Devise::Controllers::UrlHelpers.module_eval do
  [:path, :url].each do |path_or_url|
    [nil, :new_, :accept_].each do |action|
      class_eval <<-URL_HELPERS
        def #{action}invitation_#{path_or_url}(resource, *args)
          resource = case resource
            when Symbol, String
              resource
            when Class
              resource.name.underscore
            else
              resource.class.name.underscore
          end

          send("#{action}\#{resource}_invitation_#{path_or_url}", *args)
        end
      URL_HELPERS
    end
  end
end