var timingReporter = function() {
    var _dnsTime = performance.timing.domainLookupEnd - (performance.timing.domainLookupStart || 0),
        _tcpTime = performance.timing.connectEnd - (performance.timing.connectStart || 0),
        _responseTime = performance.timing.responseEnd - (performance.timing.responseStart || 0),
        _emptyScreenTime = performance.timing.responseStart - (performance.timing.navigationStart || 0),
        _parseDomTime = performance.timing.domContentLoadedEventEnd - (performance.timing.domLoading || 0),
        _domReadyTime = performance.timing.domContentLoadedEventEnd - (performance.timing.navigationStart || 0),
        _roundtripTime = (performance.timing.loadEventEnd || performance.timing.domComplete) - (performance.timing.navigationStart || 0);

    function getResults() {
        return {
            tp: 'timing',
            dtp: 'html',
            dt: Math.floor(_dnsTime),                       // DNS 时间
            tt: Math.floor(_tcpTime),                       // TCP 建立时间
            rt: Math.floor(_responseTime),                  // request 建立时间 // 下载时间
            domt: Math.floor(_parseDomTime),                // 解析 dom 树时间
            et: Math.floor(_emptyScreenTime),               // 白屏时间,用户可见, start render
            ot: Math.floor(_domReadyTime),                  // 用户可交互时间, start interact
            rtt: Math.floor(_roundtripTime),                // 总时间, start page load
            wd: screen.width || 1,                          // 屏幕宽
            hg: screen.height || 1,                         // 屏幕高
            pf: navigator.platform || 'unknown'             // 系统
        };
    }

    return {
        collect: function() {
            return getResults();
        },

        print: function() {
            var debug = document.getElementById("debug");
            var output = this.formatDebugInfo();
            if (!debug) {
                var divTag = document.createElement("div");
                divTag.id = "debug";
                divTag.innerHTML = output;
                document.body.appendChild(divTag);
            } else {
                debug.innerHTML += output;
            }
        },

        formatDebugInfo: function() {
            var debuginfo = "<p>";
            debuginfo += "timing object : " + JSON.stringify(this.collect(), null, 2) + "<br/>";

            debuginfo += "url: " + decodeURIComponent(window.location.href) + "<br/>";
            debuginfo += "</p>";
            return debuginfo
        }
    }
};

var reporter = {
    init: function(debug) {
        this.enable = true;
        this.debug = debug;

        if (!('performance' in window)) {
            this.enable = false;
            return;
        }
    },
    collect: function() {
        if (!this.enable) {
            return;
        }

        var perf = timingReporter();
        var data = perf.collect();

        if (this.debug) {
            perf.print();
        }

        return data;
    }
};

module.exports = reporter;