Foreign App in Subfolder / SSO Solution

PHP Code:
<?php
/**
Copyright 2011-2014 Nick Korbel
Copyright 2012-2014 Alois Schloegl

This file is part of Booked Scheduler.

Booked Scheduler is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

Booked Scheduler is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Booked Scheduler.  If not, see <http://www.gnu.org/licenses/>.
 */

require_once(ROOT_DIR . 'lib/Application/Authentication/namespace.php');

class Customapp extends Authentication implements IAuthentication
{
    private $authToDecorate;
    private $_registration;
    
    /**
     * @var string
     */
    private $username;
    
    /**
     * @var string
     */
    private $auth;
    
    /**
     * @var string
     */
    private $password;
    
    /** @var Customapp_User */
    private $user;
    
    public function SetRegistration($registration)
    {
        $this->_registration = $registration;
    }

    private function GetRegistration()
    {
        if ($this->_registration == null)
        {
            $this->_registration = new Registration();
        }

        return $this->_registration;
    }

    public function __construct(Authentication $authentication)
    {
        $this->authToDecorate = $authentication;
        
        require_once(ROOT_DIR . 'plugins/Authentication/customapp/api.php');
        
        if (!class_exists('Customapp_authenticate'))
        {
            throw new Exception('Could not load Customapp authentication.');
        }
        
        $this->auth = new customapp_authenticate;
        
        if( !isset($_SESSION['login']['username']) || !isset($_SESSION['booked']) ) 
        {
            header('Location: /logout.php');
        }
    }

    public function Validate($username, $password)
    {
        $username = $_SESSION['login']['username'];
        
        if ($this->user = $this->auth->authenticate($username))
        {
            return true;
        }
        
        return false;
    }

    public function Login($username, $loginContext)
    {
        $username = $_SESSION['login']['username'];
        if ($this->UserExists())
        {
            $this->Synchronize();
            if($this->auth->isAdmin($username)) 
            {
                require_once(ROOT_DIR . 'plugins/Authentication/customapp/booked.php');
                $bookedApi = new Customapp_booked;
                $bookedApi->addToAdmin($bookedApi->getUserId($username));
            }
        }
        return $this->authToDecorate->Login($username, $loginContext);
    }

    public function Logout(UserSession $user)
    {
        $this->authToDecorate->Logout($user);
    }

    public function AreCredentialsKnown()
    {
        return (bool)$_SESSION['login']['username'];
    }

    public function ShowUsernamePrompt()
    {
        return false;
    }

    public function ShowPasswordPrompt()
    {
        return false;
    }

    public function ShowPersistLoginPrompt()
    {
        return false;
    }

    public function ShowForgotPasswordPrompt()
    {
        return false;
    }
    
    private function UserExists()
    {
        return $this->user != null;
    }
    
    private function Synchronize()
    {
        $registration = $this->GetRegistration();
        $email = $this->user->email != ''?$this->user->email:$this->user->f_name.'.'.$this->user->l_name.'@no-reply.com';
        $registration->Synchronize(
            new AuthenticatedUser(
                $this->user->username,
                $email,
                $this->user->f_name,
                $this->user->l_name,
                '',
                Configuration::Instance()->GetKey(ConfigKeys::LANGUAGE),
                Configuration::Instance()->GetDefaultTimezone(),
                null, null, null)
        );
    }
}

?>