Minor UserAuth Class Changes

class UserAuth implements BadNaming {

    const PASSWORD_ALGO = \PASSWORD_DEFAULT; // these should be somewhere more sensible
    const PASSWORD_OPTIONS = [];

    const AUTHENTICATE_SUCCESS = 0;
    const AUTHENTICATE_INVALID_USER = 1;
    const AUTHENTICATE_WRONG_PASSWORD = 2;

    public function authenticate($userID, $inputPassword) {
        if (!$this->userMapper->contactExists('email', $userID)) {
            return self::AUTHENTICATE_INVALID_USER;
        }

        $hashedPassword = $this->userMapper->getPasswordByID('email', $userID);

        if (!\password_verify($inputPassword, $hashedPassword)) {
            return self::AUTHENTICATE_WRONG_PASSWORD;
        }

        if (\password_needs_rehash($hashedPassword, self::PASSWORD_ALGO, self::PASSWORD_OPTIONS)) {
            $this->userMapper->updatePassword('email', $userID, $inputPassword);
        }

        return self::AUTHENTICATE_SUCCESS;
    }