// ==UserScript==
// @name         BLSubSum - B站AI字幕总结
// @namespace    https://github.com/AfeyGu/BLSubSum
// @version      0.3.1
// @description  在B站视频页一键获取AI字幕（无需下载视频），调用 LLM 生成内容总结。支持多P、多字幕轨道、长视频分块总结、历史总结自动保存与恢复、可拖动悬浮按钮。
// @author       AfeyGu
// @match        https://www.bilibili.com/video/*
// @match        https://www.bilibili.com/festival/*
// @grant        GM_xmlhttpRequest
// @grant        GM_getValue
// @grant        GM_setValue
// @grant        GM_registerMenuCommand
// @connect      api.bilibili.com
// @connect      aisubtitle.hdslb.com
// @connect      *
// @icon         https://www.bilibili.com/favicon.ico
// @license      MIT
// @run-at       document-idle
// @tag          bilibili
// ==/UserScript==

/**
 * BLSubSum —— B站 AI 字幕一键总结
 *
 * 流程（见 docs/B站AI字幕接口与下载_调研报告.md）：
 *   ① x/web-interface/view?bvid=        → cid（无需登录）
 *   ② x/player/wbi/v2?bvid=&cid=        → 字幕轨道列表（需登录，浏览器 cookie 自动携带）
 *   ③ subtitle_url（auth_key 签名）      → 字幕 JSON
 *   ④ body[].content 按 ≤gap 秒合并段落  → 讲稿
 *   ⑤ 讲稿分块 → LLM map-reduce 总结
 */

(function () {
  "use strict";

  // ---------------- 配置 ----------------

  const CFG_DEFAULTS = {
    apiBase: "https://api.deepseek.com", // OpenAI 兼容端点
    apiKey: "",
    model: "deepseek-v4-flash",
    trackPref: "auto", // 字幕轨道偏好：auto / ai-zh / ai-en / ai / any
    prompt:
      "你是专业的视频内容分析师。请根据以下视频字幕讲稿总结。无论字幕是什么语言，都必须使用中文总结：" +
      "\n1. 一句话概括核心主题（使用中文）；" +
      "\n2. 3~6 个要点（每个要点一句话，使用中文）；" +
      "\n3. 值得记住的细节或金句（如有，金句可保留原文并附中文说明）。" +
      "\n只输出总结内容，不要客套话。",
    chunkChars: 6000, // 讲稿分块大小
    mergeGap: 1.0, // 字幕行间隔 ≤gap 秒合并为一段
    historySize: 30, // 历史总结保留条数，0 = 不保存
    history: [], // [{key,bvid,p,title,up,part,pagesTotal,lan,model,summary,transcript,ts}]
    fabPos: null, // FAB 按钮位置 {right,bottom}
  };

  const API = "https://api.bilibili.com";

  const cfg = (k) => GM_getValue("blsubsum." + k, CFG_DEFAULTS[k]);
  const setCfg = (k, v) => GM_setValue("blsubsum." + k, v);

  GM_registerMenuCommand("⚙️ BLSubSum 设置", openSettings);

  // ---------------- 小工具 ----------------

  const $ = (sel, root = document) => root.querySelector(sel);

  function gmFetchJSON(url) {
    return new Promise((resolve, reject) => {
      GM_xmlhttpRequest({
        method: "GET",
        url,
        timeout: 30000,
        headers: { Accept: "application/json" },
        onload: (r) => {
          try {
            resolve(JSON.parse(r.responseText));
          } catch (e) {
            reject(new Error("响应不是 JSON：" + r.responseText.slice(0, 120)));
          }
        },
        onerror: () => reject(new Error("网络请求失败：" + url)),
        ontimeout: () => reject(new Error("请求超时：" + url)),
      });
    });
  }

  async function llmChat(messages) {
    const base = cfg("apiBase").replace(/\/+$/, "");
    const res = await new Promise((resolve, reject) => {
      GM_xmlhttpRequest({
        method: "POST",
        url: base + "/chat/completions",
        timeout: 300000,
        headers: {
          "Content-Type": "application/json",
          Authorization: "Bearer " + cfg("apiKey"),
        },
        data: JSON.stringify({
          model: cfg("model"),
          messages,
          temperature: 0.3,
        }),
        onload: (r) => {
          try {
            resolve(JSON.parse(r.responseText));
          } catch (e) {
            reject(new Error("LLM 响应解析失败：" + r.responseText.slice(0, 200)));
          }
        },
        onerror: () => reject(new Error("LLM 请求失败，请检查网络 / API 地址")),
        ontimeout: () => reject(new Error("LLM 请求超时")),
      });
    });
    if (res.error) throw new Error("LLM 错误：" + (res.error.message || JSON.stringify(res.error)));
    const text = res.choices?.[0]?.message?.content;
    if (!text) throw new Error("LLM 返回为空：" + JSON.stringify(res).slice(0, 200));
    return text.trim();
  }

  function log(msg, cls = "") {
    const box = $("#bls-log");
    if (!box) return console.log("[BLSubSum]", msg);
    const div = document.createElement("div");
    div.className = "bls-log-line " + cls;
    div.textContent = msg;
    box.appendChild(div);
    box.scrollTop = box.scrollHeight;
  }

  const setTitle = (s) => {
    const el = $("#bls-title");
    if (el) el.textContent = s;
  };

  // ---------------- B站数据获取 ----------------

  function getBvid() {
    const m = location.pathname.match(/\/video\/(BV[0-9A-Za-z]+|av\d+)/);
    return m ? m[1] : null;
  }

  async function resolveVideoInfo() {
    const bvid = getBvid();
    if (!bvid) throw new Error("无法从地址解析 BV 号");
    const j = await gmFetchJSON(`${API}/x/web-interface/view?bvid=${bvid}`);
    if (j.code !== 0) throw new Error(`获取视频信息失败: ${j.code} ${j.message}`);
    const pages = j.data.pages || [];
    // 多 P：URL ?p=N（1 基），默认 1
    const p = Math.min(Math.max(parseInt(new URLSearchParams(location.search).get("p") || "1", 10), 1), pages.length);
    const page = pages[p - 1];
    return {
      bvid,
      title: j.data.title,
      up: j.data.owner?.name || "",
      p,
      pagesTotal: pages.length,
      cid: page.cid,
      part: page.part || "",
    };
  }

  async function listSubtitleTracks(bvid, cid) {
    const j = await gmFetchJSON(`${API}/x/player/wbi/v2?bvid=${bvid}&cid=${cid}`);
    if (j.code !== 0) throw new Error(`字幕接口失败: ${j.code} ${j.message}`);
    const d = j.data || {};
    if (d.need_login_subtitle) throw new Error("该视频字幕需要登录：请先登录B站账号后重试");
    const subs = (d.subtitle && d.subtitle.subtitles) || [];
    return subs.filter((s) => s.subtitle_url && s.lan);
  }

  function pickTrack(subs) {
    // 优先 AI 中文 → AI 英文 → 其他 AI → 任意上传字幕
    const order = ["ai-zh", "ai-en"];
    for (const lan of order) {
      const hit = subs.find((s) => s.lan === lan);
      if (hit) return hit;
    }
    return subs.find((s) => String(s.lan).startsWith("ai-")) || subs[0];
  }

  // 按设置的字幕轨道偏好挑选；偏好不可用时回退自动顺序
  function pickTrackByPref(tracks, pref) {
    if (pref && pref !== "auto") {
      const hit = pref === "ai" ? tracks.find((t) => String(t.lan).startsWith("ai-")) : tracks.find((t) => t.lan === pref);
      if (hit) return hit;
      log(`⚠️ 字幕轨道偏好 ${pref} 在本视频不可用，已自动选择`);
    }
    return pickTrack(tracks);
  }

  async function fetchSubtitleBody(track) {
    const url = track.subtitle_url.startsWith("//") ? "https:" + track.subtitle_url : track.subtitle_url;
    const j = await gmFetchJSON(url); // auth_key 签名 URL，无需 cookie
    return j.body || [];
  }

  function transcriptFromBody(body, gap) {
    const paras = [];
    let cur = [];
    let prevTo = null;
    for (const e of body) {
      if (prevTo !== null && e.from - prevTo > gap) {
        paras.push(cur.join(""));
        cur = [];
      }
      cur.push(e.content);
      prevTo = e.to;
    }
    if (cur.length) paras.push(cur.join(""));
    return paras.join("\n\n");
  }

  // ---------------- 总结（map-reduce 分块） ----------------

  function splitChunks(text, maxChars) {
    const paras = text.split("\n\n");
    const chunks = [];
    let cur = [];
    let len = 0;
    for (const p of paras) {
      if (len + p.length > maxChars && cur.length) {
        chunks.push(cur.join("\n\n"));
        cur = [];
        len = 0;
      }
      cur.push(p);
      len += p.length + 2;
    }
    if (cur.length) chunks.push(cur.join("\n\n"));
    return chunks;
  }

  async function summarize(transcript, extra, onProgress) {
    const sysPrompt = `<总结提示词>:\n${cfg("prompt")}`;
    const extraBlock = extra ? `<补充提示词(最高优先级)>:\n${extra}\n\n` : "";
    const chunks = splitChunks(transcript, cfg("chunkChars"));
    if (chunks.length === 1) {
      onProgress("调用 LLM 总结…");
      return llmChat([
        { role: "system", content: sysPrompt },
        { role: "user", content: `${extraBlock}<原稿>:\n${chunks[0]}` },
      ]);
    }
    // 长视频：分块摘要 → 汇总
    const partials = [];
    for (let i = 0; i < chunks.length; i++) {
      onProgress(`分块总结 ${i + 1}/${chunks.length}…`);
      const prev = partials.length ? `<前文已总结内容>:\n${partials[partials.length - 1]}\n\n` : "";
      const note = `（这是长视频讲稿的第 ${i + 1}/${chunks.length} 段，请先总结该段要点）\n\n`;
      const s = await llmChat([
        { role: "system", content: sysPrompt },
        { role: "user", content: `${extraBlock}${prev}${note}<原稿>:\n${chunks[i]}` },
      ]);
      partials.push(s);
    }
    onProgress(`汇总 ${chunks.length} 个分块…`);
    return llmChat([
      { role: "system", content: sysPrompt },
      {
        role: "user",
        content:
          `${extraBlock}（下面是长视频各部分的分段总结，请整合为一份完整总结）\n\n` +
          `<分段总结>:\n${partials.join("\n\n---\n\n")}`,
      },
    ]);
  }

  // ---------------- UI ----------------

  const CSS = `
#bls-fab{position:fixed;right:18px;bottom:88px;z-index:99999;background:#fb7299;color:#fff;border:none;
  border-radius:20px;padding:8px 14px;font-size:13px;cursor:grab;box-shadow:0 2px 8px rgba(0,0,0,.3);
  font-family:inherit;user-select:none;touch-action:none}
#bls-fab:hover{background:#fc8bab}
#bls-fab:active{cursor:grabbing}
#bls-panel{position:fixed;right:18px;bottom:130px;z-index:99999;width:420px;max-height:70vh;display:none;
  flex-direction:column;background:#fff;border-radius:10px;box-shadow:0 4px 24px rgba(0,0,0,.25);font-family:inherit;color:#18191c}
#bls-panel.open{display:flex}
#bls-head{display:flex;align-items:center;justify-content:space-between;padding:10px 14px;
  border-bottom:1px solid #e3e5e7;cursor:move}
#bls-head b{font-size:14px}
#bls-head .bls-x{cursor:pointer;border:none;background:none;font-size:16px;color:#61666d}
#bls-body{padding:12px 14px;overflow-y:auto;font-size:13px;line-height:1.6}
#bls-subtitle{color:#61666d;margin-bottom:8px;font-size:12px;word-break:break-all}
#bls-extra-label{display:block;font-size:12px;color:#61666d;margin-bottom:4px}
#bls-extra{width:100%;box-sizing:border-box;height:44px;min-height:44px;max-height:140px;padding:6px 8px;
  border:1px solid #e3e5e7;border-radius:6px;font-size:13px;font-family:inherit;resize:vertical;margin-bottom:10px}
#bls-extra:focus{outline:none;border-color:#fb7299}
#bls-run{width:100%;padding:8px 0;border:none;border-radius:6px;background:#fb7299;color:#fff;
  font-size:14px;cursor:pointer;margin-bottom:10px}
#bls-run:disabled{background:#f1f2f3;color:#9499a0;cursor:not-allowed}
#bls-log{background:#f6f7f8;border-radius:6px;padding:8px;margin-bottom:10px;max-height:120px;
  overflow-y:auto;font-size:12px;color:#61666d;display:none}
#bls-summary{white-space:pre-wrap;word-break:break-word;background:#fff8f9;border:1px solid #ffe4ea;
  border-radius:6px;padding:10px;max-height:300px;overflow-y:auto}
#bls-actions{display:flex;gap:8px;margin-top:10px}
#bls-actions button{flex:1;padding:6px 0;border:1px solid #e3e5e7;border-radius:6px;background:#fff;
  cursor:pointer;font-size:12px;color:#18191c}
#bls-actions button:hover{border-color:#fb7299;color:#fb7299}
#bls-mask{position:fixed;inset:0;z-index:99999;background:rgba(0,0,0,.4);display:none;
  align-items:center;justify-content:center}
#bls-mask.open{display:flex}
#bls-settings{width:460px;background:#fff;border-radius:10px;padding:18px;color:#18191c;font-family:inherit}
#bls-settings h3{margin:0 0 12px;font-size:15px}
#bls-settings label{display:block;font-size:12px;color:#61666d;margin:10px 0 4px}
#bls-settings input,#bls-settings select,#bls-settings textarea{width:100%;box-sizing:border-box;padding:6px 8px;
  border:1px solid #e3e5e7;border-radius:6px;font-size:13px;font-family:inherit;background:#fff}
#bls-settings textarea{height:90px;resize:vertical}
#bls-settings .row{display:flex;gap:10px}
#bls-settings .hint{font-size:11px;color:#9499a0;margin-top:2px}
#bls-settings .btns{display:flex;gap:10px;margin-top:14px;justify-content:flex-end}
#bls-settings button{padding:7px 18px;border-radius:6px;border:1px solid #e3e5e7;background:#fff;cursor:pointer}
#bls-settings button.primary{background:#fb7299;border-color:#fb7299;color:#fff}
#bls-histbtn{width:100%;padding:6px 0;border:1px solid #e3e5e7;border-radius:6px;background:#fff;
  color:#18191c;font-size:13px;cursor:pointer;margin-bottom:10px;font-family:inherit}
#bls-histbtn:hover{border-color:#fb7299;color:#fb7299}
#bls-hismask{position:fixed;inset:0;z-index:99999;background:rgba(0,0,0,.4);display:none;
  align-items:center;justify-content:center}
#bls-hismask.open{display:flex}
#bls-history{width:480px;max-width:92vw;max-height:70vh;display:flex;flex-direction:column;background:#fff;
  border-radius:10px;padding:14px;color:#18191c;font-family:inherit}
#bls-histhead{display:flex;align-items:center;justify-content:space-between;margin-bottom:8px}
#bls-histhead b{font-size:14px}
#bls-histhead .bls-x{cursor:pointer;border:none;background:none;font-size:13px;color:#61666d}
#bls-histhead .bls-x:hover{color:#fb7299}
#bls-histlist{overflow-y:auto;font-size:13px}
.bls-hist-item{padding:8px 10px;border:1px solid #e3e5e7;border-radius:6px;margin-bottom:6px;cursor:pointer}
.bls-hist-item:hover{border-color:#fb7299;background:#fff8f9}
.bls-hist-item .t{overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
.bls-hist-item .m{font-size:11px;color:#9499a0;margin-top:2px}
.bls-hist-empty{color:#9499a0;font-size:12px;text-align:center;padding:24px 0}
.bls-log-line.err{color:#f25d8e}
.bls-log-line.ok{color:#2ac864}
`;

  let panelBuilt = false;
  let state = { tracks: [], info: null, transcript: "", summary: "" };

  function buildUI() {
    if (panelBuilt) return;
    panelBuilt = true;
    const style = document.createElement("style");
    style.textContent = CSS;
    document.head.appendChild(style);

    const fab = document.createElement("button");
    fab.id = "bls-fab";
    fab.textContent = "📝 AI总结";

    const panel = document.createElement("div");
    panel.id = "bls-panel";
    panel.innerHTML = `
      <div id="bls-head"><b>BLSubSum · AI字幕总结</b><span><button id="bls-gear" class="bls-x" title="设置">⚙</button><button id="bls-close" class="bls-x">✕</button></span></div>
      <div id="bls-body">
        <div id="bls-subtitle">加载中…</div>
        <label id="bls-extra-label" for="bls-extra">补充提示词（可选，最高优先级）</label>
        <textarea id="bls-extra" placeholder="针对本视频的补充要求，例如：最后将视频中出现的单词罗列出来"></textarea>
        <button id="bls-run">获取字幕并总结</button>
        <button id="bls-histbtn">🕘 历史总结</button>
        <div id="bls-log"></div>
        <div id="bls-summary" style="display:none"></div>
        <div id="bls-actions" style="display:none">
          <button id="bls-copy">复制总结</button>
          <button id="bls-copy-t">复制讲稿</button>
          <button id="bls-dl">下载讲稿</button>
        </div>
      </div>`;
    document.body.appendChild(fab);
    document.body.appendChild(panel);

    // 恢复 FAB 上次拖动的位置
    const savedPos = cfg("fabPos");
    if (savedPos) {
      fab.style.right = Math.min(Math.max(savedPos.right || 0, 0), Math.max(window.innerWidth - fab.offsetWidth, 0)) + "px";
      fab.style.bottom = Math.min(Math.max(savedPos.bottom || 0, 0), Math.max(window.innerHeight - fab.offsetHeight, 0)) + "px";
    }
    makeFabDraggable(fab);

    $("#bls-close").addEventListener("click", () => $("#bls-panel").classList.remove("open"));
    $("#bls-gear").addEventListener("click", openSettings);
    $("#bls-run").addEventListener("click", runPipeline);
    $("#bls-copy").addEventListener("click", () => navigator.clipboard.writeText(state.summary).then(() => ($("#bls-copy").textContent = "已复制✓")));
    $("#bls-copy-t").addEventListener("click", () => navigator.clipboard.writeText(state.transcript).then(() => ($("#bls-copy-t").textContent = "已复制✓")));
    $("#bls-dl").addEventListener("click", downloadTranscript);
    $("#bls-histbtn").addEventListener("click", openHistory);

    // 设置弹层
    const mask = document.createElement("div");
    mask.id = "bls-mask";
    mask.innerHTML = `
      <div id="bls-settings">
        <h3>BLSubSum 设置</h3>
        <label>API 地址（OpenAI 兼容）</label>
        <input id="bls-cfg-api" type="text">
        <label>API Key</label>
        <input id="bls-cfg-key" type="password">
        <label>模型</label>
        <input id="bls-cfg-model" type="text">
        <label>总结提示词</label>
        <textarea id="bls-cfg-prompt"></textarea>
        <label>字幕轨道偏好</label>
        <select id="bls-cfg-track">
          <option value="auto">自动（AI中文 → AI英文 → 其他AI → 任意）</option>
          <option value="ai-zh">仅 AI 中文（无则自动回退）</option>
          <option value="ai-en">仅 AI 英文（无则自动回退）</option>
          <option value="ai">任意 AI 字幕（不分语言）</option>
          <option value="any">任意字幕（含UP主上传）</option>
        </select>
        <div class="row">
          <div style="flex:1"><label>分块大小（字符）</label><input id="bls-cfg-chunk" type="number"></div>
          <div style="flex:1"><label>段落合并间隔（秒）</label><input id="bls-cfg-gap" type="number" step="0.1"></div>
          <div style="flex:1"><label>历史总结条数</label><input id="bls-cfg-hist" type="number" min="0"></div>
        </div>
        <div class="hint">填入任意 OpenAI 兼容服务（DeepSeek / SiliconFlow / 中转等）。API Key 保存在本地脚本存储中。历史总结条数填 0 表示不保存。</div>
        <div class="btns"><button id="bls-cancel">取消</button><button id="bls-save" class="primary">保存</button></div>
      </div>`;
    document.body.appendChild(mask);
    $("#bls-cancel").addEventListener("click", () => mask.classList.remove("open"));
    $("#bls-save").addEventListener("click", () => {
      setCfg("apiBase", $("#bls-cfg-api").value.trim() || CFG_DEFAULTS.apiBase);
      setCfg("apiKey", $("#bls-cfg-key").value.trim());
      setCfg("model", $("#bls-cfg-model").value.trim() || CFG_DEFAULTS.model);
      setCfg("prompt", $("#bls-cfg-prompt").value.trim() || CFG_DEFAULTS.prompt);
      setCfg("trackPref", $("#bls-cfg-track").value || "auto");
      setCfg("chunkChars", Math.max(1000, parseInt($("#bls-cfg-chunk").value, 10) || CFG_DEFAULTS.chunkChars));
      setCfg("mergeGap", Math.max(0, parseFloat($("#bls-cfg-gap").value) || CFG_DEFAULTS.mergeGap));
      const histN = parseInt($("#bls-cfg-hist").value, 10);
      setCfg("historySize", isNaN(histN) ? CFG_DEFAULTS.historySize : Math.max(0, histN));
      mask.classList.remove("open");
      loadTracks();
    });

    // 历史总结弹层
    const hismask = document.createElement("div");
    hismask.id = "bls-hismask";
    hismask.innerHTML = `
      <div id="bls-history">
        <div id="bls-histhead"><b>🕘 历史总结</b><span><button id="bls-hist-clear" class="bls-x">清空</button><button id="bls-hist-close" class="bls-x">✕</button></span></div>
        <div id="bls-histlist"></div>
      </div>`;
    document.body.appendChild(hismask);
    $("#bls-hist-close").addEventListener("click", () => $("#bls-hismask").classList.remove("open"));
    $("#bls-hist-clear").addEventListener("click", () => {
      if (!confirm("确定清空全部历史总结？")) return;
      setCfg("history", []);
      openHistory();
    });

    makeDraggable(panel, $("#bls-head"));
  }

  function makeDraggable(el, handle) {
    let sx, sy, ox, oy, dragging = false;
    handle.addEventListener("mousedown", (e) => {
      dragging = true;
      el.style.top = "auto"; // 面板可能被 placePanelNearFab 以 top 定位，拖动时改回 bottom
      sx = e.clientX; sy = e.clientY;
      ox = el.getBoundingClientRect().right - window.innerWidth; // 以 right 定位
      oy = window.innerHeight - el.getBoundingClientRect().bottom;
      e.preventDefault();
    });
    document.addEventListener("mousemove", (e) => {
      if (!dragging) return;
      const right = Math.min(Math.max(window.innerWidth - e.clientX - ox, 0), window.innerWidth - 100);
      const bottom = Math.min(Math.max(window.innerHeight - e.clientY - oy, 0), window.innerHeight - 60);
      el.style.right = right + "px";
      el.style.bottom = bottom + "px";
    });
    document.addEventListener("mouseup", () => (dragging = false));
  }

  // FAB 拖动：位移 ≥5px 视为拖动（并记忆位置），否则视为点击
  function makeFabDraggable(fab) {
    let pid = null, sx, sy, sr, sb, moved = false;
    fab.addEventListener("pointerdown", (e) => {
      if (pid !== null) return;
      pid = e.pointerId;
      fab.setPointerCapture(pid);
      sx = e.clientX;
      sy = e.clientY;
      const r = fab.getBoundingClientRect();
      sr = window.innerWidth - r.right;
      sb = window.innerHeight - r.bottom;
      moved = false;
    });
    fab.addEventListener("pointermove", (e) => {
      if (pid === null || e.pointerId !== pid) return;
      const dx = e.clientX - sx, dy = e.clientY - sy;
      if (!moved && Math.hypot(dx, dy) < 5) return;
      moved = true;
      const right = Math.min(Math.max(sr - dx, 0), window.innerWidth - fab.offsetWidth);
      const bottom = Math.min(Math.max(sb - dy, 0), window.innerHeight - fab.offsetHeight);
      fab.style.right = right + "px";
      fab.style.bottom = bottom + "px";
    });
    const finish = (e) => {
      if (pid === null || e.pointerId !== pid) return;
      pid = null;
      if (moved) {
        setCfg("fabPos", { right: parseInt(fab.style.right, 10) || 0, bottom: parseInt(fab.style.bottom, 10) || 0 });
      } else {
        togglePanel();
      }
    };
    fab.addEventListener("pointerup", finish);
    fab.addEventListener("pointercancel", () => (pid = null));
  }

  function togglePanel() {
    const panel = $("#bls-panel");
    panel.classList.toggle("open");
    if (panel.classList.contains("open")) {
      placePanelNearFab();
      if (!state.tracks.length) loadTracks();
    }
  }

  // 面板打开时贴着 FAB 摆放（优先上方，放不下则下方）
  function placePanelNearFab() {
    const fab = $("#bls-fab");
    const panel = $("#bls-panel");
    if (!fab || !panel) return;
    const fr = fab.getBoundingClientRect();
    panel.style.right = Math.min(Math.max(window.innerWidth - fr.right, 0), window.innerWidth - panel.offsetWidth) + "px";
    if (fr.top - panel.offsetHeight - 16 > 0) {
      panel.style.top = "auto";
      panel.style.bottom = window.innerHeight - fr.top + 8 + "px";
    } else {
      panel.style.bottom = "auto";
      panel.style.top = Math.min(fr.bottom + 8, Math.max(window.innerHeight - panel.offsetHeight - 10, 0)) + "px";
    }
  }

  // ---------------- 历史总结 ----------------

  const historyKey = (bvid, p) => bvid + "#P" + p;

  function loadHistory() {
    try {
      const list = GM_getValue("blsubsum.history", []);
      return Array.isArray(list) ? list : [];
    } catch (e) {
      return [];
    }
  }

  function saveHistory(entry) {
    const max = Math.max(0, parseInt(cfg("historySize"), 10) || 0);
    if (!max) return;
    const list = loadHistory().filter((it) => it.key !== entry.key);
    list.unshift(entry);
    setCfg("history", list.slice(0, max));
  }

  const findHistory = (bvid, p) => loadHistory().find((it) => it.key === historyKey(bvid, p)) || null;

  function showSummaryBox(text) {
    const box = $("#bls-summary");
    box.textContent = text;
    box.style.display = "block";
    $("#bls-actions").style.display = "flex";
    $("#bls-copy").textContent = "复制总结";
    $("#bls-copy-t").textContent = "复制讲稿";
  }

  // 面板打开/切换分P后，若当前视频（BV+分P）有历史总结则自动恢复
  function tryRestoreSummary() {
    if (!state.info) return false;
    const hit = findHistory(state.info.bvid, state.info.p);
    if (!hit) return false;
    state.summary = hit.summary || "";
    state.transcript = hit.transcript || "";
    showSummaryBox(state.summary);
    const logBox = $("#bls-log");
    logBox.innerHTML = "";
    logBox.style.display = "block";
    log(`🕘 已恢复历史总结（保存于 ${new Date(hit.ts).toLocaleString()}），可复制/下载，也可重新总结`, "ok");
    return true;
  }

  function openHistory() {
    const list = loadHistory();
    const box = $("#bls-histlist");
    box.innerHTML = "";
    if (!list.length) {
      box.innerHTML = `<div class="bls-hist-empty">暂无历史总结<br>完成一次总结后会自动保存到这里</div>`;
    } else {
      for (const it of list) {
        const item = document.createElement("div");
        item.className = "bls-hist-item";
        const t = document.createElement("div");
        t.className = "t";
        t.textContent = `${it.title}${it.pagesTotal > 1 ? ` (P${it.p}${it.part ? " " + it.part : ""})` : ""}`;
        const m = document.createElement("div");
        m.className = "m";
        m.textContent = `${it.bvid} · ${it.up || "?"} · ${new Date(it.ts).toLocaleString()} · ${(it.summary || "").length} 字`;
        item.append(t, m);
        item.addEventListener("click", () => applyHistoryItem(it));
        box.appendChild(item);
      }
    }
    $("#bls-hismask").classList.add("open");
  }

  function applyHistoryItem(it) {
    $("#bls-hismask").classList.remove("open");
    const curBvid = getBvid();
    const curP = parseInt(new URLSearchParams(location.search).get("p") || "1", 10) || 1;
    if (curBvid !== it.bvid || curP !== it.p) {
      // 其他视频/分P：直接跳转，打开面板后会自动恢复
      location.href = `https://www.bilibili.com/video/${it.bvid}${it.p > 1 ? "?p=" + it.p : ""}`;
      return;
    }
    state.summary = it.summary || "";
    state.transcript = it.transcript || "";
    if (!state.info) {
      state.info = { bvid: it.bvid, title: it.title, up: it.up, p: it.p, pagesTotal: it.pagesTotal || 1, part: it.part || "" };
      const sub = $("#bls-subtitle");
      if (sub) sub.textContent = `${it.title}${it.pagesTotal > 1 ? ` (P${it.p} ${it.part})` : ""} · UP: ${it.up}`;
    }
    showSummaryBox(state.summary);
    const logBox = $("#bls-log");
    logBox.innerHTML = "";
    logBox.style.display = "block";
    log(`🕘 已载入历史总结（${new Date(it.ts).toLocaleString()}）`, "ok");
  }

  function openSettings() {
    $("#bls-cfg-api").value = cfg("apiBase");
    $("#bls-cfg-key").value = cfg("apiKey");
    $("#bls-cfg-model").value = cfg("model");
    $("#bls-cfg-prompt").value = cfg("prompt");
    $("#bls-cfg-track").value = cfg("trackPref");
    $("#bls-cfg-chunk").value = cfg("chunkChars");
    $("#bls-cfg-gap").value = cfg("mergeGap");
    $("#bls-cfg-hist").value = cfg("historySize");
    $("#bls-mask").classList.add("open");
  }

  // ---------------- 主流程 ----------------

  async function loadTracks() {
    const sub = $("#bls-subtitle");
    $("#bls-log").style.display = "none";
    $("#bls-summary").style.display = "none";
    $("#bls-actions").style.display = "none";
    sub.textContent = "加载中…";
    try {
      const info = await resolveVideoInfo();
      state.info = info;
      const title = `${info.title}${info.pagesTotal > 1 ? ` (P${info.p} ${info.part})` : ""}`;
      sub.textContent = `${title} · UP: ${info.up}`;
      tryRestoreSummary();
      const tracks = await listSubtitleTracks(info.bvid, info.cid);
      state.tracks = tracks;
      if (!tracks.length) {
        sub.textContent = title + "\n⚠️ 未找到任何字幕轨道（该视频可能未生成AI字幕，或未登录）";
        return;
      }
      sub.textContent += ` · 字幕轨道: ${tracks
        .map((t) => `${t.lan_doc || t.lan}${t.lan.startsWith("ai-") ? "(AI)" : ""}`)
        .join("、")}`;
    } catch (e) {
      sub.textContent = "❌ " + e.message;
    }
  }

  async function runPipeline() {
    const run = $("#bls-run");
    run.disabled = true;
    $("#bls-log").innerHTML = "";
    $("#bls-log").style.display = "block";
    $("#bls-summary").style.display = "none";
    $("#bls-actions").style.display = "none";
    try {
      if (!state.tracks.length) {
        log("字幕轨道未加载，请先等轨道列表加载完成");
        return;
      }
      if (!state.info) {
        log("解析视频信息…");
        state.info = await resolveVideoInfo();
      }
      const track = pickTrackByPref(state.tracks, cfg("trackPref"));
      log(`使用字幕轨道 ${track.lan}（${track.lan_doc || ""}）…`);
      const body = await fetchSubtitleBody(track);
      log(`共 ${body.length} 条字幕，合并段落…`);
      state.transcript = transcriptFromBody(body, cfg("mergeGap"));
      log(`讲稿 ${state.transcript.length} 字，开始总结…`);
      const extra = $("#bls-extra").value.trim();
      if (extra) log(`已附加补充提示词（最高优先级，${extra.length} 字）`);
      state.summary = await summarize(state.transcript, extra, (m) => log(m));
      log("✅ 总结完成", "ok");
      showSummaryBox(state.summary);
      saveHistory({
        key: historyKey(state.info.bvid, state.info.p),
        bvid: state.info.bvid,
        p: state.info.p,
        title: state.info.title,
        up: state.info.up,
        part: state.info.part,
        pagesTotal: state.info.pagesTotal,
        lan: track.lan,
        model: cfg("model"),
        summary: state.summary,
        transcript: state.transcript,
        ts: Date.now(),
      });
      log("🕘 已存入历史总结", "ok");
    } catch (e) {
      log("❌ " + e.message, "err");
    } finally {
      run.disabled = false;
    }
  }

  function downloadTranscript() {
    if (!state.info) return;
    const safe = state.info.title.replace(/[\\/:*?"<>|]/g, "_").slice(0, 60);
    const blob = new Blob(
      [`【${state.info.title}】\nUP: ${state.info.up}\n\n===== 总结 =====\n\n${state.summary}\n\n===== 讲稿 =====\n\n${state.transcript}\n`],
      { type: "text/plain;charset=utf-8" }
    );
    const a = document.createElement("a");
    a.href = URL.createObjectURL(blob);
    a.download = `${safe}_P${state.info.p}_BLSubSum.txt`;
    a.click();
    URL.revokeObjectURL(a.href);
  }

  // ---------------- SPA 路由感知 ----------------

  // B站视频页是 SPA，切换视频时重置状态重新加载轨道
  let lastUrl = location.href;
  setInterval(() => {
    if (location.href === lastUrl) return;
    lastUrl = location.href;
    state = { tracks: [], info: null, transcript: "", summary: "" };
    if ($("#bls-panel")?.classList.contains("open")) loadTracks();
  }, 800);

  // ---------------- 启动 ----------------

  function boot() {
    if (!getBvid()) return;
    buildUI();
  }

  if (document.readyState === "loading") {
    document.addEventListener("DOMContentLoaded", boot);
  } else {
    boot();
  }
})();