【框架设计】商店系统：限时商品与库存的销售框架

local SHOP_CFG = {
    daily_shop = {
        refresh = "daily",
        items = {
            { id = 2001, price = 80, currency = "gold",  limit = 1, perDay = true },
            { id = 3002, price = 45, currency = "bind",  limit = 5 },
        },
    },
}

function Shop.buy(player, shopId, itemId, count)
    local item = findItem(shopId, itemId)
    if not item then return false, "商品不存在" end
    if count > item.limit - boughtCount(player, itemId) then
        return false, "超出限购数量"
    end
    local cost = item.price * count
    if not Currency.has(player, item.currency, cost) then
        return false, "货币不足"
    end
    Currency.deduct(player, item.currency, cost)
    BagService.addItem(player.id, itemId, count)
    recordPurchase(player, itemId, count, cost)
    return true
end