Generate a YGOPro Lua script for the following Yu-Gi-Oh card effect:
When your opponent Special Summons a monster (except during the Damage Step): You can discard 1 card; Special Summon this card from your hand or Graveyard. There can only be 1 "Dragon Ice" on the field.
--ドラゴン・アイス
--Dragon Ice
local s,id=GetID()
function s.initial_effect(c)
	c:SetUniqueOnField(1,1,id)
	--spsummon
	local e1=Effect.CreateEffect(c)
	e1:SetDescription(aux.Stringid(id,0))
	e1:SetCategory(CATEGORY_SPECIAL_SUMMON)
	e1:SetType(EFFECT_TYPE_FIELD+EFFECT_TYPE_TRIGGER_O)
	e1:SetRange(LOCATION_HAND|LOCATION_GRAVE)
	e1:SetCode(EVENT_SPSUMMON_SUCCESS)
	e1:SetCondition(s.spcon)
	e1:SetCost(s.spcost)
	e1:SetTarget(s.sptg)
	e1:SetOperation(s.spop)
	c:RegisterEffect(e1)
end
function s.cfilter(c,tp)
	return c:IsSummonPlayer(1-tp)
end
function s.spcon(e,tp,eg,ep,ev,re,r,rp)
	return eg:IsExists(Card.IsSummonPlayer,1,nil,1-tp)
end
function s.spcost(e,tp,eg,ep,ev,re,r,rp,chk)
	local exc=(e:GetHandler():IsLocation(LOCATION_HAND) and not e:GetHandler():IsAbleToGraveAsCost()) and e:GetHandler() or nil
	if chk==0 then return Duel.IsExistingMatchingCard(Card.IsDiscardable,tp,LOCATION_HAND,0,1,exc) end
	Duel.DiscardHand(tp,Card.IsDiscardable,1,1,REASON_COST|REASON_DISCARD,exc)
end
function s.sptg(e,tp,eg,ep,ev,re,r,rp,chk)
	if chk==0 then return Duel.GetLocationCount(tp,LOCATION_MZONE)>0
		and e:GetHandler():IsCanBeSpecialSummoned(e,0,tp,false,false) end
	Duel.SetOperationInfo(0,CATEGORY_SPECIAL_SUMMON,e:GetHandler(),1,0,0)
	Duel.SetTargetCard(e:GetHandler())
end
function s.spop(e,tp,eg,ep,ev,re,r,rp)
	local c=e:GetHandler()
	if not c:IsRelateToEffect(e) then return end
	Duel.SpecialSummon(c,0,tp,tp,false,false,POS_FACEUP)
end