Playground.swift

import Foundation

protocol UserProvider {
    func logIn(onSuccess: (User) -> (), onFailure: (Error) -> ())
}

protocol UserRepositoryProtocol {
    
}

struct User {
    
}

enum LoginType {
    case mail(String)
    case facebook
}

class EmailUserProvider: UserProvider {
    
    func logIn(onSuccess: (User) -> (), onFailure: (Error) -> ()) {
        // TODO: implementation
        print("Logged in with email")
        onSuccess(User())
    }
    
}

class FacebookUserProvider: UserProvider {
    func logIn(onSuccess: (User) -> (), onFailure: (Error) -> ()) {
        print("Logged in with facebook")
        onSuccess(User())
    }
}

class UserRepository {
    
    fileprivate let _emailUserRepository: EmailUserProvider
    fileprivate let _facebookUserRepository: FacebookUserProvider
    
    init(emailUserRepository: EmailUserProvider = EmailUserProvider(),
         facebookUserRepository: FacebookUserProvider = FacebookUserProvider()) {
        _emailUserRepository = EmailUserProvider()
        _facebookUserRepository = FacebookUserProvider()
    }
    
    func logIn(
        with loginType: LoginType,
        onSuccess: (User) -> (),
        onFailure: (Error) -> ()
    ) {
        switch loginType {
        case .facebook:
            _facebookUserRepository.logIn(onSuccess: onSuccess, onFailure: onFailure)
        case .mail(let email):
            _emailUserRepository.logIn(onSuccess: onSuccess, onFailure: onFailure)
        }
    }
    
}

let userRepository = UserRepository()

userRepository.logIn(with: .mail("hola@hotmail.com"), onSuccess: { _ in }, onFailure: { _ in })
userRepository.logIn(with: .facebook, onSuccess: { _ in }, onFailure: { _ in })