Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
If this card attacks a Defense Position monster, inflict piercing battle damage. If this card inflicts battle damage to your opponent: Make your opponent discard 1 random card.
--地獄将軍・メフィスト
--Mefist the Infernal General
local s,id=GetID()
function s.initial_effect(c)
	--handes
	local e1=Effect.CreateEffect(c)
	e1:SetDescription(aux.Stringid(id,0))
	e1:SetCategory(CATEGORY_HANDES)
	e1:SetType(EFFECT_TYPE_SINGLE+EFFECT_TYPE_TRIGGER_F)
	e1:SetCode(EVENT_BATTLE_DAMAGE)
	e1:SetCondition(s.condition)
	e1:SetTarget(s.target)
	e1:SetOperation(s.operation)
	c:RegisterEffect(e1)
	--pierce
	local e2=Effect.CreateEffect(c)
	e2:SetType(EFFECT_TYPE_SINGLE)
	e2:SetCode(EFFECT_PIERCE)
	c:RegisterEffect(e2)
end
function s.condition(e,tp,eg,ep,ev,re,r,rp)
	return ep~=tp
end
function s.target(e,tp,eg,ep,ev,re,r,rp,chk)
	if chk==0 then return true end
	Duel.SetOperationInfo(0,CATEGORY_HANDES,0,0,1-tp,1)
end
function s.operation(e,tp,eg,ep,ev,re,r,rp)
	local g=Duel.GetFieldGroup(ep,LOCATION_HAND,0)
	if #g==0 then return end
	local sg=g:RandomSelect(ep,1)
	Duel.SendtoGrave(sg,REASON_DISCARD|REASON_EFFECT)
end