Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
While the equipped monster is attacking, it cannot be destroyed by battle. At the end of the Damage Step, if the equipped monster attacked: The attack target loses ATK equal to the ATK of the equipped monster, until the End Phase.
--ロケット・パイルダー
--Rocket Pilder
local s,id=GetID()
function s.initial_effect(c)
	aux.AddEquipProcedure(c)
	--indes
	local e2=Effect.CreateEffect(c)
	e2:SetType(EFFECT_TYPE_EQUIP)
	e2:SetCode(EFFECT_INDESTRUCTABLE_BATTLE)
	e2:SetCondition(s.indcon)
	e2:SetValue(1)
	c:RegisterEffect(e2)
	--atkdown
	local e4=Effect.CreateEffect(c)
	e4:SetDescription(aux.Stringid(id,0))
	e4:SetCategory(CATEGORY_ATKCHANGE)
	e4:SetType(EFFECT_TYPE_FIELD+EFFECT_TYPE_TRIGGER_F)
	e4:SetRange(LOCATION_SZONE)
	e4:SetCode(EVENT_DAMAGE_STEP_END)
	e4:SetCondition(s.atkcon)
	e4:SetOperation(s.atkop)
	c:RegisterEffect(e4)
end
function s.indcon(e)
	return Duel.GetAttacker()==e:GetHandler():GetEquipTarget()
end
function s.atkcon(e,tp,eg,ep,ev,re,r,rp)
	local at=Duel.GetAttackTarget()
	return at and at:IsRelateToBattle() and at:IsFaceup() and Duel.GetAttacker()==e:GetHandler():GetEquipTarget()
end
function s.atkop(e,tp,eg,ep,ev,re,r,rp)
	local c=e:GetHandler()
	local at=Duel.GetAttackTarget()
	if not c:IsRelateToEffect(e) or not at:IsRelateToBattle() or at:IsFacedown() then return end
	local atk=c:GetEquipTarget():GetAttack()
	local e1=Effect.CreateEffect(c)
	e1:SetType(EFFECT_TYPE_SINGLE)
	e1:SetCode(EFFECT_UPDATE_ATTACK)
	e1:SetValue(-atk)
	e1:SetReset(RESETS_STANDARD_PHASE_END)
	at:RegisterEffect(e1)
end