<?php

/**

 * Zend Framework

 *

 * LICENSE

 *

 * This source file is subject to the new BSD license that is bundled

 * with this package in the file LICENSE.txt.

 * It is also available through the world-wide-web at this URL:

 * http://framework.zend.com/license/new-bsd

 * If you did not receive a copy of the license and are unable to

 * obtain it through the world-wide-web, please send an email

 * to license@zend.com so we can send you a copy immediately.

 *

 * @category   Zend

 * @package    Zend_Search_Lucene

 * @subpackage Index

 * @copyright  Copyright (c) 2005-2010 Zend Technologies USA Inc. (http://www.zend.com)

 * @license    http://framework.zend.com/license/new-bsd     New BSD License

 * @version    $Id: TermStreamsPriorityQueue.php 22987 2010-09-21 10:39:53Z alexander $

 */

/** Zend_Search_Lucene_Index_TermsStream_Interface */

require_once 'Zend/Search/Lucene/Index/TermsStream/Interface.php';

/**

 * @category   Zend

 * @package    Zend_Search_Lucene

 * @subpackage Index

 * @copyright  Copyright (c) 2005-2010 Zend Technologies USA Inc. (http://www.zend.com)

 * @license    http://framework.zend.com/license/new-bsd     New BSD License

 */

class Zend_Search_Lucene_TermStreamsPriorityQueue implements Zend_Search_Lucene_Index_TermsStream_Interface

{

    /**

     * Array of term streams (Zend_Search_Lucene_Index_TermsStream_Interface objects)

     *

     * @var array

     */

    protected $_termStreams;

    /**

     * Terms stream queue

     *

     * @var Zend_Search_Lucene_Index_TermsPriorityQueue

     */

    protected $_termsStreamQueue = null;

    /**

     * Last Term in a terms stream

     *

     * @var Zend_Search_Lucene_Index_Term

     */

    protected $_lastTerm = null;

    /**

     * Object constructor

     *

     * @param array $termStreams  array of term streams (Zend_Search_Lucene_Index_TermsStream_Interface objects)

     */

    public function __construct(array $termStreams)

    {

        $this->_termStreams = $termStreams;

        $this->resetTermsStream();

    }

    /**

     * Reset terms stream.

     */

    public function resetTermsStream()

    {

        /** Zend_Search_Lucene_Index_TermsPriorityQueue */

        require_once 'Zend/Search/Lucene/Index/TermsPriorityQueue.php';

        $this->_termsStreamQueue = new Zend_Search_Lucene_Index_TermsPriorityQueue();

        foreach ($this->_termStreams as $termStream) {

            $termStream->resetTermsStream();

            // Skip "empty" containers

            if ($termStream->currentTerm() !== null) {

                $this->_termsStreamQueue->put($termStream);

            }

        }

        $this->nextTerm();

    }

    /**

     * Skip terms stream up to the specified term preffix.

     *

     * Prefix contains fully specified field info and portion of searched term

     *

     * @param Zend_Search_Lucene_Index_Term $prefix

     */

    public function skipTo(Zend_Search_Lucene_Index_Term $prefix)

    {

        $this->_termsStreamQueue = new Zend_Search_Lucene_Index_TermsPriorityQueue();

        foreach ($this->_termStreams as $termStream) {

            $termStream->skipTo($prefix);

            if ($termStream->currentTerm() !== null) {

                $this->_termsStreamQueue->put($termStream);

            }

        }

        return $this->nextTerm();

    }

    /**

     * Scans term streams and returns next term

     *

     * @return Zend_Search_Lucene_Index_Term|null

     */

    public function nextTerm()

    {

        while (($termStream = $this->_termsStreamQueue->pop()) !== null) {

            if ($this->_termsStreamQueue->top() === null ||

                $this->_termsStreamQueue->top()->currentTerm()->key() !=

                            $termStream->currentTerm()->key()) {

                // We got new term

                $this->_lastTerm = $termStream->currentTerm();

                if ($termStream->nextTerm() !== null) {

                    // Put segment back into the priority queue

                    $this->_termsStreamQueue->put($termStream);

                }

                return $this->_lastTerm;

            }

            if ($termStream->nextTerm() !== null) {

                // Put segment back into the priority queue

                $this->_termsStreamQueue->put($termStream);

            }

        }

        // End of stream

        $this->_lastTerm = null;

        return null;

    }

    /**

     * Returns term in current position

     *

     * @return Zend_Search_Lucene_Index_Term|null

     */

    public function currentTerm()

    {

        return $this->_lastTerm;

    }

    /**

     * Close terms stream

     *

     * Should be used for resources clean up if stream is not read up to the end

     */

    public function closeTermsStream()

    {

        while (($termStream = $this->_termsStreamQueue->pop()) !== null) {

            $termStream->closeTermsStream();

        }

        $this->_termsStreamQueue = null;

        $this->_lastTerm         = null;

    }

}