Neos FlowQuery Depth filter

DepthOperation.php

<?php

namespace TYPO3\NeosDemoTypo3Org\FlowQuery\Operation;

use TYPO3\Eel\FlowQuery\FlowQuery;
use TYPO3\Eel\FlowQuery\Operations\AbstractOperation;

class DepthOperation extends AbstractOperation
{
    /**
     * {@inheritdoc}
     *
     * @var string
     */
    static protected $shortName = 'depth';

    /**
     * {@inheritdoc}
     *
     * @param FlowQuery $flowQuery the FlowQuery object
     * @param array $arguments the arguments for this operation
     * @return void
     */
    public function evaluate(FlowQuery $flowQuery, array $arguments)
    {
        if (!isset($arguments[0])) {
            throw new \TYPO3\Eel\FlowQuery\FlowQueryException("Depth argument expects depth to select as first argument");
        }
        $depth = $arguments[0];

        $filter = null;
        if (isset($arguments[1])) {
            $filter = $arguments[1];
        }

        if (isset($filter)) {
            $flowQuery->pushOperation('filter', array($filter));
        }
        for ($i = 0; $i < $depth; $i++) {
            $flowQuery->pushOperation('children', array());
        }
    }
}