My take on the Gilded Rose refactoring kata

gilded_rose.rb

class Product
  attr_reader :item

  def initialize(item:)
    @item = item
  end

  def update_quality
    move_sale_date_closer

    if item.sell_in < 0
      decrease_quality(2)
    else
      decrease_quality(1)
    end
  end

  def set_quality(adjusted_quality)
    if adjusted_quality > 50
      item.quality = 50
    elsif adjusted_quality < 0
      item.quality = 0
    else
      item.quality = adjusted_quality
    end
  end

  def increase_quality(adjustment)
    adjusted_quality = item.quality + adjustment

    set_quality(adjusted_quality)
  end

  def decrease_quality(adjustment)
    adjusted_quality = item.quality - adjustment

    set_quality(adjusted_quality)
  end

  def move_sale_date_closer
    item.sell_in -= 1
  end
end

class AgedBrie < Product
  def update_quality
    move_sale_date_closer

    if extra_aged?
      increase_quality(2)
    else
      increase_quality(1)
    end
  end

  private

    def extra_aged?
      item.sell_in < 0
    end
end

class BackstagePass < Product
  def update_quality
    move_sale_date_closer

    return set_quality(0) if concert_passed?

    if concert_five_days_away?
      increase_quality(3)
    elsif concert_ten_days_away?
      increase_quality(2)
    else
      increase_quality(1)
    end
  end

  private

    def concert_passed?
      item.sell_in < 0
    end

    def concert_five_days_away?
      item.sell_in < 5
    end

    def concert_ten_days_away?
      item.sell_in < 10
    end
end

class Sulfuras < Product
  def update_quality
    # Do nothing!
  end
end

class ConjuredItem < Product
  def update_quality
    move_sale_date_closer

    if item.sell_in < 0
      decrease_quality(4)
    else
      decrease_quality(2)
    end
  end
end

def item_lookup(name)
  {
    "Aged Brie" => AgedBrie,
    "Backstage passes to a TAFKAL80ETC concert" => BackstagePass,
    "Sulfuras, Hand of Ragnaros" => Sulfuras,
    "Conjured Mana Cake" => ConjuredItem
  }.fetch(name, Product)
end

def update_quality(items)
  items.each do |item|
    product_class = item_lookup(item.name)

    product = product_class.new(item: item)

    product.update_quality
  end
end

#----------------------------
# DO NOT CHANGE THINGS BELOW
#----------------------------

Item = Struct.new(:name, :sell_in, :quality)