gistfile1.js

exports.getDialogs = function () {
  return function (req, res) {
    var dialogs = [];
    _getUsersInDialogs(req.user._id, function (err, users) {
      users.forEach(function (user, key, all) {
        _getCountAndLastMessageInDialog(req.user._id, user, function (err, lastMessage, unread) {
          dialogs.push({user: user, last_message: lastMessage, unread:unread});
          if (key === all.length - 1) {
            res.json(200, {
              data: {
                dialogs: dialogs
              }
            });
          }
        });
      });
    });
  };
};


var _getUsersInDialogs = function (user, cb) {

  var authors, users;

  var next = new Countdown(2, function () {
    users = users
      .concat(authors)
      .filter(function (value, index, self) {
        return self.indexOf(value) === index;
      });
    return cb(null, users);
  });

  Message
    .distinct('author', {user: user}, function (err, _authors) {
      authors = _authors;
      next();
    });

  Message
    .distinct('user', {author: user}, function (err, _users) {
      users = _users;
      next();
    });

};


var _getCountAndLastMessageInDialog = function (requser, user, cb) {

  var lastMessage, unread;

  var next = new Countdown(2, function () {
    return cb(null, lastMessage, unread);
  });

  Message
    .findOne(null)
    .or([{user: requser, author: user},{user: user, author: requser}])
    .sort('-create_at')
    .exec(function (err, _lastMessage) {
      lastMessage = _lastMessage;
      next();
    });

  Message
    .find({user: requser, author: user, unread: true})
    .count()
    .exec(function (err, _unread) {
      unread = _unread;
      next();
    });

};