// ==UserScript==
// @name         autoScroll
// @namespace    eyes
// @version      0.2
// @description  It allows the page to scroll on its own
// @author       eyes
// @match        *://*/*
// @grant        none
// @downloadURL none
// ==/UserScript==

(function() {
    'use strict';
        var speed = 0;
        // 获取滑动位置
        function getScrollTop() {
            var scrollTop = 0,
                bodyScrollTop = 0,
                documentScrollTop = 0;
            if (document.body) {
                bodyScrollTop = document.body.scrollTop;
            }
            if (document.documentElement) {
                documentScrollTop = document.documentElement.scrollTop;
            }
            scrollTop = (bodyScrollTop - documentScrollTop > 0) ? bodyScrollTop : documentScrollTop;
            return scrollTop;
        }

        //浏览器视口的高度
        function getWindowHeight() {
            var windowHeight = 0;
            if (document.compatMode == 'CSS1Compat') {
                windowHeight = document.documentElement.clientHeight;
            } else {
                windowHeight = document.body.clientHeight;
            }
            return windowHeight;
        }

        //文档的总高度
        function getScrollHeight() {
            var scrollHeight = 0,
                bodyScrollHeight = 0,
                documentScrollHeight = 0;
            if (document.body) {
                bodyScrollHeight = document.body.scrollHeight;
            }
            if (document.documentElement) {
                documentScrollHeight = document.documentElement.scrollHeight;
            }
            scrollHeight = (bodyScrollHeight - documentScrollHeight > 0) ? bodyScrollHeight : documentScrollHeight;
            return scrollHeight;
        }

        // 滚动事件
        setInterval(() => {
            // 判断页面是否滑到底部
            let bottomFlag = (getScrollTop() + getWindowHeight() == getScrollHeight()) ? true : false;
            let topFlag = (getScrollTop() == 0) ? true : false;
            if (bottomFlag || topFlag) {
                speed = 0;
            } else {
                document.documentElement.scrollTop += speed;
            }
        }, 5)

        // 判断是否需要滚动
        document.onkeydown = (e) => {
            e = event || window.event;
            if (e && e.keyCode == 38 && e.altKey) { // 上键
                let bottomFlag = (getScrollTop() + getWindowHeight() == getScrollHeight()) ? true : false;
                if (bottomFlag) {
                    document.documentElement.scrollTop += -1;
                }
                speed -= 1.5;
            }
            if (e && e.keyCode == 40 && e.altKey) { // 下键
                let topFlag = (getScrollTop() == 0) ? true : false;
                if (topFlag) {
                    document.documentElement.scrollTop += 1;
                    console.log('123');
                }
                speed += 1.5;
            }
        }

        // 单击页面停止滚动
        document.onclick = () => {
            speed = 0;
        }

        // 滑动滚轮页面停止滚动
        document.onmousewheel = () => {
            speed = 0;
        }
        document.addEventListener("DOMMouseScroll", () => {
            speed = 0;
        })
})();