Authentication with Auth.js

// app/api/auth/[...nextauth]/route.ts
import NextAuth from "next-auth";
import GoogleProvider from "next-auth/providers/google";
import CredentialsProvider from "next-auth/providers/credentials";

const handler = NextAuth({
  providers: [
    GoogleProvider({
      clientId: process.env.GOOGLE_ID!,
      clientSecret: process.env.GOOGLE_SECRET!,
    }),
    CredentialsProvider({
      async authorize(credentials) {
        const user = await db.users.findByEmail(credentials.email);
        if (!user || !bcrypt.compare(credentials.password, user.password)) {
          return null;  // null = authentication failed
        }
        return user;  // return user to create session
      },
    }),
  ],
  callbacks: {
    async jwt({ token, user }) {
      if (user) token.role = user.role;  // add custom fields
      return token;
    },
    async session({ session, token }) {
      session.user.role = token.role;  // expose in session
      return session;
    },
  },
});

export { handler as GET, handler as POST };

// lib/auth.ts — shared auth config

import { authOptions } from "@/app/api/auth/[...nextauth]/route";

export async function requireAuth() {
  const session = await auth();
  if (!session) redirect("/login");
  return session;
}

export async function requireAdmin() {
  const session = await requireAuth();
  if (session.user.role !== "admin") redirect("/unauthorized");
  return session;
}

// app/admin/page.tsx — admin-only page
export default async function AdminPage() {
  const session = await requireAdmin();  // redirects if not admin
  const stats = await getAdminStats();
  return <AdminDashboard stats={stats} user={session.user} />;
}

// Client component — check session
"use client";
import { useSession, signIn, signOut } from "next-auth/react";

function AuthButton() {
  const { data: session, status } = useSession();
  if (status === "loading") return <Spinner />;
  if (session) return <button onClick={() => signOut()}>Sign Out</button>;
  return <button onClick={() => signIn("google")}>Sign in with Google</button>;
}