<?php

namespace Elastica;

/**
 * scan and scroll object
 *
 * @category Xodoa
 * @package Elastica
 * @author Manuel Andreo Garcia <andreo.garcia@gmail.com>
 * @link http://www.elasticsearch.org/guide/en/elasticsearch/guide/current/scan-scroll.html
 */
class ScanAndScroll implements \Iterator {

    /**
     * time value parameter
     *
     * @link http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/search-request-scroll.html
     * @var string
     */
    public $expiryTime;

    /**
     * @var int
     */
    public $sizePerShard;

    /**
     * @var Search
     */
    protected $_search;

    /**
     * @var null|string
     */
    protected $_nextScrollId = null;

    /**
     * @var null|string
     */
    protected $_lastScrollId = null;

    /**
     * @var null|ResultSet
     */
    protected $_currentResultSet = null;

    /**
     * Constructs scroll iterator object
     *
     * @param Search $search
     * @param string $expiryTime
     * @param int $sizePerShard
     */
    public function __construct(Search $search, $expiryTime = '1m', $sizePerShard = 1000) {
        $this->_search = $search;
        $this->expiryTime = $expiryTime;
        $this->sizePerShard = $sizePerShard;
    }

    /**
     * Return the current result set
     *
     * @link http://php.net/manual/en/iterator.current.php
     * @return ResultSet
     */
    public function current() {
        return $this->_currentResultSet;
    }

    /**
     * Perform next scroll search
     *
     * @link http://php.net/manual/en/iterator.next.php
     * @return void
     */
    public function next() {
        $this->_scroll();
    }

    /**
     * Return the scroll id of current scroll request
     *
     * @link http://php.net/manual/en/iterator.key.php
     * @return string
     */
    public function key() {
        return $this->_lastScrollId;
    }

    /**
     * Returns true if current result set contains one hit
     *
     * @link http://php.net/manual/en/iterator.valid.php
     * @return boolean
     */
    public function valid() {
        return
            $this->_nextScrollId !== null
            && $this->_currentResultSet !== null
            && $this->_currentResultSet->count() > 0;
    }

    /**
     * Start the initial scan search
     * @link http://php.net/manual/en/iterator.rewind.php
     * @throws \Elastica\Exception\InvalidException
     * @return void
     */
    public function rewind() {
        $this->_search->getQuery()->setSize($this->sizePerShard);

        $this->_search->setOption(Search::OPTION_SEARCH_TYPE, Search::OPTION_SEARCH_TYPE_SCAN);
        $this->_search->setOption(Search::OPTION_SCROLL, $this->expiryTime);

        // initial scan request
        $this->_setScrollId($this->_search->search());

        // trigger first scroll request
        $this->_scroll();
    }

    /**
     * Perform next scroll search
     * @throws \Elastica\Exception\InvalidException
     * @return void
     */
    protected function _scroll() {
        $this->_search->setOption(Search::OPTION_SEARCH_TYPE, Search::OPTION_SEARCH_TYPE_SCROLL);
        $this->_search->setOption(Search::OPTION_SCROLL_ID, $this->_nextScrollId);

        $resultSet = $this->_search->search();
        $this->_currentResultSet = $resultSet;
        $this->_setScrollId($resultSet);
    }

    /**
     * Save last scroll id and extract the new one if possible
     * @param ResultSet $resultSet
     */
    protected function _setScrollId(ResultSet $resultSet) {
        $this->_lastScrollId = $this->_nextScrollId;

        $this->_nextScrollId = null;
        if($resultSet->getResponse()->isOk()) {
            $this->_nextScrollId = $resultSet->getResponse()->getScrollId();
        }
    }

}