From bab07f2d725a60b53064ea34697cd8f2b5790d6e Mon Sep 17 00:00:00 2001
From: Daniel Roe <daniel@roe.dev>
Date: Wed, 10 Jun 2026 10:43:02 +0100
Subject: [PATCH] fix: linkify urls in mastodon

---
 .../social/runtime/server/_social/linkify.ts  | 54 +++++++++++++++
 .../runtime/server/_social/mastodon.get.ts    |  4 +-
 test/unit/linkify.spec.ts                     | 67 +++++++++++++++++++
 3 files changed, 124 insertions(+), 1 deletion(-)
 create mode 100644 modules/social/runtime/server/_social/linkify.ts
 create mode 100644 test/unit/linkify.spec.ts

diff --git a/modules/social/runtime/server/_social/linkify.ts b/modules/social/runtime/server/_social/linkify.ts
new file mode 100644
index 00000000..0571b297
--- /dev/null
+++ b/modules/social/runtime/server/_social/linkify.ts
@@ -0,0 +1,54 @@
+const URL_PATTERN
+  = /\b((?:https?:\/\/|www\.)[^\s<]+|(?:[a-z0-9-]+\.)+[a-z]{2,24}\/[^\s<]*)/gi
+
+const TRAILING_PUNCTUATION = /[)\].,;:!?'"]+$/
+
+function balanceTrailing (url: string): { url: string, trailing: string } {
+  let trailing = ''
+  let current = url
+  while (true) {
+    const match = current.match(TRAILING_PUNCTUATION)
+    if (!match) break
+    const candidate = current.slice(0, -match[0].length)
+    const opens = (candidate.match(/\(/g) || []).length
+    const closes = (candidate.match(/\)/g) || []).length
+    if (match[0].includes(')') && opens > closes) break
+    trailing = match[0] + trailing
+    current = candidate
+  }
+  return { url: current, trailing }
+}
+
+function toHref (raw: string): string {
+  if (/^https?:\/\//i.test(raw)) return raw
+  return `https://${raw}`
+}
+
+/**
+ * Wrap bare URLs and domain-like tokens in Mastodon-style HTML with `<a>` tags,
+ * leaving any text already inside an `<a>` element untouched.
+ *
+ * Mastodon only auto-links text that starts with a protocol; references like
+ * `roe.dev/ama` stay as plain text in the rendered `content` field.
+ */
+export function linkifyBareUrls (html: string): string {
+  let result = ''
+  let cursor = 0
+  const anchor = /<a\b[^>]*>[\s\S]*?<\/a>/gi
+  let match: RegExpExecArray | null
+  while ((match = anchor.exec(html))) {
+    result += linkifyText(html.slice(cursor, match.index))
+    result += match[0]
+    cursor = match.index + match[0].length
+  }
+  result += linkifyText(html.slice(cursor))
+  return result
+}
+
+function linkifyText (segment: string): string {
+  if (!segment) return segment
+  return segment.replace(URL_PATTERN, raw => {
+    const { url, trailing } = balanceTrailing(raw)
+    return `<a href="${toHref(url)}">${url}</a>${trailing}`
+  })
+}
diff --git a/modules/social/runtime/server/_social/mastodon.get.ts b/modules/social/runtime/server/_social/mastodon.get.ts
index e512a8bc..415b2cc8 100644
--- a/modules/social/runtime/server/_social/mastodon.get.ts
+++ b/modules/social/runtime/server/_social/mastodon.get.ts
@@ -1,6 +1,8 @@
 import { createRestAPIClient } from 'masto'
 import { parseURL, withProtocol } from 'ufo'
 
+import { linkifyBareUrls } from './linkify'
+
 export default defineEventHandler(async event => {
   const acct = useRuntimeConfig(event).social.networks.mastodon.identifier
 
@@ -49,7 +51,7 @@ export default defineEventHandler(async event => {
           height: m.meta?.original?.height,
           alt: m.description,
         })),
-        html: p.content,
+        html: linkifyBareUrls(p.content),
       })),
   )
 })
diff --git a/test/unit/linkify.spec.ts b/test/unit/linkify.spec.ts
new file mode 100644
index 00000000..b6c3bbe1
--- /dev/null
+++ b/test/unit/linkify.spec.ts
@@ -0,0 +1,67 @@
+import { describe, it, expect } from 'vitest'
+
+import { linkifyBareUrls } from '../../modules/social/runtime/server/_social/linkify'
+
+describe('linkifyBareUrls', () => {
+  it('wraps bare domain references with a link', () => {
+    expect(linkifyBareUrls('<p>roe.dev/ama</p>')).toBe(
+      '<p><a href="https://roe.dev/ama">roe.dev/ama</a></p>',
+    )
+  })
+
+  it('leaves existing anchors untouched', () => {
+    const input = '<p>see <a href="https://roe.dev/ama" class="mention">roe.dev/ama</a> for more</p>'
+    expect(linkifyBareUrls(input)).toBe(input)
+  })
+
+  it('does not double-wrap content inside an anchor that also references another domain', () => {
+    const input = '<p><a href="https://mastodon.roe.dev/tags/ama">roe.dev/ama</a> roe.dev/ama</p>'
+    expect(linkifyBareUrls(input)).toBe(
+      '<p><a href="https://mastodon.roe.dev/tags/ama">roe.dev/ama</a> <a href="https://roe.dev/ama">roe.dev/ama</a></p>',
+    )
+  })
+
+  it('linkifies plain protocol URLs', () => {
+    expect(linkifyBareUrls('visit https://example.com/foo!')).toBe(
+      'visit <a href="https://example.com/foo">https://example.com/foo</a>!',
+    )
+  })
+
+  it('keeps trailing punctuation outside the link', () => {
+    expect(linkifyBareUrls('see roe.dev/ama.')).toBe(
+      'see <a href="https://roe.dev/ama">roe.dev/ama</a>.',
+    )
+    expect(linkifyBareUrls('(see roe.dev/ama)')).toBe(
+      '(see <a href="https://roe.dev/ama">roe.dev/ama</a>)',
+    )
+  })
+
+  it('keeps balanced parentheses inside the link', () => {
+    expect(linkifyBareUrls('see https://en.wikipedia.org/wiki/Foo_(bar) ok')).toBe(
+      'see <a href="https://en.wikipedia.org/wiki/Foo_(bar)">https://en.wikipedia.org/wiki/Foo_(bar)</a> ok',
+    )
+  })
+
+  it('leaves dotted prose like node.js or foo.bar alone (no path)', () => {
+    expect(linkifyBareUrls('<p>node.js and foo.bar are fine</p>')).toBe(
+      '<p>node.js and foo.bar are fine</p>',
+    )
+  })
+
+  it('still linkifies www.-prefixed hosts even without a path', () => {
+    expect(linkifyBareUrls('go to www.example.com today')).toBe(
+      'go to <a href="https://www.example.com">www.example.com</a> today',
+    )
+  })
+
+  it('does not break on empty input', () => {
+    expect(linkifyBareUrls('')).toBe('')
+  })
+
+  it('handles the real-world mastodon post that triggered this', () => {
+    const input = '<p>I&#39;ve always been interested in tech</p><p>roe.dev/ama</p><p><a href="https://mastodon.roe.dev/tags/ama" class="mention hashtag" rel="tag">#<span>ama</span></a></p>'
+    expect(linkifyBareUrls(input)).toBe(
+      '<p>I&#39;ve always been interested in tech</p><p><a href="https://roe.dev/ama">roe.dev/ama</a></p><p><a href="https://mastodon.roe.dev/tags/ama" class="mention hashtag" rel="tag">#<span>ama</span></a></p>',
+    )
+  })
+})
-- 
2.51.2