// ==UserScript==
// @name         国家智慧教育平台自动连播工具
// @namespace    local.smartedu.video.fast
// @version      2.3.0
// @description  静音正常速度播放、后台恢复，并在视频结束后自动切换下一课
// @match        *://smartedu.cn/*
// @match        *://*.smartedu.cn/*
// @run-at       document-start
// @grant        none
// ==/UserScript==

(function () {
  'use strict';

  const SCAN_INTERVAL_MS = 1000;
  const BACKGROUND_CHECK_INTERVAL_MS = 300;
  const NEXT_LESSON_DELAY_MS = 1200;
  const videoStates = new WeakMap();
  let currentLessonLabel = '';
  let advancing = false;

  function getVideos() {
    return Array.from(document.querySelectorAll('video'));
  }

  function muteVideo(video) {
    video.muted = true;
    video.volume = 0;
  }

  function playVideo(video) {
    muteVideo(video);
    video.autoplay = true;
    video.playsInline = true;
    const playPromise = video.play();
    if (playPromise && typeof playPromise.catch === 'function') {
      playPromise.catch(() => {
        // Some browsers still require one click on the page before autoplay.
      });
    }
  }

  function isPageInBackground() {
    return document.hidden || !document.hasFocus();
  }

  function resumeBackgroundVideo(video) {
    if (!isPageInBackground() || video.ended || video.readyState === HTMLMediaElement.HAVE_NOTHING) return;
    playVideo(video);
  }

  function resumeBackgroundPlayback() {
    if (!isPageInBackground()) return;
    getVideos().forEach((video) => {
      prepareVideo(video);
      if (video.paused && !video.ended) resumeBackgroundVideo(video);
    });
  }

  function scheduleBackgroundResume() {
    window.setTimeout(resumeBackgroundPlayback, 0);
    window.setTimeout(resumeBackgroundPlayback, 250);
    window.setTimeout(resumeBackgroundPlayback, 1000);
  }

  function normalizeText(element) {
    return (element.innerText || element.textContent || '').replace(/\s+/g, ' ').trim();
  }

  function getLessonLabel(element) {
    const text = normalizeText(element);
    return text.length >= 2 && text.length <= 100 ? text : '';
  }

  function getLessonRows() {
    const candidates = Array.from(document.querySelectorAll(
      '[role="treeitem"], [role="option"], li, a, button, [class*="item"], [class*="lesson"], [class*="resource"]'
    ));
    const byLabel = new Map();

    candidates.forEach((element) => {
      const label = getLessonLabel(element);
      const rect = element.getBoundingClientRect();
      if (!label || rect.width < 60 || rect.height < 18) return;
      if (rect.height > 120 || getComputedStyle(element).visibility === 'hidden') return;
      // The course catalog is the right-hand column. This excludes the top navigation.
      if (rect.left < window.innerWidth * 0.45) return;

      const existing = byLabel.get(label);
      if (!existing || rect.width * rect.height > existing.area) {
        byLabel.set(label, { element, area: rect.width * rect.height });
      }
    });

    return Array.from(byLabel.entries()).map(([label, value]) => ({
      label,
      element: value.element,
    }));
  }

  function hasSelectedState(element) {
    let node = element;
    for (let level = 0; node && level < 5; level += 1, node = node.parentElement) {
      if (node.getAttribute('aria-current') === 'true' || node.getAttribute('aria-selected') === 'true') {
        return true;
      }

      const className = typeof node.className === 'string' ? node.className : '';
      if (/(^|[-_\s])(active|current|playing|selected)(?=$|[-_\s])/.test(className)) {
        return true;
      }

      if (node !== element && node.getBoundingClientRect().height > 120) break;
    }
    return false;
  }

  function looksHighlighted(element) {
    const nodes = [element, ...Array.from(element.querySelectorAll('*')).slice(0, 12)];
    return nodes.some((node) => {
      const color = getComputedStyle(node).color.match(/\d+/g);
      if (!color || color.length < 3) return false;
      const [red, green, blue] = color.map(Number);
      return blue > red + 25 && blue > green + 15;
    });
  }

  function rememberClickedLesson(event) {
    let node = event.target;
    for (let level = 0; node && level < 7; level += 1, node = node.parentElement) {
      const label = getLessonLabel(node);
      const rect = node.getBoundingClientRect();
      if (label && rect.height >= 18 && rect.height <= 120 && rect.left >= window.innerWidth * 0.45) {
        currentLessonLabel = label;
        return;
      }
    }
  }

  function rememberCurrentLesson() {
    const rows = getLessonRows();
    const selected = rows.find((row) => hasSelectedState(row.element))
      || rows.find((row) => looksHighlighted(row.element));
    if (selected) currentLessonLabel = selected.label;
  }

  function advanceToNextLesson() {
    if (advancing) return;
    advancing = true;
    rememberCurrentLesson();

    window.setTimeout(() => {
      const rows = getLessonRows();
      let currentIndex = rows.findIndex((row) => row.label === currentLessonLabel);
      if (currentIndex < 0) {
        currentIndex = rows.findIndex((row) => hasSelectedState(row.element));
      }

      const next = rows[currentIndex + 1];
      if (!next || currentIndex < 0) {
        setStatus(currentIndex >= 0 ? '已是最后一课' : '未识别当前课节');
        advancing = false;
        return;
      }

      currentLessonLabel = next.label;
      setStatus(`切换：${next.label}`);
      next.element.scrollIntoView({ block: 'nearest' });
      next.element.click();

      window.setTimeout(() => {
        advancing = false;
        playAll();
      }, NEXT_LESSON_DELAY_MS);
    }, NEXT_LESSON_DELAY_MS);
  }

  function prepareVideo(video) {
    if (videoStates.has(video)) return;

    const state = {
      volumeHandler: () => muteVideo(video),
      pauseHandler: () => {
        if (isPageInBackground() && !video.ended) scheduleBackgroundResume();
      },
      readyHandler: () => {
        if (!video.ended) playVideo(video);
      },
      endedHandler: () => advanceToNextLesson(),
    };

    videoStates.set(video, state);
    video.addEventListener('volumechange', state.volumeHandler);
    video.addEventListener('pause', state.pauseHandler);
    video.addEventListener('loadedmetadata', state.readyHandler);
    video.addEventListener('canplay', state.readyHandler);
    video.addEventListener('ended', state.endedHandler);
    playVideo(video);
  }

  function playAll() {
    const videos = getVideos();
    videos.forEach((video) => {
      prepareVideo(video);
      playVideo(video);
    });
    setStatus(videos.length ? '正在自动连播' : '未找到视频');
  }

  function setStatus(text) {
    const status = document.getElementById('smartedu-fast-status');
    if (status) status.textContent = text;
  }

  function createPanel() {
    if (window.top !== window.self || document.getElementById('smartedu-fast-panel')) return;

    const panel = document.createElement('div');
    panel.id = 'smartedu-fast-panel';
    panel.innerHTML = `
      <button type="button" data-action="play" title="播放当前视频">▶</button>
      <span id="smartedu-fast-status">静音自动连播</span>
    `;

    const style = document.createElement('style');
    style.textContent = `
      #smartedu-fast-panel {
        position: fixed;
        right: 18px;
        bottom: 90px;
        z-index: 2147483647;
        display: flex;
        align-items: center;
        gap: 6px;
        padding: 7px;
        color: #202124;
        background: rgba(255, 255, 255, 0.96);
        border: 1px solid #d6d9df;
        border-radius: 6px;
        box-shadow: 0 3px 12px rgba(0, 0, 0, 0.16);
        font: 13px/1.2 system-ui, sans-serif;
      }
      #smartedu-fast-panel button {
        width: 38px;
        height: 32px;
        padding: 0;
        color: #fff;
        background: #2468df;
        border: 0;
        border-radius: 4px;
        cursor: pointer;
        font: 600 14px/32px system-ui, sans-serif;
      }
      #smartedu-fast-panel button:hover { background: #1855bd; }
      #smartedu-fast-status { min-width: 76px; white-space: nowrap; }
    `;

    panel.addEventListener('click', (event) => {
      const button = event.target.closest('button[data-action]');
      if (!button) return;
      if (button.dataset.action === 'play') playAll();
    });

    document.documentElement.append(style, panel);
  }

  function scan() {
    getVideos().forEach(prepareVideo);
    resumeBackgroundPlayback();
    rememberCurrentLesson();
    const count = getVideos().length;
    if (count) setStatus(`${count} 个视频 · 静音自动连播`);
  }

  function observeNewVideos() {
    const observer = new MutationObserver((records) => {
      records.forEach((record) => {
        record.addedNodes.forEach((node) => {
          if (!(node instanceof Element)) return;
          if (node.matches('video')) prepareVideo(node);
          node.querySelectorAll?.('video').forEach(prepareVideo);
        });
      });
    });

    observer.observe(document.documentElement, { childList: true, subtree: true });
  }

  function start() {
    createPanel();
    document.addEventListener('click', rememberClickedLesson, true);
    document.addEventListener('visibilitychange', scheduleBackgroundResume, true);
    window.addEventListener('blur', scheduleBackgroundResume, true);
    window.addEventListener('focus', playAll, true);
    window.addEventListener('pageshow', playAll, true);
    observeNewVideos();
    scan();
    setInterval(scan, SCAN_INTERVAL_MS);
    setInterval(resumeBackgroundPlayback, BACKGROUND_CHECK_INTERVAL_MS);
  }

  if (document.readyState === 'loading') {
    document.addEventListener('DOMContentLoaded', start, { once: true });
  } else {
    start();
  }
})();