Make industrialtest.api.addPower accept negative power amount

api.lua

@@ -19,11 +19,15 @@ local S=minetest.get_translator("industrialtest")
 industrialtest.api={}
 industrialtest.api.maceratorRecipes={}
 
+local function clamp(num,min,max)
+	return math.max(math.min(num,max),min)
+end
+
 -- \brief Adds power storage to metadata
 -- \param capacity How much EU item/node can store
 -- \param flow How much EU can flow in or out item/node per industrialtest.updateDelay
 -- \param ioConfig Input/Output configuration in following side order: -X, +X, -Y, +Y, -Z, +Z
---				   a - bidirectional, i - input, o - output
+--                 a - bidirectional, i - input, o - output
 -- \returns nil
 industrialtest.api.addPowerStorage=function(meta,capacity,flow,ioConfig)
 	meta:set_int("industrialtest.powerCapacity",capacity)
@@ -93,13 +97,10 @@ end
 industrialtest.api.addPower=function(meta,amount)
 	local powerAmount=meta:get_int("industrialtest.powerAmount")
 	local powerCapacity=meta:get_int("industrialtest.powerCapacity")
-	if powerAmount+amount>powerCapacity then
-		local addedAmount=powerCapacity-powerAmount
-		meta:set_int("industrialtest.powerAmount",powerCapacity)
-		return addedAmount
-	end
-	meta:set_int("industrialtest.powerAmount",powerAmount+amount)
-	return amount
+	local prevPowerAmount=powerAmount
+	powerAmount=clamp(powerAmount+amount,0,powerCapacity)
+	meta:set_int("industrialtest.powerAmount",powerAmount)
+	return powerAmount-prevPowerAmount
 end
 industrialtest.api.addPowerToItem=function(itemstack,amount)
 	local meta=itemstack:get_meta()