feat: Use null to indicate empty slots to keep inventory order

autoloads/inventory_manager.gd

@@ -14,12 +14,14 @@ signal add_to_inventory(item_id: String, amount: int)
 signal remove_from_inventory(item_id: String, amount: int)
 signal item_added(item_id: String, amount: int)
 signal item_removed(item_id: String, amount: int)
+signal inventory_slot_cleared(slot_index: int)
+
 
 var quick_slot_item_id: String = "001"
 
 var max_inventory_items: int = 40 # 4 rows of 10
 
-var inventory: Array[DBItemResource] = []
+var inventory: Array[DBItemResource] = [] ## To ensure inventory is automatically sorted, "empty" inventory cells will be replaced with null to keep positions
 var _inventory_cache: Dictionary[String, Dictionary] = {} ## Used for caching certain information
 
 
@@ -50,13 +52,15 @@ func available_space(item_id: String) -> int:
 
 
 func _find_stacks_by_id(item_resource: DBItemResource, item_id: String) -> bool:
-	return item_resource.id == item_id
+	return item_resource != null and item_resource.id == item_id
 
 ## Find the stack where at least one item can be added
 func _find_stacks_with_space(item_resource: DBItemResource, item_id: String) -> bool:
 	return (
-		item_resource.id == item_id and
-		item_resource.amount < item_resource.max_stack_size
+		item_resource == null or (
+			item_resource.id == item_id and
+			item_resource.amount < item_resource.max_stack_size
+		)
 	)
 
 func _update_cache_total(item_id: String, amount: int) -> void:
@@ -81,8 +85,9 @@ func _on_add_to_inventory(item_id: String, amount: int = 1) -> void:
 	while amount_remaining > 0:
 		var first_stack_index: int = inventory.find_custom(_find_stacks_with_space.bind(item_id))
 
+		var stack_resource: DBItemResource
 		if first_stack_index == -1 and inventory.size() < max_inventory_items: # No existing stack and empty slots available
-			var stack_resource: DBItemResource = item_resource.duplicate()
+			stack_resource = item_resource.duplicate()
 			inventory.append(stack_resource)
 
 			if amount_remaining <= stack_resource.max_stack_size:
@@ -94,7 +99,10 @@ func _on_add_to_inventory(item_id: String, amount: int = 1) -> void:
 				inventory[-1].amount = stack_resource.max_stack_size
 				amount_remaining -= stack_resource.max_stack_size
 		elif first_stack_index > -1:
-			var stack_resource: DBItemResource = inventory[first_stack_index]
+			if  inventory[first_stack_index] == null: # Empty slot
+				inventory[first_stack_index] = item_resource.duplicate()
+
+			stack_resource = inventory[first_stack_index]
 			var current_amount: int = stack_resource.amount
 			var total_amount: int = current_amount + amount_remaining
 			if total_amount < stack_resource.max_stack_size: # Stack not full and has space
@@ -125,8 +133,9 @@ func _on_remove_from_inventory(item_id: String, amount: int = 1) -> void:
 			else:
 				var to_remove: int = stack_resource.max_stack_size - current_stack_amount
 				_update_cache_total(item_id, -amount_remaining)
-				inventory.remove_at(last_stack_index)
+				inventory[last_stack_index] = null
 				amount_remaining -= to_remove
+				inventory_slot_cleared.emit(last_stack_index)
 		else: # Received more to remove than we had stacks of
 			amount_remaining = 0