Build a Production-Ready REST API with Node.js and Express

src/
├── controllers/     # Request handlers
├── middleware/      # Auth, validation, error handling
├── models/          # Database schemas
├── routes/          # API endpoints
├── services/        # Business logic
├── utils/           # Helper functions
├── validators/      # Request validation schemas
└── app.js           # Express app setup

const jwt = require('jsonwebtoken');

const generateToken = (userId) => {
  return jwt.sign(
    { userId },
    process.env.JWT_SECRET,
    { expiresIn: '7d' }
  );
};

const authMiddleware = (req, res, next) => {
  const token = req.headers.authorization?.split(' ')[1];
  
  if (!token) {
    return res.status(401).json({ error: 'Unauthorized' });
  }
  
  try {
    const decoded = jwt.verify(token, process.env.JWT_SECRET);
    req.userId = decoded.userId;
    next();
  } catch (error) {
    return res.status(401).json({ error: 'Invalid token' });
  }
};