// ==UserScript==
// @name         手机可拖动折叠回到顶部｜修复版
// @namespace    http://tampermonkey.net/
// @version      2.0
// @description  可拖动、默认折叠、记忆位置状态、修复坐标BUG、防误触
// @match        *://*/*
// @grant        none
// @run-at       document-end
// @downloadURL https://update.greasyfork.icu/scripts/575535/%E6%89%8B%E6%9C%BA%E5%8F%AF%E6%8B%96%E5%8A%A8%E6%8A%98%E5%8F%A0%E5%9B%9E%E5%88%B0%E9%A1%B6%E9%83%A8%EF%BD%9C%E4%BF%AE%E5%A4%8D%E7%89%88.user.js
// @updateURL https://update.greasyfork.icu/scripts/575535/%E6%89%8B%E6%9C%BA%E5%8F%AF%E6%8B%96%E5%8A%A8%E6%8A%98%E5%8F%A0%E5%9B%9E%E5%88%B0%E9%A1%B6%E9%83%A8%EF%BD%9C%E4%BF%AE%E5%A4%8D%E7%89%88.meta.js
// ==/UserScript==
(function() {
    'use strict';

    const STORAGE_KEY = "back_top_float_data";
    // 防重复注入
    if (document.querySelector("#dragFloatWrap")) return;

    // ===== 修复1：增加JSON解析容错 try/catch =====
    let saveData;
    try {
        const local = localStorage.getItem(STORAGE_KEY);
        saveData = local ? JSON.parse(local) : null;
    } catch (e) {
        saveData = null;
    }

    // 默认配置
    const defaultData = {
        right: 16,
        bottom: 100,
        isFold: true
    };
    saveData = Object.assign({}, defaultData, saveData);

    // 外层容器
    const wrap = document.createElement("div");
    wrap.id = "dragFloatWrap";
    wrap.style.cssText = `
        position: fixed;
        right: ${saveData.right}px;
        bottom: ${saveData.bottom}px;
        z-index: 999999;
        user-select: none;
        touch-action: none;
        box-sizing: border-box;
    `;

    // 折叠开关按钮
    const foldBtn = document.createElement("div");
    foldBtn.style.cssText = `
        width: 40px;
        height: 40px;
        line-height: 40px;
        text-align: center;
        background: #1677ff;
        color: #fff;
        border-radius: 50%;
        font-size: 18px;
        box-shadow: 0 2px 8px rgba(0,0,0,0.2);
        box-sizing: border-box;
    `;

    // 功能区容器
    const contentBox = document.createElement("div");
    contentBox.style.cssText = `
        position: absolute;
        bottom: 50px;
        right: 0;
        display: none;
        box-sizing: border-box;
    `;

    // 回到顶部按钮
    const topBtn = document.createElement("div");
    topBtn.style.cssText = `
        width: 46px;
        height: 46px;
        line-height: 46px;
        text-align: center;
        background: #22c55e;
        color: #fff;
        border-radius: 50%;
        font-size: 20px;
        margin-bottom: 8px;
        box-shadow: 0 2px 8px rgba(0,0,0,0.2);
        box-sizing: border-box;
    `;
    topBtn.innerText = "↑";

    // 结构挂载
    contentBox.appendChild(topBtn);
    wrap.appendChild(contentBox);
    wrap.appendChild(foldBtn);
    document.body.appendChild(wrap);

    // 初始化折叠状态
    function initFoldState() {
        if (saveData.isFold) {
            contentBox.style.display = "none";
            foldBtn.innerText = "☰";
        } else {
            contentBox.style.display = "block";
            foldBtn.innerText = "✕";
        }
    }
    initFoldState();

    // 折叠切换 + 保存状态
    foldBtn.addEventListener("click", (e) => {
        e.stopPropagation();
        saveData.isFold = !saveData.isFold;
        initFoldState();
        localStorage.setItem(STORAGE_KEY, JSON.stringify(saveData));
    });

    // 回到顶部
    topBtn.addEventListener("click", (e) => {
        e.stopPropagation();
        window.scrollTo({
            top: 0,
            behavior: "smooth"
        });
    });

    // ===== 修复2：标准坐标 + 拖动阈值防误触 =====
    let isDrag = false;
    let startX = 0, startY = 0;
    let initRight = 0, initBottom = 0;
    const MOVE_THRESHOLD = 8; // 移动阈值，小于则判定为点击

    wrap.addEventListener("touchstart", (e) => {
        const rect = wrap.getBoundingClientRect();
        startX = e.touches[0].clientX;
        startY = e.touches[0].clientY;
        initRight = rect.right;
        initBottom = document.documentElement.clientHeight - rect.bottom;
        isDrag = false;
    });

    wrap.addEventListener("touchmove", (e) => {
        const dx = startX - e.touches[0].clientX;
        const dy = startY - e.touches[0].clientY;
        // 超过阈值判定为拖动
        if (Math.abs(dx) > MOVE_THRESHOLD || Math.abs(dy) > MOVE_THRESHOLD) {
            isDrag = true;
        }
        wrap.style.right = `${initRight + dx}px`;
        wrap.style.bottom = `${initBottom - dy}px`;
    });

    wrap.addEventListener("touchend", () => {
        // 拖动结束才保存位置
        if (isDrag) {
            const rect = wrap.getBoundingClientRect();
            saveData.right = document.documentElement.clientWidth - rect.right;
            saveData.bottom = document.documentElement.clientHeight - rect.bottom;
            localStorage.setItem(STORAGE_KEY, JSON.stringify(saveData));
        }
        isDrag = false;
    });
})();