【数据存储】榜单快照：排行榜的历史归档与对比

---榜单快照：每周一的零点归档
setontimerex(109, 3600)
function RankSnap.archive()
    -- 每周一 00:05 归档上周终榜
    if os.date("%w") ~= "1" or os.date("%H%M") ~= "0005" then
        return
    end
    local week = os.date("%Y%W", os.time() - 7 * 86400)
    local top = Cache.get("rank_level")
    DB.exec("INSERT INTO rank_history SET ?", {
        week = week, type = "level",
        data = Snapshot.serialize(top),
    })
    Ops.log("榜单归档完成: " .. week)
end

---周对比：进步榜与掉出榜
function RankSnap.compare(weekA, weekB)
    local a = RankSnap.load(weekA)
    local b = RankSnap.load(weekB)
    local rise, fall = {}, {}
    for name, rank in pairs(b) do
        local old = a[name]
        if not old then
            rise[#rise + 1] = { name = name, rank = rank }
        elseif old.rank - rank >= 50 then
            rise[#rise + 1] = { name = name, rank = rank }
        elseif rank - old.rank >= 100 then
            fall[#fall + 1] = { name = name, rank = rank }
        end
    end
    return rise, fall
end