%% @doc: Find a cell to serve user, and try to spawn new if that's not found
find_cell(UserId, WorldId) ->
  case pick_cell(UserId, WorldId, 0) of
    {ok, Pid} -> {ok, Pid};
    {error, _} ->
      try
        gen_server:cast(?SERVER, {spawn_cell, UserId, WorldId}),
        timer:sleep(?WAIT_TIMEOUT),
        pick_cell(UserId, WorldId, 0)
      catch
        exit:{timeout, _} -> {error, not_found}
      end
  end.