We have an app that uses Facebook SDK for logging in.  

We support **iOS 6 native login, with fallback to Facebook App and Safari.**

We're adding Twitter support soon.  

We also want to implement iOS 6 login with Safari fallback for it.

Is there any code in Xamarin.Auth or Xamarin.Social that we can reuse, or do we need to write it from scratch? We need to be able to retrieve access tokens, store them and authenticate requests.

I tried writing my own authenticator for Xamarin.Auth, but its design insists I provide a view controller for authentication, whereas I need to either show iOS 6 auth dialog, or Safari.