Handle UTM params in redirect

bskylink/src/metrics.ts

@@ -11,6 +11,11 @@ type Events = {
     whitelisted: 'unknown' | 'yes'
     blocked: boolean
     warned: boolean
+    utm_source?: string
+    utm_medium?: string
+    utm_campaign?: string
+    utm_content?: string
+    utm_term?: string
   }
   invalid_redirect: {
     link: string

bskylink/src/routes/redirect.ts

@@ -101,6 +101,11 @@ export default function (ctx: AppContext, app: Express) {
         whitelisted,
         blocked,
         warned,
+        utm_source: req.query.utm_source?.toString(),
+        utm_medium: req.query.utm_medium?.toString(),
+        utm_campaign: req.query.utm_campaign?.toString(),
+        utm_content: req.query.utm_content?.toString(),
+        utm_term: req.query.utm_term?.toString(),
       })
 
       return res.end(html)

bskylink/tests/index.ts

@@ -360,4 +360,21 @@ describe('link service no safelink', async () => {
     // No blocked-site div, always safe
     assert.doesNotMatch(html, /"blocked-site"/)
   })
+
+  it('normal redirect with query params', async () => {
+    const urlToRedirect = 'https://bsky.app/settings'
+    const url = new URL(`${baseUrl}/redirect`)
+    url.searchParams.set('u', urlToRedirect)
+    url.searchParams.set('utm_source', 'test')
+    const res = await fetch(url, {redirect: 'manual'})
+    assert.strictEqual(res.status, 200)
+    const html = await res.text()
+    assert.match(html, /meta http-equiv="refresh"/)
+    assert.match(
+      html,
+      new RegExp(urlToRedirect.replace(/[.*+?^${}()|[\]\\]/g, '\\$&')),
+    )
+    // No blocked-site div, always safe
+    assert.doesNotMatch(html, /"blocked-site"/)
+  })
 })