proxy.js

import { createServerClient } from "@supabase/ssr";
import { NextResponse } from "next/server";

const PROTECTED_PREFIXES = ["/student", "/teacher", "/admin"];
const AUTH_PAGES = ["/login", "/signup"];

// Proxy (Next.js 16's renamed Middleware) refreshes the Supabase session
// cookie on every request and does an *optimistic* check: is there a
// session at all. It intentionally does not check role — that's a database
// read and belongs in the DAL (src/lib/dal.js), close to the data, per the
// Next.js auth guide. Role mismatches are caught there and rendered via
// forbidden().
export async function proxy(request) {
  let response = NextResponse.next({ request });

  const supabase = createServerClient(
    process.env.NEXT_PUBLIC_SUPABASE_URL,
    process.env.NEXT_PUBLIC_SUPABASE_API,
    {
      cookies: {
        getAll() {
          return request.cookies.getAll();
        },
        setAll(cookiesToSet) {
          cookiesToSet.forEach(({ name, value }) =>
            request.cookies.set(name, value)
          );
          response = NextResponse.next({ request });
          cookiesToSet.forEach(({ name, value, options }) =>
            response.cookies.set(name, value, options)
          );
        },
      },
    }
  );

  const {
    data: { user },
  } = await supabase.auth.getUser();

  const { pathname } = request.nextUrl;
  const isProtected = PROTECTED_PREFIXES.some((prefix) =>
    pathname.startsWith(prefix)
  );
  const isAuthPage = AUTH_PAGES.some((page) => pathname.startsWith(page));

  if (isProtected && !user) {
    const url = request.nextUrl.clone();
    url.pathname = "/login";
    url.searchParams.set("next", pathname);
    return NextResponse.redirect(url);
  }

  if (isAuthPage && user) {
    const url = request.nextUrl.clone();
    url.pathname = "/";
    url.search = "";
    return NextResponse.redirect(url);
  }

  return response;
}

export const config = {
  matcher: [
    "/((?!_next/static|_next/image|favicon.ico|.*\\.(?:svg|png|jpg|jpeg|gif|webp)$).*)",
  ],
};