umami/pages/admin.js

import React from 'react';
import cookies from 'next-cookies';
import Layout from 'components/Layout';
import { verifySecureToken } from 'lib/crypto';

export default function Admin({ username }) {
  return (
    <Layout title="Admin">
      <h2>
        You've successfully logged in as <b>{username}</b>.
      </h2>
    </Layout>
  );
}

export async function getServerSideProps(context) {
  const token = cookies(context)['umami.auth'];

  try {
    const payload = await verifySecureToken(token);

    return {
      props: {
        username: payload.username,
      },
    };
  } catch {
    const { res } = context;

    res.statusCode = 303;
    res.setHeader('Location', '/');
    res.end();
  }

  return { props: {} };
}