Abstract logic for two factor success and fail into separate methods. Further abstract the path for after success into a third method.

app/controllers/devise/two_factor_authentication_controller.rb

@@ -9,43 +9,60 @@ class Devise::TwoFactorAuthenticationController < DeviseController
     render :show and return if params[:code].nil?
 
     if resource.authenticate_otp(params[:code])
-      expires_seconds = resource.class.remember_otp_session_for_seconds
-      if expires_seconds && expires_seconds > 0
-        cookies.signed[TwoFactorAuthentication::REMEMBER_TFA_COOKIE_NAME] = {
-          value: true,
-          expires: expires_seconds.from_now
-        }
-      end
-      warden.session(resource_name)[TwoFactorAuthentication::NEED_AUTHENTICATION] = false
-      sign_in resource_name, resource, :bypass => true
-      set_flash_message :notice, :success
-      redirect_to stored_location_for(resource_name) || :root
-      resource.update_attribute(:second_factor_attempts_count, 0)
+      after_two_factor_success_for(resource)
     else
-      resource.second_factor_attempts_count += 1
-      resource.save
-      flash.now[:error] = find_message(:attempt_failed)
-      if resource.max_login_attempts?
-        sign_out(resource)
-        render :max_login_attempts_reached
-      else
-        render :show
-      end
+      after_two_factor_fail_for(resource)
     end
   end
 
   private
 
-    def authenticate_scope!
-      self.resource = send("current_#{resource_name}")
+  def after_two_factor_success_for(resource)
+    expires_seconds = resource.class.remember_otp_session_for_seconds
+
+    if expires_seconds && expires_seconds > 0
+      cookies.signed[TwoFactorAuthentication::REMEMBER_TFA_COOKIE_NAME] = {
+          value: true,
+          expires: expires_seconds.from_now
+      }
     end
 
-    def prepare_and_validate
-      redirect_to :root and return if resource.nil?
-      @limit = resource.max_login_attempts
-      if resource.max_login_attempts?
-        sign_out(resource)
-        render :max_login_attempts_reached and return
-      end
+    warden.session(resource_name)[TwoFactorAuthentication::NEED_AUTHENTICATION] = false
+    sign_in resource_name, resource, :bypass => true
+    set_flash_message :notice, :success
+    resource.update_attribute(:second_factor_attempts_count, 0)
+
+    redirect_to after_two_factor_success_path_for(resource)
+  end
+
+  def after_two_factor_success_path_for(resource)
+    stored_location_for(resource_name) || :root
+  end
+
+  def after_two_factor_fail_for(resource)
+    resource.second_factor_attempts_count += 1
+    resource.save
+    flash.now[:error] = find_message(:attempt_failed)
+
+    if resource.max_login_attempts?
+      sign_out(resource)
+      render :max_login_attempts_reached
+
+    else
+      render :show
     end
+  end
+
+  def authenticate_scope!
+    self.resource = send("current_#{resource_name}")
+  end
+
+  def prepare_and_validate
+    redirect_to :root and return if resource.nil?
+    @limit = resource.max_login_attempts
+    if resource.max_login_attempts?
+      sign_out(resource)
+      render :max_login_attempts_reached and return
+    end
+  end
 end