-

def assert_equal(expected, actual)
  print expected == actual ? "." : "Expected #{expected.inspect} but got #{actual.inspect}\n"
end

Discount = Struct.new(:amount, :value) do
  def apply(basket, item)
    (basket.count(item)/amount) * value
  end
end

# same as...

class Discount
  def initialize(amount, value)
    @amount = amount
    @value = value
  end

  def apply(basket, item)
    (basket.count(item)/@amount) * @value
  end
end

class Checkout
  PRODUCTS = {
    "A" => {
      price: 50,
      discount: Discount.new(3, -20)
    },
    "B" => {
      price: 30,
      discount: Discount.new(2, -15)
    }
  }

  def initialize
    @basket = []
  end

  def scan(item)
    @basket.push(item)
  end

  def total
    PRODUCTS.keys.map do |item|
      @basket.count(item) * PRODUCTS[item][:price] + PRODUCTS[item][:discount].apply(@basket, item)
    end.reduce(:+)
  end
end

checkout = Checkout.new
assert_equal(0, checkout.total)
checkout.scan("A")
assert_equal(50, checkout.total)
checkout.scan("B")
assert_equal(80, checkout.total)

checkout = Checkout.new
checkout.scan("A")
checkout.scan("A")
checkout.scan("A")
assert_equal(130, checkout.total)

checkout = Checkout.new
checkout.scan("B")
checkout.scan("B")
assert_equal(45, checkout.total)


#puts