// ==UserScript==
// @name         DeepSeek一键回顶
// @namespace    https://scriptcat.org/zh-CN/users/214553
// @version      1.0.0
// @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';

      // 回顶：找到滚得最多的元素，直接归零
        const goTop = () => {
            let best = null, max = 0;
                for (const el of document.querySelectorAll('*')) {
                      if (el.scrollTop > max) { max = el.scrollTop; best = el; }
                          }
                              if (best) best.scrollTop = 0;
                                  try {
                                        document.documentElement.scrollTop = 0;
                                              document.body.scrollTop = 0;
                                                    window.scrollTo(0, 0);
                                                        } catch (_) {}
                                                          };

                                                            // 按钮创建
                                                              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="2.2" stroke-linecap="round" stroke-linejoin="round">
                                                                                <path d="M12 19V5M5 12l7-7 7 7"/></svg>`;
                                                                                  Object.assign(btn.style, {
                                                                                      background: 'transparent', border: 'none', borderRadius: '8px',
                                                                                          width: '32px', height: '32px', padding: '0', margin: '0 2px',
                                                                                              display: 'flex', alignItems: 'center', justifyContent: 'center',
                                                                                                  cursor: 'pointer', color: 'inherit', opacity: '0.7', flexShrink: '0',
                                                                                                      transition: 'opacity .15s, background .15s',
                                                                                                        });
                                                                                                          btn.onmouseenter = () => { btn.style.opacity = '1'; btn.style.background = 'rgba(128,128,128,0.15)'; };
                                                                                                            btn.onmouseleave = () => { btn.style.opacity = '0.7'; btn.style.background = 'transparent'; };
                                                                                                              btn.addEventListener('click', (e) => {
                                                                                                                  e.preventDefault();
                                                                                                                      e.stopPropagation();
                                                                                                                          goTop();
                                                                                                                            });

                                                                                                                              // 寻找顶部标题栏
                                                                                                                                const findHeader = () => {
                                                                                                                                    const W = window.innerWidth;
                                                                                                                                        const list = [];
                                                                                                                                            for (const el of document.querySelectorAll('div, header, nav, section')) {
                                                                                                                                                  const r = el.getBoundingClientRect();
                                                                                                                                                        if (r.top > 30 || r.height > 90 || r.height < 24) continue;
                                                                                                                                                              if (r.width < W * 0.6) continue;
                                                                                                                                                                    const rightBtns = [...el.querySelectorAll('button, [role="button"]')]
                                                                                                                                                                            .filter(b => {
                                                                                                                                                                                      const br = b.getBoundingClientRect();
                                                                                                                                                                                                return br.left > W * 0.5 && br.width > 0 && br.height > 0;
                                                                                                                                                                                                        });
                                                                                                                                                                                                              if (rightBtns.length >= 2) list.push({ el, n: rightBtns.length });
                                                                                                                                                                                                                  }
                                                                                                                                                                                                                      list.sort((a, b) => b.n - a.n);
                                                                                                                                                                                                                          return list[0]?.el || null;
                                                                                                                                                                                                                            };

                                                                                                                                                                                                                              // 插入按钮（修复：只在位置不对时才插入）
                                                                                                                                                                                                                                const insertIntoHeader = (header) => {
                                                                                                                                                                                                                                    const W = window.innerWidth;
                                                                                                                                                                                                                                        const rightBtns = [...header.querySelectorAll('button, [role="button"]')]
                                                                                                                                                                                                                                              .filter(b => {
                                                                                                                                                                                                                                                      const r = b.getBoundingClientRect();
                                                                                                                                                                                                                                                              return r.left > W * 0.5 && r.width > 0 && r.height > 0 && b.id !== ID;
                                                                                                                                                                                                                                                                    })
                                                                                                                                                                                                                                                                          .sort((a, b) => a.getBoundingClientRect().left - b.getBoundingClientRect().left);

                                                                                                                                                                                                                                                                              if (!rightBtns.length) return false;
                                                                                                                                                                                                                                                                                  const first = rightBtns[0];
                                                                                                                                                                                                                                                                                      const parent = first.parentElement;
                                                                                                                                                                                                                                                                                          if (!parent) return false;

                                                                                                                                                                                                                                                                                              // 【核心修复点】：如果已经在目标位置，绝不重复调用 insertBefore，防止引发重绘和闪烁
                                                                                                                                                                                                                                                                                                  if (btn.parentElement !== parent || btn.nextElementSibling !== first) {
                                                                                                                                                                                                                                                                                                        parent.insertBefore(btn, first);
                                                                                                                                                                                                                                                                                                            }
                                                                                                                                                                                                                                                                                                                return true;
                                                                                                                                                                                                                                                                                                                  };

                                                                                                                                                                                                                                                                                                                    // 状态管理
                                                                                                                                                                                                                                                                                                                      let isFloating = false; // 记录当前是否处于浮动兜底状态

                                                                                                                                                                                                                                                                                                                        // 主循环
                                                                                                                                                                                                                                                                                                                          const ensure = () => {
                                                                                                                                                                                                                                                                                                                              const header = findHeader();
                                                                                                                                                                                                                                                                                                                                  
                                                                                                                                                                                                                                                                                                                                      // 尝试插入顶部栏
                                                                                                                                                                                                                                                                                                                                          if (header && insertIntoHeader(header)) {
                                                                                                                                                                                                                                                                                                                                                // 从浮动状态切换到标题栏，重置样式（只执行一次）
                                                                                                                                                                                                                                                                                                                                                      if (isFloating) {
                                                                                                                                                                                                                                                                                                                                                              isFloating = false;
                                                                                                                                                                                                                                                                                                                                                                      Object.assign(btn.style, {
                                                                                                                                                                                                                                                                                                                                                                                position: '', right: '', bottom: '', width: '32px', height: '32px',
                                                                                                                                                                                                                                                                                                                                                                                          borderRadius: '8px', background: 'transparent', color: 'inherit',
                                                                                                                                                                                                                                                                                                                                                                                                    zIndex: '', boxShadow: ''
                                                                                                                                                                                                                                                                                                                                                                                                            });
                                                                                                                                                                                                                                                                                                                                                                                                                  }
                                                                                                                                                                                                                                                                                                                                                                                                                        return; // 成功放入顶部栏，结束本次循环
                                                                                                                                                                                                                                                                                                                                                                                                                            }

                                                                                                                                                                                                                                                                                                                                                                                                                                // 兜底浮动逻辑（找不到标题栏时）
                                                                                                                                                                                                                                                                                                                                                                                                                                    if (!isFloating) {
                                                                                                                                                                                                                                                                                                                                                                                                                                          isFloating = true;
                                                                                                                                                                                                                                                                                                                                                                                                                                                Object.assign(btn.style, {
                                                                                                                                                                                                                                                                                                                                                                                                                                                        position: 'fixed', right: '20px', bottom: '170px',
                                                                                                                                                                                                                                                                                                                                                                                                                                                                width: '42px', height: '42px', borderRadius: '50%',
                                                                                                                                                                                                                                                                                                                                                                                                                                                                        background: 'rgba(0,0,0,0.55)', color: '#fff',
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                zIndex: '2147483647',
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        boxShadow: '0 2px 10px rgba(0,0,0,0.3)',
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              });
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  }
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      // 如果被React移出了DOM，重新挂载到body
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          if (!btn.isConnected) {
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                document.body.appendChild(btn);
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    }
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      };

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        // 降低频率，减少性能消耗。700ms可以放宽到1000ms，因为加入了防抖判断
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          setInterval(ensure, 1000);
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            ensure();
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              setTimeout(ensure, 200);
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                setTimeout(ensure, 1000);
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                })();