GildedRose Refactoring Kata in Go

gilded-rose-original.go

package main

func UpdateQualityOld(items ...*Item) {
	for i := 0; i < len(items); i++ {

		if items[i].name != "Aged Brie" && items[i].name != "Backstage passes to a TAFKAL80ETC concert" {
			if items[i].quality > 0 {
				if items[i].name != "Sulfuras, Hand of Ragnaros" {
					items[i].quality = items[i].quality - 1
				}
			}
		} else {
			if items[i].quality < 50 {
				items[i].quality = items[i].quality + 1
				if items[i].name == "Backstage passes to a TAFKAL80ETC concert" {
					if items[i].sellIn < 11 {
						if items[i].quality < 50 {
							items[i].quality = items[i].quality + 1
						}
					}
					if items[i].sellIn < 6 {
						if items[i].quality < 50 {
							items[i].quality = items[i].quality + 1
						}
					}
				}
			}
		}

		if items[i].name != "Sulfuras, Hand of Ragnaros" {
			items[i].sellIn = items[i].sellIn - 1
		}

		if items[i].sellIn < 0 {
			if items[i].name != "Aged Brie" {
				if items[i].name != "Backstage passes to a TAFKAL80ETC concert" {
					if items[i].quality > 0 {
						if items[i].name != "Sulfuras, Hand of Ragnaros" {
							items[i].quality = items[i].quality - 1
						}
					}
				} else {
					items[i].quality = items[i].quality - items[i].quality
				}
			} else {
				if items[i].quality < 50 {
					items[i].quality = items[i].quality + 1
				}
			}
		}
	}
}

gilded-rose.go

package main

type Item struct {
	name            string
	sellIn, quality int
}

type Brie struct {
	*Item
}

func (i *Brie) Update() *Item {
	if i.quality < 50 {
		i.quality++
	}

	i.sellIn = i.sellIn - 1
	if i.sellIn < 0 && i.quality < 50 {
		i.quality++
	}

	return i.Item
}

type Backstage struct {
	*Item
}

func (i *Backstage) Update() *Item {
	if i.quality < 50 {
		i.quality++
	}

	if i.sellIn < 11 && i.quality < 50 {
		i.quality++
	}

	if i.sellIn < 6 && i.quality < 50 {
		i.quality++
	}

	i.sellIn = i.sellIn - 1
	if i.sellIn < 0 {
		i.quality = i.quality - i.quality
	}
	return i.Item
}

type Sulfuras struct {
	*Item
}

func (i *Sulfuras) Update() *Item {
	return i.Item
}

type Other struct {
	*Item
}

func (i *Other) Update() *Item {
	if i.quality > 0 {
		i.quality = i.quality - 1
	}

	i.sellIn = i.sellIn - 1

	if i.sellIn < 0 && i.quality > 0 {
		i.quality = i.quality - 1
	}

	return i.Item
}

type Conjured struct {
	*Item
}

func (i *Conjured) Update() *Item {
	if i.quality > 0 {
		i.quality = i.quality - 2
	}

	i.sellIn = i.sellIn - 1

	if i.sellIn < 0 && i.quality > 0 {
		i.quality = i.quality - 2
	}

	return i.Item
}

type updateable interface {
	Update() *Item
}

func UpdateQuality(items ...*Item) {
	for i := 0; i < len(items); i++ {
		var ui updateable
		switch items[i].name {
		case "Sulfuras, Hand of Ragnaros":
			ui = &Sulfuras{Item: items[i]}
		case "Aged Brie":
			ui = &Brie{Item: items[i]}
		case "Backstage passes to a TAFKAL80ETC concert":
			ui = &Backstage{Item: items[i]}
		case "Conjured Mana Cake":
			ui = &Conjured{Item: items[i]}
		default:
			ui = &Other{Item: items[i]}
		}

		items[i] = ui.Update()
	}
}

gilded-rose_test.go

package main

// This test was copied from https://github.com/robphoenix/gilded-rose/blob/10f9154a5b/gilded-rose/item_test.go 

import "testing"

var tests = []struct {
	name            string
	description     string
	days            int
	quality         int
	expectedDays    int
	expectedQuality int
}{
	{"normal", "before sell date", 5, 10, 4, 9},
	{"normal", "on sell date", 0, 10, -1, 8},
	{"normal", "after sell date", -10, 10, -11, 8},
	{"normal", "of zero quality", 5, 0, 4, 0},
	{"Aged Brie", "before sell date with max quality", 5, 50, 4, 50},
	{"Aged Brie", "on sell date", 0, 10, -1, 12},
	{"Aged Brie", "on sell date near max quality", 0, 49, -1, 50},
	{"Aged Brie", "on sell date with max quality", 0, 50, -1, 50},
	{"Aged Brie", "after sell date", -10, 10, -11, 12},
	{"Aged Brie", "after sell date with max quality", -10, 50, -11, 50},
	{"Sulfuras, Hand of Ragnaros", "before sell date", 5, 80, 5, 80},
	{"Sulfuras, Hand of Ragnaros", "on sell date", 0, 80, 0, 80},
	{"Sulfuras, Hand of Ragnaros", "after sell date", -10, 80, -10, 80},
	{"Backstage passes to a TAFKAL80ETC concert", "long before sell date", 11, 10, 10, 11},
	{"Backstage passes to a TAFKAL80ETC concert", "long before sell date at max quality", 11, 50, 10, 50},
	{"Backstage passes to a TAFKAL80ETC concert", "medium close to sell date (upper bound)", 10, 10, 9, 12},
	{"Backstage passes to a TAFKAL80ETC concert", "medium close to sell date (upper bound) at max quality", 10, 50, 9, 50},
	{"Backstage passes to a TAFKAL80ETC concert", "medium close to sell date (lower bound)", 6, 10, 5, 12},
	{"Backstage passes to a TAFKAL80ETC concert", "medium close to sell date (lower bound) at max quality", 6, 50, 5, 50},
	{"Backstage passes to a TAFKAL80ETC concert", "very close to sell date (upper bound)", 5, 10, 4, 13},
	{"Backstage passes to a TAFKAL80ETC concert", "very close to sell date (upper bound) at max quality", 5, 50, 4, 50},
	{"Backstage passes to a TAFKAL80ETC concert", "very close to sell date (lower bound)", 1, 10, 0, 13},
	{"Backstage passes to a TAFKAL80ETC concert", "very close to sell date (lower bound) at max quality", 1, 50, 0, 50},
	{"Backstage passes to a TAFKAL80ETC concert", "on sell date", 0, 10, -1, 0},
	{"Backstage passes to a TAFKAL80ETC concert", "after sell date", -10, 10, -11, 0},
	{"Conjured Mana Cake", "before sell date", 5, 10, 4, 8},
	{"Conjured Mana Cake", "before sell date at zero quality", 5, 0, 4, 0},
	{"Conjured Mana Cake", "on sell date", 0, 10, -1, 6},
	{"Conjured Mana Cake", "on sell date at zero quality", 0, 0, -1, 0},
	{"Conjured Mana Cake", "after sell date", -10, 10, -11, 6},
	{"Conjured Mana Cake", "after sell date at zero quality", -10, 0, -11, 0},
}

func TestGildedRose(t *testing.T) {
	for _, tt := range tests {
		item := &Item{tt.name, tt.days, tt.quality}
		UpdateQuality(item)
		if item.quality != tt.expectedQuality {
			t.Errorf("\n%s %s\nexpected quality: %d\nactual quality: %d", tt.name, tt.description, tt.expectedQuality, item.quality)
		}
		if item.sellIn != tt.expectedDays {
			t.Errorf("\n%s %s\nexpected days left: %d\nactual days left: %d", tt.name, tt.description, tt.expectedDays, item.sellIn)
		}
	}
}