svrjs-nextjs-website/middleware.ts

import { NextResponse } from "next/server";
import type { NextRequest } from "next/server";
import { getToken } from "next-auth/jwt";

export async function middleware(req: NextRequest) {
  const token = await getToken({ req, secret: process.env.NEXTAUTH_SECRET });

  if (req.nextUrl.pathname.startsWith("/admin") && !token) {
    const url = req.nextUrl.clone();
    url.pathname = "/login";
    return NextResponse.redirect(url);
  }

  return NextResponse.next();
}

export const config = {
  matcher: ["/admin/:path*"],
};