inline-critical/index.js

/**
 * Module to inline styles while loading the existing stylesheets async
 *
 * @author Ben Zörb @bezoerb https://github.com/bezoerb
 * @copyright Copyright (c) 2014 Ben Zörb
 *
 * Licensed under the MIT license.
 * http://bezoerb.mit-license.org/
 * All rights reserved.
 */

'use strict';

const fs = require('fs');
const path = require('path');
const isString = require('lodash/isString');
const isRegExp = require('lodash/isRegExp');
const reaver = require('reaver');
const slash = require('slash');

const Dom = require('./src/dom');
const {prettifyCss, extractCss} = require('./src/css');

const DEFAULT_OPTIONS = {
  minify: true,
  extract: false,
  polyfill: true,
  ignore: [],
  replaceStylesheets: false,
  noscript: 'body',
};

/**
 * Fixup slashes in file paths for windows
 *
 * @param {string} str Filepath
 * @return {string} Normalized path
 */
function normalizePath(str) {
  return process.platform === 'win32' ? slash(str) : str;
}

/**
 * Main function ;)
 * @param {string} html HTML String
 * @param {string} styles CSS String
 * @param {object} options Options
 * @returns {string} HTML Source with inlined critical css
 */
function inline(html, styles, options) {
  const o = {...DEFAULT_OPTIONS, ...(options || {})};

  if (!isString(html)) {
    html = String(html);
  }

  if (!Array.isArray(o.ignore)) {
    o.ignore = [o.ignore].filter(i => i);
  }

  const document = new Dom(html, o);

  const inlineStyles = document.getInlineStyles();
  const extarnalStyles = document.getExternalStyles();
  const missingStyles = extractCss(styles, ...inlineStyles);

  const links = extarnalStyles.filter(link => {
    // Only take stylesheets
    const stylesheet = link.getAttribute('rel') === 'stylesheet';
    // Filter ignored links
    const href = link.getAttribute('href');
    return stylesheet && !o.ignore.some(i => (isRegExp(i) && i.test(href)) || i === href);
  });

  const targetSelectors = [
    o.selector,
    ':not(noscript) > link[rel="stylesheet"]',
    ':not(noscript) > link[rel="preload"][as="style"]',
    'head script',
  ];

  const target = document.querySelector(targetSelectors);
  const inlined = `${inlineStyles}\n${missingStyles}`;

  if (missingStyles) {
    if (o.minify) {
      document.addInlineStyles(missingStyles, target);
    } else {
      document.addInlineStyles(prettifyCss(missingStyles, document.indent), target);
    }
  }

  if (Array.isArray(o.replaceStylesheets) > 0 && links.length > 0) {
    // Detect links to be removed
    const [ref] = links;
    const removable = [...document.querySelectorAll('link[rel="stylesheet"], link[rel="preload"][as="style"]')].filter(
      link => {
        // Filter ignored links
        const href = link.getAttribute('href');
        return !o.ignore.some(i => (isRegExp(i) && i.test(href)) || i === href);
      }
    );

    // Add link tags before old links
    // eslint-disable-next-line array-callback-return
    o.replaceStylesheets.map(href => {
      const link = document.createElement('link');

      link.setAttribute('rel', 'stylesheet');
      link.setAttribute('href', href);
      document.addNoscript(link);

      link.setAttribute('rel', 'preload');
      link.setAttribute('as', 'style');
      link.setAttribute('onload', "this.onload=null;this.rel='stylesheet'");

      document.insertBefore(link, ref);
    });

    // Remove old links
    // eslint-disable-next-line array-callback-return
    removable.map(link => {
      if (link.parentElement.tagName === 'NOSCRIPT') {
        document.remove(link.parentElement);
      } else {
        document.remove(link);
      }
    });
  } else {
    // Modify links and add clones to noscript block
    // eslint-disable-next-line array-callback-return
    links.map(link => {
      if (o.extract) {
        const href = link.getAttribute('href');
        const file = path.resolve(path.join(o.basePath || process.cwd, href));

        if (fs.existsSync(file)) {
          const orig = fs.readFileSync(file);
          const diff = extractCss(orig, inlined, o.minify);
          const filename = reaver.rev(file, diff);

          fs.writeFileSync(filename, diff);
          link.setAttribute('href', normalizePath(reaver.rev(href, diff)));
        } else if (!/\/\//.test(href)) {
          throw new Error(`Error: file "${href}" not found in "${o.basePath || process.cwd}". Specify base path.`);
        }
      }

      document.addNoscript(link);

      link.setAttribute('rel', 'preload');
      link.setAttribute('as', 'style');
      link.setAttribute('onload', "this.onload=null;this.rel='stylesheet'");
    });
  }

  // Add loadcss if it's not already loaded
  if (o.polyfill) {
    document.maybeAddLoadcss();
  }

  return Buffer.from(document.serialize());
}

module.exports = inline;