// ==UserScript==
// @name         B站 m4s 合并 / 在线解析下载
// @namespace    https://github.com/bili-m4s-merge
// @version      2.0.0
// @description  纯浏览器方案（mp4box.js，无需 ffmpeg、无需 SharedArrayBuffer、无需任何本地软件）。① 在线解析当前 B 站视频并下载音视频流合并为 MP4；② 选择本地 video.m4s + audio.m4s 合并为 MP4。无损封装，速度快。
// @author       WorkBuddy
// @match        https://www.bilibili.com/*
// @match        https://www.bilibili.tv/*
// @match        https://m.bilibili.com/*
// @grant        none
// @run-at       document-idle
// @license      MIT
// ==/UserScript==

(function () {
  'use strict';

  // mp4box.js 单文件 UMD 构建（纯 JS，不需要 SharedArrayBuffer，普通页面即可运行）
  const MP4BOX_CDN = 'https://cdn.jsdelivr.net/npm/mp4box@0.5.2/dist/mp4box.all.min.js';

  let MP4Box = null;
  let loading = false;

  // ---------- 动态加载 mp4box.js ----------
  function loadScript(url) {
    return new Promise((resolve, reject) => {
      if (document.querySelector('script[data-mp4box]')) return resolve();
      const s = document.createElement('script');
      s.src = url;
      s.dataset.mp4box = '1';
      s.onload = () => resolve();
      s.onerror = () => reject(new Error('加载 mp4box.js 失败（可能是网络问题）'));
      document.head.appendChild(s);
    });
  }

  async function ensureMP4Box(log) {
    if (MP4Box && MP4Box.createFile && typeof DataStream !== 'undefined') return MP4Box;
    if (loading) throw new Error('mp4box.js 正在加载中…');
    loading = true;
    log('加载 mp4box.js …');
    await loadScript(MP4BOX_CDN);
    MP4Box = window.MP4Box || window.mp4box || MP4Box;
    if (!MP4Box || !MP4Box.createFile) throw new Error('mp4box.js 加载后不可用');
    loading = false;
    log('mp4box.js 就绪 ✓');
    return MP4Box;
  }

  // ---------- 工具 ----------
  function boxToBytes(box) {
    const stream = new DataStream(undefined, 0, DataStream.BIG_ENDIAN);
    box.write(stream);
    return new Uint8Array(stream.buffer, 0, stream.position);
  }
  function stripBoxHeader(bytes) {
    // 去掉 8 字节 box 头（size + type），返回独立的 ArrayBuffer
    // 写入端 avcDecoderConfigRecord / hevcDecoderConfigRecord 必须是真正的 ArrayBuffer，不能传 Uint8Array 视图
    return bytes.buffer.slice(bytes.byteOffset + 8, bytes.byteOffset + bytes.length);
  }
  function downloadBlob(blob, name) {
    const url = URL.createObjectURL(blob);
    const a = document.createElement('a');
    a.href = url;
    a.download = name;
    document.body.appendChild(a);
    a.click();
    a.remove();
    setTimeout(() => URL.revokeObjectURL(url), 8000);
  }
  function sanitize(name) {
    return (name || 'bilibili_merged').replace(/[\\/:*?"<>|\n\r\t]/g, '_').slice(0, 120);
  }

  // ---------- MD5（WBI 签名用，浏览器无原生 MD5；采用经 Node crypto 交叉校验的 blueimp-md5 实现） ----------
  function safeAdd(x, y) {
    const lsw = (x & 0xffff) + (y & 0xffff);
    const msw = (x >> 16) + (y >> 16) + (lsw >> 16);
    return (msw << 16) | (lsw & 0xffff);
  }
  function bitRotateLeft(num, cnt) { return (num << cnt) | (num >>> (32 - cnt)); }
  function md5cmn(q, a, b, x, s, t) { return safeAdd(bitRotateLeft(safeAdd(safeAdd(a, q), safeAdd(x, t)), s), b); }
  function md5ff(a, b, c, d, x, s, t) { return md5cmn((b & c) | (~b & d), a, b, x, s, t); }
  function md5gg(a, b, c, d, x, s, t) { return md5cmn((b & d) | (c & ~d), a, b, x, s, t); }
  function md5hh(a, b, c, d, x, s, t) { return md5cmn(b ^ c ^ d, a, b, x, s, t); }
  function md5ii(a, b, c, d, x, s, t) { return md5cmn(c ^ (b | ~d), a, b, x, s, t); }
  function binlMD5(x, len) {
    x[len >> 5] |= 0x80 << len % 32;
    x[(((len + 64) >>> 9) << 4) + 14] = len;
    let a = 1732584193, b = -271733879, c = -1732584194, d = 271733878;
    for (let i = 0; i < x.length; i += 16) {
      const olda = a, oldb = b, oldc = c, oldd = d;
      a = md5ff(a,b,c,d,x[i],7,-680876936); d = md5ff(d,a,b,c,x[i+1],12,-389564586); c = md5ff(c,d,a,b,x[i+2],17,606105819); b = md5ff(b,c,d,a,x[i+3],22,-1044525330);
      a = md5ff(a,b,c,d,x[i+4],7,-176418897); d = md5ff(d,a,b,c,x[i+5],12,1200080426); c = md5ff(c,d,a,b,x[i+6],17,-1473231341); b = md5ff(b,c,d,a,x[i+7],22,-45705983);
      a = md5ff(a,b,c,d,x[i+8],7,1770035416); d = md5ff(d,a,b,c,x[i+9],12,-1958414417); c = md5ff(c,d,a,b,x[i+10],17,-42063); b = md5ff(b,c,d,a,x[i+11],22,-1990404162);
      a = md5ff(a,b,c,d,x[i+12],7,1804603682); d = md5ff(d,a,b,c,x[i+13],12,-40341101); c = md5ff(c,d,a,b,x[i+14],17,-1502002290); b = md5ff(b,c,d,a,x[i+15],22,1236535329);
      a = md5gg(a,b,c,d,x[i+1],5,-165796510); d = md5gg(d,a,b,c,x[i+6],9,-1069501632); c = md5gg(c,d,a,b,x[i+11],14,643717713); b = md5gg(b,c,d,a,x[i],20,-373897302);
      a = md5gg(a,b,c,d,x[i+5],5,-701558691); d = md5gg(d,a,b,c,x[i+10],9,38016083); c = md5gg(c,d,a,b,x[i+15],14,-660478335); b = md5gg(b,c,d,a,x[i+4],20,-405537848);
      a = md5gg(a,b,c,d,x[i+9],5,568446438); d = md5gg(d,a,b,c,x[i+14],9,-1019803690); c = md5gg(c,d,a,b,x[i+3],14,-187363961); b = md5gg(b,c,d,a,x[i+8],20,1163531501);
      a = md5gg(a,b,c,d,x[i+13],5,-1444681467); d = md5gg(d,a,b,c,x[i+2],9,-51403784); c = md5gg(c,d,a,b,x[i+7],14,1735328473); b = md5gg(b,c,d,a,x[i+12],20,-1926607734);
      a = md5hh(a,b,c,d,x[i+5],4,-378558); d = md5hh(d,a,b,c,x[i+8],11,-2022574463); c = md5hh(c,d,a,b,x[i+11],16,1839030562); b = md5hh(b,c,d,a,x[i+14],23,-35309556);
      a = md5hh(a,b,c,d,x[i+1],4,-1530992060); d = md5hh(d,a,b,c,x[i+4],11,1272893353); c = md5hh(c,d,a,b,x[i+7],16,-155497632); b = md5hh(b,c,d,a,x[i+10],23,-1094730640);
      a = md5hh(a,b,c,d,x[i+13],4,681279174); d = md5hh(d,a,b,c,x[i],11,-358537222); c = md5hh(c,d,a,b,x[i+3],16,-722521979); b = md5hh(b,c,d,a,x[i+6],23,76029189);
      a = md5hh(a,b,c,d,x[i+9],4,-640364487); d = md5hh(d,a,b,c,x[i+12],11,-421815835); c = md5hh(c,d,a,b,x[i+15],16,530742520); b = md5hh(b,c,d,a,x[i+2],23,-995338651);
      a = md5ii(a,b,c,d,x[i],6,-198630844); d = md5ii(d,a,b,c,x[i+7],10,1126891415); c = md5ii(c,d,a,b,x[i+14],15,-1416354905); b = md5ii(b,c,d,a,x[i+5],21,-57434055);
      a = md5ii(a,b,c,d,x[i+12],6,1700485571); d = md5ii(d,a,b,c,x[i+3],10,-1894986606); c = md5ii(c,d,a,b,x[i+10],15,-1051523); b = md5ii(b,c,d,a,x[i+1],21,-2054922799);
      a = md5ii(a,b,c,d,x[i+8],6,1873313359); d = md5ii(d,a,b,c,x[i+15],10,-30611744); c = md5ii(c,d,a,b,x[i+6],15,-1560198380); b = md5ii(b,c,d,a,x[i+13],21,1309151649);
      a = md5ii(a,b,c,d,x[i+4],6,-145523070); d = md5ii(d,a,b,c,x[i+11],10,-1120210379); c = md5ii(c,d,a,b,x[i+2],15,718787259); b = md5ii(b,c,d,a,x[i+9],21,-343485551);
      a = safeAdd(a, olda); b = safeAdd(b, oldb); c = safeAdd(c, oldc); d = safeAdd(d, oldd);
    }
    return [a, b, c, d];
  }
  function binl2rstr(input) {
    let output = '';
    const length32 = input.length * 32;
    for (let i = 0; i < length32; i += 8) output += String.fromCharCode((input[i >> 5] >>> i % 32) & 0xff);
    return output;
  }
  function rstr2binl(input) {
    const output = [];
    output[(input.length >> 2) - 1] = undefined;
    for (let i = 0; i < output.length; i += 1) output[i] = 0;
    const length8 = input.length * 8;
    for (let i = 0; i < length8; i += 8) output[i >> 5] |= (input.charCodeAt(i / 8) & 0xff) << i % 32;
    return output;
  }
  function rstrMD5(s) { return binl2rstr(binlMD5(rstr2binl(s), s.length * 8)); }
  function rstr2hex(input) {
    const hexTab = '0123456789abcdef';
    let output = '';
    for (let i = 0; i < input.length; i += 1) {
      const x = input.charCodeAt(i);
      output += hexTab.charAt((x >>> 4) & 0x0f) + hexTab.charAt(x & 0x0f);
    }
    return output;
  }
  function str2rstrUTF8(input) { return unescape(encodeURIComponent(input)); }
  function rawMD5(s) { return rstrMD5(str2rstrUTF8(s)); }
  function hexMD5(s) { return rstr2hex(rawMD5(s)); }
  function md5(s) { return hexMD5(s); }

  // ---------- 解析单个 m4s/mp4 片段，提取样本 + 轨道配置 ----------
  function extractSamples(arrayBuffer) {
    return new Promise((resolve, reject) => {
      const file = MP4Box.createFile();
      const collected = [];
      let total = 0;
      let trackInfo = null;
      let finished = false;
      const finish = () => {
        if (finished) return;
        finished = true;
        const trak = file.getTrackById(trackInfo.id);
        resolve({ samples: collected, track: trackInfo, trak });
      };
      file.onError = (e) => reject(new Error('解析失败: ' + e));
      file.onReady = (info) => {
        if (!info.tracks || !info.tracks.length) {
          reject(new Error('文件中未找到音视频轨道'));
          return;
        }
        trackInfo = info.tracks[0];
        total = trackInfo.nb_samples || 0;
        file.setExtractionOptions(trackInfo.id, null, { nbSamples: Infinity });
        file.start();
      };
      file.onSamples = (id, user, samples) => {
        for (let i = 0; i < samples.length; i++) collected.push(samples[i]);
        if (total > 0 ? collected.length >= total : collected.length > 0) finish();
      };
      arrayBuffer.fileStart = 0;
      file.appendBuffer(arrayBuffer);
      file.flush();
      // 兜底：若解析异常未触发回调
      setTimeout(() => {
        if (!finished && collected.length) finish();
      }, 15000);
    });
  }

  // ---------- 核心：合并 视频流 + 音频流 -> MP4 ----------
  async function mergeToMP4(videoBuf, audioBuf, outputName, log) {
    const MB = await ensureMP4Box(log);

    log('解析视频流…');
    const v = await extractSamples(videoBuf);
    log('解析音频流…');
    const a = await extractSamples(audioBuf);

    // ---- 视频轨配置 ----
    const vEntry = v.trak.mdia.minf.stbl.stsd.entries[0];
    let vType, vConfigBox = null;
    if (vEntry.avcC) {
      vType = 'avc1';
    } else if (vEntry.hvcC) {
      vType = 'hvc1';
      vConfigBox = vEntry.hvcC; // mp4box 0.5.x 写入端不识别 hevcDecoderConfigRecord，需手动 addBox
    } else if (vEntry.av1C) {
      vType = 'av01';
      vConfigBox = vEntry.av1C;
    } else {
      throw new Error('不支持的视频编码（仅支持 H.264/HEVC/AV1，当前: ' + (v.track.codec || '未知') + '）。');
    }

    // ---- 音频轨配置（esds）----
    const aEntry = a.trak.mdia.minf.stbl.stsd.entries[0];
    const aEsds = aEntry.esds || (aEntry.wave && aEntry.wave.esds);
    if (!aEsds) throw new Error('未找到音频 esds 配置，无法封装。');

    log('封装为 MP4（无损）…');
    const out = MB.createFile();
    const vId = out.addTrack({
      type: vType,
      width: v.track.video.width,
      height: v.track.video.height,
      timescale: v.track.timescale,
      duration: v.track.duration,
      ...(vType === 'avc1'
        ? { avcDecoderConfigRecord: stripBoxHeader(boxToBytes(vEntry.avcC)) }
        : {}),
    });
    // HEVC/AV1：把原样解析到的配置盒子挂到输出 stsd entry
    if (vConfigBox) {
      out.getTrackById(vId).mdia.minf.stbl.stsd.entries[0].addBox(vConfigBox);
    }
    const aId = out.addTrack({
      type: 'mp4a',
      hdlr: 'soun',
      timescale: a.track.timescale,
      samplerate: (a.track.audio.sample_rate || 48000) << 16,
      channel_count: a.track.audio.channel_count || 2,
      samplesize: 16,
      description: aEsds,
    });

    for (const s of v.samples) {
      out.addSample(vId, new Uint8Array(s.data), {
        duration: s.duration, cts: s.cts, dts: s.dts, is_sync: s.is_sync,
      });
    }
    for (const s of a.samples) {
      out.addSample(aId, new Uint8Array(s.data), {
        duration: s.duration, cts: s.cts, dts: s.dts, is_sync: s.is_sync,
      });
    }

    const stream = out.getBuffer();
    // mp4box.js 0.5.x 的 getBuffer() 直接返回 ArrayBuffer；旧版可能返回带 .buffer/.position 的 DataStream，做兼容
    const outBytes = stream instanceof ArrayBuffer
      ? stream
      : (stream.buffer && typeof stream.position === 'number'
        ? stream.buffer.slice(0, stream.position)
        : stream);
    const blob = new Blob([outBytes], { type: 'video/mp4' });
    downloadBlob(blob, sanitize(outputName) + '.mp4');
    log('✅ 合并完成并触发下载: ' + sanitize(outputName) + '.mp4');
  }

  // ---------- B 站 WBI 签名（playurl 等接口强制校验） ----------
  const WBI_TABLE = [46, 47, 18, 2, 53, 8, 23, 32, 15, 50, 10, 31, 58, 3, 45, 35, 27, 43, 5, 49, 33, 9, 42, 19, 29, 28, 14, 39, 12, 38, 41, 13, 37, 48, 7, 16, 24, 55, 40, 61, 26, 17, 0, 1, 60, 51, 30, 4, 22, 25, 54, 21, 56, 59, 6, 63, 57, 62, 11, 36, 20, 34, 44, 52];
  let _wbiMixinKey = null;
  async function getWbiMixinKey() {
    if (_wbiMixinKey) return _wbiMixinKey;
    const nav = await fetch('https://api.bilibili.com/x/web-interface/nav', {
      credentials: 'include', headers: { Referer: location.origin + '/' },
    }).then((r) => r.json());
    if (!nav.data || !nav.data.wbi_img) throw new Error('获取 WBI 密钥失败（请确认已在 B 站登录）。');
    const img = nav.data.wbi_img.img_url.split('/').pop().split('.')[0];
    const sub = nav.data.wbi_img.sub_url.split('/').pop().split('.')[0];
    const combined = img + sub;
    _wbiMixinKey = WBI_TABLE.map((i) => combined[i]).join('').slice(0, 32);
    return _wbiMixinKey;
  }
  // 带 WBI 签名的 GET 请求，返回 JSON
  async function wbiGet(urlBase, params) {
    const mixin = await getWbiMixinKey();
    const p = Object.assign({ wts: Math.floor(Date.now() / 1000) }, params);
    const query = Object.keys(p).sort()
      .map((k) => encodeURIComponent(k) + '=' + encodeURIComponent(p[k])).join('&');
    const w_rid = md5(query + mixin);
    const url = urlBase + '?' + query + '&w_rid=' + w_rid;
    const resp = await fetch(url, { credentials: 'include', headers: { Referer: location.origin + '/' } });
    return resp.json();
  }

  // ---------- 在线解析当前 B 站视频 ----------
  function codecName(v) {
    const c = (v.codecs || '').toLowerCase();
    if (c.startsWith('hvc1') || c.startsWith('hev1') || v.codecid === 12) return 'HEVC';
    if (c.startsWith('avc1') || c.startsWith('avc3') || v.codecid === 7) return 'AVC';
    if (c.startsWith('av01') || v.codecid === 13) return 'AV1';
    return v.codecs || ('codecid:' + (v.codecid || '?'));
  }
  function isHevc(v) {
    const c = (v.codecs || '').toLowerCase();
    return c.startsWith('hvc1') || c.startsWith('hev1') || v.codecid === 12;
  }
  function isAvc(v) {
    const c = (v.codecs || '').toLowerCase();
    return c.startsWith('avc1') || c.startsWith('avc3') || v.codecid === 7;
  }
  function pickVideoStream(videoList) {
    if (!videoList || !videoList.length) return null;
    // 按清晰度 id 分组，优先最高清晰度；同清晰度优先 HEVC(hvc1/hev1)，其次 AVC
    const byId = {};
    for (const v of videoList) {
      const id = v.id || 0;
      if (!byId[id]) byId[id] = [];
      byId[id].push(v);
    }
    const ids = Object.keys(byId).map(Number).sort((a, b) => b - a);
    for (const id of ids) {
      const list = byId[id];
      const hevc = list.find(isHevc);
      if (hevc) return hevc;
    }
    // 没有 HEVC 时，返回最高清晰度的 AVC；如果连 AVC 都没有则返回最高带宽
    for (const id of ids) {
      const list = byId[id];
      const avc = list.find(isAvc);
      if (avc) return avc;
    }
    return videoList.reduce((x, y) => ((y.bandwidth || 0) > (x.bandwidth || 0) ? y : x));
  }
  function pickAudioStream(dash) {
    const sources = [];
    if (dash.audio && dash.audio.length) sources.push(...dash.audio);
    if (dash.dolby && dash.dolby.audio && dash.dolby.audio.length) sources.push(...dash.dolby.audio);
    if (dash.flac && dash.flac.audio && dash.flac.audio.length) sources.push(...dash.flac.audio);
    if (!sources.length) return null;
    // 优先无损/高码率：flac > dolby > 普通高码率
    return sources.reduce((x, y) => ((y.bandwidth || 0) > (x.bandwidth || 0) ? y : x));
  }

  async function parseCurrentVideo(log) {
    const m = location.href.match(/BV[0-9A-Za-z]+/);
    if (!m) throw new Error('当前页面未识别到 BV 号，请在本站视频播放页使用。');
    const bvid = m[0];
    log('读取视频信息: ' + bvid);
    const view = await wbiGet('https://api.bilibili.com/x/web-interface/view', { bvid });
    if (view.code !== 0) throw new Error('获取视频信息失败: ' + (view.message || view.code));
    const cid = view.data.pages[0].cid;
    const title = view.data.title || bvid;

    log('读取播放地址（WBI 签名）…');
    // fnval=4048: 请求 DASH + HEVC/AV1/4K/8K 等全部可用流
    const play = await wbiGet('https://api.bilibili.com/x/player/playurl', {
      bvid, cid, qn: 127, fnval: 4048, fourk: 1, fnver: 0,
    });
    if (play.code !== 0 || !play.data || !play.data.dash) {
      throw new Error('获取播放地址失败: ' + (play.message || play.code) + '（可能需要登录/大会员，或所选清晰度受限）');
    }
    const dash = play.data.dash;
    const v = pickVideoStream(dash.video);
    const a = pickAudioStream(dash);
    if (!v || !a) throw new Error('未获取到音视频流（可能需要登录或该清晰度受限）。');
    return {
      title,
      videoUrl: v.baseUrl || v.base_url,
      audioUrl: a.baseUrl || a.base_url,
      vCodec: codecName(v),
      vId: v.id,
    };
  }

  async function downloadArrayBuffer(url, log, label) {
    log('下载 ' + label + ' 数据流…');
    const domain = url.replace(/^https?:\/\/([^/]+).*/, '$1');
    try {
      const resp = await fetch(url, {
        // CDN 链接已带签名，不需要携带 B 站主站 cookie；带 credentials 在部分浏览器/扩展下会触发额外限制
        credentials: 'omit',
        headers: { Referer: 'https://www.bilibili.com/' },
      });
      if (!resp.ok) throw new Error(label + ' 下载失败 (HTTP ' + resp.status + ' @ ' + domain + ')');
      const buf = await resp.arrayBuffer();
      log(label + ' 下载完成 (' + (buf.byteLength / 1048576).toFixed(1) + ' MB)');
      return buf;
    } catch (e) {
      if (e.name === 'TypeError' && /fetch|network|cors/i.test(e.message)) {
        throw new Error(label + ' 下载被浏览器/扩展拦截 (CORS/混合内容/域名: ' + domain + ')。建议改用下方“本地合并”。');
      }
      throw new Error(label + ' 下载失败: ' + e.message + ' (域名: ' + domain + ')');
    }
  }

  // ---------- UI ----------
  function buildUI() {
    if (document.getElementById('bili-m4s-panel')) return;
    const style = document.createElement('style');
    style.textContent = `#bili-m4s-panel{position:fixed;right:16px;bottom:16px;width:340px;background:#fff;border:1px solid #fb7299;border-radius:12px;box-shadow:0 6px 24px rgba(0,0,0,.18);z-index:2147483647;font-family:-apple-system,"PingFang SC",Microsoft YaHei,sans-serif;font-size:13px;color:#222;overflow:hidden}
    #bili-m4s-panel .hd{background:#fb7299;color:#fff;padding:8px 12px;cursor:move;display:flex;justify-content:space-between;align-items:center;font-weight:600}
    #bili-m4s-panel .bd{padding:10px 12px;display:flex;flex-direction:column;gap:8px}
    #bili-m4s-panel input[type=file]{font-size:12px;width:100%}
    #bili-m4s-panel button{background:#fb7299;color:#fff;border:none;border-radius:8px;padding:8px;cursor:pointer;font-size:13px}
    #bili-m4s-panel button:disabled{opacity:.5;cursor:not-allowed}
    #bili-m4s-panel button.ghost{background:#fff;color:#fb7299;border:1px solid #fb7299}
    #bili-m4s-panel .log{background:#f6f7f9;border-radius:8px;padding:6px;height:110px;overflow:auto;white-space:pre-wrap;font-family:Consolas,monospace;font-size:11px;color:#333}
    #bili-m4s-panel .sec{border:1px solid #f0d6e0;border-radius:8px;padding:8px;display:flex;flex-direction:column;gap:6px}
    #bili-m4s-panel .sec h4{margin:0;font-size:12px;color:#fb7299}
    #bili-m4s-panel .x{cursor:pointer;font-weight:400}
    #bili-m4s-panel .note{font-size:11px;color:#888;line-height:1.4}
    #bili-m4s-panel input.txt{width:100%;box-sizing:border-box;padding:4px;border:1px solid #ddd;border-radius:6px}`;
    document.head.appendChild(style);

    const panel = document.createElement('div');
    panel.id = 'bili-m4s-panel';
    panel.innerHTML = `
      <div class="hd"><span>📦 B站 m4s 合并工具 v2</span><span class="x" title="收起">✕</span></div>
      <div class="bd">
        <div class="sec">
          <h4>① 在线解析并下载合并（当前视频页）</h4>
          <button id="m4s-online">🌐 解析并合并当前 B 站视频</button>
          <div class="note">自动读取当前播放页的 BV 号，下载音视频流并封装为 MP4。若提示跨域/登录限制，请改用下方本地合并。</div>
        </div>
        <div class="sec">
          <h4>② 本地文件合并（video.m4s + audio.m4s）</h4>
          <div>视频流 <input type="file" id="m4s-v" accept=".m4s,.mp4,.m4v,.mov"></div>
          <div>音频流 <input type="file" id="m4s-a" accept=".m4s,.m4a,.aac,.mp4,.mov"></div>
          <div>输出文件名 <input type="text" id="m4s-name" class="txt" value="bilibili_merged"></div>
          <button id="m4s-merge">🚀 合并并下载</button>
        </div>
        <div class="log" id="m4s-log">就绪。选择一种方式开始。</div>
      </div>`;
    document.body.appendChild(panel);

    const log = (msg) => {
      const el = panel.querySelector('#m4s-log');
      el.textContent += '\n' + msg;
      el.scrollTop = el.scrollHeight;
    };

    panel.querySelector('.x').onclick = () => panel.remove();

    // 拖拽
    const hd = panel.querySelector('.hd');
    let sx, sy, ox, oy, drag = false;
    hd.onmousedown = (e) => { drag = true; sx = e.clientX; sy = e.clientY; const r = panel.getBoundingClientRect(); ox = r.left; oy = r.top; };
    document.onmousemove = (e) => { if (drag) { panel.style.left = (ox + e.clientX - sx) + 'px'; panel.style.top = (oy + e.clientY - sy) + 'px'; panel.style.right = 'auto'; panel.style.bottom = 'auto'; } };
    document.onmouseup = () => drag = false;

    const lock = (el) => (el.disabled = true);
    const unlock = (el) => (el.disabled = false);

    // 在线解析
    panel.querySelector('#m4s-online').onclick = async () => {
      const btn = panel.querySelector('#m4s-online');
      lock(btn);
      try {
        await ensureMP4Box(log);
        const info = await parseCurrentVideo(log);
        log('编码: ' + info.vCodec + '，清晰度ID: ' + info.vId + '，标题: ' + info.title);
        const vBuf = await downloadArrayBuffer(info.videoUrl, log, '视频');
        const aBuf = await downloadArrayBuffer(info.audioUrl, log, '音频');
        await mergeToMP4(vBuf, aBuf, info.title, log);
      } catch (e) {
        log('❌ ' + e.message);
      } finally {
        unlock(btn);
      }
    };

    // 本地合并
    panel.querySelector('#m4s-merge').onclick = async () => {
      const btn = panel.querySelector('#m4s-merge');
      const v = panel.querySelector('#m4s-v').files[0];
      const a = panel.querySelector('#m4s-a').files[0];
      if (!v || !a) { log('请先选择视频流和音频流两个文件。'); return; }
      lock(btn);
      try {
        const vBuf = await v.arrayBuffer(); vBuf.fileStart = 0;
        const aBuf = await a.arrayBuffer(); aBuf.fileStart = 0;
        const name = panel.querySelector('#m4s-name').value || 'bilibili_merged';
        await mergeToMP4(vBuf, aBuf, name, log);
      } catch (e) {
        log('❌ ' + e.message);
      } finally {
        unlock(btn);
      }
    };
  }

  // 延迟确保页面稳定
  setTimeout(buildUI, 1500);

  // 暴露给控制台手动调用
  window.__biliM4sMerge = { mergeToMP4, parseCurrentVideo };
})();