fix: improve turndown config for GFM support and custom styles

Author: sumitdahal7

frontend/package.json

@@ -71,6 +71,7 @@
     "terra-draw": "^1.18.1",
     "tributejs": "^5.1.3",
     "turndown": "^7.2.4",
+    "turndown-plugin-gfm": "^1.0.2",
     "use-query-params": "^2.2.1",
     "webfontloader": "^1.6.28",
     "workbox-core": "^7.0.0",

frontend/src/utils/htmlFromMarkdown.js

@@ -1,6 +1,7 @@
 import { marked } from 'marked';
 import DOMPurify from 'dompurify';
 import TurndownService from 'turndown';
+import { gfm } from 'turndown-plugin-gfm';
 
 const VIDEO_TAG_REGEXP = new RegExp(/^::youtube\[(.*)\]$/);
 
@@ -104,7 +105,37 @@ export const formatUserNamesToLink = (text) => {
   return text;
 };
 
-const turndownService = new TurndownService();
+const turndownService = new TurndownService({
+  headingStyle: 'atx',
+  codeBlockStyle: 'fenced',
+  hr: '---',
+  bullet: '-',
+});
+turndownService.use(gfm);
+
+// Rule to convert YouTube iframes back to ::youtube[id] syntax
+turndownService.addRule('youtube', {
+  filter: (node) => {
+    return (
+      node.nodeName === 'IFRAME' &&
+      node.getAttribute('src')?.startsWith('https://www.youtube.com/embed/')
+    );
+  },
+  replacement: (content, node) => {
+    const src = node.getAttribute('src');
+    const id = src.split('/').pop();
+    return `\n\n::youtube[${id}]\n\n`;
+  },
+});
+
+// Rule to use double tildes for strikethrough
+turndownService.addRule('strikethrough', {
+  filter: ['del', 's', 'strike'],
+  replacement: (content) => `~~${content}~~`,
+});
+
+// Rule to keep other iframes
+turndownService.keep(['iframe']);
 
 export const markdownFromHtml = (html) => {
   return turndownService.turndown(html);

frontend/yarn.lock

@@ -14107,6 +14107,11 @@ tsutils@^3.21.0:
   dependencies:
     tslib "^1.8.1"
 
+turndown-plugin-gfm@^1.0.2:
+  version "1.0.2"
+  resolved "https://registry.yarnpkg.com/turndown-plugin-gfm/-/turndown-plugin-gfm-1.0.2.tgz#6f8678a361f35220b2bdf5619e6049add75bf1c7"
+  integrity sha512-vwz9tfvF7XN/jE0dGoBei3FXWuvll78ohzCZQuOb+ZjWrs3a0XhQVomJEb2Qh4VHTPNRO4GPZh0V7VRbiWwkRg==
+
 turndown@^7.2.4:
   version "7.2.4"
   resolved "https://registry.yarnpkg.com/turndown/-/turndown-7.2.4.tgz#42d98202aefa8c188c997b586bc6da78bdf27ea2"