/**
 * monitor.js — 数据监控器
 * 环形缓冲记录所有 WebSocket 收发消息，15 分钟自动清理超时记录
 */
var MonitorRing = (function() {
    var records = [];
    var MAX_RECORDS = 500;
    var TTL_MS = 900000; // 15 分钟
    var cleanTimer = null;

    function push(dir, raw) {
        var now = Date.now();
        records.push({
            time: now,
            dir: dir,    // '↑' 上行发送, '↓' 下行接收
            data: raw
        });

        // 超出上限时截掉旧数据
        while (records.length > MAX_RECORDS) {
            records.shift();
        }
    }

    function getAll() {
        return records.slice();
    }

    function count() {
        return records.length;
    }

    function cleanOld() {
        var cutoff = Date.now() - TTL_MS;
        var i = 0;
        while (i < records.length && records[i].time < cutoff) {
            i++;
        }
        if (i > 0) {
            records.splice(0, i);
        }
    }

    function clear() {
        records = [];
    }

    // 每 60 秒自动清理
    function startAutoClean() {
        if (cleanTimer) return;
        cleanTimer = setInterval(cleanOld, 60000);
    }

    function stopAutoClean() {
        if (cleanTimer) {
            clearInterval(cleanTimer);
            cleanTimer = null;
        }
    }

    // 启动自动清理
    startAutoClean();

    return {
        push: push,
        getAll: getAll,
        count: count,
        cleanOld: cleanOld,
        clear: clear
    };
})();