm run build`
5. Commit changes
6. Create git tag: `git tag v1.0.0`
7. Push: `git push --follow-tags`
8. Publish: `npm publish`

Or use the release script:

```bash
./scripts/release.sh 1.0.0
```

## Resources

- [MCP Specification](https://modelcontextprotocol.io)
- [TypeScript Documentation](https://www.typescriptlang.org/docs/)
- [Express.js Guide](https://expressjs.com/en/guide/routing.html)
- [Zod Documentation](https://zod.dev/)
- [Jest Testing Framework](https://jestjs.io/)