Navigator.php

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<?php
 
declare(strict_types=1);
 
namespace ILIAS\MetaData\Paths\Navigator;
 
use ILIAS\MetaData\Elements\ElementInterface;
use ILIAS\MetaData\Paths\Steps\NavigatorBridge;
use ILIAS\MetaData\Paths\PathInterface;
 
class Navigator extends BaseNavigator implements NavigatorInterface
{
    public function __construct(
        PathInterface $path,
        ElementInterface $start_element,
        NavigatorBridge $bridge
    ) {
        parent::__construct($path, $start_element, $bridge);
    }
 
    public function nextStep(): ?NavigatorInterface
    {
        $return = parent::nextStep();
        if (($return instanceof NavigatorInterface) || is_null($return)) {
            return $return;
        }
        throw new \ilMDPathException('Invalid Navigator');
    }
 
    public function previousStep(): ?NavigatorInterface
    {
        $return = parent::previousStep();
        if (($return instanceof NavigatorInterface) || is_null($return)) {
            return $return;
        }
        throw new \ilMDPathException('Invalid Navigator');
    }
 
    public function elementsAtFinalStep(): \Generator
    {
        foreach (parent::elementsAtFinalStep() as $element) {
            if (!($element instanceof ElementInterface)) {
                throw new \ilMDElementsException(
                    'Invalid Navigator.'
                );
            }
            yield $element;
        }
    }
 
    public function lastElementAtFinalStep(): ?ElementInterface
    {
        $element = parent::lastElementAtFinalStep();
        if (($element instanceof ElementInterface) || is_null($element)) {
            return $element;
        }
        throw new \ilMDPathException(
            'Invalid Navigator.'
        );
    }
 
    public function elements(): \Generator
    {
        foreach (parent::elements() as $element) {
            if (!($element instanceof ElementInterface)) {
                throw new \ilMDPathException(
                    'Invalid Navigator.'
                );
            }
            yield $element;
        }
    }
 
 
    public function lastElement(): ?ElementInterface
    {
        $element = parent::lastElement();
        if (($element instanceof ElementInterface) || is_null($element)) {
            return $element;
        }
        throw new \ilMDPathException(
            'Invalid Navigator.'
        );
    }
}