<?php
/**
 * TPagedDataSource, TPagedListIterator, TPagedMapIterator classes
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @link http://www.pradosoft.com/
 * @copyright Copyright &copy; 2005-2014 PradoSoft
 * @license http://www.pradosoft.com/license/
 * @package Prado\Collections
 */

namespace Prado\Collections;

/**
 * TPagedListIterator class
 *
 * TPagedListIterator implements \Iterator interface.
 *
 * TPagedListIterator is used by {@link TPagedDataSource}. It allows TPagedDataSource
 * to return a new iterator for traversing the items in a {@link TList} object.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @package Prado\Collections
 * @since 3.0
 */
class TPagedListIterator implements \Iterator
{
	private $_list;
	private $_startIndex;
	private $_count;
	private $_index;

	/**
	 * Constructor.
	 * @param TList the data to be iterated through
	 * @param integer start index
	 * @param integer number of items to be iterated through
	 */
	public function __construct(TList $list,$startIndex,$count)
	{
		$this->_list=$list;
		$this->_index=0;
		$this->_startIndex=$startIndex;
		if($startIndex+$count>$list->getCount())
			$this->_count=$list->getCount()-$startIndex;
		else
			$this->_count=$count;
	}

	/**
	 * Rewinds internal array pointer.
	 * This method is required by the interface Iterator.
	 */
	public function rewind()
	{
		$this->_index=0;
	}

	/**
	 * Returns the key of the current array item.
	 * This method is required by the interface Iterator.
	 * @return integer the key of the current array item
	 */
	public function key()
	{
		return $this->_index;
	}

	/**
	 * Returns the current array item.
	 * This method is required by the interface Iterator.
	 * @return mixed the current array item
	 */
	public function current()
	{
		return $this->_list->itemAt($this->_startIndex+$this->_index);
	}

	/**
	 * Moves the internal pointer to the next array item.
	 * This method is required by the interface Iterator.
	 */
	public function next()
	{
		$this->_index++;
	}

	/**
	 * Returns whether there is an item at current position.
	 * This method is required by the interface Iterator.
	 * @return boolean
	 */
	public function valid()
	{
		return $this->_index<$this->_count;
	}
}