Parse playlist and use it to figure out the album

lib/services/ytmusic/index.js

@@ -190,14 +190,54 @@ async function lookupAlbum(id) {
     artist: {
       name: artists.join(", "),
     },
+    playlistId: album_data.audioPlaylistId
   });
 }
 
+async function lookupPlaylist(id) {
+  let request_body = {enablePersistentPlaylistPanel: true, isAudioOnly: true, playlistId: id, ...standard_body}
+  const { body } = await request.post("https://music.youtube.com/youtubei/v1/next")
+    .set(standard_headers)
+    .query(standard_params)
+    .send(request_body)
+
+  // The playlist object is rather complex, but here's what I'm doing: I'll parse the very minimum to get to the first track.
+  // At that point, I'm going to check the id of the album in that track. And make a lookup on it. If the album looked up
+  // has the same playlist id as the one I'm looking up, it means it's an album and not a playlist and we're good.
+  const watchNextRenderer = body.contents.singleColumnMusicWatchNextResultsRenderer.tabbedRenderer.watchNextTabbedResultsRenderer
+  const firstTrack = watchNextRenderer.tabs[0].tabRenderer.content.musicQueueRenderer.content.playlistPanelRenderer.contents[0]
+  const runs = firstTrack.playlistPanelVideoRenderer.longBylineText.runs
+  const reverse_last_artist_idx = runs.reverse().findIndex((entry) => {
+    if (entry.navigationEndpoint === undefined) {
+      return false
+    }
+    return entry.navigationEndpoint.browseEndpoint.browseId.startsWith("UC") ||
+      entry.navigationEndpoint.browseEndpoint.browseId.startsWith("FEmusic_library_privately_owned_artist")
+  });
+  if (reverse_last_artist_idx == -1) {
+    debug("Could not find an artist. Implement extra logic from ytmusicapi!");
+    throw new Error();
+  }
+  const last_artist_idx = runs.length - reverse_last_artist_idx - 1;
+  if (runs.length - last_artist_idx != 5) {
+    debug("No album found, can't find this.");
+    throw new Error();
+  }
+  const albumId = runs[last_artist_idx + 2].navigationEndpoint.browseEndpoint.browseId
+  const possibleAlbum = await lookupAlbum(albumId)
+  if (possibleAlbum.playlistId = id) {
+    return possibleAlbum;
+  }
+  throw new Error();
+}
+
 export async function lookupId(id, type) {
   if (type == 'track') {
     return lookupTrack(id);
   } else if (type == 'album') {
     return lookupAlbum(id);
+  } else if (type == 'playlist') {
+    return lookupPlaylist(id);
   }
   return { service: 'ytmusic', id };
 }
@@ -214,9 +254,7 @@ export function parseUrl(url) {
   } else if (match = parsed.path.match(/^\/browse\/([A-Za-z0-9_]+)/)) {
     return lookupId(match[1], 'album');
   } else if (match = parsed.path.match(/^\/playlist/) && list_id !== undefined) {
-    if (list_id == 'OLAK5uy_lx9K5RpiBEwd3E4C1GKqY7e06qTlwydvs') { // TODO: Parse playlist correctly
+    return lookupId(list_id, 'playlist');
-      return lookupId('MPREb_9C36yscfgmJ', 'album');
-    }
   }
   throw new Error();
 }