Merge "doc: SpanInterface: more dev-friendly comments"

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

<?php
/**
 * 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
 */

namespace MediaWiki\Api;

use MediaWiki\Api\Validator\SubmoduleDef;
use MediaWiki\Cache\GenderCache;
use MediaWiki\Cache\LinkBatch;
use MediaWiki\Cache\LinkBatchFactory;
use MediaWiki\Cache\LinkCache;
use MediaWiki\Context\DerivativeContext;
use MediaWiki\Language\ILanguageConverter;
use MediaWiki\Language\Language;
use MediaWiki\Language\LanguageConverter;
use MediaWiki\Linker\LinkTarget;
use MediaWiki\MainConfigNames;
use MediaWiki\MediaWikiServices;
use MediaWiki\Message\Message;
use MediaWiki\Page\PageIdentity;
use MediaWiki\Page\PageReference;
use MediaWiki\Request\FauxRequest;
use MediaWiki\SpecialPage\RedirectSpecialArticle;
use MediaWiki\SpecialPage\SpecialPageFactory;
use MediaWiki\Title\MalformedTitleException;
use MediaWiki\Title\NamespaceInfo;
use MediaWiki\Title\Title;
use MediaWiki\Title\TitleFactory;
use stdClass;
use Wikimedia\ParamValidator\ParamValidator;
use Wikimedia\Rdbms\IReadableDatabase;
use Wikimedia\Rdbms\IResultWrapper;

/**
 * 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
         */
        private const DISABLE_GENERATORS = 1;

        /** @var ApiBase used for getDb() call */
        private $mDbSource;

        /** @var array */
        private $mParams;

        /** @var bool */
        private $mResolveRedirects;

        /** @var bool */
        private $mConvertTitles;

        /** @var bool */
        private $mAllowGenerator;

        /** @var array<int,array<string,int>> [ns][dbkey] => page_id or negative when missing */
        private $mAllPages = [];

        /** @var Title[] */
        private $mTitles = [];

        /** @var array<int,array<string,int>> [ns][dbkey] => page_id or negative when missing */
        private $mGoodAndMissingPages = [];

        /** @var array<int,array<string,int>> [ns][dbkey] => page_id */
        private $mGoodPages = [];

        /** @var array<int,Title> */
        private $mGoodTitles = [];

        /** @var array<int,array<string,int>> [ns][dbkey] => fake page_id */
        private $mMissingPages = [];

        /** @var array<int,Title> */
        private $mMissingTitles = [];

        /** @var array<int,array{title:string,invalidreason:array}> [fake_page_id] => [ 'title' => $title, 'invalidreason' => $reason ] */
        private $mInvalidTitles = [];

        /** @var int[] */
        private $mMissingPageIDs = [];

        /** @var array<string,Title> */
        private $mRedirectTitles = [];

        /** @var array<int,Title> */
        private $mSpecialTitles = [];

        /** @var array<int,array<string,int>> separate from mAllPages to avoid breaking getAllTitlesByNamespace() */
        private $mAllSpecials = [];

        /** @var array<string,string> */
        private $mNormalizedTitles = [];

        /** @var array<string,string> */
        private $mInterwikiTitles = [];

        /** @var array<int,Title> */
        private $mPendingRedirectIDs = [];

        /** @var array<string,array{Title,Title}> [dbkey] => [ Title $from, Title $to ] */
        private $mPendingRedirectSpecialPages = [];

        /** @var array<string,Title> */
        private $mResolvedRedirectTitles = [];

        /** @var array<string,string> */
        private $mConvertedTitles = [];

        /** @var array<int,int> Array of revID (int) => pageID (int) */
        private $mGoodRevIDs = [];

        /** @var array<int,int> Array of revID (int) => pageID (int) */
        private $mLiveRevIDs = [];

        /** @var array<int,int> Array of revID (int) => pageID (int) */
        private $mDeletedRevIDs = [];

        /** @var int[] */
        private $mMissingRevIDs = [];

        /** @var array<int,array<string,array>> [ns][dbkey] => data array */
        private $mGeneratorData = [];

        /** @var int */
        private $mFakePageId = -1;

        /** @var string */
        private $mCacheMode = 'public';

        /** @var array<string,array<int,mixed>> [fieldName][pageId] => value */
        private $mRequestedPageFields = [];

        /** @var int */
        private $mDefaultNamespace;

        /** @var callable|null */
        private $mRedirectMergePolicy;

        /** @var array<string,string>|null see getGenerators() */
        private static $generators = null;

        private Language $contentLanguage;
        private LinkCache $linkCache;
        private NamespaceInfo $namespaceInfo;
        private GenderCache $genderCache;
        private LinkBatchFactory $linkBatchFactory;
        private TitleFactory $titleFactory;
        private ILanguageConverter $languageConverter;
        private SpecialPageFactory $specialPageFactory;

        /**
         * 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|null $name If given, name of the value
         */
        private static function addValues( array &$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 & self::DISABLE_GENERATORS ) == 0;
                $this->mDefaultNamespace = $defaultNamespace;

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

                // Needs service injection - T283314
                $services = MediaWikiServices::getInstance();
                $this->contentLanguage = $services->getContentLanguage();
                $this->linkCache = $services->getLinkCache();
                $this->namespaceInfo = $services->getNamespaceInfo();
                $this->genderCache = $services->getGenderCache();
                $this->linkBatchFactory = $services->getLinkBatchFactory();
                $this->titleFactory = $services->getTitleFactory();
                $this->languageConverter = $services->getLanguageConverterFactory()
                        ->getLanguageConverter( $this->contentLanguage );
                $this->specialPageFactory = $services->getSpecialPageFactory();
        }

        /**
         * 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 ( $generatorName !== null ) {
                        $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->dieWithError( [ 'apierror-badgenerator-unknown', $generatorName ], 'badgenerator' );
                        }
                        if ( !$generator instanceof ApiQueryGeneratorBase ) {
                                $this->dieWithError( [ 'apierror-badgenerator-notgenerator', $generatorName ], 'badgenerator' );
                        }
                        // Create a temporary pageset to store generator's output,
                        // add any additional fields generator may need, and execute pageset to populate titles/pageids
                        // @phan-suppress-next-line PhanTypeMismatchArgumentNullable T240141
                        $tmpPageSet = new ApiPageSet( $dbSource, self::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 );

                                // @phan-suppress-next-line PhanTypeMismatchArgumentNullable T240141
                                $this->getHookRunner()->onAPIQueryGeneratorAfterExecute( $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 ( $dataSource !== null ) {
                                        $this->dieWithError(
                                                [
                                                        'apierror-invalidparammix-cannotusewith',
                                                        $this->encodeParamName( 'pageids' ),
                                                        $this->encodeParamName( $dataSource )
                                                ],
                                                'multisource'
                                        );
                                }
                                $dataSource = 'pageids';
                        }
                        if ( isset( $this->mParams['revids'] ) ) {
                                if ( $dataSource !== null ) {
                                        $this->dieWithError(
                                                [
                                                        'apierror-invalidparammix-cannotusewith',
                                                        $this->encodeParamName( 'revids' ),
                                                        $this->encodeParamName( $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->addWarning( 'apiwarn-redirectsandrevids' );
                                                }
                                                $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 A page table field, e.g. "page_touched"
         */
        public function requestField( $fieldName ) {
                $this->mRequestedPageFields[$fieldName] = [];
        }

        /**
         * Get the values of one of the previously requested page table fields. Can only be used
         * after execute() and only for fields previously requested through requestField().
         * @param string $fieldName A page table field, e.g. "page_touched"
         * @return array<int,mixed> Field values per page id, initialized only after execute()
         */
        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 string[] 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;
                }

                $pageFlds['page_content_model'] = null;

                if ( $this->getConfig()->get( MainConfigNames::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<int,array<string,int>>
         */
        public function getAllTitlesByNamespace() {
                return $this->mAllPages;
        }

        /**
         * All existing and missing pages including redirects.
         * Does not include special pages, interwiki links, and invalid titles.
         * If redirects are resolved, both the redirect and the target will be included here.
         *
         * @deprecated since 1.37, use getPages() instead, hard-deprecated since 1.43.
         * @return Title[]
         */
        public function getTitles() {
                wfDeprecated( __METHOD__, '1.37' );
                return $this->mTitles;
        }

        /**
         * All existing and missing pages including redirects.
         * Does not include special pages, interwiki links, and invalid titles.
         * If redirects are resolved, both the redirect and the target will be included here.
         *
         * @since 1.37
         * @return PageIdentity[]
         */
        public function getPages(): array {
                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<int,array<string,int>>
         */
        public function getGoodTitlesByNamespace() {
                return $this->mGoodPages;
        }

        /**
         * Title objects that were found in the database, including redirects.
         * If redirects are resolved, this will include existing redirect targets.
         * @deprecated since 1.37, use getGoodPages() instead, hard-deprecated since 1.43.
         * @return array<int,Title> Array page_id (int) => Title (obj)
         */
        public function getGoodTitles() {
                wfDeprecated( __METHOD__, '1.37' );
                return $this->mGoodTitles;
        }

        /**
         * Pages that were found in the database, including redirects.
         * If redirects are resolved, this will include existing redirect targets.
         * @since 1.37
         * @return array<int,PageIdentity> Array page_id (int) => PageIdentity (obj)
         */
        public function getGoodPages(): array {
                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<int,array<string,int>>
         */
        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.
         * If redirects are resolved, this will include missing redirect targets.
         * @deprecated since 1.37, use getMissingPages instead, hard-deprecated since 1.43.
         * @return array<int,Title>
         */
        public function getMissingTitles() {
                wfDeprecated( __METHOD__, '1.37' );
                return $this->mMissingTitles;
        }

        /**
         * Pages that were NOT found in the database.
         * The array's index will be negative for each item.
         * If redirects are resolved, this will include missing redirect targets.
         * @since 1.37
         * @return PageIdentity[]
         */
        public function getMissingPages(): array {
                return $this->mMissingTitles;
        }

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

        /**
         * Title objects for good and missing titles.
         * @deprecated since 1.37, use getGoodAndMissingPages() instead, hard-deprecated since 1.43.
         * @return Title[]
         */
        public function getGoodAndMissingTitles() {
                wfDeprecated( __METHOD__, '1.37' );
                return $this->mGoodTitles + $this->mMissingTitles;
        }

        /**
         * Pages for good and missing titles.
         * @since 1.37
         * @return PageIdentity[]
         */
        public function getGoodAndMissingPages(): array {
                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
         * @return array<int,array{title:string,invalidreason:array}>
         */
        public function getInvalidTitlesAndReasons() {
                return $this->mInvalidTitles;
        }

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

        /**
         * Get a list of redirect resolutions - maps a title to its redirect
         * target.
         * @deprecated since 1.37, use getRedirectTargets instead, hard-deprecated since 1.43.
         * @return array<string,Title>
         */
        public function getRedirectTitles() {
                wfDeprecated( __METHOD__, '1.37' );
                return $this->mRedirectTitles;
        }

        /**
         * Get a list of redirect resolutions - maps a title to its redirect
         * target.
         * @since 1.37
         * @return LinkTarget[]
         */
        public function getRedirectTargets(): array {
                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|null $result
         * @return string[][]
         * @since 1.21
         */
        public function getRedirectTitlesAsResult( $result = null ) {
                $values = [];
                foreach ( $this->mRedirectTitles 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 ( $values && $result ) {
                        ApiResult::setIndexedTagName( $values, 'r' );
                }

                return $values;
        }

        /**
         * Get a list of title normalizations - maps a title to its normalized
         * version.
         * @return array<string,string> 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|null $result
         * @return string[][]
         * @since 1.21
         */
        public function getNormalizedTitlesAsResult( $result = null ) {
                $values = [];
                foreach ( $this->getNormalizedTitles() as $rawTitleStr => $titleStr ) {
                        $encode = $this->contentLanguage->normalize( $rawTitleStr ) !== $rawTitleStr;
                        $values[] = [
                                'fromencoded' => $encode,
                                'from' => $encode ? rawurlencode( $rawTitleStr ) : $rawTitleStr,
                                'to' => $titleStr
                        ];
                }
                if ( $values && $result ) {
                        ApiResult::setIndexedTagName( $values, 'n' );
                }

                return $values;
        }

        /**
         * Get a list of title conversions - maps a title to its converted
         * version.
         * @return string[] 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|null $result
         * @return string[][] 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 ( $values && $result ) {
                        ApiResult::setIndexedTagName( $values, 'c' );
                }

                return $values;
        }

        /**
         * Get a list of interwiki titles - maps a title to its interwiki
         * prefix.
         * @return string[] 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|null $result
         * @param bool $iwUrl
         * @return 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 = $this->titleFactory->newFromText( $rawTitleStr );
                                $item['url'] = $title->getFullURL( '', false, PROTO_CURRENT );
                        }
                        $values[] = $item;
                }
                if ( $values && $result ) {
                        ApiResult::setIndexedTagName( $values, 'i' );
                }

                return $values;
        }

        /**
         * Get an array of invalid/special/missing titles.
         *
         * @param string[] $invalidChecks List of types of invalid titles to include.
         *   Recognized values are:
         *   - invalidTitles: Titles and reasons from $this->getInvalidTitlesAndReasons()
         *   - special: Titles from $this->getSpecialPages()
         *   - missingIds: ids from $this->getMissingPageIDs()
         *   - missingRevIds: ids from $this->getMissingRevisionIDs()
         *   - missingTitles: Titles from $this->getMissingPages()
         *   - 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->mSpecialTitles 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->mMissingTitles 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 int[] 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 int[] 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 int[] Array of revID (int) => pageID (int)
         */
        public function getDeletedRevisionIDs() {
                return $this->mDeletedRevIDs;
        }

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

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

                return $values;
        }

        /**
         * Get the list of titles with negative namespace
         * @deprecated since 1.37, use getSpecialPages() instead, hard-deprecated since 1.43.
         * @return Title[]
         */
        public function getSpecialTitles() {
                wfDeprecated( __METHOD__, '1.37' );
                return $this->mSpecialTitles;
        }

        /**
         * Get the list of pages with negative namespace
         * @since 1.37
         * @return PageReference[]
         */
        public function getSpecialPages(): array {
                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
         * @param string[]|LinkTarget[]|PageReference[] $titles
         */
        public function populateFromTitles( $titles ) {
                $this->initFromTitles( $titles );
        }

        /**
         * Populate this PageSet from a list of page IDs
         * @param int[] $pageIDs
         */
        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 IReadableDatabase $db Unused since 2011
         * @param IResultWrapper $queryResult
         */
        public function populateFromQueryResult( $db, $queryResult ) {
                $this->initFromQueryResult( $queryResult );
        }

        /**
         * Populate this PageSet from a list of revision IDs
         * @param int[] $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 = $this->titleFactory->newFromRow( $row );

                $this->linkCache->addGoodLinkObjFromRow( $title, $row );

                $pageId = (int)$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 string[]|LinkTarget[]|PageReference[] $titles
         */
        private function initFromTitles( $titles ) {
                // Get validated and normalized title objects
                $linkBatch = $this->processTitlesArray( $titles );
                if ( $linkBatch->isEmpty() ) {
                        // There might be special-page redirects
                        $this->resolvePendingRedirects();
                        return;
                }

                $db = $this->getDB();

                // Get pageIDs data from the `page` table
                $res = $db->newSelectQueryBuilder()
                        ->select( $this->getPageTableFields() )
                        ->from( 'page' )
                        ->where( $linkBatch->constructSet( 'page', $db ) )
                        ->caller( __METHOD__ )
                        ->fetchResultSet();

                // 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 int[] $pageids
         * @param bool $filterIds Whether the IDs need filtering
         */
        private function initFromPageIds( $pageids, $filterIds = true ) {
                if ( !$pageids ) {
                        return;
                }

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

                if ( $filterIds ) {
                        $pageids = $this->filterIDs( [ [ 'page', 'page_id' ] ], $pageids );
                }

                $res = null;
                if ( $pageids ) {
                        $db = $this->getDB();

                        // Get pageIDs data from the `page` table
                        $res = $db->newSelectQueryBuilder()
                                ->select( $this->getPageTableFields() )
                                ->from( 'page' )
                                ->where( [ 'page_id' => $pageids ] )
                                ->caller( __METHOD__ )
                                ->fetchResultSet();
                }

                $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 IResultWrapper|null $res DB Query result
         * @param array|null &$remaining Array of either pageID or ns/title elements (optional).
         *        If given, any missing items will go to $mMissingPageIDs and $mMissingTitles
         * @param bool|null $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 ( $remaining !== null && $processTitles === null ) {
                        ApiBase::dieDebug( __METHOD__, 'Missing $processTitles parameter when $remaining is provided' );
                }

                $usernames = [];
                if ( $res ) {
                        foreach ( $res as $row ) {
                                $pageId = (int)$row->page_id;

                                // Remove found page from the list of remaining items
                                if ( $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 ( $this->namespaceInfo->hasGenderDistinction( $row->page_namespace ) ) {
                                        $usernames[] = $row->page_title;
                                }
                        }
                }

                if ( $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 ( $dbkeys as $dbkey => $_ ) {
                                                $title = $this->titleFactory->makeTitle( $ns, $dbkey );
                                                $this->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 ( $this->namespaceInfo->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
                $this->genderCache->doQuery( $usernames, __METHOD__ );
        }

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

                $revids = array_map( 'intval', $revids ); // paranoia
                $db = $this->getDB();
                $pageids = [];
                $remaining = array_fill_keys( $revids, true );

                $revids = $this->filterIDs( [ [ 'revision', 'rev_id' ], [ 'archive', 'ar_rev_id' ] ], $revids );
                $goodRemaining = array_fill_keys( $revids, true );

                if ( $revids ) {
                        $fields = [ 'rev_id', 'rev_page' ];

                        // Get pageIDs data from the `page` table
                        $res = $db->newSelectQueryBuilder()
                                ->select( $fields )
                                ->from( 'page' )
                                ->where( [ 'rev_id' => $revids ] )
                                ->join( 'revision', null, [ 'rev_page = page_id' ] )
                                ->caller( __METHOD__ )
                                ->fetchResultSet();
                        foreach ( $res as $row ) {
                                $revid = (int)$row->rev_id;
                                $pageid = (int)$row->rev_page;
                                $this->mGoodRevIDs[$revid] = $pageid;
                                $this->mLiveRevIDs[$revid] = $pageid;
                                $pageids[$pageid] = '';
                                unset( $remaining[$revid] );
                                unset( $goodRemaining[$revid] );
                        }
                }

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

                // 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 ( $goodRemaining &&
                        $this->getAuthority()->isAllowed( 'deletedhistory' ) ) {

                        $res = $db->newSelectQueryBuilder()
                                ->select( [ 'ar_rev_id', 'ar_namespace', 'ar_title' ] )
                                ->from( 'archive' )
                                ->where( [ 'ar_rev_id' => array_keys( $goodRemaining ) ] )
                                ->caller( __METHOD__ )
                                ->fetchResultSet();

                        $titles = [];
                        foreach ( $res as $row ) {
                                $revid = (int)$row->ar_rev_id;
                                $titles[$revid] = $this->titleFactory->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 = $this->titleFactory->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();

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

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

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

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

                                // 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 loadRedirectTargets() {
                $titlesToResolve = [];
                $db = $this->getDB();

                if ( $this->mPendingRedirectIDs ) {
                        $res = $db->newSelectQueryBuilder()
                                ->select( [
                                        'rd_from',
                                        'rd_namespace',
                                        'rd_fragment',
                                        'rd_interwiki',
                                        'rd_title'
                                ] )
                                ->from( 'redirect' )
                                ->where( [ 'rd_from' => array_keys( $this->mPendingRedirectIDs ) ] )
                                ->caller( __METHOD__ )
                                ->fetchResultSet();

                        foreach ( $res as $row ) {
                                $rdfrom = (int)$row->rd_from;
                                $from = $this->mPendingRedirectIDs[$rdfrom]->getPrefixedText();
                                $to = $this->titleFactory->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( $this->mAllPages[$to->getNamespace()][$to->getDBkey()] )
                                        && !( $this->mConvertTitles && isset( $this->mConvertedTitles[$to->getPrefixedText()] ) )
                                ) {
                                        $titlesToResolve[] = $to;
                                }
                                $this->mRedirectTitles[$from] = $to;
                        }
                }

                if ( $this->mPendingRedirectSpecialPages ) {
                        foreach ( $this->mPendingRedirectSpecialPages as [ $from, $to ] ) {
                                /** @var Title $from */
                                $fromKey = $from->getPrefixedText();
                                $this->mResolvedRedirectTitles[$fromKey] = $from;
                                $this->mRedirectTitles[$fromKey] = $to;
                                if ( $to->isExternal() ) {
                                        $this->mInterwikiTitles[$to->getPrefixedText()] = $to->getInterwiki();
                                } elseif ( !isset( $this->mAllPages[$to->getNamespace()][$to->getDBkey()] ) ) {
                                        $titlesToResolve[] = $to;
                                }
                        }
                        $this->mPendingRedirectSpecialPages = [];

                        // Set private caching since we don't know what criteria the
                        // special pages used to decide on these redirects.
                        $this->mCacheMode = 'private';
                }

                return $this->processTitlesArray( $titlesToResolve );
        }

        /**
         * 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 string[]|LinkTarget[]|PageReference[] $titles
         * @return LinkBatch
         */
        private function processTitlesArray( $titles ) {
                $linkBatch = $this->linkBatchFactory->newLinkBatch();

                /** @var Title[] $titleObjects */
                $titleObjects = [];
                foreach ( $titles as $index => $title ) {
                        if ( is_string( $title ) ) {
                                try {
                                        /** @var Title $titleObj */
                                        $titleObj = $this->titleFactory->newFromTextThrow( $title, $this->mDefaultNamespace );
                                } catch ( MalformedTitleException $ex ) {
                                        // Handle invalid titles gracefully
                                        if ( !isset( $this->mAllPages[0][$title] ) ) {
                                                $this->mAllPages[0][$title] = $this->mFakePageId;
                                                $this->mInvalidTitles[$this->mFakePageId] = [
                                                        'title' => $title,
                                                        'invalidreason' => $this->getErrorFormatter()->formatException( $ex, [ 'bc' => true ] ),
                                                ];
                                                $this->mFakePageId--;
                                        }
                                        continue; // There's nothing else we can do
                                }
                        } elseif ( $title instanceof LinkTarget ) {
                                $titleObj = $this->titleFactory->newFromLinkTarget( $title );
                        } else {
                                $titleObj = $this->titleFactory->newFromPageReference( $title );
                        }

                        $titleObjects[$index] = $titleObj;
                }

                // Get gender information
                $this->genderCache->doTitlesArray( $titleObjects, __METHOD__ );

                foreach ( $titleObjects as $index => $titleObj ) {
                        $title = is_string( $titles[$index] ) ? $titles[$index] : false;
                        $unconvertedTitle = $titleObj->getPrefixedText();
                        $titleWasConverted = false;
                        if ( $titleObj->isExternal() ) {
                                // This title is an interwiki link.
                                $this->mInterwikiTitles[$unconvertedTitle] = $titleObj->getInterwiki();
                        } else {
                                // Variants checking
                                if (
                                        $this->mConvertTitles
                                        && $this->languageConverter->hasVariants()
                                        && !$titleObj->exists()
                                ) {
                                        // ILanguageConverter::findVariantLink will modify titleText and
                                        // titleObj into the canonical variant if possible
                                        $titleText = $title !== false ? $title : $titleObj->getPrefixedText();
                                        $this->languageConverter->findVariantLink( $titleText, $titleObj );
                                        $titleWasConverted = $unconvertedTitle !== $titleObj->getPrefixedText();
                                }

                                if ( $titleObj->getNamespace() < 0 ) {
                                        // Handle Special and Media pages
                                        $titleObj = $titleObj->fixSpecialName();
                                        $ns = $titleObj->getNamespace();
                                        $dbkey = $titleObj->getDBkey();
                                        if ( !isset( $this->mAllSpecials[$ns][$dbkey] ) ) {
                                                $this->mAllSpecials[$ns][$dbkey] = $this->mFakePageId;
                                                $target = null;
                                                if ( $ns === NS_SPECIAL && $this->mResolveRedirects ) {
                                                        $special = $this->specialPageFactory->getPage( $dbkey );
                                                        if ( $special instanceof RedirectSpecialArticle ) {
                                                                // Only RedirectSpecialArticle is intended to redirect to an article, other kinds of
                                                                // RedirectSpecialPage are probably applying weird URL parameters we don't want to
                                                                // handle.
                                                                $context = new DerivativeContext( $this );
                                                                $context->setTitle( $titleObj );
                                                                $context->setRequest( new FauxRequest );
                                                                $special->setContext( $context );
                                                                [ /* $alias */, $subpage ] = $this->specialPageFactory->resolveAlias( $dbkey );
                                                                $target = $special->getRedirect( $subpage );
                                                        }
                                                }
                                                if ( $target ) {
                                                        $this->mPendingRedirectSpecialPages[$dbkey] = [ $titleObj, $target ];
                                                } else {
                                                        $this->mSpecialTitles[$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 ( $title !== false && $title !== $unconvertedTitle ) {
                                        $this->mNormalizedTitles[$title] = $unconvertedTitle;
                                }
                        } elseif ( $title !== false && $title !== $titleObj->getPrefixedText() ) {
                                $this->mNormalizedTitles[$title] = $titleObj->getPrefixedText();
                        }
                }

                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 PageReference|LinkTarget $title
         * @param array $data
         */
        public function setGeneratorData( $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;
        }

        /**
         * Resolve the title a redirect points to.
         *
         * Will follow sequential redirects to find the final page. In
         * the case of a redirect cycle the original page will be returned.
         * self::resolvePendingRedirects must be executed before calling
         * this method.
         *
         * @param Title $titleFrom A title from $this->mResolvedRedirectTitles
         * @return Title
         */
        private function resolveRedirectTitleDest( Title $titleFrom ): Title {
                $seen = [];
                $dest = $titleFrom;
                while ( isset( $this->mRedirectTitles[$dest->getPrefixedText()] ) ) {
                        $dest = $this->mRedirectTitles[$dest->getPrefixedText()];
                        if ( isset( $seen[$dest->getPrefixedText()] ) ) {
                                return $titleFrom;
                        }
                        $seen[$dest->getPrefixedText()] = true;
                }
                return $dest;
        }

        /**
         * 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 === NS_SPECIAL ) {
                                $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 = $this->resolveRedirectTitleDest( $titleFrom );
                                $fromNs = $titleFrom->getNamespace();
                                $fromDBkey = $titleFrom->getDBkey();
                                $toPageId = $dest->getArticleID();
                                if ( isset( $data[$toPageId] ) &&
                                        isset( $this->mGeneratorData[$fromNs][$fromDBkey] )
                                ) {
                                        // It is necessary 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 ( $result instanceof ApiResult &&
                                                !$result->addValue( $path, $toPageId, $data[$toPageId], ApiResult::OVERRIDE )
                                        ) {
                                                return false;
                                        }
                                }
                        }
                }

                return true;
        }

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

        public function getAllowedParams( $flags = 0 ) {
                $result = [
                        'titles' => [
                                ParamValidator::PARAM_ISMULTI => true,
                                ApiBase::PARAM_HELP_MSG => 'api-pageset-param-titles',
                        ],
                        'pageids' => [
                                ParamValidator::PARAM_TYPE => 'integer',
                                ParamValidator::PARAM_ISMULTI => true,
                                ApiBase::PARAM_HELP_MSG => 'api-pageset-param-pageids',
                        ],
                        'revids' => [
                                ParamValidator::PARAM_TYPE => 'integer',
                                ParamValidator::PARAM_ISMULTI => true,
                                ApiBase::PARAM_HELP_MSG => 'api-pageset-param-revids',
                        ],
                        'generator' => [
                                ParamValidator::PARAM_TYPE => null,
                                ApiBase::PARAM_HELP_MSG => 'api-pageset-param-generator',
                                SubmoduleDef::PARAM_SUBMODULE_PARAM_PREFIX => 'g',
                        ],
                        'redirects' => [
                                ParamValidator::PARAM_DEFAULT => false,
                                ApiBase::PARAM_HELP_MSG => $this->mAllowGenerator
                                        ? 'api-pageset-param-redirects-generator'
                                        : 'api-pageset-param-redirects-nogenerator',
                        ],
                        'converttitles' => [
                                ParamValidator::PARAM_DEFAULT => false,
                                ApiBase::PARAM_HELP_MSG => [
                                        'api-pageset-param-converttitles',
                                        Message::listParam( LanguageConverter::$languagesWithVariants, 'text' ),
                                ],
                        ],
                ];

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

                return $result;
        }

        public 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 = ParamValidator::explodeMultiValue( $value, self::LIMIT_SML2 + 1 );
                        $l = count( $value );
                        $rawValue = ParamValidator::explodeMultiValue( $rawValue, $l );
                        for ( $i = 0; $i < $l; $i++ ) {
                                if ( $value[$i] !== $rawValue[$i] ) {
                                        $this->mNormalizedTitles[$rawValue[$i]] = $value[$i];
                                }
                        }
                }
        }

        /**
         * Get an array of all available generators
         * @return array<string,string>
         */
        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::class ) ) {
                                        $gens[$name] = $prefix . $name;
                                }
                        }
                        ksort( $gens );
                        self::$generators = $gens;
                }

                return self::$generators;
        }
}

/** @deprecated class alias since 1.43 */
class_alias( ApiPageSet::class, 'ApiPageSet' );