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--
-- All or portions of this file Copyright (c) Amazon.com, Inc. or its affiliates or
-- its licensors.
--
-- For complete copyright and license terms please see the LICENSE at the root of this
-- distribution (the "License"). All use of this software is governed by the License,
-- or, if provided, by the license below or the license accompanying this file. Do not
-- remove or modify any license notices. This file is distributed on an "AS IS" BASIS,
-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
--
--
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local DropTargetStacking = 
{
    Properties = 
    {
	},
}

function DropTargetStacking:IsValidDrop(draggable, dropTarget)
	local sourceDraggableImage = UiElementBus.Event.GetChild(draggable, 0)
	local sourceType = UiImageBus.Event.GetSpritePathname(sourceDraggableImage)

	local destType = ""
	if (UiElementBus.Event.GetNumChildElements(dropTarget) > 0) then
		local destDraggable = UiElementBus.Event.GetChild(dropTarget, 0)
		local destDraggableImage = UiElementBus.Event.GetChild(destDraggable, 0)
		destType = UiImageBus.Event.GetSpritePathname(destDraggableImage)
	end

	if (destType == "" or sourceType == destType) then
		return true
	else
		return false
	end
end

function DropTargetStacking:OnActivate()
	self.dropTargetHandler = UiDropTargetNotificationBus.Connect(self, self.entityId)
end

function DropTargetStacking:OnDeactivate()
	self.dropTargetHandler:Disconnect()
end

function DropTargetStacking:OnDropHoverStart(draggable)
	if (self:IsValidDrop(draggable, self.entityId)) then
		UiDraggableBus.Event.SetDragState(draggable, eUiDragState_Valid)
		UiDropTargetBus.Event.SetDropState(self.entityId, eUiDropState_Valid)
	else
		UiDraggableBus.Event.SetDragState(draggable, eUiDragState_Invalid)
		UiDropTargetBus.Event.SetDropState(self.entityId, eUiDropState_Invalid)
	end
end

function DropTargetStacking:OnDropHoverEnd(draggable)
	UiDraggableBus.Event.SetDragState(draggable, eUiDragState_Normal)
	UiDropTargetBus.Event.SetDropState(self.entityId, eUiDropState_Normal)
end

function DropTargetStacking:OnDrop(draggable)
	if (not self:IsValidDrop(draggable, self.entityId)) then
		return
	end
	
	-- get the source inventory count
	local sourceInventoryCount = 0
	local draggableImage = UiElementBus.Event.GetChild(draggable, 0)
	local draggableCounterBox = UiElementBus.Event.GetChild(draggableImage, 0)
	local draggableCounterText = UiElementBus.Event.GetChild(draggableCounterBox, 0)
	local textString = UiTextBus.Event.GetText(draggableCounterText)
	sourceInventoryCount = tonumber(textString)

	-- get the dest inventory count
	local destInventoryCount = 0
	local destChildCount = UiElementBus.Event.GetNumChildElements(self.entityId)
	local destDraggable = EntityId()
	local destDraggableCounterText = EntityId()
	local destTextString = ""
	if (destChildCount > 0) then
		destDraggable = UiElementBus.Event.GetChild(self.entityId, 0)
		
		if (destDraggable == draggable) then
			-- draggable was dropped on its original (current) slot - do nothing
			return
		end
		local destDraggableImage = UiElementBus.Event.GetChild(destDraggable, 0)
		local destDraggableCounterBox = UiElementBus.Event.GetChild(destDraggableImage, 0)
		destDraggableCounterText = UiElementBus.Event.GetChild(destDraggableCounterBox, 0)
		destTextString = UiTextBus.Event.GetText(destDraggableCounterText)
		destInventoryCount = tonumber(destTextString)
	end
	
	if (destInventoryCount == 0 and sourceInventoryCount == 1) then
		UiElementBus.Event.Reparent(draggable, self.entityId, EntityId())
	else
		if (destInventoryCount == 0) then
			local canvasEntity = UiElementBus.Event.GetCanvas(self.entityId)
			local clonedElement = UiCanvasBus.Event.CloneElement(canvasEntity, draggable, self.entityId, EntityId())
			-- set the count on the cloned element to one
			local clonedImage = UiElementBus.Event.GetChild(clonedElement, 0)
			local clonedCounterBox = UiElementBus.Event.GetChild(clonedImage, 0)
			local clonedCounterText = UiElementBus.Event.GetChild(clonedCounterBox, 0)
			UiTextBus.Event.SetText(clonedCounterText, "1")
			-- if using keyboard/gamepad make the we want to make sure the hover moves
			UiCanvasBus.Event.ForceHoverInteractable(canvasEntity, clonedElement)
		else
			-- increment dest
			destInventoryCount = destInventoryCount + 1
			destTextString = destInventoryCount
			UiTextBus.Event.SetText(destDraggableCounterText, destTextString)
			-- if using keyboard/gamepad make the we want to make sure the hover moves
			local canvasEntity = UiElementBus.Event.GetCanvas(self.entityId)
			UiCanvasBus.Event.ForceHoverInteractable(canvasEntity, destDraggable)
		end
		if (sourceInventoryCount == 1) then
			UiElementBus.Event.DestroyElement(draggable)
		else
			-- decrement source
			sourceInventoryCount = sourceInventoryCount - 1
			textString = sourceInventoryCount
			UiTextBus.Event.SetText(draggableCounterText, textString)
		end
	end
end

return DropTargetStacking