Added sell-in modification rules

swift/Sources/GildedRose/GildedRose.swift

@@ -1,35 +1,14 @@
 public class GildedRose {
-    var items:[Item]
+    private(set) var items: [Item]
     
-    public init(items:[Item]) {
+    public init(items: [Item]) {
         self.items = items
     }
     
     public func updateQuality() {
-        for i in 0..<items.count {
-            items[i] = QualityModificationRule.process(item: items[i])
-            
-            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
-//                    }
-//                }
-//            }
+        items = items.map { item in
+            let qualityUpdatedItem = QualityModificationRule.process(item: item)
+            return SellInModificationRule.process(item: qualityUpdatedItem)
         }
     }
 }

swift/Sources/GildedRose/Rules/SellInModificationRules.swift

@@ -0,0 +1,36 @@
+//
+//  SellInModificationRule.swift
+//  
+//
+//  Created by Lucas van Dongen on 23/11/2020.
+//
+
+import Foundation
+
+enum SellInModificationRule: Rule {
+    typealias RuleType = Self
+
+    case regular, legendary
+
+    static func rule(for item: Item) -> RuleType {
+        switch item.name {
+        case "Sulfuras, Hand of Ragnaros":
+            return .legendary
+        default:
+            return .regular
+        }
+    }
+
+    func apply(to item: Item) -> Item {
+        switch self {
+        case .regular:
+            return applyRegularRule(to: item)
+        case .legendary:
+            return item // Unmodified
+        }
+    }
+
+    func applyRegularRule(to item: Item) -> Item {
+        return Item(name: item.name, sellIn: item.sellIn - 1, quality: item.quality)
+    }
+}

swift/Tests/GildedRoseTests/TestSellInModificationRule.swift

@@ -0,0 +1,36 @@
+//
+//  TestQualityModificationRules.swift
+//  GildedRose
+//
+//  Created by Lucas van Dongen on 23/11/2020.
+//
+
+@testable import GildedRose
+import XCTest
+
+class TestQualityModificationRules: XCTestCase {
+    private let regularItem = Item(name: "Regular Item", sellIn: 1, quality: 5)
+    private let sulfuras = Item(name: "Sulfuras, Hand of Ragnaros", sellIn: 0, quality: 50)
+
+    //- All items have a SellIn value which denotes the number of days we have to sell the item
+    func testRuleSelection() {
+        XCTAssertEqual(SellInModificationRule.rule(for: regularItem), .regular)
+        XCTAssertEqual(SellInModificationRule.rule(for: sulfuras), .legendary)
+    }
+
+    func testApplyLegendary() {
+        let initialSellIn = sulfuras.sellIn
+        let system = GildedRose(items: [sulfuras])
+        system.updateQuality()
+
+        XCTAssertEqual(system.items.first!.sellIn, initialSellIn)
+    }
+
+    func testApplyRegular() {
+        let initialSellIn = regularItem.sellIn
+        let system = GildedRose(items: [regularItem])
+        system.updateQuality()
+
+        XCTAssertLessThan(system.items.first!.sellIn, initialSellIn)
+    }
+}