// ==UserScript==
// @name         DeepSeek一键回顶
// @namespace    https://scriptcat.org/zh-CN/users/214553
// @version      1.3.0
// @description  在DeepSeek网页上添加「回到顶部」按钮，一键回到对话的最开始。
// @author       English3（Σπg|!εh๑๑๑）
// @license      MIT
// @icon         https://deepseek.com/favicon.ico
// @match        https://chat.deepseek.com/*
// @run-at       document-idle
// @grant        none
// ==/UserScript==

(() => {
  'use strict';
  const ID = 'ds-back-top-v5';

  const goTop = () => {
    try {
      let bestEl = null;
      let maxScroll = 0;
      
      // 精准查找聊天滚动容器，不再全页暴力遍历
      document.querySelectorAll('div, main').forEach(el => {
        const style = window.getComputedStyle(el);
        // 找出实际产生滚动且有高度的容器
        if ((style.overflowY === 'auto' || style.overflowY === 'scroll') && el.scrollHeight > maxScroll && el.clientHeight > 100) {
          maxScroll = el.scrollHeight;
          bestEl = el;
        }
      });

      if (bestEl) {
        bestEl.scrollTop = 0;
      } else {
        window.scrollTo(0, 0);
        document.documentElement.scrollTop = 0;
        document.body.scrollTop = 0;
      }
    } catch (e) {
      console.warn('回顶异常:', e);
    }
  };

  // 创建按钮
  const btn = document.createElement('button');
  btn.id = ID;
  btn.type = 'button';
  btn.title = '回到顶部';
  btn.setAttribute('aria-label', '回到顶部');
  btn.innerHTML = `<svg width="20" height="20" viewBox="0 0 24 24" fill="none"
    stroke="currentColor" stroke-width="2.5" stroke-linecap="round" stroke-linejoin="round">
    <path d="M12 19V5M5 12l7-7 7 7"/></svg>`;

  btn.onmouseenter = () => { if (btn.dataset.mode === 'pc') btn.style.opacity = '1'; };
  btn.onmouseleave = () => { if (btn.dataset.mode === 'pc') btn.style.opacity = '0.8'; };
  
  btn.addEventListener('click', (e) => {
    e.preventDefault();
    e.stopPropagation();
    goTop();
  });

  // 智能挂载与布局
  const isMobile = () => window.innerWidth <= 768;

  const insertToMobileHeader = () => {
    const allBtns = Array.from(document.querySelectorAll('button, [role="button"]'));
    const W = window.innerWidth;
    
    const topRightBtns = allBtns.filter(b => {
      const r = b.getBoundingClientRect();
      return r.top < 60 && r.left > W * 0.5 && r.width > 0 && b.id !== ID;
    }).sort((a, b) => a.getBoundingClientRect().left - b.getBoundingClientRect().left);

    if (topRightBtns.length > 0) {
      const shareBtn = topRightBtns[topRightBtns.length - 1];
      const parent = shareBtn.parentElement;
      
      if (parent && (btn.parentElement !== parent || btn.nextElementSibling !== shareBtn)) {
        parent.insertBefore(btn, shareBtn);
        btn.dataset.mode = 'mobile';
        
        // 手机端纯净无边框，只留箭头
        Object.assign(btn.style, {
          position: 'relative', right: 'auto', bottom: 'auto',
          width: '32px', height: '32px', 
          borderRadius: '0', background: 'none', border: 'none', outline: 'none',
          boxShadow: 'none', color: 'inherit',
          zIndex: 'auto', opacity: '1',
          margin: '0 4px', padding: '0', display: 'flex',
          alignItems: 'center', justifyContent: 'center', flexShrink: '0',
          transition: 'none' // 移除过渡，防止视觉残留
        });
        return true;
      }
    }
    return false;
  };

  const setPcFloatingStyle = () => {
    btn.dataset.mode = 'pc';
    Object.assign(btn.style, {
      position: 'fixed', right: '24px', bottom: '120px',
      width: '46px', height: '46px', borderRadius: '50%',
      background: 'rgba(0, 0, 0, 0.6)', color: '#ffffff',
      border: '2px solid rgba(255,255,255,0.2)',
      zIndex: '9999999', boxShadow: '0 4px 12px rgba(0,0,0,0.3)',
      opacity: '0.8', margin: '0', padding: '0',
      display: 'flex', alignItems: 'center', justifyContent: 'center',
      transition: 'opacity 0.15s ease, transform 0.15s ease', cursor: 'pointer'
    });
  };

  const ensureMount = () => {
    if (!document.body) return;

    if (isMobile()) {
      if (btn.dataset.mode === 'mobile' && btn.parentElement && btn.parentElement.tagName !== 'BODY') return;
      if (!insertToMobileHeader()) {
        if (!btn.isConnected) document.body.appendChild(btn);
        setPcFloatingStyle(); 
      }
    } 
    else {
      if (!btn.isConnected) document.body.appendChild(btn);
      if (btn.dataset.mode !== 'pc') {
        setPcFloatingStyle();
      }
    }
  };

  // 启动
  ensureMount();
  // 防丢失轮询，避免因React重绘导致按钮被吃
  setInterval(ensureMount, 1500); 
  setTimeout(ensureMount, 500);
  setTimeout(ensureMount, 2000);

})();