/**
 * Pick the first LIVE track of a kind across a set of streams — used to find
 * the audio/video track the session is currently capturing with (webcam
 * observer, or an in-flight clip recording), so the checkpoint can read its
 * liveness. Ended tracks are ignored: a finished clip isn't a mic/camera
 * failure, just a finished clip.
 */
export function pickLiveTrack(
  kind: "audio" | "video",
  streams: Array<MediaStream | null | undefined>,
): MediaStreamTrack | null {
  for (const stream of streams) {
    if (!stream) continue;
    const tracks = kind === "audio" ? stream.getAudioTracks() : stream.getVideoTracks();
    for (const track of tracks) {
      if (track.readyState === "live") return track;
    }
  }
  return null;
}