Chapter 13 Adapter Pattern

I’m kind of confused as to what we are “Adapting” here. As in, say I wanted to also use the Facebook sign in and created a dummy 3rd party like we did in the playground example.

What would be the best way to do this? Would I also have to create a Legacy Object called FacebookAuthenticator and an adapter called FacebookAuthenticatorAdapter? Or would the better way be to have an adapter just called AuthenticatorAdapter and have some sort of switch case that can identify which type of AuthenticatorAdapter we are passing in that conforms to the AuthenticationService protocol?

@jstrawn Can you please help with this when you get a chance? Thank you - much appreciated! :]