【进阶实战】限时秒杀：库存预扣与超卖防护封装

local function trySeckill(actor, sku)
    local bought = tonumber(getplayvar(actor, 0, "Bought_" .. sku)) or 0
    if bought >= 2 then
        sendmsg(actor, 1, "每人限购 2 件，已达上限。")
        return false
    end
    local stock = tonumber(getsysvar("Seckill_" .. sku)) or 0
    if stock <= 0 then
        sendmsg(actor, 1, "本轮已售罄。")
        return false
    end
    setsysvarex("Seckill_" .. sku, stock - 1, 1)
    setplayvar(actor, 0, "Bought_" .. sku, bought + 1, 1)
    giveitem(actor, "转生证明", 1, 1, "秒杀购得")
    return true
end

local function refundSeckill(actor, sku)
    local stock = tonumber(getsysvar("Seckill_" .. sku)) or 0
    setsysvarex("Seckill_" .. sku, stock + 1, 1)
    local bought = tonumber(getplayvar(actor, 0, "Bought_" .. sku)) or 0
    setplayvar(actor, 0, "Bought_" .. sku, math.max(bought - 1, 0), 1)
    sendmsg(actor, 1, "发货失败已回滚，名额已返还。")
end