mlomnicki/ddd-ecommerce

Money = Struct.new(:amount_in_cents, :currency) do
  DEFAULT_CURRENCY = "EUR".freeze

  def self.from_float(amount, currency = DEFAULT_CURRENCY)
    new((amount * 100).round, currency)
  end

  def self.from_int(amount, currency = DEFAULT_CURRENCY)
    new(amount, currency)
  end

  def self.zero
    from_int(0)
  end

  private_class_method :new

  alias_method :to_i, :amount_in_cents

  def +(other)
    plus(other.amount_in_cents)
  end

  def -(other)
    plus(-other.amount_in_cents)
  end

  def to_s
    sprintf("#{currency}%.2f", amount_in_cents / 100.0)
  end

  private

  def plus(added_amount_in_cents)
    self.class.from_int(amount_in_cents + added_amount_in_cents, currency)
  end
end