scope NoItemDuplicates initializer init
	import SimError

	function countItems takes unit u, item i returns integer
		integer typ = GetItemTypeId(i)
		integer index = 0
		integer count = 0

		loop
			exitwhen index > 5

			if GetItemTypeId(UnitItemInSlot(u, index)) == typ then
				count++
			end

			index++
		end

		return count
	end

	function act takes nothing returns boolean
		unit t = GetTriggerUnit()
		item i = GetManipulatedItem()

		if countItems(t, i) > 1 then
			UnitDropItemPoint(t, i, t.getX(), t.getY())
			simError(t.getOwner(), "You can't carry two of the same item.")
		end
		return false
	end

	function init takes nothing returns nothing
		trigger trig = CreateTrigger()
		trig..registerAnyUnitEvent(EVENT_PLAYER_UNIT_PICKUP_ITEM)..addCondition(Condition(function act))
	end
endscope