// Router
setupRouter() {
    this.router.route('/signup')
    /* POST /users/signup req.body = {email, password} */
    .post(this.userController.registerUser.bind(this.userController))

    this.router.route('/signin')
    /* POST /users/signin req.body = {email, password} */
    .post(this.userController.loginUser.bind(this.userController))
}

// Controller
registerUser(req, res, next) {
    const { email, password } = req.body
    this.userService.registerUser(email, password)
    .then(newUser => res.status(201).json({ newUser }))
    .catch(error => res.status(422).json({ error }))
}

// Service
registerUser(email, password) {
    return this.userResource.registerUser(email, password)
    .then(res => res)
}

// Resource
async registerUser(email, password) {
    const possibleUser = await User.findOne({ email })
    if (possibleUser) throw new Error('Email already taken!')

    const newUser = new User({
      _id: new mongoose.Types.ObjectId(),
      email,
      password
    })

    const salt = await encrypt.genSalt(10)
    const hashedPassword = await encrypt.genHash(newUser.password, salt)

    newUser.password = hashedPassword
    return newUser.save()
}