From c5e692c0510d49106bf9515dd88479ace6e8b5a7 Mon Sep 17 00:00:00 2001
From: Zeeshaun <zeeshaun@gmail.com>
Date: Fri, 20 Mar 2026 13:18:22 -0500
Subject: [PATCH] Fixing drop/pickup stacking

---
 game/scenes/Levels/location_level.gd          |  3 +-
 .../InventoryApi/Services/InventoryStore.cs   | 41 ++++++++++++++++---
 2 files changed, 36 insertions(+), 8 deletions(-)

diff --git a/game/scenes/Levels/location_level.gd b/game/scenes/Levels/location_level.gd
index a30d1f1..ea56e22 100644
--- a/game/scenes/Levels/location_level.gd
+++ b/game/scenes/Levels/location_level.gd
@@ -678,8 +678,7 @@ func _on_inventory_pickup_pressed() -> void:
 		_inventory_status_label.text = "Current location is missing an id."
 		return
 	var quantity := int(_quantity_spin_box.value)
-	var to_slot := int(_target_slot_spin_box.value)
-	_transfer_item_async(_selected_ground_item_id, "location", location_id, "character", _character_id, to_slot, quantity, "Picked up item.")
+	_transfer_item_async(_selected_ground_item_id, "location", location_id, "character", _character_id, null, quantity, "Picked up item.")
 
 
 func _on_inventory_refresh_pressed() -> void:
diff --git a/microservices/InventoryApi/Services/InventoryStore.cs b/microservices/InventoryApi/Services/InventoryStore.cs
index 5c58232..4bd318d 100644
--- a/microservices/InventoryApi/Services/InventoryStore.cs
+++ b/microservices/InventoryApi/Services/InventoryStore.cs
@@ -328,13 +328,28 @@ public class InventoryStore
         if (definition is null)
             return new InventoryMutationResult { Status = InventoryMutationStatus.Invalid };
 
-        var toSlot = req.ToSlot ?? await FindFirstOpenSlotAsync(toOwner.OwnerType, toOwner.OwnerId);
-        if (toSlot is null)
-            return new InventoryMutationResult { Status = InventoryMutationStatus.Conflict };
+        InventoryItem? target = null;
+        int? toSlot = req.ToSlot;
+        if (toSlot is not null)
+        {
+            target = await FindItemBySlotAsync(toOwner.OwnerType, toOwner.OwnerId, toSlot.Value);
+            if (target is not null && !CanMerge(item, target, definition))
+                return new InventoryMutationResult { Status = InventoryMutationStatus.Conflict };
+        }
+        else if (definition.Stackable)
+        {
+            target = await FindMergeTargetAsync(toOwner.OwnerType, toOwner.OwnerId, item.ItemKey, definition.MaxStackSize);
+            if (target is not null)
+                toSlot = target.Slot;
+        }
 
-        var target = await FindItemBySlotAsync(toOwner.OwnerType, toOwner.OwnerId, toSlot.Value);
-        if (target is not null && !CanMerge(item, target, definition))
-            return new InventoryMutationResult { Status = InventoryMutationStatus.Conflict };
+        if (toSlot is null)
+        {
+            toSlot = await FindFirstOpenSlotAsync(toOwner.OwnerType, toOwner.OwnerId);
+            if (toSlot is null)
+                return new InventoryMutationResult { Status = InventoryMutationStatus.Conflict };
+            target = null;
+        }
 
         if (target is not null)
         {
@@ -521,6 +536,20 @@ public class InventoryStore
         return slot;
     }
 
+    private async Task<InventoryItem?> FindMergeTargetAsync(string ownerType, string ownerId, string itemKey, int maxStackSize)
+    {
+        var normalizedItemKey = NormalizeItemKey(itemKey);
+        return await _items.Find(i =>
+                i.OwnerType == ownerType &&
+                i.OwnerId == ownerId &&
+                i.ItemKey == normalizedItemKey &&
+                i.EquippedSlot == null &&
+                i.Slot != null &&
+                i.Quantity < maxStackSize)
+            .SortBy(i => i.Slot)
+            .FirstOrDefaultAsync();
+    }
+
     private Task<InventoryItem?> FindItemBySlotAsync(string ownerType, string ownerId, int slot, IClientSessionHandle? session = null)
         => session is null
             ? FindItemBySlotNoSessionAsync(ownerType, ownerId, slot)