Chrome Headless build

let express = require('express');
let fs = require('fs');
let Chrome = require('chrome-remote-interface');
let spawn = require('child_process').spawn;
let PDFDocument = require('pdfkit');
// The second argument when starting node is the location of the headless_shell binary.
if (process.argv[ 2 ] === undefined) {
  throw Error('No headless binary path provided.');
}

// We need to spawn Chrome headless with some parameters, one of which is the debug port.
// I am hard coding window size because I want the screenshot to be a specific size.
// Note: 1280x1696 is the default pixel resolution for a Letter sheet of paper.
spawn(process.argv[ 2 ], ['--no-sandbox', '--remote-debugging-port=9222','--window-size=1280x1696' ]);

let app = express();

// Just to demonstrate the app working fetch on root of the app causes the PDF to be generated.
app.get('/', (req, res)=> {
  Chrome.New(function () {
    Chrome(chromeInstance => {
      chromeInstance.Page.loadEventFired(takeScreenshot.bind(null, chromeInstance, res, Date.now()));
      chromeInstance.Page.enable();
      chromeInstance.once('ready', ()=> {
        chromeInstance.Page.navigate({url: 'https://addyosmani.com/'});
      })
    });
  });
});


function takeScreenshot(instance, response, startTime) {
  let screenshot = function (v) {
    let filename = `screenshot-${Date.now()}`;
    fs.writeFileSync(filename + '.png', v.data, 'base64');

    console.log(`Image saved as ${filename}.png`);

    let imageEnd = Date.now();

    console.log('image success in: ' + (+imageEnd - +startTime) + "ms");
    // Using PDFKit to create the actual PDF document
    let doc = new PDFDocument({
      margin:0,
      size:'letter'
    });
    // This width is in points not pixels.
    doc.image(filename + '.png', 0,0, {width:612});
    // I wanted the file response to trigger a download rather than loading in the page.
    response.setHeader('Content-Type', 'application/pdf');
    response.setHeader('Content-Disposition', 'attachment; filename=' + filename + '.pdf');
    // Pipe the document into the response and close the stream when it's completed.
    doc.pipe(response);

    let docEnd = Date.now();
    doc.end();

    let endTime = Date.now();
    console.log('pdf success in: ' + (+docEnd - +startTime) + "ms");
    console.log('success in: ' + (+endTime - +startTime) + "ms");
    // Kill the tab we are using to save on memory.
    instance.close();
  };
  // This is the magic here.
  instance.Page.captureScreenshot().then(screenshot);
}

app.listen(3000, function () {
  Chrome.Version().then(version => {
    console.log(version)
  });
  console.log('Export app running on 3000!');
});

FROM ubuntu:16.04

# Install.
RUN \
    apt-get update && \
    apt-get install sudo && \
    sed -i 's/# \(.*multiverse$\)/\1/g' /etc/apt/sources.list && \
    apt-get update && \
    apt-get -y upgrade && \
    apt-get install -y build-essential && \
    apt-get install -y software-properties-common && \
    apt-get install -y byobu curl git htop man unzip vim wget && \
    rm -rf /var/lib/apt/lists/* && \
    curl -sL https://deb.nodesource.com/setup_6.x | sudo -E bash - && \
    sudo apt-get install -y nodejs && \
    sudo apt-get install -y libnss3 && \
    sudo apt-get install -y libgtk2.0-0 libgdk-pixbuf2.0-0 libfontconfig1 libxrender1 libx11-6 libglib2.0-0 libxft2 libfreetype6 libc6 zlib1g libpng12-0 libstdc++6-4.8-dbg-arm64-cross libgcc1

COPY ./node_modules /root/export-app/node_modules
ADD ./app.js /root/export-app/app.js
ADD ./package.json /root/export-app/package.json
ADD ./ChromiumHeadless.tar.gz /root/export-app

WORKDIR /root/export-app

EXPOSE 8080 3000

CMD ["node", "app.js", "/root/export-app/chromium/src/out/Debug/headless_shell"]