Title::convertByteClassToUnicodeClass(): Cleanup

[mediawiki.git] / includes / Title.php

<?php
/**
 * Representation of a title within MediaWiki.
 *
 * See Title.md
 *
 * 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
 */

use MediaWiki\Interwiki\InterwikiLookup;
use MediaWiki\Linker\LinkTarget;
use MediaWiki\MediaWikiServices;
use MediaWiki\User\UserIdentity;
use Wikimedia\Assert\Assert;
use Wikimedia\Rdbms\Database;
use Wikimedia\Rdbms\IDatabase;

/**
 * Represents a title within MediaWiki.
 * Optionally may contain an interwiki designation or namespace.
 * @note This class can fetch various kinds of data from the database;
 *       however, it does so inefficiently.
 * @note Consider using a TitleValue object instead. TitleValue is more lightweight
 *       and does not rely on global state or the database.
 */
class Title implements LinkTarget, IDBAccessObject {
        /** @var MapCacheLRU|null */
        private static $titleCache = null;

        /**
         * Title::newFromText maintains a cache to avoid expensive re-normalization of
         * commonly used titles. On a batch operation this can become a memory leak
         * if not bounded. After hitting this many titles reset the cache.
         */
        private const CACHE_MAX = 1000;

        /**
         * Used to be GAID_FOR_UPDATE define(). Used with getArticleID() and friends
         * to use the master DB and inject it into link cache.
         * @deprecated since 1.34, use Title::READ_LATEST instead.
         */
        public const GAID_FOR_UPDATE = 512;

        /**
         * Flag for use with factory methods like newFromLinkTarget() that have
         * a $forceClone parameter. If set, the method must return a new instance.
         * Without this flag, some factory methods may return existing instances.
         *
         * @since 1.33
         */
        public const NEW_CLONE = 'clone';

        /***************************************************************************/
        // region   Private member variables
        /** @name   Private member variables
         * Please use the accessor functions instead.
         * @internal
         * @{
         */

        /** @var string Text form (spaces not underscores) of the main part */
        public $mTextform = '';
        /** @var string URL-encoded form of the main part */
        public $mUrlform = '';
        /** @var string Main part with underscores */
        public $mDbkeyform = '';
        /** @var int Namespace index, i.e. one of the NS_xxxx constants */
        public $mNamespace = NS_MAIN;
        /** @var string Interwiki prefix */
        public $mInterwiki = '';
        /** @var bool Was this Title created from a string with a local interwiki prefix? */
        private $mLocalInterwiki = false;
        /** @var string Title fragment (i.e. the bit after the #) */
        public $mFragment = '';

        /** @var int Article ID, fetched from the link cache on demand */
        public $mArticleID = -1;

        /** @var bool|int ID of most recent revision */
        protected $mLatestID = false;

        /**
         * @var bool|string ID of the page's content model, i.e. one of the
         *   CONTENT_MODEL_XXX constants
         */
        private $mContentModel = false;

        /**
         * @var bool If a content model was forced via setContentModel()
         *   this will be true to avoid having other code paths reset it
         */
        private $mForcedContentModel = false;

        /** @var int Estimated number of revisions; null of not loaded */
        private $mEstimateRevisions;

        /** @var array Array of groups allowed to edit this article */
        public $mRestrictions = [];

        /**
         * @var string|bool Comma-separated set of permission keys
         * indicating who can move or edit the page from the page table, (pre 1.10) rows.
         * Edit and move sections are separated by a colon
         * Example: "edit=autoconfirmed,sysop:move=sysop"
         */
        protected $mOldRestrictions = false;

        /** @var bool Cascade restrictions on this page to included templates and images? */
        public $mCascadeRestriction;

        /** Caching the results of getCascadeProtectionSources */
        public $mCascadingRestrictions;

        /** @var array When do the restrictions on this page expire? */
        protected $mRestrictionsExpiry = [];

        /** @var bool Are cascading restrictions in effect on this page? */
        protected $mHasCascadingRestrictions;

        /** @var array Where are the cascading restrictions coming from on this page? */
        public $mCascadeSources;

        /** @var bool Boolean for initialisation on demand */
        public $mRestrictionsLoaded = false;

        /**
         * Text form including namespace/interwiki, initialised on demand
         *
         * Only public to share cache with TitleFormatter
         *
         * @internal
         * @var string|null
         */
        public $prefixedText = null;

        /** @var mixed Cached value for getTitleProtection (create protection) */
        public $mTitleProtection;

        /**
         * @var int Namespace index when there is no namespace. Don't change the
         *   following default, NS_MAIN is hardcoded in several places. See T2696.
         *   Used primarily for {{transclusion}} tags.
         * @see newFromText()
         */
        public $mDefaultNamespace = NS_MAIN;

        /** @var int The page length, 0 for special pages */
        protected $mLength = -1;

        /** @var null|bool Is the article at this title a redirect? */
        public $mRedirect = null;

        /** @var bool Whether a page has any subpages */
        private $mHasSubpages;

        /** @var array|null The (string) language code of the page's language and content code. */
        private $mPageLanguage;

        /** @var string|bool|null The page language code from the database, null if not saved in
         * the database or false if not loaded, yet.
         */
        private $mDbPageLanguage = false;

        /** @var TitleValue|null A corresponding TitleValue object */
        private $mTitleValue = null;

        /** @var bool|null Would deleting this page be a big deletion? */
        private $mIsBigDeletion = null;

        /** @var bool|null Is the title known to be valid? */
        private $mIsValid = null;

        // endregion -- end of private member variables
        /** @} */
        /***************************************************************************/

        /**
         * Shorthand for getting a Language Converter for specific language
         * @param Language $language Language of converter
         * @return ILanguageConverter
         */
        private function getLanguageConverter( $language ) : ILanguageConverter {
                return MediaWikiServices::getInstance()->getLanguageConverterFactory()
                        ->getLanguageConverter( $language );
        }

        /**
         * Shorthand for getting a Language Converter for page's language
         * @return ILanguageConverter
         */
        private function getPageLanguageConverter() : ILanguageConverter {
                return $this->getLanguageConverter( $this->getPageLanguage() );
        }

        /**
         * B/C kludge: provide a TitleParser for use by Title.
         * Ideally, Title would have no methods that need this.
         * Avoid usage of this singleton by using TitleValue
         * and the associated services when possible.
         *
         * @return TitleFormatter
         */
        private static function getTitleFormatter() {
                return MediaWikiServices::getInstance()->getTitleFormatter();
        }

        /**
         * B/C kludge: provide an InterwikiLookup for use by Title.
         * Ideally, Title would have no methods that need this.
         * Avoid usage of this singleton by using TitleValue
         * and the associated services when possible.
         *
         * @return InterwikiLookup
         */
        private static function getInterwikiLookup() {
                return MediaWikiServices::getInstance()->getInterwikiLookup();
        }

        private function __construct() {
        }

        /**
         * Create a new Title from a prefixed DB key
         *
         * @param string $key The database key, which has underscores
         *      instead of spaces, possibly including namespace and
         *      interwiki prefixes
         * @return Title|null Title, or null on an error
         */
        public static function newFromDBkey( $key ) {
                $t = new self();

                try {
                        $t->secureAndSplit( $key );
                        return $t;
                } catch ( MalformedTitleException $ex ) {
                        return null;
                }
        }

        /**
         * Returns a Title given a TitleValue.
         * If the given TitleValue is already a Title instance, that instance is returned,
         * unless $forceClone is "clone". If $forceClone is "clone" and the given TitleValue
         * is already a Title instance, that instance is copied using the clone operator.
         *
         * @deprecated since 1.34, use newFromLinkTarget or castFromLinkTarget
         *
         * @param TitleValue $titleValue Assumed to be safe.
         * @param string $forceClone set to NEW_CLONE to ensure a fresh instance is returned.
         *
         * @return Title
         */
        public static function newFromTitleValue( TitleValue $titleValue, $forceClone = '' ) {
                return self::newFromLinkTarget( $titleValue, $forceClone );
        }

        /**
         * Returns a Title given a LinkTarget.
         * If the given LinkTarget is already a Title instance, that instance is returned,
         * unless $forceClone is "clone". If $forceClone is "clone" and the given LinkTarget
         * is already a Title instance, that instance is copied using the clone operator.
         *
         * @param LinkTarget $linkTarget Assumed to be safe.
         * @param string $forceClone set to NEW_CLONE to ensure a fresh instance is returned.
         *
         * @return Title
         */
        public static function newFromLinkTarget( LinkTarget $linkTarget, $forceClone = '' ) {
                if ( $linkTarget instanceof Title ) {
                        // Special case if it's already a Title object
                        if ( $forceClone === self::NEW_CLONE ) {
                                return clone $linkTarget;
                        } else {
                                return $linkTarget;
                        }
                }
                return self::makeTitle(
                        $linkTarget->getNamespace(),
                        $linkTarget->getText(),
                        $linkTarget->getFragment(),
                        $linkTarget->getInterwiki()
                );
        }

        /**
         * Same as newFromLinkTarget, but if passed null, returns null.
         *
         * @param LinkTarget|null $linkTarget Assumed to be safe (if not null).
         *
         * @return Title|null
         */
        public static function castFromLinkTarget( $linkTarget ) {
                return $linkTarget ? self::newFromLinkTarget( $linkTarget ) : null;
        }

        /**
         * Create a new Title from text, such as what one would find in a link.
         * Decodes any HTML entities in the text.
         * Titles returned by this method are guaranteed to be valid.
         * Call canExist() to check if the Title represents an editable page.
         *
         * @note The Title instance returned by this method is not guaranteed to be a fresh instance.
         * It may instead be a cached instance created previously, with references to it remaining
         * elsewhere.
         *
         * @param string|int|null $text The link text; spaces, prefixes, and an
         *   initial ':' indicating the main namespace are accepted.
         * @param int $defaultNamespace The namespace to use if none is specified
         *   by a prefix.  If you want to force a specific namespace even if
         *   $text might begin with a namespace prefix, use makeTitle() or
         *   makeTitleSafe().
         * @throws InvalidArgumentException
         * @return Title|null Title or null if the Title could not be parsed because
         *         it is invalid.
         */
        public static function newFromText( $text, $defaultNamespace = NS_MAIN ) {
                // DWIM: Integers can be passed in here when page titles are used as array keys.
                if ( $text !== null && !is_string( $text ) && !is_int( $text ) ) {
                        throw new InvalidArgumentException( '$text must be a string.' );
                }
                if ( $text === null ) {
                        return null;
                }

                try {
                        return self::newFromTextThrow( (string)$text, (int)$defaultNamespace );
                } catch ( MalformedTitleException $ex ) {
                        return null;
                }
        }

        /**
         * Like Title::newFromText(), but throws MalformedTitleException when the title is invalid,
         * rather than returning null.
         *
         * Titles returned by this method are guaranteed to be valid.
         * Call canExist() to check if the Title represents an editable page.
         *
         * @note The Title instance returned by this method is not guaranteed to be a fresh instance.
         * It may instead be a cached instance created previously, with references to it remaining
         * elsewhere.
         *
         * @see Title::newFromText
         *
         * @since 1.25
         * @param string $text Title text to check
         * @param int $defaultNamespace
         * @throws MalformedTitleException If the title is invalid.
         * @return Title
         */
        public static function newFromTextThrow( $text, $defaultNamespace = NS_MAIN ) {
                if ( is_object( $text ) ) {
                        throw new MWException( '$text must be a string, given an object' );
                } elseif ( $text === null ) {
                        // Legacy code relies on MalformedTitleException being thrown in this case
                        // (happens when URL with no title in it is parsed). TODO fix
                        throw new MalformedTitleException( 'title-invalid-empty' );
                }

                $titleCache = self::getTitleCache();

                // Wiki pages often contain multiple links to the same page.
                // Title normalization and parsing can become expensive on pages with many
                // links, so we can save a little time by caching them.
                // In theory these are value objects and won't get changed...
                if ( $defaultNamespace === NS_MAIN ) {
                        $t = $titleCache->get( $text );
                        if ( $t ) {
                                return $t;
                        }
                }

                // Convert things like &eacute; &#257; or &#x3017; into normalized (T16952) text
                $filteredText = Sanitizer::decodeCharReferencesAndNormalize( $text );

                $t = new Title();
                $dbKeyForm = strtr( $filteredText, ' ', '_' );

                $t->secureAndSplit( $dbKeyForm, (int)$defaultNamespace );
                if ( $defaultNamespace === NS_MAIN ) {
                        $titleCache->set( $text, $t );
                }
                return $t;
        }

        /**
         * THIS IS NOT THE FUNCTION YOU WANT. Use Title::newFromText().
         *
         * Example of wrong and broken code:
         * $title = Title::newFromURL( $wgRequest->getVal( 'title' ) );
         *
         * Example of right code:
         * $title = Title::newFromText( $wgRequest->getVal( 'title' ) );
         *
         * Create a new Title from URL-encoded text. Ensures that
         * the given title's length does not exceed the maximum.
         *
         * @param string $url The title, as might be taken from a URL
         * @return Title|null The new object, or null on an error
         */
        public static function newFromURL( $url ) {
                $t = new Title();

                # For compatibility with old buggy URLs. "+" is usually not valid in titles,
                # but some URLs used it as a space replacement and they still come
                # from some external search tools.
                if ( strpos( self::legalChars(), '+' ) === false ) {
                        $url = strtr( $url, '+', ' ' );
                }

                $dbKeyForm = strtr( $url, ' ', '_' );

                try {
                        $t->secureAndSplit( $dbKeyForm );
                        return $t;
                } catch ( MalformedTitleException $ex ) {
                        return null;
                }
        }

        /**
         * @return MapCacheLRU
         */
        private static function getTitleCache() {
                if ( self::$titleCache === null ) {
                        self::$titleCache = new MapCacheLRU( self::CACHE_MAX );
                }
                return self::$titleCache;
        }

        /**
         * Returns a list of fields that are to be selected for initializing Title
         * objects or LinkCache entries.
         *
         * @return array
         */
        protected static function getSelectFields() {
                global $wgPageLanguageUseDB;

                $fields = [
                        'page_namespace', 'page_title', 'page_id',
                        'page_len', 'page_is_redirect', 'page_latest',
                        'page_content_model',
                ];

                if ( $wgPageLanguageUseDB ) {
                        $fields[] = 'page_lang';
                }

                return $fields;
        }

        /**
         * Create a new Title from an article ID
         *
         * @param int $id The page_id corresponding to the Title to create
         * @param int $flags Bitfield of class READ_* constants
         * @return Title|null The new object, or null on an error
         */
        public static function newFromID( $id, $flags = 0 ) {
                $flags |= ( $flags & self::GAID_FOR_UPDATE ) ? self::READ_LATEST : 0; // b/c
                list( $index, $options ) = DBAccessObjectUtils::getDBOptions( $flags );
                $row = wfGetDB( $index )->selectRow(
                        'page',
                        self::getSelectFields(),
                        [ 'page_id' => $id ],
                        __METHOD__,
                        $options
                );
                if ( $row !== false ) {
                        $title = self::newFromRow( $row );
                } else {
                        $title = null;
                }

                return $title;
        }

        /**
         * Make an array of titles from an array of IDs
         *
         * @param int[] $ids Array of IDs
         * @return Title[] Array of Titles
         */
        public static function newFromIDs( $ids ) {
                if ( !count( $ids ) ) {
                        return [];
                }
                $dbr = wfGetDB( DB_REPLICA );

                $res = $dbr->select(
                        'page',
                        self::getSelectFields(),
                        [ 'page_id' => $ids ],
                        __METHOD__
                );

                $titles = [];
                foreach ( $res as $row ) {
                        $titles[] = self::newFromRow( $row );
                }
                return $titles;
        }

        /**
         * Make a Title object from a DB row
         *
         * @param stdClass $row Object database row (needs at least page_title,page_namespace)
         * @return Title Corresponding Title
         */
        public static function newFromRow( $row ) {
                $t = self::makeTitle( $row->page_namespace, $row->page_title );
                $t->loadFromRow( $row );
                return $t;
        }

        /**
         * Load Title object fields from a DB row.
         * If false is given, the title will be treated as non-existing.
         *
         * @param stdClass|bool $row Database row
         */
        public function loadFromRow( $row ) {
                if ( $row ) { // page found
                        if ( isset( $row->page_id ) ) {
                                $this->mArticleID = (int)$row->page_id;
                        }
                        if ( isset( $row->page_len ) ) {
                                $this->mLength = (int)$row->page_len;
                        }
                        if ( isset( $row->page_is_redirect ) ) {
                                $this->mRedirect = (bool)$row->page_is_redirect;
                        }
                        if ( isset( $row->page_latest ) ) {
                                $this->mLatestID = (int)$row->page_latest;
                        }
                        if ( isset( $row->page_content_model ) ) {
                                $this->lazyFillContentModel( $row->page_content_model );
                        } else {
                                $this->lazyFillContentModel( false ); // lazily-load getContentModel()
                        }
                        if ( isset( $row->page_lang ) ) {
                                $this->mDbPageLanguage = (string)$row->page_lang;
                        }
                        if ( isset( $row->page_restrictions ) ) {
                                $this->mOldRestrictions = $row->page_restrictions;
                        }
                } else { // page not found
                        $this->mArticleID = 0;
                        $this->mLength = 0;
                        $this->mRedirect = false;
                        $this->mLatestID = 0;
                        $this->lazyFillContentModel( false ); // lazily-load getContentModel()
                }
        }

        /**
         * Create a new Title from a namespace index and a DB key.
         *
         * It's assumed that $ns and $title are safe, for instance when
         * they came directly from the database or a special page name,
         * not from user input.
         *
         * No validation is applied. For convenience, spaces are normalized
         * to underscores, so that e.g. user_text fields can be used directly.
         *
         * @note This method may return Title objects that are "invalid"
         * according to the isValid() method. This is usually caused by
         * configuration changes: e.g. a namespace that was once defined is
         * no longer configured, or a character that was once allowed in
         * titles is now forbidden.
         *
         * @param int $ns The namespace of the article
         * @param string $title The unprefixed database key form
         * @param string $fragment The link fragment (after the "#")
         * @param string $interwiki The interwiki prefix
         * @return Title The new object
         */
        public static function makeTitle( $ns, $title, $fragment = '', $interwiki = '' ) {
                $t = new Title();
                $t->mInterwiki = $interwiki;
                $t->mFragment = $fragment;
                $t->mNamespace = $ns = (int)$ns;
                $t->mDbkeyform = strtr( $title, ' ', '_' );
                $t->mArticleID = ( $ns >= 0 ) ? -1 : 0;
                $t->mUrlform = wfUrlencode( $t->mDbkeyform );
                $t->mTextform = strtr( $title, '_', ' ' );
                return $t;
        }

        /**
         * Create a new Title from a namespace index and a DB key.
         * The parameters will be checked for validity, which is a bit slower
         * than makeTitle() but safer for user-provided data.
         *
         * The Title object returned by this method is guaranteed to be valid.
         * Call canExist() to check if the Title represents an editable page.
         *
         * @param int $ns The namespace of the article
         * @param string $title Database key form
         * @param string $fragment The link fragment (after the "#")
         * @param string $interwiki Interwiki prefix
         * @return Title|null The new object, or null on an error
         */
        public static function makeTitleSafe( $ns, $title, $fragment = '', $interwiki = '' ) {
                // NOTE: ideally, this would just call makeTitle() and then isValid(),
                // but presently, that means more overhead on a potential performance hotspot.

                if ( !MediaWikiServices::getInstance()->getNamespaceInfo()->exists( $ns ) ) {
                        return null;
                }

                $t = new Title();
                $dbKeyForm = self::makeName( $ns, $title, $fragment, $interwiki, true );

                try {
                        $t->secureAndSplit( $dbKeyForm );
                        return $t;
                } catch ( MalformedTitleException $ex ) {
                        return null;
                }
        }

        /**
         * Create a new Title for the Main Page
         *
         * This uses the 'mainpage' interface message, which could be specified in
         * `$wgForceUIMsgAsContentMsg`. If that is the case, then calling this method
         * will use the user language, which would involve initialising the session
         * via `RequestContext::getMain()->getLanguage()`. For session-less endpoints,
         * be sure to pass in a MessageLocalizer (such as your own RequestContext,
         * or ResourceloaderContext) to prevent an error.
         *
         * @note The Title instance returned by this method is not guaranteed to be a fresh instance.
         * It may instead be a cached instance created previously, with references to it remaining
         * elsewhere.
         *
         * @param MessageLocalizer|null $localizer An optional context to use (since 1.34)
         * @return Title
         */
        public static function newMainPage( MessageLocalizer $localizer = null ) {
                if ( $localizer ) {
                        $msg = $localizer->msg( 'mainpage' );
                } else {
                        $msg = wfMessage( 'mainpage' );
                }

                $title = self::newFromText( $msg->inContentLanguage()->text() );

                // Every page renders at least one link to the Main Page (e.g. sidebar).
                // If the localised value is invalid, don't produce fatal errors that
                // would make the wiki inaccessible (and hard to fix the invalid message).
                // Gracefully fallback...
                if ( !$title ) {
                        $title = self::newFromText( 'Main Page' );
                }
                return $title;
        }

        /**
         * Get the prefixed DB key associated with an ID
         *
         * @param int $id The page_id of the article
         * @return string|null An object representing the article, or null if no such article was found
         * @deprecated since 1.36, use Title::newFromID( $id )->getPrefixedDBkey() instead.
         */
        public static function nameOf( $id ) {
                wfDeprecated( __METHOD__, '1.36' );

                $dbr = wfGetDB( DB_REPLICA );

                $s = $dbr->selectRow(
                        'page',
                        [ 'page_namespace', 'page_title' ],
                        [ 'page_id' => $id ],
                        __METHOD__
                );
                if ( $s === false ) {
                        return null;
                }

                return self::makeName( $s->page_namespace, $s->page_title );
        }

        /**
         * Get a regex character class describing the legal characters in a link
         *
         * @return string The list of characters, not delimited
         */
        public static function legalChars() {
                global $wgLegalTitleChars;
                return $wgLegalTitleChars;
        }

        /**
         * Utility method for converting a character sequence from bytes to Unicode.
         *
         * Primary usecase being converting $wgLegalTitleChars to a sequence usable in
         * javascript, as PHP uses UTF-8 bytes where javascript uses Unicode code units.
         *
         * @param string $byteClass
         * @return string
         */
        public static function convertByteClassToUnicodeClass( $byteClass ) {
                $length = strlen( $byteClass );
                // Input token queue
                $x0 = $x1 = $x2 = '';
                // Decoded queue
                $d0 = $d1 = '';
                // Decoded integer codepoints
                $ord0 = $ord1 = $ord2 = 0;
                // Re-encoded queue
                $r0 = $r1 = $r2 = '';
                // Output
                $out = '';
                // Flags
                $allowUnicode = false;
                for ( $pos = 0; $pos < $length; $pos++ ) {
                        // Shift the queues down
                        $x2 = $x1;
                        $x1 = $x0;
                        $d1 = $d0;
                        $ord2 = $ord1;
                        $ord1 = $ord0;
                        $r2 = $r1;
                        $r1 = $r0;
                        // Load the current input token and decoded values
                        $inChar = $byteClass[$pos];
                        if ( $inChar === '\\' ) {
                                if ( preg_match( '/x([0-9a-fA-F]{2})/A', $byteClass, $m, 0, $pos + 1 ) ) {
                                        $x0 = $inChar . $m[0];
                                        $d0 = chr( hexdec( $m[1] ) );
                                        $pos += strlen( $m[0] );
                                } elseif ( preg_match( '/[0-7]{3}/A', $byteClass, $m, 0, $pos + 1 ) ) {
                                        $x0 = $inChar . $m[0];
                                        $d0 = chr( octdec( $m[0] ) );
                                        $pos += strlen( $m[0] );
                                } elseif ( $pos + 1 >= $length ) {
                                        $x0 = $d0 = '\\';
                                } else {
                                        $d0 = $byteClass[$pos + 1];
                                        $x0 = $inChar . $d0;
                                        $pos++;
                                }
                        } else {
                                $x0 = $d0 = $inChar;
                        }
                        $ord0 = ord( $d0 );
                        // Load the current re-encoded value
                        if ( $ord0 < 32 || $ord0 == 0x7f ) {
                                $r0 = sprintf( '\x%02x', $ord0 );
                        } elseif ( $ord0 >= 0x80 ) {
                                // Allow unicode if a single high-bit character appears
                                $r0 = sprintf( '\x%02x', $ord0 );
                                $allowUnicode = true;
                                // @phan-suppress-next-line PhanParamSuspiciousOrder false positive
                        } elseif ( strpos( '-\\[]^', $d0 ) !== false ) {
                                $r0 = '\\' . $d0;
                        } else {
                                $r0 = $d0;
                        }
                        // Do the output
                        if ( $x0 !== '' && $x1 === '-' && $x2 !== '' ) {
                                // Range
                                if ( $ord2 > $ord0 ) {
                                        // Empty range
                                } elseif ( $ord0 >= 0x80 ) {
                                        // Unicode range
                                        $allowUnicode = true;
                                        if ( $ord2 < 0x80 ) {
                                                // Keep the non-unicode section of the range
                                                $out .= "$r2-\\x7F";
                                        }
                                } else {
                                        // Normal range
                                        $out .= "$r2-$r0";
                                }
                                // Reset state to the initial value
                                $x0 = $x1 = $d0 = $d1 = $r0 = $r1 = '';
                        } elseif ( $ord2 < 0x80 ) {
                                // ASCII character
                                $out .= $r2;
                        }
                }
                // @phan-suppress-next-line PhanSuspiciousValueComparison
                if ( $ord1 < 0x80 ) {
                        $out .= $r1;
                }
                if ( $ord0 < 0x80 ) {
                        $out .= $r0;
                }
                if ( $allowUnicode ) {
                        $out .= '\u0080-\uFFFF';
                }
                return $out;
        }

        /**
         * Make a prefixed DB key from a DB key and a namespace index
         *
         * @param int $ns Numerical representation of the namespace
         * @param string $title The DB key form the title
         * @param string $fragment The link fragment (after the "#")
         * @param string $interwiki The interwiki prefix
         * @param bool $canonicalNamespace If true, use the canonical name for
         *   $ns instead of the localized version.
         * @return string The prefixed form of the title
         */
        public static function makeName( $ns, $title, $fragment = '', $interwiki = '',
                $canonicalNamespace = false
        ) {
                if ( $canonicalNamespace ) {
                        $namespace = MediaWikiServices::getInstance()->getNamespaceInfo()->
                                getCanonicalName( $ns );
                } else {
                        $namespace = MediaWikiServices::getInstance()->getContentLanguage()->getNsText( $ns );
                }
                $name = $namespace == '' ? $title : "$namespace:$title";
                if ( strval( $interwiki ) != '' ) {
                        $name = "$interwiki:$name";
                }
                if ( strval( $fragment ) != '' ) {
                        $name .= '#' . $fragment;
                }
                return $name;
        }

        /**
         * Callback for usort() to do title sorts by (namespace, title)
         *
         * @param LinkTarget $a
         * @param LinkTarget $b
         *
         * @return int Result of string comparison, or namespace comparison
         */
        public static function compare( LinkTarget $a, LinkTarget $b ) {
                return $a->getNamespace() <=> $b->getNamespace()
                        ?: strcmp( $a->getText(), $b->getText() );
        }

        /**
         * Returns true if the title is a valid link target, and that it has been
         * properly normalized. This method checks that the title is syntactically valid,
         * and that the namespace it refers to exists.
         *
         * Titles constructed using newFromText() or makeTitleSafe() are always valid.
         *
         * @note Code that wants to check whether the title can represent a page that can
         * be created and edited should use canExist() instead. Examples of valid titles
         * that cannot "exist" are Special pages, interwiki links, and on-page section links
         * that only have the fragment part set.
         *
         * @see canExist()
         *
         * @return bool
         */
        public function isValid() {
                if ( $this->mIsValid !== null ) {
                        return $this->mIsValid;
                }

                try {
                        $text = $this->getFullText();
                        $titleCodec = MediaWikiServices::getInstance()->getTitleParser();

                        '@phan-var MediaWikiTitleCodec $titleCodec';
                        $parts = $titleCodec->splitTitleString( $text, $this->mNamespace );

                        // Check that nothing changed!
                        // This ensures that $text was already perperly normalized.
                        if ( $parts['fragment'] !== $this->mFragment
                                || $parts['interwiki'] !== $this->mInterwiki
                                || $parts['local_interwiki'] !== $this->mLocalInterwiki
                                || $parts['namespace'] !== $this->mNamespace
                                || $parts['dbkey'] !== $this->mDbkeyform
                        ) {
                                $this->mIsValid = false;
                                return $this->mIsValid;
                        }
                } catch ( MalformedTitleException $ex ) {
                        $this->mIsValid = false;
                        return $this->mIsValid;
                }

                $this->mIsValid = true;
                return $this->mIsValid;
        }

        /**
         * Determine whether the object refers to a page within
         * this project (either this wiki or a wiki with a local
         * interwiki, see https://www.mediawiki.org/wiki/Manual:Interwiki_table#iw_local )
         *
         * @return bool True if this is an in-project interwiki link or a wikilink, false otherwise
         */
        public function isLocal() {
                if ( $this->isExternal() ) {
                        $iw = self::getInterwikiLookup()->fetch( $this->mInterwiki );
                        if ( $iw ) {
                                return $iw->isLocal();
                        }
                }
                return true;
        }

        /**
         * Is this Title interwiki?
         *
         * @return bool
         */
        public function isExternal() {
                return $this->mInterwiki !== '';
        }

        /**
         * Get the interwiki prefix
         *
         * Use Title::isExternal to check if a interwiki is set
         *
         * @return string Interwiki prefix
         */
        public function getInterwiki() {
                return $this->mInterwiki;
        }

        /**
         * Was this a local interwiki link?
         *
         * @return bool
         */
        public function wasLocalInterwiki() {
                return $this->mLocalInterwiki;
        }

        /**
         * Determine whether the object refers to a page within
         * this project and is transcludable.
         *
         * @return bool True if this is transcludable
         */
        public function isTrans() {
                if ( !$this->isExternal() ) {
                        return false;
                }

                return self::getInterwikiLookup()->fetch( $this->mInterwiki )->isTranscludable();
        }

        /**
         * Returns the DB name of the distant wiki which owns the object.
         *
         * @return string|false The DB name
         */
        public function getTransWikiID() {
                if ( !$this->isExternal() ) {
                        return false;
                }

                return self::getInterwikiLookup()->fetch( $this->mInterwiki )->getWikiID();
        }

        /**
         * Get a TitleValue object representing this Title.
         *
         * @note Not all valid Titles have a corresponding valid TitleValue
         * (e.g. TitleValues cannot represent page-local links that have a
         * fragment but no title text).
         *
         * @return TitleValue|null
         */
        public function getTitleValue() {
                if ( $this->mTitleValue === null ) {
                        try {
                                $this->mTitleValue = new TitleValue(
                                        $this->mNamespace,
                                        $this->mDbkeyform,
                                        $this->mFragment,
                                        $this->mInterwiki
                                );
                        } catch ( InvalidArgumentException $ex ) {
                                wfDebug( __METHOD__ . ': Can\'t create a TitleValue for [[' .
                                        $this->getPrefixedText() . ']]: ' . $ex->getMessage() );
                        }
                }

                return $this->mTitleValue;
        }

        /**
         * Get the text form (spaces not underscores) of the main part
         *
         * @return string Main part of the title
         */
        public function getText() {
                return $this->mTextform;
        }

        /**
         * Get the URL-encoded form of the main part
         *
         * @return string Main part of the title, URL-encoded
         */
        public function getPartialURL() {
                return $this->mUrlform;
        }

        /**
         * Get the main part with underscores
         *
         * @return string Main part of the title, with underscores
         */
        public function getDBkey() {
                return $this->mDbkeyform;
        }

        /**
         * Get the namespace index, i.e. one of the NS_xxxx constants.
         *
         * @return int Namespace index
         */
        public function getNamespace() {
                return $this->mNamespace;
        }

        /**
         * Get the page's content model id, see the CONTENT_MODEL_XXX constants.
         *
         * @todo Deprecate this in favor of SlotRecord::getModel()
         *
         * @param int $flags Either a bitfield of class READ_* constants or GAID_FOR_UPDATE
         * @return string Content model id
         */
        public function getContentModel( $flags = 0 ) {
                if ( $this->mForcedContentModel ) {
                        if ( !$this->mContentModel ) {
                                throw new RuntimeException( 'Got out of sync; an empty model is being forced' );
                        }
                        // Content model is locked to the currently loaded one
                        return $this->mContentModel;
                }

                if ( DBAccessObjectUtils::hasFlags( $flags, self::READ_LATEST ) ) {
                        $this->lazyFillContentModel( $this->loadFieldFromDB( 'page_content_model', $flags ) );
                } elseif (
                        ( !$this->mContentModel || $flags & self::GAID_FOR_UPDATE ) &&
                        $this->getArticleID( $flags )
                ) {
                        $linkCache = MediaWikiServices::getInstance()->getLinkCache();
                        $linkCache->addLinkObj( $this ); # in case we already had an article ID
                        $this->lazyFillContentModel( $linkCache->getGoodLinkFieldObj( $this, 'model' ) );
                }

                if ( !$this->mContentModel ) {
                        $this->lazyFillContentModel( ContentHandler::getDefaultModelFor( $this ) );
                }

                return $this->mContentModel;
        }

        /**
         * Convenience method for checking a title's content model name
         *
         * @param string $id The content model ID (use the CONTENT_MODEL_XXX constants).
         * @return bool True if $this->getContentModel() == $id
         */
        public function hasContentModel( $id ) {
                return $this->getContentModel() == $id;
        }

        /**
         * Set a proposed content model for the page for permissions checking
         *
         * This does not actually change the content model of a title in the DB.
         * It only affects this particular Title instance. The content model is
         * forced to remain this value until another setContentModel() call.
         *
         * ContentHandler::canBeUsedOn() should be checked before calling this
         * if there is any doubt regarding the applicability of the content model
         *
         * @since 1.28
         * @param string $model CONTENT_MODEL_XXX constant
         */
        public function setContentModel( $model ) {
                if ( (string)$model === '' ) {
                        throw new InvalidArgumentException( "Missing CONTENT_MODEL_* constant" );
                }

                $this->mContentModel = $model;
                $this->mForcedContentModel = true;
        }

        /**
         * If the content model field is not frozen then update it with a retreived value
         *
         * @param string|bool $model CONTENT_MODEL_XXX constant or false
         */
        private function lazyFillContentModel( $model ) {
                if ( !$this->mForcedContentModel ) {
                        $this->mContentModel = ( $model === false ) ? false : (string)$model;
                }
        }

        /**
         * Get the namespace text
         *
         * @return string|false Namespace text
         */
        public function getNsText() {
                if ( $this->isExternal() ) {
                        // This probably shouldn't even happen, except for interwiki transclusion.
                        // If possible, use the canonical name for the foreign namespace.
                        $nsText = MediaWikiServices::getInstance()->getNamespaceInfo()->
                                getCanonicalName( $this->mNamespace );
                        if ( $nsText !== false ) {
                                return $nsText;
                        }
                }

                try {
                        $formatter = self::getTitleFormatter();
                        return $formatter->getNamespaceName( $this->mNamespace, $this->mDbkeyform );
                } catch ( InvalidArgumentException $ex ) {
                        wfDebug( __METHOD__ . ': ' . $ex->getMessage() );
                        return false;
                }
        }

        /**
         * Get the namespace text of the subject (rather than talk) page
         *
         * @return string Namespace text
         */
        public function getSubjectNsText() {
                $services = MediaWikiServices::getInstance();
                return $services->getContentLanguage()->
                        getNsText( $services->getNamespaceInfo()->getSubject( $this->mNamespace ) );
        }

        /**
         * Get the namespace text of the talk page
         *
         * @return string Namespace text
         */
        public function getTalkNsText() {
                $services = MediaWikiServices::getInstance();
                return $services->getContentLanguage()->
                        getNsText( $services->getNamespaceInfo()->getTalk( $this->mNamespace ) );
        }

        /**
         * Can this title have a corresponding talk page?
         *
         * False for relative section links (with getText() === ''),
         * interwiki links (with getInterwiki() !== ''), and pages in NS_SPECIAL.
         *
         * @see NamespaceInfo::canHaveTalkPage
         * @since 1.30
         *
         * @return bool True if this title either is a talk page or can have a talk page associated.
         */
        public function canHaveTalkPage() {
                return MediaWikiServices::getInstance()->getNamespaceInfo()->canHaveTalkPage( $this );
        }

        /**
         * Can this title represent a page in the wiki's database?
         *
         * Titles can exist as pages in the database if they are valid, and they
         * are not Special pages, interwiki links, or fragment-only links.
         *
         * @see isValid()
         *
         * @return bool true if and only if this title can be used to perform an edit.
         */
        public function canExist() {
                // NOTE: Don't use getArticleID(), we don't want to
                // trigger a database query here. This check is supposed to
                // act as an optimization, not add extra cost.
                if ( $this->mArticleID > 0 ) {
                        // It exists, so it can exist.
                        return true;
                }

                // NOTE: we call the relatively expensive isValid() method further down,
                // but we can bail out early if we already know the title is invalid.
                if ( $this->mIsValid === false ) {
                        // It's invalid, so it can't exist.
                        return false;
                }

                if ( $this->getNamespace() < NS_MAIN ) {
                        // It's a special page, so it can't exist in the database.
                        return false;
                }

                if ( $this->isExternal() ) {
                        // If it's external, it's not local, so it can't exist.
                        return false;
                }

                if ( $this->getText() === '' ) {
                        // The title has no text, so it can't exist in the database.
                        // It's probably an on-page section link, like "#something".
                        return false;
                }

                // Double check that the title is valid.
                return $this->isValid();
        }

        /**
         * Can this title be added to a user's watchlist?
         *
         * False for relative section links (with getText() === ''),
         * interwiki links (with getInterwiki() !== ''), and pages in NS_SPECIAL.
         *
         * @return bool
         */
        public function isWatchable() {
                $nsInfo = MediaWikiServices::getInstance()->getNamespaceInfo();
                return $this->getText() !== '' && !$this->isExternal() &&
                        $nsInfo->isWatchable( $this->mNamespace );
        }

        /**
         * Returns true if this is a special page.
         *
         * @return bool
         */
        public function isSpecialPage() {
                return $this->mNamespace === NS_SPECIAL;
        }

        /**
         * Returns true if this title resolves to the named special page
         *
         * @param string $name The special page name
         * @return bool
         */
        public function isSpecial( $name ) {
                if ( $this->isSpecialPage() ) {
                        list( $thisName, /* $subpage */ ) =
                                MediaWikiServices::getInstance()->getSpecialPageFactory()->
                                        resolveAlias( $this->mDbkeyform );
                        if ( $name == $thisName ) {
                                return true;
                        }
                }
                return false;
        }

        /**
         * If the Title refers to a special page alias which is not the local default, resolve
         * the alias, and localise the name as necessary.  Otherwise, return $this
         *
         * @return Title
         */
        public function fixSpecialName() {
                if ( $this->isSpecialPage() ) {
                        $spFactory = MediaWikiServices::getInstance()->getSpecialPageFactory();
                        list( $canonicalName, $par ) = $spFactory->resolveAlias( $this->mDbkeyform );
                        if ( $canonicalName ) {
                                $localName = $spFactory->getLocalNameFor( $canonicalName, $par );
                                if ( $localName != $this->mDbkeyform ) {
                                        return self::makeTitle( NS_SPECIAL, $localName );
                                }
                        }
                }
                return $this;
        }

        /**
         * Returns true if the title is inside the specified namespace.
         *
         * Please make use of this instead of comparing to getNamespace()
         * This function is much more resistant to changes we may make
         * to namespaces than code that makes direct comparisons.
         * @param int $ns The namespace
         * @return bool
         * @since 1.19
         */
        public function inNamespace( $ns ) {
                return MediaWikiServices::getInstance()->getNamespaceInfo()->
                        equals( $this->mNamespace, $ns );
        }

        /**
         * Returns true if the title is inside one of the specified namespaces.
         *
         * @param int|int[] ...$namespaces The namespaces to check for
         * @return bool
         * @since 1.19
         */
        public function inNamespaces( ...$namespaces ) {
                if ( count( $namespaces ) > 0 && is_array( $namespaces[0] ) ) {
                        $namespaces = $namespaces[0];
                }

                foreach ( $namespaces as $ns ) {
                        if ( $this->inNamespace( $ns ) ) {
                                return true;
                        }
                }

                return false;
        }

        /**
         * Returns true if the title has the same subject namespace as the
         * namespace specified.
         * For example this method will take NS_USER and return true if namespace
         * is either NS_USER or NS_USER_TALK since both of them have NS_USER
         * as their subject namespace.
         *
         * This is MUCH simpler than individually testing for equivalence
         * against both NS_USER and NS_USER_TALK, and is also forward compatible.
         * @since 1.19
         * @param int $ns
         * @return bool
         */
        public function hasSubjectNamespace( $ns ) {
                return MediaWikiServices::getInstance()->getNamespaceInfo()->
                        subjectEquals( $this->mNamespace, $ns );
        }

        /**
         * Is this Title in a namespace which contains content?
         * In other words, is this a content page, for the purposes of calculating
         * statistics, etc?
         *
         * @return bool
         */
        public function isContentPage() {
                return MediaWikiServices::getInstance()->getNamespaceInfo()->
                        isContent( $this->mNamespace );
        }

        /**
         * Would anybody with sufficient privileges be able to move this page?
         * Some pages just aren't movable.
         *
         * @return bool
         */
        public function isMovable() {
                if (
                        !MediaWikiServices::getInstance()->getNamespaceInfo()->
                                isMovable( $this->mNamespace ) || $this->isExternal()
                ) {
                        // Interwiki title or immovable namespace. Hooks don't get to override here
                        return false;
                }

                $result = true;
                Hooks::runner()->onTitleIsMovable( $this, $result );
                return $result;
        }

        /**
         * Is this the mainpage?
         * @note Title::newFromText seems to be sufficiently optimized by the title
         * cache that we don't need to over-optimize by doing direct comparisons and
         * accidentally creating new bugs where $title->equals( Title::newFromText() )
         * ends up reporting something differently than $title->isMainPage();
         *
         * @since 1.18
         * @return bool
         */
        public function isMainPage() {
                return $this->equals( self::newMainPage() );
        }

        /**
         * Is this a subpage?
         *
         * @return bool
         */
        public function isSubpage() {
                return MediaWikiServices::getInstance()->getNamespaceInfo()->
                        hasSubpages( $this->mNamespace )
                        ? strpos( $this->getText(), '/' ) !== false
                        : false;
        }

        /**
         * Is this a conversion table for the LanguageConverter?
         *
         * @return bool
         */
        public function isConversionTable() {
                // @todo ConversionTable should become a separate content model.

                return $this->mNamespace === NS_MEDIAWIKI &&
                        strpos( $this->getText(), 'Conversiontable/' ) === 0;
        }

        /**
         * Does that page contain wikitext, or it is JS, CSS or whatever?
         *
         * @return bool
         */
        public function isWikitextPage() {
                return $this->hasContentModel( CONTENT_MODEL_WIKITEXT );
        }

        /**
         * Could this MediaWiki namespace page contain custom CSS, JSON, or JavaScript for the
         * global UI. This is generally true for pages in the MediaWiki namespace having
         * CONTENT_MODEL_CSS, CONTENT_MODEL_JSON, or CONTENT_MODEL_JAVASCRIPT.
         *
         * This method does *not* return true for per-user JS/JSON/CSS. Use isUserConfigPage()
         * for that!
         *
         * Note that this method should not return true for pages that contain and show
         * "inactive" CSS, JSON, or JS.
         *
         * @return bool
         * @since 1.31
         */
        public function isSiteConfigPage() {
                return (
                        $this->isSiteCssConfigPage()
                        || $this->isSiteJsonConfigPage()
                        || $this->isSiteJsConfigPage()
                );
        }

        /**
         * Is this a "config" (.css, .json, or .js) sub-page of a user page?
         *
         * @return bool
         * @since 1.31
         */
        public function isUserConfigPage() {
                return (
                        $this->isUserCssConfigPage()
                        || $this->isUserJsonConfigPage()
                        || $this->isUserJsConfigPage()
                );
        }

        /**
         * Trim down a .css, .json, or .js subpage title to get the corresponding skin name
         *
         * @return string Containing skin name from .css, .json, or .js subpage title
         * @since 1.31
         */
        public function getSkinFromConfigSubpage() {
                $subpage = explode( '/', $this->mTextform );
                $subpage = $subpage[count( $subpage ) - 1];
                $lastdot = strrpos( $subpage, '.' );
                if ( $lastdot === false ) {
                        return $subpage; # Never happens: only called for names ending in '.css'/'.json'/'.js'
                }
                return substr( $subpage, 0, $lastdot );
        }

        /**
         * Is this a CSS "config" sub-page of a user page?
         *
         * @return bool
         * @since 1.31
         */
        public function isUserCssConfigPage() {
                return (
                        $this->mNamespace === NS_USER
                        && $this->isSubpage()
                        && $this->hasContentModel( CONTENT_MODEL_CSS )
                );
        }

        /**
         * Is this a JSON "config" sub-page of a user page?
         *
         * @return bool
         * @since 1.31
         */
        public function isUserJsonConfigPage() {
                return (
                        $this->mNamespace === NS_USER
                        && $this->isSubpage()
                        && $this->hasContentModel( CONTENT_MODEL_JSON )
                );
        }

        /**
         * Is this a JS "config" sub-page of a user page?
         *
         * @return bool
         * @since 1.31
         */
        public function isUserJsConfigPage() {
                return (
                        $this->mNamespace === NS_USER
                        && $this->isSubpage()
                        && $this->hasContentModel( CONTENT_MODEL_JAVASCRIPT )
                );
        }

        /**
         * Is this a sitewide CSS "config" page?
         *
         * @return bool
         * @since 1.32
         */
        public function isSiteCssConfigPage() {
                return (
                        $this->mNamespace === NS_MEDIAWIKI
                        && (
                                $this->hasContentModel( CONTENT_MODEL_CSS )
                                // paranoia - a MediaWiki: namespace page with mismatching extension and content
                                // model is probably by mistake and might get handled incorrectly (see e.g. T112937)
                                || substr( $this->mDbkeyform, -4 ) === '.css'
                        )
                );
        }

        /**
         * Is this a sitewide JSON "config" page?
         *
         * @return bool
         * @since 1.32
         */
        public function isSiteJsonConfigPage() {
                return (
                        $this->mNamespace === NS_MEDIAWIKI
                        && (
                                $this->hasContentModel( CONTENT_MODEL_JSON )
                                // paranoia - a MediaWiki: namespace page with mismatching extension and content
                                // model is probably by mistake and might get handled incorrectly (see e.g. T112937)
                                || substr( $this->mDbkeyform, -5 ) === '.json'
                        )
                );
        }

        /**
         * Is this a sitewide JS "config" page?
         *
         * @return bool
         * @since 1.31
         */
        public function isSiteJsConfigPage() {
                return (
                        $this->mNamespace === NS_MEDIAWIKI
                        && (
                                $this->hasContentModel( CONTENT_MODEL_JAVASCRIPT )
                                // paranoia - a MediaWiki: namespace page with mismatching extension and content
                                // model is probably by mistake and might get handled incorrectly (see e.g. T112937)
                                || substr( $this->mDbkeyform, -3 ) === '.js'
                        )
                );
        }

        /**
         * Is this a message which can contain raw HTML?
         *
         * @return bool
         * @since 1.32
         */
        public function isRawHtmlMessage() {
                global $wgRawHtmlMessages;

                if ( !$this->inNamespace( NS_MEDIAWIKI ) ) {
                        return false;
                }
                $message = lcfirst( $this->getRootTitle()->getDBkey() );
                return in_array( $message, $wgRawHtmlMessages, true );
        }

        /**
         * Is this a talk page of some sort?
         *
         * @return bool
         */
        public function isTalkPage() {
                return MediaWikiServices::getInstance()->getNamespaceInfo()->
                        isTalk( $this->mNamespace );
        }

        /**
         * Get a Title object associated with the talk page of this article
         *
         * @deprecated since 1.34, use getTalkPageIfDefined() or NamespaceInfo::getTalkPage()
         *             with NamespaceInfo::canHaveTalkPage(). Note that the new method will
         *             throw if asked for the talk page of a section-only link, or of an interwiki
         *             link.
         * @return Title The object for the talk page
         * @throws MWException if $target doesn't have talk pages, e.g. because it's in NS_SPECIAL
         *         or because it's a relative link, or an interwiki link.
         */
        public function getTalkPage() {
                // NOTE: The equivalent code in NamespaceInfo is less lenient about producing invalid titles.
                //       Instead of failing on invalid titles, let's just log the issue for now.
                //       See the discussion on T227817.

                // Is this the same title?
                $talkNS = MediaWikiServices::getInstance()->getNamespaceInfo()->getTalk( $this->mNamespace );
                if ( $this->mNamespace == $talkNS ) {
                        return $this;
                }

                $title = self::makeTitle( $talkNS, $this->mDbkeyform );

                $this->warnIfPageCannotExist( $title, __METHOD__ );

                return $title;
                // TODO: replace the above with the code below:
                // return self::castFromLinkTarget(
                // MediaWikiServices::getInstance()->getNamespaceInfo()->getTalkPage( $this ) );
        }

        /**
         * Get a Title object associated with the talk page of this article,
         * if such a talk page can exist.
         *
         * @since 1.30
         *
         * @return Title|null The object for the talk page,
         *         or null if no associated talk page can exist, according to canHaveTalkPage().
         */
        public function getTalkPageIfDefined() {
                if ( !$this->canHaveTalkPage() ) {
                        return null;
                }

                return $this->getTalkPage();
        }

        /**
         * Get a title object associated with the subject page of this
         * talk page
         *
         * @deprecated since 1.34, use NamespaceInfo::getSubjectPage
         * @return Title The object for the subject page
         */
        public function getSubjectPage() {
                // Is this the same title?
                $subjectNS = MediaWikiServices::getInstance()->getNamespaceInfo()
                        ->getSubject( $this->mNamespace );
                if ( $this->mNamespace == $subjectNS ) {
                        return $this;
                }
                // NOTE: The equivalent code in NamespaceInfo is less lenient about producing invalid titles.
                //       Instead of failing on invalid titles, let's just log the issue for now.
                //       See the discussion on T227817.
                $title = self::makeTitle( $subjectNS, $this->mDbkeyform );

                $this->warnIfPageCannotExist( $title, __METHOD__ );

                return $title;
                // TODO: replace the above with the code below:
                // return self::castFromLinkTarget(
                // MediaWikiServices::getInstance()->getNamespaceInfo()->getSubjectPage( $this ) );
        }

        /**
         * @param Title $title
         * @param string $method
         *
         * @return bool whether a warning was issued
         */
        private function warnIfPageCannotExist( Title $title, $method ) {
                if ( $this->getText() == '' ) {
                        wfLogWarning(
                                $method . ': called on empty title ' . $this->getFullText() . ', returning '
                                . $title->getFullText()
                        );

                        return true;
                }

                if ( $this->getInterwiki() !== '' ) {
                        wfLogWarning(
                                $method . ': called on interwiki title ' . $this->getFullText() . ', returning '
                                . $title->getFullText()
                        );

                        return true;
                }

                return false;
        }

        /**
         * Get the other title for this page, if this is a subject page
         * get the talk page, if it is a subject page get the talk page
         *
         * @deprecated since 1.34, use NamespaceInfo::getAssociatedPage
         * @since 1.25
         * @throws MWException If the page doesn't have an other page
         * @return Title
         */
        public function getOtherPage() {
                // NOTE: Depend on the methods in this class instead of their equivalent in NamespaceInfo,
                //       until their semantics has become exactly the same.
                //       See the discussion on T227817.
                if ( $this->isSpecialPage() ) {
                        throw new MWException( 'Special pages cannot have other pages' );
                }
                if ( $this->isTalkPage() ) {
                        return $this->getSubjectPage();
                } else {
                        if ( !$this->canHaveTalkPage() ) {
                                throw new MWException( "{$this->getPrefixedText()} does not have an other page" );
                        }
                        return $this->getTalkPage();
                }
                // TODO: replace the above with the code below:
                // return self::castFromLinkTarget(
                // MediaWikiServices::getInstance()->getNamespaceInfo()->getAssociatedPage( $this ) );
        }

        /**
         * Get the default namespace index, for when there is no namespace
         *
         * @return int Default namespace index
         */
        public function getDefaultNamespace() {
                return $this->mDefaultNamespace;
        }

        /**
         * Get the Title fragment (i.e.\ the bit after the #) in text form
         *
         * Use Title::hasFragment to check for a fragment
         *
         * @return string Title fragment
         */
        public function getFragment() {
                return $this->mFragment;
        }

        /**
         * Check if a Title fragment is set
         *
         * @return bool
         * @since 1.23
         */
        public function hasFragment() {
                return $this->mFragment !== '';
        }

        /**
         * Get the fragment in URL form, including the "#" character if there is one
         *
         * @return string Fragment in URL form
         */
        public function getFragmentForURL() {
                if ( !$this->hasFragment() ) {
                        return '';
                } elseif ( $this->isExternal() ) {
                        // Note: If the interwiki is unknown, it's treated as a namespace on the local wiki,
                        // so we treat it like a local interwiki.
                        $interwiki = self::getInterwikiLookup()->fetch( $this->mInterwiki );
                        if ( $interwiki && !$interwiki->isLocal() ) {
                                return '#' . Sanitizer::escapeIdForExternalInterwiki( $this->mFragment );
                        }
                }

                return '#' . Sanitizer::escapeIdForLink( $this->mFragment );
        }

        /**
         * Set the fragment for this title. Removes the first character from the
         * specified fragment before setting, so it assumes you're passing it with
         * an initial "#".
         *
         * Deprecated for public use, use Title::makeTitle() with fragment parameter,
         * or Title::createFragmentTarget().
         * Still in active use privately.
         *
         * @internal
         * @param string $fragment Text
         */
        public function setFragment( $fragment ) {
                $this->mFragment = strtr( substr( $fragment, 1 ), '_', ' ' );
        }

        /**
         * Creates a new Title for a different fragment of the same page.
         *
         * @since 1.27
         * @param string $fragment
         * @return Title
         */
        public function createFragmentTarget( $fragment ) {
                return self::makeTitle(
                        $this->mNamespace,
                        $this->getText(),
                        $fragment,
                        $this->mInterwiki
                );
        }

        /**
         * Prefix some arbitrary text with the namespace or interwiki prefix
         * of this object
         *
         * @param string $name The text
         * @return string The prefixed text
         */
        private function prefix( $name ) {
                $p = '';
                if ( $this->isExternal() ) {
                        $p = $this->mInterwiki . ':';
                }

                if ( $this->mNamespace != 0 ) {
                        $nsText = $this->getNsText();

                        if ( $nsText === false ) {
                                // See T165149. Awkward, but better than erroneously linking to the main namespace.
                                $nsText = MediaWikiServices::getInstance()->getContentLanguage()->
                                        getNsText( NS_SPECIAL ) . ":Badtitle/NS{$this->mNamespace}";
                        }

                        $p .= $nsText . ':';
                }
                return $p . $name;
        }

        /**
         * Get the prefixed database key form
         *
         * @return string The prefixed title, with underscores and
         *  any interwiki and namespace prefixes
         */
        public function getPrefixedDBkey() {
                $s = $this->prefix( $this->mDbkeyform );
                $s = strtr( $s, ' ', '_' );
                return $s;
        }

        /**
         * Get the prefixed title with spaces.
         * This is the form usually used for display
         *
         * @return string The prefixed title, with spaces
         */
        public function getPrefixedText() {
                if ( $this->prefixedText === null ) {
                        $s = $this->prefix( $this->mTextform );
                        $s = strtr( $s, '_', ' ' );
                        $this->prefixedText = $s;
                }
                return $this->prefixedText;
        }

        /**
         * Return a string representation of this title
         *
         * @return string Representation of this title
         */
        public function __toString() {
                return $this->getPrefixedText();
        }

        /**
         * Get the prefixed title with spaces, plus any fragment
         * (part beginning with '#')
         *
         * @return string The prefixed title, with spaces and the fragment, including '#'
         */
        public function getFullText() {
                $text = $this->getPrefixedText();
                if ( $this->hasFragment() ) {
                        $text .= '#' . $this->mFragment;
                }
                return $text;
        }

        /**
         * Finds the first or last subpage divider (slash) in the string.
         * Any leading sequence of slashes is ignored, since it does not divide
         * two parts of the string. Considering leading slashes dividers would
         * result in empty root title or base title (T229443).
         *
         * Note that trailing slashes are considered dividers, and empty subpage
         * names are allowed.
         *
         * @param string $text
         * @param int $dir -1 for the last or +1 for the first divider.
         *
         * @return false|int
         */
        private function findSubpageDivider( $text, $dir ) {
                $top = strlen( $text ) - 1;
                $bottom = 0;

                while ( $bottom < $top && $text[$bottom] === '/' ) {
                        $bottom++;
                }

                if ( $top < $bottom ) {
                        return false;
                }

                if ( $dir > 0 ) {
                        $idx = $bottom;
                        while ( $idx <= $top && $text[$idx] !== '/' ) {
                                $idx++;
                        }
                } else {
                        $idx = $top;
                        while ( $idx > $bottom && $text[$idx] !== '/' ) {
                                $idx--;
                        }
                }

                if ( $idx < $bottom || $idx > $top ) {
                        return false;
                }

                if ( $idx < 1 ) {
                        return false;
                }

                return $idx;
        }

        /**
         * Whether this Title's namespace has subpages enabled.
         * @return bool
         */
        private function hasSubpagesEnabled() {
                return MediaWikiServices::getInstance()->getNamespaceInfo()->
                        hasSubpages( $this->mNamespace );
        }

        /**
         * Get the root page name text without a namespace, i.e. the leftmost part before any slashes
         *
         * @note the return value may contain trailing whitespace and is thus
         * not safe for use with makeTitle or TitleValue.
         *
         * @par Example:
         * @code
         * Title::newFromText('User:Foo/Bar/Baz')->getRootText();
         * # returns: 'Foo'
         * @endcode
         *
         * @return string Root name
         * @since 1.20
         */
        public function getRootText() {
                $text = $this->getText();
                if ( !$this->hasSubpagesEnabled() ) {
                        return $text;
                }

                $firstSlashPos = $this->findSubpageDivider( $text, +1 );
                // Don't discard the real title if there's no subpage involved
                if ( $firstSlashPos === false ) {
                        return $text;
                }

                return substr( $text, 0, $firstSlashPos );
        }

        /**
         * Get the root page name title, i.e. the leftmost part before any slashes
         *
         * @par Example:
         * @code
         * Title::newFromText('User:Foo/Bar/Baz')->getRootTitle();
         * # returns: Title{User:Foo}
         * @endcode
         *
         * @return Title Root title
         * @since 1.20
         */
        public function getRootTitle() {
                $title = self::makeTitleSafe( $this->mNamespace, $this->getRootText() );
                Assert::postcondition(
                        $title !== null,
                        'makeTitleSafe() should always return a Title for the text returned by getRootText().'
                );
                return $title;
        }

        /**
         * Get the base page name without a namespace, i.e. the part before the subpage name
         *
         * @note the return value may contain trailing whitespace and is thus
         * not safe for use with makeTitle or TitleValue.
         *
         * @par Example:
         * @code
         * Title::newFromText('User:Foo/Bar/Baz')->getBaseText();
         * # returns: 'Foo/Bar'
         * @endcode
         *
         * @return string Base name
         */
        public function getBaseText() {
                $text = $this->getText();
                if ( !$this->hasSubpagesEnabled() ) {
                        return $text;
                }

                $lastSlashPos = $this->findSubpageDivider( $text, -1 );
                // Don't discard the real title if there's no subpage involved
                if ( $lastSlashPos === false ) {
                        return $text;
                }

                return substr( $text, 0, $lastSlashPos );
        }

        /**
         * Get the base page name title, i.e. the part before the subpage name.
         *
         * @par Example:
         * @code
         * Title::newFromText('User:Foo/Bar/Baz')->getBaseTitle();
         * # returns: Title{User:Foo/Bar}
         * @endcode
         *
         * @return Title Base title
         * @since 1.20
         */
        public function getBaseTitle() {
                $title = self::makeTitleSafe( $this->mNamespace, $this->getBaseText() );
                Assert::postcondition(
                        $title !== null,
                        'makeTitleSafe() should always return a Title for the text returned by getBaseText().'
                );
                return $title;
        }

        /**
         * Get the lowest-level subpage name, i.e. the rightmost part after any slashes
         *
         * @par Example:
         * @code
         * Title::newFromText('User:Foo/Bar/Baz')->getSubpageText();
         * # returns: "Baz"
         * @endcode
         *
         * @return string Subpage name
         */
        public function getSubpageText() {
                $text = $this->getText();
                if ( !$this->hasSubpagesEnabled() ) {
                        return $text;
                }

                $lastSlashPos = $this->findSubpageDivider( $text, -1 );
                if ( $lastSlashPos === false ) {
                        // T256922 - Return the title text if no subpages
                        return $text;
                }
                return substr( $text, $lastSlashPos + 1 );
        }

        /**
         * Get the title for a subpage of the current page
         *
         * @par Example:
         * @code
         * Title::newFromText('User:Foo/Bar/Baz')->getSubpage("Asdf");
         * # returns: Title{User:Foo/Bar/Baz/Asdf}
         * @endcode
         *
         * @param string $text The subpage name to add to the title
         * @return Title|null Subpage title, or null on an error
         * @since 1.20
         */
        public function getSubpage( $text ) {
                return self::makeTitleSafe(
                        $this->mNamespace,
                        $this->getText() . '/' . $text,
                        '',
                        $this->mInterwiki
                );
        }

        /**
         * Get a URL-encoded form of the subpage text
         *
         * @return string URL-encoded subpage name
         */
        public function getSubpageUrlForm() {
                $text = $this->getSubpageText();
                $text = wfUrlencode( strtr( $text, ' ', '_' ) );
                return $text;
        }

        /**
         * Get a URL-encoded title (not an actual URL) including interwiki
         *
         * @return string The URL-encoded form
         */
        public function getPrefixedURL() {
                $s = $this->prefix( $this->mDbkeyform );
                $s = wfUrlencode( strtr( $s, ' ', '_' ) );
                return $s;
        }

        /**
         * Helper to fix up the get{Canonical,Full,Link,Local,Internal}URL args
         * get{Canonical,Full,Link,Local,Internal}URL methods accepted an optional
         * second argument named variant. This was deprecated in favor
         * of passing an array of option with a "variant" key
         * Once $query2 is removed for good, this helper can be dropped
         * and the wfArrayToCgi moved to getLocalURL();
         *
         * @since 1.19 (r105919)
         * @param array|string $query
         * @param string|string[]|bool $query2
         * @return string
         */
        private static function fixUrlQueryArgs( $query, $query2 = false ) {
                if ( $query2 !== false ) {
                        wfDeprecatedMsg( "Title::get{Canonical,Full,Link,Local,Internal}URL " .
                                "method called with a second parameter is deprecated since MediaWiki 1.19. " .
                                "Add your parameter to an array passed as the first parameter.", "1.19" );
                }
                if ( is_array( $query ) ) {
                        $query = wfArrayToCgi( $query );
                }
                if ( $query2 ) {
                        if ( is_string( $query2 ) ) {
                                // $query2 is a string, we will consider this to be
                                // a deprecated $variant argument and add it to the query
                                $query2 = wfArrayToCgi( [ 'variant' => $query2 ] );
                        } else {
                                $query2 = wfArrayToCgi( $query2 );
                        }
                        // If we have $query content add a & to it first
                        if ( $query ) {
                                $query .= '&';
                        }
                        // Now append the queries together
                        $query .= $query2;
                }
                return $query;
        }

        /**
         * Get a real URL referring to this title, with interwiki link and
         * fragment
         *
         * @see self::getLocalURL for the arguments.
         * @see wfExpandUrl
         * @param string|array $query
         * @param string|string[]|bool $query2
         * @param string|int|null $proto Protocol type to use in URL
         * @return string The URL
         */
        public function getFullURL( $query = '', $query2 = false, $proto = PROTO_RELATIVE ) {
                $query = self::fixUrlQueryArgs( $query, $query2 );

                # Hand off all the decisions on urls to getLocalURL
                $url = $this->getLocalURL( $query );

                # Expand the url to make it a full url. Note that getLocalURL has the
                # potential to output full urls for a variety of reasons, so we use
                # wfExpandUrl instead of simply prepending $wgServer
                $url = wfExpandUrl( $url, $proto );

                # Finally, add the fragment.
                $url .= $this->getFragmentForURL();
                Hooks::runner()->onGetFullURL( $this, $url, $query );
                return $url;
        }

        /**
         * Get a url appropriate for making redirects based on an untrusted url arg
         *
         * This is basically the same as getFullUrl(), but in the case of external
         * interwikis, we send the user to a landing page, to prevent possible
         * phishing attacks and the like.
         *
         * @note Uses current protocol by default, since technically relative urls
         *   aren't allowed in redirects per HTTP spec, so this is not suitable for
         *   places where the url gets cached, as might pollute between
         *   https and non-https users.
         * @see self::getLocalURL for the arguments.
         * @param array|string $query
         * @param string $proto Protocol type to use in URL
         * @return string A url suitable to use in an HTTP location header.
         */
        public function getFullUrlForRedirect( $query = '', $proto = PROTO_CURRENT ) {
                $target = $this;
                if ( $this->isExternal() ) {
                        $target = SpecialPage::getTitleFor(
                                'GoToInterwiki',
                                $this->getPrefixedDBkey()
                        );
                }
                return $target->getFullURL( $query, false, $proto );
        }

        /**
         * Get a URL with no fragment or server name (relative URL) from a Title object.
         * If this page is generated with action=render, however,
         * $wgServer is prepended to make an absolute URL.
         *
         * @see self::getFullURL to always get an absolute URL.
         * @see self::getLinkURL to always get a URL that's the simplest URL that will be
         *  valid to link, locally, to the current Title.
         * @see self::newFromText to produce a Title object.
         *
         * @param string|array $query An optional query string,
         *   not used for interwiki links. Can be specified as an associative array as well,
         *   e.g., [ 'action' => 'edit' ] (keys and values will be URL-escaped).
         *   Some query patterns will trigger various shorturl path replacements.
         * @param string|string[]|bool $query2 An optional secondary query array. This one MUST
         *   be an array. If a string is passed it will be interpreted as a deprecated
         *   variant argument and urlencoded into a variant= argument.
         *   This second query argument will be added to the $query
         *   The second parameter is deprecated since 1.19. Pass it as a key,value
         *   pair in the first parameter array instead.
         *
         * @return string String of the URL.
         */
        public function getLocalURL( $query = '', $query2 = false ) {
                global $wgArticlePath, $wgScript, $wgServer, $wgRequest, $wgMainPageIsDomainRoot;

                $query = self::fixUrlQueryArgs( $query, $query2 );

                $interwiki = self::getInterwikiLookup()->fetch( $this->mInterwiki );
                if ( $interwiki ) {
                        $namespace = $this->getNsText();
                        if ( $namespace != '' ) {
                                # Can this actually happen? Interwikis shouldn't be parsed.
                                # Yes! It can in interwiki transclusion. But... it probably shouldn't.
                                $namespace .= ':';
                        }
                        $url = $interwiki->getURL( $namespace . $this->mDbkeyform );
                        $url = wfAppendQuery( $url, $query );
                } else {
                        $dbkey = wfUrlencode( $this->getPrefixedDBkey() );
                        if ( $query == '' ) {
                                $url = str_replace( '$1', $dbkey, $wgArticlePath );
                                Hooks::runner()->onGetLocalURL__Article( $this, $url );
                        } else {
                                global $wgVariantArticlePath, $wgActionPaths;
                                $url = false;
                                $matches = [];

                                $articlePaths = PathRouter::getActionPaths( $wgActionPaths, $wgArticlePath );

                                if ( $articlePaths
                                        && preg_match( '/^(.*&|)action=([^&]*)(&(.*)|)$/', $query, $matches )
                                ) {
                                        $action = urldecode( $matches[2] );
                                        if ( isset( $articlePaths[$action] ) ) {
                                                $query = $matches[1];
                                                if ( isset( $matches[4] ) ) {
                                                        $query .= $matches[4];
                                                }
                                                $url = str_replace( '$1', $dbkey, $articlePaths[$action] );
                                                if ( $query != '' ) {
                                                        $url = wfAppendQuery( $url, $query );
                                                }
                                        }
                                }

                                if ( $url === false
                                        && $wgVariantArticlePath
                                        && preg_match( '/^variant=([^&]*)$/', $query, $matches )
                                        && $this->getPageLanguage()->equals(
                                                MediaWikiServices::getInstance()->getContentLanguage() )
                                        && $this->getPageLanguageConverter()->hasVariants()
                                ) {
                                        $variant = urldecode( $matches[1] );
                                        if ( $this->getPageLanguageConverter()->hasVariant( $variant ) ) {
                                                // Only do the variant replacement if the given variant is a valid
                                                // variant for the page's language.
                                                $url = str_replace( '$2', urlencode( $variant ), $wgVariantArticlePath );
                                                $url = str_replace( '$1', $dbkey, $url );
                                        }
                                }

                                if ( $url === false ) {
                                        if ( $query == '-' ) {
                                                $query = '';
                                        }
                                        $url = "{$wgScript}?title={$dbkey}&{$query}";
                                }
                        }
                        Hooks::runner()->onGetLocalURL__Internal( $this, $url, $query );

                        // @todo FIXME: This causes breakage in various places when we
                        // actually expected a local URL and end up with dupe prefixes.
                        if ( $wgRequest->getVal( 'action' ) == 'render' ) {
                                $url = $wgServer . $url;
                        }
                }

                if ( $wgMainPageIsDomainRoot && $this->isMainPage() && $query === '' ) {
                        return '/';
                }

                Hooks::runner()->onGetLocalURL( $this, $url, $query );
                return $url;
        }

        /**
         * Get a URL that's the simplest URL that will be valid to link, locally,
         * to the current Title.  It includes the fragment, but does not include
         * the server unless action=render is used (or the link is external).  If
         * there's a fragment but the prefixed text is empty, we just return a link
         * to the fragment.
         *
         * The result obviously should not be URL-escaped, but does need to be
         * HTML-escaped if it's being output in HTML.
         *
         * @param string|array $query
         * @param bool $query2
         * @param string|int|bool $proto A PROTO_* constant on how the URL should be expanded,
         *                               or false (default) for no expansion
         * @see self::getLocalURL for the arguments.
         * @return string The URL
         */
        public function getLinkURL( $query = '', $query2 = false, $proto = false ) {
                if ( $this->isExternal() || $proto !== false ) {
                        $ret = $this->getFullURL( $query, $query2, $proto );
                } elseif ( $this->getPrefixedText() === '' && $this->hasFragment() ) {
                        $ret = $this->getFragmentForURL();
                } else {
                        $ret = $this->getLocalURL( $query, $query2 ) . $this->getFragmentForURL();
                }
                return $ret;
        }

        /**
         * Get the URL form for an internal link.
         * - Used in various CDN-related code, in case we have a different
         * internal hostname for the server from the exposed one.
         *
         * This uses $wgInternalServer to qualify the path, or $wgServer
         * if $wgInternalServer is not set. If the server variable used is
         * protocol-relative, the URL will be expanded to http://
         *
         * @see self::getLocalURL for the arguments.
         * @param string|array $query
         * @param string|bool $query2 Deprecated
         * @return string The URL
         */
        public function getInternalURL( $query = '', $query2 = false ) {
                global $wgInternalServer, $wgServer;
                $query = self::fixUrlQueryArgs( $query, $query2 );
                $server = $wgInternalServer !== false ? $wgInternalServer : $wgServer;
                $url = wfExpandUrl( $server . $this->getLocalURL( $query ), PROTO_HTTP );
                Hooks::runner()->onGetInternalURL( $this, $url, $query );
                return $url;
        }

        /**
         * Get the URL for a canonical link, for use in things like IRC and
         * e-mail notifications. Uses $wgCanonicalServer and the
         * GetCanonicalURL hook.
         *
         * NOTE: Unlike getInternalURL(), the canonical URL includes the fragment
         *
         * @see self::getLocalURL for the arguments.
         * @param string|array $query
         * @param string|bool $query2 Deprecated
         * @return string The URL
         * @since 1.18
         */
        public function getCanonicalURL( $query = '', $query2 = false ) {
                $query = self::fixUrlQueryArgs( $query, $query2 );
                $url = wfExpandUrl( $this->getLocalURL( $query ) . $this->getFragmentForURL(), PROTO_CANONICAL );
                Hooks::runner()->onGetCanonicalURL( $this, $url, $query );
                return $url;
        }

        /**
         * Get the edit URL for this Title
         *
         * @return string The URL, or a null string if this is an interwiki link
         */
        public function getEditURL() {
                if ( $this->isExternal() ) {
                        return '';
                }
                $s = $this->getLocalURL( 'action=edit' );

                return $s;
        }

        /**
         * Get a filtered list of all restriction types supported by this wiki.
         * @param bool $exists True to get all restriction types that apply to
         * titles that do exist, False for all restriction types that apply to
         * titles that do not exist
         * @return array
         */
        public static function getFilteredRestrictionTypes( $exists = true ) {
                global $wgRestrictionTypes;
                $types = $wgRestrictionTypes;
                if ( $exists ) {
                        # Remove the create restriction for existing titles
                        $types = array_diff( $types, [ 'create' ] );
                } else {
                        # Only the create and upload restrictions apply to non-existing titles
                        $types = array_intersect( $types, [ 'create', 'upload' ] );
                }
                return $types;
        }

        /**
         * Returns restriction types for the current Title
         *
         * @return array Applicable restriction types
         */
        public function getRestrictionTypes() {
                if ( $this->isSpecialPage() ) {
                        return [];
                }

                $types = self::getFilteredRestrictionTypes( $this->exists() );

                if ( $this->mNamespace !== NS_FILE ) {
                        # Remove the upload restriction for non-file titles
                        $types = array_diff( $types, [ 'upload' ] );
                }

                Hooks::runner()->onTitleGetRestrictionTypes( $this, $types );

                wfDebug( __METHOD__ . ': applicable restrictions to [[' .
                        $this->getPrefixedText() . ']] are {' . implode( ',', $types ) . "}" );

                return $types;
        }

        /**
         * Is this title subject to title protection?
         * Title protection is the one applied against creation of such title.
         *
         * @return array|bool An associative array representing any existent title
         *   protection, or false if there's none.
         */
        public function getTitleProtection() {
                $protection = $this->getTitleProtectionInternal();
                if ( $protection ) {
                        if ( $protection['permission'] == 'sysop' ) {
                                $protection['permission'] = 'editprotected'; // B/C
                        }
                        if ( $protection['permission'] == 'autoconfirmed' ) {
                                $protection['permission'] = 'editsemiprotected'; // B/C
                        }
                }
                return $protection;
        }

        /**
         * Fetch title protection settings
         *
         * To work correctly, $this->loadRestrictions() needs to have access to the
         * actual protections in the database without munging 'sysop' =>
         * 'editprotected' and 'autoconfirmed' => 'editsemiprotected'. Other
         * callers probably want $this->getTitleProtection() instead.
         *
         * @return array|bool
         */
        protected function getTitleProtectionInternal() {
                // Can't protect pages in special namespaces
                if ( $this->mNamespace < 0 ) {
                        return false;
                }

                // Can't protect pages that exist.
                if ( $this->exists() ) {
                        return false;
                }

                if ( $this->mTitleProtection === null ) {
                        $dbr = wfGetDB( DB_REPLICA );
                        $commentStore = CommentStore::getStore();
                        $commentQuery = $commentStore->getJoin( 'pt_reason' );
                        $res = $dbr->select(
                                [ 'protected_titles' ] + $commentQuery['tables'],
                                [
                                        'user' => 'pt_user',
                                        'expiry' => 'pt_expiry',
                                        'permission' => 'pt_create_perm'
                                ] + $commentQuery['fields'],
                                [ 'pt_namespace' => $this->mNamespace, 'pt_title' => $this->mDbkeyform ],
                                __METHOD__,
                                [],
                                $commentQuery['joins']
                        );

                        // fetchRow returns false if there are no rows.
                        $row = $dbr->fetchRow( $res );
                        if ( $row ) {
                                $this->mTitleProtection = [
                                        'user' => $row['user'],
                                        'expiry' => $dbr->decodeExpiry( $row['expiry'] ),
                                        'permission' => $row['permission'],
                                        'reason' => $commentStore->getComment( 'pt_reason', $row )->text,
                                ];
                        } else {
                                $this->mTitleProtection = false;
                        }
                }
                return $this->mTitleProtection;
        }

        /**
         * Remove any title protection due to page existing
         */
        public function deleteTitleProtection() {
                $dbw = wfGetDB( DB_MASTER );

                $dbw->delete(
                        'protected_titles',
                        [ 'pt_namespace' => $this->mNamespace, 'pt_title' => $this->mDbkeyform ],
                        __METHOD__
                );
                $this->mTitleProtection = false;
        }

        /**
         * Is this page "semi-protected" - the *only* protection levels are listed
         * in $wgSemiprotectedRestrictionLevels?
         *
         * @param string $action Action to check (default: edit)
         * @return bool
         */
        public function isSemiProtected( $action = 'edit' ) {
                global $wgSemiprotectedRestrictionLevels;

                $restrictions = $this->getRestrictions( $action );
                $semi = $wgSemiprotectedRestrictionLevels;
                if ( !$restrictions || !$semi ) {
                        // Not protected, or all protection is full protection
                        return false;
                }

                // Remap autoconfirmed to editsemiprotected for BC
                foreach ( array_keys( $semi, 'autoconfirmed' ) as $key ) {
                        $semi[$key] = 'editsemiprotected';
                }
                foreach ( array_keys( $restrictions, 'autoconfirmed' ) as $key ) {
                        $restrictions[$key] = 'editsemiprotected';
                }

                return !array_diff( $restrictions, $semi );
        }

        /**
         * Does the title correspond to a protected article?
         *
         * @param string $action The action the page is protected from,
         * by default checks all actions.
         * @return bool
         */
        public function isProtected( $action = '' ) {
                global $wgRestrictionLevels;

                $restrictionTypes = $this->getRestrictionTypes();

                # Special pages have inherent protection
                if ( $this->isSpecialPage() ) {
                        return true;
                }

                # Check regular protection levels
                foreach ( $restrictionTypes as $type ) {
                        if ( $action == $type || $action == '' ) {
                                $r = $this->getRestrictions( $type );
                                foreach ( $wgRestrictionLevels as $level ) {
                                        if ( in_array( $level, $r ) && $level != '' ) {
                                                return true;
                                        }
                                }
                        }
                }

                return false;
        }

        /**
         * Determines if $user is unable to edit this page because it has been protected
         * by $wgNamespaceProtection.
         *
         * @deprecated since 1.34 Don't use this function in new code.
         * @param User $user User object to check permissions
         * @return bool
         */
        public function isNamespaceProtected( User $user ) {
                global $wgNamespaceProtection;

                if ( isset( $wgNamespaceProtection[$this->mNamespace] ) ) {
                        $permissionManager = MediaWikiServices::getInstance()->getPermissionManager();
                        foreach ( (array)$wgNamespaceProtection[$this->mNamespace] as $right ) {
                                if ( !$permissionManager->userHasRight( $user, $right ) ) {
                                        return true;
                                }
                        }
                }
                return false;
        }

        /**
         * Cascading protection: Return true if cascading restrictions apply to this page, false if not.
         *
         * @return bool If the page is subject to cascading restrictions.
         */
        public function isCascadeProtected() {
                list( $isCascadeProtected, ) = $this->getCascadeProtectionSources( false );
                return $isCascadeProtected;
        }

        /**
         * Determines whether cascading protection sources have already been loaded from
         * the database.
         *
         * @param bool $getPages True to check if the pages are loaded, or false to check
         * if the status is loaded.
         * @return bool Whether or not the specified information has been loaded
         * @since 1.23
         */
        public function areCascadeProtectionSourcesLoaded( $getPages = true ) {
                return $getPages ? $this->mCascadeSources !== null : $this->mHasCascadingRestrictions !== null;
        }

        /**
         * Cascading protection: Get the source of any cascading restrictions on this page.
         *
         * @param bool $getPages Whether or not to retrieve the actual pages
         *        that the restrictions have come from and the actual restrictions
         *        themselves.
         * @return array Two elements: First is an array of Title objects of the
         *        pages from which cascading restrictions have come, false for
         *        none, or true if such restrictions exist but $getPages was not
         *        set. Second is an array like that returned by
         *        Title::getAllRestrictions(), or an empty array if $getPages is
         *        false.
         */
        public function getCascadeProtectionSources( $getPages = true ) {
                $pagerestrictions = [];

                if ( $this->mCascadeSources !== null && $getPages ) {
                        return [ $this->mCascadeSources, $this->mCascadingRestrictions ];
                } elseif ( $this->mHasCascadingRestrictions !== null && !$getPages ) {
                        return [ $this->mHasCascadingRestrictions, $pagerestrictions ];
                }

                $dbr = wfGetDB( DB_REPLICA );

                if ( $this->mNamespace === NS_FILE ) {
                        $tables = [ 'imagelinks', 'page_restrictions' ];
                        $where_clauses = [
                                'il_to' => $this->mDbkeyform,
                                'il_from=pr_page',
                                'pr_cascade' => 1
                        ];
                } else {
                        $tables = [ 'templatelinks', 'page_restrictions' ];
                        $where_clauses = [
                                'tl_namespace' => $this->mNamespace,
                                'tl_title' => $this->mDbkeyform,
                                'tl_from=pr_page',
                                'pr_cascade' => 1
                        ];
                }

                if ( $getPages ) {
                        $cols = [ 'pr_page', 'page_namespace', 'page_title',
                                'pr_expiry', 'pr_type', 'pr_level' ];
                        $where_clauses[] = 'page_id=pr_page';
                        $tables[] = 'page';
                } else {
                        $cols = [ 'pr_expiry' ];
                }

                $res = $dbr->select( $tables, $cols, $where_clauses, __METHOD__ );

                $sources = $getPages ? [] : false;
                $now = wfTimestampNow();

                foreach ( $res as $row ) {
                        $expiry = $dbr->decodeExpiry( $row->pr_expiry );
                        if ( $expiry > $now ) {
                                if ( $getPages ) {
                                        $page_id = $row->pr_page;
                                        $page_ns = $row->page_namespace;
                                        $page_title = $row->page_title;
                                        $sources[$page_id] = self::makeTitle( $page_ns, $page_title );
                                        # Add groups needed for each restriction type if its not already there
                                        # Make sure this restriction type still exists

                                        if ( !isset( $pagerestrictions[$row->pr_type] ) ) {
                                                $pagerestrictions[$row->pr_type] = [];
                                        }

                                        if (
                                                isset( $pagerestrictions[$row->pr_type] )
                                                && !in_array( $row->pr_level, $pagerestrictions[$row->pr_type] )
                                        ) {
                                                $pagerestrictions[$row->pr_type][] = $row->pr_level;
                                        }
                                } else {
                                        $sources = true;
                                }
                        }
                }

                if ( $getPages ) {
                        $this->mCascadeSources = $sources;
                        $this->mCascadingRestrictions = $pagerestrictions;
                } else {
                        $this->mHasCascadingRestrictions = $sources;
                }

                return [ $sources, $pagerestrictions ];
        }

        /**
         * Accessor for mRestrictionsLoaded
         *
         * @return bool Whether or not the page's restrictions have already been
         * loaded from the database
         * @since 1.23
         */
        public function areRestrictionsLoaded() {
                return $this->mRestrictionsLoaded;
        }

        /**
         * Accessor/initialisation for mRestrictions
         *
         * @param string $action Action that permission needs to be checked for
         * @return array Restriction levels needed to take the action. All levels are
         *     required. Note that restriction levels are normally user rights, but 'sysop'
         *     and 'autoconfirmed' are also allowed for backwards compatibility. These should
         *     be mapped to 'editprotected' and 'editsemiprotected' respectively.
         */
        public function getRestrictions( $action ) {
                if ( !$this->mRestrictionsLoaded ) {
                        $this->loadRestrictions();
                }
                return $this->mRestrictions[$action] ?? [];
        }

        /**
         * Accessor/initialisation for mRestrictions
         *
         * @return array Keys are actions, values are arrays as returned by
         *     Title::getRestrictions()
         * @since 1.23
         */
        public function getAllRestrictions() {
                if ( !$this->mRestrictionsLoaded ) {
                        $this->loadRestrictions();
                }
                return $this->mRestrictions;
        }

        /**
         * Get the expiry time for the restriction against a given action
         *
         * @param string $action
         * @return string|bool 14-char timestamp, or 'infinity' if the page is protected forever
         *     or not protected at all, or false if the action is not recognised.
         */
        public function getRestrictionExpiry( $action ) {
                if ( !$this->mRestrictionsLoaded ) {
                        $this->loadRestrictions();
                }
                return $this->mRestrictionsExpiry[$action] ?? false;
        }

        /**
         * Returns cascading restrictions for the current article
         *
         * @return bool
         */
        public function areRestrictionsCascading() {
                if ( !$this->mRestrictionsLoaded ) {
                        $this->loadRestrictions();
                }

                return $this->mCascadeRestriction;
        }

        /**
         * Compiles list of active page restrictions from both page table (pre 1.10)
         * and page_restrictions table for this existing page.
         * Public for usage by LiquidThreads.
         *
         * @param stdClass[] $rows Array of db result objects
         * @param string|null $oldFashionedRestrictions Comma-separated set of permission keys
         * indicating who can move or edit the page from the page table, (pre 1.10) rows.
         * Edit and move sections are separated by a colon
         * Example: "edit=autoconfirmed,sysop:move=sysop"
         */
        public function loadRestrictionsFromRows( $rows, $oldFashionedRestrictions = null ) {
                // This function will only read rows from a table that we migrated away
                // from before adding READ_LATEST support to loadRestrictions, so we
                // don't need to support reading from DB_MASTER here.
                $dbr = wfGetDB( DB_REPLICA );

                $restrictionTypes = $this->getRestrictionTypes();

                foreach ( $restrictionTypes as $type ) {
                        $this->mRestrictions[$type] = [];
                        $this->mRestrictionsExpiry[$type] = 'infinity';
                }

                $this->mCascadeRestriction = false;

                # Backwards-compatibility: also load the restrictions from the page record (old format).
                if ( $oldFashionedRestrictions !== null ) {
                        $this->mOldRestrictions = $oldFashionedRestrictions;
                }

                if ( $this->mOldRestrictions === false ) {
                        $linkCache = MediaWikiServices::getInstance()->getLinkCache();
                        $linkCache->addLinkObj( $this ); # in case we already had an article ID
                        $this->mOldRestrictions = $linkCache->getGoodLinkFieldObj( $this, 'restrictions' );
                }

                if ( $this->mOldRestrictions != '' ) {
                        foreach ( explode( ':', trim( $this->mOldRestrictions ) ) as $restrict ) {
                                $temp = explode( '=', trim( $restrict ) );
                                if ( count( $temp ) == 1 ) {
                                        // old old format should be treated as edit/move restriction
                                        $this->mRestrictions['edit'] = explode( ',', trim( $temp[0] ) );
                                        $this->mRestrictions['move'] = explode( ',', trim( $temp[0] ) );
                                } else {
                                        $restriction = trim( $temp[1] );
                                        if ( $restriction != '' ) { // some old entries are empty
                                                $this->mRestrictions[$temp[0]] = explode( ',', $restriction );
                                        }
                                }
                        }
                }

                if ( count( $rows ) ) {
                        # Current system - load second to make them override.
                        $now = wfTimestampNow();

                        # Cycle through all the restrictions.
                        foreach ( $rows as $row ) {
                                // Don't take care of restrictions types that aren't allowed
                                if ( !in_array( $row->pr_type, $restrictionTypes ) ) {
                                        continue;
                                }

                                $expiry = $dbr->decodeExpiry( $row->pr_expiry );

                                // Only apply the restrictions if they haven't expired!
                                if ( !$expiry || $expiry > $now ) {
                                        $this->mRestrictionsExpiry[$row->pr_type] = $expiry;
                                        $this->mRestrictions[$row->pr_type] = explode( ',', trim( $row->pr_level ) );

                                        $this->mCascadeRestriction = $this->mCascadeRestriction || $row->pr_cascade;
                                }
                        }
                }

                $this->mRestrictionsLoaded = true;
        }

        /**
         * Load restrictions from the page_restrictions table
         *
         * @param string|null $oldFashionedRestrictions Comma-separated set of permission keys
         * indicating who can move or edit the page from the page table, (pre 1.10) rows.
         * Edit and move sections are separated by a colon
         * Example: "edit=autoconfirmed,sysop:move=sysop"
         * @param int $flags A bit field. If self::READ_LATEST is set, skip replicas and read
         *  from the master DB.
         */
        public function loadRestrictions( $oldFashionedRestrictions = null, $flags = 0 ) {
                $readLatest = DBAccessObjectUtils::hasFlags( $flags, self::READ_LATEST );
                if ( $this->mRestrictionsLoaded && !$readLatest ) {
                        return;
                }

                $id = $this->getArticleID( $flags );
                if ( $id ) {
                        $fname = __METHOD__;
                        $loadRestrictionsFromDb = function ( IDatabase $dbr ) use ( $fname, $id ) {
                                return iterator_to_array(
                                        $dbr->select(
                                                'page_restrictions',
                                                [ 'pr_type', 'pr_expiry', 'pr_level', 'pr_cascade' ],
                                                [ 'pr_page' => $id ],
                                                $fname
                                        )
                                );
                        };

                        if ( $readLatest ) {
                                $dbr = wfGetDB( DB_MASTER );
                                $rows = $loadRestrictionsFromDb( $dbr );
                        } else {
                                $cache = MediaWikiServices::getInstance()->getMainWANObjectCache();
                                $rows = $cache->getWithSetCallback(
                                        // Page protections always leave a new null revision
                                        $cache->makeKey( 'page-restrictions', 'v1', $id, $this->getLatestRevID() ),
                                        $cache::TTL_DAY,
                                        function ( $curValue, &$ttl, array &$setOpts ) use ( $loadRestrictionsFromDb ) {
                                                $dbr = wfGetDB( DB_REPLICA );

                                                $setOpts += Database::getCacheSetOptions( $dbr );
                                                $lb = MediaWikiServices::getInstance()->getDBLoadBalancer();
                                                if ( $lb->hasOrMadeRecentMasterChanges() ) {
                                                        // @TODO: cleanup Title cache and caller assumption mess in general
                                                        $ttl = WANObjectCache::TTL_UNCACHEABLE;
                                                }

                                                return $loadRestrictionsFromDb( $dbr );
                                        }
                                );
                        }

                        $this->loadRestrictionsFromRows( $rows, $oldFashionedRestrictions );
                } else {
                        $title_protection = $this->getTitleProtectionInternal();

                        if ( $title_protection ) {
                                $now = wfTimestampNow();
                                $expiry = wfGetDB( DB_REPLICA )->decodeExpiry( $title_protection['expiry'] );

                                if ( !$expiry || $expiry > $now ) {
                                        // Apply the restrictions
                                        $this->mRestrictionsExpiry['create'] = $expiry;
                                        $this->mRestrictions['create'] =
                                                explode( ',', trim( $title_protection['permission'] ) );
                                } else { // Get rid of the old restrictions
                                        $this->mTitleProtection = false;
                                }
                        } else {
                                $this->mRestrictionsExpiry['create'] = 'infinity';
                        }
                        $this->mRestrictionsLoaded = true;
                }
        }

        /**
         * Flush the protection cache in this object and force reload from the database.
         * This is used when updating protection from WikiPage::doUpdateRestrictions().
         */
        public function flushRestrictions() {
                $this->mRestrictionsLoaded = false;
                $this->mTitleProtection = null;
        }

        /**
         * Purge expired restrictions from the page_restrictions table
         *
         * This will purge no more than $wgUpdateRowsPerQuery page_restrictions rows
         */
        public static function purgeExpiredRestrictions() {
                if ( wfReadOnly() ) {
                        return;
                }

                DeferredUpdates::addUpdate( new AtomicSectionUpdate(
                        wfGetDB( DB_MASTER ),
                        __METHOD__,
                        function ( IDatabase $dbw, $fname ) {
                                $config = MediaWikiServices::getInstance()->getMainConfig();
                                $ids = $dbw->selectFieldValues(
                                        'page_restrictions',
                                        'pr_id',
                                        [ 'pr_expiry < ' . $dbw->addQuotes( $dbw->timestamp() ) ],
                                        $fname,
                                        [ 'LIMIT' => $config->get( 'UpdateRowsPerQuery' ) ] // T135470
                                );
                                if ( $ids ) {
                                        $dbw->delete( 'page_restrictions', [ 'pr_id' => $ids ], $fname );
                                }
                        }
                ) );

                DeferredUpdates::addUpdate( new AtomicSectionUpdate(
                        wfGetDB( DB_MASTER ),
                        __METHOD__,
                        function ( IDatabase $dbw, $fname ) {
                                $dbw->delete(
                                        'protected_titles',
                                        [ 'pt_expiry < ' . $dbw->addQuotes( $dbw->timestamp() ) ],
                                        $fname
                                );
                        }
                ) );
        }

        /**
         * Does this have subpages?  (Warning, usually requires an extra DB query.)
         *
         * @return bool
         */
        public function hasSubpages() {
                if (
                        !MediaWikiServices::getInstance()->getNamespaceInfo()->
                                hasSubpages( $this->mNamespace )
                ) {
                        # Duh
                        return false;
                }

                # We dynamically add a member variable for the purpose of this method
                # alone to cache the result.  There's no point in having it hanging
                # around uninitialized in every Title object; therefore we only add it
                # if needed and don't declare it statically.
                if ( $this->mHasSubpages === null ) {
                        $this->mHasSubpages = false;
                        $subpages = $this->getSubpages( 1 );
                        if ( $subpages instanceof TitleArray ) {
                                $this->mHasSubpages = (bool)$subpages->current();
                        }
                }

                return $this->mHasSubpages;
        }

        /**
         * Get all subpages of this page.
         *
         * @param int $limit Maximum number of subpages to fetch; -1 for no limit
         * @return TitleArray|array TitleArray, or empty array if this page's namespace
         *  doesn't allow subpages
         */
        public function getSubpages( $limit = -1 ) {
                if (
                        !MediaWikiServices::getInstance()->getNamespaceInfo()->
                                hasSubpages( $this->mNamespace )
                ) {
                        return [];
                }

                $dbr = wfGetDB( DB_REPLICA );
                $conds = [ 'page_namespace' => $this->mNamespace ];
                $conds[] = 'page_title ' . $dbr->buildLike( $this->mDbkeyform . '/', $dbr->anyString() );
                $options = [];
                if ( $limit > -1 ) {
                        $options['LIMIT'] = $limit;
                }
                return TitleArray::newFromResult(
                        $dbr->select( 'page',
                                [ 'page_id', 'page_namespace', 'page_title', 'page_is_redirect' ],
                                $conds,
                                __METHOD__,
                                $options
                        )
                );
        }

        /**
         * Is there a version of this page in the deletion archive?
         *
         * @deprecated since 1.36. Use self::getDeletedEditsCount()
         * @return int The number of archived revisions
         */
        public function isDeleted() {
                return $this->getDeletedEditsCount();
        }

        /**
         * Is there a version of this page in the deletion archive?
         *
         * @since 1.36
         * @return int The number of archived revisions
         */
        public function getDeletedEditsCount() {
                if ( $this->mNamespace < 0 ) {
                        $n = 0;
                } else {
                        $dbr = wfGetDB( DB_REPLICA );

                        $n = $dbr->selectField( 'archive', 'COUNT(*)',
                                [ 'ar_namespace' => $this->mNamespace, 'ar_title' => $this->mDbkeyform ],
                                __METHOD__
                        );
                        if ( $this->mNamespace === NS_FILE ) {
                                $n += $dbr->selectField( 'filearchive', 'COUNT(*)',
                                        [ 'fa_name' => $this->mDbkeyform ],
                                        __METHOD__
                                );
                        }
                }
                return (int)$n;
        }

        /**
         * Is there a version of this page in the deletion archive?
         *
         * @deprecated since 1.36, Use self::hasDeletedEdits()
         * @return bool
         */
        public function isDeletedQuick() {
                return $this->hasDeletedEdits();
        }

        /**
         * Is there a version of this page in the deletion archive?
         *
         * @since 1.36
         * @return bool
         */
        public function hasDeletedEdits() {
                if ( $this->mNamespace < 0 ) {
                        return false;
                }
                $dbr = wfGetDB( DB_REPLICA );
                $deleted = (bool)$dbr->selectField( 'archive', '1',
                        [ 'ar_namespace' => $this->mNamespace, 'ar_title' => $this->mDbkeyform ],
                        __METHOD__
                );
                if ( !$deleted && $this->mNamespace === NS_FILE ) {
                        $deleted = (bool)$dbr->selectField( 'filearchive', '1',
                                [ 'fa_name' => $this->mDbkeyform ],
                                __METHOD__
                        );
                }
                return $deleted;
        }

        /**
         * Get the article ID for this Title from the link cache,
         * adding it if necessary
         *
         * @param int $flags Either a bitfield of class READ_* constants or GAID_FOR_UPDATE
         * @return int The ID
         */
        public function getArticleID( $flags = 0 ) {
                if ( $this->mNamespace < 0 ) {
                        $this->mArticleID = 0;

                        return $this->mArticleID;
                }

                if ( $flags & self::GAID_FOR_UPDATE ) {
                        $linkCache = MediaWikiServices::getInstance()->getLinkCache();
                        $oldUpdate = $linkCache->forUpdate( true );
                        $linkCache->clearLink( $this );
                        $this->mArticleID = $linkCache->addLinkObj( $this );
                        $linkCache->forUpdate( $oldUpdate );
                } elseif ( DBAccessObjectUtils::hasFlags( $flags, self::READ_LATEST ) ) {
                        // If mArticleID is >0, pageCond() will use it, making it impossible
                        // for the call below to return a different result, e.g. after a
                        // page move.
                        $this->mArticleID = -1;
                        $this->mArticleID = (int)$this->loadFieldFromDB( 'page_id', $flags );
                } elseif ( $this->mArticleID == -1 ) {
                        $linkCache = MediaWikiServices::getInstance()->getLinkCache();
                        $this->mArticleID = $linkCache->addLinkObj( $this );
                }

                return $this->mArticleID;
        }

        /**
         * Is this an article that is a redirect page?
         * Uses link cache, adding it if necessary
         *
         * @param int $flags Either a bitfield of class READ_* constants or GAID_FOR_UPDATE
         * @return bool
         */
        public function isRedirect( $flags = 0 ) {
                if ( DBAccessObjectUtils::hasFlags( $flags, self::READ_LATEST ) ) {
                        $this->mRedirect = (bool)$this->loadFieldFromDB( 'page_is_redirect', $flags );
                } elseif ( $this->mRedirect === null ) {
                        if ( $this->getArticleID( $flags ) ) {
                                $linkCache = MediaWikiServices::getInstance()->getLinkCache();
                                $linkCache->addLinkObj( $this ); // in case we already had an article ID
                                // Note that LinkCache returns null if it thinks the page does not exist;
                                // always trust the state of LinkCache over that of this Title instance.
                                $this->mRedirect = (bool)$linkCache->getGoodLinkFieldObj( $this, 'redirect' );
                        } else {
                                $this->mRedirect = false;
                        }
                }

                return $this->mRedirect;
        }

        /**
         * What is the length of this page?
         * Uses link cache, adding it if necessary
         *
         * @param int $flags Either a bitfield of class READ_* constants or GAID_FOR_UPDATE
         * @return int
         */
        public function getLength( $flags = 0 ) {
                if ( DBAccessObjectUtils::hasFlags( $flags, self::READ_LATEST ) ) {
                        $this->mLength = (int)$this->loadFieldFromDB( 'page_len', $flags );
                } else {
                        if ( $this->mLength != -1 ) {
                                return $this->mLength;
                        } elseif ( !$this->getArticleID( $flags ) ) {
                                $this->mLength = 0;
                                return $this->mLength;
                        }

                        $linkCache = MediaWikiServices::getInstance()->getLinkCache();
                        $linkCache->addLinkObj( $this ); // in case we already had an article ID
                        // Note that LinkCache returns null if it thinks the page does not exist;
                        // always trust the state of LinkCache over that of this Title instance.
                        $this->mLength = (int)$linkCache->getGoodLinkFieldObj( $this, 'length' );
                }

                return $this->mLength;
        }

        /**
         * What is the page_latest field for this page?
         *
         * @param int $flags Either a bitfield of class READ_* constants or GAID_FOR_UPDATE
         * @return int Int or 0 if the page doesn't exist
         */
        public function getLatestRevID( $flags = 0 ) {
                if ( DBAccessObjectUtils::hasFlags( $flags, self::READ_LATEST ) ) {
                        $this->mLatestID = (int)$this->loadFieldFromDB( 'page_latest', $flags );
                } else {
                        if ( $this->mLatestID !== false ) {
                                return (int)$this->mLatestID;
                        } elseif ( !$this->getArticleID( $flags ) ) {
                                $this->mLatestID = 0;

                                return $this->mLatestID;
                        }

                        $linkCache = MediaWikiServices::getInstance()->getLinkCache();
                        $linkCache->addLinkObj( $this ); // in case we already had an article ID
                        // Note that LinkCache returns null if it thinks the page does not exist;
                        // always trust the state of LinkCache over that of this Title instance.
                        $this->mLatestID = (int)$linkCache->getGoodLinkFieldObj( $this, 'revision' );
                }

                return $this->mLatestID;
        }

        /**
         * Inject a page ID, reset DB-loaded fields, and clear the link cache for this title
         *
         * This can be called on page insertion to allow loading of the new page_id without
         * having to create a new Title instance. Likewise with deletion.
         *
         * This is also used during page moves, to reflect the change in the relationship
         * between article ID and title text.
         *
         * @note This overrides Title::setContentModel()
         *
         * @param int|bool $id Page ID, 0 for non-existant, or false for "unknown" (lazy-load)
         */
        public function resetArticleID( $id ) {
                if ( $id === false ) {
                        $this->mArticleID = -1;
                } else {
                        $this->mArticleID = (int)$id;
                }
                $this->mRestrictionsLoaded = false;
                $this->mRestrictions = [];
                $this->mOldRestrictions = false;
                $this->mRedirect = null;
                $this->mLength = -1;
                $this->mLatestID = false;
                $this->mContentModel = false;
                $this->mForcedContentModel = false;
                $this->mEstimateRevisions = null;
                $this->mPageLanguage = null;
                $this->mDbPageLanguage = false;
                $this->mIsBigDeletion = null;

                MediaWikiServices::getInstance()->getLinkCache()->clearLink( $this );
        }

        public static function clearCaches() {
                $linkCache = MediaWikiServices::getInstance()->getLinkCache();
                $linkCache->clear();

                $titleCache = self::getTitleCache();
                $titleCache->clear();
        }

        /**
         * Capitalize a text string for a title if it belongs to a namespace that capitalizes
         *
         * @param string $text Containing title to capitalize
         * @param int $ns Namespace index, defaults to NS_MAIN
         * @return string Containing capitalized title
         */
        public static function capitalize( $text, $ns = NS_MAIN ) {
                $services = MediaWikiServices::getInstance();
                if ( $services->getNamespaceInfo()->isCapitalized( $ns ) ) {
                        return $services->getContentLanguage()->ucfirst( $text );
                } else {
                        return $text;
                }
        }

        /**
         * Secure and split - main initialisation function for this object
         *
         * Assumes that $text is urldecoded
         * and uses underscores, but not otherwise munged.  This function
         * removes illegal characters, splits off the interwiki and
         * namespace prefixes, sets the other forms, and canonicalizes
         * everything.
         *
         * If this method returns normally, the Title is valid.
         *
         * @param string $text
         * @param int|null $defaultNamespace
         *
         * @throws MalformedTitleException On malformed titles
         */
        private function secureAndSplit( $text, $defaultNamespace = null ) {
                if ( $defaultNamespace === null ) {
                        $defaultNamespace = $this->mDefaultNamespace;
                }

                // @note: splitTitleString() is a temporary hack to allow MediaWikiTitleCodec to share
                //        the parsing code with Title, while avoiding massive refactoring.
                // @todo: get rid of secureAndSplit, refactor parsing code.
                // @note: getTitleParser() returns a TitleParser implementation which does not have a
                //        splitTitleString method, but the only implementation (MediaWikiTitleCodec) does
                /** @var MediaWikiTitleCodec $titleCodec */
                $titleCodec = MediaWikiServices::getInstance()->getTitleParser();
                '@phan-var MediaWikiTitleCodec $titleCodec';
                // MalformedTitleException can be thrown here
                $parts = $titleCodec->splitTitleString( $text, $defaultNamespace );

                # Fill fields
                $this->setFragment( '#' . $parts['fragment'] );
                $this->mInterwiki = $parts['interwiki'];
                $this->mLocalInterwiki = $parts['local_interwiki'];
                $this->mNamespace = $parts['namespace'];
                $this->mDefaultNamespace = $defaultNamespace;

                $this->mDbkeyform = $parts['dbkey'];
                $this->mUrlform = wfUrlencode( $this->mDbkeyform );
                $this->mTextform = strtr( $this->mDbkeyform, '_', ' ' );

                // splitTitleString() guarantees that this title is valid.
                $this->mIsValid = true;

                # We already know that some pages won't be in the database!
                if ( $this->isExternal() || $this->isSpecialPage() || $this->mTextform === '' ) {
                        $this->mArticleID = 0;
                }
        }

        /**
         * Get an array of Title objects linking to this Title
         * Also stores the IDs in the link cache.
         *
         * WARNING: do not use this function on arbitrary user-supplied titles!
         * On heavily-used templates it will max out the memory.
         *
         * @param array $options May be FOR UPDATE
         * @param string $table Table name
         * @param string $prefix Fields prefix
         * @return Title[] Array of Title objects linking here
         */
        public function getLinksTo( $options = [], $table = 'pagelinks', $prefix = 'pl' ) {
                if ( count( $options ) > 0 ) {
                        $db = wfGetDB( DB_MASTER );
                } else {
                        $db = wfGetDB( DB_REPLICA );
                }

                $res = $db->select(
                        [ 'page', $table ],
                        self::getSelectFields(),
                        [
                                "{$prefix}_from=page_id",
                                "{$prefix}_namespace" => $this->mNamespace,
                                "{$prefix}_title" => $this->mDbkeyform ],
                        __METHOD__,
                        $options
                );

                $retVal = [];
                if ( $res->numRows() ) {
                        $linkCache = MediaWikiServices::getInstance()->getLinkCache();
                        foreach ( $res as $row ) {
                                $titleObj = self::makeTitle( $row->page_namespace, $row->page_title );
                                if ( $titleObj ) {
                                        $linkCache->addGoodLinkObjFromRow( $titleObj, $row );
                                        $retVal[] = $titleObj;
                                }
                        }
                }
                return $retVal;
        }

        /**
         * Get an array of Title objects using this Title as a template
         * Also stores the IDs in the link cache.
         *
         * WARNING: do not use this function on arbitrary user-supplied titles!
         * On heavily-used templates it will max out the memory.
         *
         * @param array $options Query option to Database::select()
         * @return Title[] Array of Title the Title objects linking here
         */
        public function getTemplateLinksTo( $options = [] ) {
                return $this->getLinksTo( $options, 'templatelinks', 'tl' );
        }

        /**
         * Get an array of Title objects linked from this Title
         * Also stores the IDs in the link cache.
         *
         * WARNING: do not use this function on arbitrary user-supplied titles!
         * On heavily-used templates it will max out the memory.
         *
         * @param array $options Query option to Database::select()
         * @param string $table Table name
         * @param string $prefix Fields prefix
         * @return Title[] List of Titles linking here
         */
        public function getLinksFrom( $options = [], $table = 'pagelinks', $prefix = 'pl' ) {
                $id = $this->getArticleID();

                # If the page doesn't exist; there can't be any link from this page
                if ( !$id ) {
                        return [];
                }

                $db = wfGetDB( DB_REPLICA );

                $blNamespace = "{$prefix}_namespace";
                $blTitle = "{$prefix}_title";

                $pageQuery = WikiPage::getQueryInfo();
                $res = $db->select(
                        [ $table, 'nestpage' => $pageQuery['tables'] ],
                        array_merge(
                                [ $blNamespace, $blTitle ],
                                $pageQuery['fields']
                        ),
                        [ "{$prefix}_from" => $id ],
                        __METHOD__,
                        $options,
                        [ 'nestpage' => [
                                'LEFT JOIN',
                                [ "page_namespace=$blNamespace", "page_title=$blTitle" ]
                        ] ] + $pageQuery['joins']
                );

                $retVal = [];
                $linkCache = MediaWikiServices::getInstance()->getLinkCache();
                foreach ( $res as $row ) {
                        if ( $row->page_id ) {
                                $titleObj = self::newFromRow( $row );
                        } else {
                                $titleObj = self::makeTitle( $row->$blNamespace, $row->$blTitle );
                                $linkCache->addBadLinkObj( $titleObj );
                        }
                        $retVal[] = $titleObj;
                }

                return $retVal;
        }

        /**
         * Get an array of Title objects used on this Title as a template
         * Also stores the IDs in the link cache.
         *
         * WARNING: do not use this function on arbitrary user-supplied titles!
         * On heavily-used templates it will max out the memory.
         *
         * @param array $options May be FOR UPDATE
         * @return Title[] Array of Title the Title objects used here
         */
        public function getTemplateLinksFrom( $options = [] ) {
                return $this->getLinksFrom( $options, 'templatelinks', 'tl' );
        }

        /**
         * Get an array of Title objects referring to non-existent articles linked
         * from this page.
         *
         * @todo check if needed (used only in SpecialBrokenRedirects.php, and
         *   should use redirect table in this case).
         * @return Title[] Array of Title the Title objects
         */
        public function getBrokenLinksFrom() {
                if ( $this->getArticleID() == 0 ) {
                        # All links from article ID 0 are false positives
                        return [];
                }

                $dbr = wfGetDB( DB_REPLICA );
                $res = $dbr->select(
                        [ 'page', 'pagelinks' ],
                        [ 'pl_namespace', 'pl_title' ],
                        [
                                'pl_from' => $this->getArticleID(),
                                'page_namespace IS NULL'
                        ],
                        __METHOD__, [],
                        [
                                'page' => [
                                        'LEFT JOIN',
                                        [ 'pl_namespace=page_namespace', 'pl_title=page_title' ]
                                ]
                        ]
                );

                $retVal = [];
                foreach ( $res as $row ) {
                        $retVal[] = self::makeTitle( $row->pl_namespace, $row->pl_title );
                }
                return $retVal;
        }

        /**
         * Get a list of URLs to purge from the CDN cache when this page changes.
         *
         * @deprecated 1.35 Use HtmlCacheUpdater
         * @return string[] Array of String the URLs
         */
        public function getCdnUrls() {
                $htmlCache = MediaWikiServices::getInstance()->getHtmlCacheUpdater();
                return $htmlCache->getUrls( $this );
        }

        /**
         * Purge all applicable CDN URLs
         * @deprecated 1.35 Use HtmlCacheUpdater
         */
        public function purgeSquid() {
                $htmlCache = MediaWikiServices::getInstance()->getHtmlCacheUpdater();
                $htmlCache->purgeTitleUrls( $this, $htmlCache::PURGE_INTENT_TXROUND_REFLECTED );
        }

        /**
         * Locks the page row and check if this page is single revision redirect
         *
         * This updates the cached fields of this instance via Title::loadFromRow()
         *
         * @return bool
         */
        public function isSingleRevRedirect() {
                $dbw = wfGetDB( DB_MASTER );
                $dbw->startAtomic( __METHOD__ );

                $row = $dbw->selectRow(
                        'page',
                        self::getSelectFields(),
                        $this->pageCond(),
                        __METHOD__,
                        [ 'FOR UPDATE' ]
                );
                // Update the cached fields
                $this->loadFromRow( $row );

                if ( $this->mRedirect && $this->mLatestID ) {
                        $isSingleRevRedirect = !$dbw->selectField(
                                'revision',
                                '1',
                                [ 'rev_page' => $this->mArticleID,  'rev_id != ' . (int)$this->mLatestID ],
                                __METHOD__,
                                [ 'FOR UPDATE' ]
                        );
                } else {
                        $isSingleRevRedirect = false;
                }

                $dbw->endAtomic( __METHOD__ );

                return $isSingleRevRedirect;
        }

        /**
         * Get categories to which this Title belongs and return an array of
         * categories' names.
         *
         * @return string[] Array of parents in the form:
         *     $parent => $currentarticle
         */
        public function getParentCategories() {
                $data = [];

                $titleKey = $this->getArticleID();

                if ( $titleKey === 0 ) {
                        return $data;
                }

                $dbr = wfGetDB( DB_REPLICA );

                $res = $dbr->select(
                        'categorylinks',
                        'cl_to',
                        [ 'cl_from' => $titleKey ],
                        __METHOD__
                );

                if ( $res->numRows() > 0 ) {
                        $contLang = MediaWikiServices::getInstance()->getContentLanguage();
                        foreach ( $res as $row ) {
                                // $data[] = Title::newFromText( $contLang->getNsText ( NS_CATEGORY ).':'.$row->cl_to);
                                $data[$contLang->getNsText( NS_CATEGORY ) . ':' . $row->cl_to] =
                                        $this->getFullText();
                        }
                }
                return $data;
        }

        /**
         * Get a tree of parent categories
         *
         * @param array $children Array with the children in the keys, to check for circular refs
         * @return array Tree of parent categories
         */
        public function getParentCategoryTree( $children = [] ) {
                $stack = [];
                $parents = $this->getParentCategories();

                if ( $parents ) {
                        foreach ( $parents as $parent => $current ) {
                                if ( array_key_exists( $parent, $children ) ) {
                                        # Circular reference
                                        $stack[$parent] = [];
                                } else {
                                        $nt = self::newFromText( $parent );
                                        if ( $nt ) {
                                                $stack[$parent] = $nt->getParentCategoryTree( $children + [ $parent => 1 ] );
                                        }
                                }
                        }
                }

                return $stack;
        }

        /**
         * Get an associative array for selecting this title from
         * the "page" table
         *
         * @return array Array suitable for the $where parameter of DB::select()
         */
        public function pageCond() {
                if ( $this->mArticleID > 0 ) {
                        // PK avoids secondary lookups in InnoDB, shouldn't hurt other DBs
                        return [ 'page_id' => $this->mArticleID ];
                } else {
                        return [ 'page_namespace' => $this->mNamespace, 'page_title' => $this->mDbkeyform ];
                }
        }

        /**
         * Get next/previous revision ID relative to another revision ID
         * @param int $revId Revision ID. Get the revision that was before this one.
         * @param int $flags Bitfield of class READ_* constants
         * @param string $dir 'next' or 'prev'
         * @return int|bool New revision ID, or false if none exists
         */
        private function getRelativeRevisionID( $revId, $flags, $dir ) {
                $rl = MediaWikiServices::getInstance()->getRevisionLookup();
                $rev = $rl->getRevisionById( $revId, $flags );
                if ( !$rev ) {
                        return false;
                }

                $oldRev = ( $dir === 'next' )
                        ? $rl->getNextRevision( $rev, $flags )
                        : $rl->getPreviousRevision( $rev, $flags );

                return $oldRev ? $oldRev->getId() : false;
        }

        /**
         * Get the revision ID of the previous revision
         *
         * @deprecated since 1.34, use RevisionLookup::getPreviousRevision
         * @param int $revId Revision ID. Get the revision that was before this one.
         * @param int $flags Bitfield of class READ_* constants
         * @return int|bool Old revision ID, or false if none exists
         */
        public function getPreviousRevisionID( $revId, $flags = 0 ) {
                return $this->getRelativeRevisionID( $revId, $flags, 'prev' );
        }

        /**
         * Get the revision ID of the next revision
         *
         * @deprecated since 1.34, use RevisionLookup::getNextRevision
         * @param int $revId Revision ID. Get the revision that was after this one.
         * @param int $flags Bitfield of class READ_* constants
         * @return int|bool Next revision ID, or false if none exists
         */
        public function getNextRevisionID( $revId, $flags = 0 ) {
                return $this->getRelativeRevisionID( $revId, $flags, 'next' );
        }

        /**
         * Get the first revision of the page
         *
         * @deprecated since 1.35. Use RevisionLookup::getFirstRevision instead.
         * @param int $flags Bitfield of class READ_* constants
         * @return Revision|null If page doesn't exist
         */
        public function getFirstRevision( $flags = 0 ) {
                wfDeprecated( __METHOD__, '1.35' );
                $flags |= ( $flags & self::GAID_FOR_UPDATE ) ? self::READ_LATEST : 0; // b/c
                $rev = MediaWikiServices::getInstance()
                        ->getRevisionLookup()
                        ->getFirstRevision( $this, $flags );
                return $rev ? new Revision( $rev ) : null;
        }

        /**
         * Get the oldest revision timestamp of this page
         *
         * @deprecated since 1.35. Use RevisionLookup::getFirstRevision instead.
         * @param int $flags Bitfield of class READ_* constants
         * @return string|null MW timestamp
         */
        public function getEarliestRevTime( $flags = 0 ) {
                $rev = MediaWikiServices::getInstance()
                        ->getRevisionLookup()
                        ->getFirstRevision( $this, $flags );
                return $rev ? $rev->getTimestamp() : null;
        }

        /**
         * Check if this is a new page
         *
         * @return bool
         */
        public function isNewPage() {
                $dbr = wfGetDB( DB_REPLICA );
                return (bool)$dbr->selectField( 'page', 'page_is_new', $this->pageCond(), __METHOD__ );
        }

        /**
         * Check whether the number of revisions of this page surpasses $wgDeleteRevisionsLimit
         *
         * @return bool
         */
        public function isBigDeletion() {
                global $wgDeleteRevisionsLimit;

                if ( !$wgDeleteRevisionsLimit ) {
                        return false;
                }

                if ( $this->mIsBigDeletion === null ) {
                        $dbr = wfGetDB( DB_REPLICA );

                        $revCount = $dbr->selectRowCount(
                                'revision',
                                '1',
                                [ 'rev_page' => $this->getArticleID() ],
                                __METHOD__,
                                [ 'LIMIT' => $wgDeleteRevisionsLimit + 1 ]
                        );

                        $this->mIsBigDeletion = $revCount > $wgDeleteRevisionsLimit;
                }

                return $this->mIsBigDeletion;
        }

        /**
         * Get the approximate revision count of this page.
         *
         * @return int
         */
        public function estimateRevisionCount() {
                if ( !$this->exists() ) {
                        return 0;
                }

                if ( $this->mEstimateRevisions === null ) {
                        $dbr = wfGetDB( DB_REPLICA );
                        $this->mEstimateRevisions = $dbr->estimateRowCount( 'revision', '*',
                                [ 'rev_page' => $this->getArticleID() ], __METHOD__ );
                }

                return $this->mEstimateRevisions;
        }

        /**
         * Get the number of revisions between the given revision.
         * Used for diffs and other things that really need it.
         *
         * @deprecated since 1.35 Use RevisionStore::countRevisionsBetween instead.
         *
         * @param int|Revision $old Old revision or rev ID (first before range)
         * @param int|Revision $new New revision or rev ID (first after range)
         * @param int|null $max Limit of Revisions to count, will be incremented to detect truncations
         * @return int Number of revisions between these revisions.
         */
        public function countRevisionsBetween( $old, $new, $max = null ) {
                wfDeprecated( __METHOD__, '1.35' );
                if ( !( $old instanceof Revision ) ) {
                        $old = Revision::newFromTitle( $this, (int)$old );
                }
                if ( !( $new instanceof Revision ) ) {
                        $new = Revision::newFromTitle( $this, (int)$new );
                }
                if ( !$old || !$new ) {
                        return 0; // nothing to compare
                }
                return MediaWikiServices::getInstance()
                        ->getRevisionStore()
                        ->countRevisionsBetween(
                                $this->getArticleID(),
                                $old->getRevisionRecord(),
                                $new->getRevisionRecord(),
                                $max
                        );
        }

        /**
         * Get the authors between the given revisions or revision IDs.
         * Used for diffs and other things that really need it.
         *
         * @since 1.23
         * @deprecated since 1.35 Use RevisionStore::getAuthorsBetween instead.
         *
         * @param int|Revision $old Old revision or rev ID (first before range by default)
         * @param int|Revision $new New revision or rev ID (first after range by default)
         * @param int $limit Maximum number of authors
         * @param string|array $options (Optional): Single option, or an array of options:
         *     'include_old' Include $old in the range; $new is excluded.
         *     'include_new' Include $new in the range; $old is excluded.
         *     'include_both' Include both $old and $new in the range.
         *     Unknown option values are ignored.
         * @return array|null Names of revision authors in the range; null if not both revisions exist
         */
        public function getAuthorsBetween( $old, $new, $limit, $options = [] ) {
                wfDeprecated( __METHOD__, '1.35' );
                if ( !( $old instanceof Revision ) ) {
                        $old = Revision::newFromTitle( $this, (int)$old );
                }
                if ( !( $new instanceof Revision ) ) {
                        $new = Revision::newFromTitle( $this, (int)$new );
                }
                try {
                        $users = MediaWikiServices::getInstance()
                                ->getRevisionStore()
                                ->getAuthorsBetween(
                                        $this->getArticleID(),
                                        $old->getRevisionRecord(),
                                        $new->getRevisionRecord(),
                                        null,
                                        $limit,
                                        $options
                                );
                        return array_map( function ( UserIdentity $user ) {
                                return $user->getName();
                        }, $users );
                } catch ( InvalidArgumentException $e ) {
                        return null; // b/c
                }
        }

        /**
         * Get the number of authors between the given revisions or revision IDs.
         * Used for diffs and other things that really need it.
         *
         * @deprecated since 1.35 Use RevisionStore::countAuthorsBetween instead.
         *
         * @param int|Revision $old Old revision or rev ID (first before range by default)
         * @param int|Revision $new New revision or rev ID (first after range by default)
         * @param int $limit Maximum number of authors
         * @param string|array $options (Optional): Single option, or an array of options:
         *     'include_old' Include $old in the range; $new is excluded.
         *     'include_new' Include $new in the range; $old is excluded.
         *     'include_both' Include both $old and $new in the range.
         *     Unknown option values are ignored.
         * @return int Number of revision authors in the range; zero if not both revisions exist
         */
        public function countAuthorsBetween( $old, $new, $limit, $options = [] ) {
                wfDeprecated( __METHOD__, '1.35' );
                $authors = $this->getAuthorsBetween( $old, $new, $limit, $options );
                return $authors ? count( $authors ) : 0;
        }

        /**
         * Compare with another title.
         *
         * @param LinkTarget $title
         * @return bool
         */
        public function equals( LinkTarget $title ) {
                // Note: === is necessary for proper matching of number-like titles.
                return $this->mInterwiki === $title->getInterwiki()
                        && $this->mNamespace == $title->getNamespace()
                        && $this->mDbkeyform === $title->getDBkey();
        }

        /**
         * Check if this title is a subpage of another title
         *
         * @param Title $title
         * @return bool
         */
        public function isSubpageOf( Title $title ) {
                return $this->mInterwiki === $title->mInterwiki
                        && $this->mNamespace == $title->mNamespace
                        && strpos( $this->mDbkeyform, $title->mDbkeyform . '/' ) === 0;
        }

        /**
         * Check if page exists.  For historical reasons, this function simply
         * checks for the existence of the title in the page table, and will
         * thus return false for interwiki links, special pages and the like.
         * If you want to know if a title can be meaningfully viewed, you should
         * probably call the isKnown() method instead.
         *
         * @param int $flags Either a bitfield of class READ_* constants or GAID_FOR_UPDATE
         * @return bool
         */
        public function exists( $flags = 0 ) {
                $exists = $this->getArticleID( $flags ) != 0;
                Hooks::runner()->onTitleExists( $this, $exists );
                return $exists;
        }

        /**
         * Should links to this title be shown as potentially viewable (i.e. as
         * "bluelinks"), even if there's no record by this title in the page
         * table?
         *
         * This function is semi-deprecated for public use, as well as somewhat
         * misleadingly named.  You probably just want to call isKnown(), which
         * calls this function internally.
         *
         * (ISSUE: Most of these checks are cheap, but the file existence check
         * can potentially be quite expensive.  Including it here fixes a lot of
         * existing code, but we might want to add an optional parameter to skip
         * it and any other expensive checks.)
         *
         * @return bool
         */
        public function isAlwaysKnown() {
                $isKnown = null;

                /**
                 * Allows overriding default behavior for determining if a page exists.
                 * If $isKnown is kept as null, regular checks happen. If it's
                 * a boolean, this value is returned by the isKnown method.
                 *
                 * @since 1.20
                 *
                 * @param Title $title
                 * @param bool|null $isKnown
                 */
                Hooks::runner()->onTitleIsAlwaysKnown( $this, $isKnown );

                if ( $isKnown !== null ) {
                        return $isKnown;
                }

                if ( $this->isExternal() ) {
                        return true; // any interwiki link might be viewable, for all we know
                }

                $services = MediaWikiServices::getInstance();
                switch ( $this->mNamespace ) {
                        case NS_MEDIA:
                        case NS_FILE:
                                // file exists, possibly in a foreign repo
                                return (bool)$services->getRepoGroup()->findFile( $this );
                        case NS_SPECIAL:
                                // valid special page
                                return $services->getSpecialPageFactory()->exists( $this->mDbkeyform );
                        case NS_MAIN:
                                // selflink, possibly with fragment
                                return $this->mDbkeyform == '';
                        case NS_MEDIAWIKI:
                                // known system message
                                return $this->hasSourceText() !== false;
                        default:
                                return false;
                }
        }

        /**
         * Does this title refer to a page that can (or might) be meaningfully
         * viewed?  In particular, this function may be used to determine if
         * links to the title should be rendered as "bluelinks" (as opposed to
         * "redlinks" to non-existent pages).
         * Adding something else to this function will cause inconsistency
         * since LinkHolderArray calls isAlwaysKnown() and does its own
         * page existence check.
         *
         * @return bool
         */
        public function isKnown() {
                return $this->isAlwaysKnown() || $this->exists();
        }

        /**
         * Does this page have source text?
         *
         * @return bool
         */
        public function hasSourceText() {
                if ( $this->exists() ) {
                        return true;
                }

                if ( $this->mNamespace === NS_MEDIAWIKI ) {
                        $services = MediaWikiServices::getInstance();
                        // If the page doesn't exist but is a known system message, default
                        // message content will be displayed, same for language subpages-
                        // Use always content language to avoid loading hundreds of languages
                        // to get the link color.
                        $contLang = $services->getContentLanguage();
                        list( $name, ) = $services->getMessageCache()->figureMessage(
                                $contLang->lcfirst( $this->getText() )
                        );
                        $message = wfMessage( $name )->inLanguage( $contLang )->useDatabase( false );
                        return $message->exists();
                }

                return false;
        }

        /**
         * Get the default (plain) message contents for an page that overrides an
         * interface message key.
         *
         * Primary use cases:
         *
         * - Article:
         *    - Show default when viewing the page. The Article::getSubstituteContent
         *      method displays the default message content, instead of the
         *      'noarticletext' placeholder message normally used.
         *
         * - EditPage:
         *    - Title of edit page. When creating an interface message override,
         *      the editor is told they are "Editing the page", instead of
         *      "Creating the page". (EditPage::setHeaders)
         *    - Edit notice. The 'translateinterface' edit notice is shown when creating
         *      or editing an interface message override. (EditPage::showIntro)
         *    - Opening the editor. The contents of the localisation message are used
         *      as contents of the editor when creating a new page in the MediaWiki
         *      namespace. This simplifies the process for editors when "changing"
         *      an interface message by creating an override. (EditPage::getContentObject)
         *    - Showing a diff. The left-hand side of a diff when an editor is
         *      previewing their changes before saving the creation of a page in the
         *      MediaWiki namespace. (EditPage::showDiff)
         *    - Disallowing a save. When attempting to create a MediaWiki-namespace
         *      page with the proposed content matching the interface message default,
         *      the save is rejected, the same way we disallow blank pages from being
         *      created. (EditPage::internalAttemptSave)
         *
         * - ApiEditPage:
         *    - Default content, when using the 'prepend' or 'append' feature.
         *
         * - SkinTemplate:
         *    - Label the create action as "Edit", if the page can be an override.
         *
         * @return string|bool
         */
        public function getDefaultMessageText() {
                if ( $this->mNamespace !== NS_MEDIAWIKI ) { // Just in case
                        return false;
                }

                list( $name, $lang ) = MediaWikiServices::getInstance()->getMessageCache()->figureMessage(
                        MediaWikiServices::getInstance()->getContentLanguage()->lcfirst( $this->getText() )
                );
                $message = wfMessage( $name )->inLanguage( $lang )->useDatabase( false );

                if ( $message->exists() ) {
                        return $message->plain();
                } else {
                        return false;
                }
        }

        /**
         * Updates page_touched for this page; called from LinksUpdate.php
         *
         * @param string|null $purgeTime [optional] TS_MW timestamp
         * @return bool True if the update succeeded
         */
        public function invalidateCache( $purgeTime = null ) {
                if ( wfReadOnly() ) {
                        return false;
                }
                if ( $this->mArticleID === 0 ) {
                        // avoid gap locking if we know it's not there
                        return true;
                }

                $conds = $this->pageCond();
                DeferredUpdates::addUpdate(
                        new AutoCommitUpdate(
                                wfGetDB( DB_MASTER ),
                                __METHOD__,
                                function ( IDatabase $dbw, $fname ) use ( $conds, $purgeTime ) {
                                        $dbTimestamp = $dbw->timestamp( $purgeTime ?: time() );
                                        $dbw->update(
                                                'page',
                                                [ 'page_touched' => $dbTimestamp ],
                                                $conds + [ 'page_touched < ' . $dbw->addQuotes( $dbTimestamp ) ],
                                                $fname
                                        );

                                        MediaWikiServices::getInstance()->getLinkCache()->invalidateTitle( $this );

                                        ResourceLoaderWikiModule::invalidateModuleCache(
                                                $this, null, null, $dbw->getDomainID() );
                                }
                        ),
                        DeferredUpdates::PRESEND
                );

                return true;
        }

        /**
         * Update page_touched timestamps and send CDN purge messages for
         * pages linking to this title. May be sent to the job queue depending
         * on the number of links. Typically called on create and delete.
         */
        public function touchLinks() {
                $jobs = [];
                $jobs[] = HTMLCacheUpdateJob::newForBacklinks(
                        $this,
                        'pagelinks',
                        [ 'causeAction' => 'page-touch' ]
                );
                if ( $this->mNamespace === NS_CATEGORY ) {
                        $jobs[] = HTMLCacheUpdateJob::newForBacklinks(
                                $this,
                                'categorylinks',
                                [ 'causeAction' => 'category-touch' ]
                        );
                }

                JobQueueGroup::singleton()->lazyPush( $jobs );
        }

        /**
         * Get the last touched timestamp
         *
         * @param IDatabase|null $db
         * @return string|false Last-touched timestamp
         */
        public function getTouched( $db = null ) {
                if ( $db === null ) {
                        $db = wfGetDB( DB_REPLICA );
                }
                $touched = $db->selectField( 'page', 'page_touched', $this->pageCond(), __METHOD__ );
                return $touched;
        }

        /**
         * Get the timestamp when this page was updated since the user last saw it.
         *
         * @deprecated since 1.35
         *
         * @param User $user
         * @return string|bool|null String timestamp, false if not watched, null if nothing is unseen
         */
        public function getNotificationTimestamp( User $user ) {
                return MediaWikiServices::getInstance()
                        ->getWatchlistNotificationManager()
                        ->getTitleNotificationTimestamp( $user, $this );
        }

        /**
         * Generate strings used for xml 'id' names in monobook tabs
         *
         * @param string $prepend Defaults to 'nstab-'
         * @return string XML 'id' name
         */
        public function getNamespaceKey( $prepend = 'nstab-' ) {
                // Gets the subject namespace of this title
                $nsInfo = MediaWikiServices::getInstance()->getNamespaceInfo();
                $subjectNS = $nsInfo->getSubject( $this->mNamespace );
                // Prefer canonical namespace name for HTML IDs
                $namespaceKey = $nsInfo->getCanonicalName( $subjectNS );
                if ( $namespaceKey === false ) {
                        // Fallback to localised text
                        $namespaceKey = $this->getSubjectNsText();
                }
                // Makes namespace key lowercase
                $namespaceKey = MediaWikiServices::getInstance()->getContentLanguage()->lc( $namespaceKey );
                // Uses main
                if ( $namespaceKey == '' ) {
                        $namespaceKey = 'main';
                }
                // Changes file to image for backwards compatibility
                if ( $namespaceKey == 'file' ) {
                        $namespaceKey = 'image';
                }
                return $prepend . $namespaceKey;
        }

        /**
         * Get all extant redirects to this Title
         *
         * @param int|null $ns Single namespace to consider; null to consider all namespaces
         * @return Title[] Array of Title redirects to this title
         */
        public function getRedirectsHere( $ns = null ) {
                $redirs = [];

                $dbr = wfGetDB( DB_REPLICA );
                $where = [
                        'rd_namespace' => $this->mNamespace,
                        'rd_title' => $this->mDbkeyform,
                        'rd_from = page_id'
                ];
                if ( $this->isExternal() ) {
                        $where['rd_interwiki'] = $this->mInterwiki;
                } else {
                        $where[] = 'rd_interwiki = ' . $dbr->addQuotes( '' ) . ' OR rd_interwiki IS NULL';
                }
                if ( $ns !== null ) {
                        $where['page_namespace'] = $ns;
                }

                $res = $dbr->select(
                        [ 'redirect', 'page' ],
                        [ 'page_namespace', 'page_title' ],
                        $where,
                        __METHOD__
                );

                foreach ( $res as $row ) {
                        $redirs[] = self::newFromRow( $row );
                }
                return $redirs;
        }

        /**
         * Check if this Title is a valid redirect target
         *
         * @return bool
         */
        public function isValidRedirectTarget() {
                global $wgInvalidRedirectTargets;

                if ( $this->isSpecialPage() ) {
                        // invalid redirect targets are stored in a global array, but explicitly disallow Userlogout here
                        if ( $this->isSpecial( 'Userlogout' ) ) {
                                return false;
                        }

                        foreach ( $wgInvalidRedirectTargets as $target ) {
                                if ( $this->isSpecial( $target ) ) {
                                        return false;
                                }
                        }
                }

                return true;
        }

        /**
         * Get a backlink cache object
         *
         * @return BacklinkCache
         */
        public function getBacklinkCache() {
                return BacklinkCache::get( $this );
        }

        /**
         * Whether the magic words __INDEX__ and __NOINDEX__ function for this page.
         *
         * @return bool
         */
        public function canUseNoindex() {
                global $wgExemptFromUserRobotsControl;

                $bannedNamespaces = $wgExemptFromUserRobotsControl ??
                        MediaWikiServices::getInstance()->getNamespaceInfo()->getContentNamespaces();

                return !in_array( $this->mNamespace, $bannedNamespaces );
        }

        /**
         * Returns the raw sort key to be used for categories, with the specified
         * prefix.  This will be fed to Collation::getSortKey() to get a
         * binary sortkey that can be used for actual sorting.
         *
         * @param string $prefix The prefix to be used, specified using
         *   {{defaultsort:}} or like [[Category:Foo|prefix]].  Empty for no
         *   prefix.
         * @return string
         */
        public function getCategorySortkey( $prefix = '' ) {
                $unprefixed = $this->getText();

                // Anything that uses this hook should only depend
                // on the Title object passed in, and should probably
                // tell the users to run updateCollations.php --force
                // in order to re-sort existing category relations.
                Hooks::runner()->onGetDefaultSortkey( $this, $unprefixed );
                if ( $prefix !== '' ) {
                        # Separate with a line feed, so the unprefixed part is only used as
                        # a tiebreaker when two pages have the exact same prefix.
                        # In UCA, tab is the only character that can sort above LF
                        # so we strip both of them from the original prefix.
                        $prefix = strtr( $prefix, "\n\t", '  ' );
                        return "$prefix\n$unprefixed";
                }
                return $unprefixed;
        }

        /**
         * Returns the page language code saved in the database, if $wgPageLanguageUseDB is set
         * to true in LocalSettings.php, otherwise returns false. If there is no language saved in
         * the db, it will return NULL.
         *
         * @return string|null|bool
         */
        private function getDbPageLanguageCode() {
                global $wgPageLanguageUseDB;

                // check, if the page language could be saved in the database, and if so and
                // the value is not requested already, lookup the page language using LinkCache
                if ( $wgPageLanguageUseDB && $this->mDbPageLanguage === false ) {
                        $linkCache = MediaWikiServices::getInstance()->getLinkCache();
                        $linkCache->addLinkObj( $this );
                        $this->mDbPageLanguage = $linkCache->getGoodLinkFieldObj( $this, 'lang' );
                }

                return $this->mDbPageLanguage;
        }

        /**
         * Get the language in which the content of this page is written in
         * wikitext. Defaults to content language, but in certain cases it can be
         * e.g. $wgLang (such as special pages, which are in the user language).
         *
         * @since 1.18
         * @return Language
         */
        public function getPageLanguage() {
                global $wgLang, $wgLanguageCode;
                if ( $this->isSpecialPage() ) {
                        // special pages are in the user language
                        return $wgLang;
                }

                // Checking if DB language is set
                $dbPageLanguage = $this->getDbPageLanguageCode();
                if ( $dbPageLanguage ) {
                        return wfGetLangObj( $dbPageLanguage );
                }

                if ( !$this->mPageLanguage || $this->mPageLanguage[1] !== $wgLanguageCode ) {
                        // Note that this may depend on user settings, so the cache should
                        // be only per-request.
                        // NOTE: ContentHandler::getPageLanguage() may need to load the
                        // content to determine the page language!
                        // Checking $wgLanguageCode hasn't changed for the benefit of unit
                        // tests.
                        $contentHandler = MediaWikiServices::getInstance()
                                ->getContentHandlerFactory()
                                ->getContentHandler( $this->getContentModel() );
                        $langObj = $contentHandler->getPageLanguage( $this );
                        $this->mPageLanguage = [ $langObj->getCode(), $wgLanguageCode ];
                } else {
                        $langObj = MediaWikiServices::getInstance()->getLanguageFactory()
                                ->getLanguage( $this->mPageLanguage[0] );
                }

                return $langObj;
        }

        /**
         * Get the language in which the content of this page is written when
         * viewed by user. Defaults to content language, but in certain cases it can be
         * e.g. $wgLang (such as special pages, which are in the user language).
         *
         * @since 1.20
         * @return Language
         */
        public function getPageViewLanguage() {
                global $wgLang;

                if ( $this->isSpecialPage() ) {
                        // If the user chooses a variant, the content is actually
                        // in a language whose code is the variant code.
                        $variant = $this->getLanguageConverter( $wgLang )->getPreferredVariant();
                        if ( $wgLang->getCode() !== $variant ) {
                                return MediaWikiServices::getInstance()->getLanguageFactory()
                                        ->getLanguage( $variant );
                        }

                        return $wgLang;
                }

                // Checking if DB language is set
                $dbPageLanguage = $this->getDbPageLanguageCode();
                if ( $dbPageLanguage ) {
                        $pageLang = wfGetLangObj( $dbPageLanguage );
                        $variant = $this->getLanguageConverter( $pageLang )->getPreferredVariant();
                        if ( $pageLang->getCode() !== $variant ) {
                                $pageLang = MediaWikiServices::getInstance()->getLanguageFactory()
                                        ->getLanguage( $variant );
                        }

                        return $pageLang;
                }

                // @note Can't be cached persistently, depends on user settings.
                // @note ContentHandler::getPageViewLanguage() may need to load the
                //   content to determine the page language!
                $contentHandler = MediaWikiServices::getInstance()
                        ->getContentHandlerFactory()
                        ->getContentHandler( $this->getContentModel() );
                $pageLang = $contentHandler->getPageViewLanguage( $this );
                return $pageLang;
        }

        /**
         * Get a list of rendered edit notices for this page.
         *
         * Array is keyed by the original message key, and values are rendered using parseAsBlock, so
         * they will already be wrapped in paragraphs.
         *
         * @since 1.21
         * @param int $oldid Revision ID that's being edited
         * @return array
         */
        public function getEditNotices( $oldid = 0 ) {
                $notices = [];

                // Optional notice for the entire namespace
                $editnotice_ns = 'editnotice-' . $this->mNamespace;
                $msg = wfMessage( $editnotice_ns );
                if ( $msg->exists() ) {
                        $html = $msg->parseAsBlock();
                        // Edit notices may have complex logic, but output nothing (T91715)
                        if ( trim( $html ) !== '' ) {
                                $notices[$editnotice_ns] = Html::rawElement(
                                        'div',
                                        [ 'class' => [
                                                'mw-editnotice',
                                                'mw-editnotice-namespace',
                                                Sanitizer::escapeClass( "mw-$editnotice_ns" )
                                        ] ],
                                        $html
                                );
                        }
                }

                if (
                        MediaWikiServices::getInstance()->getNamespaceInfo()->
                                hasSubpages( $this->mNamespace )
                ) {
                        // Optional notice for page itself and any parent page
                        $editnotice_base = $editnotice_ns;
                        foreach ( explode( '/', $this->mDbkeyform ) as $part ) {
                                $editnotice_base .= '-' . $part;
                                $msg = wfMessage( $editnotice_base );
                                if ( $msg->exists() ) {
                                        $html = $msg->parseAsBlock();
                                        if ( trim( $html ) !== '' ) {
                                                $notices[$editnotice_base] = Html::rawElement(
                                                        'div',
                                                        [ 'class' => [
                                                                'mw-editnotice',
                                                                'mw-editnotice-base',
                                                                Sanitizer::escapeClass( "mw-$editnotice_base" )
                                                        ] ],
                                                        $html
                                                );
                                        }
                                }
                        }
                } else {
                        // Even if there are no subpages in namespace, we still don't want "/" in MediaWiki message keys
                        $editnoticeText = $editnotice_ns . '-' . strtr( $this->mDbkeyform, '/', '-' );
                        $msg = wfMessage( $editnoticeText );
                        if ( $msg->exists() ) {
                                $html = $msg->parseAsBlock();
                                if ( trim( $html ) !== '' ) {
                                        $notices[$editnoticeText] = Html::rawElement(
                                                'div',
                                                [ 'class' => [
                                                        'mw-editnotice',
                                                        'mw-editnotice-page',
                                                        Sanitizer::escapeClass( "mw-$editnoticeText" )
                                                ] ],
                                                $html
                                        );
                                }
                        }
                }

                Hooks::runner()->onTitleGetEditNotices( $this, $oldid, $notices );
                return $notices;
        }

        /**
         * @param string $field
         * @param int $flags Bitfield of class READ_* constants
         * @return string|bool
         */
        private function loadFieldFromDB( $field, $flags ) {
                if ( !in_array( $field, self::getSelectFields(), true ) ) {
                        return false; // field does not exist
                }

                $flags |= ( $flags & self::GAID_FOR_UPDATE ) ? self::READ_LATEST : 0; // b/c
                list( $index, $options ) = DBAccessObjectUtils::getDBOptions( $flags );

                return wfGetDB( $index )->selectField(
                        'page',
                        $field,
                        $this->pageCond(),
                        __METHOD__,
                        $options
                );
        }

        /**
         * @return array
         */
        public function __sleep() {
                return [
                        'mNamespace',
                        'mDbkeyform',
                        'mFragment',
                        'mInterwiki',
                        'mLocalInterwiki',
                        'mDefaultNamespace',
                ];
        }

        public function __wakeup() {
                $this->mArticleID = ( $this->mNamespace >= 0 ) ? -1 : 0;
                $this->mUrlform = wfUrlencode( $this->mDbkeyform );
                $this->mTextform = strtr( $this->mDbkeyform, '_', ' ' );
        }

}