index.js

const express = require('express');
const portfinder = require('portfinder');
const { render } = require('url-to-pdf-api/src/core/render-core.js');
const { Storage } = require("@google-cloud/storage");
const storage = new Storage({});

const getImage = async (path, bucketName) => storage.bucket(bucketName).file(path).createReadStream();

const streamImage = async (path, imageId, bucketName, res) => {
  res.set('Content-Type', 'image/jpg');
  res.set('Content-Disposition', 'attachment;filename=' + imageId);
  await getImage(path, bucketName).pipe(res);
}

const store = (inspectionId, pdf, bucketName) => storage.bucket(bucketName).file(`inspection/${inspectionId}/report.pdf`).save(pdf);

const generate = async ({ data }) => {
  # get the report in json
  const report = JSON.parse(Buffer.from(data, "base64").toString());
  
  # configure express 
  const app = express();
  app.use('/api/inspections/:inspectionId/images/:imageId', ({ params: { inspectionId, imageId } }, res) =>
    streamImage(`inspection/${inspectionId}/${imageId}`, imageId, process.env.IMAGE_BUCKET, res));
  app.use('/api/inspections/:inspectionId/report', (req, res) => res.json(report));
  app.use(express.static('www'));

  # find an available port
  const port = await portfinder.getPortPromise();
  return new Promise((resolve) => {
    const server = app.listen(port, async () => {
      try {
        const id = report.id;

        const pdf = await render({
          url: `http://localhost:${port}#/report/${id}`,
          goto: { timeout: 0 }, # I don't remember why I needed this :P
          emulateScreenMedia: false # use @media print to display the web page
        });

        await store(id, pdf, process.env.REPORT_BUCKET);

        resolve(pdf);
      } catch (e) {
        console.error(e);
        throw e;
      } finally {
        server.close();
      }
    });
  });
};

exports.run = arg => generate(arg).catch(e => console.error(e));

package.json

{
  "name": "pdf-report-generator",
  "main": "index.js",
  "version": "1.°.0",
  "private": true,
  "keywords": [],
  "author": "",
  "license": "UNLICENSED",
  "dependencies": {
    "@google-cloud/storage": "^4.7.0",
    "express": "^4.17.1",
    "portfinder": "^1.0.26",
    "url-to-pdf-api": "git+https://github.com/alvarcarto/url-to-pdf-api.git"
  }
}