asciidoctor-prism-extension/index.js

Highlight Asciidoc code listings with Prism.js, server side, with no front-end dependencies.

'use strict';

const {readFileSync} = require('fs');
const {join, dirname} = require('path');
const Prism = require('prismjs');
const loadLanguages = require('prismjs/components/index.js');

Prism.hooks.add('before-tokenize', (env) => {
  env.code = env.code.replace(/<b class="conum">\((\d+)\)<\/b>/gi, '____$1____');
});

// available list of themes: https://github.com/PrismJS/prism/tree/master/themes
const DEFAULT_THEME = 'prism.css';

// css, markup (html, xml, css, svg) and javascript are loaded by default
const DEFAULT_LANGUAGES = [
  'asciidoc',
  'bash',
  'json',
  'markdown',
  'typescript',
  'yaml',
].join(',');

const getDocumentLanguages = (document) => {
  return (document.getAttribute('prism-languages') || DEFAULT_LANGUAGES)
    .split(',')
    .map(lang => lang.trim());
};

const PrismExtension = {
  initialize (name, backend, {document}) {
    const languages = getDocumentLanguages(document);

    loadLanguages(languages);

    this.backend = backend;
    this.theme = document.hasAttribute('prism-theme') ? document.getAttribute('prism-theme') || DEFAULT_THEME : null;
    this.languages = languages;

    this.super();
  },

  format (node, lang) {
    node.removeSubstitution('specialcharacters');
    node.removeSubstitution('specialchars');

    if (lang && Prism.languages[lang] === undefined) {
      const {languages} = this;
      const source = node.lines.join('\n');
      throw TypeError(`Prism language ${lang} is not loaded (loaded: ${languages}).\n${source}`);
    }

    return `<pre class="highlight highlight-prismjs prismjs language-${lang}"><code class="language-${lang}" data-lang="${lang}">${node.getContent()}</code></pre>`;
  },

  highlight (node, content, lang) {
    return lang
      ? Prism.highlight(
          content, Prism.languages[lang]
        ).replace(/____(\d+)____/gi, '<b class="conum">($1)</b>')
      : content;
  },

  handlesHighlighting () {
    return true;
  },

  hasDocinfo() {
    return true;
  },

  docinfo (location, doc) {
    if (!doc.isBasebackend('html')) {
      return '';
    }

    const {theme} = this;

    if (!theme) {
      return '';
    }

    const prism_folder = dirname(require.resolve('prismjs'));
    const theme_location = join(prism_folder, 'themes', theme);
    const output = readFileSync(theme_location);

    return `<style type="text/css" class="prism-theme">${output}</style>`;
  }
}

module.exports = PrismExtension
module.exports.register = function register (registry) {
  const AsciidoctorModule = registry.$$base_module
  const SyntaxHighlighterRegistry = AsciidoctorModule.$$['SyntaxHighlighter']
  SyntaxHighlighterRegistry.register('prism', PrismExtension)
}