Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
Once per turn: You can target 1 Level 4 or lower monster you control; it can attack your opponent directly this turn. Send it to the Graveyard at the end of the Battle Phase.
--ウィルスメール
--Infected Mail
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)
	--direct attack
	local e2=Effect.CreateEffect(c)
	e2:SetDescription(aux.Stringid(id,0))
	e2:SetType(EFFECT_TYPE_IGNITION)
	e2:SetProperty(EFFECT_FLAG_CARD_TARGET)
	e2:SetRange(LOCATION_SZONE)
	e2:SetCountLimit(1)
	e2:SetCondition(s.atcon)
	e2:SetTarget(s.attg)
	e2:SetOperation(s.atop)
	c:RegisterEffect(e2)
end
function s.atcon(e,tp,eg,ep,ev,re,r,rp)
	return Duel.IsAbleToEnterBP()
end
function s.filter(c)
	return c:IsFaceup() and c:IsLevelBelow(4) and c:CanAttack() and not c:IsHasEffect(EFFECT_DIRECT_ATTACK)
end
function s.attg(e,tp,eg,ep,ev,re,r,rp,chk,chkc)
	if chkc then return chkc:IsLocation(LOCATION_MZONE) and chkc:IsControler(tp) and s.filter(chkc) end
	if chk==0 then return Duel.IsExistingTarget(s.filter,tp,LOCATION_MZONE,0,1,nil) end
	Duel.Hint(HINT_SELECTMSG,tp,HINTMSG_FACEUP)
	Duel.SelectTarget(tp,s.filter,tp,LOCATION_MZONE,0,1,1,nil)
end
function s.atop(e,tp,eg,ep,ev,re,r,rp)
	local c=e:GetHandler()
	if not c:IsRelateToEffect(e) then return end
	local tc=Duel.GetFirstTarget()
	if tc:IsFaceup() and tc:IsRelateToEffect(e) then
		local e1=Effect.CreateEffect(c)
		e1:SetType(EFFECT_TYPE_SINGLE)
		e1:SetCode(EFFECT_DIRECT_ATTACK)
		e1:SetReset(RESETS_STANDARD_PHASE_END)
		tc:RegisterEffect(e1)
		tc:RegisterFlagEffect(id,RESET_EVENT|RESETS_STANDARD,0,1)
		local e2=Effect.CreateEffect(c)
		e2:SetType(EFFECT_TYPE_FIELD+EFFECT_TYPE_CONTINUOUS)
		e2:SetCode(EVENT_PHASE|PHASE_BATTLE)
		e2:SetProperty(EFFECT_FLAG_IGNORE_IMMUNE)
		e2:SetCountLimit(1)
		e2:SetLabelObject(tc)
		e2:SetCondition(s.tgcon)
		e2:SetOperation(s.tgop)
		Duel.RegisterEffect(e2,tp)
	end
end
function s.tgcon(e,tp,eg,ep,ev,re,r,rp)
	local tc=e:GetLabelObject()
	if tc:GetFlagEffect(id)~=0 then
		return true
	else
		e:Reset()
		return false
	end
end
function s.tgop(e,tp,eg,ep,ev,re,r,rp)
	local tc=e:GetLabelObject()
	Duel.SendtoGrave(tc,REASON_EFFECT)
end