Redirect plugin to matreshka (event OnPageNotFound)

<?php
if ($modx->context->key !== 'mgr' ) {
    $parts = array_reverse(explode('/', $_SERVER['REQUEST_URI']));
    if ($parts[0]) {
        $alias = str_replace('.html', '', $parts[0]);
    } else {
        $alias = $parts[1];
    }
    
    if ($res = $modx->getObject('modResource', array('alias' => $alias))) {
        $uri = $modx->makeUrl($res->id);
        $modx->sendRedirect($uri, array('responseCode' => 'HTTP/1.1 301 Moved Permanently'));
    }
    
}