Gilded Rose

GildedRose.swift

import Foundation

typealias Quality = Int
typealias SellIn = Int
typealias UpdateRule = (Item) -> Item

struct Item {
    
    enum Kind: String {
        case normal
        case conjured
        case sulfuras
        case brie
        case backstage
    }
    
    var name: String
    var kind: Kind
    var sellIn: SellIn
    var quality: Quality
    
    var updateRule: UpdateRule {
        switch kind {
        case .normal:
            return { item in Item(name: self.name, kind: self.kind,
                                  sellIn: self.sellIn-1,
                                  quality: self.quality-1)
            }
        case .conjured:
            return { item in Item(name: self.name, kind: self.kind,
                                  sellIn: self.sellIn-1,
                                  quality: self.quality-2)
            }
        case .sulfuras:
            return { _ in self }
        case .brie:
            return { item in Item(name: self.name, kind: self.kind,
                                  sellIn: self.sellIn-1,
                                  quality: self.quality+1)
            }
        case .backstage:
            return { item in
                
                let newQuality: Quality
                switch self.sellIn {
                case ...0:
                    newQuality = 0
                case ...5:
                    newQuality = self.quality+3
                case ...10:
                    newQuality = self.quality+2
                case _:
                    newQuality = self.quality+1
                }
                
                return Item(name: self.name, kind: self.kind,
                            sellIn: self.sellIn-1,
                            quality: newQuality)
            }
        }
    }
    
    init(name: String, kind: Item.Kind, sellIn: Int, quality: Int) {
        self.name = name
        self.kind = kind
        self.sellIn = max(sellIn,0)
        self.quality = min(max(quality, 0), 50)
    }
    
    mutating func update() {
        self = updated()
    }
    
    func updated() -> Item {
        return updateRule(self)
    }
    
}

extension Item: CustomStringConvertible {
    public var description: String {
        return [name, kind.rawValue, String(sellIn), String(quality)].joined(separator: ", ")
    }
}

var items = [
    Item(name: "+5 Dexterity Vest", kind: .normal, sellIn: 10, quality: 20),
    Item(name: "Aged Brie", kind: .brie, sellIn: 2, quality: 0),
    Item(name: "Elixir of the Mongoose", kind: .normal, sellIn: 5, quality: 7),
    Item(name: "Sulfuras, Hand of Ragnaros", kind: .sulfuras, sellIn: 10, quality: 80),
    Item(name: "Sulfuras, Hand of Ragnaros", kind: .sulfuras, sellIn: -1, quality: 80),
    Item(name: "Backstage passes to a TAFKAL80ETC concert", kind: .backstage, sellIn: 15, quality: 20),
    Item(name: "Backstage passes to a TAFKAL80ETC concert", kind: .backstage, sellIn: 10, quality: 49),
    Item(name: "Backstage passes to a TAFKAL80ETC concert", kind: .backstage, sellIn: 5, quality: 49),
    Item(name: "Conjured Mana Cake", kind: .conjured, sellIn: 3, quality: 6)
]

let days = 100
for day in 0 ..< days {
    print("-------- day \(day) --------")
    for item in items {
        print(item)
    }
    print("")
    for index in items.indices {
        items[index].update()
    }
}