function addNode(AdminNode $node)
 {
     $node_id = $node->getId();
     if (isset($this->nodes[$node_id])) {
         return $node_id;
     }
     $this->nodes[$node_id] = $node->toArray();
     $this->session->set('history', $this->nodes);
     return $node_id;
 }
 function getOperationUrl(AdminNode $node, $component, $operation, $args = array())
 {
     $args_string = http_build_query($args);
     return "node/{$node->getId()}?component=" . urlencode($component) . '&operation=' . urlencode($operation) . '&' . $args_string;
 }