[Module development] How to correctly find SSL certs path?

Good morning,
I'm developing Varnish module for ISPConfig. Currently, to detect SSL path, I do this kind of code inside function update($event_name, $data):

Code:

if($data['new']['ssl_letsencrypt'] == 'y'){
    // It is a Let's Encrypt SSL certificate
    $key_file = $data['new']['document_root'].'/ssl/'.$data['new']['ssl_domain'].'-le.key';
    $crt_file = $data['new']['document_root'].'/ssl/'.$data['new']['ssl_domain'].'-le.crt';
} else{
    // It is an ordinary SSL certificate
    $key_file = $data['new']['document_root'].'/ssl/'.$data['new']['ssl_domain'].'.key';
    $crt_file = $data['new']['document_root'].'/ssl/'.$data['new']['ssl_domain'].'.crt';
}

This works but I'm not sure if I do it on the best way. Is this correct? Is there a better way to achieve this? Does ISPConfig has a mechanism to send SSL certificates path directly to plugins?