Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
Monsters you control gain 500 DEF for each "Ancient Fairy Dragon", and monsters that mention it, that you control. Once per Chain: You can target 1 face-up monster your opponent controls; until the end of this turn, its ATK/DEF become halved, also its effects are negated. You can use this effect of "Eternal Sunshine" a number of times per turn, up to the number of "Ancient Fairy Dragon", and monsters that mention it, that you control.
--エターナル・サンシャイン
--Eternal Sunshine
--Scripted by Eerie Code
local s,id=GetID()
function s.initial_effect(c)
	--Activate
	local e0=Effect.CreateEffect(c)
	e0:SetType(EFFECT_TYPE_ACTIVATE)
	e0:SetProperty(EFFECT_FLAG_DAMAGE_STEP)
	e0:SetCode(EVENT_FREE_CHAIN)
	e0:SetHintTiming(TIMING_DAMAGE_STEP)
	e0:SetCondition(aux.StatChangeDamageStepCondition)
	c:RegisterEffect(e0)
	--Monsters you control gain 500 DEF for each "Ancient Fairy Dragon", and monster that mentions it, that you control
	local e1=Effect.CreateEffect(c)
	e1:SetType(EFFECT_TYPE_FIELD)
	e1:SetCode(EFFECT_UPDATE_DEFENSE)
	e1:SetRange(LOCATION_SZONE)
	e1:SetTargetRange(LOCATION_MZONE,0)
	e1:SetValue(s.defval)
	c:RegisterEffect(e1)
	--Halve the current ATK/DEF and negate the effects of 1 opponent's monster until the end of that turn
	local e2=Effect.CreateEffect(c)
	e2:SetDescription(aux.Stringid(id,0))
	e2:SetCategory(CATEGORY_ATKCHANGE+CATEGORY_DEFCHANGE+CATEGORY_DISABLE)
	e2:SetType(EFFECT_TYPE_QUICK_O)
	e2:SetProperty(EFFECT_FLAG_CARD_TARGET+EFFECT_FLAG_DAMAGE_STEP)
	e2:SetCode(EVENT_FREE_CHAIN)
	e2:SetRange(LOCATION_SZONE)
	e2:SetHintTiming(TIMING_DAMAGE_STEP,TIMING_DAMAGE_STEP|TIMING_STANDBY_PHASE|TIMING_MAIN_END|TIMINGS_CHECK_MONSTER)
	e2:SetCountLimit(1,0,EFFECT_COUNT_CODE_CHAIN)
	e2:SetCondition(s.discon)
	e2:SetTarget(s.distg)
	e2:SetOperation(s.disop)
	c:RegisterEffect(e2)
end
s.listed_names={CARD_ANCIENT_FAIRY_DRAGON}
function s.afdfilter(c)
	return (c:IsCode(CARD_ANCIENT_FAIRY_DRAGON) or (c:ListsCode(CARD_ANCIENT_FAIRY_DRAGON) and c:IsMonster())) and c:IsFaceup()
end
function s.defval(e,c)
	return Duel.GetMatchingGroupCount(s.afdfilter,e:GetHandlerPlayer(),LOCATION_ONFIELD,0,nil)*500
end
function s.discon(e,tp,eg,ep,ev,re,r,rp)
	return Duel.GetFlagEffect(tp,id)<Duel.GetMatchingGroupCount(s.afdfilter,tp,LOCATION_ONFIELD,0,nil)
		and aux.StatChangeDamageStepCondition()
end
function s.distg(e,tp,eg,ep,ev,re,r,rp,chk,chkc)
	if chkc then return chkc:IsLocation(LOCATION_MZONE) and chkc:IsControler(1-tp) and chkc:IsFaceup() end
	if chk==0 then return Duel.IsExistingTarget(Card.IsFaceup,tp,0,LOCATION_MZONE,1,nil) end
	Duel.RegisterFlagEffect(tp,id,RESET_PHASE|PHASE_END,0,1)
	Duel.Hint(HINT_SELECTMSG,tp,HINTMSG_TARGET)
	local g=Duel.SelectTarget(tp,Card.IsFaceup,tp,0,LOCATION_MZONE,1,1,nil)
	Duel.SetOperationInfo(0,CATEGORY_DISABLE,g,1,tp,0)
end
function s.disop(e,tp,eg,ep,ev,re,r,rp)
	local tc=Duel.GetFirstTarget()
	if tc:IsRelateToEffect(e) and tc:IsFaceup() then
		local c=e:GetHandler()
		--Its current ATK/DEF become halved until the end of this turn
		local e1=Effect.CreateEffect(c)
		e1:SetType(EFFECT_TYPE_SINGLE)
		e1:SetProperty(EFFECT_FLAG_CANNOT_DISABLE)
		e1:SetCode(EFFECT_SET_ATTACK_FINAL)
		e1:SetValue(math.ceil(tc:GetAttack()/2))
		e1:SetReset(RESETS_STANDARD_PHASE_END)
		tc:RegisterEffect(e1)
		local e2=e1:Clone()
		e2:SetCode(EFFECT_SET_DEFENSE_FINAL)
		e2:SetValue(math.ceil(tc:GetDefense()/2))
		tc:RegisterEffect(e2)
		--Its effects are negated until the end of this turn
		tc:NegateEffects(c,RESETS_STANDARD_PHASE_END)
	end
end