mod.ts

import { emojify, htmlEscape, marked, Prism, sanitizeHtml } from "./deps.ts";
import { CSS } from "./style.js";
export { CSS };

class Renderer extends marked.Renderer {
  heading(
    text: string,
    level: 1 | 2 | 3 | 4 | 5 | 6,
    raw: string,
    slugger: marked.Slugger,
  ): string {
    const slug = slugger.slug(raw);
    return `<h${level} id="${slug}"><a class="anchor" aria-hidden="true" tabindex="-1" href="#${slug}"><svg class="octicon octicon-link" viewBox="0 0 16 16" width="16" height="16" aria-hidden="true"><path fill-rule="evenodd" d="M7.775 3.275a.75.75 0 001.06 1.06l1.25-1.25a2 2 0 112.83 2.83l-2.5 2.5a2 2 0 01-2.83 0 .75.75 0 00-1.06 1.06 3.5 3.5 0 004.95 0l2.5-2.5a3.5 3.5 0 00-4.95-4.95l-1.25 1.25zm-4.69 9.64a2 2 0 010-2.83l2.5-2.5a2 2 0 012.83 0 .75.75 0 001.06-1.06 3.5 3.5 0 00-4.95 0l-2.5 2.5a3.5 3.5 0 004.95 4.95l1.25-1.25a.75.75 0 00-1.06-1.06l-1.25 1.25a2 2 0 01-2.83 0z"></path></svg></a>${text}</h${level}>`;
  }

  code(code: string, language: string) {
    // a language of `ts, ignore` should really be `ts`
    language = language.split(",")[0];
    const grammar = Object.hasOwnProperty.call(Prism.languages, language)
      ? Prism.languages[language]
      : undefined;
    if (grammar === undefined) {
      return `<pre><code>${htmlEscape(code)}</code></pre>`;
    }
    const html = Prism.highlight(code, grammar, language);
    return `<div class="highlight highlight-source-${language}"><pre>${html}</pre></div>`;
  }

  link(href: string, title: string, text: string) {
    if (href.startsWith("#")) {
      return `<a href="${href}" title="${title}">${text}</a>`;
    }
    return `<a href="${href}" title="${title}" rel="noopener noreferrer">${text}</a>`;
  }
}

export interface RenderOptions {
  baseUrl?: string;
  allowIframes?: boolean;
}

export function render(markdown: string, opts: RenderOptions = {}): string {
  markdown = emojify(markdown);

  const html = marked(markdown, {
    baseUrl: opts.baseUrl,
    gfm: true,
    renderer: new Renderer(),
  });

  const allowedTags = sanitizeHtml.defaults.allowedTags.concat([
    "img",
    "svg",
    "path",
  ]);
  if (opts.allowIframes) {
    allowedTags.push("iframe");
  }

  return sanitizeHtml(html, {
    allowedTags,
    allowedAttributes: {
      ...sanitizeHtml.defaults.allowedAttributes,
      img: ["src", "alt", "height", "width", "align"],
      a: ["id", "aria-hidden", "href", "tabindex", "rel"],
      svg: ["viewbox", "width", "height", "aria-hidden"],
      path: ["fill-rule", "d"],
      h1: ["id"],
      h2: ["id"],
      h3: ["id"],
      h4: ["id"],
      h5: ["id"],
      h6: ["id"],
      iframe: ["src", "width", "height"], // Only used when iframe tags are allowed in the first place.
    },
    allowedClasses: {
      div: ["highlight"],
      span: [
        "token",
        "keyword",
        "operator",
        "number",
        "boolean",
        "function",
        "string",
        "comment",
        "class-name",
        "regex",
        "regex-delimiter",
        "tag",
        "attr-name",
        "punctuation",
        "script-punctuation",
        "script",
        "plain-text",
      ],
      a: ["anchor"],
      svg: ["octicon", "octicon-link"],
    },
    allowProtocolRelative: false,
  });
}