(defvar my-subed-skim-msecs 1000 "Number of milliseconds to play when skimming.")
(defun my-subed-skim-starts ()
  (interactive)
  (subed-mpv-unpause)
  (subed-disable-loop-over-current-subtitle)
  (catch 'done
    (while (not (eobp))
      (subed-mpv-jump-to-current-subtitle)
      (let ((ch
             (read-char "(q)uit? " nil (/ my-subed-skim-msecs 1000.0))))
        (when ch
          (throw 'done t)))
      (subed-forward-subtitle-time-start)
      (when (and subed-waveform-minor-mode
                 (not subed-waveform-show-all))
        (subed-waveform-refresh))
      (recenter)))
  (subed-mpv-pause))

function getVisibleVideo() {
  const videos = document.querySelectorAll('video');
  for (const video of videos) {
    const rect = video.getBoundingClientRect();
    if (
      rect.top >= 0 &&
      rect.left >= 0 &&
      rect.bottom <= (window.innerHeight || document.documentElement.clientHeight) &&
      rect.right <= (window.innerWidth || document.documentElement.clientWidth)
    ) {
      return video;
    }
  }
  return null;
}

async function skimVideo(video=getVisibleVideo(), msecs=1000) {
  // Get the first text track (assumed to be captions/subtitles)
  const textTrack = video.textTracks[0];
  if (!textTrack) return;
  const remaining = [...textTrack.cues].filter((cue) => cue.endTime >= video.currentTime);
  video.play();
  // Play the first 1 second of each visible subtitle
  for (let i = 0; i < remaining.length && !video.paused; i++) {
    video.currentTime = remaining[i].startTime;
    await new Promise((resolve) => setTimeout(resolve, msecs));
  }
}

function handleSkimButton(event) {
   const vid = event.target.closest('.vid').querySelector('video');
   skimVideo(vid);
 }

document.querySelectorAll('video').forEach((vid) => {
   const div = document.createElement('div');
   const skim = document.createElement('button');
   skim.textContent = 'Skim';
   div.appendChild(skim);
   vid.parentNode.insertBefore(div, vid.nextSibling);
   skim.addEventListener('click', handleSkimButton);
});