// ==UserScript==
// @name         连续下一页 - 优化版
// @namespace    https://scriptcat.org/zh-CN/scripts/create
// @version      1.1.0
// @description  智能预加载下一页，滚动到底部自动拼接，无感加载，右下角显示加载进度。
// @author       YZD
// @license      MIT
// @match        *://*/*
// @grant        GM_addStyle
// @run-at       document-end
// @icon         https://images.icon-icons.com/2063/PNG/512/download_down_arrow_browser_webpage_icon_124661.png
// ==/UserScript==

(function () {
  'use strict';

  // ─── 状态面板 ───────────────────────────────────────────────
  const panel = document.createElement('div');
  panel.id = 'np-panel';
  panel.innerHTML = `
    <div class="np-header">
      <span class="np-icon">⟲</span>
      <span class="np-title">连续下一页</span>
      <span class="np-toggle">▼</span>
    </div>
    <div class="np-content">
      <div class="np-page">第 1 页</div>
      <div class="np-status">等待滚动...</div>
    </div>
  `;
  document.body.appendChild(panel);

  GM_addStyle(`
    #np-panel {
      position: fixed;
      bottom: 12px;
      right: 12px;
      width: 180px;
      background: rgba(255,255,255,0.96);
      border-radius: 10px;
      box-shadow: 0 4px 18px rgba(0,0,0,0.18);
      font-family: "Segoe UI", system-ui, sans-serif;
      font-size: 12px;
      color: #333;
      z-index: 2147483647;
      user-select: none;
    }
    .np-header {
      display: flex;
      align-items: center;
      gap: 6px;
      padding: 7px 10px;
      background: linear-gradient(135deg,#667eea,#764ba2);
      color: #fff;
      border-radius: 10px 10px 0 0;
      cursor: move;
    }
    .np-title { flex: 1; font-size: 12px; font-weight: 600; }
    .np-toggle { cursor: pointer; font-size: 10px; padding: 2px 4px; }
    .np-content { padding: 8px 10px 10px; }
    .np-page {
      font-size: 11px;
      font-weight: bold;
      color: #667eea;
      margin-bottom: 4px;
      text-align: center;
    }
    .np-status {
      font-size: 11px;
      text-align: center;
      color: #555;
      line-height: 1.5;
    }
    .np-status.loading { color: #667eea; }
    .np-status.success { color: #2c9f67; }
    .np-status.error   { color: #e05f66; }
    .np-divider {
      border: none;
      border-top: 2px dashed #667eea44;
      margin: 16px 0 4px;
    }
    .np-page-label {
      text-align: center;
      font-size: 11px;
      color: #764ba2;
      font-weight: bold;
      margin: 4px 0 8px;
    }
  `);

  // ─── 折叠 ────────────────────────────────────────────────────
  const toggleBtn = panel.querySelector('.np-toggle');
  const content   = panel.querySelector('.np-content');
  let collapsed = false;
  toggleBtn.addEventListener('click', () => {
    collapsed = !collapsed;
    content.style.display = collapsed ? 'none' : 'block';
    toggleBtn.textContent  = collapsed ? '▲' : '▼';
  });

  // ─── 拖拽 ────────────────────────────────────────────────────
  const header = panel.querySelector('.np-header');
  header.addEventListener('mousedown', (e) => {
    const sx = e.clientX, sy = e.clientY;
    const sr = parseInt(getComputedStyle(panel).right,  10) || 12;
    const sb = parseInt(getComputedStyle(panel).bottom, 10) || 12;
    panel.style.cursor = 'grabbing';
    const move = (e) => {
      panel.style.right  = `${Math.max(0, sr + sx - e.clientX)}px`;
      panel.style.bottom = `${Math.max(0, sb - sy + e.clientY)}px`;
    };
    const up = () => {
      panel.style.cursor = 'default';
      document.removeEventListener('mousemove', move);
    };
    document.addEventListener('mousemove', move);
    document.addEventListener('mouseup', up, { once: true });
  });

  // ─── 工具函数 ─────────────────────────────────────────────────
  const statusEl = panel.querySelector('.np-status');
  const pageEl   = panel.querySelector('.np-page');
  let pageCount  = 1;

  function setStatus(text, cls = '') {
    statusEl.textContent = text;
    statusEl.className   = 'np-status ' + cls;
  }

  function setPage(n) {
    pageCount = n;
    pageEl.textContent = `第 ${n} 页`;
  }

  // ─── 下一页链接检测（多策略）────────────────────────────────
  const NEXT_SELECTORS = [
    'a[rel="next"]',
    'link[rel="next"]',
    '.next a', '.next-page a', '.pagination-next a',
    'a.next', 'a.next-page', 'a.nextpage',
    '[class*="next"] a',
    '[aria-label="Next page"]',
    '[aria-label="下一页"]',
    '[aria-label="next"]',
    'a[href*="page="]:last-of-type',
  ];

  const NEXT_TEXT = ['下一页','下一篇','下页','next','next page','»','›','>>'];

  function findNextLink() {
    // 1. 标准选择器
    for (const sel of NEXT_SELECTORS) {
      const el = document.querySelector(sel);
      if (el && el.href) return el.href;
    }

    // 2. 按文字内容匹配所有 <a>
    const anchors = Array.from(document.querySelectorAll('a[href]'));
    for (const a of anchors) {
      const txt = a.textContent.trim().toLowerCase();
      if (NEXT_TEXT.includes(txt) && a.href) return a.href;
    }

    // 3. 按当前 URL 自动推断页码
    return guessNextUrl();
  }

  function guessNextUrl() {
    const url = new URL(location.href);

    // ?page=N 或 ?p=N
    for (const key of ['page', 'p', 'paged', 'pg', 'pagenum', 'pageno']) {
      if (url.searchParams.has(key)) {
        const cur = parseInt(url.searchParams.get(key), 10);
        if (!isNaN(cur)) {
          url.searchParams.set(key, cur + 1);
          return url.toString();
        }
      }
    }

    // 路径中的 /page/N/ 或 /p/N/
    const pathMatch = url.pathname.match(/\/(page|p)\/(\d+)(\/?)$/i);
    if (pathMatch) {
      const next = parseInt(pathMatch[2], 10) + 1;
      url.pathname = url.pathname.replace(pathMatch[0], `/${pathMatch[1]}/${next}${pathMatch[3]}`);
      return url.toString();
    }

    // 路径末尾 -N 或 _N
    const numMatch = url.pathname.match(/[-_](\d+)(\.html?)?$/i);
    if (numMatch) {
      const next = parseInt(numMatch[1], 10) + 1;
      url.pathname = url.pathname.replace(numMatch[0], `-${next}${numMatch[2] || ''}`);
      return url.toString();
    }

    return null;
  }

  // ─── 内容容器检测 ─────────────────────────────────────────────
  const CONTENT_SELECTORS = [
    'article', 'main',
    '[role="main"]',
    '.post-content', '.article-content', '.entry-content',
    '.content', '#content', '#main', '.main',
    '.post', '.article',
  ];

  function findContainer(doc) {
    for (const sel of CONTENT_SELECTORS) {
      const el = doc.querySelector(sel);
      if (el) return el;
    }
    return doc.body;
  }

  // ─── 拼接逻辑 ─────────────────────────────────────────────────
  let currentNextUrl = null;
  let isFetching     = false;

  function fetchAndAppend(url) {
    if (isFetching) return;
    isFetching = true;
    setStatus('正在加载...', 'loading');

    fetch(url, { credentials: 'include' })
      .then((r) => {
        if (!r.ok) throw new Error(`HTTP ${r.status}`);
        return r.text();
      })
      .then((html) => {
        const doc       = new DOMParser().parseFromString(html, 'text/html');
        const srcEl     = findContainer(doc);
        const dstEl     = findContainer(document);

        // 添加分隔线 + 页码标签
        const hr = document.createElement('hr');
        hr.className = 'np-divider';
        const label = document.createElement('div');
        label.className = 'np-page-label';
        label.textContent = `—— 第 ${pageCount + 1} 页 ——`;
        dstEl.appendChild(hr);
        dstEl.appendChild(label);

        // 拼接内容
        Array.from(srcEl.childNodes).forEach((node) => {
          dstEl.appendChild(node.cloneNode(true));
        });

        setPage(pageCount + 1);
        setStatus('已拼接', 'success');

        // 更新下一页 URL（从新文档中重新查找）
        // 临时替换 document.querySelector 上下文
        const oldBody = document.body;
        const tmpDiv  = document.createElement('div');
        tmpDiv.innerHTML = doc.body.innerHTML;

        currentNextUrl = (() => {
          for (const sel of NEXT_SELECTORS) {
            const el = tmpDiv.querySelector(sel);
            if (el && el.href) return el.href;
          }
          const anchors = Array.from(tmpDiv.querySelectorAll('a[href]'));
          for (const a of anchors) {
            const txt = a.textContent.trim().toLowerCase();
            if (NEXT_TEXT.includes(txt) && a.href) return a.href;
          }
          return null;
        })();

        if (!currentNextUrl) {
          // 降级：继续用 URL 推断
          currentNextUrl = (() => {
            const u = new URL(url);
            for (const key of ['page','p','paged','pg','pagenum','pageno']) {
              if (u.searchParams.has(key)) {
                const cur = parseInt(u.searchParams.get(key), 10);
                if (!isNaN(cur)) { u.searchParams.set(key, cur + 1); return u.toString(); }
              }
            }
            return null;
          })();
        }

        if (!currentNextUrl) setStatus('已到最后一页', 'success');
      })
      .catch((err) => {
        setStatus('加载失败: ' + err.message, 'error');
      })
      .finally(() => {
        isFetching = false;
      });
  }

  // ─── 滚动监听 ─────────────────────────────────────────────────
  let scrollTimer = null;
  window.addEventListener('scroll', () => {
    clearTimeout(scrollTimer);
    scrollTimer = setTimeout(() => {
      const distToBottom = document.body.scrollHeight - window.innerHeight - window.scrollY;
      if (distToBottom > 300) return;

      const url = currentNextUrl || findNextLink();
      if (!url) {
        setStatus('未找到下一页', 'error');
        return;
      }
      if (url === location.href) {
        setStatus('已是最后一页', 'success');
        return;
      }
      currentNextUrl = url;
      fetchAndAppend(url);
    }, 200);
  });

})();