nextjs-handler-add-user-middleware.ts

import { Middleware } from 'next-api-route-middleware';
import { getUserByCookie } from '../utils';

export type User = { userId: string };
export type NextApiRequestWithUser = NextApiRequest & User;

export const addUser: Middleware<NextApiRequestWithUser> = async (req, res, next) => {
  const authCookie = await getUserByCookie();

  if (authCookie) {
    req.userId = authCookie.userId;
    next();
  } else {
    res.status(401).send({ message: 'Invalid auth cookie.' });
  }
};