Custom Next.js server.js with purge cache handler.

server.js

// server.js

const { createServer } = require('http');
const next = require('next');
const { promises, existsSync  } = require('fs');

const dev = (process.env.NODE_ENV || '').indexOf('production') === -1;

const app = next({ dev });
const handle = app.getRequestHandler();

const purgeData = async (pathname) => {
    const fullPathname = `.next/server/pages${pathname}`;
    const fullPathHTML = `${fullPathname}.html`;
    const fullPathJSON = `${fullPathname}.json`;
    try {
        if (existsSync(fullPathHTML)) {
            await promises.unlink(fullPathHTML);
            console.info(`Deleted ${fullPathHTML}`);
        }
        if (existsSync(fullPathJSON)) {
            await promises.unlink(fullPathJSON);
            console.info(`deleted ${fullPathJSON}`);
        }
        
        /* Delete the entry in cache */
        app.server.incrementalCache.cache.del(pathname);
        console.log(`Cache of ${fullPathname} was successfully purged`);
    } catch (err) {
        console.error(`Could not purge cache of ${fullPathname} - ${err}`);
    }
}

app.prepare().then(() => {
    createServer((req, res) => {
        const url = new URL(req.url, "http://localhost:3000/");
        if (url.searchParams.get('purge') == '1') {
            /* Handle incoming request after purge the cache */
            purgeData(url.pathname).then(r => handle(req, res));
        }else {
            /* Handle incoming request without purge the cache */
            handle(req, res)
        }
    }).listen(3000, (err) => {
        if (err) throw err;
        console.log(`> Ready on http://localhost:3000/`);
    })
})