fastify-prerender-plugin/dist/index.mjs

Prerender SPA pages for bots

import Crypto from 'node:crypto';
import Fs from 'node:fs';
import Path from 'node:path';
import { fastifyPlugin } from 'fastify-plugin';
import { isbot } from 'isbot';
import sanitize from 'sanitize-filename';
import tmp from 'tmp';
import { fileURLToPath } from 'node:url';
import { isMainThread, workerData, parentPort, Worker } from 'node:worker_threads';
import { lightpanda } from '@lightpanda/browser';

async function requestFromBrowser(url) {
  return new Promise((resolve, reject) => {
    const worker = new Worker(fileURLToPath(import.meta.url), {
      workerData: { url }
    });
    worker.on("message", resolve);
    worker.on("error", reject);
  });
}
if (!isMainThread) {
  const options = {
    dump: true,
    disableHostVerification: false
  };
  lightpanda.fetch(workerData.url, options).then((response) => {
    parentPort?.postMessage(response.toString());
  });
}

const prerenderPlugin = fastifyPlugin(
  (app, options, done) => {
    const tmpobj = tmp.dirSync();
    app.addHook("onRequest", async (request, reply) => {
      const userAgent = request.headers["user-agent"] ?? "";
      if (userAgent.startsWith("Lightpanda/")) {
        return;
      }
      const requestFromBot = isbot(userAgent) || userAgent.toLowerCase().startsWith("facebookexternalhit") || userAgent.toLowerCase().startsWith("whatsapp") || userAgent.toLowerCase().startsWith("twitterbot");
      if (!requestFromBot || request.method !== "GET") {
        return;
      }
      request.log.info({ requestFromBot });
      let matches = false;
      const requestPathname = request.url.split("?")[0];
      for (const url2 of options.urls) {
        if (typeof url2 === "string") {
          if (url2 === requestPathname) {
            matches = true;
            break;
          }
        } else {
          if (url2.test(request.url)) {
            matches = true;
            break;
          }
        }
      }
      if (!matches) {
        return;
      }
      const url = `http://${options.host ?? "localhost"}:${options.port}${request.url}`;
      const urlObj = new URL(url);
      const pathname = sanitize(urlObj.pathname.replace(/\//g, "_"));
      const queryString = urlObj.search;
      let filename = pathname || "index";
      if (queryString) {
        const queryHash = Crypto.createHash("md5").update(queryString).digest("hex");
        filename = `${filename}_${queryHash}`;
      }
      filename = `${filename}.html`;
      const filepath = Path.join(options.tmpPath ?? tmpobj.name, filename);
      if (Fs.existsSync(filepath)) {
        const fileStat = Fs.statSync(filepath);
        const fileAgeInMinutes = (Date.now() - fileStat.mtime.getTime()) / 1e3 / 60;
        if (fileAgeInMinutes <= 5) {
          return reply.status(200).type("text/html").send(Fs.readFileSync(filepath));
        }
        Fs.rmSync(filepath);
      }
      request.log.info(`request-from-browser: ${url}`);
      const html = await requestFromBrowser(url).catch((error) => {
        console.error(error);
      }) ?? "";
      try {
        Fs.writeFileSync(filepath, html);
      } catch (_error) {
        request.log.error(`Couldn't write cache in ${filepath}`);
      }
      reply.status(200).type("text/html").send(html);
    });
    done();
  },
  {
    fastify: "^5.x",
    name: "fastify-prerender"
  }
);

export { prerenderPlugin, requestFromBrowser };