How to make a reusable getServerSideProps function

next-reusable-ssr-auth-check.js

// pages/protected.js
import protectRoute from "utils/protect-route";

export async function getServerSideProps({ req }) {
  return await protectRoute(req, (user) => {
    return { props: { user } };
  });
}

// protect-route.js
import { supabase } from "@supabase";

const protectRoute = async (req, callback) => {
  const { user } = await supabase.auth.api.getUserByCookie(req); // use any auth provider you want

  if (!user) {
    return { props: {}, redirect: { destination: "/sign-in" } };
  }

  return callback?.(user) ?? { props: {} };
};

export default protectRoute;