A bio is markdown, on stricter rules than the site's own

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GT37Z1Xtfd9pUuQtMTg6Yt

src/app.rs

@@ -2553,7 +2553,12 @@ fn AnswerCard(answer: Answer, picture: String, link: Option<RowLink>) -> impl In
             <img class="answer-picture" src=picture alt=heading.clone() loading="lazy" />
             <div class="answer-card-text">
                 <h4 class="answer-card-heading">{heading}</h4>
-                {rest.into_iter().map(|t| view! { <p>{t}</p> }).collect_view()}
+                // What the person wrote, as they wrote it: markdown, on
+                // the stricter rules for text that is not the site's.
+                {rest
+                    .into_iter()
+                    .map(|t| view! { <div class="card-field" inner_html=crate::content::render_written_markdown(&t)></div> })
+                    .collect_view()}
             </div>
             {link.map(|(href, label)| view! { <a class="answer-link" href=href>{label}</a> })}
         </article>

src/content/markdown.rs

@@ -118,3 +118,67 @@ pub(crate) fn rewrite_img_tag(tag: &str) -> String {
     cleaned.replacen("<img", &format!("<img{attrs}"), 1)
 }
 
+
+/// Markdown that a person wrote into a record - a bio on a card - as
+/// opposed to the site's own content. Paragraphs, line breaks as they
+/// were typed, lists, emphasis and links; no images (a picture has its
+/// own field, and an image in text is a way to load something from
+/// elsewhere into every visitor's page), no raw HTML, headings as plain
+/// paragraphs. Links go to https, mailto or tel only, and say they are
+/// the writer's, not the site's (`rel="nofollow ugc"`).
+pub fn render_written_markdown(text: &str) -> String {
+    use pulldown_cmark::{html, Event, Options, Parser, Tag, TagEnd};
+    let parser = Parser::new_ext(text, Options::ENABLE_STRIKETHROUGH);
+    let mut in_dropped_link = 0usize;
+    let mut in_image = 0usize;
+    let filtered = parser.filter_map(|event| match event {
+        Event::Html(_) | Event::InlineHtml(_) => None,
+        Event::Start(Tag::Image { .. }) => {
+            in_image += 1;
+            None
+        }
+        Event::End(TagEnd::Image) => {
+            in_image = in_image.saturating_sub(1);
+            None
+        }
+        _ if in_image > 0 => None,
+        Event::Start(Tag::Heading { .. }) => Some(Event::Start(Tag::Paragraph)),
+        Event::End(TagEnd::Heading(_)) => Some(Event::End(TagEnd::Paragraph)),
+        // What someone typed on a new line is on a new line.
+        Event::SoftBreak => Some(Event::HardBreak),
+        Event::Start(Tag::Link { dest_url, .. })
+            if !(dest_url.starts_with("https://") || dest_url.starts_with("mailto:") || dest_url.starts_with("tel:")) =>
+        {
+            in_dropped_link += 1;
+            None
+        }
+        Event::End(TagEnd::Link) if in_dropped_link > 0 => {
+            in_dropped_link -= 1;
+            None
+        }
+        other => Some(other),
+    });
+    let mut out = String::new();
+    html::push_html(&mut out, filtered);
+    out.trim().replace("<a href=", "<a rel=\"nofollow ugc\" href=")
+}
+
+#[cfg(test)]
+mod written_tests {
+    use super::render_written_markdown as md;
+
+    #[test]
+    fn a_bio_keeps_what_a_person_would_write_and_nothing_that_reaches_out() {
+        assert_eq!(md("Line one\nline two"), "<p>Line one<br />\nline two</p>");
+        assert!(md("- NS 3424\n- NS 3423").contains("<ul>\n<li>NS 3424</li>"));
+        assert!(md("**Sivilingeniør**, *NTNU*").contains("<strong>Sivilingeniør</strong>, <em>NTNU</em>"));
+        assert_eq!(md("[Westra](https://westra.no)"), "<p><a rel=\"nofollow ugc\" href=\"https://westra.no\">Westra</a></p>");
+        // Everything that would put something else in the page is gone.
+        assert_eq!(md("<script>alert(1)</script>"), "");
+        assert_eq!(md("hi <img src=x onerror=alert(1)>"), "<p>hi </p>");
+        assert_eq!(md("[click](javascript:alert(1))"), "<p>click</p>");
+        assert_eq!(md("[home](/kontor)"), "<p>home</p>", "a site path is the site's to link, not a bio's");
+        assert_eq!(md("before ![pixel](https://tracker.example/p.gif) after"), "<p>before  after</p>");
+        assert_eq!(md("# Shouting"), "<p>Shouting</p>");
+    }
+}