// requires Msg concept

class DiscordScanner {
  MessageChannel channel;
  MessageHistory history;
  int scanned;
  bool incremental, postResult = true;
  Runnable whenDone;

  run {
    if (history == null) history = channel.getHistory();
    history.retrievePast(100).queue(msgs -> {
      temp enter();
      print("Got msgs: " + l(msgs));
      if (empty(msgs)) {
        if (postResult)
          postInChannel(channel, "Done scanning " + discordChannelRef(channel.getIdLong()) + " (" + nMessages(scanned) + ")");
        callF(whenDone);
        ret;
      }
      scanned += l(msgs);
      if (storeMsgs(msgs) && incremental) {
        if (postResult)
          postInChannel(channel, "Stopping incremental scan of " + discordChannelRef(channel.getIdLong()) + " after " + nMessages(scanned));
        callF(whenDone);
        ret;
      }
      run();
    }, onQueueError);
  }
}

// returns true if seen
Pair<Msg, Bool> storeMsg(Message msg) {
  if (msg == null) null;
  Msg m, bool isNew = unpair uniq2(Msg, msgID := msg.getIdLong());
  cset(m,
    channelID := msg.getTextChannel().getIdLong(),
    userID := msg.getAuthor().getIdLong(),
    date := msg.getCreationTime().toEpochSecond(),
    edited := msg.isEdited() ? msg.getEditedTime().toEpochSecond() : 0,
    text := msg.getContentRaw());
  ret pair(m, !isNew);
}

// returns true if any seen
bool storeMsgs(L<Message> l) {
  bool anySeen;
  for (Message msg : l) {
    if (pairB(storeMsg(msg))) set anySeen;
  }
  ret anySeen;
}