// Extracts the current track from a YouTube Music page. `doc` and `nav` are
// injected so this stays testable without a browser.

function largestArtwork(artwork) {
  if (!artwork || !artwork.length) return null;
  const area = (a) => {
    const [w, h] = String(a.sizes || '').split('x').map(Number);
    return (w || 0) * (h || 0);
  };
  return artwork.reduce((best, a) => (area(a) > area(best) ? a : best)).src || null;
}

// Preferred source: YT Music publishes the track via the Media Session API
// even when its player-bar markup changes.
function fromMediaSession(nav) {
  const session = nav && nav.mediaSession;
  const meta = session && session.metadata;
  if (!meta || !meta.title) return null;
  return {
    title: meta.title,
    artist: meta.artist || null,
    albumArt: largestArtwork(meta.artwork),
    isPlaying: session.playbackState === 'playing',
  };
}

// Fallback for older YT Music layouts that still render ytmusic-player-bar.
function fromPlayerBar(doc) {
  const titleEl =
    doc.querySelector('ytmusic-player-bar .title') ||
    doc.querySelector('.ytmusic-player-bar .title');
  const title = titleEl ? titleEl.textContent.trim() : null;
  if (!title) return null;

  const bylineEl =
    doc.querySelector('ytmusic-player-bar .byline') ||
    doc.querySelector('.ytmusic-player-bar .byline');
  const artImg =
    doc.querySelector('ytmusic-player-bar .middle-controls .thumbnail-image-wrapper img') ||
    doc.querySelector('ytmusic-player-bar .image img') ||
    doc.querySelector('ytmusic-player-bar img.image');

  // The button's title is the action it will perform: "Pause" while playing.
  const btn = doc.querySelector('#play-pause-button');
  let isPlaying = false;
  if (btn) {
    const label = (btn.getAttribute('title') || btn.getAttribute('aria-label') || '').toLowerCase();
    isPlaying = label.includes('pause');
  }

  return {
    title,
    artist: bylineEl ? bylineEl.textContent.trim() : null,
    albumArt: artImg ? artImg.src : null,
    isPlaying,
  };
}

function scrapeNowPlaying(doc, nav) {
  return fromMediaSession(nav) || fromPlayerBar(doc);
}

module.exports = { scrapeNowPlaying };