Add stackable items

Zennysoft.Game.Ma/src/items/Inventory.cs

@@ -4,6 +4,7 @@ using Chickensoft.Serialization;
 using Godot;
 using System.Collections.Generic;
 using System.Linq;
+using Zennysoft.Game.Abstractions;
 using Zennysoft.Ma.Adapter;
 
 namespace Zennysoft.Game.Ma;
@@ -52,6 +53,16 @@ public partial class Inventory : Node, IInventory
     var consumables = listToSort.Where(x => x is ConsumableItem).OrderBy(x => x as ConsumableItem, new ConsumableComparer());
     var throwables = listToSort.Where(x => x is ThrowableItem).OrderBy(x => x as ThrowableItem, new ThrowableComparer());
     Items = [.. equippedItems, .. weapons, .. armor, .. accessories, .. consumables, .. throwables];
+
+    var stackableItems = Items.OfType<IStackable>();
+    var itemsToStack = stackableItems.GroupBy(x => ((InventoryItem)x).ItemName).Where(x => x.Count() > 1);
+    foreach (var itemStack in itemsToStack)
+    {
+      var firstItem = itemStack.First();
+      firstItem.SetCount(itemStack.Count());
+      var itemsToRemove = itemStack.Except([firstItem]).Cast<InventoryItem>();
+      Items = [.. Items.Except(itemsToRemove)];
+    }
   }
 
   public class WeaponComparer : IComparer<Weapon>