gen-firebase-rewrites.js

// Purpose: Configure Firebase rewrite rules for Next.js static routing.
// This script is intended for statically generated Next.js projects (built with 'next build' and 'next export').
// Inspired by the discussion at: https://github.com/firebase/firebase-js-sdk/discussions/4980

import fsPromises from 'fs/promises';
import path from 'path';
import { fileURLToPath } from 'url';

async function main() {
  const args = process.argv.slice(2); // Get command-line arguments, excluding 'node' and script name
  if (args.length !== 2) {
    console.error('Usage: node script.js <routeManifestFilePath> <firebaseJsonFilePath>');
    return;
  }

  const routeManifestFilePath = args[0];
  const firebaseJsonFilePath = args[1];
  
  console.info(`Using route manifest file: ${routeManifestFilePath}`);
  console.info(`Using Firebase JSON file: ${firebaseJsonFilePath}`);

  try {
    // Read route manifest file
    const routeManifestTxt = await fsPromises.readFile(routeManifestFilePath, 'utf8');
    const routeManifest = JSON.parse(routeManifestTxt);

    // Read Firebase configuration file
    const firebaseJsonTxt = await fsPromises.readFile(firebaseJsonFilePath, 'utf8');
    const firebaseJson = JSON.parse(firebaseJsonTxt);

   const modifiedRoutes = routeManifest.dynamicRoutes.map(({
      page,
      regex,
    }) => {
      const destination = `${page}/index.html`;
      return {
        destination,
        regex,
      };
    });
    
    firebaseJson.hosting.rewrites = modifiedRoutes;
    
    const firebaseJsonModTxt = JSON.stringify(firebaseJson, null, 2);
    
    await fsProm.writeFile(firebaseJsonPath, firebaseJsonModTxt, 'utf8');


  } catch (error) {
    console.error('An error occurred:', error.message);
  }
}

next.config.js

module.exports = {
  images: {
    loader: 'akamai',
    domains: ['firebasestorage.googleapis.com'],
    path: '',
  },
  trailingSlash: true,
};

package.json

{
  "scripts": {
    "dev": "next dev",
    "build": "next build",
    "export": "next export",
    "gen-firebase-rewrites": "node script.js /path/to/routes-manifest.json /path/to/firebase.json",
  },
}