public function download(){

        if (!$this->hasRequestParameter('uri')) {
            throw new common_exception_MissingParameter('uri', __METHOD__);
        }
        if (!$this->hasRequestParameter('stylesheetUri')) {
            throw new common_exception_MissingParameter('stylesheetUri', __METHOD__);
        }
        if (!$this->hasRequestParameter('lang')) {
            throw new common_exception_MissingParameter('lang', __METHOD__);
        }


        $item = new \core_kernel_classes_Resource($this->getRequestParameter('uri'));
        $lang = $this->getRequestParameter('lang');
        $styleSheet = $this->getRequestParameter('stylesheetUri');

        if (!\tao_helpers_File::securityCheck($styleSheet, true)) {
            throw new \common_exception_Error('invalid stylesheet path "'.$styleSheet.'"');
        }

        header('Set-Cookie: fileDownload=true');
        setcookie('fileDownload','true', 0, '/');
        header('Content-type: application/octet-stream');
        header(sprintf('Content-Disposition: attachment; filename=%s', basename($styleSheet)));
        echo CssHelper::downloadCssFile($item, $lang, $styleSheet);
    }