public function findMaximumRights(array $roles, ResourceNode $resource)
    {
        //add the role anonymous for everyone !
        if (!in_array('ROLE_ANONYMOUS', $roles)) {
            $roles[] = 'ROLE_ANONYMOUS';
        }

        $dql = '
            SELECT rrw.mask
            FROM Claroline\CoreBundle\Entity\Resource\ResourceRights rrw
            JOIN rrw.role role
            JOIN rrw.resourceNode resource
            WHERE ';

        $index = 0;

        foreach ($roles as $key => $role) {
            $dql .= 0 !== $index ? ' OR ' : '';
            $dql .= "resource.id = {$resource->getId()} AND role.name = :role{$key}";
            ++$index;
        }

        $query = $this->_em->createQuery($dql);

        foreach ($roles as $key => $role) {
            $query->setParameter("role{$key}", $role);
        }

        $results = $query->getResult();
        $mask = 0;

        foreach ($results as $result) {
            $mask |= $result['mask'];
        }

        return $mask;
    }