Reset RequestContext between tests

[mediawiki.git] / includes / api / ApiPageSet.php

<?php
/**
 *
 *
 * Created on Sep 24, 2006
 *
 * Copyright © 2006, 2013 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.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 */

/**
 * This class contains a list of pages that the client has requested.
 * Initially, when the client passes in titles=, pageids=, or revisions=
 * parameter, an instance of the ApiPageSet class will normalize titles,
 * determine if the pages/revisions exist, and prefetch any additional page
 * data requested.
 *
 * When a generator is used, the result of the generator will become the input
 * for the second instance of this class, and all subsequent actions will use
 * the second instance for all their work.
 *
 * @ingroup API
 * @since 1.21 derives from ApiBase instead of ApiQueryBase
 */
class ApiPageSet extends ApiBase {
        /**
         * Constructor flag: The new instance of ApiPageSet will ignore the 'generator=' parameter
         * @since 1.21
         */
        const DISABLE_GENERATORS = 1;

        private $mDbSource;
        private $mParams;
        private $mResolveRedirects;
        private $mConvertTitles;
        private $mAllowGenerator;

        private $mAllPages = array(); // [ns][dbkey] => page_id or negative when missing
        private $mTitles = array();
        private $mGoodTitles = array();
        private $mMissingTitles = array();
        private $mInvalidTitles = array();
        private $mMissingPageIDs = array();
        private $mRedirectTitles = array();
        private $mSpecialTitles = array();
        private $mNormalizedTitles = array();
        private $mInterwikiTitles = array();
        private $mPendingRedirectIDs = array();
        private $mConvertedTitles = array();
        private $mGoodRevIDs = array();
        private $mMissingRevIDs = array();
        private $mFakePageId = -1;
        private $mCacheMode = 'public';
        private $mRequestedPageFields = array();
        /**
         * @var int
         */
        private $mDefaultNamespace = NS_MAIN;

        /**
         * Add all items from $values into the result
         * @param array $result Output
         * @param array $values Values to add
         * @param string $flag The name of the boolean flag to mark this element
         * @param string $name If given, name of the value
         */
        private static function addValues( array &$result, $values, $flag = null, $name = null ) {
                foreach ( $values as $val ) {
                        if ( $val instanceof Title ) {
                                $v = array();
                                ApiQueryBase::addTitleInfo( $v, $val );
                        } elseif ( $name !== null ) {
                                $v = array( $name => $val );
                        } else {
                                $v = $val;
                        }
                        if ( $flag !== null ) {
                                $v[$flag] = '';
                        }
                        $result[] = $v;
                }
        }

        /**
         * @param ApiBase $dbSource Module implementing getDB().
         *        Allows PageSet to reuse existing db connection from the shared state like ApiQuery.
         * @param int $flags Zero or more flags like DISABLE_GENERATORS
         * @param int $defaultNamespace The namespace to use if none is specified by a prefix.
         * @since 1.21 accepts $flags instead of two boolean values
         */
        public function __construct( ApiBase $dbSource, $flags = 0, $defaultNamespace = NS_MAIN ) {
                parent::__construct( $dbSource->getMain(), $dbSource->getModuleName() );
                $this->mDbSource = $dbSource;
                $this->mAllowGenerator = ( $flags & ApiPageSet::DISABLE_GENERATORS ) == 0;
                $this->mDefaultNamespace = $defaultNamespace;

                $this->profileIn();
                $this->mParams = $this->extractRequestParams();
                $this->mResolveRedirects = $this->mParams['redirects'];
                $this->mConvertTitles = $this->mParams['converttitles'];
                $this->profileOut();
        }

        /**
         * In case execute() is not called, call this method to mark all relevant parameters as used
         * This prevents unused parameters from being reported as warnings
         */
        public function executeDryRun() {
                $this->executeInternal( true );
        }

        /**
         * Populate the PageSet from the request parameters.
         */
        public function execute() {
                $this->executeInternal( false );
        }

        /**
         * Populate the PageSet from the request parameters.
         * @param bool $isDryRun If true, instantiates generator, but only to mark
         *    relevant parameters as used
         */
        private function executeInternal( $isDryRun ) {
                $this->profileIn();

                $generatorName = $this->mAllowGenerator ? $this->mParams['generator'] : null;
                if ( isset( $generatorName ) ) {
                        $dbSource = $this->mDbSource;
                        $isQuery = $dbSource instanceof ApiQuery;
                        if ( !$isQuery ) {
                                // If the parent container of this pageset is not ApiQuery, we must create it to run generator
                                $dbSource = $this->getMain()->getModuleManager()->getModule( 'query' );
                                // Enable profiling for query module because it will be used for db sql profiling
                                $dbSource->profileIn();
                        }
                        $generator = $dbSource->getModuleManager()->getModule( $generatorName, null, true );
                        if ( $generator === null ) {
                                $this->dieUsage( 'Unknown generator=' . $generatorName, 'badgenerator' );
                        }
                        if ( !$generator instanceof ApiQueryGeneratorBase ) {
                                $this->dieUsage( "Module $generatorName cannot be used as a generator", 'badgenerator' );
                        }
                        // Create a temporary pageset to store generator's output,
                        // add any additional fields generator may need, and execute pageset to populate titles/pageids
                        $tmpPageSet = new ApiPageSet( $dbSource, ApiPageSet::DISABLE_GENERATORS );
                        $generator->setGeneratorMode( $tmpPageSet );
                        $this->mCacheMode = $generator->getCacheMode( $generator->extractRequestParams() );

                        if ( !$isDryRun ) {
                                $generator->requestExtraData( $tmpPageSet );
                        }
                        $tmpPageSet->executeInternal( $isDryRun );

                        // populate this pageset with the generator output
                        $this->profileOut();
                        $generator->profileIn();

                        if ( !$isDryRun ) {
                                $generator->executeGenerator( $this );
                                wfRunHooks( 'APIQueryGeneratorAfterExecute', array( &$generator, &$this ) );
                        } else {
                                // Prevent warnings from being reported on these parameters
                                $main = $this->getMain();
                                foreach ( $generator->extractRequestParams() as $paramName => $param ) {
                                        $main->getVal( $generator->encodeParamName( $paramName ) );
                                }
                        }
                        $generator->profileOut();
                        $this->profileIn();

                        if ( !$isDryRun ) {
                                $this->resolvePendingRedirects();
                        }

                        if ( !$isQuery ) {
                                // If this pageset is not part of the query, we called profileIn() above
                                $dbSource->profileOut();
                        }
                } else {
                        // Only one of the titles/pageids/revids is allowed at the same time
                        $dataSource = null;
                        if ( isset( $this->mParams['titles'] ) ) {
                                $dataSource = 'titles';
                        }
                        if ( isset( $this->mParams['pageids'] ) ) {
                                if ( isset( $dataSource ) ) {
                                        $this->dieUsage( "Cannot use 'pageids' at the same time as '$dataSource'", 'multisource' );
                                }
                                $dataSource = 'pageids';
                        }
                        if ( isset( $this->mParams['revids'] ) ) {
                                if ( isset( $dataSource ) ) {
                                        $this->dieUsage( "Cannot use 'revids' at the same time as '$dataSource'", 'multisource' );
                                }
                                $dataSource = 'revids';
                        }

                        if ( !$isDryRun ) {
                                // Populate page information with the original user input
                                switch ( $dataSource ) {
                                        case 'titles':
                                                $this->initFromTitles( $this->mParams['titles'] );
                                                break;
                                        case 'pageids':
                                                $this->initFromPageIds( $this->mParams['pageids'] );
                                                break;
                                        case 'revids':
                                                if ( $this->mResolveRedirects ) {
                                                        $this->setWarning( 'Redirect resolution cannot be used ' .
                                                                'together with the revids= parameter. Any redirects ' .
                                                                'the revids= point to have not been resolved.' );
                                                }
                                                $this->mResolveRedirects = false;
                                                $this->initFromRevIDs( $this->mParams['revids'] );
                                                break;
                                        default:
                                                // Do nothing - some queries do not need any of the data sources.
                                                break;
                                }
                        }
                }
                $this->profileOut();
        }

        /**
         * Check whether this PageSet is resolving redirects
         * @return bool
         */
        public function isResolvingRedirects() {
                return $this->mResolveRedirects;
        }

        /**
         * Return the parameter name that is the source of data for this PageSet
         *
         * If multiple source parameters are specified (e.g. titles and pageids),
         * one will be named arbitrarily.
         *
         * @return string|null
         */
        public function getDataSource() {
                if ( $this->mAllowGenerator && isset( $this->mParams['generator'] ) ) {
                        return 'generator';
                }
                if ( isset( $this->mParams['titles'] ) ) {
                        return 'titles';
                }
                if ( isset( $this->mParams['pageids'] ) ) {
                        return 'pageids';
                }
                if ( isset( $this->mParams['revids'] ) ) {
                        return 'revids';
                }

                return null;
        }

        /**
         * Request an additional field from the page table.
         * Must be called before execute()
         * @param string $fieldName Field name
         */
        public function requestField( $fieldName ) {
                $this->mRequestedPageFields[$fieldName] = null;
        }

        /**
         * Get the value of a custom field previously requested through
         * requestField()
         * @param string $fieldName Field name
         * @return mixed Field value
         */
        public function getCustomField( $fieldName ) {
                return $this->mRequestedPageFields[$fieldName];
        }

        /**
         * Get the fields that have to be queried from the page table:
         * the ones requested through requestField() and a few basic ones
         * we always need
         * @return array Array of field names
         */
        public function getPageTableFields() {
                // Ensure we get minimum required fields
                // DON'T change this order
                $pageFlds = array(
                        'page_namespace' => null,
                        'page_title' => null,
                        'page_id' => null,
                );

                if ( $this->mResolveRedirects ) {
                        $pageFlds['page_is_redirect'] = null;
                }

                // only store non-default fields
                $this->mRequestedPageFields = array_diff_key( $this->mRequestedPageFields, $pageFlds );

                $pageFlds = array_merge( $pageFlds, $this->mRequestedPageFields );

                return array_keys( $pageFlds );
        }

        /**
         * Returns an array [ns][dbkey] => page_id for all requested titles.
         * page_id is a unique negative number in case title was not found.
         * Invalid titles will also have negative page IDs and will be in namespace 0
         * @return array
         */
        public function getAllTitlesByNamespace() {
                return $this->mAllPages;
        }

        /**
         * All Title objects provided.
         * @return Title[]
         */
        public function getTitles() {
                return $this->mTitles;
        }

        /**
         * Returns the number of unique pages (not revisions) in the set.
         * @return int
         */
        public function getTitleCount() {
                return count( $this->mTitles );
        }

        /**
         * Title objects that were found in the database.
         * @return Title[] Array page_id (int) => Title (obj)
         */
        public function getGoodTitles() {
                return $this->mGoodTitles;
        }

        /**
         * Returns the number of found unique pages (not revisions) in the set.
         * @return int
         */
        public function getGoodTitleCount() {
                return count( $this->mGoodTitles );
        }

        /**
         * Title objects that were NOT found in the database.
         * The array's index will be negative for each item
         * @return Title[]
         */
        public function getMissingTitles() {
                return $this->mMissingTitles;
        }

        /**
         * Titles that were deemed invalid by Title::newFromText()
         * The array's index will be unique and negative for each item
         * @return string[] Array of strings (not Title objects)
         */
        public function getInvalidTitles() {
                return $this->mInvalidTitles;
        }

        /**
         * Page IDs that were not found in the database
         * @return array Array of page IDs
         */
        public function getMissingPageIDs() {
                return $this->mMissingPageIDs;
        }

        /**
         * Get a list of redirect resolutions - maps a title to its redirect
         * target, as an array of output-ready arrays
         * @return array
         */
        public function getRedirectTitles() {
                return $this->mRedirectTitles;
        }

        /**
         * Get a list of redirect resolutions - maps a title to its redirect
         * target.
         * @param ApiResult $result
         * @return array Array of prefixed_title (string) => Title object
         * @since 1.21
         */
        public function getRedirectTitlesAsResult( $result = null ) {
                $values = array();
                foreach ( $this->getRedirectTitles() as $titleStrFrom => $titleTo ) {
                        $r = array(
                                'from' => strval( $titleStrFrom ),
                                'to' => $titleTo->getPrefixedText(),
                        );
                        if ( $titleTo->hasFragment() ) {
                                $r['tofragment'] = $titleTo->getFragment();
                        }
                        $values[] = $r;
                }
                if ( !empty( $values ) && $result ) {
                        $result->setIndexedTagName( $values, 'r' );
                }

                return $values;
        }

        /**
         * Get a list of title normalizations - maps a title to its normalized
         * version.
         * @return array Array of raw_prefixed_title (string) => prefixed_title (string)
         */
        public function getNormalizedTitles() {
                return $this->mNormalizedTitles;
        }

        /**
         * Get a list of title normalizations - maps a title to its normalized
         * version in the form of result array.
         * @param ApiResult $result
         * @return array Array of raw_prefixed_title (string) => prefixed_title (string)
         * @since 1.21
         */
        public function getNormalizedTitlesAsResult( $result = null ) {
                $values = array();
                foreach ( $this->getNormalizedTitles() as $rawTitleStr => $titleStr ) {
                        $values[] = array(
                                'from' => $rawTitleStr,
                                'to' => $titleStr
                        );
                }
                if ( !empty( $values ) && $result ) {
                        $result->setIndexedTagName( $values, 'n' );
                }

                return $values;
        }

        /**
         * Get a list of title conversions - maps a title to its converted
         * version.
         * @return array Array of raw_prefixed_title (string) => prefixed_title (string)
         */
        public function getConvertedTitles() {
                return $this->mConvertedTitles;
        }

        /**
         * Get a list of title conversions - maps a title to its converted
         * version as a result array.
         * @param ApiResult $result
         * @return array Array of (from, to) strings
         * @since 1.21
         */
        public function getConvertedTitlesAsResult( $result = null ) {
                $values = array();
                foreach ( $this->getConvertedTitles() as $rawTitleStr => $titleStr ) {
                        $values[] = array(
                                'from' => $rawTitleStr,
                                'to' => $titleStr
                        );
                }
                if ( !empty( $values ) && $result ) {
                        $result->setIndexedTagName( $values, 'c' );
                }

                return $values;
        }

        /**
         * Get a list of interwiki titles - maps a title to its interwiki
         * prefix.
         * @return array Array of raw_prefixed_title (string) => interwiki_prefix (string)
         */
        public function getInterwikiTitles() {
                return $this->mInterwikiTitles;
        }

        /**
         * Get a list of interwiki titles - maps a title to its interwiki
         * prefix as result.
         * @param ApiResult $result
         * @param bool $iwUrl
         * @return array Array of raw_prefixed_title (string) => interwiki_prefix (string)
         * @since 1.21
         */
        public function getInterwikiTitlesAsResult( $result = null, $iwUrl = false ) {
                $values = array();
                foreach ( $this->getInterwikiTitles() as $rawTitleStr => $interwikiStr ) {
                        $item = array(
                                'title' => $rawTitleStr,
                                'iw' => $interwikiStr,
                        );
                        if ( $iwUrl ) {
                                $title = Title::newFromText( $rawTitleStr );
                                $item['url'] = $title->getFullURL( '', false, PROTO_CURRENT );
                        }
                        $values[] = $item;
                }
                if ( !empty( $values ) && $result ) {
                        $result->setIndexedTagName( $values, 'i' );
                }

                return $values;
        }

        /**
         * Get an array of invalid/special/missing titles.
         *
         * @param array $invalidChecks List of types of invalid titles to include.
         *   Recognized values are:
         *   - invalidTitles: Titles from $this->getInvalidTitles()
         *   - special: Titles from $this->getSpecialTitles()
         *   - missingIds: ids from $this->getMissingPageIDs()
         *   - missingRevIds: ids from $this->getMissingRevisionIDs()
         *   - missingTitles: Titles from $this->getMissingTitles()
         *   - interwikiTitles: Titles from $this->getInterwikiTitlesAsResult()
         * @return array Array suitable for inclusion in the response
         * @since 1.23
         */
        public function getInvalidTitlesAndRevisions( $invalidChecks = array( 'invalidTitles',
                'special', 'missingIds', 'missingRevIds', 'missingTitles', 'interwikiTitles' )
        ) {
                $result = array();
                if ( in_array( "invalidTitles", $invalidChecks ) ) {
                        self::addValues( $result, $this->getInvalidTitles(), 'invalid', 'title' );
                }
                if ( in_array( "special", $invalidChecks ) ) {
                        self::addValues( $result, $this->getSpecialTitles(), 'special', 'title' );
                }
                if ( in_array( "missingIds", $invalidChecks ) ) {
                        self::addValues( $result, $this->getMissingPageIDs(), 'missing', 'pageid' );
                }
                if ( in_array( "missingRevIds", $invalidChecks ) ) {
                        self::addValues( $result, $this->getMissingRevisionIDs(), 'missing', 'revid' );
                }
                if ( in_array( "missingTitles", $invalidChecks ) ) {
                        self::addValues( $result, $this->getMissingTitles(), 'missing' );
                }
                if ( in_array( "interwikiTitles", $invalidChecks ) ) {
                        self::addValues( $result, $this->getInterwikiTitlesAsResult() );
                }

                return $result;
        }

        /**
         * Get the list of revision IDs (requested with the revids= parameter)
         * @return array Array of revID (int) => pageID (int)
         */
        public function getRevisionIDs() {
                return $this->mGoodRevIDs;
        }

        /**
         * Revision IDs that were not found in the database
         * @return array Array of revision IDs
         */
        public function getMissingRevisionIDs() {
                return $this->mMissingRevIDs;
        }

        /**
         * Revision IDs that were not found in the database as result array.
         * @param ApiResult $result
         * @return array Array of revision IDs
         * @since 1.21
         */
        public function getMissingRevisionIDsAsResult( $result = null ) {
                $values = array();
                foreach ( $this->getMissingRevisionIDs() as $revid ) {
                        $values[$revid] = array(
                                'revid' => $revid
                        );
                }
                if ( !empty( $values ) && $result ) {
                        $result->setIndexedTagName( $values, 'rev' );
                }

                return $values;
        }

        /**
         * Get the list of titles with negative namespace
         * @return array Title
         */
        public function getSpecialTitles() {
                return $this->mSpecialTitles;
        }

        /**
         * Returns the number of revisions (requested with revids= parameter).
         * @return int Number of revisions.
         */
        public function getRevisionCount() {
                return count( $this->getRevisionIDs() );
        }

        /**
         * Populate this PageSet from a list of Titles
         * @param array $titles Array of Title objects
         */
        public function populateFromTitles( $titles ) {
                $this->profileIn();
                $this->initFromTitles( $titles );
                $this->profileOut();
        }

        /**
         * Populate this PageSet from a list of page IDs
         * @param array $pageIDs Array of page IDs
         */
        public function populateFromPageIDs( $pageIDs ) {
                $this->profileIn();
                $this->initFromPageIds( $pageIDs );
                $this->profileOut();
        }

        /**
         * Populate this PageSet from a rowset returned from the database
         * @param DatabaseBase $db
         * @param ResultWrapper $queryResult Query result object
         */
        public function populateFromQueryResult( $db, $queryResult ) {
                $this->profileIn();
                $this->initFromQueryResult( $queryResult );
                $this->profileOut();
        }

        /**
         * Populate this PageSet from a list of revision IDs
         * @param array $revIDs Array of revision IDs
         */
        public function populateFromRevisionIDs( $revIDs ) {
                $this->profileIn();
                $this->initFromRevIDs( $revIDs );
                $this->profileOut();
        }

        /**
         * Extract all requested fields from the row received from the database
         * @param stdClass $row Result row
         */
        public function processDbRow( $row ) {
                // Store Title object in various data structures
                $title = Title::newFromRow( $row );

                $pageId = intval( $row->page_id );
                $this->mAllPages[$row->page_namespace][$row->page_title] = $pageId;
                $this->mTitles[] = $title;

                if ( $this->mResolveRedirects && $row->page_is_redirect == '1' ) {
                        $this->mPendingRedirectIDs[$pageId] = $title;
                } else {
                        $this->mGoodTitles[$pageId] = $title;
                }

                foreach ( $this->mRequestedPageFields as $fieldName => &$fieldValues ) {
                        $fieldValues[$pageId] = $row->$fieldName;
                }
        }

        /**
         * Do not use, does nothing, will be removed
         * @deprecated since 1.21
         */
        public function finishPageSetGeneration() {
                wfDeprecated( __METHOD__, '1.21' );
        }

        /**
         * This method populates internal variables with page information
         * based on the given array of title strings.
         *
         * Steps:
         * #1 For each title, get data from `page` table
         * #2 If page was not found in the DB, store it as missing
         *
         * Additionally, when resolving redirects:
         * #3 If no more redirects left, stop.
         * #4 For each redirect, get its target from the `redirect` table.
         * #5 Substitute the original LinkBatch object with the new list
         * #6 Repeat from step #1
         *
         * @param array $titles Array of Title objects or strings
         */
        private function initFromTitles( $titles ) {
                // Get validated and normalized title objects
                $linkBatch = $this->processTitlesArray( $titles );
                if ( $linkBatch->isEmpty() ) {
                        return;
                }

                $db = $this->getDB();
                $set = $linkBatch->constructSet( 'page', $db );

                // Get pageIDs data from the `page` table
                $this->profileDBIn();
                $res = $db->select( 'page', $this->getPageTableFields(), $set,
                        __METHOD__ );
                $this->profileDBOut();

                // Hack: get the ns:titles stored in array(ns => array(titles)) format
                $this->initFromQueryResult( $res, $linkBatch->data, true ); // process Titles

                // Resolve any found redirects
                $this->resolvePendingRedirects();
        }

        /**
         * Does the same as initFromTitles(), but is based on page IDs instead
         * @param array $pageids Array of page IDs
         */
        private function initFromPageIds( $pageids ) {
                if ( !$pageids ) {
                        return;
                }

                $pageids = array_map( 'intval', $pageids ); // paranoia
                $remaining = array_flip( $pageids );

                $pageids = self::getPositiveIntegers( $pageids );

                $res = null;
                if ( !empty( $pageids ) ) {
                        $set = array(
                                'page_id' => $pageids
                        );
                        $db = $this->getDB();

                        // Get pageIDs data from the `page` table
                        $this->profileDBIn();
                        $res = $db->select( 'page', $this->getPageTableFields(), $set,
                                __METHOD__ );
                        $this->profileDBOut();
                }

                $this->initFromQueryResult( $res, $remaining, false ); // process PageIDs

                // Resolve any found redirects
                $this->resolvePendingRedirects();
        }

        /**
         * Iterate through the result of the query on 'page' table,
         * and for each row create and store title object and save any extra fields requested.
         * @param ResultWrapper $res DB Query result
         * @param array $remaining Array of either pageID or ns/title elements (optional).
         *        If given, any missing items will go to $mMissingPageIDs and $mMissingTitles
         * @param bool $processTitles Must be provided together with $remaining.
         *        If true, treat $remaining as an array of [ns][title]
         *        If false, treat it as an array of [pageIDs]
         */
        private function initFromQueryResult( $res, &$remaining = null, $processTitles = null ) {
                if ( !is_null( $remaining ) && is_null( $processTitles ) ) {
                        ApiBase::dieDebug( __METHOD__, 'Missing $processTitles parameter when $remaining is provided' );
                }

                $usernames = array();
                if ( $res ) {
                        foreach ( $res as $row ) {
                                $pageId = intval( $row->page_id );

                                // Remove found page from the list of remaining items
                                if ( isset( $remaining ) ) {
                                        if ( $processTitles ) {
                                                unset( $remaining[$row->page_namespace][$row->page_title] );
                                        } else {
                                                unset( $remaining[$pageId] );
                                        }
                                }

                                // Store any extra fields requested by modules
                                $this->processDbRow( $row );

                                // Need gender information
                                if ( MWNamespace::hasGenderDistinction( $row->page_namespace ) ) {
                                        $usernames[] = $row->page_title;
                                }
                        }
                }

                if ( isset( $remaining ) ) {
                        // Any items left in the $remaining list are added as missing
                        if ( $processTitles ) {
                                // The remaining titles in $remaining are non-existent pages
                                foreach ( $remaining as $ns => $dbkeys ) {
                                        foreach ( array_keys( $dbkeys ) as $dbkey ) {
                                                $title = Title::makeTitle( $ns, $dbkey );
                                                $this->mAllPages[$ns][$dbkey] = $this->mFakePageId;
                                                $this->mMissingTitles[$this->mFakePageId] = $title;
                                                $this->mFakePageId--;
                                                $this->mTitles[] = $title;

                                                // need gender information
                                                if ( MWNamespace::hasGenderDistinction( $ns ) ) {
                                                        $usernames[] = $dbkey;
                                                }
                                        }
                                }
                        } else {
                                // The remaining pageids do not exist
                                if ( !$this->mMissingPageIDs ) {
                                        $this->mMissingPageIDs = array_keys( $remaining );
                                } else {
                                        $this->mMissingPageIDs = array_merge( $this->mMissingPageIDs, array_keys( $remaining ) );
                                }
                        }
                }

                // Get gender information
                $genderCache = GenderCache::singleton();
                $genderCache->doQuery( $usernames, __METHOD__ );
        }

        /**
         * Does the same as initFromTitles(), but is based on revision IDs
         * instead
         * @param array $revids Array of revision IDs
         */
        private function initFromRevIDs( $revids ) {
                if ( !$revids ) {
                        return;
                }

                $revids = array_map( 'intval', $revids ); // paranoia
                $db = $this->getDB();
                $pageids = array();
                $remaining = array_flip( $revids );

                $revids = self::getPositiveIntegers( $revids );

                if ( !empty( $revids ) ) {
                        $tables = array( 'revision', 'page' );
                        $fields = array( 'rev_id', 'rev_page' );
                        $where = array( 'rev_id' => $revids, 'rev_page = page_id' );

                        // Get pageIDs data from the `page` table
                        $this->profileDBIn();
                        $res = $db->select( $tables, $fields, $where, __METHOD__ );
                        foreach ( $res as $row ) {
                                $revid = intval( $row->rev_id );
                                $pageid = intval( $row->rev_page );
                                $this->mGoodRevIDs[$revid] = $pageid;
                                $pageids[$pageid] = '';
                                unset( $remaining[$revid] );
                        }
                        $this->profileDBOut();
                }

                $this->mMissingRevIDs = array_keys( $remaining );

                // Populate all the page information
                $this->initFromPageIds( array_keys( $pageids ) );
        }

        /**
         * Resolve any redirects in the result if redirect resolution was
         * requested. This function is called repeatedly until all redirects
         * have been resolved.
         */
        private function resolvePendingRedirects() {
                if ( $this->mResolveRedirects ) {
                        $db = $this->getDB();
                        $pageFlds = $this->getPageTableFields();

                        // Repeat until all redirects have been resolved
                        // The infinite loop is prevented by keeping all known pages in $this->mAllPages
                        while ( $this->mPendingRedirectIDs ) {
                                // Resolve redirects by querying the pagelinks table, and repeat the process
                                // Create a new linkBatch object for the next pass
                                $linkBatch = $this->getRedirectTargets();

                                if ( $linkBatch->isEmpty() ) {
                                        break;
                                }

                                $set = $linkBatch->constructSet( 'page', $db );
                                if ( $set === false ) {
                                        break;
                                }

                                // Get pageIDs data from the `page` table
                                $this->profileDBIn();
                                $res = $db->select( 'page', $pageFlds, $set, __METHOD__ );
                                $this->profileDBOut();

                                // Hack: get the ns:titles stored in array(ns => array(titles)) format
                                $this->initFromQueryResult( $res, $linkBatch->data, true );
                        }
                }
        }

        /**
         * Get the targets of the pending redirects from the database
         *
         * Also creates entries in the redirect table for redirects that don't
         * have one.
         * @return LinkBatch
         */
        private function getRedirectTargets() {
                $lb = new LinkBatch();
                $db = $this->getDB();

                $this->profileDBIn();
                $res = $db->select(
                        'redirect',
                        array(
                                'rd_from',
                                'rd_namespace',
                                'rd_fragment',
                                'rd_interwiki',
                                'rd_title'
                        ), array( 'rd_from' => array_keys( $this->mPendingRedirectIDs ) ),
                        __METHOD__
                );
                $this->profileDBOut();
                foreach ( $res as $row ) {
                        $rdfrom = intval( $row->rd_from );
                        $from = $this->mPendingRedirectIDs[$rdfrom]->getPrefixedText();
                        $to = Title::makeTitle(
                                $row->rd_namespace,
                                $row->rd_title,
                                $row->rd_fragment,
                                $row->rd_interwiki
                        );
                        unset( $this->mPendingRedirectIDs[$rdfrom] );
                        if ( !$to->isExternal() && !isset( $this->mAllPages[$row->rd_namespace][$row->rd_title] ) ) {
                                $lb->add( $row->rd_namespace, $row->rd_title );
                        }
                        $this->mRedirectTitles[$from] = $to;
                }

                if ( $this->mPendingRedirectIDs ) {
                        // We found pages that aren't in the redirect table
                        // Add them
                        foreach ( $this->mPendingRedirectIDs as $id => $title ) {
                                $page = WikiPage::factory( $title );
                                $rt = $page->insertRedirect();
                                if ( !$rt ) {
                                        // What the hell. Let's just ignore this
                                        continue;
                                }
                                $lb->addObj( $rt );
                                $this->mRedirectTitles[$title->getPrefixedText()] = $rt;
                                unset( $this->mPendingRedirectIDs[$id] );
                        }
                }

                return $lb;
        }

        /**
         * Get the cache mode for the data generated by this module.
         * All PageSet users should take into account whether this returns a more-restrictive
         * cache mode than the using module itself. For possible return values and other
         * details about cache modes, see ApiMain::setCacheMode()
         *
         * Public caching will only be allowed if *all* the modules that supply
         * data for a given request return a cache mode of public.
         *
         * @param array|null $params
         * @return string
         * @since 1.21
         */
        public function getCacheMode( $params = null ) {
                return $this->mCacheMode;
        }

        /**
         * Given an array of title strings, convert them into Title objects.
         * Alternatively, an array of Title objects may be given.
         * This method validates access rights for the title,
         * and appends normalization values to the output.
         *
         * @param array $titles Array of Title objects or strings
         * @return LinkBatch
         */
        private function processTitlesArray( $titles ) {
                $usernames = array();
                $linkBatch = new LinkBatch();

                foreach ( $titles as $title ) {
                        if ( is_string( $title ) ) {
                                $titleObj = Title::newFromText( $title, $this->mDefaultNamespace );
                        } else {
                                $titleObj = $title;
                        }
                        if ( !$titleObj ) {
                                // Handle invalid titles gracefully
                                $this->mAllPages[0][$title] = $this->mFakePageId;
                                $this->mInvalidTitles[$this->mFakePageId] = $title;
                                $this->mFakePageId--;
                                continue; // There's nothing else we can do
                        }
                        $unconvertedTitle = $titleObj->getPrefixedText();
                        $titleWasConverted = false;
                        if ( $titleObj->isExternal() ) {
                                // This title is an interwiki link.
                                $this->mInterwikiTitles[$unconvertedTitle] = $titleObj->getInterwiki();
                        } else {
                                // Variants checking
                                global $wgContLang;
                                if ( $this->mConvertTitles &&
                                        count( $wgContLang->getVariants() ) > 1 &&
                                        !$titleObj->exists()
                                ) {
                                        // Language::findVariantLink will modify titleText and titleObj into
                                        // the canonical variant if possible
                                        $titleText = is_string( $title ) ? $title : $titleObj->getPrefixedText();
                                        $wgContLang->findVariantLink( $titleText, $titleObj );
                                        $titleWasConverted = $unconvertedTitle !== $titleObj->getPrefixedText();
                                }

                                if ( $titleObj->getNamespace() < 0 ) {
                                        // Handle Special and Media pages
                                        $titleObj = $titleObj->fixSpecialName();
                                        $this->mSpecialTitles[$this->mFakePageId] = $titleObj;
                                        $this->mFakePageId--;
                                } else {
                                        // Regular page
                                        $linkBatch->addObj( $titleObj );
                                }
                        }

                        // Make sure we remember the original title that was
                        // given to us. This way the caller can correlate new
                        // titles with the originally requested when e.g. the
                        // namespace is localized or the capitalization is
                        // different
                        if ( $titleWasConverted ) {
                                $this->mConvertedTitles[$unconvertedTitle] = $titleObj->getPrefixedText();
                                // In this case the page can't be Special.
                                if ( is_string( $title ) && $title !== $unconvertedTitle ) {
                                        $this->mNormalizedTitles[$title] = $unconvertedTitle;
                                }
                        } elseif ( is_string( $title ) && $title !== $titleObj->getPrefixedText() ) {
                                $this->mNormalizedTitles[$title] = $titleObj->getPrefixedText();
                        }

                        // Need gender information
                        if ( MWNamespace::hasGenderDistinction( $titleObj->getNamespace() ) ) {
                                $usernames[] = $titleObj->getText();
                        }
                }
                // Get gender information
                $genderCache = GenderCache::singleton();
                $genderCache->doQuery( $usernames, __METHOD__ );

                return $linkBatch;
        }

        /**
         * Get the database connection (read-only)
         * @return DatabaseBase
         */
        protected function getDB() {
                return $this->mDbSource->getDB();
        }

        /**
         * Returns the input array of integers with all values < 0 removed
         *
         * @param array $array
         * @return array
         */
        private static function getPositiveIntegers( $array ) {
                // bug 25734 API: possible issue with revids validation
                // It seems with a load of revision rows, MySQL gets upset
                // Remove any < 0 integers, as they can't be valid
                foreach ( $array as $i => $int ) {
                        if ( $int < 0 ) {
                                unset( $array[$i] );
                        }
                }

                return $array;
        }

        public function getAllowedParams( $flags = 0 ) {
                $result = array(
                        'titles' => array(
                                ApiBase::PARAM_ISMULTI => true
                        ),
                        'pageids' => array(
                                ApiBase::PARAM_TYPE => 'integer',
                                ApiBase::PARAM_ISMULTI => true
                        ),
                        'revids' => array(
                                ApiBase::PARAM_TYPE => 'integer',
                                ApiBase::PARAM_ISMULTI => true
                        ),
                        'redirects' => false,
                        'converttitles' => false,
                );
                if ( $this->mAllowGenerator ) {
                        if ( $flags & ApiBase::GET_VALUES_FOR_HELP ) {
                                $result['generator'] = array(
                                        ApiBase::PARAM_TYPE => $this->getGenerators()
                                );
                        } else {
                                $result['generator'] = null;
                        }
                }

                return $result;
        }

        private static $generators = null;

        /**
         * Get an array of all available generators
         * @return array
         */
        private function getGenerators() {
                if ( self::$generators === null ) {
                        $query = $this->mDbSource;
                        if ( !( $query instanceof ApiQuery ) ) {
                                // If the parent container of this pageset is not ApiQuery,
                                // we must create it to get module manager
                                $query = $this->getMain()->getModuleManager()->getModule( 'query' );
                        }
                        $gens = array();
                        $mgr = $query->getModuleManager();
                        foreach ( $mgr->getNamesWithClasses() as $name => $class ) {
                                if ( is_subclass_of( $class, 'ApiQueryGeneratorBase' ) ) {
                                        $gens[] = $name;
                                }
                        }
                        sort( $gens );
                        self::$generators = $gens;
                }

                return self::$generators;
        }

        public function getParamDescription() {
                return array(
                        'titles' => 'A list of titles to work on',
                        'pageids' => 'A list of page IDs to work on',
                        'revids' => 'A list of revision IDs to work on',
                        'generator' => array(
                                'Get the list of pages to work on by executing the specified query module.',
                                'NOTE: generator parameter names must be prefixed with a \'g\', see examples'
                        ),
                        'redirects' => 'Automatically resolve redirects',
                        'converttitles' => array(
                                'Convert titles to other variants if necessary. Only works if ' .
                                        'the wiki\'s content language supports variant conversion.',
                                'Languages that support variant conversion include ' .
                                        implode( ', ', LanguageConverter::$languagesWithVariants )
                        ),
                );
        }

        public function getPossibleErrors() {
                return array_merge( parent::getPossibleErrors(), array(
                        array(
                                'code' => 'multisource',
                                'info' => "Cannot use 'pageids' at the same time as 'dataSource'"
                        ),
                        array(
                                'code' => 'multisource',
                                'info' => "Cannot use 'revids' at the same time as 'dataSource'"
                        ),
                        array(
                                'code' => 'badgenerator',
                                'info' => 'Module $generatorName cannot be used as a generator'
                        ),
                ) );
        }
}