<?php
/**
 * Zend Framework (http://framework.zend.com/)
 *
 * @link      http://github.com/zendframework/zf2 for the canonical source repository
 * @copyright Copyright (c) 2005-2015 Zend Technologies USA Inc. (http://www.zend.com)
 * @license   http://framework.zend.com/license/new-bsd New BSD License
 */

namespace Zend\Paginator\Adapter;

use Countable;
use Zend\Paginator\SerializableLimitIterator;

class Iterator implements AdapterInterface
{
    /**
     * Iterator which implements Countable
     *
     * @var \Iterator
     */
    protected $iterator = null;

    /**
     * Item count
     *
     * @var int
     */
    protected $count = null;

    /**
     * Constructor.
     *
     * @param  \Iterator $iterator Iterator to paginate
     * @throws Exception\InvalidArgumentException
     */
    public function __construct(\Iterator $iterator)
    {
        if (! $iterator instanceof Countable) {
            throw new Exception\InvalidArgumentException('Iterator must implement Countable');
        }

        $this->iterator = $iterator;
        $this->count = count($iterator);
    }

    /**
     * Returns an iterator of items for a page, or an empty array.
     *
     * @param  int $offset Page offset
     * @param  int $itemCountPerPage Number of items per page
     * @return array|SerializableLimitIterator
     */
    public function getItems($offset, $itemCountPerPage)
    {
        if ($this->count == 0) {
            return [];
        }
        return new SerializableLimitIterator($this->iterator, $offset, $itemCountPerPage);
    }

    /**
     * Returns the total number of rows in the collection.
     *
     * @return int
     */
    public function count()
    {
        return $this->count;
    }
}
