How can I get the hosting url instead of functions url in firebase functions for https

If you examine the contents of req.headers, you'll find some attributes of interest:

• host: The host of Cloud Functions, e.g. "us-central1-YOUR-PROJECT.cloudfunctions.net:
• x-forwarded-host: Your Firebase Hosting host, e.g. "YOUR-PROJECT.firebaseapp.com"
• x-forwarded-proto: The protocol of the original request, e.g. "https"
• x-original-url: The URL path of the original request, e.g. "/test"

Between three of those (the ones that start with "x-"), you could concatenate them together to get the original URL.

I don't know if these headers are fully documented and supported.