- Code refactoring as per SOLID Principles

swift/Sources/GildedRose/CustomisedItemFactory.swift

@@ -7,16 +7,10 @@
 
 import Foundation
 
-protocol CustomisedItem {
-    var item: Item {get set}
-    func updateItemState()
-}
-
 protocol CustomisedItemFactoryCreator {
     static func getCustomisedItem(item: Item) -> CustomisedItem
 }
 
-
 struct CustomisedItemFactory: CustomisedItemFactoryCreator {
     // Returns the Customised Item based on the Item name
     static func getCustomisedItem(item: Item) -> CustomisedItem {

swift/Sources/GildedRose/GlidedRoseConstants.swift

@@ -17,4 +17,3 @@ struct ValueConstants {
     static let kHightestQualityValue = 50
     static let kLowestQualityValue = 0
 }
-

swift/Sources/GildedRose/ItemQualityUpdater.swift

@@ -11,14 +11,7 @@ protocol ItemQualityUpdater: CustomisedItem {
 }
 
 extension ItemQualityUpdater {
-    var isItemUnderHighestQuality: Bool {
-        return item.quality < ValueConstants.kHightestQualityValue
-    }
-    
-    var isItemMoreThanLowestQuality: Bool {
-        return item.quality > ValueConstants.kLowestQualityValue
-    }
-    
+   
     func reduceItemQuality(by value:Int) {
         item.quality -= value
     }
@@ -33,4 +26,3 @@ extension ItemQualityUpdater {
 }
 
 typealias ItemStateUpdater = ItemSellInUpdater & ItemQualityUpdater
-

swift/Sources/GildedRose/ItemSellInUpdater.swift

@@ -12,9 +12,6 @@ protocol ItemSellInUpdater: CustomisedItem{
 }
 
 extension ItemSellInUpdater {
-    var isSellInDatePassed: Bool{
-        return item.sellIn < 0
-    }
     func reduceSellInDays(by days: Int) {
         item.sellIn -= days
     }

swift/Sources/GildedRose/Items/AgedBrieItem.swift

@@ -9,7 +9,11 @@ import Foundation
 
 struct AgedBrieItem: ItemStateUpdater{
     var item: Item
-        
+    
+    private var isItemUnderHighestQuality: Bool {
+        return item.quality < ValueConstants.kHightestQualityValue
+    }
+    
     public init(item: Item) {
         self.item = item
     }
@@ -22,7 +26,4 @@ struct AgedBrieItem: ItemStateUpdater{
         guard isItemUnderHighestQuality else { return }
         increaseItemQuality(by: 1)
     }
-    
-    
-    
 }

swift/Sources/GildedRose/Items/BackstagePassesItem.swift

@@ -10,6 +10,14 @@ import Foundation
 struct BackstagePassesItem: ItemStateUpdater {
     var item: Item
     
+    private var isItemUnderHighestQuality: Bool {
+        return item.quality < ValueConstants.kHightestQualityValue
+    }
+    
+    private var isSellInDatePassed: Bool{
+        return item.sellIn < 0
+    }
+    
     public init(item: Item) {
         self.item = item
     }

swift/Sources/GildedRose/Items/CustomisedItem.swift

@@ -0,0 +1,13 @@
+//
+//  File.swift
+//  
+//
+//  Created by Manali Mogre on 17/08/2020.
+//
+
+import Foundation
+
+protocol CustomisedItem {
+    var item: Item {get set}
+    func updateItemState()
+}

swift/Sources/GildedRose/Items/StandardItem.swift

@@ -10,6 +10,21 @@ import Foundation
 struct StandardItem: ItemStateUpdater {
     var item: Item
     
+    private var isSellInDatePassed: Bool{
+        return item.sellIn < 0
+    }
+    
+    var decreasingValueOverZeroDaysToSell: Int {
+        return 1
+    }
+    private var decreasingValueForZeroOrLessDaysToSell: Int {
+        return 2 * decreasingValueOverZeroDaysToSell
+    }
+    
+    private  var isItemMoreThanLowestQuality: Bool {
+        return item.quality > ValueConstants.kLowestQualityValue
+    }
+    
     public init(item: Item) {
         self.item = item
     }
@@ -17,9 +32,9 @@ struct StandardItem: ItemStateUpdater {
     func updateItemState() {
         // Reduce the sellIn days for Item by 1
         reduceSellInDays(by: 1)
-
+        
         // Reduce the item quality by 1 , if the sell in date is passed decrement by double the value
-        isSellInDatePassed ? reduceItemQuality(by: decreasingValueForZeroOrLessDaysToSell()) : reduceItemQuality(by: decreasingValueOverZeroDaysToSell())
+        isSellInDatePassed ? reduceItemQuality(by: decreasingValueForZeroOrLessDaysToSell) : reduceItemQuality(by: decreasingValueOverZeroDaysToSell)
         
         guard isItemMoreThanLowestQuality else {
             // Sets the quality to zero if the quality is negative
@@ -27,12 +42,4 @@ struct StandardItem: ItemStateUpdater {
             return
         }
     }
-    
-    func decreasingValueOverZeroDaysToSell() -> Int {
-        return 1
-    }
-    
-    private func decreasingValueForZeroOrLessDaysToSell() -> Int {
-        return 2 * decreasingValueOverZeroDaysToSell()
-    }
 }