class Calculator::FreeShipping < ::Calculator

  def self.description
    I18n.t("free_shipping")
  end

  def self.register
    super                                
    Promotion.register_calculator(self)
  end

  def compute(object)
    if object.is_a?(Array)
      return if object.empty?
      order = object.first.order
    else
      order = object
    end

    order.ship_total
  end
  
end