class ListenDomChange {
    //   监听 dom 节点
    dom = null;
    // observer
    observer = null;
    // performance
    performanceConfig = {};

    constructor(dom, callbackDomChange) {
        this.dom = dom;
        this.callbackDomChange = callbackDomChange;
        // 初始化为{}
        this.performanceConfig={}
        // 计算performanceConfig
        this.calcPerformance()
    }
    // 监听 dom变化
    mutationListen() {
        // 选择需要观察变动的节点
        const targetNode = this.dom

        // 观察器的配置（需要观察什么变动）
        const config = { attributes: true, childList: true, subtree: true };

        // 当观察到变动时执行的回调函数
        const callback = function (mutationsList, observer) {
            // Use traditional 'for loops' for IE 11
            for (let mutation of mutationsList) {
                if (mutation.type === "childList") {
                    console.log("A child node has been added or removed.");
                } else if (mutation.type === "attributes") {
                    console.log("The " + mutation.attributeName + " attribute was modified.");
                }
            }
            console.log('change', change)
        };

        // 创建一个观察器实例并传入回调函数
        this.observer = new MutationObserver(callback);

        // 以上述配置开始观察目标节点
        this.observer.observer.observe(targetNode, config);

        // 之后，可停止观察
        this.observer.observer.disconnect();
    }

    getPerformance(){
        return performance
    }

    setPerformance(key,value){
        this.calcPerformance[key]=value
    }

    calcPerformance() {
        // Time to when activation occurred
        let activationStart =
            performance.getEntriesByType("navigation")[0].activationStart;

        // Time to first paint
        let firstPaint = performance.getEntriesByName("first-paint")[0].startTime;

        // Time to first contentful paint
        let firstContentfulPaint = performance.getEntriesByName(
            "first-contentful-paint",
        )[0].startTime;

        console.log("time to first paint: " + (firstPaint - activationStart));
        console.log(
            "time to first-contentful-paint: " + (firstContentfulPaint - activationStart),
        );
        setPerformance('time to first paint',firstPaint - activationStart)
        setPerformance('time to first-contentful-paint',firstContentfulPaint - activationStart)

        const entries = performance.getEntriesByType("navigation");
        entries.forEach((entry) => {
            console.log(`${entry.name}: domComplete time: ${entry.domComplete}ms`);

            const domContentLoadedTime =
                entry.domContentLoadedEventEnd - entry.domContentLoadedEventStart;
            console.log(
                `${entry.name}: DOMContentLoaded processing time: ${domContentLoadedTime}ms`,
            );
            setPerformance(entry.name,domContentLoadedTime)
        });
    }
}

export {
    ListenDomChange
}