sclass YTChatMessage {
  S text, publishedAt, authorChannelId, authorDisplayName;
}

sclass YTChatMessages {
  S nextPageToken;
  int pollingIntervalMillis;
  L<YTChatMessage> messages;
}

static YTChatMessages youTubeGetChatMessages(S liveStreamID) {
  ret youTubeGetChatMessages(liveStreamID, null);
}

static YTChatMessages youTubeGetChatMessages(S liveStreamID, S pageToken) {
  S page = loadPageWithParamsSilently("https://www.googleapis.com/youtube/v3/liveChat/messages",
    liveChatId := liveStreamID,
    part := "id,snippet,authorDetails",
    +pageToken,
    key := youTubeDataAPIKey());
  Map map = jsonDecodeMap(page);
  //printStruct(map);
  L<Map> items = cast map.get('items);
  ret nu(YTChatMessages,
    nextPageToken := getString(map, 'nextPageToken),
    pollingIntervalMillis := getInt(map, 'pollingIntervalMillis),
    messages := map(items, func(Map item) -> YTChatMessage {
      Map snippet = (Map) item.get('snippet);
      Map textMessageDetails = (Map) _get(snippet, 'textMessageDetails);
      Map authorDetails = (Map) _get(item, 'authorDetails);
      ret nu(YTChatMessage,
        text := getString(textMessageDetails, 'messageText),
        publishedAt := getString(snippet, 'publishedAt),
        authorChannelId := getString(snippet, 'authorChannelId),
        authorDisplayName := getString(authorDetails, 'displayName));
    }));
}

Began life as a copy of #1009898