Title.php

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<?php
use Wikimedia\Rdbms\Database;
use Wikimedia\Rdbms\IDatabase;
use MediaWiki\Linker\LinkTarget;
use MediaWiki\Interwiki\InterwikiLookup;
use MediaWiki\MediaWikiServices;
 
class Title implements LinkTarget {
    static private $titleCache = null;
 
    const CACHE_MAX = 1000;
 
    const GAID_FOR_UPDATE = 1;
 
    // @{
 
    public $mTextform = '';
 
    public $mUrlform = '';
 
    public $mDbkeyform = '';
 
    protected $mUserCaseDBKey;
 
    public $mNamespace = NS_MAIN;
 
    public $mInterwiki = '';
 
    private $mLocalInterwiki = false;
 
    public $mFragment = '';
 
    public $mArticleID = -1;
 
    protected $mLatestID = false;
 
    private $mContentModel = false;
 
    private $mForcedContentModel = false;
 
    private $mEstimateRevisions;
 
    public $mRestrictions = [];
 
    protected $mOldRestrictions = false;
 
    public $mCascadeRestriction;
 
    public $mCascadingRestrictions;
 
    protected $mRestrictionsExpiry = [];
 
    protected $mHasCascadingRestrictions;
 
    public $mCascadeSources;
 
    public $mRestrictionsLoaded = false;
 
    protected $mPrefixedText = null;
 
    public $mTitleProtection;
 
    public $mDefaultNamespace = NS_MAIN;
 
    protected $mLength = -1;
 
    public $mRedirect = null;
 
    private $mNotificationTimestamp = [];
 
    private $mHasSubpages;
 
    private $mPageLanguage = false;
 
    private $mDbPageLanguage = false;
 
    private $mTitleValue = null;
 
    private $mIsBigDeletion = null;
    // @}
 
    private static function getTitleFormatter() {
        return MediaWikiServices::getInstance()->getTitleFormatter();
    }
 
    private static function getInterwikiLookup() {
        return MediaWikiServices::getInstance()->getInterwikiLookup();
    }
 
    function __construct() {
    }
 
    public static function newFromDBkey( $key ) {
        $t = new Title();
        $t->mDbkeyform = $key;
 
        try {
            $t->secureAndSplit();
            return $t;
        } catch ( MalformedTitleException $ex ) {
            return null;
        }
    }
 
    public static function newFromTitleValue( TitleValue $titleValue ) {
        return self::newFromLinkTarget( $titleValue );
    }
 
    public static function newFromLinkTarget( LinkTarget $linkTarget ) {
        if ( $linkTarget instanceof Title ) {
            // Special case if it's already a Title object
            return $linkTarget;
        }
        return self::makeTitle(
            $linkTarget->getNamespace(),
            $linkTarget->getText(),
            $linkTarget->getFragment(),
            $linkTarget->getInterwiki()
        );
    }
 
    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( strval( $text ), $defaultNamespace );
        } catch ( MalformedTitleException $ex ) {
            return null;
        }
    }
 
    public static function newFromTextThrow( $text, $defaultNamespace = NS_MAIN ) {
        if ( is_object( $text ) ) {
            throw new MWException( '$text must be a string, given an object' );
        }
 
        $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();
        $t->mDbkeyform = strtr( $filteredText, ' ', '_' );
        $t->mDefaultNamespace = intval( $defaultNamespace );
 
        $t->secureAndSplit();
        if ( $defaultNamespace == NS_MAIN ) {
            $titleCache->set( $text, $t );
        }
        return $t;
    }
 
    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, '+', ' ' );
        }
 
        $t->mDbkeyform = strtr( $url, ' ', '_' );
 
        try {
            $t->secureAndSplit();
            return $t;
        } catch ( MalformedTitleException $ex ) {
            return null;
        }
    }
 
    private static function getTitleCache() {
        if ( self::$titleCache == null ) {
            self::$titleCache = new HashBagOStuff( [ 'maxKeys' => self::CACHE_MAX ] );
        }
        return self::$titleCache;
    }
 
    protected static function getSelectFields() {
        global $wgContentHandlerUseDB, $wgPageLanguageUseDB;
 
        $fields = [
            'page_namespace', 'page_title', 'page_id',
            'page_len', 'page_is_redirect', 'page_latest',
        ];
 
        if ( $wgContentHandlerUseDB ) {
            $fields[] = 'page_content_model';
        }
 
        if ( $wgPageLanguageUseDB ) {
            $fields[] = 'page_lang';
        }
 
        return $fields;
    }
 
    public static function newFromID( $id, $flags = 0 ) {
        $db = ( $flags & self::GAID_FOR_UPDATE ) ? wfGetDB( DB_MASTER ) : wfGetDB( DB_REPLICA );
        $row = $db->selectRow(
            'page',
            self::getSelectFields(),
            [ 'page_id' => $id ],
            __METHOD__
        );
        if ( $row !== false ) {
            $title = self::newFromRow( $row );
        } else {
            $title = null;
        }
        return $title;
    }
 
    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;
    }
 
    public static function newFromRow( $row ) {
        $t = self::makeTitle( $row->page_namespace, $row->page_title );
        $t->loadFromRow( $row );
        return $t;
    }
 
    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 ( !$this->mForcedContentModel && isset( $row->page_content_model ) ) {
                $this->mContentModel = strval( $row->page_content_model );
            } elseif ( !$this->mForcedContentModel ) {
                $this->mContentModel = false; # initialized lazily in 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;
            $this->mLatestID = 0;
            if ( !$this->mForcedContentModel ) {
                $this->mContentModel = false; # initialized lazily in getContentModel()
            }
        }
    }
 
    public static function makeTitle( $ns, $title, $fragment = '', $interwiki = '' ) {
        $t = new Title();
        $t->mInterwiki = $interwiki;
        $t->mFragment = $fragment;
        $t->mNamespace = $ns = intval( $ns );
        $t->mDbkeyform = strtr( $title, ' ', '_' );
        $t->mArticleID = ( $ns >= 0 ) ? -1 : 0;
        $t->mUrlform = wfUrlencode( $t->mDbkeyform );
        $t->mTextform = strtr( $title, '_', ' ' );
        $t->mContentModel = false; # initialized lazily in getContentModel()
        return $t;
    }
 
    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 ( !MWNamespace::exists( $ns ) ) {
            return null;
        }
 
        $t = new Title();
        $t->mDbkeyform = self::makeName( $ns, $title, $fragment, $interwiki, true );
 
        try {
            $t->secureAndSplit();
            return $t;
        } catch ( MalformedTitleException $ex ) {
            return null;
        }
    }
 
    public static function newMainPage() {
        $title = self::newFromText( wfMessage( 'mainpage' )->inContentLanguage()->text() );
        // Don't give fatal errors if the message is broken
        if ( !$title ) {
            $title = self::newFromText( 'Main Page' );
        }
        return $title;
    }
 
    public static function nameOf( $id ) {
        $dbr = wfGetDB( DB_REPLICA );
 
        $s = $dbr->selectRow(
            'page',
            [ 'page_namespace', 'page_title' ],
            [ 'page_id' => $id ],
            __METHOD__
        );
        if ( $s === false ) {
            return null;
        }
 
        $n = self::makeName( $s->page_namespace, $s->page_title );
        return $n;
    }
 
    public static function legalChars() {
        global $wgLegalTitleChars;
        return $wgLegalTitleChars;
    }
 
    static function getTitleInvalidRegex() {
        wfDeprecated( __METHOD__, '1.25' );
        return MediaWikiTitleCodec::getTitleInvalidRegex();
    }
 
    public static function convertByteClassToUnicodeClass( $byteClass ) {
        $length = strlen( $byteClass );
        // Input token queue
        $x0 = $x1 = $x2 = '';
        // Decoded queue
        $d0 = $d1 = $d2 = '';
        // 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;
            $d2 = $d1;
            $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 += 1;
                }
            } 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;
            } 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;
            }
        }
        if ( $ord1 < 0x80 ) {
            $out .= $r1;
        }
        if ( $ord0 < 0x80 ) {
            $out .= $r0;
        }
        if ( $allowUnicode ) {
            $out .= '\u0080-\uFFFF';
        }
        return $out;
    }
 
    public static function makeName( $ns, $title, $fragment = '', $interwiki = '',
        $canonicalNamespace = false
    ) {
        global $wgContLang;
 
        if ( $canonicalNamespace ) {
            $namespace = MWNamespace::getCanonicalName( $ns );
        } else {
            $namespace = $wgContLang->getNsText( $ns );
        }
        $name = $namespace == '' ? $title : "$namespace:$title";
        if ( strval( $interwiki ) != '' ) {
            $name = "$interwiki:$name";
        }
        if ( strval( $fragment ) != '' ) {
            $name .= '#' . $fragment;
        }
        return $name;
    }
 
    static function escapeFragmentForURL( $fragment ) {
        # Note that we don't urlencode the fragment.  urlencoded Unicode
        # fragments appear not to work in IE (at least up to 7) or in at least
        # one version of Opera 9.x.  The W3C validator, for one, doesn't seem
        # to care if they aren't encoded.
        return Sanitizer::escapeId( $fragment, 'noninitial' );
    }
 
    public static function compare( LinkTarget $a, LinkTarget $b ) {
        if ( $a->getNamespace() == $b->getNamespace() ) {
            return strcmp( $a->getText(), $b->getText() );
        } else {
            return $a->getNamespace() - $b->getNamespace();
        }
    }
 
    public function isValid() {
        $ns = $this->getNamespace();
 
        if ( !MWNamespace::exists( $ns ) ) {
            return false;
        }
 
        try {
            $parser = MediaWikiServices::getInstance()->getTitleParser();
            $parser->parseTitle( $this->getDBkey(), $ns );
            return true;
        } catch ( MalformedTitleException $ex ) {
            return false;
        }
    }
 
    public function isLocal() {
        if ( $this->isExternal() ) {
            $iw = self::getInterwikiLookup()->fetch( $this->mInterwiki );
            if ( $iw ) {
                return $iw->isLocal();
            }
        }
        return true;
    }
 
    public function isExternal() {
        return $this->mInterwiki !== '';
    }
 
    public function getInterwiki() {
        return $this->mInterwiki;
    }
 
    public function wasLocalInterwiki() {
        return $this->mLocalInterwiki;
    }
 
    public function isTrans() {
        if ( !$this->isExternal() ) {
            return false;
        }
 
        return self::getInterwikiLookup()->fetch( $this->mInterwiki )->isTranscludable();
    }
 
    public function getTransWikiID() {
        if ( !$this->isExternal() ) {
            return false;
        }
 
        return self::getInterwikiLookup()->fetch( $this->mInterwiki )->getWikiID();
    }
 
    public function getTitleValue() {
        if ( $this->mTitleValue === null ) {
            try {
                $this->mTitleValue = new TitleValue(
                    $this->getNamespace(),
                    $this->getDBkey(),
                    $this->getFragment(),
                    $this->getInterwiki()
                );
            } catch ( InvalidArgumentException $ex ) {
                wfDebug( __METHOD__ . ': Can\'t create a TitleValue for [[' .
                    $this->getPrefixedText() . ']]: ' . $ex->getMessage() . "\n" );
            }
        }
 
        return $this->mTitleValue;
    }
 
    public function getText() {
        return $this->mTextform;
    }
 
    public function getPartialURL() {
        return $this->mUrlform;
    }
 
    public function getDBkey() {
        return $this->mDbkeyform;
    }
 
    function getUserCaseDBKey() {
        if ( !is_null( $this->mUserCaseDBKey ) ) {
            return $this->mUserCaseDBKey;
        } else {
            // If created via makeTitle(), $this->mUserCaseDBKey is not set.
            return $this->mDbkeyform;
        }
    }
 
    public function getNamespace() {
        return $this->mNamespace;
    }
 
    public function getContentModel( $flags = 0 ) {
        if ( !$this->mForcedContentModel
            && ( !$this->mContentModel || $flags === self::GAID_FOR_UPDATE )
            && $this->getArticleID( $flags )
        ) {
            $linkCache = LinkCache::singleton();
            $linkCache->addLinkObj( $this ); # in case we already had an article ID
            $this->mContentModel = $linkCache->getGoodLinkFieldObj( $this, 'model' );
        }
 
        if ( !$this->mContentModel ) {
            $this->mContentModel = ContentHandler::getDefaultModelFor( $this );
        }
 
        return $this->mContentModel;
    }
 
    public function hasContentModel( $id ) {
        return $this->getContentModel() == $id;
    }
 
    public function setContentModel( $model ) {
        $this->mContentModel = $model;
        $this->mForcedContentModel = true;
    }
 
    public function getNsText() {
        if ( $this->isExternal() ) {
            // This probably shouldn't even happen,
            // but for interwiki transclusion it sometimes does.
            // Use the canonical namespaces if possible to try to
            // resolve a foreign namespace.
            if ( MWNamespace::exists( $this->mNamespace ) ) {
                return MWNamespace::getCanonicalName( $this->mNamespace );
            }
        }
 
        try {
            $formatter = self::getTitleFormatter();
            return $formatter->getNamespaceName( $this->mNamespace, $this->mDbkeyform );
        } catch ( InvalidArgumentException $ex ) {
            wfDebug( __METHOD__ . ': ' . $ex->getMessage() . "\n" );
            return false;
        }
    }
 
    public function getSubjectNsText() {
        global $wgContLang;
        return $wgContLang->getNsText( MWNamespace::getSubject( $this->mNamespace ) );
    }
 
    public function getTalkNsText() {
        global $wgContLang;
        return $wgContLang->getNsText( MWNamespace::getTalk( $this->mNamespace ) );
    }
 
    public function canTalk() {
        return $this->canHaveTalkPage();
    }
 
    public function canHaveTalkPage() {
        return MWNamespace::hasTalkNamespace( $this->mNamespace );
    }
 
    public function canExist() {
        return $this->mNamespace >= NS_MAIN;
    }
 
    public function isWatchable() {
        return !$this->isExternal() && MWNamespace::isWatchable( $this->getNamespace() );
    }
 
    public function isSpecialPage() {
        return $this->getNamespace() == NS_SPECIAL;
    }
 
    public function isSpecial( $name ) {
        if ( $this->isSpecialPage() ) {
            list( $thisName, /* $subpage */ ) = SpecialPageFactory::resolveAlias( $this->getDBkey() );
            if ( $name == $thisName ) {
                return true;
            }
        }
        return false;
    }
 
    public function fixSpecialName() {
        if ( $this->isSpecialPage() ) {
            list( $canonicalName, $par ) = SpecialPageFactory::resolveAlias( $this->mDbkeyform );
            if ( $canonicalName ) {
                $localName = SpecialPageFactory::getLocalNameFor( $canonicalName, $par );
                if ( $localName != $this->mDbkeyform ) {
                    return self::makeTitle( NS_SPECIAL, $localName );
                }
            }
        }
        return $this;
    }
 
    public function inNamespace( $ns ) {
        return MWNamespace::equals( $this->getNamespace(), $ns );
    }
 
    public function inNamespaces( /* ... */ ) {
        $namespaces = func_get_args();
        if ( count( $namespaces ) > 0 && is_array( $namespaces[0] ) ) {
            $namespaces = $namespaces[0];
        }
 
        foreach ( $namespaces as $ns ) {
            if ( $this->inNamespace( $ns ) ) {
                return true;
            }
        }
 
        return false;
    }
 
    public function hasSubjectNamespace( $ns ) {
        return MWNamespace::subjectEquals( $this->getNamespace(), $ns );
    }
 
    public function isContentPage() {
        return MWNamespace::isContent( $this->getNamespace() );
    }
 
    public function isMovable() {
        if ( !MWNamespace::isMovable( $this->getNamespace() ) || $this->isExternal() ) {
            // Interwiki title or immovable namespace. Hooks don't get to override here
            return false;
        }
 
        $result = true;
        Hooks::run( 'TitleIsMovable', [ $this, &$result ] );
        return $result;
    }
 
    public function isMainPage() {
        return $this->equals( self::newMainPage() );
    }
 
    public function isSubpage() {
        return MWNamespace::hasSubpages( $this->mNamespace )
            ? strpos( $this->getText(), '/' ) !== false
            : false;
    }
 
    public function isConversionTable() {
        // @todo ConversionTable should become a separate content model.
 
        return $this->getNamespace() == NS_MEDIAWIKI &&
            strpos( $this->getText(), 'Conversiontable/' ) === 0;
    }
 
    public function isWikitextPage() {
        return $this->hasContentModel( CONTENT_MODEL_WIKITEXT );
    }
 
    public function isCssOrJsPage() {
        $isCssOrJsPage = NS_MEDIAWIKI == $this->mNamespace
            && ( $this->hasContentModel( CONTENT_MODEL_CSS )
                || $this->hasContentModel( CONTENT_MODEL_JAVASCRIPT ) );
 
        return $isCssOrJsPage;
    }
 
    public function isCssJsSubpage() {
        return ( NS_USER == $this->mNamespace && $this->isSubpage()
                && ( $this->hasContentModel( CONTENT_MODEL_CSS )
                    || $this->hasContentModel( CONTENT_MODEL_JAVASCRIPT ) ) );
    }
 
    public function getSkinFromCssJsSubpage() {
        $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' or '.js'
        }
        return substr( $subpage, 0, $lastdot );
    }
 
    public function isCssSubpage() {
        return ( NS_USER == $this->mNamespace && $this->isSubpage()
            && $this->hasContentModel( CONTENT_MODEL_CSS ) );
    }
 
    public function isJsSubpage() {
        return ( NS_USER == $this->mNamespace && $this->isSubpage()
            && $this->hasContentModel( CONTENT_MODEL_JAVASCRIPT ) );
    }
 
    public function isTalkPage() {
        return MWNamespace::isTalk( $this->getNamespace() );
    }
 
    public function getTalkPage() {
        return self::makeTitle( MWNamespace::getTalk( $this->getNamespace() ), $this->getDBkey() );
    }
 
    public function getTalkPageIfDefined() {
        if ( !$this->canHaveTalkPage() ) {
            return null;
        }
 
        return $this->getTalkPage();
    }
 
    public function getSubjectPage() {
        // Is this the same title?
        $subjectNS = MWNamespace::getSubject( $this->getNamespace() );
        if ( $this->getNamespace() == $subjectNS ) {
            return $this;
        }
        return self::makeTitle( $subjectNS, $this->getDBkey() );
    }
 
    public function getOtherPage() {
        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();
        }
    }
 
    public function getDefaultNamespace() {
        return $this->mDefaultNamespace;
    }
 
    public function getFragment() {
        return $this->mFragment;
    }
 
    public function hasFragment() {
        return $this->mFragment !== '';
    }
 
    public function getFragmentForURL() {
        if ( !$this->hasFragment() ) {
            return '';
        } elseif ( $this->isExternal() && !$this->getTransWikiID() ) {
            return '#' . Sanitizer::escapeIdForExternalInterwiki( $this->getFragment() );
        }
        return '#' . Sanitizer::escapeIdForLink( $this->getFragment() );
    }
 
    public function setFragment( $fragment ) {
        $this->mFragment = strtr( substr( $fragment, 1 ), '_', ' ' );
    }
 
    public function createFragmentTarget( $fragment ) {
        return self::makeTitle(
            $this->getNamespace(),
            $this->getText(),
            $fragment,
            $this->getInterwiki()
        );
    }
 
    private function prefix( $name ) {
        global $wgContLang;
 
        $p = '';
        if ( $this->isExternal() ) {
            $p = $this->mInterwiki . ':';
        }
 
        if ( 0 != $this->mNamespace ) {
            $nsText = $this->getNsText();
 
            if ( $nsText === false ) {
                // See T165149. Awkward, but better than erroneously linking to the main namespace.
                $nsText = $wgContLang->getNsText( NS_SPECIAL ) . ":Badtitle/NS{$this->mNamespace}";
            }
 
            $p .= $nsText . ':';
        }
        return $p . $name;
    }
 
    public function getPrefixedDBkey() {
        $s = $this->prefix( $this->mDbkeyform );
        $s = strtr( $s, ' ', '_' );
        return $s;
    }
 
    public function getPrefixedText() {
        if ( $this->mPrefixedText === null ) {
            $s = $this->prefix( $this->mTextform );
            $s = strtr( $s, '_', ' ' );
            $this->mPrefixedText = $s;
        }
        return $this->mPrefixedText;
    }
 
    public function __toString() {
        return $this->getPrefixedText();
    }
 
    public function getFullText() {
        $text = $this->getPrefixedText();
        if ( $this->hasFragment() ) {
            $text .= '#' . $this->getFragment();
        }
        return $text;
    }
 
    public function getRootText() {
        if ( !MWNamespace::hasSubpages( $this->mNamespace ) ) {
            return $this->getText();
        }
 
        return strtok( $this->getText(), '/' );
    }
 
    public function getRootTitle() {
        return self::makeTitle( $this->getNamespace(), $this->getRootText() );
    }
 
    public function getBaseText() {
        if ( !MWNamespace::hasSubpages( $this->mNamespace ) ) {
            return $this->getText();
        }
 
        $parts = explode( '/', $this->getText() );
        # Don't discard the real title if there's no subpage involved
        if ( count( $parts ) > 1 ) {
            unset( $parts[count( $parts ) - 1] );
        }
        return implode( '/', $parts );
    }
 
    public function getBaseTitle() {
        return self::makeTitle( $this->getNamespace(), $this->getBaseText() );
    }
 
    public function getSubpageText() {
        if ( !MWNamespace::hasSubpages( $this->mNamespace ) ) {
            return $this->mTextform;
        }
        $parts = explode( '/', $this->mTextform );
        return $parts[count( $parts ) - 1];
    }
 
    public function getSubpage( $text ) {
        return self::makeTitleSafe( $this->getNamespace(), $this->getText() . '/' . $text );
    }
 
    public function getSubpageUrlForm() {
        $text = $this->getSubpageText();
        $text = wfUrlencode( strtr( $text, ' ', '_' ) );
        return $text;
    }
 
    public function getPrefixedURL() {
        $s = $this->prefix( $this->mDbkeyform );
        $s = wfUrlencode( strtr( $s, ' ', '_' ) );
        return $s;
    }
 
    private static function fixUrlQueryArgs( $query, $query2 = false ) {
        if ( $query2 !== false ) {
            wfDeprecated( "Title::get{Canonical,Full,Link,Local,Internal}URL " .
                "method called with a second parameter is deprecated. 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;
    }
 
    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();
        // Avoid PHP 7.1 warning from passing $this by reference
        $titleRef = $this;
        Hooks::run( 'GetFullURL', [ &$titleRef, &$url, $query ] );
        return $url;
    }
 
    public function getFullUrlForRedirect( $query = '', $proto = PROTO_CURRENT ) {
        $target = $this;
        if ( $this->isExternal() ) {
            $target = SpecialPage::getTitleFor(
                'GoToInterwiki',
                $this->getPrefixedDBKey()
            );
        }
        return $target->getFullUrl( $query, false, $proto );
    }
 
    public function getLocalURL( $query = '', $query2 = false ) {
        global $wgArticlePath, $wgScript, $wgServer, $wgRequest;
 
        $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->getDBkey() );
            $url = wfAppendQuery( $url, $query );
        } else {
            $dbkey = wfUrlencode( $this->getPrefixedDBkey() );
            if ( $query == '' ) {
                $url = str_replace( '$1', $dbkey, $wgArticlePath );
                // Avoid PHP 7.1 warning from passing $this by reference
                $titleRef = $this;
                Hooks::run( 'GetLocalURL::Article', [ &$titleRef, &$url ] );
            } else {
                global $wgVariantArticlePath, $wgActionPaths, $wgContLang;
                $url = false;
                $matches = [];
 
                if ( !empty( $wgActionPaths )
                    && preg_match( '/^(.*&|)action=([^&]*)(&(.*)|)$/', $query, $matches )
                ) {
                    $action = urldecode( $matches[2] );
                    if ( isset( $wgActionPaths[$action] ) ) {
                        $query = $matches[1];
                        if ( isset( $matches[4] ) ) {
                            $query .= $matches[4];
                        }
                        $url = str_replace( '$1', $dbkey, $wgActionPaths[$action] );
                        if ( $query != '' ) {
                            $url = wfAppendQuery( $url, $query );
                        }
                    }
                }
 
                if ( $url === false
                    && $wgVariantArticlePath
                    && preg_match( '/^variant=([^&]*)$/', $query, $matches )
                    && $this->getPageLanguage()->equals( $wgContLang )
                    && $this->getPageLanguage()->hasVariants()
                ) {
                    $variant = urldecode( $matches[1] );
                    if ( $this->getPageLanguage()->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}";
                }
            }
            // Avoid PHP 7.1 warning from passing $this by reference
            $titleRef = $this;
            Hooks::run( 'GetLocalURL::Internal', [ &$titleRef, &$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;
            }
        }
        // Avoid PHP 7.1 warning from passing $this by reference
        $titleRef = $this;
        Hooks::run( 'GetLocalURL', [ &$titleRef, &$url, $query ] );
        return $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;
    }
 
    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 );
        // Avoid PHP 7.1 warning from passing $this by reference
        $titleRef = $this;
        Hooks::run( 'GetInternalURL', [ &$titleRef, &$url, $query ] );
        return $url;
    }
 
    public function getCanonicalURL( $query = '', $query2 = false ) {
        $query = self::fixUrlQueryArgs( $query, $query2 );
        $url = wfExpandUrl( $this->getLocalURL( $query ) . $this->getFragmentForURL(), PROTO_CANONICAL );
        // Avoid PHP 7.1 warning from passing $this by reference
        $titleRef = $this;
        Hooks::run( 'GetCanonicalURL', [ &$titleRef, &$url, $query ] );
        return $url;
    }
 
    public function getEditURL() {
        if ( $this->isExternal() ) {
            return '';
        }
        $s = $this->getLocalURL( 'action=edit' );
 
        return $s;
    }
 
    public function quickUserCan( $action, $user = null ) {
        return $this->userCan( $action, $user, false );
    }
 
    public function userCan( $action, $user = null, $rigor = 'secure' ) {
        if ( !$user instanceof User ) {
            global $wgUser;
            $user = $wgUser;
        }
 
        return !count( $this->getUserPermissionsErrorsInternal( $action, $user, $rigor, true ) );
    }
 
    public function getUserPermissionsErrors(
        $action, $user, $rigor = 'secure', $ignoreErrors = []
    ) {
        $errors = $this->getUserPermissionsErrorsInternal( $action, $user, $rigor );
 
        // Remove the errors being ignored.
        foreach ( $errors as $index => $error ) {
            $errKey = is_array( $error ) ? $error[0] : $error;
 
            if ( in_array( $errKey, $ignoreErrors ) ) {
                unset( $errors[$index] );
            }
            if ( $errKey instanceof MessageSpecifier && in_array( $errKey->getKey(), $ignoreErrors ) ) {
                unset( $errors[$index] );
            }
        }
 
        return $errors;
    }
 
    private function checkQuickPermissions( $action, $user, $errors, $rigor, $short ) {
        if ( !Hooks::run( 'TitleQuickPermissions',
            [ $this, $user, $action, &$errors, ( $rigor !== 'quick' ), $short ] )
        ) {
            return $errors;
        }
 
        if ( $action == 'create' ) {
            if (
                ( $this->isTalkPage() && !$user->isAllowed( 'createtalk' ) ) ||
                ( !$this->isTalkPage() && !$user->isAllowed( 'createpage' ) )
            ) {
                $errors[] = $user->isAnon() ? [ 'nocreatetext' ] : [ 'nocreate-loggedin' ];
            }
        } elseif ( $action == 'move' ) {
            if ( !$user->isAllowed( 'move-rootuserpages' )
                    && $this->mNamespace == NS_USER && !$this->isSubpage() ) {
                // Show user page-specific message only if the user can move other pages
                $errors[] = [ 'cant-move-user-page' ];
            }
 
            // Check if user is allowed to move files if it's a file
            if ( $this->mNamespace == NS_FILE && !$user->isAllowed( 'movefile' ) ) {
                $errors[] = [ 'movenotallowedfile' ];
            }
 
            // Check if user is allowed to move category pages if it's a category page
            if ( $this->mNamespace == NS_CATEGORY && !$user->isAllowed( 'move-categorypages' ) ) {
                $errors[] = [ 'cant-move-category-page' ];
            }
 
            if ( !$user->isAllowed( 'move' ) ) {
                // User can't move anything
                $userCanMove = User::groupHasPermission( 'user', 'move' );
                $autoconfirmedCanMove = User::groupHasPermission( 'autoconfirmed', 'move' );
                if ( $user->isAnon() && ( $userCanMove || $autoconfirmedCanMove ) ) {
                    // custom message if logged-in users without any special rights can move
                    $errors[] = [ 'movenologintext' ];
                } else {
                    $errors[] = [ 'movenotallowed' ];
                }
            }
        } elseif ( $action == 'move-target' ) {
            if ( !$user->isAllowed( 'move' ) ) {
                // User can't move anything
                $errors[] = [ 'movenotallowed' ];
            } elseif ( !$user->isAllowed( 'move-rootuserpages' )
                    && $this->mNamespace == NS_USER && !$this->isSubpage() ) {
                // Show user page-specific message only if the user can move other pages
                $errors[] = [ 'cant-move-to-user-page' ];
            } elseif ( !$user->isAllowed( 'move-categorypages' )
                    && $this->mNamespace == NS_CATEGORY ) {
                // Show category page-specific message only if the user can move other pages
                $errors[] = [ 'cant-move-to-category-page' ];
            }
        } elseif ( !$user->isAllowed( $action ) ) {
            $errors[] = $this->missingPermissionError( $action, $short );
        }
 
        return $errors;
    }
 
    private function resultToError( $errors, $result ) {
        if ( is_array( $result ) && count( $result ) && !is_array( $result[0] ) ) {
            // A single array representing an error
            $errors[] = $result;
        } elseif ( is_array( $result ) && is_array( $result[0] ) ) {
            // A nested array representing multiple errors
            $errors = array_merge( $errors, $result );
        } elseif ( $result !== '' && is_string( $result ) ) {
            // A string representing a message-id
            $errors[] = [ $result ];
        } elseif ( $result instanceof MessageSpecifier ) {
            // A message specifier representing an error
            $errors[] = [ $result ];
        } elseif ( $result === false ) {
            // a generic "We don't want them to do that"
            $errors[] = [ 'badaccess-group0' ];
        }
        return $errors;
    }
 
    private function checkPermissionHooks( $action, $user, $errors, $rigor, $short ) {
        // Use getUserPermissionsErrors instead
        $result = '';
        // Avoid PHP 7.1 warning from passing $this by reference
        $titleRef = $this;
        if ( !Hooks::run( 'userCan', [ &$titleRef, &$user, $action, &$result ] ) ) {
            return $result ? [] : [ [ 'badaccess-group0' ] ];
        }
        // Check getUserPermissionsErrors hook
        // Avoid PHP 7.1 warning from passing $this by reference
        $titleRef = $this;
        if ( !Hooks::run( 'getUserPermissionsErrors', [ &$titleRef, &$user, $action, &$result ] ) ) {
            $errors = $this->resultToError( $errors, $result );
        }
        // Check getUserPermissionsErrorsExpensive hook
        if (
            $rigor !== 'quick'
            && !( $short && count( $errors ) > 0 )
            && !Hooks::run( 'getUserPermissionsErrorsExpensive', [ &$titleRef, &$user, $action, &$result ] )
        ) {
            $errors = $this->resultToError( $errors, $result );
        }
 
        return $errors;
    }
 
    private function checkSpecialsAndNSPermissions( $action, $user, $errors, $rigor, $short ) {
        # Only 'createaccount' can be performed on special pages,
        # which don't actually exist in the DB.
        if ( $this->isSpecialPage() && $action !== 'createaccount' ) {
            $errors[] = [ 'ns-specialprotected' ];
        }
 
        # Check $wgNamespaceProtection for restricted namespaces
        if ( $this->isNamespaceProtected( $user ) ) {
            $ns = $this->mNamespace == NS_MAIN ?
                wfMessage( 'nstab-main' )->text() : $this->getNsText();
            $errors[] = $this->mNamespace == NS_MEDIAWIKI ?
                [ 'protectedinterface', $action ] : [ 'namespaceprotected', $ns, $action ];
        }
 
        return $errors;
    }
 
    private function checkCSSandJSPermissions( $action, $user, $errors, $rigor, $short ) {
        # Protect css/js subpages of user pages
        # XXX: this might be better using restrictions
        if ( $action != 'patrol' ) {
            if ( preg_match( '/^' . preg_quote( $user->getName(), '/' ) . '\//', $this->mTextform ) ) {
                if ( $this->isCssSubpage() && !$user->isAllowedAny( 'editmyusercss', 'editusercss' ) ) {
                    $errors[] = [ 'mycustomcssprotected', $action ];
                } elseif ( $this->isJsSubpage() && !$user->isAllowedAny( 'editmyuserjs', 'edituserjs' ) ) {
                    $errors[] = [ 'mycustomjsprotected', $action ];
                }
            } else {
                if ( $this->isCssSubpage() && !$user->isAllowed( 'editusercss' ) ) {
                    $errors[] = [ 'customcssprotected', $action ];
                } elseif ( $this->isJsSubpage() && !$user->isAllowed( 'edituserjs' ) ) {
                    $errors[] = [ 'customjsprotected', $action ];
                }
            }
        }
 
        return $errors;
    }
 
    private function checkPageRestrictions( $action, $user, $errors, $rigor, $short ) {
        foreach ( $this->getRestrictions( $action ) as $right ) {
            // Backwards compatibility, rewrite sysop -> editprotected
            if ( $right == 'sysop' ) {
                $right = 'editprotected';
            }
            // Backwards compatibility, rewrite autoconfirmed -> editsemiprotected
            if ( $right == 'autoconfirmed' ) {
                $right = 'editsemiprotected';
            }
            if ( $right == '' ) {
                continue;
            }
            if ( !$user->isAllowed( $right ) ) {
                $errors[] = [ 'protectedpagetext', $right, $action ];
            } elseif ( $this->mCascadeRestriction && !$user->isAllowed( 'protect' ) ) {
                $errors[] = [ 'protectedpagetext', 'protect', $action ];
            }
        }
 
        return $errors;
    }
 
    private function checkCascadingSourcesRestrictions( $action, $user, $errors, $rigor, $short ) {
        if ( $rigor !== 'quick' && !$this->isCssJsSubpage() ) {
            # We /could/ use the protection level on the source page, but it's
            # fairly ugly as we have to establish a precedence hierarchy for pages
            # included by multiple cascade-protected pages. So just restrict
            # it to people with 'protect' permission, as they could remove the
            # protection anyway.
            list( $cascadingSources, $restrictions ) = $this->getCascadeProtectionSources();
            # Cascading protection depends on more than this page...
            # Several cascading protected pages may include this page...
            # Check each cascading level
            # This is only for protection restrictions, not for all actions
            if ( isset( $restrictions[$action] ) ) {
                foreach ( $restrictions[$action] as $right ) {
                    // Backwards compatibility, rewrite sysop -> editprotected
                    if ( $right == 'sysop' ) {
                        $right = 'editprotected';
                    }
                    // Backwards compatibility, rewrite autoconfirmed -> editsemiprotected
                    if ( $right == 'autoconfirmed' ) {
                        $right = 'editsemiprotected';
                    }
                    if ( $right != '' && !$user->isAllowedAll( 'protect', $right ) ) {
                        $pages = '';
                        foreach ( $cascadingSources as $page ) {
                            $pages .= '* [[:' . $page->getPrefixedText() . "]]\n";
                        }
                        $errors[] = [ 'cascadeprotected', count( $cascadingSources ), $pages, $action ];
                    }
                }
            }
        }
 
        return $errors;
    }
 
    private function checkActionPermissions( $action, $user, $errors, $rigor, $short ) {
        global $wgDeleteRevisionsLimit, $wgLang;
 
        if ( $action == 'protect' ) {
            if ( count( $this->getUserPermissionsErrorsInternal( 'edit', $user, $rigor, true ) ) ) {
                // If they can't edit, they shouldn't protect.
                $errors[] = [ 'protect-cantedit' ];
            }
        } elseif ( $action == 'create' ) {
            $title_protection = $this->getTitleProtection();
            if ( $title_protection ) {
                if ( $title_protection['permission'] == ''
                    || !$user->isAllowed( $title_protection['permission'] )
                ) {
                    $errors[] = [
                        'titleprotected',
                        User::whoIs( $title_protection['user'] ),
                        $title_protection['reason']
                    ];
                }
            }
        } elseif ( $action == 'move' ) {
            // Check for immobile pages
            if ( !MWNamespace::isMovable( $this->mNamespace ) ) {
                // Specific message for this case
                $errors[] = [ 'immobile-source-namespace', $this->getNsText() ];
            } elseif ( !$this->isMovable() ) {
                // Less specific message for rarer cases
                $errors[] = [ 'immobile-source-page' ];
            }
        } elseif ( $action == 'move-target' ) {
            if ( !MWNamespace::isMovable( $this->mNamespace ) ) {
                $errors[] = [ 'immobile-target-namespace', $this->getNsText() ];
            } elseif ( !$this->isMovable() ) {
                $errors[] = [ 'immobile-target-page' ];
            }
        } elseif ( $action == 'delete' ) {
            $tempErrors = $this->checkPageRestrictions( 'edit', $user, [], $rigor, true );
            if ( !$tempErrors ) {
                $tempErrors = $this->checkCascadingSourcesRestrictions( 'edit',
                    $user, $tempErrors, $rigor, true );
            }
            if ( $tempErrors ) {
                // If protection keeps them from editing, they shouldn't be able to delete.
                $errors[] = [ 'deleteprotected' ];
            }
            if ( $rigor !== 'quick' && $wgDeleteRevisionsLimit
                && !$this->userCan( 'bigdelete', $user ) && $this->isBigDeletion()
            ) {
                $errors[] = [ 'delete-toobig', $wgLang->formatNum( $wgDeleteRevisionsLimit ) ];
            }
        } elseif ( $action === 'undelete' ) {
            if ( count( $this->getUserPermissionsErrorsInternal( 'edit', $user, $rigor, true ) ) ) {
                // Undeleting implies editing
                $errors[] = [ 'undelete-cantedit' ];
            }
            if ( !$this->exists()
                && count( $this->getUserPermissionsErrorsInternal( 'create', $user, $rigor, true ) )
            ) {
                // Undeleting where nothing currently exists implies creating
                $errors[] = [ 'undelete-cantcreate' ];
            }
        }
        return $errors;
    }
 
    private function checkUserBlock( $action, $user, $errors, $rigor, $short ) {
        global $wgEmailConfirmToEdit, $wgBlockDisablesLogin;
        // Account creation blocks handled at userlogin.
        // Unblocking handled in SpecialUnblock
        if ( $rigor === 'quick' || in_array( $action, [ 'createaccount', 'unblock' ] ) ) {
            return $errors;
        }
 
        // Optimize for a very common case
        if ( $action === 'read' && !$wgBlockDisablesLogin ) {
            return $errors;
        }
 
        if ( $wgEmailConfirmToEdit && !$user->isEmailConfirmed() ) {
            $errors[] = [ 'confirmedittext' ];
        }
 
        $useSlave = ( $rigor !== 'secure' );
        if ( ( $action == 'edit' || $action == 'create' )
            && !$user->isBlockedFrom( $this, $useSlave )
        ) {
            // Don't block the user from editing their own talk page unless they've been
            // explicitly blocked from that too.
        } elseif ( $user->isBlocked() && $user->getBlock()->prevents( $action ) !== false ) {
            // @todo FIXME: Pass the relevant context into this function.
            $errors[] = $user->getBlock()->getPermissionsError( RequestContext::getMain() );
        }
 
        return $errors;
    }
 
    private function checkReadPermissions( $action, $user, $errors, $rigor, $short ) {
        global $wgWhitelistRead, $wgWhitelistReadRegexp;
 
        $whitelisted = false;
        if ( User::isEveryoneAllowed( 'read' ) ) {
            # Shortcut for public wikis, allows skipping quite a bit of code
            $whitelisted = true;
        } elseif ( $user->isAllowed( 'read' ) ) {
            # If the user is allowed to read pages, he is allowed to read all pages
            $whitelisted = true;
        } elseif ( $this->isSpecial( 'Userlogin' )
            || $this->isSpecial( 'PasswordReset' )
            || $this->isSpecial( 'Userlogout' )
        ) {
            # Always grant access to the login page.
            # Even anons need to be able to log in.
            $whitelisted = true;
        } elseif ( is_array( $wgWhitelistRead ) && count( $wgWhitelistRead ) ) {
            # Time to check the whitelist
            # Only do these checks is there's something to check against
            $name = $this->getPrefixedText();
            $dbName = $this->getPrefixedDBkey();
 
            // Check for explicit whitelisting with and without underscores
            if ( in_array( $name, $wgWhitelistRead, true ) || in_array( $dbName, $wgWhitelistRead, true ) ) {
                $whitelisted = true;
            } elseif ( $this->getNamespace() == NS_MAIN ) {
                # Old settings might have the title prefixed with
                # a colon for main-namespace pages
                if ( in_array( ':' . $name, $wgWhitelistRead ) ) {
                    $whitelisted = true;
                }
            } elseif ( $this->isSpecialPage() ) {
                # If it's a special page, ditch the subpage bit and check again
                $name = $this->getDBkey();
                list( $name, /* $subpage */ ) = SpecialPageFactory::resolveAlias( $name );
                if ( $name ) {
                    $pure = SpecialPage::getTitleFor( $name )->getPrefixedText();
                    if ( in_array( $pure, $wgWhitelistRead, true ) ) {
                        $whitelisted = true;
                    }
                }
            }
        }
 
        if ( !$whitelisted && is_array( $wgWhitelistReadRegexp ) && !empty( $wgWhitelistReadRegexp ) ) {
            $name = $this->getPrefixedText();
            // Check for regex whitelisting
            foreach ( $wgWhitelistReadRegexp as $listItem ) {
                if ( preg_match( $listItem, $name ) ) {
                    $whitelisted = true;
                    break;
                }
            }
        }
 
        if ( !$whitelisted ) {
            # If the title is not whitelisted, give extensions a chance to do so...
            Hooks::run( 'TitleReadWhitelist', [ $this, $user, &$whitelisted ] );
            if ( !$whitelisted ) {
                $errors[] = $this->missingPermissionError( $action, $short );
            }
        }
 
        return $errors;
    }
 
    private function missingPermissionError( $action, $short ) {
        // We avoid expensive display logic for quickUserCan's and such
        if ( $short ) {
            return [ 'badaccess-group0' ];
        }
 
        return User::newFatalPermissionDeniedStatus( $action )->getErrorsArray()[0];
    }
 
    protected function getUserPermissionsErrorsInternal(
        $action, $user, $rigor = 'secure', $short = false
    ) {
        if ( $rigor === true ) {
            $rigor = 'secure'; // b/c
        } elseif ( $rigor === false ) {
            $rigor = 'quick'; // b/c
        } elseif ( !in_array( $rigor, [ 'quick', 'full', 'secure' ] ) ) {
            throw new Exception( "Invalid rigor parameter '$rigor'." );
        }
 
        # Read has special handling
        if ( $action == 'read' ) {
            $checks = [
                'checkPermissionHooks',
                'checkReadPermissions',
                'checkUserBlock', // for wgBlockDisablesLogin
            ];
        # Don't call checkSpecialsAndNSPermissions or checkCSSandJSPermissions
        # here as it will lead to duplicate error messages. This is okay to do
        # since anywhere that checks for create will also check for edit, and
        # those checks are called for edit.
        } elseif ( $action == 'create' ) {
            $checks = [
                'checkQuickPermissions',
                'checkPermissionHooks',
                'checkPageRestrictions',
                'checkCascadingSourcesRestrictions',
                'checkActionPermissions',
                'checkUserBlock'
            ];
        } else {
            $checks = [
                'checkQuickPermissions',
                'checkPermissionHooks',
                'checkSpecialsAndNSPermissions',
                'checkCSSandJSPermissions',
                'checkPageRestrictions',
                'checkCascadingSourcesRestrictions',
                'checkActionPermissions',
                'checkUserBlock'
            ];
        }
 
        $errors = [];
        while ( count( $checks ) > 0 &&
                !( $short && count( $errors ) > 0 ) ) {
            $method = array_shift( $checks );
            $errors = $this->$method( $action, $user, $errors, $rigor, $short );
        }
 
        return $errors;
    }
 
    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;
    }
 
    public function getRestrictionTypes() {
        if ( $this->isSpecialPage() ) {
            return [];
        }
 
        $types = self::getFilteredRestrictionTypes( $this->exists() );
 
        if ( $this->getNamespace() != NS_FILE ) {
            # Remove the upload restriction for non-file titles
            $types = array_diff( $types, [ 'upload' ] );
        }
 
        Hooks::run( 'TitleGetRestrictionTypes', [ $this, &$types ] );
 
        wfDebug( __METHOD__ . ': applicable restrictions to [[' .
            $this->getPrefixedText() . ']] are {' . implode( ',', $types ) . "}\n" );
 
        return $types;
    }
 
    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;
    }
 
    protected function getTitleProtectionInternal() {
        // Can't protect pages in special namespaces
        if ( $this->getNamespace() < 0 ) {
            return false;
        }
 
        // Can't protect pages that exist.
        if ( $this->exists() ) {
            return false;
        }
 
        if ( $this->mTitleProtection === null ) {
            $dbr = wfGetDB( DB_REPLICA );
            $commentStore = new CommentStore( 'pt_reason' );
            $commentQuery = $commentStore->getJoin();
            $res = $dbr->select(
                [ 'protected_titles' ] + $commentQuery['tables'],
                [
                    'user' => 'pt_user',
                    'expiry' => 'pt_expiry',
                    'permission' => 'pt_create_perm'
                ] + $commentQuery['fields'],
                [ 'pt_namespace' => $this->getNamespace(), 'pt_title' => $this->getDBkey() ],
                __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( $row )->text,
                ];
            } else {
                $this->mTitleProtection = false;
            }
        }
        return $this->mTitleProtection;
    }
 
    public function deleteTitleProtection() {
        $dbw = wfGetDB( DB_MASTER );
 
        $dbw->delete(
            'protected_titles',
            [ 'pt_namespace' => $this->getNamespace(), 'pt_title' => $this->getDBkey() ],
            __METHOD__
        );
        $this->mTitleProtection = false;
    }
 
    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 );
    }
 
    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;
    }
 
    public function isNamespaceProtected( User $user ) {
        global $wgNamespaceProtection;
 
        if ( isset( $wgNamespaceProtection[$this->mNamespace] ) ) {
            foreach ( (array)$wgNamespaceProtection[$this->mNamespace] as $right ) {
                if ( $right != '' && !$user->isAllowed( $right ) ) {
                    return true;
                }
            }
        }
        return false;
    }
 
    public function isCascadeProtected() {
        list( $sources, /* $restrictions */ ) = $this->getCascadeProtectionSources( false );
        return ( $sources > 0 );
    }
 
    public function areCascadeProtectionSourcesLoaded( $getPages = true ) {
        return $getPages ? $this->mCascadeSources !== null : $this->mHasCascadingRestrictions !== null;
    }
 
    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->getNamespace() == NS_FILE ) {
            $tables = [ 'imagelinks', 'page_restrictions' ];
            $where_clauses = [
                'il_to' => $this->getDBkey(),
                'il_from=pr_page',
                'pr_cascade' => 1
            ];
        } else {
            $tables = [ 'templatelinks', 'page_restrictions' ];
            $where_clauses = [
                'tl_namespace' => $this->getNamespace(),
                'tl_title' => $this->getDBkey(),
                '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 ];
    }
 
    public function areRestrictionsLoaded() {
        return $this->mRestrictionsLoaded;
    }
 
    public function getRestrictions( $action ) {
        if ( !$this->mRestrictionsLoaded ) {
            $this->loadRestrictions();
        }
        return isset( $this->mRestrictions[$action] )
                ? $this->mRestrictions[$action]
                : [];
    }
 
    public function getAllRestrictions() {
        if ( !$this->mRestrictionsLoaded ) {
            $this->loadRestrictions();
        }
        return $this->mRestrictions;
    }
 
    public function getRestrictionExpiry( $action ) {
        if ( !$this->mRestrictionsLoaded ) {
            $this->loadRestrictions();
        }
        return isset( $this->mRestrictionsExpiry[$action] ) ? $this->mRestrictionsExpiry[$action] : false;
    }
 
    function areRestrictionsCascading() {
        if ( !$this->mRestrictionsLoaded ) {
            $this->loadRestrictions();
        }
 
        return $this->mCascadeRestriction;
    }
 
    public function loadRestrictionsFromRows( $rows, $oldFashionedRestrictions = null ) {
        $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 ) {
            $this->mOldRestrictions = $dbr->selectField( 'page', 'page_restrictions',
                [ 'page_id' => $this->getArticleID() ], __METHOD__ );
        }
 
        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 |= $row->pr_cascade;
                }
            }
        }
 
        $this->mRestrictionsLoaded = true;
    }
 
    public function loadRestrictions( $oldFashionedRestrictions = null ) {
        if ( $this->mRestrictionsLoaded ) {
            return;
        }
 
        $id = $this->getArticleID();
        if ( $id ) {
            $cache = ObjectCache::getMainWANInstance();
            $rows = $cache->getWithSetCallback(
                // Page protections always leave a new null revision
                $cache->makeKey( 'page-restrictions', $id, $this->getLatestRevID() ),
                $cache::TTL_DAY,
                function ( $curValue, &$ttl, array &$setOpts ) {
                    $dbr = wfGetDB( DB_REPLICA );
 
                    $setOpts += Database::getCacheSetOptions( $dbr );
 
                    return iterator_to_array(
                        $dbr->select(
                            'page_restrictions',
                            [ 'pr_type', 'pr_expiry', 'pr_level', 'pr_cascade' ],
                            [ 'pr_page' => $this->getArticleID() ],
                            __METHOD__
                        )
                    );
                }
            );
 
            $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;
        }
    }
 
    public function flushRestrictions() {
        $this->mRestrictionsLoaded = false;
        $this->mTitleProtection = null;
    }
 
    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
                );
            }
        ) );
    }
 
    public function hasSubpages() {
        if ( !MWNamespace::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->count();
            }
        }
 
        return $this->mHasSubpages;
    }
 
    public function getSubpages( $limit = -1 ) {
        if ( !MWNamespace::hasSubpages( $this->getNamespace() ) ) {
            return [];
        }
 
        $dbr = wfGetDB( DB_REPLICA );
        $conds['page_namespace'] = $this->getNamespace();
        $conds[] = 'page_title ' . $dbr->buildLike( $this->getDBkey() . '/', $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
            )
        );
    }
 
    public function isDeleted() {
        if ( $this->getNamespace() < 0 ) {
            $n = 0;
        } else {
            $dbr = wfGetDB( DB_REPLICA );
 
            $n = $dbr->selectField( 'archive', 'COUNT(*)',
                [ 'ar_namespace' => $this->getNamespace(), 'ar_title' => $this->getDBkey() ],
                __METHOD__
            );
            if ( $this->getNamespace() == NS_FILE ) {
                $n += $dbr->selectField( 'filearchive', 'COUNT(*)',
                    [ 'fa_name' => $this->getDBkey() ],
                    __METHOD__
                );
            }
        }
        return (int)$n;
    }
 
    public function isDeletedQuick() {
        if ( $this->getNamespace() < 0 ) {
            return false;
        }
        $dbr = wfGetDB( DB_REPLICA );
        $deleted = (bool)$dbr->selectField( 'archive', '1',
            [ 'ar_namespace' => $this->getNamespace(), 'ar_title' => $this->getDBkey() ],
            __METHOD__
        );
        if ( !$deleted && $this->getNamespace() == NS_FILE ) {
            $deleted = (bool)$dbr->selectField( 'filearchive', '1',
                [ 'fa_name' => $this->getDBkey() ],
                __METHOD__
            );
        }
        return $deleted;
    }
 
    public function getArticleID( $flags = 0 ) {
        if ( $this->getNamespace() < 0 ) {
            $this->mArticleID = 0;
            return $this->mArticleID;
        }
        $linkCache = LinkCache::singleton();
        if ( $flags & self::GAID_FOR_UPDATE ) {
            $oldUpdate = $linkCache->forUpdate( true );
            $linkCache->clearLink( $this );
            $this->mArticleID = $linkCache->addLinkObj( $this );
            $linkCache->forUpdate( $oldUpdate );
        } else {
            if ( -1 == $this->mArticleID ) {
                $this->mArticleID = $linkCache->addLinkObj( $this );
            }
        }
        return $this->mArticleID;
    }
 
    public function isRedirect( $flags = 0 ) {
        if ( !is_null( $this->mRedirect ) ) {
            return $this->mRedirect;
        }
        if ( !$this->getArticleID( $flags ) ) {
            $this->mRedirect = false;
            return $this->mRedirect;
        }
 
        $linkCache = LinkCache::singleton();
        $linkCache->addLinkObj( $this ); # in case we already had an article ID
        $cached = $linkCache->getGoodLinkFieldObj( $this, 'redirect' );
        if ( $cached === null ) {
            # Trust LinkCache's state over our own
            # LinkCache is telling us that the page doesn't exist, despite there being cached
            # data relating to an existing page in $this->mArticleID. Updaters should clear
            # LinkCache as appropriate, or use $flags = Title::GAID_FOR_UPDATE. If that flag is
            # set, then LinkCache will definitely be up to date here, since getArticleID() forces
            # LinkCache to refresh its data from the master.
            $this->mRedirect = false;
            return $this->mRedirect;
        }
 
        $this->mRedirect = (bool)$cached;
 
        return $this->mRedirect;
    }
 
    public function getLength( $flags = 0 ) {
        if ( $this->mLength != -1 ) {
            return $this->mLength;
        }
        if ( !$this->getArticleID( $flags ) ) {
            $this->mLength = 0;
            return $this->mLength;
        }
        $linkCache = LinkCache::singleton();
        $linkCache->addLinkObj( $this ); # in case we already had an article ID
        $cached = $linkCache->getGoodLinkFieldObj( $this, 'length' );
        if ( $cached === null ) {
            # Trust LinkCache's state over our own, as for isRedirect()
            $this->mLength = 0;
            return $this->mLength;
        }
 
        $this->mLength = intval( $cached );
 
        return $this->mLength;
    }
 
    public function getLatestRevID( $flags = 0 ) {
        if ( !( $flags & self::GAID_FOR_UPDATE ) && $this->mLatestID !== false ) {
            return intval( $this->mLatestID );
        }
        if ( !$this->getArticleID( $flags ) ) {
            $this->mLatestID = 0;
            return $this->mLatestID;
        }
        $linkCache = LinkCache::singleton();
        $linkCache->addLinkObj( $this ); # in case we already had an article ID
        $cached = $linkCache->getGoodLinkFieldObj( $this, 'revision' );
        if ( $cached === null ) {
            # Trust LinkCache's state over our own, as for isRedirect()
            $this->mLatestID = 0;
            return $this->mLatestID;
        }
 
        $this->mLatestID = intval( $cached );
 
        return $this->mLatestID;
    }
 
    public function resetArticleID( $newid ) {
        $linkCache = LinkCache::singleton();
        $linkCache->clearLink( $this );
 
        if ( $newid === false ) {
            $this->mArticleID = -1;
        } else {
            $this->mArticleID = intval( $newid );
        }
        $this->mRestrictionsLoaded = false;
        $this->mRestrictions = [];
        $this->mOldRestrictions = false;
        $this->mRedirect = null;
        $this->mLength = -1;
        $this->mLatestID = false;
        $this->mContentModel = false;
        $this->mEstimateRevisions = null;
        $this->mPageLanguage = false;
        $this->mDbPageLanguage = false;
        $this->mIsBigDeletion = null;
    }
 
    public static function clearCaches() {
        $linkCache = LinkCache::singleton();
        $linkCache->clear();
 
        $titleCache = self::getTitleCache();
        $titleCache->clear();
    }
 
    public static function capitalize( $text, $ns = NS_MAIN ) {
        global $wgContLang;
 
        if ( MWNamespace::isCapitalized( $ns ) ) {
            return $wgContLang->ucfirst( $text );
        } else {
            return $text;
        }
    }
 
    private function secureAndSplit() {
        # Initialisation
        $this->mInterwiki = '';
        $this->mFragment = '';
        $this->mNamespace = $this->mDefaultNamespace; # Usually NS_MAIN
 
        $dbkey = $this->mDbkeyform;
 
        // @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
        $titleCodec = MediaWikiServices::getInstance()->getTitleParser();
        // MalformedTitleException can be thrown here
        $parts = $titleCodec->splitTitleString( $dbkey, $this->getDefaultNamespace() );
 
        # Fill fields
        $this->setFragment( '#' . $parts['fragment'] );
        $this->mInterwiki = $parts['interwiki'];
        $this->mLocalInterwiki = $parts['local_interwiki'];
        $this->mNamespace = $parts['namespace'];
        $this->mUserCaseDBKey = $parts['user_case_dbkey'];
 
        $this->mDbkeyform = $parts['dbkey'];
        $this->mUrlform = wfUrlencode( $this->mDbkeyform );
        $this->mTextform = strtr( $this->mDbkeyform, '_', ' ' );
 
        # We already know that some pages won't be in the database!
        if ( $this->isExternal() || $this->isSpecialPage() ) {
            $this->mArticleID = 0;
        }
 
        return true;
    }
 
    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" => $this->getNamespace(),
                "{$prefix}_title" => $this->getDBkey() ],
            __METHOD__,
            $options
        );
 
        $retVal = [];
        if ( $res->numRows() ) {
            $linkCache = LinkCache::singleton();
            foreach ( $res as $row ) {
                $titleObj = self::makeTitle( $row->page_namespace, $row->page_title );
                if ( $titleObj ) {
                    $linkCache->addGoodLinkObjFromRow( $titleObj, $row );
                    $retVal[] = $titleObj;
                }
            }
        }
        return $retVal;
    }
 
    public function getTemplateLinksTo( $options = [] ) {
        return $this->getLinksTo( $options, 'templatelinks', 'tl' );
    }
 
    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";
 
        $res = $db->select(
            [ $table, 'page' ],
            array_merge(
                [ $blNamespace, $blTitle ],
                WikiPage::selectFields()
            ),
            [ "{$prefix}_from" => $id ],
            __METHOD__,
            $options,
            [ 'page' => [
                'LEFT JOIN',
                [ "page_namespace=$blNamespace", "page_title=$blTitle" ]
            ] ]
        );
 
        $retVal = [];
        $linkCache = LinkCache::singleton();
        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;
    }
 
    public function getTemplateLinksFrom( $options = [] ) {
        return $this->getLinksFrom( $options, 'templatelinks', 'tl' );
    }
 
    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;
    }
 
    public function getCdnUrls() {
        $urls = [
            $this->getInternalURL(),
            $this->getInternalURL( 'action=history' )
        ];
 
        $pageLang = $this->getPageLanguage();
        if ( $pageLang->hasVariants() ) {
            $variants = $pageLang->getVariants();
            foreach ( $variants as $vCode ) {
                $urls[] = $this->getInternalURL( $vCode );
            }
        }
 
        // If we are looking at a css/js user subpage, purge the action=raw.
        if ( $this->isJsSubpage() ) {
            $urls[] = $this->getInternalURL( 'action=raw&ctype=text/javascript' );
        } elseif ( $this->isCssSubpage() ) {
            $urls[] = $this->getInternalURL( 'action=raw&ctype=text/css' );
        }
 
        Hooks::run( 'TitleSquidURLs', [ $this, &$urls ] );
        return $urls;
    }
 
    public function getSquidURLs() {
        return $this->getCdnUrls();
    }
 
    public function purgeSquid() {
        DeferredUpdates::addUpdate(
            new CdnCacheUpdate( $this->getCdnUrls() ),
            DeferredUpdates::PRESEND
        );
    }
 
    public function isValidMoveOperation( &$nt, $auth = true, $reason = '' ) {
        global $wgUser;
 
        if ( !( $nt instanceof Title ) ) {
            // Normally we'd add this to $errors, but we'll get
            // lots of syntax errors if $nt is not an object
            return [ [ 'badtitletext' ] ];
        }
 
        $mp = new MovePage( $this, $nt );
        $errors = $mp->isValidMove()->getErrorsArray();
        if ( $auth ) {
            $errors = wfMergeErrorArrays(
                $errors,
                $mp->checkPermissions( $wgUser, $reason )->getErrorsArray()
            );
        }
 
        return $errors ?: true;
    }
 
    protected function validateFileMoveOperation( $nt ) {
        global $wgUser;
 
        $errors = [];
 
        $destFile = wfLocalFile( $nt );
        $destFile->load( File::READ_LATEST );
        if ( !$wgUser->isAllowed( 'reupload-shared' )
            && !$destFile->exists() && wfFindFile( $nt )
        ) {
            $errors[] = [ 'file-exists-sharedrepo' ];
        }
 
        return $errors;
    }
 
    public function moveTo( &$nt, $auth = true, $reason = '', $createRedirect = true,
        array $changeTags = []
    ) {
        global $wgUser;
        $err = $this->isValidMoveOperation( $nt, $auth, $reason );
        if ( is_array( $err ) ) {
            // Auto-block user's IP if the account was "hard" blocked
            $wgUser->spreadAnyEditBlock();
            return $err;
        }
        // Check suppressredirect permission
        if ( $auth && !$wgUser->isAllowed( 'suppressredirect' ) ) {
            $createRedirect = true;
        }
 
        $mp = new MovePage( $this, $nt );
        $status = $mp->move( $wgUser, $reason, $createRedirect, $changeTags );
        if ( $status->isOK() ) {
            return true;
        } else {
            return $status->getErrorsArray();
        }
    }
 
    public function moveSubpages( $nt, $auth = true, $reason = '', $createRedirect = true,
        array $changeTags = []
    ) {
        global $wgMaximumMovedPages;
        // Check permissions
        if ( !$this->userCan( 'move-subpages' ) ) {
            return [
                [ 'cant-move-subpages' ],
            ];
        }
        // Do the source and target namespaces support subpages?
        if ( !MWNamespace::hasSubpages( $this->getNamespace() ) ) {
            return [
                [ 'namespace-nosubpages', MWNamespace::getCanonicalName( $this->getNamespace() ) ],
            ];
        }
        if ( !MWNamespace::hasSubpages( $nt->getNamespace() ) ) {
            return [
                [ 'namespace-nosubpages', MWNamespace::getCanonicalName( $nt->getNamespace() ) ],
            ];
        }
 
        $subpages = $this->getSubpages( $wgMaximumMovedPages + 1 );
        $retval = [];
        $count = 0;
        foreach ( $subpages as $oldSubpage ) {
            $count++;
            if ( $count > $wgMaximumMovedPages ) {
                $retval[$oldSubpage->getPrefixedText()] = [
                    [ 'movepage-max-pages', $wgMaximumMovedPages ],
                ];
                break;
            }
 
            // We don't know whether this function was called before
            // or after moving the root page, so check both
            // $this and $nt
            if ( $oldSubpage->getArticleID() == $this->getArticleID()
                || $oldSubpage->getArticleID() == $nt->getArticleID()
            ) {
                // When moving a page to a subpage of itself,
                // don't move it twice
                continue;
            }
            $newPageName = preg_replace(
                    '#^' . preg_quote( $this->getDBkey(), '#' ) . '#',
                    StringUtils::escapeRegexReplacement( $nt->getDBkey() ), # T23234
                    $oldSubpage->getDBkey() );
            if ( $oldSubpage->isTalkPage() ) {
                $newNs = $nt->getTalkPage()->getNamespace();
            } else {
                $newNs = $nt->getSubjectPage()->getNamespace();
            }
            # T16385: we need makeTitleSafe because the new page names may
            # be longer than 255 characters.
            $newSubpage = self::makeTitleSafe( $newNs, $newPageName );
 
            $success = $oldSubpage->moveTo( $newSubpage, $auth, $reason, $createRedirect, $changeTags );
            if ( $success === true ) {
                $retval[$oldSubpage->getPrefixedText()] = $newSubpage->getPrefixedText();
            } else {
                $retval[$oldSubpage->getPrefixedText()] = $success;
            }
        }
        return $retval;
    }
 
    public function isSingleRevRedirect() {
        global $wgContentHandlerUseDB;
 
        $dbw = wfGetDB( DB_MASTER );
 
        # Is it a redirect?
        $fields = [ 'page_is_redirect', 'page_latest', 'page_id' ];
        if ( $wgContentHandlerUseDB ) {
            $fields[] = 'page_content_model';
        }
 
        $row = $dbw->selectRow( 'page',
            $fields,
            $this->pageCond(),
            __METHOD__,
            [ 'FOR UPDATE' ]
        );
        # Cache some fields we may want
        $this->mArticleID = $row ? intval( $row->page_id ) : 0;
        $this->mRedirect = $row ? (bool)$row->page_is_redirect : false;
        $this->mLatestID = $row ? intval( $row->page_latest ) : false;
        $this->mContentModel = $row && isset( $row->page_content_model )
            ? strval( $row->page_content_model )
            : false;
 
        if ( !$this->mRedirect ) {
            return false;
        }
        # Does the article have a history?
        $row = $dbw->selectField( [ 'page', 'revision' ],
            'rev_id',
            [ 'page_namespace' => $this->getNamespace(),
                'page_title' => $this->getDBkey(),
                'page_id=rev_page',
                'page_latest != rev_id'
            ],
            __METHOD__,
            [ 'FOR UPDATE' ]
        );
        # Return true if there was no history
        return ( $row === false );
    }
 
    public function isValidMoveTarget( $nt ) {
        # Is it an existing file?
        if ( $nt->getNamespace() == NS_FILE ) {
            $file = wfLocalFile( $nt );
            $file->load( File::READ_LATEST );
            if ( $file->exists() ) {
                wfDebug( __METHOD__ . ": file exists\n" );
                return false;
            }
        }
        # Is it a redirect with no history?
        if ( !$nt->isSingleRevRedirect() ) {
            wfDebug( __METHOD__ . ": not a one-rev redirect\n" );
            return false;
        }
        # Get the article text
        $rev = Revision::newFromTitle( $nt, false, Revision::READ_LATEST );
        if ( !is_object( $rev ) ) {
            return false;
        }
        $content = $rev->getContent();
        # Does the redirect point to the source?
        # Or is it a broken self-redirect, usually caused by namespace collisions?
        $redirTitle = $content ? $content->getRedirectTarget() : null;
 
        if ( $redirTitle ) {
            if ( $redirTitle->getPrefixedDBkey() != $this->getPrefixedDBkey() &&
                $redirTitle->getPrefixedDBkey() != $nt->getPrefixedDBkey() ) {
                wfDebug( __METHOD__ . ": redirect points to other page\n" );
                return false;
            } else {
                return true;
            }
        } else {
            # Fail safe (not a redirect after all. strange.)
            wfDebug( __METHOD__ . ": failsafe: database sais " . $nt->getPrefixedDBkey() .
                        " is a redirect, but it doesn't contain a valid redirect.\n" );
            return false;
        }
    }
 
    public function getParentCategories() {
        global $wgContLang;
 
        $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 ) {
            foreach ( $res as $row ) {
                // $data[] = Title::newFromText($wgContLang->getNsText ( NS_CATEGORY ).':'.$row->cl_to);
                $data[$wgContLang->getNsText( NS_CATEGORY ) . ':' . $row->cl_to] = $this->getFullText();
            }
        }
        return $data;
    }
 
    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;
    }
 
    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 ];
        }
    }
 
    private function getRelativeRevisionID( $revId, $flags, $dir ) {
        $revId = (int)$revId;
        if ( $dir === 'next' ) {
            $op = '>';
            $sort = 'ASC';
        } elseif ( $dir === 'prev' ) {
            $op = '<';
            $sort = 'DESC';
        } else {
            throw new InvalidArgumentException( '$dir must be "next" or "prev"' );
        }
 
        if ( $flags & self::GAID_FOR_UPDATE ) {
            $db = wfGetDB( DB_MASTER );
        } else {
            $db = wfGetDB( DB_REPLICA, 'contributions' );
        }
 
        // Intentionally not caring if the specified revision belongs to this
        // page. We only care about the timestamp.
        $ts = $db->selectField( 'revision', 'rev_timestamp', [ 'rev_id' => $revId ], __METHOD__ );
        if ( $ts === false ) {
            $ts = $db->selectField( 'archive', 'ar_timestamp', [ 'ar_rev_id' => $revId ], __METHOD__ );
            if ( $ts === false ) {
                // Or should this throw an InvalidArgumentException or something?
                return false;
            }
        }
        $ts = $db->addQuotes( $ts );
 
        $revId = $db->selectField( 'revision', 'rev_id',
            [
                'rev_page' => $this->getArticleID( $flags ),
                "rev_timestamp $op $ts OR (rev_timestamp = $ts AND rev_id $op $revId)"
            ],
            __METHOD__,
            [
                'ORDER BY' => "rev_timestamp $sort, rev_id $sort",
                'IGNORE INDEX' => 'rev_timestamp', // Probably needed for T159319
            ]
        );
 
        if ( $revId === false ) {
            return false;
        } else {
            return intval( $revId );
        }
    }
 
    public function getPreviousRevisionID( $revId, $flags = 0 ) {
        return $this->getRelativeRevisionID( $revId, $flags, 'prev' );
    }
 
    public function getNextRevisionID( $revId, $flags = 0 ) {
        return $this->getRelativeRevisionID( $revId, $flags, 'next' );
    }
 
    public function getFirstRevision( $flags = 0 ) {
        $pageId = $this->getArticleID( $flags );
        if ( $pageId ) {
            $db = ( $flags & self::GAID_FOR_UPDATE ) ? wfGetDB( DB_MASTER ) : wfGetDB( DB_REPLICA );
            $row = $db->selectRow( 'revision', Revision::selectFields(),
                [ 'rev_page' => $pageId ],
                __METHOD__,
                [
                    'ORDER BY' => 'rev_timestamp ASC, rev_id ASC',
                    'IGNORE INDEX' => 'rev_timestamp', // See T159319
                ]
            );
            if ( $row ) {
                return new Revision( $row );
            }
        }
        return null;
    }
 
    public function getEarliestRevTime( $flags = 0 ) {
        $rev = $this->getFirstRevision( $flags );
        return $rev ? $rev->getTimestamp() : null;
    }
 
    public function isNewPage() {
        $dbr = wfGetDB( DB_REPLICA );
        return (bool)$dbr->selectField( 'page', 'page_is_new', $this->pageCond(), __METHOD__ );
    }
 
    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;
    }
 
    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;
    }
 
    public function countRevisionsBetween( $old, $new, $max = null ) {
        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
        }
        $dbr = wfGetDB( DB_REPLICA );
        $conds = [
            'rev_page' => $this->getArticleID(),
            'rev_timestamp > ' . $dbr->addQuotes( $dbr->timestamp( $old->getTimestamp() ) ),
            'rev_timestamp < ' . $dbr->addQuotes( $dbr->timestamp( $new->getTimestamp() ) )
        ];
        if ( $max !== null ) {
            return $dbr->selectRowCount( 'revision', '1',
                $conds,
                __METHOD__,
                [ 'LIMIT' => $max + 1 ] // extra to detect truncation
            );
        } else {
            return (int)$dbr->selectField( 'revision', 'count(*)', $conds, __METHOD__ );
        }
    }
 
    public function getAuthorsBetween( $old, $new, $limit, $options = [] ) {
        if ( !( $old instanceof Revision ) ) {
            $old = Revision::newFromTitle( $this, (int)$old );
        }
        if ( !( $new instanceof Revision ) ) {
            $new = Revision::newFromTitle( $this, (int)$new );
        }
        // XXX: what if Revision objects are passed in, but they don't refer to this title?
        // Add $old->getPage() != $new->getPage() || $old->getPage() != $this->getArticleID()
        // in the sanity check below?
        if ( !$old || !$new ) {
            return null; // nothing to compare
        }
        $authors = [];
        $old_cmp = '>';
        $new_cmp = '<';
        $options = (array)$options;
        if ( in_array( 'include_old', $options ) ) {
            $old_cmp = '>=';
        }
        if ( in_array( 'include_new', $options ) ) {
            $new_cmp = '<=';
        }
        if ( in_array( 'include_both', $options ) ) {
            $old_cmp = '>=';
            $new_cmp = '<=';
        }
        // No DB query needed if $old and $new are the same or successive revisions:
        if ( $old->getId() === $new->getId() ) {
            return ( $old_cmp === '>' && $new_cmp === '<' ) ?
                [] :
                [ $old->getUserText( Revision::RAW ) ];
        } elseif ( $old->getId() === $new->getParentId() ) {
            if ( $old_cmp === '>=' && $new_cmp === '<=' ) {
                $authors[] = $old->getUserText( Revision::RAW );
                if ( $old->getUserText( Revision::RAW ) != $new->getUserText( Revision::RAW ) ) {
                    $authors[] = $new->getUserText( Revision::RAW );
                }
            } elseif ( $old_cmp === '>=' ) {
                $authors[] = $old->getUserText( Revision::RAW );
            } elseif ( $new_cmp === '<=' ) {
                $authors[] = $new->getUserText( Revision::RAW );
            }
            return $authors;
        }
        $dbr = wfGetDB( DB_REPLICA );
        $res = $dbr->select( 'revision', 'DISTINCT rev_user_text',
            [
                'rev_page' => $this->getArticleID(),
                "rev_timestamp $old_cmp " . $dbr->addQuotes( $dbr->timestamp( $old->getTimestamp() ) ),
                "rev_timestamp $new_cmp " . $dbr->addQuotes( $dbr->timestamp( $new->getTimestamp() ) )
            ], __METHOD__,
            [ 'LIMIT' => $limit + 1 ] // add one so caller knows it was truncated
        );
        foreach ( $res as $row ) {
            $authors[] = $row->rev_user_text;
        }
        return $authors;
    }
 
    public function countAuthorsBetween( $old, $new, $limit, $options = [] ) {
        $authors = $this->getAuthorsBetween( $old, $new, $limit, $options );
        return $authors ? count( $authors ) : 0;
    }
 
    public function equals( Title $title ) {
        // Note: === is necessary for proper matching of number-like titles.
        return $this->getInterwiki() === $title->getInterwiki()
            && $this->getNamespace() == $title->getNamespace()
            && $this->getDBkey() === $title->getDBkey();
    }
 
    public function isSubpageOf( Title $title ) {
        return $this->getInterwiki() === $title->getInterwiki()
            && $this->getNamespace() == $title->getNamespace()
            && strpos( $this->getDBkey(), $title->getDBkey() . '/' ) === 0;
    }
 
    public function exists( $flags = 0 ) {
        $exists = $this->getArticleID( $flags ) != 0;
        Hooks::run( 'TitleExists', [ $this, &$exists ] );
        return $exists;
    }
 
    public function isAlwaysKnown() {
        $isKnown = null;
 
        Hooks::run( 'TitleIsAlwaysKnown', [ $this, &$isKnown ] );
 
        if ( !is_null( $isKnown ) ) {
            return $isKnown;
        }
 
        if ( $this->isExternal() ) {
            return true;  // any interwiki link might be viewable, for all we know
        }
 
        switch ( $this->mNamespace ) {
            case NS_MEDIA:
            case NS_FILE:
                // file exists, possibly in a foreign repo
                return (bool)wfFindFile( $this );
            case NS_SPECIAL:
                // valid special page
                return SpecialPageFactory::exists( $this->getDBkey() );
            case NS_MAIN:
                // selflink, possibly with fragment
                return $this->mDbkeyform == '';
            case NS_MEDIAWIKI:
                // known system message
                return $this->hasSourceText() !== false;
            default:
                return false;
        }
    }
 
    public function isKnown() {
        return $this->isAlwaysKnown() || $this->exists();
    }
 
    public function hasSourceText() {
        if ( $this->exists() ) {
            return true;
        }
 
        if ( $this->mNamespace == NS_MEDIAWIKI ) {
            // 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.
            global $wgContLang;
            list( $name, ) = MessageCache::singleton()->figureMessage(
                $wgContLang->lcfirst( $this->getText() )
            );
            $message = wfMessage( $name )->inLanguage( $wgContLang )->useDatabase( false );
            return $message->exists();
        }
 
        return false;
    }
 
    public function getDefaultMessageText() {
        global $wgContLang;
 
        if ( $this->getNamespace() != NS_MEDIAWIKI ) { // Just in case
            return false;
        }
 
        list( $name, $lang ) = MessageCache::singleton()->figureMessage(
            $wgContLang->lcfirst( $this->getText() )
        );
        $message = wfMessage( $name )->inLanguage( $lang )->useDatabase( false );
 
        if ( $message->exists() ) {
            return $message->plain();
        } else {
            return false;
        }
    }
 
    public function invalidateCache( $purgeTime = null ) {
        if ( wfReadOnly() ) {
            return false;
        } elseif ( $this->mArticleID === 0 ) {
            return true; // avoid gap locking if we know it's not there
        }
 
        $dbw = wfGetDB( DB_MASTER );
        $dbw->onTransactionPreCommitOrIdle( function () {
            ResourceLoaderWikiModule::invalidateModuleCache( $this, null, null, wfWikiID() );
        } );
 
        $conds = $this->pageCond();
        DeferredUpdates::addUpdate(
            new AutoCommitUpdate(
                $dbw,
                __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 );
                }
            ),
            DeferredUpdates::PRESEND
        );
 
        return true;
    }
 
    public function touchLinks() {
        DeferredUpdates::addUpdate( new HTMLCacheUpdate( $this, 'pagelinks' ) );
        if ( $this->getNamespace() == NS_CATEGORY ) {
            DeferredUpdates::addUpdate( new HTMLCacheUpdate( $this, 'categorylinks' ) );
        }
    }
 
    public function getTouched( $db = null ) {
        if ( $db === null ) {
            $db = wfGetDB( DB_REPLICA );
        }
        $touched = $db->selectField( 'page', 'page_touched', $this->pageCond(), __METHOD__ );
        return $touched;
    }
 
    public function getNotificationTimestamp( $user = null ) {
        global $wgUser;
 
        // Assume current user if none given
        if ( !$user ) {
            $user = $wgUser;
        }
        // Check cache first
        $uid = $user->getId();
        if ( !$uid ) {
            return false;
        }
        // avoid isset here, as it'll return false for null entries
        if ( array_key_exists( $uid, $this->mNotificationTimestamp ) ) {
            return $this->mNotificationTimestamp[$uid];
        }
        // Don't cache too much!
        if ( count( $this->mNotificationTimestamp ) >= self::CACHE_MAX ) {
            $this->mNotificationTimestamp = [];
        }
 
        $store = MediaWikiServices::getInstance()->getWatchedItemStore();
        $watchedItem = $store->getWatchedItem( $user, $this );
        if ( $watchedItem ) {
            $this->mNotificationTimestamp[$uid] = $watchedItem->getNotificationTimestamp();
        } else {
            $this->mNotificationTimestamp[$uid] = false;
        }
 
        return $this->mNotificationTimestamp[$uid];
    }
 
    public function getNamespaceKey( $prepend = 'nstab-' ) {
        global $wgContLang;
        // Gets the subject namespace if this title
        $namespace = MWNamespace::getSubject( $this->getNamespace() );
        // Checks if canonical namespace name exists for namespace
        if ( MWNamespace::exists( $this->getNamespace() ) ) {
            // Uses canonical namespace name
            $namespaceKey = MWNamespace::getCanonicalName( $namespace );
        } else {
            // Uses text of namespace
            $namespaceKey = $this->getSubjectNsText();
        }
        // Makes namespace key lowercase
        $namespaceKey = $wgContLang->lc( $namespaceKey );
        // Uses main
        if ( $namespaceKey == '' ) {
            $namespaceKey = 'main';
        }
        // Changes file to image for backwards compatibility
        if ( $namespaceKey == 'file' ) {
            $namespaceKey = 'image';
        }
        return $prepend . $namespaceKey;
    }
 
    public function getRedirectsHere( $ns = null ) {
        $redirs = [];
 
        $dbr = wfGetDB( DB_REPLICA );
        $where = [
            'rd_namespace' => $this->getNamespace(),
            'rd_title' => $this->getDBkey(),
            'rd_from = page_id'
        ];
        if ( $this->isExternal() ) {
            $where['rd_interwiki'] = $this->getInterwiki();
        } else {
            $where[] = 'rd_interwiki = ' . $dbr->addQuotes( '' ) . ' OR rd_interwiki IS NULL';
        }
        if ( !is_null( $ns ) ) {
            $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;
    }
 
    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;
    }
 
    public function getBacklinkCache() {
        return BacklinkCache::get( $this );
    }
 
    public function canUseNoindex() {
        global $wgExemptFromUserRobotsControl;
 
        $bannedNamespaces = is_null( $wgExemptFromUserRobotsControl )
            ? MWNamespace::getContentNamespaces()
            : $wgExemptFromUserRobotsControl;
 
        return !in_array( $this->mNamespace, $bannedNamespaces );
    }
 
    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::run( 'GetDefaultSortkey', [ $this, &$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;
    }
 
    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 = LinkCache::singleton();
            $linkCache->addLinkObj( $this );
            $this->mDbPageLanguage = $linkCache->getGoodLinkFieldObj( $this, 'lang' );
        }
 
        return $this->mDbPageLanguage;
    }
 
    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 = ContentHandler::getForTitle( $this );
            $langObj = $contentHandler->getPageLanguage( $this );
            $this->mPageLanguage = [ $langObj->getCode(), $wgLanguageCode ];
        } else {
            $langObj = wfGetLangObj( $this->mPageLanguage[0] );
        }
 
        return $langObj;
    }
 
    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 = $wgLang->getPreferredVariant();
            if ( $wgLang->getCode() !== $variant ) {
                return Language::factory( $variant );
            }
 
            return $wgLang;
        }
 
        // Checking if DB language is set
        $dbPageLanguage = $this->getDbPageLanguageCode();
        if ( $dbPageLanguage ) {
            $pageLang = wfGetLangObj( $dbPageLanguage );
            $variant = $pageLang->getPreferredVariant();
            if ( $pageLang->getCode() !== $variant ) {
                $pageLang = Language::factory( $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 = ContentHandler::getForTitle( $this );
        $pageLang = $contentHandler->getPageViewLanguage( $this );
        return $pageLang;
    }
 
    public function getEditNotices( $oldid = 0 ) {
        $notices = [];
 
        // Optional notice for the entire namespace
        $editnotice_ns = 'editnotice-' . $this->getNamespace();
        $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 ( MWNamespace::hasSubpages( $this->getNamespace() ) ) {
            // Optional notice for page itself and any parent page
            $parts = explode( '/', $this->getDBkey() );
            $editnotice_base = $editnotice_ns;
            while ( count( $parts ) > 0 ) {
                $editnotice_base .= '-' . array_shift( $parts );
                $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->getDBkey(), '/', '-' );
            $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::run( 'TitleGetEditNotices', [ $this, $oldid, &$notices ] );
        return $notices;
    }
 
    public function __sleep() {
        return [
            'mNamespace',
            'mDbkeyform',
            'mFragment',
            'mInterwiki',
            'mLocalInterwiki',
            'mUserCaseDBKey',
            'mDefaultNamespace',
        ];
    }
 
    public function __wakeup() {
        $this->mArticleID = ( $this->mNamespace >= 0 ) ? -1 : 0;
        $this->mUrlform = wfUrlencode( $this->mDbkeyform );
        $this->mTextform = strtr( $this->mDbkeyform, '_', ' ' );
    }
 
}