Sort operation for a set of nodes based on their index

SortRecursiveOperation.ts2

<?php

namespace Foo\Bar\TypoScript\FlowQueryOperations;

use TYPO3\Eel\FlowQuery\Operations\AbstractOperation;
use TYPO3\Flow\Annotations as Flow;
use TYPO3\TYPO3CR\Domain\Model\NodeInterface;
use TYPO3\Eel\FlowQuery\FlowQuery;

/**
 * Sort Nodes by their position in the node tree.
 *
 * Use it like this:
 *
 *    ${q(node).children().sortRecursive(['ASC'|'DESC'])}
 */
class SortRecursiveOperation extends AbstractOperation
{
    /**
     * {@inheritdoc}
     *
     * @var string
     */
    protected static $shortName = 'sortRecursive';

    /**
     * {@inheritdoc}
     *
     * @var int
     */
    protected static $priority = 100;

    /**
     * {@inheritdoc}
     *
     * We can only handle TYPO3CR Nodes.
     *
     * @param mixed $context
     *
     * @return bool
     */
    public function canEvaluate($context)
    {
        return (isset($context[0]) && ($context[0] instanceof NodeInterface));
    }

    /**
     * {@inheritdoc}
     *
     * @param FlowQuery $flowQuery the FlowQuery object
     * @param array     $arguments the arguments for this operation
     *
     * @return mixed
     */
    public function evaluate(FlowQuery $flowQuery, array $arguments)
    {
        $nodes = $flowQuery->getContext();

        $sortOrder = 'ASC';
        if (isset($arguments[0]) && !empty($arguments[0]) && in_array($arguments[0], array('ASC', 'DESC'))) {
            $sortOrder = $arguments[0];
        }

        $getIndexPath = function (NodeInterface $node) {
            $indexPath = array($node->getIndex());
            while ($node = $node->getParent()) {
                $indexPath[] = $node->getIndex();
            }

            return $indexPath;
        };

        $cmpIndex = function (NodeInterface $a, NodeInterface $b) use ($getIndexPath) {
            if ($a == $b) {
                return 0;
            }

            // Compare index path backwards until a difference is found
            $aIndexPath = $getIndexPath($a);
            $bIndexPath = $getIndexPath($b);
            while (count($aIndexPath) > 0 && count($bIndexPath) > 0) {
                $diff = (array_pop($aIndexPath) - array_pop($bIndexPath));
                if ($diff !== 0) {
                    return $diff < 0 ? -1 : 1;
                }
            }

            return 0;
        };

        usort($nodes, $cmpIndex);
        if ($sortOrder === 'DESC') {
            $nodes = array_reverse($nodes);
        }

        $flowQuery->setContext($nodes);
    }
}