class.ilTermsOfServiceDocumentsContainsHtmlValidator.php

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<?php

declare(strict_types=1);

class ilTermsOfServiceDocumentsContainsHtmlValidator
{
    private const LIBXML_CODE_HTML_UNKNOWN_TAG = 801;

    private string $text;
    private bool $xmlErrorState = false;
    private array $xmlErrors = [];

    public function __construct(string $text)
    {
        $this->text = $text;
    }

    public function isValid(): bool
    {
        if (!preg_match('/<[^>]+?>/', $this->text)) {
            return false;
        }

        try {
            set_error_handler(static function (int $severity, string $message, string $file, int $line): void {
                throw new ErrorException($message, $severity, $severity, $file, $line);
            });

            $this->beginXmlLogging();

            $dom = new DOMDocument();
            $import_succeeded = $dom->loadHTML($this->text);

            $this->endXmlLogging();

            if (!$import_succeeded || $this->xmlErrorsOccurred()) {
                return false;
            }

            $iter = new RecursiveIteratorIterator(
                new ilHtmlDomNodeIterator($dom),
                RecursiveIteratorIterator::SELF_FIRST
            );
            foreach ($iter as $element) {
                if (strtolower($element->nodeName) === 'body') {
                    continue;
                }

                if ($element->nodeType === XML_ELEMENT_NODE) {
                    return true;
                }
            }

            return false;
        } catch (Throwable $e) {
            $this->endXmlLogging();
            return false;
        } finally {
            restore_error_handler();
        }
    }

    private function beginXmlLogging(): void
    {
        $this->xmlErrorState = libxml_use_internal_errors(true);
        libxml_clear_errors();
    }

    private function addErrors(): void
    {
        $currentErrors = libxml_get_errors();
        libxml_clear_errors();

        $this->xmlErrors = $currentErrors;
    }

    private function endXmlLogging(): void
    {
        $this->addErrors();

        libxml_use_internal_errors($this->xmlErrorState);
    }

    private function relevantXmlErrors(): array
    {
        return array_filter($this->xmlErrors, static function (LibXMLError $error): bool {
            return $error->code !== self::LIBXML_CODE_HTML_UNKNOWN_TAG;
        });
    }

    private function xmlErrorsOccurred(): bool
    {
        return $this->relevantXmlErrors() !== [];
    }
}