text: var recent_senders = (function () {
  
  var exports = {};
  
  var topic_senders = new Dict(); // key is stream-id, value is Dict
  var stream_senders = new Dict(); // key is stream-id, value is Dict
  
  exports.process_message_for_senders = function (message) {
      var stream_id = message.stream_id.toString();
      var topic = util.get_message_topic(message);
  
      // Process most recent sender to topic
      var topic_dict = topic_senders.get(stream_id) || new Dict({fold_case: true});
      var sender_message_ids = topic_dict.get(topic) || new Dict();
      var old_message_id = sender_message_ids.get(message.sender_id);
  
      if (old_message_id === undefined || old_message_id < message.id) {
          sender_message_ids.set(message.sender_id, message.id);
      }
  
      topic_dict.set(topic, sender_message_ids);
      topic_senders.set(stream_id, topic_dict);
  
      // Process most recent sender to whole stream
      sender_message_ids = stream_senders.get(stream_id) || new Dict();
      old_message_id = sender_message_ids.get(message.sender_id);
  
      if (old_message_id === undefined || old_message_id < message.id) {
          sender_message_ids.set(message.sender_id, message.id);
      }
  
      stream_senders.set(stream_id, sender_message_ids);
  };
  
  exports.compare_by_recency = function (user_a, user_b, stream_id, topic) {
      stream_id = stream_id.toString();
  
      var a_message_id;
      var b_message_id;
  
      var topic_dict = topic_senders.get(stream_id);
      if (topic !== undefined && topic_dict !== undefined) {
          var sender_message_ids = topic_dict.get(topic);
          if (sender_message_ids !== undefined) {
              b_message_id = sender_message_ids.get(user_b.user_id) || Number.NEGATIVE_INFINITY;
              a_message_id = sender_message_ids.get(user_a.user_id) || Number.NEGATIVE_INFINITY;
  
              if (a_message_id !== b_message_id) {
                  return b_message_id - a_message_id;
              }
          }
      }
  
      // Check recency for whole stream as tiebreaker
      var stream_dict = stream_senders.get(stream_id);
      if (stream_dict !== undefined) {
          b_message_id = stream_dict.get(user_b.user_id) || Number.NEGATIVE_INFINITY;
          a_message_id = stream_dict.get(user_a.user_id) || Number.NEGATIVE_INFINITY;
  
          if (a_message_id !== b_message_id) {
              return b_message_id - a_message_id;
          }
      }
  
      return 0;
  };
  
  return exports;
  }());
  
  if (typeof module !== 'undefined') {
      module.exports = recent_senders;
  }
  window.recent_senders = recent_senders;
  