Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
The first time each Ritual Summoned monster would be destroyed by battle each turn, it is not destroyed. If a "Megalith" monster is Special Summoned (except during the Damage Step): You can target 1 Ritual Monster in your GY; add it to your hand. You can only use this effect of "Megalith Portal" once per turn.
--メガリス・ポータル
--Megalith Portal
local s,id=GetID()
function s.initial_effect(c)
	--activate
	local e1=Effect.CreateEffect(c)
	e1:SetType(EFFECT_TYPE_ACTIVATE)
	e1:SetCode(EVENT_FREE_CHAIN)
	c:RegisterEffect(e1)
	--indes
	local e2=Effect.CreateEffect(c)
	e2:SetType(EFFECT_TYPE_FIELD)
	e2:SetCode(EFFECT_INDESTRUCTABLE_COUNT)
	e2:SetRange(LOCATION_FZONE)
	e2:SetTargetRange(LOCATION_MZONE,LOCATION_MZONE)
	e2:SetTarget(aux.TargetBoolFunction(Card.IsSummonType,SUMMON_TYPE_RITUAL))
	e2:SetValue(s.indct)
	c:RegisterEffect(e2)
	--to hand
	local e3=Effect.CreateEffect(c)
	e3:SetDescription(aux.Stringid(id,0))
	e3:SetCategory(CATEGORY_TOHAND)
	e3:SetType(EFFECT_TYPE_FIELD+EFFECT_TYPE_TRIGGER_O)
	e3:SetCode(EVENT_SPSUMMON_SUCCESS)
	e3:SetProperty(EFFECT_FLAG_DELAY+EFFECT_FLAG_CARD_TARGET)
	e3:SetRange(LOCATION_FZONE)
	e3:SetCountLimit(1,id)
	e3:SetCondition(s.thcon)
	e3:SetTarget(s.thtg)
	e3:SetOperation(s.thop)
	c:RegisterEffect(e3)
end
s.listed_series={SET_MEGALITH}
function s.indct(e,re,r,rp)
	if (r&REASON_BATTLE)~=0 then
		return 1
	else
		return 0
	end
end
function s.thcon(e,tp,eg,ep,ev,re,r,rp)
	return eg:IsExists(Card.IsSetCard,1,nil,SET_MEGALITH)
end
function s.thfilter(c)
	return c:IsRitualMonster() and c:IsAbleToHand()
end
function s.thtg(e,tp,eg,ep,ev,re,r,rp,chk,chkc)
	if chkc then return chkc:IsControler(tp) and chkc:IsLocation(LOCATION_GRAVE) and s.thfilter(chkc) end
	if chk==0 then return Duel.IsExistingTarget(s.thfilter,tp,LOCATION_GRAVE,0,1,nil) end
	Duel.Hint(HINT_SELECTMSG,tp,HINTMSG_ATOHAND)
	local g=Duel.SelectTarget(tp,s.thfilter,tp,LOCATION_GRAVE,0,1,1,nil)
	Duel.SetOperationInfo(0,CATEGORY_TOHAND,g,1,0,0)
end
function s.thop(e,tp,eg,ep,ev,re,r,rp)
	local tc=Duel.GetFirstTarget()
	if tc:IsRelateToEffect(e) then
		Duel.SendtoHand(tc,nil,REASON_EFFECT)
	end
end