Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
Target 1 face-up Attack Position monster on the field; change it to face-up Defense Position, also any damage you take for the rest of this turn is halved.
--幻蝶の護り
--Butterspy Protection
local s,id=GetID()
function s.initial_effect(c)
	--Activate
	local e1=Effect.CreateEffect(c)
	e1:SetCategory(CATEGORY_POSITION)
	e1:SetType(EFFECT_TYPE_ACTIVATE)
	e1:SetProperty(EFFECT_FLAG_CARD_TARGET)
	e1:SetCode(EVENT_FREE_CHAIN)
	e1:SetTarget(s.target)
	e1:SetOperation(s.operation)
	c:RegisterEffect(e1)
end
function s.filter(c)
	return c:IsPosition(POS_FACEUP_ATTACK) and c:IsCanChangePosition()
end
function s.target(e,tp,eg,ep,ev,re,r,rp,chk,chkc)
	if chkc then return chkc:IsLocation(LOCATION_MZONE) and s.filter(chkc) end
	if chk==0 then return Duel.IsExistingTarget(s.filter,tp,LOCATION_MZONE,LOCATION_MZONE,1,nil) end
	Duel.Hint(HINT_SELECTMSG,tp,HINTMSG_POSCHANGE)
	Duel.SelectTarget(tp,s.filter,tp,LOCATION_MZONE,LOCATION_MZONE,1,1,nil)
end
function s.operation(e,tp,eg,ep,ev,re,r,rp)
	local tc=Duel.GetFirstTarget()
	if tc and tc:IsRelateToEffect(e) and tc:IsPosition(POS_FACEUP_ATTACK) then
		Duel.ChangePosition(tc,POS_FACEUP_DEFENSE)
	end
	if e:IsHasType(EFFECT_TYPE_ACTIVATE) then
		local e1=Effect.CreateEffect(e:GetHandler())
		e1:SetType(EFFECT_TYPE_FIELD)
		e1:SetCode(EFFECT_CHANGE_DAMAGE)
		e1:SetProperty(EFFECT_FLAG_PLAYER_TARGET)
		e1:SetTargetRange(1,0)
		e1:SetValue(s.val)
		e1:SetReset(RESET_PHASE|PHASE_END,1)
		Duel.RegisterEffect(e1,tp)
	end
end
function s.val(e,re,val,r,rp,rc)
	return math.floor(val/2)
end