guilded_rose_kata

gilded_rose.rb

class ItemUpdater
  class AgedBrie < ItemUpdater
    def value_change
      -super
    end
  end

  class BackstagePass < ItemUpdater
    def value_change
      case sell_in
      when -Float::INFINITY..0
        -quality
      when 1..5
        3
      when 5..10
        2
      else
        1
      end
    end
  end

  class Sulfuras < ItemUpdater
    def call
      # no-op
    end
  end

  class Conjured < ItemUpdater
    def value_change
      super * 2
    end
  end

  attr_reader :sell_in, :quality

  MINIMUM_QUALITY = 0
  MAXIMUM_QUALITY = 50

  UPDATER_CLASSES = {
    'Aged Brie' => AgedBrie,
    'Backstage passes to a TAFKAL80ETC concert' => BackstagePass,
    'Sulfuras, Hand of Ragnaros' => Sulfuras,
    'Conjured Mana Cake' => Conjured,
  }

  UPDATER_CLASSES.default = self

  def self.from_name(name)
    UPDATER_CLASSES[name]
  end

  def initialize(sell_in, quality)
    @sell_in = sell_in
    @quality = quality
  end

  def call
    @quality = within_boundary(quality + value_change)
    @sell_in -= 1
  end

  def value_change
    if sell_in.zero? || sell_in.negative?
      -2
    else
      -1
    end
  end

  private

  def within_boundary(value)
    value_or_maximum = [MAXIMUM_QUALITY, value].min
    [MINIMUM_QUALITY, value_or_maximum].max
  end
end

class GildedRose
  def initialize(items)
    @items = items
  end

  def update_quality
    @items.each do |item|
      updater = ItemUpdater.from_name(item.name).new(item.sell_in, item.quality)
      updater.call
      item.sell_in = updater.sell_in
      item.quality = updater.quality
    end
  end
end

class Item
  attr_accessor :name, :sell_in, :quality

  def initialize(name, sell_in, quality)
    @name = name
    @sell_in = sell_in
    @quality = quality
  end

  def to_s
    "#{@name}, #{@sell_in}, #{@quality}"
  end
end

gilded_rose_kata_spec.rb

require File.join(File.dirname(__FILE__), 'gilded_rose')

describe GildedRose do
  describe '#update_quality' do
    subject { GildedRose.new(items) }
    let(:items) { [item] }
    let(:item) { Item.new(object_name, 20, 20) }

    context 'generic objects' do
      let(:object_name) { 'foo' }

      it 'does not change the name' do
        expect { subject.update_quality }.not_to change { item.name }
      end

      it 'decrease the sell in date by one' do
        expect { subject.update_quality }.to change { item.sell_in }.by(-1)
      end

      it 'decrease the quality by one' do
        expect { subject.update_quality }.to change { item.quality }.by(-1)
      end

      it 'does not decrease the quality bellow zero' do
        item.quality = 0
        expect { subject.update_quality }.not_to change { item.quality }
      end

      it 'decrease the quality by two once the sell in date reach zero' do
        item.sell_in = 0
        expect { subject.update_quality }.to change { item.quality }.by(-2)
      end
    end

    context 'Aged Brie' do
      let(:object_name) { 'Aged Brie' }

      it 'does not increase beyond 50' do
        item.quality = 50
        expect { subject.update_quality }.not_to change { item.quality }
      end

      it 'increase the quality by one' do
        expect { subject.update_quality }.to change { item.quality }.by(+1)
      end

      it 'increase the quality by two once the sell in date reach zero' do
        item.sell_in = 0
        expect { subject.update_quality }.to change { item.quality }.by(+2)
      end
    end

    context 'Sulfras' do
      let(:object_name) { 'Sulfuras, Hand of Ragnaros' }

      it 'does not change the sell in' do
        expect { subject.update_quality }.not_to change { item.sell_in }
      end

      it 'does not change the quality' do
        expect { subject.update_quality }.not_to change { item.quality }
      end

      it 'does not change the quality if the sell in is zero' do
        item.sell_in = 0
        expect { subject.update_quality }.not_to change { item.quality }
      end
    end

    context 'Backstage passes' do
      let(:object_name) { 'Backstage passes to a TAFKAL80ETC concert' }

      it 'increase quality by one when the sell in is more than 10 days' do
        item.sell_in = 11
        expect { subject.update_quality }.to change { item.quality }.by(+1)
      end

      it 'increase quality by two when the sell in is at 10 days' do
        item.sell_in = 10
        expect { subject.update_quality }.to change { item.quality }.by(+2)
      end

      it 'increase quality by three when the sell in is at 5 days' do
        item.sell_in = 5
        expect { subject.update_quality }.to change { item.quality }.by(+3)
      end

      it 'drop quality to zero when the sell in is zero' do
        item.sell_in = 0
        subject.update_quality
        expect(item.quality).to be_zero
      end
    end

    context 'Conjured' do
      let(:object_name) { 'Conjured Mana Cake' }

      it 'decrease the quality by two' do
        expect { subject.update_quality }.to change { item.quality }.by(-2)
      end

      it 'decrease the quality by four once the sell in date reach zero' do
        item.sell_in = 0
        expect { subject.update_quality }.to change { item.quality }.by(-4)
      end
    end
  end
end