Pass referrer on native (with an opt out) (#6648)

* Pass referer on native

* Add ChainLink3

* Add an opt out for sending utm

* Remove noreferrer on links

We do have <meta name="referrer" content="origin-when-cross-origin"> in HTML, should be sufficient.

* Narrow down the condition slightly

---------

Co-authored-by: Eric Bailey <git@esb.lol>

src/lib/hooks/useOpenLink.ts

@@ -4,12 +4,14 @@ import * as WebBrowser from 'expo-web-browser'
 
 import {
   createBskyAppAbsoluteUrl,
+  isBskyAppUrl,
   isBskyRSSUrl,
   isRelativeUrl,
 } from '#/lib/strings/url-helpers'
 import {isNative} from '#/platform/detection'
 import {useModalControls} from '#/state/modals'
 import {useInAppBrowser} from '#/state/preferences/in-app-browser'
+import {useOptOutOfUtm} from '#/state/preferences/opt-out-of-utm'
 import {useTheme} from '#/alf'
 import {useSheetWrapper} from '#/components/Dialog/sheet-wrapper'
 
@@ -18,6 +20,7 @@ export function useOpenLink() {
   const enabled = useInAppBrowser()
   const t = useTheme()
   const sheetWrapper = useSheetWrapper()
+  const optOutOfUtm = useOptOutOfUtm()
 
   const openLink = useCallback(
     async (url: string, override?: boolean) => {
@@ -26,6 +29,9 @@ export function useOpenLink() {
       }
 
       if (isNative && !url.startsWith('mailto:')) {
+        if (!optOutOfUtm && !isBskyAppUrl(url) && url.startsWith('http')) {
+          url = addUtmSource(url)
+        }
         if (override === undefined && enabled === undefined) {
           openModal({
             name: 'in-app-browser-consent',
@@ -47,8 +53,24 @@ export function useOpenLink() {
       }
       Linking.openURL(url)
     },
-    [enabled, openModal, t, sheetWrapper],
+    [enabled, openModal, t, sheetWrapper, optOutOfUtm],
   )
 
   return openLink
 }
+
+function addUtmSource(url: string): string {
+  let parsedUrl
+  try {
+    parsedUrl = new URL(url)
+  } catch (e) {
+    return url
+  }
+  if (!parsedUrl.searchParams.has('utm_source')) {
+    parsedUrl.searchParams.set('utm_source', 'bluesky')
+    if (!parsedUrl.searchParams.has('utm_medium')) {
+      parsedUrl.searchParams.set('utm_medium', 'social')
+    }
+  }
+  return parsedUrl.toString()
+}