Merge "Use adaptive CDN TTLs for page views"

[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 = []; // [ns][dbkey] => page_id or negative when missing
        private $mTitles = [];
        private $mGoodAndMissingPages = []; // [ns][dbkey] => page_id or negative when missing
        private $mGoodPages = []; // [ns][dbkey] => page_id
        private $mGoodTitles = [];
        private $mMissingPages = []; // [ns][dbkey] => fake page_id
        private $mMissingTitles = [];
        /** @var array [fake_page_id] => [ 'title' => $title, 'invalidreason' => $reason ] */
        private $mInvalidTitles = [];
        private $mMissingPageIDs = [];
        private $mRedirectTitles = [];
        private $mSpecialTitles = [];
        private $mNormalizedTitles = [];
        private $mInterwikiTitles = [];
        /** @var Title[] */
        private $mPendingRedirectIDs = [];
        private $mResolvedRedirectTitles = [];
        private $mConvertedTitles = [];
        private $mGoodRevIDs = [];
        private $mLiveRevIDs = [];
        private $mDeletedRevIDs = [];
        private $mMissingRevIDs = [];
        private $mGeneratorData = []; // [ns][dbkey] => data array
        private $mFakePageId = -1;
        private $mCacheMode = 'public';
        private $mRequestedPageFields = [];
        /** @var int */
        private $mDefaultNamespace = NS_MAIN;
        /** @var callable|null */
        private $mRedirectMergePolicy;

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

        /**
         * 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 ) {
                $generatorName = $this->mAllowGenerator ? $this->mParams['generator'] : null;
                if ( isset( $generatorName ) ) {
                        $dbSource = $this->mDbSource;
                        if ( !$dbSource instanceof ApiQuery ) {
                                // If the parent container of this pageset is not ApiQuery, we must create it to run generator
                                $dbSource = $this->getMain()->getModuleManager()->getModule( 'query' );
                        }
                        $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
                        if ( !$isDryRun ) {
                                $generator->executeGenerator( $this );
                                Hooks::run( 'APIQueryGeneratorAfterExecute', [ &$generator, &$this ] );
                        } else {
                                // Prevent warnings from being reported on these parameters
                                $main = $this->getMain();
                                foreach ( $generator->extractRequestParams() as $paramName => $param ) {
                                        $main->markParamsUsed( $generator->encodeParamName( $paramName ) );
                                }
                        }

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

        /**
         * 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 = [
                        'page_namespace' => null,
                        'page_title' => null,
                        'page_id' => null,
                ];

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

                if ( $this->getConfig()->get( 'ContentHandlerUseDB' ) ) {
                        $pageFlds['page_content_model'] = null;
                }

                if ( $this->getConfig()->get( 'PageLanguageUseDB' ) ) {
                        $pageFlds['page_lang'] = null;
                }

                foreach ( LinkCache::getSelectFields() as $field ) {
                        $pageFlds[$field] = null;
                }

                $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 );
        }

        /**
         * Returns an array [ns][dbkey] => page_id for all good titles.
         * @return array
         */
        public function getGoodTitlesByNamespace() {
                return $this->mGoodPages;
        }

        /**
         * 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 );
        }

        /**
         * Returns an array [ns][dbkey] => fake_page_id for all missing titles.
         * fake_page_id is a unique negative number.
         * @return array
         */
        public function getMissingTitlesByNamespace() {
                return $this->mMissingPages;
        }

        /**
         * 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;
        }

        /**
         * Returns an array [ns][dbkey] => page_id for all good and missing titles.
         * @return array
         */
        public function getGoodAndMissingTitlesByNamespace() {
                return $this->mGoodAndMissingPages;
        }

        /**
         * Title objects for good and missing titles.
         * @return array
         */
        public function getGoodAndMissingTitles() {
                return $this->mGoodTitles + $this->mMissingTitles;
        }

        /**
         * Titles that were deemed invalid by Title::newFromText()
         * The array's index will be unique and negative for each item
         * @deprecated since 1.26, use self::getInvalidTitlesAndReasons()
         * @return string[] Array of strings (not Title objects)
         */
        public function getInvalidTitles() {
                wfDeprecated( __METHOD__, '1.26' );
                return array_map( function ( $t ) {
                        return $t['title'];
                }, $this->mInvalidTitles );
        }

        /**
         * Titles that were deemed invalid by Title::newFromText()
         * The array's index will be unique and negative for each item
         * @return array[] Array of arrays with 'title' and 'invalidreason' properties
         */
        public function getInvalidTitlesAndReasons() {
                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 Title[]
         */
        public function getRedirectTitles() {
                return $this->mRedirectTitles;
        }

        /**
         * Get a list of redirect resolutions - maps a title to its redirect
         * target. Includes generator data for redirect source when available.
         * @param ApiResult $result
         * @return array Array of prefixed_title (string) => Title object
         * @since 1.21
         */
        public function getRedirectTitlesAsResult( $result = null ) {
                $values = [];
                foreach ( $this->getRedirectTitles() as $titleStrFrom => $titleTo ) {
                        $r = [
                                'from' => strval( $titleStrFrom ),
                                'to' => $titleTo->getPrefixedText(),
                        ];
                        if ( $titleTo->hasFragment() ) {
                                $r['tofragment'] = $titleTo->getFragment();
                        }
                        if ( $titleTo->isExternal() ) {
                                $r['tointerwiki'] = $titleTo->getInterwiki();
                        }
                        if ( isset( $this->mResolvedRedirectTitles[$titleStrFrom] ) ) {
                                $titleFrom = $this->mResolvedRedirectTitles[$titleStrFrom];
                                $ns = $titleFrom->getNamespace();
                                $dbkey = $titleFrom->getDBkey();
                                if ( isset( $this->mGeneratorData[$ns][$dbkey] ) ) {
                                        $r = array_merge( $this->mGeneratorData[$ns][$dbkey], $r );
                                }
                        }

                        $values[] = $r;
                }
                if ( !empty( $values ) && $result ) {
                        ApiResult::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 ) {
                global $wgContLang;

                $values = [];
                foreach ( $this->getNormalizedTitles() as $rawTitleStr => $titleStr ) {
                        $encode = ( $wgContLang->normalize( $rawTitleStr ) !== $rawTitleStr );
                        $values[] = [
                                'fromencoded' => $encode,
                                'from' => $encode ? rawurlencode( $rawTitleStr ) : $rawTitleStr,
                                'to' => $titleStr
                        ];
                }
                if ( !empty( $values ) && $result ) {
                        ApiResult::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 = [];
                foreach ( $this->getConvertedTitles() as $rawTitleStr => $titleStr ) {
                        $values[] = [
                                'from' => $rawTitleStr,
                                'to' => $titleStr
                        ];
                }
                if ( !empty( $values ) && $result ) {
                        ApiResult::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 = [];
                foreach ( $this->getInterwikiTitles() as $rawTitleStr => $interwikiStr ) {
                        $item = [
                                'title' => $rawTitleStr,
                                'iw' => $interwikiStr,
                        ];
                        if ( $iwUrl ) {
                                $title = Title::newFromText( $rawTitleStr );
                                $item['url'] = $title->getFullURL( '', false, PROTO_CURRENT );
                        }
                        $values[] = $item;
                }
                if ( !empty( $values ) && $result ) {
                        ApiResult::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 and reasons from $this->getInvalidTitlesAndReasons()
         *   - 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 = [ 'invalidTitles',
                'special', 'missingIds', 'missingRevIds', 'missingTitles', 'interwikiTitles' ]
        ) {
                $result = [];
                if ( in_array( 'invalidTitles', $invalidChecks ) ) {
                        self::addValues( $result, $this->getInvalidTitlesAndReasons(), [ 'invalid' ] );
                }
                if ( in_array( 'special', $invalidChecks ) ) {
                        $known = [];
                        $unknown = [];
                        foreach ( $this->getSpecialTitles() as $title ) {
                                if ( $title->isKnown() ) {
                                        $known[] = $title;
                                } else {
                                        $unknown[] = $title;
                                }
                        }
                        self::addValues( $result, $unknown, [ 'special', 'missing' ] );
                        self::addValues( $result, $known, [ 'special' ] );
                }
                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 ) ) {
                        $known = [];
                        $unknown = [];
                        foreach ( $this->getMissingTitles() as $title ) {
                                if ( $title->isKnown() ) {
                                        $known[] = $title;
                                } else {
                                        $unknown[] = $title;
                                }
                        }
                        self::addValues( $result, $unknown, [ 'missing' ] );
                        self::addValues( $result, $known, [ 'missing', 'known' ] );
                }
                if ( in_array( 'interwikiTitles', $invalidChecks ) ) {
                        self::addValues( $result, $this->getInterwikiTitlesAsResult() );
                }

                return $result;
        }

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

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

        /**
         * Get the list of revision IDs that were associated with deleted titles.
         * @return array Array of revID (int) => pageID (int)
         */
        public function getDeletedRevisionIDs() {
                return $this->mDeletedRevIDs;
        }

        /**
         * 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 = [];
                foreach ( $this->getMissingRevisionIDs() as $revid ) {
                        $values[$revid] = [
                                'revid' => $revid
                        ];
                }
                if ( !empty( $values ) && $result ) {
                        ApiResult::setIndexedTagName( $values, 'rev' );
                }

                return $values;
        }

        /**
         * Get the list of titles with negative namespace
         * @return 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->initFromTitles( $titles );
        }

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

        /**
         * Populate this PageSet from a rowset returned from the database
         *
         * Note that the query result must include the columns returned by
         * $this->getPageTableFields().
         *
         * @param IDatabase $db
         * @param ResultWrapper $queryResult Query result object
         */
        public function populateFromQueryResult( $db, $queryResult ) {
                $this->initFromQueryResult( $queryResult );
        }

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

        /**
         * 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 );

                LinkCache::singleton()->addGoodLinkObjFromRow( $title, $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 {
                        $this->mGoodPages[$row->page_namespace][$row->page_title] = $pageId;
                        $this->mGoodAndMissingPages[$row->page_namespace][$row->page_title] = $pageId;
                        $this->mGoodTitles[$pageId] = $title;
                }

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

        /**
         * 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
                $res = $db->select( 'page', $this->getPageTableFields(), $set,
                        __METHOD__ );

                // Hack: get the ns:titles stored in [ ns => [ 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 = [
                                'page_id' => $pageids
                        ];
                        $db = $this->getDB();

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

                $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 = [];
                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
                                $linkCache = LinkCache::singleton();
                                foreach ( $remaining as $ns => $dbkeys ) {
                                        foreach ( array_keys( $dbkeys ) as $dbkey ) {
                                                $title = Title::makeTitle( $ns, $dbkey );
                                                $linkCache->addBadLinkObj( $title );
                                                $this->mAllPages[$ns][$dbkey] = $this->mFakePageId;
                                                $this->mMissingPages[$ns][$dbkey] = $this->mFakePageId;
                                                $this->mGoodAndMissingPages[$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 = [];
                $remaining = array_flip( $revids );

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

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

                        // Get pageIDs data from the `page` table
                        $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;
                                $this->mLiveRevIDs[$revid] = $pageid;
                                $pageids[$pageid] = '';
                                unset( $remaining[$revid] );
                        }
                }

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

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

                // If the user can see deleted revisions, pull out the corresponding
                // titles from the archive table and include them too. We ignore
                // ar_page_id because deleted revisions are tied by title, not page_id.
                if ( !empty( $this->mMissingRevIDs ) && $this->getUser()->isAllowed( 'deletedhistory' ) ) {
                        $remaining = array_flip( $this->mMissingRevIDs );
                        $tables = [ 'archive' ];
                        $fields = [ 'ar_rev_id', 'ar_namespace', 'ar_title' ];
                        $where = [ 'ar_rev_id' => $this->mMissingRevIDs ];

                        $res = $db->select( $tables, $fields, $where, __METHOD__ );
                        $titles = [];
                        foreach ( $res as $row ) {
                                $revid = intval( $row->ar_rev_id );
                                $titles[$revid] = Title::makeTitle( $row->ar_namespace, $row->ar_title );
                                unset( $remaining[$revid] );
                        }

                        $this->initFromTitles( $titles );

                        foreach ( $titles as $revid => $title ) {
                                $ns = $title->getNamespace();
                                $dbkey = $title->getDBkey();

                                // Handle converted titles
                                if ( !isset( $this->mAllPages[$ns][$dbkey] ) &&
                                        isset( $this->mConvertedTitles[$title->getPrefixedText()] )
                                ) {
                                        $title = Title::newFromText( $this->mConvertedTitles[$title->getPrefixedText()] );
                                        $ns = $title->getNamespace();
                                        $dbkey = $title->getDBkey();
                                }

                                if ( isset( $this->mAllPages[$ns][$dbkey] ) ) {
                                        $this->mGoodRevIDs[$revid] = $this->mAllPages[$ns][$dbkey];
                                        $this->mDeletedRevIDs[$revid] = $this->mAllPages[$ns][$dbkey];
                                } else {
                                        $remaining[$revid] = true;
                                }
                        }

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

        /**
         * 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
                                $res = $db->select( 'page', $pageFlds, $set, __METHOD__ );

                                // Hack: get the ns:titles stored in [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();

                $res = $db->select(
                        'redirect',
                        [
                                'rd_from',
                                'rd_namespace',
                                'rd_fragment',
                                'rd_interwiki',
                                'rd_title'
                        ], [ 'rd_from' => array_keys( $this->mPendingRedirectIDs ) ],
                        __METHOD__
                );
                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
                        );
                        $this->mResolvedRedirectTitles[$from] = $this->mPendingRedirectIDs[$rdfrom];
                        unset( $this->mPendingRedirectIDs[$rdfrom] );
                        if ( $to->isExternal() ) {
                                $this->mInterwikiTitles[$to->getPrefixedText()] = $to->getInterwiki();
                        } elseif ( !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 );
                                $from = $title->getPrefixedText();
                                $this->mResolvedRedirectTitles[$from] = $title;
                                $this->mRedirectTitles[$from] = $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 = [];
                $linkBatch = new LinkBatch();

                foreach ( $titles as $title ) {
                        if ( is_string( $title ) ) {
                                try {
                                        $titleObj = Title::newFromTextThrow( $title, $this->mDefaultNamespace );
                                } catch ( MalformedTitleException $ex ) {
                                        // Handle invalid titles gracefully
                                        $this->mAllPages[0][$title] = $this->mFakePageId;
                                        $this->mInvalidTitles[$this->mFakePageId] = [
                                                'title' => $title,
                                                'invalidreason' => $ex->getMessage(),
                                        ];
                                        $this->mFakePageId--;
                                        continue; // There's nothing else we can do
                                }
                        } else {
                                $titleObj = $title;
                        }
                        $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;
        }

        /**
         * Set data for a title.
         *
         * This data may be extracted into an ApiResult using
         * self::populateGeneratorData. This should generally be limited to
         * data that is likely to be particularly useful to end users rather than
         * just being a dump of everything returned in non-generator mode.
         *
         * Redirects here will *not* be followed, even if 'redirects' was
         * specified, since in the case of multiple redirects we can't know which
         * source's data to use on the target.
         *
         * @param Title $title
         * @param array $data
         */
        public function setGeneratorData( Title $title, array $data ) {
                $ns = $title->getNamespace();
                $dbkey = $title->getDBkey();
                $this->mGeneratorData[$ns][$dbkey] = $data;
        }

        /**
         * Controls how generator data about a redirect source is merged into
         * the generator data for the redirect target. When not set no data
         * is merged. Note that if multiple titles redirect to the same target
         * the order of operations is undefined.
         *
         * Example to include generated data from redirect in target, prefering
         * the data generated for the destination when there is a collision:
         * @code
         *   $pageSet->setRedirectMergePolicy( function( array $current, array $new ) {
         *       return $current + $new;
         *   } );
         * @endcode
         *
         * @param callable|null $callable Recieves two array arguments, first the
         *  generator data for the redirect target and second the generator data
         *  for the redirect source. Returns the resulting generator data to use
         *  for the redirect target.
         */
        public function setRedirectMergePolicy( $callable ) {
                $this->mRedirectMergePolicy = $callable;
        }

        /**
         * Populate the generator data for all titles in the result
         *
         * The page data may be inserted into an ApiResult object or into an
         * associative array. The $path parameter specifies the path within the
         * ApiResult or array to find the "pages" node.
         *
         * The "pages" node itself must be an associative array mapping the page ID
         * or fake page ID values returned by this pageset (see
         * self::getAllTitlesByNamespace() and self::getSpecialTitles()) to
         * associative arrays of page data. Each of those subarrays will have the
         * data from self::setGeneratorData() merged in.
         *
         * Data that was set by self::setGeneratorData() for pages not in the
         * "pages" node will be ignored.
         *
         * @param ApiResult|array &$result
         * @param array $path
         * @return bool Whether the data fit
         */
        public function populateGeneratorData( &$result, array $path = [] ) {
                if ( $result instanceof ApiResult ) {
                        $data = $result->getResultData( $path );
                        if ( $data === null ) {
                                return true;
                        }
                } else {
                        $data = &$result;
                        foreach ( $path as $key ) {
                                if ( !isset( $data[$key] ) ) {
                                        // Path isn't in $result, so nothing to add, so everything
                                        // "fits"
                                        return true;
                                }
                                $data = &$data[$key];
                        }
                }
                foreach ( $this->mGeneratorData as $ns => $dbkeys ) {
                        if ( $ns === -1 ) {
                                $pages = [];
                                foreach ( $this->mSpecialTitles as $id => $title ) {
                                        $pages[$title->getDBkey()] = $id;
                                }
                        } else {
                                if ( !isset( $this->mAllPages[$ns] ) ) {
                                        // No known titles in the whole namespace. Skip it.
                                        continue;
                                }
                                $pages = $this->mAllPages[$ns];
                        }
                        foreach ( $dbkeys as $dbkey => $genData ) {
                                if ( !isset( $pages[$dbkey] ) ) {
                                        // Unknown title. Forget it.
                                        continue;
                                }
                                $pageId = $pages[$dbkey];
                                if ( !isset( $data[$pageId] ) ) {
                                        // $pageId didn't make it into the result. Ignore it.
                                        continue;
                                }

                                if ( $result instanceof ApiResult ) {
                                        $path2 = array_merge( $path, [ $pageId ] );
                                        foreach ( $genData as $key => $value ) {
                                                if ( !$result->addValue( $path2, $key, $value ) ) {
                                                        return false;
                                                }
                                        }
                                } else {
                                        $data[$pageId] = array_merge( $data[$pageId], $genData );
                                }
                        }
                }

                // Merge data generated about redirect titles into the redirect destination
                if ( $this->mRedirectMergePolicy ) {
                        foreach ( $this->mResolvedRedirectTitles as $titleFrom ) {
                                $dest = $titleFrom;
                                while ( isset( $this->mRedirectTitles[$dest->getPrefixedText()] ) ) {
                                        $dest = $this->mRedirectTitles[$dest->getPrefixedText()];
                                }
                                $fromNs = $titleFrom->getNamespace();
                                $fromDBkey = $titleFrom->getDBkey();
                                $toPageId = $dest->getArticleID();
                                if ( isset( $data[$toPageId] ) &&
                                        isset( $this->mGeneratorData[$fromNs][$fromDBkey] )
                                ) {
                                        // It is necesary to set both $data and add to $result, if an ApiResult,
                                        // to ensure multiple redirects to the same destination are all merged.
                                        $data[$toPageId] = call_user_func(
                                                $this->mRedirectMergePolicy,
                                                $data[$toPageId],
                                                $this->mGeneratorData[$fromNs][$fromDBkey]
                                        );
                                        if ( $result instanceof ApiResult ) {
                                                if ( !$result->addValue( $path, $toPageId, $data[$toPageId], ApiResult::OVERRIDE ) ) {
                                                        return false;
                                                }
                                        }
                                }
                        }
                }

                return true;
        }

        /**
         * Get the database connection (read-only)
         * @return Database
         */
        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 = [
                        'titles' => [
                                ApiBase::PARAM_ISMULTI => true,
                                ApiBase::PARAM_HELP_MSG => 'api-pageset-param-titles',
                        ],
                        'pageids' => [
                                ApiBase::PARAM_TYPE => 'integer',
                                ApiBase::PARAM_ISMULTI => true,
                                ApiBase::PARAM_HELP_MSG => 'api-pageset-param-pageids',
                        ],
                        'revids' => [
                                ApiBase::PARAM_TYPE => 'integer',
                                ApiBase::PARAM_ISMULTI => true,
                                ApiBase::PARAM_HELP_MSG => 'api-pageset-param-revids',
                        ],
                        'generator' => [
                                ApiBase::PARAM_TYPE => null,
                                ApiBase::PARAM_HELP_MSG => 'api-pageset-param-generator',
                                ApiBase::PARAM_SUBMODULE_PARAM_PREFIX => 'g',
                        ],
                        'redirects' => [
                                ApiBase::PARAM_DFLT => false,
                                ApiBase::PARAM_HELP_MSG => $this->mAllowGenerator
                                        ? 'api-pageset-param-redirects-generator'
                                        : 'api-pageset-param-redirects-nogenerator',
                        ],
                        'converttitles' => [
                                ApiBase::PARAM_DFLT => false,
                                ApiBase::PARAM_HELP_MSG => [
                                        'api-pageset-param-converttitles',
                                        new DeferredStringifier(
                                                function ( IContextSource $context ) {
                                                        return $context->getLanguage()
                                                                ->commaList( LanguageConverter::$languagesWithVariants );
                                                },
                                                $this
                                        )
                                ],
                        ],
                ];

                if ( !$this->mAllowGenerator ) {
                        unset( $result['generator'] );
                } elseif ( $flags & ApiBase::GET_VALUES_FOR_HELP ) {
                        $result['generator'][ApiBase::PARAM_TYPE] = 'submodule';
                        $result['generator'][ApiBase::PARAM_SUBMODULE_MAP] = $this->getGenerators();
                }

                return $result;
        }

        protected function handleParamNormalization( $paramName, $value, $rawValue ) {
                parent::handleParamNormalization( $paramName, $value, $rawValue );

                if ( $paramName === 'titles' ) {
                        // For the 'titles' parameter, we want to split it like ApiBase would
                        // and add any changed titles to $this->mNormalizedTitles
                        $value = $this->explodeMultiValue( $value, self::LIMIT_SML2 + 1 );
                        $l = count( $value );
                        $rawValue = $this->explodeMultiValue( $rawValue, $l );
                        for ( $i = 0; $i < $l; $i++ ) {
                                if ( $value[$i] !== $rawValue[$i] ) {
                                        $this->mNormalizedTitles[$rawValue[$i]] = $value[$i];
                                }
                        }
                }
        }

        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 = [];
                        $prefix = $query->getModulePath() . '+';
                        $mgr = $query->getModuleManager();
                        foreach ( $mgr->getNamesWithClasses() as $name => $class ) {
                                if ( is_subclass_of( $class, 'ApiQueryGeneratorBase' ) ) {
                                        $gens[$name] = $prefix . $name;
                                }
                        }
                        ksort( $gens );
                        self::$generators = $gens;
                }

                return self::$generators;
        }
}