server.mjs

import express from 'express';
import compression from 'compression';
import path from 'path';
import { fileURLToPath } from 'url';
import { readdir } from 'fs/promises';
import serveStatic from 'serve-static';

const __filename = fileURLToPath(import.meta.url);
const __dirname = path.dirname(__filename);

const baseDir = process.env.NODE_ENV === 'production' ? './dist' : './src';
const app = express();

// Gzip compression for all files
app.use(compression());

// Serve static files
// Automatically adds etag and last-modifed headers for conditional requests
app.use(
	'/',
	express.static(path.join(__dirname, baseDir), {
		redirect: false,
		setHeaders: (res, path) => {
			if (serveStatic.mime.lookup(path) === 'text/html') {
				// 2 minute browser cache, 1 minute CDN cache, safe to be cached on CDNs as well, will keep old html file when revalidating or upon a server error
				res.set('Cache-Control', 'public, max-age=120, s-maxage=60, stale-while-revalidate=86400, stale-if-error=86400');
			} else {
				// Cache static assets for 1 year on the browser, 7 days on CDNs and keep old file when revalidating or upon server error
				res.set('Cache-Control', 'public, max-age=31536000, s-maxage=604800, stale-while-revalidate=86400, stale-if-error=86400');
			}
		},
	})
);

// Get all files recursively
async function getFiles(dir) {
	const dirents = await readdir(dir, { withFileTypes: true });
	const files = await Promise.all(
		dirents.map((dirent) => {
			const res = path.resolve(dir, dirent.name);
			return dirent.isDirectory() ? getFiles(res) : res;
		})
	);

	return Array.prototype.concat(...files);
}

// Api route to get all files from baseDir recursively
app.get('/api/files', async (req, res) => {
	try {
		const files = await getFiles(path.join(__dirname, baseDir));
		res.json({
			success: true,
			files: files.map((file) => {
				file = file.replace(path.join(__dirname, baseDir), ''); // Leave relative path
				file = file.replace('index.html', ''); // Fix service worker bug
				return file.replace(/\\/g, '/'); // Turn '\' to '/'
			}),
		});
	} catch (err) {
		res.json({ success: false, error: err });
	}
});

// Start server on port 4000
app.listen(4000, console.log('Server running on http://localhost:4000/'));