【高级技巧】环形日志：最近N条错误的结构化留存

local ring, head, cap = {}, 0, 50
local function logError(module, code, brief)
    head = head % cap + 1
    ring[head] = {
        at = os.date("%H:%M:%S"),
        module = module,
        code = code,
        brief = brief,
    }
end
local function dumpErrors(actor)
    actor = getplayerbyname(actor)
    for i = 0, cap - 1 do
        local idx = (head - i - 1) % cap + 1
        local e = ring[idx]
        if e then
            sendmsg(actor, 1, e.at .. " [" .. e.module .. "#" .. e.code .. "] " .. e.brief)
        end
    end
end

local function onTradeFail(actor, code, brief)
    logError("trade", code, brief)
    sendmsg(actor, 1, "交易失败，错误码 " .. code .. "。")
end