fix(post form): block temporary media links

src/lib/utils/__tests__/url-utils.test.ts

@@ -10,6 +10,7 @@ vi.mock('../clipboard-utils', () => ({
 
 import {
   copyShareLinkToClipboard,
+  getExpiringMediaLinkHostname,
   getHostname,
   getPublishURLFilename,
   is5chanLink,
@@ -62,6 +63,15 @@ describe('url-utils', () => {
     expect(getPublishURLFilename('not-a-url')).toBeNull();
   });
 
+  it('detects publish media hosts with temporary links', () => {
+    expect(getExpiringMediaLinkHostname('https://i.4cdn.org/gif/1712345678900.jpg')).toBe('i.4cdn.org');
+    expect(getExpiringMediaLinkHostname('http://litterbox.catbox.moe/u/example.png')).toBe('litterbox.catbox.moe');
+    expect(getExpiringMediaLinkHostname('https://www.tmpfiles.org/dl/123/file.mp4')).toBe('tmpfiles.org');
+    expect(getExpiringMediaLinkHostname('https://cdn.file.kiwi/example')).toBe('file.kiwi');
+    expect(getExpiringMediaLinkHostname('https://example.com/file.png')).toBeNull();
+    expect(getExpiringMediaLinkHostname('not-a-url')).toBeNull();
+  });
+
   it('copies share links for threads and catalog pages using the production fallback base url', async () => {
     await copyShareLinkToClipboard('music.eth', 'thread', 'cid-123');
     expect(testState.copyToClipboardMock).toHaveBeenCalledWith('https://5chan.app/#/music.eth/thread/cid-123');

src/lib/utils/media-link-validation-utils.ts

@@ -0,0 +1,8 @@
+import { getExpiringMediaLinkHostname } from './url-utils';
+
+type TranslateFn = (key: string, options?: Record<string, unknown>) => string;
+
+export const getExpiringMediaLinkAlert = (url: string, t: TranslateFn): string | null => {
+  const expiringMediaLinkHostname = getExpiringMediaLinkHostname(url);
+  return expiringMediaLinkHostname ? `${t('error')}: ${t('expiring_media_link_alert', { domain: expiringMediaLinkHostname })}` : null;
+};

src/lib/utils/url-utils.ts

@@ -67,6 +67,41 @@ export const normalizePublishURL = (url: string) => {
   return trimmedUrl;
 };
 
+const EXPIRING_MEDIA_LINK_HOSTNAMES = [
+  // 4chan CDN media disappears when threads are pruned, usually after a few hours or days.
+  'i.4cdn.org',
+  // Litterbox temporary uploads can expire after 1 hour, 12 hours, 1 day, or 3 days.
+  'litterbox.catbox.moe',
+  // tmpfiles.org uploads expire after 60 minutes, 6 hours, 12 hours, or 24 hours.
+  'tmpfiles.org',
+  // Filebin uploads are deleted automatically after about 6 days.
+  'filebin.net',
+  // temp.sh files expire after 3 days.
+  'temp.sh',
+  // Termbin pastes are automatically deleted after 1 week.
+  'termbin.com',
+  // Uguu files expire after 3 hours.
+  'uguu.se',
+  // file.kiwi encrypted files are deleted after about 4 days by default.
+  'file.kiwi',
+] as const;
+
+const normalizeHostnameForMatching = (hostname: string) => hostname.toLowerCase().replace(/^www\./, '');
+
+export const getExpiringMediaLinkHostname = (url: string): string | null => {
+  try {
+    const parsedUrl = new URL(normalizePublishURL(url));
+    if (parsedUrl.protocol !== 'https:') {
+      return null;
+    }
+
+    const hostname = normalizeHostnameForMatching(parsedUrl.hostname);
+    return EXPIRING_MEDIA_LINK_HOSTNAMES.find((expiringHostname) => hostname === expiringHostname || hostname.endsWith(`.${expiringHostname}`)) || null;
+  } catch {
+    return null;
+  }
+};
+
 export const isValidPublishURL = (url: string) => {
   try {
     return new URL(normalizePublishURL(url)).protocol === 'https:';