app/assets/javascripts/content_editor/services/asset_resolver.js


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import { memoize } from 'lodash';

const parser = new DOMParser();

export default class AssetResolver {
  constructor({ renderMarkdown }) {
    this.renderMarkdown = renderMarkdown;
  }

  resolveUrl = memoize(async (canonicalSrc) => {
    const html = await this.renderMarkdown(`[link](${canonicalSrc})`);
    if (!html) return canonicalSrc;

    const { body } = parser.parseFromString(html, 'text/html');
    return body.querySelector('a').getAttribute('href');
  });

  resolveReference = memoize(async (originalText) => {
    const text = originalText.replace(/(\+|\+s)$/, '');
    const toRender = `${text} ${text}+ ${text}+s`;
    const html = await this.renderMarkdown(toRender);

    if (!html) return {};

    const { body } = parser.parseFromString(html, 'text/html');
    const a = body.querySelectorAll('a');
    if (!a.length) return {};

    return {
      href: a[0].getAttribute('href'),
      text: a[0].textContent,
      expandedText: a[1].textContent,
      fullyExpandedText: a[2].textContent,
    };
  });

  renderDiagram = memoize(async (code, language) => {
    const backticks = '`'.repeat(4);
    const html = await this.renderMarkdown(`${backticks}${language}\n${code}\n${backticks}`);

    const { body } = parser.parseFromString(html, 'text/html');
    const img = body.querySelector('img');
    if (!img) return '';

    return img.dataset.src || img.getAttribute('src');
  });
}