材料自动补购：不足时自动商城补齐差额

local function craft(actor)
    takeitem(actor, "强化石", 20, 0, "合成消耗")   -- 不足直接失败
end

local PRICE = 100
local function craft(actor, have, need)
    local lack = need - have
    if lack > 0 then
        takeitem(actor, "金元", lack * PRICE, 0,
            "材料自动补购")
        sendmsg(actor, 1, "自动补购强化石 " .. lack .. " 个")
    end
    takeitem(actor, "强化石", need, 0, "合成消耗")
end
craft(actor, 12, 20)