Gilded Rose Kata

gilded_rose.rb

require_relative 'item'

class GildedRose

  def initialize items
    @items = items
  end

  def update_quality
    @items.each{ |item| update_item item }
  end

  private

  def update_item item
    update_strategy = UpdateStrategyFactory.get_strategy_for(item)
    update_strategy.update_item()
  end
end

class DefaultUpdateStrategy
  def initialize item
    @item = item
  end

  def update_item
    update_sell_in
    update_quality
  end

  private

  def update_sell_in
    @item.sell_in -= 1
  end

  def update_quality
    return if @item.quality <= 0
    multiplier = sell_date_passed? ? 2 : 1
    @item.quality -= multiplier
  end

  def sell_date_passed?
    @item.sell_in < 0
  end
end

class AgedBrieUpdateStrategy < DefaultUpdateStrategy
  private
  def update_quality
    return if @item.quality >= 50
    multiplier = sell_date_passed? ? 2 : 1
    @item.quality += multiplier
  end
end

class SulfurasUpdateStrategy < DefaultUpdateStrategy
  private
  def update_sell_in
  end
end

class BackstagePassUpdateStrategy < DefaultUpdateStrategy
  private
  def update_quality
    @item.quality = 0 and return if @item.sell_in < 0
    increment_item_quality if @item.sell_in < 10
    increment_item_quality if @item.sell_in < 5
    increment_item_quality
  end

  def increment_item_quality
    return if @item.quality >= 50
    @item.quality += 1
  end
end

class ConjuredManaCakeUpdateStrategy < DefaultUpdateStrategy
  private
  def update_quality
    @item.quality -= 2 unless @item.quality <= 0
  end
end

class UpdateStrategyFactory
  MAP = {
    "Aged Brie" => AgedBrieUpdateStrategy,
    "Sulfuras, Hand of Ragnaros" => SulfurasUpdateStrategy,
    "Backstage passes to a TAFKAL80ETC concert" => BackstagePassUpdateStrategy,
    "Conjured Mana Cake" => ConjuredManaCakeUpdateStrategy,
  }

  def self.get_strategy_for item
    strategy = MAP[item.name] || DefaultUpdateStrategy
    strategy.new(item)
  end
end