【数据存储】黑市兑换：限量商品的库存账

---限量兑换：库存的原子校验扣减
function BlackMarket.exchange(actor, goodsId)
    local player = class(actor)
    if not player then return false end
    local goods = BlackMarket.goods[goodsId]
    if not goods or goods.stock <= 0 then
        sendmsg(actor, 1, "今日已售罄")
        return false
    end
    if not checkitemw(actor, "黑市令牌", goods.price) then
        sendmsg(actor, 1, "令牌不足，需要 " .. goods.price)
        return false
    end
    -- 校验与扣库存在同一临界区
    goods.stock = goods.stock - 1
    takeitem(actor, "黑市令牌", goods.price, 0, "黑市兑换")
    giveitem(actor, goods.item, 1)
    sendmsg(actor, 1, "兑换成功，剩余库存 " .. goods.stock)
    return true
end

---库存的快照推送：售罄即时可见
setontimerex(90, 5)
function BlackMarket.sync()
    local snap = {}
    for id, g in pairs(BlackMarket.goods) do
        snap[#snap + 1] = {
            id = id, stock = g.stock,
            soldOut = g.stock <= 0,
        }
    end
    BlackMarket.broadcast(snap)
end

---每日的重置：零点补货
function BlackMarket.restock()
    for _, g in pairs(BlackMarket.goods) do
        if g.daily then
            g.stock = g.dailyStock
        end
    end
    Ops.log("黑市每日补货完成")
end