Extract logic to create Updater into DailyUpdaterFactory and some minor refactoring in DailyUpdater.cs

csharpcore/GildedRose/DailyUpdater.cs

@@ -4,13 +4,17 @@ namespace GildedRoseKata;
 
 public abstract class DailyUpdater
 {
-    protected const int MinQuality = 0;
+    private const int MinQuality = 0;
-    protected const int MaxQuality = 50;
+    private const int MaxQuality = 50;
 
     public void DailyUpdate(Item item)
     {
         UpdateSellIn(item);
         UpdateQuality(item);
+        if (IsExpired(item))
+        {
+            UpdateQuality(item);
+        }
     }
 
     public abstract void UpdateQuality(Item item);
@@ -18,28 +22,22 @@ public abstract class DailyUpdater
 
     protected static bool IsExpired(Item item) => item.SellIn < 0;
 
-    protected static void IncreaseQuality(Item item, int byValue)
+    protected static void IncreaseQuality(Item item, int byValue = 1)
     {
         item.Quality = int.Min(item.Quality + byValue, MaxQuality);
     }
 
-    protected static void DecreaseQuality(Item item, int byValue)
+    protected static void DecreaseQuality(Item item, int byValue = 1)
     {
         item.Quality = int.Max(item.Quality - byValue, MinQuality);
     }
-    
-    
 }
 
 public class DailyUpdaterForRegularItems : DailyUpdater
 {
     public override void UpdateQuality(Item item)
     {
-        DecreaseQuality(item, 1);
+        DecreaseQuality(item);
-        if (IsExpired(item))
-        {
-            DecreaseQuality(item, 1);
-        }
     }
 }
 
@@ -47,11 +45,7 @@ public class DailyUpdaterForBetterWithAgeItems : DailyUpdater
 {
     public override void UpdateQuality(Item item)
     {
-        IncreaseQuality(item, 1);
+        IncreaseQuality(item);
-        if (IsExpired(item))
-        {
-            IncreaseQuality(item, 1);
-        }
     }
 }
 
@@ -62,7 +56,7 @@ public class DailyUpdaterForBackstagePassesItems : DailyUpdater
     {
         if (item.SellIn > 9)
         {
-            IncreaseQuality(item, 1);
+            IncreaseQuality(item);
         }
         else if (item.SellIn > 4)
         {

csharpcore/GildedRose/DailyUpdaterFactory.cs

@@ -0,0 +1,31 @@
+namespace GildedRoseKata;
+
+public static class DailyUpdaterFactory
+{
+    public static DailyUpdater GetDailyUpdater(Item item)
+    {
+        if (IsLegendaryItem(item))
+        {
+            return new DailyUpdaterForLegendaryItems();
+        } 
+        
+        if (IsBetterWithAgeItem(item))
+        {
+            return new DailyUpdaterForBetterWithAgeItems();
+        }
+
+        if (IsBackstagePassesItem(item))
+        {
+            return new DailyUpdaterForBackstagePassesItems();
+        }
+
+        return new DailyUpdaterForRegularItems();
+    }
+    
+    private static bool IsLegendaryItem(Item item) => item.Name.ToLower().Contains("sulfuras");
+
+    private static bool IsBackstagePassesItem(Item item) => item.Name.ToLower().Contains("backstage passes");
+
+    private static bool IsBetterWithAgeItem(Item item) => item.Name.ToLower().Equals("aged brie");
+    
+}

csharpcore/GildedRose/GildedRose.cs

@@ -5,8 +5,6 @@ namespace GildedRoseKata;
 public class GildedRose
 {
     private readonly IList<Item> _items;
-    const int MinQuality = 0;
-    const int MaxQuality = 50;
 
     public GildedRose(IList<Item> items)
     {
@@ -17,34 +15,9 @@ public class GildedRose
     {
         foreach (var item in _items)
         {
-            DailyUpdater dailyUpdater = getDailyUpdater(item);
+            DailyUpdater dailyUpdater = DailyUpdaterFactory.GetDailyUpdater(item);
             dailyUpdater.DailyUpdate(item);
         }
     }
-
-    private static bool IsLegendaryItem(Item item) => item.Name.ToLower().Contains("sulfuras");
-
-    private static bool IsBackstagePassesItem(Item item) => item.Name.ToLower().Contains("backstage passes");
-
-    private static bool IsBetterWithAgeItem(Item item) => item.Name.ToLower().Equals("aged brie");
     
-    private DailyUpdater getDailyUpdater(Item item)
-    {
-        if (IsLegendaryItem(item))
-        {
-            return new DailyUpdaterForLegendaryItems();
-        }
-
-        if (IsBetterWithAgeItem(item))
-        {
-            return new DailyUpdaterForBetterWithAgeItems();
-        }
-
-        if (IsBackstagePassesItem(item))
-        {
-            return new DailyUpdaterForBackstagePassesItems();
-        }
-
-        return new DailyUpdaterForRegularItems();
-    }
 }

csharpcore/GildedRose/RefactoringDiary.md

@@ -16,7 +16,9 @@ I decorated these tests with `[Ignore]` until I get to a stage in the refactorin
 5. Used the `Template` design pattern to create DailyUpdater abstract class and derived classes to handle the DailyUpdate's steps for the different types of items.<br>
 The different derived classes will be moved to their own files in the next PR. Left them together for now to show the steps.
 6. Created a `Simple Factory` method to return the appropriate DailyUpdater object for the item type.<br>
-For this PR, I left this method in the GildedRose.cp to show the steps. But in the next PR I'll move it into its own class.
+7. Moved DailyUpdaterFactory to its own class.
+8. Moved the logic of "Once the sell by date has passed, Quality degrades twice as fast" into the DailyUpdater Template class since it's relevant to all types of items.
+9. Moved Decrease/IncreaseItem byValue to be 1 by default.
 
 
 This is the state of the code now