checkout.rb

class Checkout
  attr_reader :basket, :pricing_rules

  def initialize(pricing_rules)
    @basket = []
    @pricing_rules = pricing_rules
  end

  # [
  #   bogof: [ product_code ],
  #   bulk_discount: [ product_code, new_unit_price, min_number ]
  # ]

  def scan(item_code)
    basket << item(item_code)
  end

  def total
    discount = 0
    basket.group_by{|i| i[:code]}.each do |code, grouping|   #=> [[3 rasberries], [2 soe]]
      discount -= discounts(code, grouping)
    end
    basket.inject(discount) { |sum, i| sum += i[:price]; sum }
  end

  def discounts(code, grouping)
    discount = 0
    if pricing_rules[:bogof].include? code
      return (grouping.count / 2) * grouping.first[:price]
    end
    return discount
  end

  def item(item_code)
    {
      'FR1' => { code: 'FR1', name: 'Fruit Tea', price: 311 },
      'SR1' => { code: 'SR1', name: 'Strawberries', price: 500 },
      'CF1' => { code: 'CF1', name: 'Coffee', price: 1123 },
    }[item_code]
  end

end