Refactor first_or_create_for_auth & its usage

Conflicts:
	app/controllers/users/omniauth_callbacks_controller.rb

Refactors first_or_initialize_for_oauth

app/controllers/users/omniauth_callbacks_controller.rb

@@ -1,23 +1,15 @@
 class Users::OmniauthCallbacksController < Devise::OmniauthCallbacksController
 
-  def self.provides_callback_for(provider)
-    class_eval %Q{
-      def #{provider}
-        @user = User.find_for_oauth(env["omniauth.auth"], current_user)
-
-        if @user.persisted?
-          sign_in_and_redirect @user, event: :authentication
-          set_flash_message(:notice, :success, kind: "#{provider}".capitalize) if is_navigational_format?
-        else
-          session["devise.#{provider}_data"] = env["omniauth.auth"]
-          redirect_to new_user_registration_url
-        end
-      end
-    }
+  def twitter
+    sign_in_with :twitter
   end
 
-  [:twitter, :facebook, :google_oauth2].each do |provider|
-    provides_callback_for provider
+  def facebook
+    sign_in_with :facebook
+  end
+
+  def google_oauth2
+    sign_in_with :google_oauth2
   end
 
   def after_sign_in_path_for(resource)
@@ -28,4 +20,22 @@ class Users::OmniauthCallbacksController < Devise::OmniauthCallbacksController
     end
   end
 
+  private
+
+    def sign_in_with(provider)
+      auth = env["omniauth.auth"]
+
+      identity = Identity.first_or_create_from_oauth(auth)
+      @user = current_user || identity.user || User.first_or_initialize_for_oauth(auth)
+
+      if @user.save
+        identity.update(user: @user)
+        sign_in_and_redirect @user, event: :authentication
+        set_flash_message(:notice, :success, kind: "#{provider}".capitalize) if is_navigational_format?
+      else
+        session["devise.#{provider}_data"] = env["omniauth.auth"]
+        redirect_to new_user_registration_url
+      end
+    end
+
 end