Next.js high-order function middlewware

auth.ts

// util/middleware/auth.ts
import { NextApiRequest, NextApiResponse } from 'next'
import { User } from './models/user'

// so we can add the user info to the req object
type NextApiRequestWithUser = NextApiRequest & {
	user: string
}

export const auth = (handler: (req: NextApiRequestWithUser, res: NextApiResponse) => void) => {
  return async (req: NextApiRequest, res: NextApiResponse): Promise<void> => {
	  const { email, password } = req.body
	  
	  if (!email || !password) {
		  return res.status(401).json({message: "missing email or password"})
	  }
	  
	  const user = await User.findOne({ email })
	  if (!user) {
	  	return res.status(401).json({ message: "unauthorized" })
	  }
	  
	  const isAllowed = user.authenticate({ user, password })
	  if (!isAllowed) {
	  	return res.status(401).json({ message: "unauthorized" })
	  }
	  
	  // if it's successful add the user info to the request object
	  // let the request get through
	  req.user = user
	  return handler(req, res)
  }
}