/** Record the rendered camera path, never an AI approximation. */
export async function recordDirectorVideo({
  canvas,
  duration,
  render,
  signal,
  onProgress,
}: {
  canvas: HTMLCanvasElement;
  duration: number;
  render: (time: number) => void;
  signal: AbortSignal;
  onProgress?: (time: number) => void;
}): Promise<Blob> {
  const mimeType = [
    "video/mp4",
    "video/webm;codecs=vp9",
    "video/webm;codecs=vp8",
    "video/webm",
  ].find((t) => typeof MediaRecorder !== "undefined" && MediaRecorder.isTypeSupported(t));
  if (!mimeType || !canvas.captureStream)
    throw Error("当前浏览器不支持视频录制，请更换支持视频录制的浏览器");
  if (signal.aborted || document.hidden) throw Error("请保持当前页面可见后导出");
  // Let WebGL present the first frame before opening the encoder stream.
  render(0);
  await new Promise<void>((resolve, reject) => {
    let frame = 0;
    const finish = (error?: Error) => {
      cancelAnimationFrame(frame);
      clearTimeout(timeout);
      signal.removeEventListener("abort", cancel);
      document.removeEventListener("visibilitychange", hidden);
      if (error) reject(error);
      else resolve();
    };
    const cancel = () => finish(Error("已取消轨迹视频导出"));
    const hidden = () => {
      if (document.hidden) finish(Error("导出时切换了页面，请回到当前页面重新导出"));
    };
    const timeout = setTimeout(() => finish(Error("画面准备超时，请保持页面可见后重试")), 2000);
    signal.addEventListener("abort", cancel, { once: true });
    document.addEventListener("visibilitychange", hidden);
    frame = requestAnimationFrame(() => {
      frame = requestAnimationFrame(() => finish());
    });
  });
  if (signal.aborted || document.hidden) throw Error("请保持当前页面可见后导出");
  const stream = canvas.captureStream(30);
  try {
    return await new Promise<Blob>((resolve, reject) => {
      const recorder = new MediaRecorder(stream, {
        mimeType,
        videoBitsPerSecond: 6_000_000,
      });
      const chunks: Blob[] = [];
      let frame = 0,
        started = 0,
        failure: Error | undefined,
        finished = false;
      const cleanup = () => {
        cancelAnimationFrame(frame);
        clearTimeout(timeout);
        signal.removeEventListener("abort", cancel);
        document.removeEventListener("visibilitychange", visibility);
      };
      const stop = (error?: Error) => {
        if (finished) return;
        finished = true;
        failure = error;
        cleanup();
        if (recorder.state !== "inactive") recorder.stop();
        else reject(error || Error("视频录制未启动"));
      };
      const cancel = () => stop(Error("已取消轨迹视频导出"));
      const visibility = () => {
        if (document.hidden) stop(Error("导出时切换了页面，请回到当前页面重新导出"));
      };
      const timeout = setTimeout(
        () => stop(Error("轨迹导出超时，请重试")),
        duration * 1000 + 15000,
      );
      recorder.ondataavailable = (e) => {
        if (e.data.size) chunks.push(e.data);
      };
      recorder.onerror = () => stop(Error("浏览器视频编码失败"));
      recorder.onstop = () => {
        cleanup();
        if (failure) reject(failure);
        else if (!chunks.length) reject(Error("未生成有效视频"));
        else resolve(new Blob(chunks, { type: recorder.mimeType }));
      };
      signal.addEventListener("abort", cancel, { once: true });
      document.addEventListener("visibilitychange", visibility);
      const tick = (now: number) => {
        if (finished) return;
        if (!started) started = now;
        const t = Math.min(duration, (now - started) / 1000);
        try {
          render(t);
          onProgress?.(t);
        } catch (e) {
          stop(e instanceof Error ? e : Error("轨迹渲染失败"));
          return;
        }
        // MediaRecorder consumes the canvas asynchronously. Stopping in the rendering
        // callback drops the final pose; allow two presentation frames to flush it.
        if (t >= duration)
          frame = requestAnimationFrame(() => {
            frame = requestAnimationFrame(() => stop());
          });
        else frame = requestAnimationFrame(tick);
      };
      try {
        render(0);
        recorder.start(100);
        frame = requestAnimationFrame(tick);
      } catch (e) {
        stop(e instanceof Error ? e : Error("视频编码失败"));
      }
    });
  } finally {
    stream.getTracks().forEach((t) => t.stop());
  }
}