<?php
/**
* @package dompdf
* @link https://github.com/dompdf/dompdf
* @license http://www.gnu.org/copyleft/lesser.html GNU Lesser General Public License
*/
namespace Dompdf\Frame;

use Iterator;
use Dompdf\Frame;

/**
* Pre-order Iterator
*
* Returns frames in preorder traversal order (parent then children)
*
* @package dompdf
*/
class FrameTreeIterator implements Iterator
{
/**
* @var Frame
*/
protected $_root;

/**
* @var Frame[]
*/
protected $_stack = [];

/**
* @var int
*/
protected $_num;

/**
* @param Frame $root
*/
public function __construct(Frame $root)
{
$this->_stack[] = $this->_root = $root;
$this->_num = 0;
}

public function rewind(): void
{
$this->_stack = [$this->_root];
$this->_num = 0;
}

/**
* @return bool
*/
public function valid(): bool
{
return count($this->_stack) > 0;
}

/**
* @return int
*/
public function key(): int
{
return $this->_num;
}

/**
* @return Frame
*/
public function current(): Frame
{
return end($this->_stack);
}

public function next(): void
{
$b = array_pop($this->_stack);
$this->_num++;

// Push all children onto the stack in reverse order
if ($c = $b->get_last_child()) {
$this->_stack[] = $c;
while ($c = $c->get_prev_sibling()) {
$this->_stack[] = $c;
}
}
}
}