return User.find({ username })
    .count()
    .then(count => {
      if (count > 0) {
        return Promise.reject({
          code: 422,
          reason: 'ValidationError',
          message: 'Username already taken',
          location: 'username'
        });
      }
      return User.hashPassword(password);
    })
    .then((digest) => {
      const newUser = { username, password: digest, currentCash, careerCash, manualClicks, clickValue, assets, upgrades, seenMessage };
      return User.create(newUser);
    })
    .then(result => {
      return res.status(201).location(`/api/users/${result.username}`).json(result);
    })
    .catch(err => {
      if (err.code === 11000) {
        err = new Error('The username already exists');
        err.status = 400;
      }
      next(err);
    });