// ==UserScript==
// @name         页面导航
// @namespace    http://tampermonkey.net/
// @version      1.0.0
// @description  在右下角增添可以置顶或置底的按钮，长按可拖动
// @author       G31415
// @match        *://*/*
// @grant        none
// @license MIT
// @downloadURL https://update.greasyfork.icu/scripts/566182/%E9%A1%B5%E9%9D%A2%E5%AF%BC%E8%88%AA.user.js
// @updateURL https://update.greasyfork.icu/scripts/566182/%E9%A1%B5%E9%9D%A2%E5%AF%BC%E8%88%AA.meta.js
// ==/UserScript==

(function() {
    const id = 'g' + Math.random().toString(36).slice(2,7);
    const btn = Object.assign(document.createElement('button'), {
        id,
        textContent: '▼',
        title: '点击跳转'
    });
    
    // 状态变量
    let isDragging = false, dragActive = false, pressTimer = null;
    let startX, startY, startRight, startBottom;
    let lastY = window.scrollY;

    const style = document.createElement('style');
    style.textContent = `
        #${id} {
            all: initial;
            position: fixed;
            bottom: 0;
            right: 0;
            width: 32px;
            height: 32px;
            font: 16px/32px sans-serif;
            text-align: center;
            color: #000;
            background: transparent;
            border: none;
            cursor: pointer;
            z-index: 9999;
            user-select: none;
            -webkit-tap-highlight-color: transparent;
            outline: none; /* 取消蓝色方框 */
            display: none;
            touch-action: none; /* 核心：防止移动端手势干扰拖拽 */
        }
        #${id}.visible { display: block; }
        #${id}:hover { transform: scale(1); }
        #${id}:active { transform: scale(0.82); }
        #${id}.dragging {
            opacity: 0.6;
            cursor: grabbing;
            transform: scale(1);
            transition: none;
        }
        @media (max-width: 768px) {
            #${id} { width: 44px; height: 44px; font-size: 26px; line-height: 44px; }
        }
    `;
    
    document.head.appendChild(style);
    document.body.appendChild(btn);

    // 拖拽逻辑更新为 Pointer 事件（支持鼠标和触摸）
    const handlePointerMove = (e) => {
        if (!dragActive) return;
        
        const deltaX = e.clientX - startX;
        const deltaY = e.clientY - startY;
        
        // 计算新位置并限制在视口内
        let newRight = Math.max(0, Math.min(window.innerWidth - btn.offsetWidth, startRight - deltaX));
        let newBottom = Math.max(0, Math.min(window.innerHeight - btn.offsetHeight, startBottom - deltaY));
        
        btn.style.right = newRight + 'px';
        btn.style.bottom = newBottom + 'px';
    };

    btn.onpointerdown = (e) => {
        if (e.button !== 0 && e.pointerType === 'mouse') return;
        
        pressTimer = setTimeout(() => {
            dragActive = isDragging = true;
            btn.classList.add('dragging');
            // 锁定指针，拖拽更稳
            btn.setPointerCapture(e.pointerId);
            
            startX = e.clientX;
            startY = e.clientY;
            const s = getComputedStyle(btn);
            startRight = parseFloat(s.right) || 0;
            startBottom = parseFloat(s.bottom) || 0;
        }, 500);
    };

    btn.onpointerup = (e) => {
        clearTimeout(pressTimer);
        if (dragActive) {
            dragActive = isDragging = false;
            btn.classList.remove('dragging');
            btn.releasePointerCapture(e.pointerId);
        } else if (pressTimer && btn.classList.contains('visible')) {
            // 短按触发跳转
            const isToTop = btn.textContent === '▲';
            window.scrollTo(0, isToTop ? 0 : document.documentElement.scrollHeight);
        }
        pressTimer = null;
    };

    // 全局移动监听
    window.addEventListener('pointermove', handlePointerMove);

    // 滚动监听（增加性能节流）
    let ticking = false;
    window.addEventListener('scroll', () => {
        if (!ticking) {
            window.requestAnimationFrame(() => {
                const y = window.scrollY;
                if (y > 0) btn.classList.add('visible');
                
                if (btn.classList.contains('visible') && Math.abs(y - lastY) > 5) {
                    const isDown = y > lastY;
                    btn.textContent = isDown ? '▼' : '▲';
                    btn.title = isDown ? '点击跳转到底部' : '点击跳转到顶部';
                }
                lastY = y;
                ticking = false;
            });
            ticking = true;
        }
    }, { passive: true });

    // 守护按钮不被意外删除
    new MutationObserver(muts => muts.forEach(m => 
        m.removedNodes.forEach(n => n.id === id && document.body.appendChild(btn))
    )).observe(document.body, { childList: true });

})();