Migrating a BOGO that ran across the whole cart

危险配对 D17。这个文件和它的搭档看起来几乎一样，行为却不同，在判断您手上是哪一个之前，请把两份都读一遍。

class InterleavedPartitioner
  def initialize(paid_item_count, discounted_item_count)
    @paid_item_count = paid_item_count
    @discounted_item_count = discounted_item_count
  end

  def partition(cart, applicable_line_items)
    sorted_items = applicable_line_items.sort_by { |line_item| line_item.variant.price }.reverse
    discounted_items = []
    paid_items_seen = 0
    discounted_items_seen = 0

    sorted_items.each do |line_item|
      line_item.quantity.times do
        if paid_items_seen < @paid_item_count
          paid_items_seen += 1
        else
          discounted_items_seen += 1
          discounted_items.push(line_item.split(take: 1))
          if discounted_items_seen == @discounted_item_count
            paid_items_seen = 0
            discounted_items_seen = 0
          end
        end
      end
    end

    discounted_items
  end
end

CAMPAIGNS = [
  BogoCampaign.new(
    ProductTagSelector.new("bogo"),
    PercentageDiscount.new(100, "Buy 2 get 1 free"),
    InterleavedPartitioner.new(2, 1)
  ),
]

CAMPAIGNS.each do |campaign|
  campaign.run(Input.cart)
end

Output.cart = Input.cart

识别为 Buy X, get Y，重建为 bxgy 类型的优惠。下面是优惠实际保存时使用的配置键，您可以逐项核对自己的重建结果。

基于我们的公开演示店铺 Meridian Goods 搭建，因此这里的每个价格都可以复现，而不必凭信任接受。下方的折扣金额，是结账时运行的同一个引擎针对这个购物车算出的结果。