next.config.js

/** @type {import('next').NextConfig} */
const runtimeCaching = require('next-pwa/cache');
const withPWA = require('next-pwa')({
  dest: 'public',
  register: true,
  skipWaiting: true,
  disable: process.env.NODE_ENV === 'development'
});

module.exports = withPWA({
  // future: {
  //   webpack5: true,
  //   strictPostcssConfiguration: true
  // },
  reactStrictMode: true,
  // experimental: {
  //   turboMode: true,
  //   eslint: true
  // },
  // async redirects() {
  //   return [
  //     {
  //       source: '/:version/:book',
  //       destination: '/:version/:book/1',
  //       permanent: false
  //     }
  //   ];
  // },
  async headers() {
    return [
      {
        source: '/(.*)',
        headers: securityHeaders
      }
    ];
  }
  // webpack: (config, { dev, isServer }) => {
  //   if (isServer) {
  //     require('./scripts/generate-sitemap');
  //   }

  //   // Replace React with Preact only in client production build
  //   if (!dev && !isServer) {
  //     Object.assign(config.resolve.alias, {
  //       react: 'preact/compat',
  //       'react-dom/test-utils': 'preact/test-utils',
  //       'react-dom': 'preact/compat'
  //     });
  //   }

  //   return config;
  // }
});

// https://securityheaders.com
// const ContentSecurityPolicy = `
//   default-src 'self';
//   script-src 'self' 'unsafe-eval' 'unsafe-inline' *.youtube.com *.twitter.com cdn.usefathom.com;
//   child-src *.youtube.com *.google.com *.twitter.com;
//   style-src 'self' 'unsafe-inline' *.googleapis.com;
//   img-src * blob: data:;
//   media-src 'none';
//   connect-src *;
//   font-src 'self';
//   `;

const securityHeaders = [
  // https://developer.mozilla.org/en-US/docs/Web/HTTP/CSP
  // {
  //   key: 'Content-Security-Policy',
  //   value: ContentSecurityPolicy.replace(/\n/g, '')
  // },
  // https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Referrer-Policy
  {
    key: 'Referrer-Policy',
    value: 'origin-when-cross-origin'
  },
  // https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Frame-Options
  {
    key: 'X-Frame-Options',
    value: 'DENY'
  },
  // https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Content-Type-Options
  {
    key: 'X-Content-Type-Options',
    value: 'nosniff'
  },
  // https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-DNS-Prefetch-Control
  {
    key: 'X-DNS-Prefetch-Control',
    value: 'on'
  },
  // https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Strict-Transport-Security
  {
    key: 'Strict-Transport-Security',
    value: 'max-age=31536000; includeSubDomains; preload'
  },
  // https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Feature-Policy
  // Opt-out of Google FLoC: https://amifloced.org/
  {
    key: 'Permissions-Policy',
    value: 'camera=(), microphone=(), geolocation=(), interest-cohort=()'
  }
];