not-working-middleware.ts

import { getToken } from "next-auth/jwt";
import { withAuth } from "next-auth/middleware";
import { NextResponse } from "next/server";

// For the time being, the withAuth middleware only supports "jwt" as session strategy.
export default withAuth(async function middleware(req) {
  const token = await getToken({ req });
  // if token exists, !!token will be true
  const isAuthenticated = !!token;

  // first, check if the current path is login page
  if (req.nextUrl.pathname.startsWith("/login")) {
    // I am in "login" page now  I check if the user is authenticated or not
    if (isAuthenticated) {
      // If I get here it means user is on "login" page and it is authenticated. then redirect it to whatever url
      return NextResponse.redirect(new URL("/", req.url));
    }
  }
});

// specify on which routes you want to run the middleware
export const config = {
  matcher: ["/register", "/login"],
};