router.post('/', (req, res, next) => {
  const requiredFields = ['username', 'password', 'firstName', 'lastName'];
  const missingField = requiredFields.find(field => !(field in req.body));

    if (missingField) {
        return res.status(422).json({
            code: 422,
            reason: 'ValidationError',
            message: 'Missing field',
            location: missingField
        });
    }

    let { username, password, firstName, lastName } = req.body;

    return User.find({ username })
        .count()
        .then(count => {
            if (count > 0) {
                return Promise.reject({
                    code: 422,
                    reason: 'ValidationError',
                    message: 'Username already taken',
                    location: 'username'
                });
            }
        })
        .then(() => Question.find())
        .then(questions => {
            let hash = User.hashPassword(password);
            let userQuestions = questions.map((question, index) => {
                return {
                    question: question.question,
                    answer: question.answer,
                    next: index === questions.length - 1 ? null : index + 1,
                    mValue: 1,
                    numCorrect: 0,
                    numAttempts: 0
                }
            });

            console.log(userQuestions);

            return User.create({
                questions: userQuestions,
                firstName,
                lastName,
                username,
                password: hash
            });
        })
        .then(user => res.status(201).json(user))
        .catch(err => {
            if (err.reason === 'ValidationError') {
                return res.status(err.code).json(err);
            }
            console.log(err);
            res.status(500).json({ code: 500, message: err });
        });
});