<?php

/*
 * Created on Monday, January 28, 2008
 *
 * API for MediaWiki 1.8+
 *
 * Copyright (C) 2008 Brent Garber
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 * http://www.gnu.org/copyleft/gpl.html
 */

if ( !defined( 'MEDIAWIKI' ) ) {
	// Eclipse helper - will be ignored in production
	require_once ( 'ApiQueryBase.php' );
}

/**
 * Query module to get list of random pages
 *
 * @ingroup API
 */

 class ApiQueryRandom extends ApiQueryGeneratorBase {

	public function __construct( $query, $moduleName ) {
		parent :: __construct( $query, $moduleName, 'rn' );
	}

	public function execute() {
		$this->run();
	}

	public function executeGenerator( $resultPageSet ) {
		$this->run( $resultPageSet );
	}

	protected function prepareQuery( $randstr, $limit, $namespace, &$resultPageSet, $redirect ) {
		$this->resetQueryParams();
		$this->addTables( 'page' );
		$this->addOption( 'LIMIT', $limit );
		$this->addWhereFld( 'page_namespace', $namespace );
		$this->addWhereRange( 'page_random', 'newer', $randstr, null );
		$this->addWhereFld( 'page_is_redirect', $redirect );
		$this->addOption( 'USE INDEX', 'page_random' );
		if ( is_null( $resultPageSet ) )
			$this->addFields( array( 'page_id', 'page_title', 'page_namespace' ) );
		else
			$this->addFields( $resultPageSet->getPageTableFields() );
	}

	protected function runQuery( &$resultPageSet ) {
		$db = $this->getDB();
		$res = $this->select( __METHOD__ );
		$count = 0;
		while ( $row = $db->fetchObject( $res ) ) {
			$count++;
			if ( is_null( $resultPageSet ) )
			{
				// Prevent duplicates
				if ( !in_array( $row->page_id, $this->pageIDs ) )
				{
					$fit = $this->getResult()->addValue(
							array( 'query', $this->getModuleName() ),
							null, $this->extractRowInfo( $row ) );
					if ( !$fit )
						// We can't really query-continue a random list.
						// Return an insanely high value so
						// $count < $limit is false
						return 1E9;
					$this->pageIDs[] = $row->page_id;
				}
			}
			else
				$resultPageSet->processDbRow( $row );
		}
		$db->freeResult( $res );
		return $count;
	}

	public function run( $resultPageSet = null ) {
		$params = $this->extractRequestParams();
		$result = $this->getResult();
		$this->pageIDs = array();
		
		$this->prepareQuery( wfRandom(), $params['limit'], $params['namespace'], $resultPageSet, $params['redirect'] );
		$count = $this->runQuery( $resultPageSet );
		if ( $count < $params['limit'] )
		{
			/* We got too few pages, we probably picked a high value
			 * for page_random. We'll just take the lowest ones, see
			 * also the comment in Title::getRandomTitle()
			 */
			 $this->prepareQuery( 0, $params['limit'] - $count, $params['namespace'], $resultPageSet, $params['redirect'] );
			 $this->runQuery( $resultPageSet );
		}

		if ( is_null( $resultPageSet ) ) {
			$result->setIndexedTagName_internal( array( 'query', $this->getModuleName() ), 'page' );
		}
	}

	private function extractRowInfo( $row ) {
		$title = Title::makeTitle( $row->page_namespace, $row->page_title );
		$vals = array();
		$vals['id'] = intval( $row->page_id );
		ApiQueryBase::addTitleInfo( $vals, $title );
		return $vals;
	}

	public function getCacheMode( $params ) {
		return 'public';
	}

	public function getAllowedParams() {
		return array (
			'namespace' => array(
				ApiBase :: PARAM_TYPE => 'namespace',
				ApiBase :: PARAM_ISMULTI => true
			),
			'limit' => array (
				ApiBase :: PARAM_TYPE => 'limit',
				ApiBase :: PARAM_DFLT => 1,
				ApiBase :: PARAM_MIN => 1,
				ApiBase :: PARAM_MAX => 10,
				ApiBase :: PARAM_MAX2 => 20
			),
			'redirect' => false,
		);
	}

	public function getParamDescription() {
		return array (
			'namespace' => 'Return pages in these namespaces only',
			'limit' => 'Limit how many random pages will be returned',
			'redirect' => 'Load a random redirect instead of a random page'
		);
	}

	public function getDescription() {
		return array(	'Get a set of random pages',
				'NOTE: Pages are listed in a fixed sequence, only the starting point is random. This means that if, for example, "Main Page" is the first ',
				'      random page on your list, "List of fictional monkeys" will *always* be second, "List of people on stamps of Vanuatu" third, etc.',
				'NOTE: If the number of pages in the namespace is lower than rnlimit, you will get fewer pages. You will not get the same page twice.'
		);
	}

	protected function getExamples() {
		return 'api.php?action=query&list=random&rnnamespace=0&rnlimit=2';
	}

	public function getVersion() {
		return __CLASS__ . ': $Id: ApiQueryRandom.php overlordq$';
	}
}