// ==UserScript==
// @name         抖音直播/视频 后台防暂停（脚本猫版）
// @namespace    com.workbuddy.douyin.keepplaying
// @version      1.0.1
// @description  网页版抖音直播页后台防暂停：切后台/最小化时保持直播播放不被自动暂停。仅在 live.douyin.com 与 www.douyin.com/follow/live 生效。右下角浮标显示状态，扩展菜单可一键开关。
// @author       WorkBuddy
// @match        *://live.douyin.com/*
// @match        *://www.douyin.com/follow/live*
// @grant        GM_registerMenuCommand
// @grant        GM_getValue
// @grant        GM_setValue
// @run-at       document-start
// ==/UserScript==

(function () {
  'use strict';

  var STORAGE_KEY = 'kj_keep_enabled';
  var USER_CLICK_COOLDOWN = 3000; // 用户交互后 3 秒内不自动恢复

  // ===== 开关状态 =====
  var enabledRef = true;
  function getEnabled() { return GM_getValue(STORAGE_KEY, true) !== false; }
  function setEnabled(v) {
    enabledRef = !!v;
    GM_setValue(STORAGE_KEY, enabledRef);
    updateIndicator();
  }

  // ===== 右下角浮标：让你一眼看出是否在运行 =====
  var indicator = null;
  function ensureIndicator() {
    if (indicator) return;
    indicator = document.createElement('div');
    indicator.setAttribute('style',
      'position:fixed;left:12px;bottom:12px;z-index:2147483647;' +
      'background:rgba(254,44,85,0.55);color:#fff;font:12px/1.4 sans-serif;' +
      'padding:6px 10px;border-radius:8px;box-shadow:0 2px 8px rgba(0,0,0,.3);' +
      'user-select:none;cursor:pointer;');
    (document.body || document.documentElement).appendChild(indicator);
    indicator.title = '点击切换 防暂停 开关';
    indicator.addEventListener('click', function () {
      setEnabled(!getEnabled());
    });
    updateIndicator();
  }
  function isFullscreen() {
    return !!(document.fullscreenElement || document.webkitFullscreenElement || document.msFullscreenElement);
  }
  function updateIndicator() {
    if (!indicator) return;
    // 全屏时隐藏，避免遮挡画面
    if (isFullscreen()) {
      indicator.style.display = 'none';
      return;
    }
    indicator.style.display = 'block';
    if (enabledRef) {
      indicator.textContent = '抖音防暂停 · 运行中';
      indicator.style.background = 'rgba(254,44,85, 0.55)';
    } else {
      indicator.textContent = '抖音防暂停 · 已关闭';
      indicator.style.background = 'rgba(120,120,120,0.5)';
    }
  }

  // 全屏切换时同步隐藏/恢复浮标
  ['fullscreenchange', 'webkitfullscreenchange', 'msfullscreenchange'].forEach(function (ev) {
    document.addEventListener(ev, updateIndicator, false);
  });

  // ===== 1) 伪装可见性 API（拦截抖音后台检测） =====
  function patchVisibility() {
    try { Object.defineProperty(document, 'hidden', { configurable: false, get: function () { return false; } }); } catch (e) {}
    try { Object.defineProperty(document, 'visibilityState', { configurable: false, get: function () { return 'visible'; } }); } catch (e) {}
    try { Object.defineProperty(document, 'webkitHidden', { configurable: false, get: function () { return false; } }); } catch (e) {}
  }

  // ===== 2) 伪装 hasFocus =====
  function patchFocus() {
    try {
      Object.defineProperty(Document.prototype, 'hasFocus', { configurable: false, value: function () { return true; } });
    } catch (e) {
      try { Object.defineProperty(document, 'hasFocus', { configurable: false, value: function () { return true; } }); } catch (e2) {}
    }
  }

  // ===== 3) 静音循环音频（防 Chrome 冻结后台标签页） =====
  function silentAudio() {
    if (window.__keepAliveDone) return;
    window.__keepAliveDone = true;
    try {
      var sampleRate = 8000;
      var numSamples = sampleRate / 2;
      var dataSize = numSamples;
      var buf = new ArrayBuffer(44 + dataSize);
      var v = new DataView(buf);
      v.setUint8(0, 0x52); v.setUint8(1, 0x49); v.setUint8(2, 0x46); v.setUint8(3, 0x46);
      v.setUint32(4, 36 + dataSize, true);
      v.setUint8(8, 0x57); v.setUint8(9, 0x41); v.setUint8(10, 0x56); v.setUint8(11, 0x45);
      v.setUint8(12, 0x66); v.setUint8(13, 0x6d); v.setUint8(14, 0x74); v.setUint8(15, 0x20);
      v.setUint32(16, 16, true);
      v.setUint16(20, 1, true);
      v.setUint16(22, 1, true);
      v.setUint32(24, sampleRate, true);
      v.setUint32(28, sampleRate, true);
      v.setUint16(32, 1, true);
      v.setUint16(34, 8, true);
      v.setUint8(36, 0x64); v.setUint8(37, 0x61); v.setUint8(38, 0x74); v.setUint8(39, 0x61);
      v.setUint32(40, dataSize, true);
      for (var i = 44; i < buf.byteLength; i++) v.setUint8(i, 0x80);
      var blob = new Blob([buf], { type: 'audio/wav' });
      var url = URL.createObjectURL(blob);
      var audio = new Audio(url);
      audio.loop = true;
      audio.volume = 0;
      audio.setAttribute('aria-hidden', 'true');
      audio.style.cssText = 'position:fixed;left:-9999px;top:-9999px;width:1px;height:1px;opacity:0;pointer-events:none;';
      var appendAndPlay = function () {
        (document.body || document.documentElement).appendChild(audio);
        var p = audio.play();
        if (p && p.catch) p.catch(function () {});
      };
      if (document.body) appendAndPlay();
      else document.addEventListener('DOMContentLoaded', appendAndPlay, { once: true });
      window.__keepAliveAudio = audio;
    } catch (e) {
      try {
        var ac = new (window.AudioContext || window.webkitAudioContext)();
        var osc = ac.createOscillator();
        var gain = ac.createGain();
        gain.gain.value = 0.0001;
        osc.connect(gain).connect(ac.destination);
        osc.start();
        window.__keepAliveAC = ac;
      } catch (e2) {}
    }
  }

  // ===== 4) 拦截更广事件监听 =====
  var BLOCKED = { visibilitychange: 1, webkitvisibilitychange: 1, pagehide: 1, pageshow: 1, blur: 1, focus: 1, focusin: 1, focusout: 1 };
  var nativeAdd = EventTarget.prototype.addEventListener;
  var nativeRemove = EventTarget.prototype.removeEventListener;
  var eventsPatched = false;
  function shouldBlock(type, target) {
    if (!BLOCKED[type]) return false;
    return target === document || target === window;
  }
  function patchEvents() {
    if (eventsPatched) return;
    eventsPatched = true;
    EventTarget.prototype.addEventListener = function (type, listener, options) {
      if (shouldBlock(type, this)) return;
      return nativeAdd.call(this, type, listener, options);
    };
    EventTarget.prototype.removeEventListener = function (type, listener, options) {
      if (shouldBlock(type, this)) return;
      return nativeRemove.call(this, type, listener, options);
    };
  }

  // ===== 5) 自动恢复：只恢复当前激活媒体，且避开用户操作期 =====
  function autoResume() {
    if (window.__keepAliveResumeInstalled) return;
    window.__keepAliveResumeInstalled =  true;

    var lastActivity = 0;                       // 任意页面交互时间（用于避让临时操作）
    var videoClickTime = 0;                     // 最近一次点击视频/播放器控件的时间
    var userPaused = false;                      // 用户主动暂停（粘滞，直到下次播放）

    // 记录用户在视频/播放器区域内的点击，用于区分「主动暂停」与「系统后台暂停」
    document.addEventListener('mousedown', function (e) {
      var t = e.target;
      if (!t || !t.closest) return;
      if (t.tagName === 'VIDEO' || t.closest('video, [class*="player"], [data-e2e="play-button"]')) {
        videoClickTime = Date.now();
      }
    }, true);

    var mark = function () { lastActivity = Date.now(); };
    ['keydown', 'wheel', 'touchstart'].forEach(function (ev) {
      document.addEventListener(ev, mark, true);
    });

    var activeMedia = null;
    var tryHook = function (el) {
      if (!el || el.__keepAliveHooked) return;
      el.__keepAliveHooked = true;
      el.addEventListener('play', function () { activeMedia = el; userPaused = false; });
      el.addEventListener('pause', function () {
        if (activeMedia !== el) return;          // 抖音切走旧视频 → 忽略
        if (!enabledRef) return;                 // 已关闭 → 不恢复
        if (Date.now() - videoClickTime < USER_CLICK_COOLDOWN) {
          userPaused = true;                     // 用户刚点过播放器 → 视为主动暂停，保持
          return;
        }
        // 非用户操作的暂停（系统/后台）→ 自动恢复
        var p = el.play();
        if (p && p.catch) p.catch(function () {});
      });
    };
    var scan = function () {
      var list = document.querySelectorAll('video, audio');
      for (var i = 0; i < list.length; i++) tryHook(list[i]);
    };
    scan();
    new MutationObserver(scan).observe(document.documentElement || document, { childList: true, subtree: true });

    setInterval(function () {
      if (!enabledRef || userPaused) return;     // 已关闭 或 用户主动暂停 → 不恢复
      if (Date.now() - lastActivity < USER_CLICK_COOLDOWN) return;
      if (!activeMedia) return;
      if (activeMedia.paused && !activeMedia.ended && activeMedia.readyState >= 2) {
        var p = activeMedia.play();
        if (p && p.catch) p.catch(function () {});
      }
    }, 1000);
  }

  // ===== 启动 =====
  function apply() {
    if (!getEnabled()) { enabledRef = false; updateIndicator(); return; }
    enabledRef = true;
    patchVisibility();
    patchFocus();
    patchEvents();
    silentAudio();
    autoResume();
    updateIndicator();
  }

  if (document.body) ensureIndicator();
  else document.addEventListener('DOMContentLoaded', function () { ensureIndicator(); }, { once: true });

  apply();

  // 脚本猫 / 油猴菜单命令：一键切换开关（即时生效，无需刷新）
  if (typeof GM_registerMenuCommand === 'function') {
    GM_registerMenuCommand('切换 抖音防暂停 开关', function () {
      setEnabled(!getEnabled());
    });
    GM_registerMenuCommand('刷新状态显示', function () {
      ensureIndicator();
      updateIndicator();
    });
  }
})();