<?php
class MyDOMDocument extends DOMDocument
{

    /**
     * Smart cache
     *
     * @var array
     */
    private $smart_query_cache = [];
    /**
     * DOMXPath
     *
     * @var DOMXPath
     */
    private $query_provider = null;

    public function smartQuery($query): DOMNodeList
    {
        if ($this->query_provider === null) {
            $this->query_provider = new DOMXPath($this);
        }

        if ($this->smart_query_cache[$query] ?? null) {
            //dump("Repeat");
            return $this->smart_query_cache[$query];
        }

        $retval = $this->query_provider->query($query);
        $this->smart_query_cache[$query] = $retval;
        return $retval;
    }

    /**
     * stripComments
     *
     * @return MyDOMDocument
     */
    public function stripComments(): MyDOMDocument
    {

        $xpath = new DOMXPath($this);
        $comments = $xpath->query('//comment()');
        foreach ($comments as $comment) {
            $comment->parentNode->removeChild($comment);
        }

        return $this;
    }

    /**
     * Load includes in XML Schema
     *
     * @return MyDOMDocument
     */
    public function loadIncludes(array &$paths = []): MyDOMDocument
    {
        $query = "//*[local-name()='include']";
        $xpath = new \DOMXPath($this);
        if ($xpath->query($query)->length > 0) {
            $this->loadExt($xpath->query($query), $paths);
        }
        return $this;
    }

    /**
     * Load imports
     *
     * @return MyDOMDocument
     */
    public function loadImports(array &$paths = []): MyDOMDocument
    {
        $query = "//*[local-name()='import']";
        $xpath = new \DOMXPath($this);
        if ($xpath->query($query)->length > 0) {
            $this->loadExt($xpath->query($query), $paths);
        }
        return $this;
    }


    /**
     * Load external resources
     *
     * @param DOMNodeList $files
     * @param array $paths
     * @return void
     */
    private function loadExt(DOMNodeList $files, array &$paths = []): void
    {

        /** @var DOMElement $file */
        foreach ($files as $file) {

            $baseName = basename($file->getAttribute("schemaLocation"));

            if (empty($paths[$baseName])) {

                $paths[$baseName] = true;

                $parent = $file->parentNode;
                $path = dirname($file->baseURI) . DIRECTORY_SEPARATOR . $file->getAttribute("schemaLocation");

                if (file_exists($path)) {

                    $xsd = new \MyDOMDocument();
                    $result = $xsd->load($path, LIBXML_DTDLOAD | LIBXML_DTDATTR | LIBXML_NOENT | LIBXML_XINCLUDE);
                    if ($result) {

                        $_PATHS[$file->getAttribute("schemaLocation")] = true;

                        $xsd->loadImports($paths)->loadIncludes($paths);
                        foreach ($xsd->documentElement->childNodes as $node) {
                            $node = $this->importNode($node, true);
                            $parent->insertBefore($node, $file);
                        }
                    }
                }
                $parent->removeChild($file);
            }
        }
    }
}