<?php

/*
 * Created on Oct 16, 2006
 *
 * API for MediaWiki 1.8+
 *
 * Copyright (C) 2006 Yuri Astrakhan <Firstname><Lastname>@gmail.com
 *
 * 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" );
}

/**
 * This is a three-in-one module to query:
 *   * backlinks  - links pointing to the given page,
 *   * embeddedin - what pages transclude the given page within themselves,
 *   * imageusage - what pages use the given image
 *
 * @ingroup API
 */
class ApiQueryBacklinks extends ApiQueryGeneratorBase {

	private $params, $rootTitle, $contRedirs, $contLevel, $contTitle, $contID, $redirID, $redirect;
	private $bl_ns, $bl_from, $bl_table, $bl_code, $bl_title, $bl_sort, $bl_fields, $hasNS;
	private $pageMap, $resultArr;

	// output element name, database column field prefix, database table
	private $backlinksSettings = array (
		'backlinks' => array (
			'code' => 'bl',
			'prefix' => 'pl',
			'linktbl' => 'pagelinks'
		),
		'embeddedin' => array (
			'code' => 'ei',
			'prefix' => 'tl',
			'linktbl' => 'templatelinks'
		),
		'imageusage' => array (
			'code' => 'iu',
			'prefix' => 'il',
			'linktbl' => 'imagelinks'
		)
	);

	public function __construct( $query, $moduleName ) {
		extract( $this->backlinksSettings[$moduleName] );
		$this->resultArr = array();

		parent :: __construct( $query, $moduleName, $code );
		$this->bl_ns = $prefix . '_namespace';
		$this->bl_from = $prefix . '_from';
		$this->bl_table = $linktbl;
		$this->bl_code = $code;

		$this->hasNS = $moduleName !== 'imageusage';
		if ( $this->hasNS ) {
			$this->bl_title = $prefix . '_title';
			$this->bl_sort = "{$this->bl_ns}, {$this->bl_title}, {$this->bl_from}";
			$this->bl_fields = array (
				$this->bl_ns,
				$this->bl_title
			);
		} else {
			$this->bl_title = $prefix . '_to';
			$this->bl_sort = "{$this->bl_title}, {$this->bl_from}";
			$this->bl_fields = array (
				$this->bl_title
			);
		}
	}

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

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

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

	private function prepareFirstQuery( $resultPageSet = null ) {
		/* SELECT page_id, page_title, page_namespace, page_is_redirect
		 * FROM pagelinks, page WHERE pl_from=page_id
		 * AND pl_title='Foo' AND pl_namespace=0
		 * LIMIT 11 ORDER BY pl_from
		 */
		$db = $this->getDB();
		$this->addTables( array( $this->bl_table, 'page' ) );
		$this->addWhere( "{$this->bl_from}=page_id" );
		if ( is_null( $resultPageSet ) )
			$this->addFields( array( 'page_id', 'page_title', 'page_namespace' ) );
		else
			$this->addFields( $resultPageSet->getPageTableFields() );

		$this->addFields( 'page_is_redirect' );
		$this->addWhereFld( $this->bl_title, $this->rootTitle->getDBkey() );

		if ( $this->hasNS )
			$this->addWhereFld( $this->bl_ns, $this->rootTitle->getNamespace() );
		$this->addWhereFld( 'page_namespace', $this->params['namespace'] );

		if ( !is_null( $this->contID ) )
			$this->addWhere( "{$this->bl_from}>={$this->contID}" );

		if ( $this->params['filterredir'] == 'redirects' )
			$this->addWhereFld( 'page_is_redirect', 1 );
		else if ( $this->params['filterredir'] == 'nonredirects' && !$this->redirect )
			// bug 22245 - Check for !redirect, as filtering nonredirects, when getting what links to them is contradictory
			$this->addWhereFld( 'page_is_redirect', 0 );

		$this->addOption( 'LIMIT', $this->params['limit'] + 1 );
		$this->addOption( 'ORDER BY', $this->bl_from );
		$this->addOption( 'STRAIGHT_JOIN' );
	}

	private function prepareSecondQuery( $resultPageSet = null ) {
		/* SELECT page_id, page_title, page_namespace, page_is_redirect, pl_title, pl_namespace
		   FROM pagelinks, page WHERE pl_from=page_id
		   AND (pl_title='Foo' AND pl_namespace=0) OR (pl_title='Bar' AND pl_namespace=1)
		   ORDER BY pl_namespace, pl_title, pl_from LIMIT 11
		 */
		$db = $this->getDB();
		$this->addTables( array( 'page', $this->bl_table ) );
		$this->addWhere( "{$this->bl_from}=page_id" );

		if ( is_null( $resultPageSet ) )
			$this->addFields( array( 'page_id', 'page_title', 'page_namespace', 'page_is_redirect' ) );
		else
			$this->addFields( $resultPageSet->getPageTableFields() );

		$this->addFields( $this->bl_title );
		if ( $this->hasNS )
			$this->addFields( $this->bl_ns );

		// We can't use LinkBatch here because $this->hasNS may be false
		$titleWhere = array();
		foreach ( $this->redirTitles as $t )
			$titleWhere[] = "{$this->bl_title} = " . $db->addQuotes( $t->getDBkey() ) .
					( $this->hasNS ? " AND {$this->bl_ns} = '{$t->getNamespace()}'" : "" );
		$this->addWhere( $db->makeList( $titleWhere, LIST_OR ) );
		$this->addWhereFld( 'page_namespace', $this->params['namespace'] );

		if ( !is_null( $this->redirID ) )
		{
			$first = $this->redirTitles[0];
			$title = $db->strencode( $first->getDBkey() );
			$ns = $first->getNamespace();
			$from = $this->redirID;
			if ( $this->hasNS )
				$this->addWhere( "{$this->bl_ns} > $ns OR " .
						"({$this->bl_ns} = $ns AND " .
						"({$this->bl_title} > '$title' OR " .
						"({$this->bl_title} = '$title' AND " .
						"{$this->bl_from} >= $from)))" );
			else
				$this->addWhere( "{$this->bl_title} > '$title' OR " .
						"({$this->bl_title} = '$title' AND " .
						"{$this->bl_from} >= $from)" );
				
		}
		if ( $this->params['filterredir'] == 'redirects' )
			$this->addWhereFld( 'page_is_redirect', 1 );
		else if ( $this->params['filterredir'] == 'nonredirects' )
			$this->addWhereFld( 'page_is_redirect', 0 );

		$this->addOption( 'LIMIT', $this->params['limit'] + 1 );
		$this->addOption( 'ORDER BY', $this->bl_sort );
		$this->addOption( 'USE INDEX', array( 'page' => 'PRIMARY' ) );
	}

	private function run( $resultPageSet = null ) {
		$this->params = $this->extractRequestParams( false );
		$this->redirect = isset( $this->params['redirect'] ) && $this->params['redirect'];
		$userMax = ( $this->redirect ? ApiBase::LIMIT_BIG1 / 2 : ApiBase::LIMIT_BIG1 );
		$botMax  = ( $this->redirect ? ApiBase::LIMIT_BIG2 / 2 : ApiBase::LIMIT_BIG2 );
		if ( $this->params['limit'] == 'max' ) {
			$this->params['limit'] = $this->getMain()->canApiHighLimits() ? $botMax : $userMax;
			$this->getResult()->addValue( 'limits', $this->getModuleName(), $this->params['limit'] );
		}

		$this->processContinue();
		$this->prepareFirstQuery( $resultPageSet );

		$db = $this->getDB();
		$res = $this->select( __METHOD__ . '::firstQuery' );

		$count = 0;
		$this->pageMap = array(); // Maps ns and title to pageid
		$this->continueStr = null;
		$this->redirTitles = array();
		while ( $row = $db->fetchObject( $res ) ) {
			if ( ++ $count > $this->params['limit'] ) {
				// We've reached the one extra which shows that there are additional pages to be had. Stop here...
				// Continue string preserved in case the redirect query doesn't pass the limit
				$this->continueStr = $this->getContinueStr( $row->page_id );
				break;
			}

			if ( is_null( $resultPageSet ) )
				$this->extractRowInfo( $row );
			else
			{
				$this->pageMap[$row->page_namespace][$row->page_title] = $row->page_id;
				if ( $row->page_is_redirect )
					$this->redirTitles[] = Title::makeTitle( $row->page_namespace, $row->page_title );

				$resultPageSet->processDbRow( $row );
			}
		}
		$db->freeResult( $res );

		if ( $this->redirect && count( $this->redirTitles ) )
		{
			$this->resetQueryParams();
			$this->prepareSecondQuery( $resultPageSet );
			$res = $this->select( __METHOD__ . '::secondQuery' );
			$count = 0;
			while ( $row = $db->fetchObject( $res ) )
			{
				if ( ++$count > $this->params['limit'] )
				{
					// We've reached the one extra which shows that there are additional pages to be had. Stop here...
					// We need to keep the parent page of this redir in
					if ( $this->hasNS )
						$parentID = $this->pageMap[$row-> { $this->bl_ns } ][$row-> { $this->bl_title } ];
					else
						$parentID = $this->pageMap[NS_IMAGE][$row-> { $this->bl_title } ];
					$this->continueStr = $this->getContinueRedirStr( $parentID, $row->page_id );
					break;
				}

				if ( is_null( $resultPageSet ) )
					$this->extractRedirRowInfo( $row );
				else
					$resultPageSet->processDbRow( $row );
			}
			$db->freeResult( $res );
		}
		if ( is_null( $resultPageSet ) ) {
			// Try to add the result data in one go and pray that it fits
			$fit = $this->getResult()->addValue( 'query', $this->getModuleName(), array_values( $this->resultArr ) );
			if ( !$fit )
			{
				// It didn't fit. Add elements one by one until the
				// result is full.
				foreach ( $this->resultArr as $pageID => $arr )
				{
					// Add the basic entry without redirlinks first
					$fit = $this->getResult()->addValue(
						array( 'query', $this->getModuleName() ),
						null, array_diff_key( $arr, array( 'redirlinks' => '' ) ) );
					if ( !$fit )
					{
						$this->continueStr = $this->getContinueStr( $pageID );
						break;
					}

					$hasRedirs = false;
					foreach ( (array)@$arr['redirlinks'] as $key => $redir )
					{
						$fit = $this->getResult()->addValue(
							array( 'query', $this->getModuleName(), $pageID, 'redirlinks' ),
							$key, $redir );
						if ( !$fit )
						{
							$this->continueStr = $this->getContinueRedirStr( $pageID, $redir['pageid'] );
							break;
						}
						$hasRedirs = true;
					}
					if ( $hasRedirs )
						$this->getResult()->setIndexedTagName_internal(
							array( 'query', $this->getModuleName(), $pageID, 'redirlinks' ),
							$this->bl_code );
					if ( !$fit )
						break;
				}
			}

			$this->getResult()->setIndexedTagName_internal(
					 array( 'query', $this->getModuleName() ),
					 $this->bl_code );
		}
		if ( !is_null( $this->continueStr ) )
			$this->setContinueEnumParameter( 'continue', $this->continueStr );
	}

	private function extractRowInfo( $row ) {
		$this->pageMap[$row->page_namespace][$row->page_title] = $row->page_id;
		$t = Title::makeTitle( $row->page_namespace, $row->page_title );
		$a = array( 'pageid' => intval( $row->page_id ) );
		ApiQueryBase::addTitleInfo( $a, $t );
		if ( $row->page_is_redirect )
		{
			$a['redirect'] = '';
			$this->redirTitles[] = $t;
		}
		// Put all the results in an array first
		$this->resultArr[$a['pageid']] = $a;
	}

	private function extractRedirRowInfo( $row )
	{
		$a['pageid'] = intval( $row->page_id );
		ApiQueryBase::addTitleInfo( $a, Title::makeTitle( $row->page_namespace, $row->page_title ) );
		if ( $row->page_is_redirect )
			$a['redirect'] = '';
		$ns = $this->hasNS ? $row-> { $this->bl_ns } : NS_FILE;
		$parentID = $this->pageMap[$ns][$row-> { $this->bl_title } ];
		// Put all the results in an array first
		$this->resultArr[$parentID]['redirlinks'][] = $a;
		$this->getResult()->setIndexedTagName( $this->resultArr[$parentID]['redirlinks'], $this->bl_code );
	}

	protected function processContinue() {
		if ( !is_null( $this->params['continue'] ) )
			$this->parseContinueParam();
		else {
			if ( $this->params['title'] !== "" ) {
				$title = Title::newFromText( $this->params['title'] );
				if ( !$title ) {
					$this->dieUsageMsg( array( 'invalidtitle', $this->params['title'] ) );
				} else {
					$this->rootTitle = $title;
				}
			} else {
				$this->dieUsageMsg( array( 'missingparam', 'title' ) );
			}
		}

		// only image titles are allowed for the root in imageinfo mode
		if ( !$this->hasNS && $this->rootTitle->getNamespace() !== NS_FILE )
			$this->dieUsage( "The title for {$this->getModuleName()} query must be an image", 'bad_image_title' );
	}

	protected function parseContinueParam() {
		$continueList = explode( '|', $this->params['continue'] );
		// expected format:
		// ns | key | id1 [| id2]
		// ns+key: root title
		// id1: first-level page ID to continue from
		// id2: second-level page ID to continue from

		// null stuff out now so we know what's set and what isn't
		$this->rootTitle = $this->contID = $this->redirID = null;
		$rootNs = intval( $continueList[0] );
		if ( $rootNs === 0 && $continueList[0] !== '0' )
			// Illegal continue parameter
			$this->dieUsage( "Invalid continue param. You should pass the original value returned by the previous query", "_badcontinue" );
		$this->rootTitle = Title::makeTitleSafe( $rootNs, $continueList[1] );

		if ( !$this->rootTitle )
			$this->dieUsage( "Invalid continue param. You should pass the original value returned by the previous query", "_badcontinue" );
		$contID = intval( $continueList[2] );

		if ( $contID === 0 && $continueList[2] !== '0' )
			$this->dieUsage( "Invalid continue param. You should pass the original value returned by the previous query", "_badcontinue" );
		$this->contID = $contID;
		$redirID = intval( @$continueList[3] );
		
		if ( $redirID === 0 && @$continueList[3] !== '0' )
			// This one isn't required
			return;
		$this->redirID = $redirID;

	}

	protected function getContinueStr( $lastPageID ) {
		return $this->rootTitle->getNamespace() .
		'|' . $this->rootTitle->getDBkey() .
		'|' . $lastPageID;
	}

	protected function getContinueRedirStr( $lastPageID, $lastRedirID ) {
		return $this->getContinueStr( $lastPageID ) . '|' . $lastRedirID;
	}

	public function getAllowedParams() {
		$retval =  array (
			'title' => null,
			'continue' => null,
			'namespace' => array (
				ApiBase :: PARAM_ISMULTI => true,
				ApiBase :: PARAM_TYPE => 'namespace'
			),
			'filterredir' => array(
				ApiBase :: PARAM_DFLT => 'all',
				ApiBase :: PARAM_TYPE => array(
					'all',
					'redirects',
					'nonredirects'
				)
			),
			'limit' => array (
				ApiBase :: PARAM_DFLT => 10,
				ApiBase :: PARAM_TYPE => 'limit',
				ApiBase :: PARAM_MIN => 1,
				ApiBase :: PARAM_MAX => ApiBase :: LIMIT_BIG1,
				ApiBase :: PARAM_MAX2 => ApiBase :: LIMIT_BIG2
			)
		);
		if ( $this->getModuleName() == 'embeddedin' )
			return $retval;
		$retval['redirect'] = false;
		return $retval;
	}

	public function getParamDescription() {
		$retval = array (
			'title' => 'Title to search.',
			'continue' => 'When more results are available, use this to continue.',
			'namespace' => 'The namespace to enumerate.',
		);
		if ( $this->getModuleName() != 'embeddedin' )
			return array_merge( $retval, array(
				'redirect' => 'If linking page is a redirect, find all pages that link to that redirect as well. Maximum limit is halved.',
				'filterredir' => "How to filter for redirects. If set to nonredirects when {$this->bl_code}redirect is enabled, this is only applied to the second level",
				'limit' => "How many total pages to return. If {$this->bl_code}redirect is enabled, limit applies to each level separately (which means you may get up to 2 * limit results)."
			) );
		return array_merge( $retval, array(
			'filterredir' => 'How to filter for redirects',
			'limit' => 'How many total pages to return.'
		) );
	}

	public function getDescription() {
		switch ( $this->getModuleName() ) {
			case 'backlinks' :
				return 'Find all pages that link to the given page';
			case 'embeddedin' :
				return 'Find all pages that embed (transclude) the given title';
			case 'imageusage' :
				return 'Find all pages that use the given image title.';
			default :
				ApiBase :: dieDebug( __METHOD__, 'Unknown module name' );
		}
	}
	
	public function getPossibleErrors() {
		return array_merge( parent::getPossibleErrors(), array(
			array( 'invalidtitle', 'title' ),
			array( 'missingparam', 'title' ),
			array( 'code' => 'bad_image_title', 'info' => "The title for {$this->getModuleName()} query must be an image" ),
			array( 'code' => '_badcontinue', 'info' => 'Invalid continue param. You should pass the original value returned by the previous query' ),
		) );
	}

	protected function getExamples() {
		static $examples = array (
			'backlinks' => array (
				"api.php?action=query&list=backlinks&bltitle=Main%20Page",
				"api.php?action=query&generator=backlinks&gbltitle=Main%20Page&prop=info"
			),
			'embeddedin' => array (
				"api.php?action=query&list=embeddedin&eititle=Template:Stub",
				"api.php?action=query&generator=embeddedin&geititle=Template:Stub&prop=info"
			),
			'imageusage' => array (
				"api.php?action=query&list=imageusage&iutitle=File:Albert%20Einstein%20Head.jpg",
				"api.php?action=query&generator=imageusage&giutitle=File:Albert%20Einstein%20Head.jpg&prop=info"
			)
		);

		return $examples[$this->getModuleName()];
	}

	public function getVersion() {
		return __CLASS__ . ': $Id: ApiQueryBacklinks.php 69932 2010-07-26 08:03:21Z tstarling $';
	}
}