// ==UserScript==
// @name         B站 m4s 合并工具
// @namespace    https://github.com/bili-m4s-merge
// @version      1.0.0
// @description  在浏览器内将 B站的 video.m4s + audio.m4s 合并为 MP4 并下载（基于 ffmpeg.wasm，无需安装任何软件）。支持本地文件合并，也可尝试直接抓取当前 B 站视频。
// @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';

  const CDN_LIST = [
    'https://cdn.jsdelivr.net/npm/@ffmpeg/ffmpeg@0.11.6/dist/ffmpeg.min.js',
    'https://unpkg.com/@ffmpeg/ffmpeg@0.11.6/dist/ffmpeg.min.js',
  ];

  let ffmpeg = null;
  let loading = false;

  // ---- 动态加载 ffmpeg.wasm ----
  function loadScript(url) {
    return new Promise((resolve, reject) => {
      const s = document.createElement('script');
      s.src = url;
      s.onload = () => resolve();
      s.onerror = () => reject(new Error('load ' + url));
      document.head.appendChild(s);
    });
  }

  async function ensureFFmpeg(log) {
    if (ffmpeg) return ffmpeg;
    if (loading) throw new Error('ffmpeg 正在加载中…');
    loading = true;
    log('正在加载 ffmpeg.wasm …');
    let loaded = false;
    for (const url of CDN_LIST) {
      try {
        await loadScript(url);
        loaded = true;
        break;
      } catch (e) { /* try next */ }
    }
    if (!loaded || typeof window.createFFmpeg === 'undefined') {
      loading = false;
      throw new Error('无法从 CDN 加载 ffmpeg，请检查网络或换用本地 EXE 版。');
    }
    ffmpeg = window.createFFmpeg({
      coreURL: 'https://cdn.jsdelivr.net/npm/@ffmpeg/core@0.11.1/dist/ffmpeg-core.js',
      wasmURL: 'https://cdn.jsdelivr.net/npm/@ffmpeg/core@0.11.1/dist/ffmpeg-core.wasm',
      logger: ({ message }) => log(message),
    });
    await ffmpeg.load();
    loading = false;
    log('ffmpeg 就绪 ✓');
    return ffmpeg;
  }

  // ---- 合并：video.m4s + audio.m4s -> out.mp4 ----
  async function mergeFiles(videoFile, audioFile, outputName, log, onProgress) {
    const ff = await ensureFFmpeg(log);
    log('写入输入文件…');
    ff.FS('writeFile', 'video.m4s', await videoFile.arrayBuffer());
    ff.FS('writeFile', 'audio.m4s', await audioFile.arrayBuffer());
    const re = ff.run('-i', 'video.m4s', '-i', 'audio.m4s', '-c', 'copy', '-movflags', '+faststart', 'out.mp4');
    await re;
    log('读取输出文件…');
    const data = ff.FS('readFile', 'out.mp4');
    const blob = new Blob([data.buffer], { type: 'video/mp4' });
    const url = URL.createObjectURL(blob);
    const a = document.createElement('a');
    a.href = url;
    a.download = outputName || 'bilibili_merged.mp4';
    document.body.appendChild(a);
    a.click();
    a.remove();
    setTimeout(() => URL.revokeObjectURL(url), 5000);
    ff.FS('unlink', 'video.m4s');
    ff.FS('unlink', 'audio.m4s');
    ff.FS('unlink', 'out.mp4');
    log('✅ 已触发下载: ' + (outputName || 'bilibili_merged.mp4'));
  }

  // ---- 尝试从当前 B 站页面抓取 dash 流（best-effort）----
  async function grabCurrent(log) {
    const m = location.href.match(/BV\w+/);
    if (!m) { log('未在当前页面识别到 BV 号。'); return; }
    const bvid = m[0];
    const api = `https://api.bilibili.com/x/player/playurl?bvid=${bvid}&qn=127&fnval=16&fourk=1`;
    log('请求 playurl: ' + bvid);
    const resp = await fetch(api, { credentials: 'include' });
    const json = await resp.json();
    const dash = json?.data?.dash;
    if (!dash) { log('未获取到 dash 流（可能需要登录或受限制）。'); return null; }
    const pick = (arr) => arr && arr.length ? arr.reduce((a, b) => (b.bandwidth > a.bandwidth ? b : a)) : null;
    const v = pick(dash.video), a = pick(dash.audio) || pick(dash.dolby?.audio);
    return { videoUrl: v?.baseUrl, audioUrl: a?.baseUrl };
  }

  async function fetchAsFile(url, name) {
    const r = await fetch(url, { credentials: 'include', headers: { Referer: 'https://www.bilibili.com/' } });
    const buf = await r.arrayBuffer();
    return new File([buf], name);
  }

  // ---- 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:320px;background:#fff;border:1px solid #fb7299;border-radius:12px;box-shadow:0 6px 24px rgba(0,0,0,.18);z-index:999999;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}
    #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:96px;overflow:auto;white-space:pre-wrap;font-family:Consolas,monospace;font-size:11px;color:#333}
    #bili-m4s-panel .row{display:flex;gap:6px}
    #bili-m4s-panel .row button{flex:1}
    #bili-m4s-panel .x{cursor:pointer;font-weight:400}`;
    document.head.appendChild(style);

    const panel = document.createElement('div');
    panel.id = 'bili-m4s-panel';
    panel.innerHTML = `
      <div class="hd"><span>📦 m4s 合并工具</span><span class="x" title="收起">✕</span></div>
      <div class="bd">
        <div>① 选择视频流 <input type="file" id="m4s-v" accept=".m4s,.mp4,.m4v"></div>
        <div>② 选择音频流 <input type="file" id="m4s-a" accept=".m4s,.m4a,.aac"></div>
        <div>输出文件名 <input type="text" id="m4s-name" value="bilibili_merged.mp4" style="width:100%;box-sizing:border-box;padding:4px"></div>
        <div class="row">
          <button id="m4s-merge">🚀 合并并下载</button>
          <button id="m4s-grab" class="ghost">从本页抓取</button>
        </div>
        <div class="log" id="m4s-log">就绪。选择两个 m4s 文件后点击合并。</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;

    panel.querySelector('#m4s-merge').onclick = async () => {
      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; }
      const btn = panel.querySelector('#m4s-merge');
      btn.disabled = true;
      try {
        await mergeFiles(v, a, panel.querySelector('#m4s-name').value || 'bilibili_merged.mp4', log);
      } catch (e) {
        log('❌ ' + e.message);
      } finally {
        btn.disabled = false;
      }
    };

    panel.querySelector('#m4s-grab').onclick = async () => {
      const btn = panel.querySelector('#m4s-grab');
      btn.disabled = true;
      try {
        const urls = await grabCurrent(log);
        if (urls && urls.videoUrl && urls.audioUrl) {
          log('抓取成功，开始下载并合并…');
          const v = await fetchAsFile(urls.videoUrl, 'video.m4s');
          const a = await fetchAsFile(urls.audioUrl, 'audio.m4s');
          await mergeFiles(v, a, panel.querySelector('#m4s-name').value || 'bilibili_merged.mp4', log);
        } else {
          log('抓取失败（B站可能限制了跨域/需登录）。请改用①手动选择已下载的 m4s 文件。');
        }
      } catch (e) {
        log('❌ ' + e.message);
      } finally {
        btn.disabled = false;
      }
    };
  }

  // 延迟一点确保页面稳定
  setTimeout(buildUI, 1500);

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