【进阶实战】优雅降级：依赖服务不可用时的兜底封装

local lastRankSnapshot = {}
local function getRankList()
    local ok, result = pcall(fetchRemoteRank)
    if ok and result and #result > 0 then
        lastRankSnapshot = result
        return { list = result, degraded = false }
    end
    return { list = lastRankSnapshot, degraded = true }
end
local function showRank(actorName)
    local actor = getplayerbyname(actorName)
    local resp = getRankList()
    if resp.degraded then
        sendmsg(actor, 1, "跨服榜单暂时不可用，显示本服快照。")
    end
    for i, row in ipairs(resp.list) do
        sendmsg(actor, 1, i .. "." .. row.name .. " " .. row.score)
    end
end

local DEFAULT_CFG = { dropRate = 100, maxJoin = 50 }
local function loadActCfg()
    local ok, cfg = pcall(readActCfg)
    if ok and type(cfg) == "table" then
        for k, v in pairs(DEFAULT_CFG) do
            if cfg[k] == nil then
                cfg[k] = v
            end
        end
        return cfg
    end
    local fallback = {}
    for k, v in pairs(DEFAULT_CFG) do
        fallback[k] = v
    end
    return fallback
end