Halin (ဟန်လင်း)

A lightweight, fast, and type-safe web framework for Bun, inspired by Express and Hono.

Features

• 🚀 Built for Bun's high-performance runtime
• 📝 First-class TypeScript support
• 🔄 Flexible middleware system
• 🛣️ Express-style routing with parameters
• 👥 Route grouping with shared middleware
• 🌊 Server-Sent Events (SSE) support
• 🔒 Built-in error handling
• 🎯 Custom HTTP methods support

Installation

bun add halin

Quick Start

import { Halin } from 'halin';

const app = new Halin();

// Basic middleware (logging)
app.use(async (req, res, next) => {
  console.log(`[${new Date().toISOString()}] ${req.method} ${req.path}`);
  await next();
});

// Simple route
app.get('/', (req, res) => {
  res.send('Welcome to Halin!');
});

// Start server
app.listen(3000, () => {
  console.log('Server started on http://localhost:3000');
});

Core Concepts

Routing

// Basic routes
app.get('/', (req, res) => {
  res.send('Hello World!');
});

// Routes with parameters
app.get('/users/:id', (req, res) => {
  res.json({
    userId: req.params.id,
    query: req.query
  });
});

// POST handling with JSON body
app.post('/data', async (req, res) => {
  const data = req.body;
  res.status(201).json({ received: data });
});

Middleware

// Global middleware
app.use(async (req, res, next) => {
  console.log(`${req.method} ${req.path}`);
  await next();
});

// Error handling middleware
app.use((err, req, res, next) => {
  if (err instanceof HalinError) {
    res.status(err.statusCode).json({
      error: err.message,
      status: err.statusCode
    });
  } else {
    next(err);
  }
});

Route Groups

app.group('/api')
  .use((req, res, next) => {
    // Authentication middleware
    if (req.headers.get('x-api-key') !== 'secret') {
      throw new HalinError(401, 'Invalid API key');
    }
    next();
  })
  .routes(api => {
    // Routes under /api
    api.get('/users', (req, res) => {
      res.json([{ id: 1, name: 'John' }]);
    });

    // Nested groups
    api.group('/v2').routes(v2 => {
      v2.get('/products', (req, res) => {
        res.json([{ id: 'p1', name: 'Product 1' }]);
      });
    });
  });

CORS Example

const cors = (req, res, next) => {
  res.headers.set('Access-Control-Allow-Origin', '*');
  res.headers.set('Access-Control-Allow-Methods', 'GET, POST');
  res.headers.set('Access-Control-Allow-Headers', 'Content-Type, Authorization');
  next();
};

app.options('/cors', cors, (req, res) => {
  res.text('');
});

app.get('/cors', cors, (req, res) => {
  res.json({ message: 'CORS enabled' });
});

Server-Sent Events (SSE)

app.get('/sse', (req, res) => {
  const sse = res.sse();
  let count = 0;

  const interval = setInterval(() => {
    sse.send(`Message ${count++}`);
    if (count >= 5) {
      sse.close();
      clearInterval(interval);
    }
  }, 1000);

  return sse;
});

API Reference

Request Object

• req.method: HTTP method
• req.url: Full URL
• req.path: URL pathname
• req.params: Route parameters
• req.query: Query parameters
• req.headers: Request headers
• req.body: Request body (parsed automatically)
• req.raw: Raw Bun request object

Response Object

• res.status(code): Set status code
• res.headers: Response headers
• res.json(data): Send JSON response
• res.text(data): Send text response
• res.send(data): Smart send (auto-detects type)
• res.sse(): Create SSE connection
• res.stream(stream): Send streaming response

Error Handling

import { Halin, HalinError } from 'halin';

// Using the built-in error handler
app.get('/error', () => {
  throw new HalinError(418, "I'm a teapot");
});

// Custom error handling middleware
app.use((err: Error, req: Request, res: Response, next: NextFunction) => {
  if (err instanceof HalinError) {
    res.status(err.statusCode).json({
      error: err.message
    });
  } else {
    next(err);
  }
});

TypeScript Support

Halin is written in TypeScript and provides full type safety. Key types:

type Handler = (req: Request, res: Response, next?: NextFunction) => Promise<void> | void;
type ErrorHandler = (error: Error, req: Request, res: Response, next: NextFunction) => Promise<void> | void;

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

MIT License - See LICENSE file for details.