order_calculator.rb

class OrderCalulator
  attr_reader :order
  attr_reader :total, :fee
  
  def initialize(order)
    @order = order
  end
  
  def calculate
    @total = calculate_total
    @fee   = calculate_fee
  end
  
  private
  
  def calculate_total
    order.items.sum(&:price)
  end
  
  def calculate_fee
    total * 0.01
  end
end