process-path.js

const csso = require('csso');
const { promisify } = require('util');
const { readFile } = require('fs');
const { join } = require('path');
const { minify } = require('html-minifier');
const delay = require('delay2');
const getMinimalCss = require('./min-css');
const addCSP = require('./add-csp');
const { minify: minifyJs } = require('uglify-js');
const {
  getLinksOnPage, removeEmptyStyleTags, getLintResults,
  preloadifyScripts, preloadifyStylesheets, preloadifyFonts
} = require('./in-browser-scripts');

const [scriptLoader, stylesheetLoader] = [
  'script-loader-stub.js',
  'style-loader-stub.js'
].map(f => promisify(readFile)(join(__dirname, f)));

const minifierOptions = {
  collapseWhitespace: true,
  collapseBooleanAttributes: true,
  removeAttributeQuotes: true,
  removeRedundantAttributes: true,
  removeScriptTypeAttribute: true,
  removeStyleLinkTypeAttributes: true,
  sortAttributes: true
};

const wrapScripts = str => `window.addEventListener('load', function(){${str}});`;

module.exports = async ({ browser, path, config }) => {
  const page = await browser.newPage();

  page.evaluateOnNewDocument(() => {
    window.SNAPSHOT = true; // eslint-disable-line no-undef
  });

  await page.setBypassCSP(true);
  await page.goto(path);
  await delay(50);

  if(config.printConsoleLogs) {
    page.on('console', msg => {
      for (let i = 0; i < msg.args.length; ++i) {
        console.log(`[browser-console] - ${path} - ${i}: ${msg.args[i]}`);
      }
    });
  }

  const scriptsToInsert = [];

  if(config.inlineCSS || config.preloadFonts) {
    const { css, fonts } = await getMinimalCss(page);

    if(config.inlineCSS) {
      const minimalStyles = csso.minify(css).css;
      await addCSP(page, 'style-src', minimalStyles, config);
      await page.addStyleTag({ content: minimalStyles });

      const stylesheetCount = await preloadifyStylesheets(page);
      if(stylesheetCount) scriptsToInsert.push(stylesheetLoader);
    }

    if(config.preloadFonts) {
      await preloadifyFonts(page, fonts);
    }
  }

  if(config.preloadScripts) {
    await preloadifyScripts(page);
    scriptsToInsert.push(scriptLoader);
  }

  if(scriptsToInsert.length) {
    const scriptContents = minifyJs(
      wrapScripts((await Promise.all(scriptsToInsert)).join('\n'))
    ).code;

    await addCSP(page, 'script-src', scriptContents, config);
    await page.addScriptTag({ content: scriptContents });
  }

  await removeEmptyStyleTags(page);

  const [ markup, links ] = await Promise.all([
    minify(await page.content(), minifierOptions),
    getLinksOnPage(page)
  ]);

  const lint = await getLintResults(page);

  await page.close();

  return { markup, links, lint };
};