Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
Target 1 face-up monster on the field; equip this card to that target. It gains 500 ATK. If the equipped monster battles while in Defense Position, it gains DEF equal to its ATK during damage calculation only.
--鎖付き尖盾
--Spikeshield with Chain
local s,id=GetID()
function s.initial_effect(c)
	--Activate
	local e1=Effect.CreateEffect(c)
	e1:SetCategory(CATEGORY_EQUIP)
	e1:SetType(EFFECT_TYPE_ACTIVATE)
	e1:SetCode(EVENT_FREE_CHAIN)
	e1:SetHintTiming(TIMING_DAMAGE_STEP)
	e1:SetProperty(EFFECT_FLAG_CARD_TARGET+EFFECT_FLAG_DAMAGE_STEP)
	e1:SetCondition(aux.StatChangeDamageStepCondition)
	e1:SetCost(aux.RemainFieldCost)
	e1:SetTarget(s.target)
	e1:SetOperation(s.operation)
	c:RegisterEffect(e1)
end
function s.target(e,tp,eg,ep,ev,re,r,rp,chk,chkc)
	if chkc then return chkc:IsLocation(LOCATION_MZONE) and chkc:IsFaceup() end
	if chk==0 then return e:IsHasType(EFFECT_TYPE_ACTIVATE) 
		and Duel.IsExistingTarget(Card.IsFaceup,tp,LOCATION_MZONE,LOCATION_MZONE,1,nil) end
	Duel.Hint(HINT_SELECTMSG,tp,HINTMSG_EQUIP)
	Duel.SelectTarget(tp,Card.IsFaceup,tp,LOCATION_MZONE,LOCATION_MZONE,1,1,nil)
	Duel.SetOperationInfo(0,CATEGORY_EQUIP,e:GetHandler(),1,0,0)
end
function s.operation(e,tp,eg,ep,ev,re,r,rp)
	local c=e:GetHandler()
	if not c:IsLocation(LOCATION_SZONE) or not c:IsRelateToEffect(e) or c:IsStatus(STATUS_LEAVE_CONFIRMED) then return end
	local tc=Duel.GetFirstTarget()
	if tc:IsRelateToEffect(e) and tc:IsFaceup() then
		Duel.Equip(tp,c,tc)
		--Atkup
		local e1=Effect.CreateEffect(c)
		e1:SetType(EFFECT_TYPE_EQUIP)
		e1:SetCode(EFFECT_UPDATE_ATTACK)
		e1:SetValue(500)
		e1:SetReset(RESET_EVENT|RESETS_STANDARD)
		c:RegisterEffect(e1)
		--def
		local e2=Effect.CreateEffect(c)
		e2:SetType(EFFECT_TYPE_EQUIP)
		e2:SetCode(EFFECT_UPDATE_DEFENSE)
		e2:SetCondition(s.defcon)
		e2:SetValue(s.defval)
		e2:SetReset(RESET_EVENT|RESETS_STANDARD)
		c:RegisterEffect(e2)
		--Equip limit
		local e3=Effect.CreateEffect(c)
		e3:SetType(EFFECT_TYPE_SINGLE)
		e3:SetCode(EFFECT_EQUIP_LIMIT)
		e3:SetProperty(EFFECT_FLAG_CANNOT_DISABLE)
		e3:SetValue(1)
		e3:SetReset(RESET_EVENT|RESETS_STANDARD)
		c:RegisterEffect(e3)
	else
		c:CancelToGrave(false)
	end
end
function s.defcon(e)
	if Duel.GetCurrentPhase()~=PHASE_DAMAGE_CAL then return false end
	local eq=e:GetHandler():GetEquipTarget()
	return (eq==Duel.GetAttacker() or eq==Duel.GetAttackTarget()) and eq:IsDefensePos()
end
function s.defval(e,c)
	return c:GetAttack()
end