Added item stacking

prefabs/UI/Inventory/Slot.tscn

@@ -41,4 +41,22 @@ label_settings = SubResource("LabelSettings_7emux")
 horizontal_alignment = 1
 vertical_alignment = 1
 
+[node name="AmountLabel" type="Label" parent="."]
+layout_mode = 1
+anchors_preset = -1
+anchor_left = 1.0
+anchor_top = 1.0
+anchor_right = 1.0
+anchor_bottom = 1.0
+offset_left = -409.0
+offset_top = -329.0
+offset_right = -10.0
+offset_bottom = -10.0
+grow_horizontal = 0
+grow_vertical = 0
+theme_override_colors/font_color = Color(0, 0, 0, 1)
+text = "999"
+horizontal_alignment = 2
+vertical_alignment = 2
+
 [connection signal="gui_input" from="." to="." method="_on_gui_input"]

scripts/CSharp/Common/Inventory/InventoryInstance.cs

@@ -12,6 +12,7 @@ public partial class InventoryInstance : Node
 
     [Signal]
     public delegate void SlotAmountChangedEventHandler();
+
     [Signal]
     public delegate void InventoryContentsChangedEventHandler();
 
@@ -32,30 +33,62 @@ public partial class InventoryInstance : Node
                     _slots.Add(new InventorySlot());
                 }
             }
+
             EmitSignal(SignalName.SlotAmountChanged);
         }
     }
 
-    public InventoryActionResult AddItem(ItemInstance newItem, int inventorySlot = -1)
+    public InventoryActionResult AddItem(ItemInstance newItem)
+    {
+        var result = AddItemAndStackRecursive(newItem, 0);
+        EmitSignal(SignalName.InventoryContentsChanged);
+        return result;
+    }
+
+    private InventoryActionResult AddItemAndStackRecursive(ItemInstance newItem, int slotSearch)
+    {
+        if (newItem.blueprint == null || newItem.amount == 0)
+            return InventoryActionResult.SourceDoesNotExists;
+
+        var slotIndex = -1;
+        // find stackable slot
+        for (var i = slotSearch; i < _slots.Count; i++)
         {
-        if (inventorySlot < 0)
+            if (_slots[i].itemInstance?.blueprint == newItem.blueprint)
             {
-            inventorySlot = _slots.FindIndex(slot => slot.IsEmpty());
+                slotIndex = i;
+                break;
+            }
         }
 
-        if (inventorySlot < 0 || !_slots[inventorySlot].IsEmpty())
+        if (slotIndex < 0)
         {
-            return InventoryActionResult.DestinationFull;
+            // find empty slot
+            for (var i = slotSearch; i < _slots.Count; i++)
+            {
+                if (_slots[i].IsEmpty())
+                {
+                    slotIndex = i;
+                    break;
+                }
+            }
         }
 
-        if (inventorySlot >= _slots.Count)
+        if (slotIndex < 0)
         {
-            return InventoryActionResult.DestinationDoesNotExists;
+            return InventoryActionResult.DestinationFull;
         }
 
-        _slots[inventorySlot].itemInstance = newItem;
-        EmitSignal(SignalName.InventoryContentsChanged);
-        return InventoryActionResult.Success;
+        var itemInstance = _slots[slotIndex].itemInstance ?? new ItemInstance { blueprint = newItem.blueprint, amount = 0 };
+        var maxStack = itemInstance!.blueprint.maxStack;
+        var freeOnStack = maxStack - itemInstance.amount;
+        var moveAmount = Math.Min(freeOnStack, newItem.amount);
+        itemInstance.amount += moveAmount;
+        newItem.amount -= moveAmount;
+        _slots[slotIndex].itemInstance = itemInstance;
+        return newItem.amount <= 0
+            ? InventoryActionResult.Success
+            : AddItemAndStackRecursive(newItem, slotIndex + 1);
     }
 
     public InventoryActionResult RemoveItem(int inventorySlot, out ItemInstance? itemInstance)
@@ -82,4 +115,17 @@ public partial class InventoryInstance : Node
     {
         return RemoveItem(inventorySlot, out _);
     }
+
+    public InventoryActionResult AddItemToSlot(ItemInstance itemInstance, int destinationSlot)
+    {
+        if (destinationSlot < 0 || destinationSlot >= _slots.Count)
+            return InventoryActionResult.DestinationDoesNotExists;
+        
+        if (!_slots[destinationSlot].IsEmpty())
+            return InventoryActionResult.DestinationFull;
+        
+        _slots[destinationSlot].itemInstance = itemInstance;
+        EmitSignal(SignalName.InventoryContentsChanged);
+        return InventoryActionResult.Success;
+    }
 }

scripts/CSharp/Common/Inventory/InventoryManager.cs

@@ -23,11 +23,13 @@ public partial class InventoryManager : Node
     public InventoryActionResult CreateItem(
         ItemResource itemBlueprint,
         InventoryInstance inventory,
+        int amount = 1,
         int inventorySlot = -1)
     {
-        var newItem = new ItemInstance { blueprint = itemBlueprint };
-        var addResult = inventory.AddItem(newItem, inventorySlot);
-        return addResult;
+        var newItem = new ItemInstance { blueprint = itemBlueprint, amount = amount };
+        return inventorySlot < 0
+            ? inventory.AddItem(newItem)
+            : inventory.AddItemToSlot(newItem, inventorySlot);
     }
 
     public InventoryActionResult MoveItem(
@@ -39,10 +41,11 @@ public partial class InventoryManager : Node
         var remResult = sourceInventory.RemoveItem(sourceSlot, out var item);
         if (remResult != InventoryActionResult.Success) return remResult;
 
-        var addResult = destinationInventory.AddItem(item!, destinationSlot);
+        var addResult = destinationInventory.AddItemToSlot(item!, destinationSlot);
         if (addResult == InventoryActionResult.Success) return InventoryActionResult.Success;
 
-        sourceInventory.AddItem(item!, sourceSlot); // can not fail ... in theory
+        // if adding in the destination failed, re-add the item into the source
+        sourceInventory.AddItemToSlot(item!, sourceSlot); // can not fail ... in theory
         return addResult;
     }
 
@@ -60,6 +63,7 @@ public partial class InventoryManager : Node
     {
         return inventory.RemoveItem(inventorySlot);
     }
+
     public InventoryActionResult CollectItem(ItemInstance itemInstance)
     {
         return playerInventory.AddItem(itemInstance);

scripts/CSharp/Common/Inventory/InventoryUi.cs

@@ -43,6 +43,12 @@ public partial class InventoryUi : Control
             uiSlot!.nameLabel.Text = inventorySlot.itemInstance?.blueprint.name ?? "";
             uiSlot!.nameLabel.LabelSettings = uiSlot!.nameLabel.LabelSettings.Duplicate() as LabelSettings;
             uiSlot!.nameLabel.LabelSettings!.FontColor = inventorySlot.itemInstance?.blueprint.color ?? Colors.White;
+
+            var amountText = inventorySlot.itemInstance != null &&
+                             inventorySlot.itemInstance.amount != 1
+                ? inventorySlot.itemInstance.amount.ToString()
+                : "";
+            uiSlot!.amountLabel.Text = amountText;
         }
     }
 
@@ -99,6 +105,7 @@ public partial class InventoryUi : Control
         {
             InputInventoryOpenClose();
         }
+
         if (Input.IsActionJustPressed("ui_inventory_disadvance"))
         {
             _selectedSlot++;
@@ -106,6 +113,7 @@ public partial class InventoryUi : Control
                 _selectedSlot = 0;
             SetSlotSelectPosition();
         }
+
         if (Input.IsActionJustPressed("ui_inventory_advance"))
         {
             _selectedSlot--;

scripts/CSharp/Common/Inventory/ItemInstance.cs

@@ -4,4 +4,13 @@ public class ItemInstance
 {
     public ItemResource blueprint;
     public int amount = 1;
+
+    public ItemInstance Clone()
+    {
+        return new ItemInstance
+        {
+            blueprint = blueprint,
+            amount = amount
+        };
+    }
 }

scripts/CSharp/Common/Inventory/ItemOnGround.cs

@@ -25,7 +25,7 @@ public partial class ItemOnGround : Node3D
     {
         GD.Print("Trying to pick up item");
 
-        var result = InventoryManager.Instance.CollectItem(itemInstance);
+        var result = InventoryManager.Instance.CollectItem(itemInstance.Clone());
         if (result == InventoryActionResult.Success)
         {
             if (!_infiniteSupply)

scripts/CSharp/Common/Inventory/SlotUi.cs

@@ -7,12 +7,14 @@ public partial class SlotUi : Control
 {
     public Label nameLabel;
     public int index;
+    public Label amountLabel;
 
     [Signal] public delegate void ClickedEventHandler(int index);
 
     public override void _EnterTree()
     {
         nameLabel = GetNode<Label>("NameLabel");
+        amountLabel = GetNode<Label>("AmountLabel");
     }
 
     public void _on_gui_input(InputEvent ev)