My app is using its internal registration system for users to signup and login…
I am now checking out the idea of integrating Facebook Connect into my app but i have come to a situation that i think i need some sort of help…
So users in my app upon registration have to select a username and email address which are unique.
What will happen if a user tries to connect via Facebook and that user already exists? their email for example? or what will happen if that user doesnt have a username? can i show them error messages depending in their situation?
Also if the user doesnt have a username on facebook but has an email address that is not registered in my system do i have to show them a new inputfield for them to type in their username before they can access the website further?
All of these scenarios have been explained in registration flows, specifically
My site uses Facebook and my own Registration