// ==UserScript==
// @name         网页电子教材自动来回滚动演示
// @namespace    http://tampermonkey.net/
// @version      1.4
// @description  【仅技术演示】网页长文本自动来回滚动，支持面板实时调速，不可用于网课刷时长
// @author       demo
// @match        *://*/*
// @grant        GM_addStyle
// ==/UserScript==
(function() {
    'use strict';

    GM_addStyle(`
        .book-auto-read-panel {
            position: fixed;
            top: 80px;
            right: 16px;
            background: rgba(0,0,0,0.7);
            color:#fff;
            padding:12px;
            border-radius:6px;
            z-index:99999;
        }
        .book-auto-read-panel button {
            padding: 6px 10px;
            margin:4px;
            border:none;
            border-radius:4px;
            cursor:pointer;
        }
        .book-auto-read-panel input {
            width:60px;
            padding:4px;
            margin:4px;
        }
    `);

    const cfg = {
        speed: 1.5,        // 默认滚动像素
        interval: 60,      // 滚动间隔ms
        bottomGap: 120,
        topGap: 20
    };
    let timer = null;
    let paused = false;
    let direction = 1; // 1向下，-1向上

    const panel = document.createElement('div');
    panel.className = "book-auto-read-panel";
    panel.innerHTML = `
        <div>来回滚动演示</div>
        <div>速度:<input id="speedInput" type="number" step="0.1" min="0.1" value="${cfg.speed}"></div>
        <button id="readStart">开始</button>
        <button id="readPause">暂停</button>
        <button id="readStop">停止</button>
    `;
    document.body.appendChild(panel);

    const speedInput = document.querySelector("#speedInput");

    // 获取真实滚动容器
    function getScrollContainer() {
        const html = document.documentElement;
        const body = document.body;
        if (html.scrollHeight > html.clientHeight) return html;
        if (body.scrollHeight > body.clientHeight) return body;
        const allDivs = document.querySelectorAll('div');
        for(let el of allDivs){
            if(el.scrollHeight > el.clientHeight && getComputedStyle(el).overflow !== 'hidden'){
                return el;
            }
        }
        return window;
    }

    function startScroll() {
        if(timer) return;
        paused = false;
        direction = 1;
        timer = setInterval(()=>{
            if(paused) return;
            // 实时读取输入框速度
            cfg.speed = parseFloat(speedInput.value) || 1.5;

            const scrollEl = getScrollContainer();
            let scrollTop, scrollH, viewH;
            if(scrollEl === window){
                scrollTop = window.scrollY;
                scrollH = document.documentElement.scrollHeight;
                viewH = window.innerHeight;
            }else{
                scrollTop = scrollEl.scrollTop;
                scrollH = scrollEl.scrollHeight;
                viewH = scrollEl.clientHeight;
            }

            // 触底切换向上
            if(direction === 1 && scrollTop + viewH >= scrollH - cfg.bottomGap){
                direction = -1;
            }
            // 触顶切换向下
            if(direction === -1 && scrollTop <= cfg.topGap){
                direction = 1;
            }

            const newScrollTop = scrollTop + cfg.speed * direction;
            if(scrollEl === window){
                window.scrollTo(0, newScrollTop);
            }else{
                scrollEl.scrollTop = newScrollTop;
            }
        }, cfg.interval);
    }
    function pauseScroll(){
        paused = !paused;
    }
    function stopScroll(){
        clearInterval(timer);
        timer = null;
    }

    document.querySelector("#readStart").onclick = startScroll;
    document.querySelector("#readPause").onclick = pauseScroll;
    document.querySelector("#readStop").onclick = stopScroll;

})();