Merge "ForeignStructuredUpload: Stop using methods from CapsuleMultiselectWidget"

[lhc/web/wiklou.git] / includes / page / WikiPage.php

<?php
/**
 * Base representation for a MediaWiki page.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 */

use MediaWiki\Edit\PreparedEdit;
use MediaWiki\Logger\LoggerFactory;
use MediaWiki\MediaWikiServices;
use MediaWiki\Storage\DerivedPageDataUpdater;
use MediaWiki\Storage\PageUpdater;
use MediaWiki\Storage\RevisionRecord;
use MediaWiki\Storage\RevisionSlotsUpdate;
use MediaWiki\Storage\RevisionStore;
use Wikimedia\Assert\Assert;
use Wikimedia\Rdbms\FakeResultWrapper;
use Wikimedia\Rdbms\IDatabase;
use Wikimedia\Rdbms\LoadBalancer;

/**
 * Class representing a MediaWiki article and history.
 *
 * Some fields are public only for backwards-compatibility. Use accessors.
 * In the past, this class was part of Article.php and everything was public.
 */
class WikiPage implements Page, IDBAccessObject {
        // Constants for $mDataLoadedFrom and related

        /**
         * @var Title
         */
        public $mTitle = null;

        /**@{{
         * @protected
         */
        public $mDataLoaded = false;         // !< Boolean
        public $mIsRedirect = false;         // !< Boolean
        public $mLatest = false;             // !< Integer (false means "not loaded")
        /**@}}*/

        /** @var PreparedEdit Map of cache fields (text, parser output, ect) for a proposed/new edit */
        public $mPreparedEdit = false;

        /**
         * @var int
         */
        protected $mId = null;

        /**
         * @var int One of the READ_* constants
         */
        protected $mDataLoadedFrom = self::READ_NONE;

        /**
         * @var Title
         */
        protected $mRedirectTarget = null;

        /**
         * @var Revision
         */
        protected $mLastRevision = null;

        /**
         * @var string Timestamp of the current revision or empty string if not loaded
         */
        protected $mTimestamp = '';

        /**
         * @var string
         */
        protected $mTouched = '19700101000000';

        /**
         * @var string
         */
        protected $mLinksUpdated = '19700101000000';

        /**
         * @var DerivedPageDataUpdater|null
         */
        private $derivedDataUpdater = null;

        /**
         * Constructor and clear the article
         * @param Title $title Reference to a Title object.
         */
        public function __construct( Title $title ) {
                $this->mTitle = $title;
        }

        /**
         * Makes sure that the mTitle object is cloned
         * to the newly cloned WikiPage.
         */
        public function __clone() {
                $this->mTitle = clone $this->mTitle;
        }

        /**
         * Create a WikiPage object of the appropriate class for the given title.
         *
         * @param Title $title
         *
         * @throws MWException
         * @return WikiPage|WikiCategoryPage|WikiFilePage
         */
        public static function factory( Title $title ) {
                $ns = $title->getNamespace();

                if ( $ns == NS_MEDIA ) {
                        throw new MWException( "NS_MEDIA is a virtual namespace; use NS_FILE." );
                } elseif ( $ns < 0 ) {
                        throw new MWException( "Invalid or virtual namespace $ns given." );
                }

                $page = null;
                if ( !Hooks::run( 'WikiPageFactory', [ $title, &$page ] ) ) {
                        return $page;
                }

                switch ( $ns ) {
                        case NS_FILE:
                                $page = new WikiFilePage( $title );
                                break;
                        case NS_CATEGORY:
                                $page = new WikiCategoryPage( $title );
                                break;
                        default:
                                $page = new WikiPage( $title );
                }

                return $page;
        }

        /**
         * Constructor from a page id
         *
         * @param int $id Article ID to load
         * @param string|int $from One of the following values:
         *        - "fromdb" or WikiPage::READ_NORMAL to select from a replica DB
         *        - "fromdbmaster" or WikiPage::READ_LATEST to select from the master database
         *
         * @return WikiPage|null
         */
        public static function newFromID( $id, $from = 'fromdb' ) {
                // page ids are never 0 or negative, see T63166
                if ( $id < 1 ) {
                        return null;
                }

                $from = self::convertSelectType( $from );
                $db = wfGetDB( $from === self::READ_LATEST ? DB_MASTER : DB_REPLICA );
                $pageQuery = self::getQueryInfo();
                $row = $db->selectRow(
                        $pageQuery['tables'], $pageQuery['fields'], [ 'page_id' => $id ], __METHOD__,
                        [], $pageQuery['joins']
                );
                if ( !$row ) {
                        return null;
                }
                return self::newFromRow( $row, $from );
        }

        /**
         * Constructor from a database row
         *
         * @since 1.20
         * @param object $row Database row containing at least fields returned by selectFields().
         * @param string|int $from Source of $data:
         *        - "fromdb" or WikiPage::READ_NORMAL: from a replica DB
         *        - "fromdbmaster" or WikiPage::READ_LATEST: from the master DB
         *        - "forupdate" or WikiPage::READ_LOCKING: from the master DB using SELECT FOR UPDATE
         * @return WikiPage
         */
        public static function newFromRow( $row, $from = 'fromdb' ) {
                $page = self::factory( Title::newFromRow( $row ) );
                $page->loadFromRow( $row, $from );
                return $page;
        }

        /**
         * Convert 'fromdb', 'fromdbmaster' and 'forupdate' to READ_* constants.
         *
         * @param object|string|int $type
         * @return mixed
         */
        protected static function convertSelectType( $type ) {
                switch ( $type ) {
                        case 'fromdb':
                                return self::READ_NORMAL;
                        case 'fromdbmaster':
                                return self::READ_LATEST;
                        case 'forupdate':
                                return self::READ_LOCKING;
                        default:
                                // It may already be an integer or whatever else
                                return $type;
                }
        }

        /**
         * @return RevisionStore
         */
        private function getRevisionStore() {
                return MediaWikiServices::getInstance()->getRevisionStore();
        }

        /**
         * @return ParserCache
         */
        private function getParserCache() {
                return MediaWikiServices::getInstance()->getParserCache();
        }

        /**
         * @return LoadBalancer
         */
        private function getDBLoadBalancer() {
                return MediaWikiServices::getInstance()->getDBLoadBalancer();
        }

        /**
         * @todo Move this UI stuff somewhere else
         *
         * @see ContentHandler::getActionOverrides
         * @return array
         */
        public function getActionOverrides() {
                return $this->getContentHandler()->getActionOverrides();
        }

        /**
         * Returns the ContentHandler instance to be used to deal with the content of this WikiPage.
         *
         * Shorthand for ContentHandler::getForModelID( $this->getContentModel() );
         *
         * @return ContentHandler
         *
         * @since 1.21
         */
        public function getContentHandler() {
                return ContentHandler::getForModelID( $this->getContentModel() );
        }

        /**
         * Get the title object of the article
         * @return Title Title object of this page
         */
        public function getTitle() {
                return $this->mTitle;
        }

        /**
         * Clear the object
         * @return void
         */
        public function clear() {
                $this->mDataLoaded = false;
                $this->mDataLoadedFrom = self::READ_NONE;

                $this->clearCacheFields();
        }

        /**
         * Clear the object cache fields
         * @return void
         */
        protected function clearCacheFields() {
                $this->mId = null;
                $this->mRedirectTarget = null; // Title object if set
                $this->mLastRevision = null; // Latest revision
                $this->mTouched = '19700101000000';
                $this->mLinksUpdated = '19700101000000';
                $this->mTimestamp = '';
                $this->mIsRedirect = false;
                $this->mLatest = false;
                // T59026: do not clear $this->derivedDataUpdater since getDerivedDataUpdater() already
                // checks the requested rev ID and content against the cached one. For most
                // content types, the output should not change during the lifetime of this cache.
                // Clearing it can cause extra parses on edit for no reason.
        }

        /**
         * Clear the mPreparedEdit cache field, as may be needed by mutable content types
         * @return void
         * @since 1.23
         */
        public function clearPreparedEdit() {
                $this->mPreparedEdit = false;
        }

        /**
         * Return the list of revision fields that should be selected to create
         * a new page.
         *
         * @deprecated since 1.31, use self::getQueryInfo() instead.
         * @return array
         */
        public static function selectFields() {
                global $wgContentHandlerUseDB, $wgPageLanguageUseDB;

                wfDeprecated( __METHOD__, '1.31' );

                $fields = [
                        'page_id',
                        'page_namespace',
                        'page_title',
                        'page_restrictions',
                        'page_is_redirect',
                        'page_is_new',
                        'page_random',
                        'page_touched',
                        'page_links_updated',
                        'page_latest',
                        'page_len',
                ];

                if ( $wgContentHandlerUseDB ) {
                        $fields[] = 'page_content_model';
                }

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

                return $fields;
        }

        /**
         * Return the tables, fields, and join conditions to be selected to create
         * a new page object.
         * @since 1.31
         * @return array With three keys:
         *   - tables: (string[]) to include in the `$table` to `IDatabase->select()`
         *   - fields: (string[]) to include in the `$vars` to `IDatabase->select()`
         *   - joins: (array) to include in the `$join_conds` to `IDatabase->select()`
         */
        public static function getQueryInfo() {
                global $wgContentHandlerUseDB, $wgPageLanguageUseDB;

                $ret = [
                        'tables' => [ 'page' ],
                        'fields' => [
                                'page_id',
                                'page_namespace',
                                'page_title',
                                'page_restrictions',
                                'page_is_redirect',
                                'page_is_new',
                                'page_random',
                                'page_touched',
                                'page_links_updated',
                                'page_latest',
                                'page_len',
                        ],
                        'joins' => [],
                ];

                if ( $wgContentHandlerUseDB ) {
                        $ret['fields'][] = 'page_content_model';
                }

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

                return $ret;
        }

        /**
         * Fetch a page record with the given conditions
         * @param IDatabase $dbr
         * @param array $conditions
         * @param array $options
         * @return object|bool Database result resource, or false on failure
         */
        protected function pageData( $dbr, $conditions, $options = [] ) {
                $pageQuery = self::getQueryInfo();

                // Avoid PHP 7.1 warning of passing $this by reference
                $wikiPage = $this;

                Hooks::run( 'ArticlePageDataBefore', [
                        &$wikiPage, &$pageQuery['fields'], &$pageQuery['tables'], &$pageQuery['joins']
                ] );

                $row = $dbr->selectRow(
                        $pageQuery['tables'],
                        $pageQuery['fields'],
                        $conditions,
                        __METHOD__,
                        $options,
                        $pageQuery['joins']
                );

                Hooks::run( 'ArticlePageDataAfter', [ &$wikiPage, &$row ] );

                return $row;
        }

        /**
         * Fetch a page record matching the Title object's namespace and title
         * using a sanitized title string
         *
         * @param IDatabase $dbr
         * @param Title $title
         * @param array $options
         * @return object|bool Database result resource, or false on failure
         */
        public function pageDataFromTitle( $dbr, $title, $options = [] ) {
                return $this->pageData( $dbr, [
                        'page_namespace' => $title->getNamespace(),
                        'page_title' => $title->getDBkey() ], $options );
        }

        /**
         * Fetch a page record matching the requested ID
         *
         * @param IDatabase $dbr
         * @param int $id
         * @param array $options
         * @return object|bool Database result resource, or false on failure
         */
        public function pageDataFromId( $dbr, $id, $options = [] ) {
                return $this->pageData( $dbr, [ 'page_id' => $id ], $options );
        }

        /**
         * Load the object from a given source by title
         *
         * @param object|string|int $from One of the following:
         *   - A DB query result object.
         *   - "fromdb" or WikiPage::READ_NORMAL to get from a replica DB.
         *   - "fromdbmaster" or WikiPage::READ_LATEST to get from the master DB.
         *   - "forupdate"  or WikiPage::READ_LOCKING to get from the master DB
         *     using SELECT FOR UPDATE.
         *
         * @return void
         */
        public function loadPageData( $from = 'fromdb' ) {
                $from = self::convertSelectType( $from );
                if ( is_int( $from ) && $from <= $this->mDataLoadedFrom ) {
                        // We already have the data from the correct location, no need to load it twice.
                        return;
                }

                if ( is_int( $from ) ) {
                        list( $index, $opts ) = DBAccessObjectUtils::getDBOptions( $from );
                        $loadBalancer = $this->getDBLoadBalancer();
                        $db = $loadBalancer->getConnection( $index );
                        $data = $this->pageDataFromTitle( $db, $this->mTitle, $opts );

                        if ( !$data
                                && $index == DB_REPLICA
                                && $loadBalancer->getServerCount() > 1
                                && $loadBalancer->hasOrMadeRecentMasterChanges()
                        ) {
                                $from = self::READ_LATEST;
                                list( $index, $opts ) = DBAccessObjectUtils::getDBOptions( $from );
                                $db = $loadBalancer->getConnection( $index );
                                $data = $this->pageDataFromTitle( $db, $this->mTitle, $opts );
                        }
                } else {
                        // No idea from where the caller got this data, assume replica DB.
                        $data = $from;
                        $from = self::READ_NORMAL;
                }

                $this->loadFromRow( $data, $from );
        }

        /**
         * Checks whether the page data was loaded using the given database access mode (or better).
         *
         * @since 1.32
         *
         * @param string|int $from One of the following:
         *   - "fromdb" or WikiPage::READ_NORMAL to get from a replica DB.
         *   - "fromdbmaster" or WikiPage::READ_LATEST to get from the master DB.
         *   - "forupdate"  or WikiPage::READ_LOCKING to get from the master DB
         *     using SELECT FOR UPDATE.
         *
         * @return bool
         */
        public function wasLoadedFrom( $from ) {
                $from = self::convertSelectType( $from );

                if ( !is_int( $from ) ) {
                        // No idea from where the caller got this data, assume replica DB.
                        $from = self::READ_NORMAL;
                }

                if ( is_int( $from ) && $from <= $this->mDataLoadedFrom ) {
                        return true;
                }

                return false;
        }

        /**
         * Load the object from a database row
         *
         * @since 1.20
         * @param object|bool $data DB row containing fields returned by selectFields() or false
         * @param string|int $from One of the following:
         *        - "fromdb" or WikiPage::READ_NORMAL if the data comes from a replica DB
         *        - "fromdbmaster" or WikiPage::READ_LATEST if the data comes from the master DB
         *        - "forupdate"  or WikiPage::READ_LOCKING if the data comes from
         *          the master DB using SELECT FOR UPDATE
         */
        public function loadFromRow( $data, $from ) {
                $lc = MediaWikiServices::getInstance()->getLinkCache();
                $lc->clearLink( $this->mTitle );

                if ( $data ) {
                        $lc->addGoodLinkObjFromRow( $this->mTitle, $data );

                        $this->mTitle->loadFromRow( $data );

                        // Old-fashioned restrictions
                        $this->mTitle->loadRestrictions( $data->page_restrictions );

                        $this->mId = intval( $data->page_id );
                        $this->mTouched = wfTimestamp( TS_MW, $data->page_touched );
                        $this->mLinksUpdated = wfTimestampOrNull( TS_MW, $data->page_links_updated );
                        $this->mIsRedirect = intval( $data->page_is_redirect );
                        $this->mLatest = intval( $data->page_latest );
                        // T39225: $latest may no longer match the cached latest Revision object.
                        // Double-check the ID of any cached latest Revision object for consistency.
                        if ( $this->mLastRevision && $this->mLastRevision->getId() != $this->mLatest ) {
                                $this->mLastRevision = null;
                                $this->mTimestamp = '';
                        }
                } else {
                        $lc->addBadLinkObj( $this->mTitle );

                        $this->mTitle->loadFromRow( false );

                        $this->clearCacheFields();

                        $this->mId = 0;
                }

                $this->mDataLoaded = true;
                $this->mDataLoadedFrom = self::convertSelectType( $from );
        }

        /**
         * @return int Page ID
         */
        public function getId() {
                if ( !$this->mDataLoaded ) {
                        $this->loadPageData();
                }
                return $this->mId;
        }

        /**
         * @return bool Whether or not the page exists in the database
         */
        public function exists() {
                if ( !$this->mDataLoaded ) {
                        $this->loadPageData();
                }
                return $this->mId > 0;
        }

        /**
         * Check if this page is something we're going to be showing
         * some sort of sensible content for. If we return false, page
         * views (plain action=view) will return an HTTP 404 response,
         * so spiders and robots can know they're following a bad link.
         *
         * @return bool
         */
        public function hasViewableContent() {
                return $this->mTitle->isKnown();
        }

        /**
         * Tests if the article content represents a redirect
         *
         * @return bool
         */
        public function isRedirect() {
                if ( !$this->mDataLoaded ) {
                        $this->loadPageData();
                }

                return (bool)$this->mIsRedirect;
        }

        /**
         * Returns the page's content model id (see the CONTENT_MODEL_XXX constants).
         *
         * Will use the revisions actual content model if the page exists,
         * and the page's default if the page doesn't exist yet.
         *
         * @return string
         *
         * @since 1.21
         */
        public function getContentModel() {
                if ( $this->exists() ) {
                        $cache = ObjectCache::getMainWANInstance();

                        return $cache->getWithSetCallback(
                                $cache->makeKey( 'page-content-model', $this->getLatest() ),
                                $cache::TTL_MONTH,
                                function () {
                                        $rev = $this->getRevision();
                                        if ( $rev ) {
                                                // Look at the revision's actual content model
                                                return $rev->getContentModel();
                                        } else {
                                                $title = $this->mTitle->getPrefixedDBkey();
                                                wfWarn( "Page $title exists but has no (visible) revisions!" );
                                                return $this->mTitle->getContentModel();
                                        }
                                }
                        );
                }

                // use the default model for this page
                return $this->mTitle->getContentModel();
        }

        /**
         * Loads page_touched and returns a value indicating if it should be used
         * @return bool True if this page exists and is not a redirect
         */
        public function checkTouched() {
                if ( !$this->mDataLoaded ) {
                        $this->loadPageData();
                }
                return ( $this->mId && !$this->mIsRedirect );
        }

        /**
         * Get the page_touched field
         * @return string Containing GMT timestamp
         */
        public function getTouched() {
                if ( !$this->mDataLoaded ) {
                        $this->loadPageData();
                }
                return $this->mTouched;
        }

        /**
         * Get the page_links_updated field
         * @return string|null Containing GMT timestamp
         */
        public function getLinksTimestamp() {
                if ( !$this->mDataLoaded ) {
                        $this->loadPageData();
                }
                return $this->mLinksUpdated;
        }

        /**
         * Get the page_latest field
         * @return int The rev_id of current revision
         */
        public function getLatest() {
                if ( !$this->mDataLoaded ) {
                        $this->loadPageData();
                }
                return (int)$this->mLatest;
        }

        /**
         * Get the Revision object of the oldest revision
         * @return Revision|null
         */
        public function getOldestRevision() {
                // Try using the replica DB first, then try the master
                $rev = $this->mTitle->getFirstRevision();
                if ( !$rev ) {
                        $rev = $this->mTitle->getFirstRevision( Title::GAID_FOR_UPDATE );
                }
                return $rev;
        }

        /**
         * Loads everything except the text
         * This isn't necessary for all uses, so it's only done if needed.
         */
        protected function loadLastEdit() {
                if ( $this->mLastRevision !== null ) {
                        return; // already loaded
                }

                $latest = $this->getLatest();
                if ( !$latest ) {
                        return; // page doesn't exist or is missing page_latest info
                }

                if ( $this->mDataLoadedFrom == self::READ_LOCKING ) {
                        // T39225: if session S1 loads the page row FOR UPDATE, the result always
                        // includes the latest changes committed. This is true even within REPEATABLE-READ
                        // transactions, where S1 normally only sees changes committed before the first S1
                        // SELECT. Thus we need S1 to also gets the revision row FOR UPDATE; otherwise, it
                        // may not find it since a page row UPDATE and revision row INSERT by S2 may have
                        // happened after the first S1 SELECT.
                        // https://dev.mysql.com/doc/refman/5.0/en/set-transaction.html#isolevel_repeatable-read
                        $flags = Revision::READ_LOCKING;
                        $revision = Revision::newFromPageId( $this->getId(), $latest, $flags );
                } elseif ( $this->mDataLoadedFrom == self::READ_LATEST ) {
                        // Bug T93976: if page_latest was loaded from the master, fetch the
                        // revision from there as well, as it may not exist yet on a replica DB.
                        // Also, this keeps the queries in the same REPEATABLE-READ snapshot.
                        $flags = Revision::READ_LATEST;
                        $revision = Revision::newFromPageId( $this->getId(), $latest, $flags );
                } else {
                        $dbr = wfGetDB( DB_REPLICA );
                        $revision = Revision::newKnownCurrent( $dbr, $this->getTitle(), $latest );
                }

                if ( $revision ) { // sanity
                        $this->setLastEdit( $revision );
                }
        }

        /**
         * Set the latest revision
         * @param Revision $revision
         */
        protected function setLastEdit( Revision $revision ) {
                $this->mLastRevision = $revision;
                $this->mTimestamp = $revision->getTimestamp();
        }

        /**
         * Get the latest revision
         * @return Revision|null
         */
        public function getRevision() {
                $this->loadLastEdit();
                if ( $this->mLastRevision ) {
                        return $this->mLastRevision;
                }
                return null;
        }

        /**
         * Get the content of the current revision. No side-effects...
         *
         * @param int $audience One of:
         *   Revision::FOR_PUBLIC       to be displayed to all users
         *   Revision::FOR_THIS_USER    to be displayed to $wgUser
         *   Revision::RAW              get the text regardless of permissions
         * @param User $user User object to check for, only if FOR_THIS_USER is passed
         *   to the $audience parameter
         * @return Content|null The content of the current revision
         *
         * @since 1.21
         */
        public function getContent( $audience = Revision::FOR_PUBLIC, User $user = null ) {
                $this->loadLastEdit();
                if ( $this->mLastRevision ) {
                        return $this->mLastRevision->getContent( $audience, $user );
                }
                return null;
        }

        /**
         * @return string MW timestamp of last article revision
         */
        public function getTimestamp() {
                // Check if the field has been filled by WikiPage::setTimestamp()
                if ( !$this->mTimestamp ) {
                        $this->loadLastEdit();
                }

                return wfTimestamp( TS_MW, $this->mTimestamp );
        }

        /**
         * Set the page timestamp (use only to avoid DB queries)
         * @param string $ts MW timestamp of last article revision
         * @return void
         */
        public function setTimestamp( $ts ) {
                $this->mTimestamp = wfTimestamp( TS_MW, $ts );
        }

        /**
         * @param int $audience One of:
         *   Revision::FOR_PUBLIC       to be displayed to all users
         *   Revision::FOR_THIS_USER    to be displayed to the given user
         *   Revision::RAW              get the text regardless of permissions
         * @param User $user User object to check for, only if FOR_THIS_USER is passed
         *   to the $audience parameter
         * @return int User ID for the user that made the last article revision
         */
        public function getUser( $audience = Revision::FOR_PUBLIC, User $user = null ) {
                $this->loadLastEdit();
                if ( $this->mLastRevision ) {
                        return $this->mLastRevision->getUser( $audience, $user );
                } else {
                        return -1;
                }
        }

        /**
         * Get the User object of the user who created the page
         * @param int $audience One of:
         *   Revision::FOR_PUBLIC       to be displayed to all users
         *   Revision::FOR_THIS_USER    to be displayed to the given user
         *   Revision::RAW              get the text regardless of permissions
         * @param User $user User object to check for, only if FOR_THIS_USER is passed
         *   to the $audience parameter
         * @return User|null
         */
        public function getCreator( $audience = Revision::FOR_PUBLIC, User $user = null ) {
                $revision = $this->getOldestRevision();
                if ( $revision ) {
                        $userName = $revision->getUserText( $audience, $user );
                        return User::newFromName( $userName, false );
                } else {
                        return null;
                }
        }

        /**
         * @param int $audience One of:
         *   Revision::FOR_PUBLIC       to be displayed to all users
         *   Revision::FOR_THIS_USER    to be displayed to the given user
         *   Revision::RAW              get the text regardless of permissions
         * @param User $user User object to check for, only if FOR_THIS_USER is passed
         *   to the $audience parameter
         * @return string Username of the user that made the last article revision
         */
        public function getUserText( $audience = Revision::FOR_PUBLIC, User $user = null ) {
                $this->loadLastEdit();
                if ( $this->mLastRevision ) {
                        return $this->mLastRevision->getUserText( $audience, $user );
                } else {
                        return '';
                }
        }

        /**
         * @param int $audience One of:
         *   Revision::FOR_PUBLIC       to be displayed to all users
         *   Revision::FOR_THIS_USER    to be displayed to the given user
         *   Revision::RAW              get the text regardless of permissions
         * @param User $user User object to check for, only if FOR_THIS_USER is passed
         *   to the $audience parameter
         * @return string Comment stored for the last article revision
         */
        public function getComment( $audience = Revision::FOR_PUBLIC, User $user = null ) {
                $this->loadLastEdit();
                if ( $this->mLastRevision ) {
                        return $this->mLastRevision->getComment( $audience, $user );
                } else {
                        return '';
                }
        }

        /**
         * Returns true if last revision was marked as "minor edit"
         *
         * @return bool Minor edit indicator for the last article revision.
         */
        public function getMinorEdit() {
                $this->loadLastEdit();
                if ( $this->mLastRevision ) {
                        return $this->mLastRevision->isMinor();
                } else {
                        return false;
                }
        }

        /**
         * Determine whether a page would be suitable for being counted as an
         * article in the site_stats table based on the title & its content
         *
         * @param PreparedEdit|bool $editInfo (false): object returned by prepareTextForEdit(),
         *   if false, the current database state will be used
         * @return bool
         */
        public function isCountable( $editInfo = false ) {
                global $wgArticleCountMethod;

                // NOTE: Keep in sync with DerivedPageDataUpdater::isCountable.

                if ( !$this->mTitle->isContentPage() ) {
                        return false;
                }

                if ( $editInfo ) {
                        // NOTE: only the main slot can make a page a redirect
                        $content = $editInfo->pstContent;
                } else {
                        $content = $this->getContent();
                }

                if ( !$content || $content->isRedirect() ) {
                        return false;
                }

                $hasLinks = null;

                if ( $wgArticleCountMethod === 'link' ) {
                        // nasty special case to avoid re-parsing to detect links

                        if ( $editInfo ) {
                                // ParserOutput::getLinks() is a 2D array of page links, so
                                // to be really correct we would need to recurse in the array
                                // but the main array should only have items in it if there are
                                // links.
                                $hasLinks = (bool)count( $editInfo->output->getLinks() );
                        } else {
                                $hasLinks = (bool)wfGetDB( DB_REPLICA )->selectField( 'pagelinks', 1,
                                        [ 'pl_from' => $this->getId() ], __METHOD__ );
                        }
                }

                return $content->isCountable( $hasLinks );
        }

        /**
         * If this page is a redirect, get its target
         *
         * The target will be fetched from the redirect table if possible.
         * If this page doesn't have an entry there, call insertRedirect()
         * @return Title|null Title object, or null if this page is not a redirect
         */
        public function getRedirectTarget() {
                if ( !$this->mTitle->isRedirect() ) {
                        return null;
                }

                if ( $this->mRedirectTarget !== null ) {
                        return $this->mRedirectTarget;
                }

                // Query the redirect table
                $dbr = wfGetDB( DB_REPLICA );
                $row = $dbr->selectRow( 'redirect',
                        [ 'rd_namespace', 'rd_title', 'rd_fragment', 'rd_interwiki' ],
                        [ 'rd_from' => $this->getId() ],
                        __METHOD__
                );

                // rd_fragment and rd_interwiki were added later, populate them if empty
                if ( $row && !is_null( $row->rd_fragment ) && !is_null( $row->rd_interwiki ) ) {
                        $this->mRedirectTarget = Title::makeTitle(
                                $row->rd_namespace, $row->rd_title,
                                $row->rd_fragment, $row->rd_interwiki
                        );
                        return $this->mRedirectTarget;
                }

                // This page doesn't have an entry in the redirect table
                $this->mRedirectTarget = $this->insertRedirect();
                return $this->mRedirectTarget;
        }

        /**
         * Insert an entry for this page into the redirect table if the content is a redirect
         *
         * The database update will be deferred via DeferredUpdates
         *
         * Don't call this function directly unless you know what you're doing.
         * @return Title|null Title object or null if not a redirect
         */
        public function insertRedirect() {
                $content = $this->getContent();
                $retval = $content ? $content->getUltimateRedirectTarget() : null;
                if ( !$retval ) {
                        return null;
                }

                // Update the DB post-send if the page has not cached since now
                $latest = $this->getLatest();
                DeferredUpdates::addCallableUpdate(
                        function () use ( $retval, $latest ) {
                                $this->insertRedirectEntry( $retval, $latest );
                        },
                        DeferredUpdates::POSTSEND,
                        wfGetDB( DB_MASTER )
                );

                return $retval;
        }

        /**
         * Insert or update the redirect table entry for this page to indicate it redirects to $rt
         * @param Title $rt Redirect target
         * @param int|null $oldLatest Prior page_latest for check and set
         */
        public function insertRedirectEntry( Title $rt, $oldLatest = null ) {
                $dbw = wfGetDB( DB_MASTER );
                $dbw->startAtomic( __METHOD__ );

                if ( !$oldLatest || $oldLatest == $this->lockAndGetLatest() ) {
                        $dbw->upsert(
                                'redirect',
                                [
                                        'rd_from' => $this->getId(),
                                        'rd_namespace' => $rt->getNamespace(),
                                        'rd_title' => $rt->getDBkey(),
                                        'rd_fragment' => $rt->getFragment(),
                                        'rd_interwiki' => $rt->getInterwiki(),
                                ],
                                [ 'rd_from' ],
                                [
                                        'rd_namespace' => $rt->getNamespace(),
                                        'rd_title' => $rt->getDBkey(),
                                        'rd_fragment' => $rt->getFragment(),
                                        'rd_interwiki' => $rt->getInterwiki(),
                                ],
                                __METHOD__
                        );
                }

                $dbw->endAtomic( __METHOD__ );
        }

        /**
         * Get the Title object or URL this page redirects to
         *
         * @return bool|Title|string False, Title of in-wiki target, or string with URL
         */
        public function followRedirect() {
                return $this->getRedirectURL( $this->getRedirectTarget() );
        }

        /**
         * Get the Title object or URL to use for a redirect. We use Title
         * objects for same-wiki, non-special redirects and URLs for everything
         * else.
         * @param Title $rt Redirect target
         * @return bool|Title|string False, Title object of local target, or string with URL
         */
        public function getRedirectURL( $rt ) {
                if ( !$rt ) {
                        return false;
                }

                if ( $rt->isExternal() ) {
                        if ( $rt->isLocal() ) {
                                // Offsite wikis need an HTTP redirect.
                                // This can be hard to reverse and may produce loops,
                                // so they may be disabled in the site configuration.
                                $source = $this->mTitle->getFullURL( 'redirect=no' );
                                return $rt->getFullURL( [ 'rdfrom' => $source ] );
                        } else {
                                // External pages without "local" bit set are not valid
                                // redirect targets
                                return false;
                        }
                }

                if ( $rt->isSpecialPage() ) {
                        // Gotta handle redirects to special pages differently:
                        // Fill the HTTP response "Location" header and ignore the rest of the page we're on.
                        // Some pages are not valid targets.
                        if ( $rt->isValidRedirectTarget() ) {
                                return $rt->getFullURL();
                        } else {
                                return false;
                        }
                }

                return $rt;
        }

        /**
         * Get a list of users who have edited this article, not including the user who made
         * the most recent revision, which you can get from $article->getUser() if you want it
         * @return UserArrayFromResult
         */
        public function getContributors() {
                // @todo: This is expensive; cache this info somewhere.

                $dbr = wfGetDB( DB_REPLICA );

                $actorMigration = ActorMigration::newMigration();
                $actorQuery = $actorMigration->getJoin( 'rev_user' );

                $tables = array_merge( [ 'revision' ], $actorQuery['tables'], [ 'user' ] );

                $fields = [
                        'user_id' => $actorQuery['fields']['rev_user'],
                        'user_name' => $actorQuery['fields']['rev_user_text'],
                        'actor_id' => $actorQuery['fields']['rev_actor'],
                        'user_real_name' => 'MIN(user_real_name)',
                        'timestamp' => 'MAX(rev_timestamp)',
                ];

                $conds = [ 'rev_page' => $this->getId() ];

                // The user who made the top revision gets credited as "this page was last edited by
                // John, based on contributions by Tom, Dick and Harry", so don't include them twice.
                $user = $this->getUser()
                        ? User::newFromId( $this->getUser() )
                        : User::newFromName( $this->getUserText(), false );
                $conds[] = 'NOT(' . $actorMigration->getWhere( $dbr, 'rev_user', $user )['conds'] . ')';

                // Username hidden?
                $conds[] = "{$dbr->bitAnd( 'rev_deleted', Revision::DELETED_USER )} = 0";

                $jconds = [
                        'user' => [ 'LEFT JOIN', $actorQuery['fields']['rev_user'] . ' = user_id' ],
                ] + $actorQuery['joins'];

                $options = [
                        'GROUP BY' => [ $fields['user_id'], $fields['user_name'] ],
                        'ORDER BY' => 'timestamp DESC',
                ];

                $res = $dbr->select( $tables, $fields, $conds, __METHOD__, $options, $jconds );
                return new UserArrayFromResult( $res );
        }

        /**
         * Should the parser cache be used?
         *
         * @param ParserOptions $parserOptions ParserOptions to check
         * @param int $oldId
         * @return bool
         */
        public function shouldCheckParserCache( ParserOptions $parserOptions, $oldId ) {
                return $parserOptions->getStubThreshold() == 0
                        && $this->exists()
                        && ( $oldId === null || $oldId === 0 || $oldId === $this->getLatest() )
                        && $this->getContentHandler()->isParserCacheSupported();
        }

        /**
         * Get a ParserOutput for the given ParserOptions and revision ID.
         *
         * The parser cache will be used if possible. Cache misses that result
         * in parser runs are debounced with PoolCounter.
         *
         * @since 1.19
         * @param ParserOptions $parserOptions ParserOptions to use for the parse operation
         * @param null|int $oldid Revision ID to get the text from, passing null or 0 will
         *   get the current revision (default value)
         * @param bool $forceParse Force reindexing, regardless of cache settings
         * @return bool|ParserOutput ParserOutput or false if the revision was not found
         */
        public function getParserOutput(
                ParserOptions $parserOptions, $oldid = null, $forceParse = false
        ) {
                $useParserCache =
                        ( !$forceParse ) && $this->shouldCheckParserCache( $parserOptions, $oldid );

                if ( $useParserCache && !$parserOptions->isSafeToCache() ) {
                        throw new InvalidArgumentException(
                                'The supplied ParserOptions are not safe to cache. Fix the options or set $forceParse = true.'
                        );
                }

                wfDebug( __METHOD__ .
                        ': using parser cache: ' . ( $useParserCache ? 'yes' : 'no' ) . "\n" );
                if ( $parserOptions->getStubThreshold() ) {
                        wfIncrStats( 'pcache.miss.stub' );
                }

                if ( $useParserCache ) {
                        $parserOutput = $this->getParserCache()
                                ->get( $this, $parserOptions );
                        if ( $parserOutput !== false ) {
                                return $parserOutput;
                        }
                }

                if ( $oldid === null || $oldid === 0 ) {
                        $oldid = $this->getLatest();
                }

                $pool = new PoolWorkArticleView( $this, $parserOptions, $oldid, $useParserCache );
                $pool->execute();

                return $pool->getParserOutput();
        }

        /**
         * Do standard deferred updates after page view (existing or missing page)
         * @param User $user The relevant user
         * @param int $oldid Revision id being viewed; if not given or 0, latest revision is assumed
         */
        public function doViewUpdates( User $user, $oldid = 0 ) {
                if ( wfReadOnly() ) {
                        return;
                }

                // Update newtalk / watchlist notification status;
                // Avoid outage if the master is not reachable by using a deferred updated
                DeferredUpdates::addCallableUpdate(
                        function () use ( $user, $oldid ) {
                                Hooks::run( 'PageViewUpdates', [ $this, $user ] );

                                $user->clearNotification( $this->mTitle, $oldid );
                        },
                        DeferredUpdates::PRESEND
                );
        }

        /**
         * Perform the actions of a page purging
         * @return bool
         * @note In 1.28 (and only 1.28), this took a $flags parameter that
         *  controlled how much purging was done.
         */
        public function doPurge() {
                // Avoid PHP 7.1 warning of passing $this by reference
                $wikiPage = $this;

                if ( !Hooks::run( 'ArticlePurge', [ &$wikiPage ] ) ) {
                        return false;
                }

                $this->mTitle->invalidateCache();

                // Clear file cache
                HTMLFileCache::clearFileCache( $this->getTitle() );
                // Send purge after above page_touched update was committed
                DeferredUpdates::addUpdate(
                        new CdnCacheUpdate( $this->mTitle->getCdnUrls() ),
                        DeferredUpdates::PRESEND
                );

                if ( $this->mTitle->getNamespace() == NS_MEDIAWIKI ) {
                        $messageCache = MessageCache::singleton();
                        $messageCache->updateMessageOverride( $this->mTitle, $this->getContent() );
                }

                return true;
        }

        /**
         * Insert a new empty page record for this article.
         * This *must* be followed up by creating a revision
         * and running $this->updateRevisionOn( ... );
         * or else the record will be left in a funky state.
         * Best if all done inside a transaction.
         *
         * @todo Factor out into a PageStore service, to be used by PageUpdater.
         *
         * @param IDatabase $dbw
         * @param int|null $pageId Custom page ID that will be used for the insert statement
         *
         * @return bool|int The newly created page_id key; false if the row was not
         *   inserted, e.g. because the title already existed or because the specified
         *   page ID is already in use.
         */
        public function insertOn( $dbw, $pageId = null ) {
                $pageIdForInsert = $pageId ? [ 'page_id' => $pageId ] : [];
                $dbw->insert(
                        'page',
                        [
                                'page_namespace'    => $this->mTitle->getNamespace(),
                                'page_title'        => $this->mTitle->getDBkey(),
                                'page_restrictions' => '',
                                'page_is_redirect'  => 0, // Will set this shortly...
                                'page_is_new'       => 1,
                                'page_random'       => wfRandom(),
                                'page_touched'      => $dbw->timestamp(),
                                'page_latest'       => 0, // Fill this in shortly...
                                'page_len'          => 0, // Fill this in shortly...
                        ] + $pageIdForInsert,
                        __METHOD__,
                        'IGNORE'
                );

                if ( $dbw->affectedRows() > 0 ) {
                        $newid = $pageId ? (int)$pageId : $dbw->insertId();
                        $this->mId = $newid;
                        $this->mTitle->resetArticleID( $newid );

                        return $newid;
                } else {
                        return false; // nothing changed
                }
        }

        /**
         * Update the page record to point to a newly saved revision.
         *
         * @todo Factor out into a PageStore service, or move into PageUpdater.
         *
         * @param IDatabase $dbw
         * @param Revision $revision For ID number, and text used to set
         *   length and redirect status fields
         * @param int $lastRevision If given, will not overwrite the page field
         *   when different from the currently set value.
         *   Giving 0 indicates the new page flag should be set on.
         * @param bool $lastRevIsRedirect If given, will optimize adding and
         *   removing rows in redirect table.
         * @return bool Success; false if the page row was missing or page_latest changed
         */
        public function updateRevisionOn( $dbw, $revision, $lastRevision = null,
                $lastRevIsRedirect = null
        ) {
                global $wgContentHandlerUseDB;

                // TODO: move into PageUpdater or PageStore
                // NOTE: when doing that, make sure cached fields get reset in doEditContent,
                // and in the compat stub!

                // Assertion to try to catch T92046
                if ( (int)$revision->getId() === 0 ) {
                        throw new InvalidArgumentException(
                                __METHOD__ . ': Revision has ID ' . var_export( $revision->getId(), 1 )
                        );
                }

                $content = $revision->getContent();
                $len = $content ? $content->getSize() : 0;
                $rt = $content ? $content->getUltimateRedirectTarget() : null;

                $conditions = [ 'page_id' => $this->getId() ];

                if ( !is_null( $lastRevision ) ) {
                        // An extra check against threads stepping on each other
                        $conditions['page_latest'] = $lastRevision;
                }

                $revId = $revision->getId();
                Assert::parameter( $revId > 0, '$revision->getId()', 'must be > 0' );

                $row = [ /* SET */
                        'page_latest'      => $revId,
                        'page_touched'     => $dbw->timestamp( $revision->getTimestamp() ),
                        'page_is_new'      => ( $lastRevision === 0 ) ? 1 : 0,
                        'page_is_redirect' => $rt !== null ? 1 : 0,
                        'page_len'         => $len,
                ];

                if ( $wgContentHandlerUseDB ) {
                        $row['page_content_model'] = $revision->getContentModel();
                }

                $dbw->update( 'page',
                        $row,
                        $conditions,
                        __METHOD__ );

                $result = $dbw->affectedRows() > 0;
                if ( $result ) {
                        $this->updateRedirectOn( $dbw, $rt, $lastRevIsRedirect );
                        $this->setLastEdit( $revision );
                        $this->mLatest = $revision->getId();
                        $this->mIsRedirect = (bool)$rt;
                        // Update the LinkCache.
                        $linkCache = MediaWikiServices::getInstance()->getLinkCache();
                        $linkCache->addGoodLinkObj(
                                $this->getId(),
                                $this->mTitle,
                                $len,
                                $this->mIsRedirect,
                                $this->mLatest,
                                $revision->getContentModel()
                        );
                }

                return $result;
        }

        /**
         * Add row to the redirect table if this is a redirect, remove otherwise.
         *
         * @param IDatabase $dbw
         * @param Title|null $redirectTitle Title object pointing to the redirect target,
         *   or NULL if this is not a redirect
         * @param null|bool $lastRevIsRedirect If given, will optimize adding and
         *   removing rows in redirect table.
         * @return bool True on success, false on failure
         * @private
         */
        public function updateRedirectOn( $dbw, $redirectTitle, $lastRevIsRedirect = null ) {
                // Always update redirects (target link might have changed)
                // Update/Insert if we don't know if the last revision was a redirect or not
                // Delete if changing from redirect to non-redirect
                $isRedirect = !is_null( $redirectTitle );

                if ( !$isRedirect && $lastRevIsRedirect === false ) {
                        return true;
                }

                if ( $isRedirect ) {
                        $this->insertRedirectEntry( $redirectTitle );
                } else {
                        // This is not a redirect, remove row from redirect table
                        $where = [ 'rd_from' => $this->getId() ];
                        $dbw->delete( 'redirect', $where, __METHOD__ );
                }

                if ( $this->getTitle()->getNamespace() == NS_FILE ) {
                        RepoGroup::singleton()->getLocalRepo()->invalidateImageRedirect( $this->getTitle() );
                }

                return ( $dbw->affectedRows() != 0 );
        }

        /**
         * If the given revision is newer than the currently set page_latest,
         * update the page record. Otherwise, do nothing.
         *
         * @deprecated since 1.24, use updateRevisionOn instead
         *
         * @param IDatabase $dbw
         * @param Revision $revision
         * @return bool
         */
        public function updateIfNewerOn( $dbw, $revision ) {
                $row = $dbw->selectRow(
                        [ 'revision', 'page' ],
                        [ 'rev_id', 'rev_timestamp', 'page_is_redirect' ],
                        [
                                'page_id' => $this->getId(),
                                'page_latest=rev_id' ],
                        __METHOD__ );

                if ( $row ) {
                        if ( wfTimestamp( TS_MW, $row->rev_timestamp ) >= $revision->getTimestamp() ) {
                                return false;
                        }
                        $prev = $row->rev_id;
                        $lastRevIsRedirect = (bool)$row->page_is_redirect;
                } else {
                        // No or missing previous revision; mark the page as new
                        $prev = 0;
                        $lastRevIsRedirect = null;
                }

                $ret = $this->updateRevisionOn( $dbw, $revision, $prev, $lastRevIsRedirect );

                return $ret;
        }

        /**
         * Helper method for checking whether two revisions have differences that go
         * beyond the main slot.
         *
         * MCR migration note: this method should go away!
         *
         * @deprecated Use only as a stop-gap before refactoring to support MCR.
         *
         * @param Revision $a
         * @param Revision $b
         * @return bool
         */
        public static function hasDifferencesOutsideMainSlot( Revision $a, Revision $b ) {
                $aSlots = $a->getRevisionRecord()->getSlots();
                $bSlots = $b->getRevisionRecord()->getSlots();
                $changedRoles = $aSlots->getRolesWithDifferentContent( $bSlots );

                return ( $changedRoles !== [ 'main' ] );
        }

        /**
         * Get the content that needs to be saved in order to undo all revisions
         * between $undo and $undoafter. Revisions must belong to the same page,
         * must exist and must not be deleted
         *
         * @param Revision $undo
         * @param Revision $undoafter Must be an earlier revision than $undo
         * @return Content|bool Content on success, false on failure
         * @since 1.21
         * Before we had the Content object, this was done in getUndoText
         */
        public function getUndoContent( Revision $undo, Revision $undoafter ) {
                // TODO: MCR: replace this with a method that returns a RevisionSlotsUpdate

                if ( self::hasDifferencesOutsideMainSlot( $undo, $undoafter ) ) {
                        // Cannot yet undo edits that involve anything other the main slot.
                        return false;
                }

                $handler = $undo->getContentHandler();
                return $handler->getUndoContent( $this->getRevision(), $undo, $undoafter );
        }

        /**
         * Returns true if this page's content model supports sections.
         *
         * @return bool
         *
         * @todo The skin should check this and not offer section functionality if
         *   sections are not supported.
         * @todo The EditPage should check this and not offer section functionality
         *   if sections are not supported.
         */
        public function supportsSections() {
                return $this->getContentHandler()->supportsSections();
        }

        /**
         * @param string|int|null|bool $sectionId Section identifier as a number or string
         * (e.g. 0, 1 or 'T-1'), null/false or an empty string for the whole page
         * or 'new' for a new section.
         * @param Content $sectionContent New content of the section.
         * @param string $sectionTitle New section's subject, only if $section is "new".
         * @param string $edittime Revision timestamp or null to use the current revision.
         *
         * @throws MWException
         * @return Content|null New complete article content, or null if error.
         *
         * @since 1.21
         * @deprecated since 1.24, use replaceSectionAtRev instead
         */
        public function replaceSectionContent(
                $sectionId, Content $sectionContent, $sectionTitle = '', $edittime = null
        ) {
                $baseRevId = null;
                if ( $edittime && $sectionId !== 'new' ) {
                        $lb = $this->getDBLoadBalancer();
                        $dbr = $lb->getConnection( DB_REPLICA );
                        $rev = Revision::loadFromTimestamp( $dbr, $this->mTitle, $edittime );
                        // Try the master if this thread may have just added it.
                        // This could be abstracted into a Revision method, but we don't want
                        // to encourage loading of revisions by timestamp.
                        if ( !$rev
                                && $lb->getServerCount() > 1
                                && $lb->hasOrMadeRecentMasterChanges()
                        ) {
                                $dbw = $lb->getConnection( DB_MASTER );
                                $rev = Revision::loadFromTimestamp( $dbw, $this->mTitle, $edittime );
                        }
                        if ( $rev ) {
                                $baseRevId = $rev->getId();
                        }
                }

                return $this->replaceSectionAtRev( $sectionId, $sectionContent, $sectionTitle, $baseRevId );
        }

        /**
         * @param string|int|null|bool $sectionId Section identifier as a number or string
         * (e.g. 0, 1 or 'T-1'), null/false or an empty string for the whole page
         * or 'new' for a new section.
         * @param Content $sectionContent New content of the section.
         * @param string $sectionTitle New section's subject, only if $section is "new".
         * @param int|null $baseRevId
         *
         * @throws MWException
         * @return Content|null New complete article content, or null if error.
         *
         * @since 1.24
         */
        public function replaceSectionAtRev( $sectionId, Content $sectionContent,
                $sectionTitle = '', $baseRevId = null
        ) {
                if ( strval( $sectionId ) === '' ) {
                        // Whole-page edit; let the whole text through
                        $newContent = $sectionContent;
                } else {
                        if ( !$this->supportsSections() ) {
                                throw new MWException( "sections not supported for content model " .
                                        $this->getContentHandler()->getModelID() );
                        }

                        // T32711: always use current version when adding a new section
                        if ( is_null( $baseRevId ) || $sectionId === 'new' ) {
                                $oldContent = $this->getContent();
                        } else {
                                $rev = Revision::newFromId( $baseRevId );
                                if ( !$rev ) {
                                        wfDebug( __METHOD__ . " asked for bogus section (page: " .
                                                $this->getId() . "; section: $sectionId)\n" );
                                        return null;
                                }

                                $oldContent = $rev->getContent();
                        }

                        if ( !$oldContent ) {
                                wfDebug( __METHOD__ . ": no page text\n" );
                                return null;
                        }

                        $newContent = $oldContent->replaceSection( $sectionId, $sectionContent, $sectionTitle );
                }

                return $newContent;
        }

        /**
         * Check flags and add EDIT_NEW or EDIT_UPDATE to them as needed.
         *
         * @deprecated since 1.32, use exists() instead, or simply omit the EDIT_UPDATE
         * and EDIT_NEW flags. To protect against race conditions, use PageUpdater::grabParentRevision.
         *
         * @param int $flags
         * @return int Updated $flags
         */
        public function checkFlags( $flags ) {
                if ( !( $flags & EDIT_NEW ) && !( $flags & EDIT_UPDATE ) ) {
                        if ( $this->exists() ) {
                                $flags |= EDIT_UPDATE;
                        } else {
                                $flags |= EDIT_NEW;
                        }
                }

                return $flags;
        }

        /**
         * @return DerivedPageDataUpdater
         */
        private function newDerivedDataUpdater() {
                global $wgContLang, $wgRCWatchCategoryMembership, $wgArticleCountMethod;

                $derivedDataUpdater = new DerivedPageDataUpdater(
                        $this, // NOTE: eventually, PageUpdater should not know about WikiPage
                        $this->getRevisionStore(),
                        $this->getParserCache(),
                        JobQueueGroup::singleton(),
                        MessageCache::singleton(),
                        $wgContLang,
                        LoggerFactory::getInstance( 'SaveParse' )
                );

                $derivedDataUpdater->setRcWatchCategoryMembership( $wgRCWatchCategoryMembership );
                $derivedDataUpdater->setArticleCountMethod( $wgArticleCountMethod );

                return $derivedDataUpdater;
        }

        /**
         * Returns a DerivedPageDataUpdater for use with the given target revision or new content.
         * This method attempts to re-use the same DerivedPageDataUpdater instance for subsequent calls.
         * The parameters passed to this method are used to ensure that the DerivedPageDataUpdater
         * returned matches that caller's expectations, allowing an existing instance to be re-used
         * if the given parameters match that instance's internal state according to
         * DerivedPageDataUpdater::isReusableFor(), and creating a new instance of the parameters do not
         * match the existign one.
         *
         * If neither $forRevision nor $forUpdate is given, a new DerivedPageDataUpdater is always
         * created, replacing any DerivedPageDataUpdater currently cached.
         *
         * MCR migration note: this replaces WikiPage::prepareContentForEdit.
         *
         * @since 1.32
         *
         * @param User|null $forUser The user that will be used for, or was used for, PST.
         * @param RevisionRecord|null $forRevision The revision created by the edit for which
         *        to perform updates, if the edit was already saved.
         * @param RevisionSlotsUpdate|null $forUpdate The new content to be saved by the edit (pre PST),
         *        if the edit was not yet saved.
         *
         * @return DerivedPageDataUpdater
         */
        private function getDerivedDataUpdater(
                User $forUser = null,
                RevisionRecord $forRevision = null,
                RevisionSlotsUpdate $forUpdate = null
        ) {
                if ( !$forRevision && !$forUpdate ) {
                        // NOTE: can't re-use an existing derivedDataUpdater if we don't know what the caller is
                        // going to use it with.
                        $this->derivedDataUpdater = null;
                }

                if ( $this->derivedDataUpdater && !$this->derivedDataUpdater->isContentPrepared() ) {
                        // NOTE: can't re-use an existing derivedDataUpdater if other code that has a reference
                        // to it did not yet initialize it, because we don't know what data it will be
                        // initialized with.
                        $this->derivedDataUpdater = null;
                }

                // XXX: It would be nice to have an LRU cache instead of trying to re-use a single instance.
                // However, there is no good way to construct a cache key. We'd need to check against all
                // cached instances.

                if ( $this->derivedDataUpdater
                        && !$this->derivedDataUpdater->isReusableFor(
                                $forUser,
                                $forRevision,
                                $forUpdate
                        )
                ) {
                        $this->derivedDataUpdater = null;
                }

                if ( !$this->derivedDataUpdater ) {
                        $this->derivedDataUpdater = $this->newDerivedDataUpdater();
                }

                return $this->derivedDataUpdater;
        }

        /**
         * Returns a PageUpdater for creating new revisions on this page (or creating the page).
         *
         * The PageUpdater can also be used to detect the need for edit conflict resolution,
         * and to protected such conflict resolution from concurrent edits using a check-and-set
         * mechanism.
         *
         * @since 1.32
         *
         * @param User $user
         *
         * @return PageUpdater
         */
        public function newPageUpdater( User $user ) {
                global $wgAjaxEditStash, $wgUseAutomaticEditSummaries, $wgPageCreationLog;

                $pageUpdater = new PageUpdater(
                        $user,
                        $this, // NOTE: eventually, PageUpdater should not know about WikiPage
                        $this->getDerivedDataUpdater( $user ),
                        $this->getDBLoadBalancer(),
                        $this->getRevisionStore()
                );

                $pageUpdater->setUsePageCreationLog( $wgPageCreationLog );
                $pageUpdater->setAjaxEditStash( $wgAjaxEditStash );
                $pageUpdater->setUseAutomaticEditSummaries( $wgUseAutomaticEditSummaries );

                return $pageUpdater;
        }

        /**
         * Change an existing article or create a new article. Updates RC and all necessary caches,
         * optionally via the deferred update array.
         *
         * @deprecated since 1.32, use PageUpdater::saveRevision instead. Note that the new method
         * expects callers to take care of checking EDIT_MINOR against the minoredit right, and to
         * apply the autopatrol right as appropriate.
         *
         * @param Content $content New content
         * @param string|CommentStoreComment $summary Edit summary
         * @param int $flags Bitfield:
         *      EDIT_NEW
         *          Article is known or assumed to be non-existent, create a new one
         *      EDIT_UPDATE
         *          Article is known or assumed to be pre-existing, update it
         *      EDIT_MINOR
         *          Mark this edit minor, if the user is allowed to do so
         *      EDIT_SUPPRESS_RC
         *          Do not log the change in recentchanges
         *      EDIT_FORCE_BOT
         *          Mark the edit a "bot" edit regardless of user rights
         *      EDIT_AUTOSUMMARY
         *          Fill in blank summaries with generated text where possible
         *      EDIT_INTERNAL
         *          Signal that the page retrieve/save cycle happened entirely in this request.
         *
         * If neither EDIT_NEW nor EDIT_UPDATE is specified, the status of the
         * article will be detected. If EDIT_UPDATE is specified and the article
         * doesn't exist, the function will return an edit-gone-missing error. If
         * EDIT_NEW is specified and the article does exist, an edit-already-exists
         * error will be returned. These two conditions are also possible with
         * auto-detection due to MediaWiki's performance-optimised locking strategy.
         *
         * @param bool|int $originalRevId: The ID of an original revision that the edit
         * restores or repeats. The new revision is expected to have the exact same content as
         * the given original revision. This is used with rollbacks and with dummy "null" revisions
         * which are created to record things like page moves.
         * @param User $user The user doing the edit
         * @param string $serialFormat IGNORED.
         * @param array|null $tags Change tags to apply to this edit
         * Callers are responsible for permission checks
         * (with ChangeTags::canAddTagsAccompanyingChange)
         * @param Int $undidRevId Id of revision that was undone or 0
         *
         * @throws MWException
         * @return Status Possible errors:
         *     edit-hook-aborted: The ArticleSave hook aborted the edit but didn't
         *       set the fatal flag of $status.
         *     edit-gone-missing: In update mode, but the article didn't exist.
         *     edit-conflict: In update mode, the article changed unexpectedly.
         *     edit-no-change: Warning that the text was the same as before.
         *     edit-already-exists: In creation mode, but the article already exists.
         *
         *  Extensions may define additional errors.
         *
         *  $return->value will contain an associative array with members as follows:
         *     new: Boolean indicating if the function attempted to create a new article.
         *     revision: The revision object for the inserted revision, or null.
         *
         * @since 1.21
         * @throws MWException
         */
        public function doEditContent(
                Content $content, $summary, $flags = 0, $originalRevId = false,
                User $user = null, $serialFormat = null, $tags = [], $undidRevId = 0
        ) {
                global $wgUser, $wgUseNPPatrol, $wgUseRCPatrol;

                if ( !( $summary instanceof CommentStoreComment ) ) {
                        $summary = CommentStoreComment::newUnsavedComment( trim( $summary ) );
                }

                if ( !$user ) {
                        $user = $wgUser;
                }

                // TODO: this check is here for backwards-compatibility with 1.31 behavior.
                // Checking the minoredit right should be done in the same place the 'bot' right is
                // checked for the EDIT_FORCE_BOT flag, which is currently in EditPage::attemptSave.
                if ( ( $flags & EDIT_MINOR ) && !$user->isAllowed( 'minoredit' ) ) {
                        $flags = ( $flags & ~EDIT_MINOR );
                }

                // NOTE: while doEditContent() executes, callbacks to getDerivedDataUpdater and
                // prepareContentForEdit will generally use the DerivedPageDataUpdater that is also
                // used by this PageUpdater. However, there is no guarantee for this.
                $updater = $this->newPageUpdater( $user );
                $updater->setContent( 'main', $content );
                $updater->setOriginalRevisionId( $originalRevId );
                $updater->setUndidRevisionId( $undidRevId );

                $needsPatrol = $wgUseRCPatrol || ( $wgUseNPPatrol && !$this->exists() );

                // TODO: this logic should not be in the storage layer, it's here for compatibility
                // with 1.31 behavior. Applying the 'autopatrol' right should be done in the same
                // place the 'bot' right is handled, which is currently in EditPage::attemptSave.
                if ( $needsPatrol && $this->getTitle()->userCan( 'autopatrol', $user ) ) {
                        $updater->setRcPatrolStatus( RecentChange::PRC_AUTOPATROLLED );
                }

                $updater->addTags( $tags );

                $revRec = $updater->saveRevision(
                        $summary,
                        $flags
                );

                // $revRec will be null if the edit failed, or if no new revision was created because
                // the content did not change.
                if ( $revRec ) {
                        // update cached fields
                        // TODO: this is currently redundant to what is done in updateRevisionOn.
                        // But updateRevisionOn() should move into PageStore, and then this will be needed.
                        $this->setLastEdit( new Revision( $revRec ) ); // TODO: use RevisionRecord
                        $this->mLatest = $revRec->getId();
                }

                return $updater->getStatus();
        }

        /**
         * Get parser options suitable for rendering the primary article wikitext
         *
         * @see ContentHandler::makeParserOptions
         *
         * @param IContextSource|User|string $context One of the following:
         *        - IContextSource: Use the User and the Language of the provided
         *          context
         *        - User: Use the provided User object and $wgLang for the language,
         *          so use an IContextSource object if possible.
         *        - 'canonical': Canonical options (anonymous user with default
         *          preferences and content language).
         * @return ParserOptions
         */
        public function makeParserOptions( $context ) {
                $options = $this->getContentHandler()->makeParserOptions( $context );

                if ( $this->getTitle()->isConversionTable() ) {
                        // @todo ConversionTable should become a separate content model, so
                        // we don't need special cases like this one.
                        $options->disableContentConversion();
                }

                return $options;
        }

        /**
         * Prepare content which is about to be saved.
         *
         * Prior to 1.30, this returned a stdClass.
         *
         * @deprecated since 1.32, use getDerivedDataUpdater instead.
         *
         * @param Content $content
         * @param Revision|RevisionRecord|int|null $revision Revision object.
         *        For backwards compatibility, a revision ID is also accepted,
         *        but this is deprecated.
         *        Used with vary-revision or vary-revision-id.
         * @param User|null $user
         * @param string|null $serialFormat IGNORED
         * @param bool $useCache Check shared prepared edit cache
         *
         * @return PreparedEdit
         *
         * @since 1.21
         */
        public function prepareContentForEdit(
                Content $content,
                $revision = null,
                User $user = null,
                $serialFormat = null,
                $useCache = true
        ) {
                global $wgUser;

                if ( !$user ) {
                        $user = $wgUser;
                }

                if ( !is_object( $revision ) ) {
                        $revid = $revision;
                        // This code path is deprecated, and nothing is known to
                        // use it, so performance here shouldn't be a worry.
                        if ( $revid !== null ) {
                                wfDeprecated( __METHOD__ . ' with $revision = revision ID', '1.25' );
                                $store = $this->getRevisionStore();
                                $revision = $store->getRevisionById( $revid, Revision::READ_LATEST );
                        } else {
                                $revision = null;
                        }
                } elseif ( $revision instanceof Revision ) {
                        $revision = $revision->getRevisionRecord();
                }

                $slots = RevisionSlotsUpdate::newFromContent( [ 'main' => $content ] );
                $updater = $this->getDerivedDataUpdater( $user, $revision, $slots );

                if ( !$updater->isUpdatePrepared() ) {
                        $updater->prepareContent( $user, $slots, [], $useCache );

                        if ( $revision ) {
                                $updater->prepareUpdate( $revision );
                        }
                }

                return $updater->getPreparedEdit();
        }

        /**
         * Do standard deferred updates after page edit.
         * Update links tables, site stats, search index and message cache.
         * Purges pages that include this page if the text was changed here.
         * Every 100th edit, prune the recent changes table.
         *
         * @deprecated since 1.32, use PageUpdater::doEditUpdates instead.
         *
         * @param Revision $revision
         * @param User $user User object that did the revision
         * @param array $options Array of options, following indexes are used:
         * - changed: bool, whether the revision changed the content (default true)
         * - created: bool, whether the revision created the page (default false)
         * - moved: bool, whether the page was moved (default false)
         * - restored: bool, whether the page was undeleted (default false)
         * - oldrevision: Revision object for the pre-update revision (default null)
         * - oldcountable: bool, null, or string 'no-change' (default null):
         *   - bool: whether the page was counted as an article before that
         *     revision, only used in changed is true and created is false
         *   - null: if created is false, don't update the article count; if created
         *     is true, do update the article count
         *   - 'no-change': don't update the article count, ever
         */
        public function doEditUpdates( Revision $revision, User $user, array $options = [] ) {
                $revision = $revision->getRevisionRecord();

                $updater = $this->getDerivedDataUpdater( $user, $revision );

                $updater->prepareUpdate( $revision, $options );

                $updater->doUpdates();
        }

        /**
         * Update the article's restriction field, and leave a log entry.
         * This works for protection both existing and non-existing pages.
         *
         * @param array $limit Set of restriction keys
         * @param array $expiry Per restriction type expiration
         * @param int &$cascade Set to false if cascading protection isn't allowed.
         * @param string $reason
         * @param User $user The user updating the restrictions
         * @param string|string[] $tags Change tags to add to the pages and protection log entries
         *   ($user should be able to add the specified tags before this is called)
         * @return Status Status object; if action is taken, $status->value is the log_id of the
         *   protection log entry.
         */
        public function doUpdateRestrictions( array $limit, array $expiry,
                &$cascade, $reason, User $user, $tags = null
        ) {
                global $wgCascadingRestrictionLevels;

                if ( wfReadOnly() ) {
                        return Status::newFatal( wfMessage( 'readonlytext', wfReadOnlyReason() ) );
                }

                $this->loadPageData( 'fromdbmaster' );
                $restrictionTypes = $this->mTitle->getRestrictionTypes();
                $id = $this->getId();

                if ( !$cascade ) {
                        $cascade = false;
                }

                // Take this opportunity to purge out expired restrictions
                Title::purgeExpiredRestrictions();

                // @todo: Same limitations as described in ProtectionForm.php (line 37);
                // we expect a single selection, but the schema allows otherwise.
                $isProtected = false;
                $protect = false;
                $changed = false;

                $dbw = wfGetDB( DB_MASTER );

                foreach ( $restrictionTypes as $action ) {
                        if ( !isset( $expiry[$action] ) || $expiry[$action] === $dbw->getInfinity() ) {
                                $expiry[$action] = 'infinity';
                        }
                        if ( !isset( $limit[$action] ) ) {
                                $limit[$action] = '';
                        } elseif ( $limit[$action] != '' ) {
                                $protect = true;
                        }

                        // Get current restrictions on $action
                        $current = implode( '', $this->mTitle->getRestrictions( $action ) );
                        if ( $current != '' ) {
                                $isProtected = true;
                        }

                        if ( $limit[$action] != $current ) {
                                $changed = true;
                        } elseif ( $limit[$action] != '' ) {
                                // Only check expiry change if the action is actually being
                                // protected, since expiry does nothing on an not-protected
                                // action.
                                if ( $this->mTitle->getRestrictionExpiry( $action ) != $expiry[$action] ) {
                                        $changed = true;
                                }
                        }
                }

                if ( !$changed && $protect && $this->mTitle->areRestrictionsCascading() != $cascade ) {
                        $changed = true;
                }

                // If nothing has changed, do nothing
                if ( !$changed ) {
                        return Status::newGood();
                }

                if ( !$protect ) { // No protection at all means unprotection
                        $revCommentMsg = 'unprotectedarticle-comment';
                        $logAction = 'unprotect';
                } elseif ( $isProtected ) {
                        $revCommentMsg = 'modifiedarticleprotection-comment';
                        $logAction = 'modify';
                } else {
                        $revCommentMsg = 'protectedarticle-comment';
                        $logAction = 'protect';
                }

                $logRelationsValues = [];
                $logRelationsField = null;
                $logParamsDetails = [];

                // Null revision (used for change tag insertion)
                $nullRevision = null;

                if ( $id ) { // Protection of existing page
                        // Avoid PHP 7.1 warning of passing $this by reference
                        $wikiPage = $this;

                        if ( !Hooks::run( 'ArticleProtect', [ &$wikiPage, &$user, $limit, $reason ] ) ) {
                                return Status::newGood();
                        }

                        // Only certain restrictions can cascade...
                        $editrestriction = isset( $limit['edit'] )
                                ? [ $limit['edit'] ]
                                : $this->mTitle->getRestrictions( 'edit' );
                        foreach ( array_keys( $editrestriction, 'sysop' ) as $key ) {
                                $editrestriction[$key] = 'editprotected'; // backwards compatibility
                        }
                        foreach ( array_keys( $editrestriction, 'autoconfirmed' ) as $key ) {
                                $editrestriction[$key] = 'editsemiprotected'; // backwards compatibility
                        }

                        $cascadingRestrictionLevels = $wgCascadingRestrictionLevels;
                        foreach ( array_keys( $cascadingRestrictionLevels, 'sysop' ) as $key ) {
                                $cascadingRestrictionLevels[$key] = 'editprotected'; // backwards compatibility
                        }
                        foreach ( array_keys( $cascadingRestrictionLevels, 'autoconfirmed' ) as $key ) {
                                $cascadingRestrictionLevels[$key] = 'editsemiprotected'; // backwards compatibility
                        }

                        // The schema allows multiple restrictions
                        if ( !array_intersect( $editrestriction, $cascadingRestrictionLevels ) ) {
                                $cascade = false;
                        }

                        // insert null revision to identify the page protection change as edit summary
                        $latest = $this->getLatest();
                        $nullRevision = $this->insertProtectNullRevision(
                                $revCommentMsg,
                                $limit,
                                $expiry,
                                $cascade,
                                $reason,
                                $user
                        );

                        if ( $nullRevision === null ) {
                                return Status::newFatal( 'no-null-revision', $this->mTitle->getPrefixedText() );
                        }

                        $logRelationsField = 'pr_id';

                        // Update restrictions table
                        foreach ( $limit as $action => $restrictions ) {
                                $dbw->delete(
                                        'page_restrictions',
                                        [
                                                'pr_page' => $id,
                                                'pr_type' => $action
                                        ],
                                        __METHOD__
                                );
                                if ( $restrictions != '' ) {
                                        $cascadeValue = ( $cascade && $action == 'edit' ) ? 1 : 0;
                                        $dbw->insert(
                                                'page_restrictions',
                                                [
                                                        'pr_page' => $id,
                                                        'pr_type' => $action,
                                                        'pr_level' => $restrictions,
                                                        'pr_cascade' => $cascadeValue,
                                                        'pr_expiry' => $dbw->encodeExpiry( $expiry[$action] )
                                                ],
                                                __METHOD__
                                        );
                                        $logRelationsValues[] = $dbw->insertId();
                                        $logParamsDetails[] = [
                                                'type' => $action,
                                                'level' => $restrictions,
                                                'expiry' => $expiry[$action],
                                                'cascade' => (bool)$cascadeValue,
                                        ];
                                }
                        }

                        // Clear out legacy restriction fields
                        $dbw->update(
                                'page',
                                [ 'page_restrictions' => '' ],
                                [ 'page_id' => $id ],
                                __METHOD__
                        );

                        // Avoid PHP 7.1 warning of passing $this by reference
                        $wikiPage = $this;

                        Hooks::run( 'NewRevisionFromEditComplete',
                                [ $this, $nullRevision, $latest, $user ] );
                        Hooks::run( 'ArticleProtectComplete', [ &$wikiPage, &$user, $limit, $reason ] );
                } else { // Protection of non-existing page (also known as "title protection")
                        // Cascade protection is meaningless in this case
                        $cascade = false;

                        if ( $limit['create'] != '' ) {
                                $commentFields = CommentStore::getStore()->insert( $dbw, 'pt_reason', $reason );
                                $dbw->replace( 'protected_titles',
                                        [ [ 'pt_namespace', 'pt_title' ] ],
                                        [
                                                'pt_namespace' => $this->mTitle->getNamespace(),
                                                'pt_title' => $this->mTitle->getDBkey(),
                                                'pt_create_perm' => $limit['create'],
                                                'pt_timestamp' => $dbw->timestamp(),
                                                'pt_expiry' => $dbw->encodeExpiry( $expiry['create'] ),
                                                'pt_user' => $user->getId(),
                                        ] + $commentFields, __METHOD__
                                );
                                $logParamsDetails[] = [
                                        'type' => 'create',
                                        'level' => $limit['create'],
                                        'expiry' => $expiry['create'],
                                ];
                        } else {
                                $dbw->delete( 'protected_titles',
                                        [
                                                'pt_namespace' => $this->mTitle->getNamespace(),
                                                'pt_title' => $this->mTitle->getDBkey()
                                        ], __METHOD__
                                );
                        }
                }

                $this->mTitle->flushRestrictions();
                InfoAction::invalidateCache( $this->mTitle );

                if ( $logAction == 'unprotect' ) {
                        $params = [];
                } else {
                        $protectDescriptionLog = $this->protectDescriptionLog( $limit, $expiry );
                        $params = [
                                '4::description' => $protectDescriptionLog, // parameter for IRC
                                '5:bool:cascade' => $cascade,
                                'details' => $logParamsDetails, // parameter for localize and api
                        ];
                }

                // Update the protection log
                $logEntry = new ManualLogEntry( 'protect', $logAction );
                $logEntry->setTarget( $this->mTitle );
                $logEntry->setComment( $reason );
                $logEntry->setPerformer( $user );
                $logEntry->setParameters( $params );
                if ( !is_null( $nullRevision ) ) {
                        $logEntry->setAssociatedRevId( $nullRevision->getId() );
                }
                $logEntry->setTags( $tags );
                if ( $logRelationsField !== null && count( $logRelationsValues ) ) {
                        $logEntry->setRelations( [ $logRelationsField => $logRelationsValues ] );
                }
                $logId = $logEntry->insert();
                $logEntry->publish( $logId );

                return Status::newGood( $logId );
        }

        /**
         * Insert a new null revision for this page.
         *
         * @param string $revCommentMsg Comment message key for the revision
         * @param array $limit Set of restriction keys
         * @param array $expiry Per restriction type expiration
         * @param int $cascade Set to false if cascading protection isn't allowed.
         * @param string $reason
         * @param User|null $user
         * @return Revision|null Null on error
         */
        public function insertProtectNullRevision( $revCommentMsg, array $limit,
                array $expiry, $cascade, $reason, $user = null
        ) {
                $dbw = wfGetDB( DB_MASTER );

                // Prepare a null revision to be added to the history
                $editComment = wfMessage(
                        $revCommentMsg,
                        $this->mTitle->getPrefixedText(),
                        $user ? $user->getName() : ''
                )->inContentLanguage()->text();
                if ( $reason ) {
                        $editComment .= wfMessage( 'colon-separator' )->inContentLanguage()->text() . $reason;
                }
                $protectDescription = $this->protectDescription( $limit, $expiry );
                if ( $protectDescription ) {
                        $editComment .= wfMessage( 'word-separator' )->inContentLanguage()->text();
                        $editComment .= wfMessage( 'parentheses' )->params( $protectDescription )
                                ->inContentLanguage()->text();
                }
                if ( $cascade ) {
                        $editComment .= wfMessage( 'word-separator' )->inContentLanguage()->text();
                        $editComment .= wfMessage( 'brackets' )->params(
                                wfMessage( 'protect-summary-cascade' )->inContentLanguage()->text()
                        )->inContentLanguage()->text();
                }

                $nullRev = Revision::newNullRevision( $dbw, $this->getId(), $editComment, true, $user );
                if ( $nullRev ) {
                        $nullRev->insertOn( $dbw );

                        // Update page record and touch page
                        $oldLatest = $nullRev->getParentId();
                        $this->updateRevisionOn( $dbw, $nullRev, $oldLatest );
                }

                return $nullRev;
        }

        /**
         * @param string $expiry 14-char timestamp or "infinity", or false if the input was invalid
         * @return string
         */
        protected function formatExpiry( $expiry ) {
                global $wgContLang;

                if ( $expiry != 'infinity' ) {
                        return wfMessage(
                                'protect-expiring',
                                $wgContLang->timeanddate( $expiry, false, false ),
                                $wgContLang->date( $expiry, false, false ),
                                $wgContLang->time( $expiry, false, false )
                        )->inContentLanguage()->text();
                } else {
                        return wfMessage( 'protect-expiry-indefinite' )
                                ->inContentLanguage()->text();
                }
        }

        /**
         * Builds the description to serve as comment for the edit.
         *
         * @param array $limit Set of restriction keys
         * @param array $expiry Per restriction type expiration
         * @return string
         */
        public function protectDescription( array $limit, array $expiry ) {
                $protectDescription = '';

                foreach ( array_filter( $limit ) as $action => $restrictions ) {
                        # $action is one of $wgRestrictionTypes = [ 'create', 'edit', 'move', 'upload' ].
                        # All possible message keys are listed here for easier grepping:
                        # * restriction-create
                        # * restriction-edit
                        # * restriction-move
                        # * restriction-upload
                        $actionText = wfMessage( 'restriction-' . $action )->inContentLanguage()->text();
                        # $restrictions is one of $wgRestrictionLevels = [ '', 'autoconfirmed', 'sysop' ],
                        # with '' filtered out. All possible message keys are listed below:
                        # * protect-level-autoconfirmed
                        # * protect-level-sysop
                        $restrictionsText = wfMessage( 'protect-level-' . $restrictions )
                                ->inContentLanguage()->text();

                        $expiryText = $this->formatExpiry( $expiry[$action] );

                        if ( $protectDescription !== '' ) {
                                $protectDescription .= wfMessage( 'word-separator' )->inContentLanguage()->text();
                        }
                        $protectDescription .= wfMessage( 'protect-summary-desc' )
                                ->params( $actionText, $restrictionsText, $expiryText )
                                ->inContentLanguage()->text();
                }

                return $protectDescription;
        }

        /**
         * Builds the description to serve as comment for the log entry.
         *
         * Some bots may parse IRC lines, which are generated from log entries which contain plain
         * protect description text. Keep them in old format to avoid breaking compatibility.
         * TODO: Fix protection log to store structured description and format it on-the-fly.
         *
         * @param array $limit Set of restriction keys
         * @param array $expiry Per restriction type expiration
         * @return string
         */
        public function protectDescriptionLog( array $limit, array $expiry ) {
                global $wgContLang;

                $protectDescriptionLog = '';

                foreach ( array_filter( $limit ) as $action => $restrictions ) {
                        $expiryText = $this->formatExpiry( $expiry[$action] );
                        $protectDescriptionLog .= $wgContLang->getDirMark() .
                                "[$action=$restrictions] ($expiryText)";
                }

                return trim( $protectDescriptionLog );
        }

        /**
         * Take an array of page restrictions and flatten it to a string
         * suitable for insertion into the page_restrictions field.
         *
         * @param string[] $limit
         *
         * @throws MWException
         * @return string
         */
        protected static function flattenRestrictions( $limit ) {
                if ( !is_array( $limit ) ) {
                        throw new MWException( __METHOD__ . ' given non-array restriction set' );
                }

                $bits = [];
                ksort( $limit );

                foreach ( array_filter( $limit ) as $action => $restrictions ) {
                        $bits[] = "$action=$restrictions";
                }

                return implode( ':', $bits );
        }

        /**
         * Same as doDeleteArticleReal(), but returns a simple boolean. This is kept around for
         * backwards compatibility, if you care about error reporting you should use
         * doDeleteArticleReal() instead.
         *
         * Deletes the article with database consistency, writes logs, purges caches
         *
         * @param string $reason Delete reason for deletion log
         * @param bool $suppress Suppress all revisions and log the deletion in
         *        the suppression log instead of the deletion log
         * @param int $u1 Unused
         * @param bool $u2 Unused
         * @param array|string &$error Array of errors to append to
         * @param User $user The deleting user
         * @return bool True if successful
         */
        public function doDeleteArticle(
                $reason, $suppress = false, $u1 = null, $u2 = null, &$error = '', User $user = null
        ) {
                $status = $this->doDeleteArticleReal( $reason, $suppress, $u1, $u2, $error, $user );
                return $status->isGood();
        }

        /**
         * Back-end article deletion
         * Deletes the article with database consistency, writes logs, purges caches
         *
         * @since 1.19
         *
         * @param string $reason Delete reason for deletion log
         * @param bool $suppress Suppress all revisions and log the deletion in
         *   the suppression log instead of the deletion log
         * @param int $u1 Unused
         * @param bool $u2 Unused
         * @param array|string &$error Array of errors to append to
         * @param User $deleter The deleting user
         * @param array $tags Tags to apply to the deletion action
         * @param string $logsubtype
         * @return Status Status object; if successful, $status->value is the log_id of the
         *   deletion log entry. If the page couldn't be deleted because it wasn't
         *   found, $status is a non-fatal 'cannotdelete' error
         */
        public function doDeleteArticleReal(
                $reason, $suppress = false, $u1 = null, $u2 = null, &$error = '', User $deleter = null,
                $tags = [], $logsubtype = 'delete'
        ) {
                global $wgUser, $wgContentHandlerUseDB, $wgCommentTableSchemaMigrationStage,
                        $wgActorTableSchemaMigrationStage, $wgMultiContentRevisionSchemaMigrationStage;

                wfDebug( __METHOD__ . "\n" );

                $status = Status::newGood();

                if ( $this->mTitle->getDBkey() === '' ) {
                        $status->error( 'cannotdelete',
                                wfEscapeWikiText( $this->getTitle()->getPrefixedText() ) );
                        return $status;
                }

                // Avoid PHP 7.1 warning of passing $this by reference
                $wikiPage = $this;

                $deleter = is_null( $deleter ) ? $wgUser : $deleter;
                if ( !Hooks::run( 'ArticleDelete',
                        [ &$wikiPage, &$deleter, &$reason, &$error, &$status, $suppress ]
                ) ) {
                        if ( $status->isOK() ) {
                                // Hook aborted but didn't set a fatal status
                                $status->fatal( 'delete-hook-aborted' );
                        }
                        return $status;
                }

                $dbw = wfGetDB( DB_MASTER );
                $dbw->startAtomic( __METHOD__ );

                $this->loadPageData( self::READ_LATEST );
                $id = $this->getId();
                // T98706: lock the page from various other updates but avoid using
                // WikiPage::READ_LOCKING as that will carry over the FOR UPDATE to
                // the revisions queries (which also JOIN on user). Only lock the page
                // row and CAS check on page_latest to see if the trx snapshot matches.
                $lockedLatest = $this->lockAndGetLatest();
                if ( $id == 0 || $this->getLatest() != $lockedLatest ) {
                        $dbw->endAtomic( __METHOD__ );
                        // Page not there or trx snapshot is stale
                        $status->error( 'cannotdelete',
                                wfEscapeWikiText( $this->getTitle()->getPrefixedText() ) );
                        return $status;
                }

                // Given the lock above, we can be confident in the title and page ID values
                $namespace = $this->getTitle()->getNamespace();
                $dbKey = $this->getTitle()->getDBkey();

                // At this point we are now comitted to returning an OK
                // status unless some DB query error or other exception comes up.
                // This way callers don't have to call rollback() if $status is bad
                // unless they actually try to catch exceptions (which is rare).

                // we need to remember the old content so we can use it to generate all deletion updates.
                $revision = $this->getRevision();
                try {
                        $content = $this->getContent( Revision::RAW );
                } catch ( Exception $ex ) {
                        wfLogWarning( __METHOD__ . ': failed to load content during deletion! '
                                . $ex->getMessage() );

                        $content = null;
                }

                $commentStore = CommentStore::getStore();
                $actorMigration = ActorMigration::newMigration();

                $revQuery = Revision::getQueryInfo();
                $bitfield = false;

                // Bitfields to further suppress the content
                if ( $suppress ) {
                        $bitfield = Revision::SUPPRESSED_ALL;
                        $revQuery['fields'] = array_diff( $revQuery['fields'], [ 'rev_deleted' ] );
                }

                // For now, shunt the revision data into the archive table.
                // Text is *not* removed from the text table; bulk storage
                // is left intact to avoid breaking block-compression or
                // immutable storage schemes.
                // In the future, we may keep revisions and mark them with
                // the rev_deleted field, which is reserved for this purpose.

                // Lock rows in `revision` and its temp tables, but not any others.
                // Note array_intersect() preserves keys from the first arg, and we're
                // assuming $revQuery has `revision` primary and isn't using subtables
                // for anything we care about.
                $res = $dbw->select(
                        array_intersect(
                                $revQuery['tables'],
                                [ 'revision', 'revision_comment_temp', 'revision_actor_temp' ]
                        ),
                        '1',
                        [ 'rev_page' => $id ],
                        __METHOD__,
                        'FOR UPDATE',
                        $revQuery['joins']
                );
                foreach ( $res as $row ) {
                        // Fetch all rows in case the DB needs that to properly lock them.
                }

                // Get all of the page revisions
                $res = $dbw->select(
                        $revQuery['tables'],
                        $revQuery['fields'],
                        [ 'rev_page' => $id ],
                        __METHOD__,
                        [],
                        $revQuery['joins']
                );

                // Build their equivalent archive rows
                $rowsInsert = [];
                $revids = [];

                /** @var int[] Revision IDs of edits that were made by IPs */
                $ipRevIds = [];

                foreach ( $res as $row ) {
                        $comment = $commentStore->getComment( 'rev_comment', $row );
                        $user = User::newFromAnyId( $row->rev_user, $row->rev_user_text, $row->rev_actor );
                        $rowInsert = [
                                'ar_namespace'  => $namespace,
                                'ar_title'      => $dbKey,
                                'ar_timestamp'  => $row->rev_timestamp,
                                'ar_minor_edit' => $row->rev_minor_edit,
                                'ar_rev_id'     => $row->rev_id,
                                'ar_parent_id'  => $row->rev_parent_id,
                                        /**
                                         * ar_text_id should probably not be written to when the multi content schema has
                                         * been migrated to (wgMultiContentRevisionSchemaMigrationStage) however there is no
                                         * default for the field in WMF production currently so we must keep writing
                                         * writing until a default of 0 is set.
                                         * Task: https://phabricator.wikimedia.org/T190148
                                         * Copying the value from the revision table should not lead to any issues for now.
                                         */
                                'ar_len'        => $row->rev_len,
                                'ar_page_id'    => $id,
                                'ar_deleted'    => $suppress ? $bitfield : $row->rev_deleted,
                                'ar_sha1'       => $row->rev_sha1,
                        ] + $commentStore->insert( $dbw, 'ar_comment', $comment )
                                + $actorMigration->getInsertValues( $dbw, 'ar_user', $user );

                        if ( $wgMultiContentRevisionSchemaMigrationStage < MIGRATION_NEW ) {
                                $rowInsert['ar_text_id'] = $row->rev_text_id;
                        }

                        if (
                                $wgContentHandlerUseDB &&
                                $wgMultiContentRevisionSchemaMigrationStage <= MIGRATION_WRITE_BOTH
                        ) {
                                $rowInsert['ar_content_model'] = $row->rev_content_model;
                                $rowInsert['ar_content_format'] = $row->rev_content_format;
                        }
                        $rowsInsert[] = $rowInsert;
                        $revids[] = $row->rev_id;

                        // Keep track of IP edits, so that the corresponding rows can
                        // be deleted in the ip_changes table.
                        if ( (int)$row->rev_user === 0 && IP::isValid( $row->rev_user_text ) ) {
                                $ipRevIds[] = $row->rev_id;
                        }
                }
                // Copy them into the archive table
                $dbw->insert( 'archive', $rowsInsert, __METHOD__ );
                // Save this so we can pass it to the ArticleDeleteComplete hook.
                $archivedRevisionCount = $dbw->affectedRows();

                // Clone the title and wikiPage, so we have the information we need when
                // we log and run the ArticleDeleteComplete hook.
                $logTitle = clone $this->mTitle;
                $wikiPageBeforeDelete = clone $this;

                // Now that it's safely backed up, delete it
                $dbw->delete( 'page', [ 'page_id' => $id ], __METHOD__ );
                $dbw->delete( 'revision', [ 'rev_page' => $id ], __METHOD__ );
                if ( $wgCommentTableSchemaMigrationStage > MIGRATION_OLD ) {
                        $dbw->delete( 'revision_comment_temp', [ 'revcomment_rev' => $revids ], __METHOD__ );
                }
                if ( $wgActorTableSchemaMigrationStage > MIGRATION_OLD ) {
                        $dbw->delete( 'revision_actor_temp', [ 'revactor_rev' => $revids ], __METHOD__ );
                }

                // Also delete records from ip_changes as applicable.
                if ( count( $ipRevIds ) > 0 ) {
                        $dbw->delete( 'ip_changes', [ 'ipc_rev_id' => $ipRevIds ], __METHOD__ );
                }

                // Log the deletion, if the page was suppressed, put it in the suppression log instead
                $logtype = $suppress ? 'suppress' : 'delete';

                $logEntry = new ManualLogEntry( $logtype, $logsubtype );
                $logEntry->setPerformer( $deleter );
                $logEntry->setTarget( $logTitle );
                $logEntry->setComment( $reason );
                $logEntry->setTags( $tags );
                $logid = $logEntry->insert();

                $dbw->onTransactionPreCommitOrIdle(
                        function () use ( $logEntry, $logid ) {
                                // T58776: avoid deadlocks (especially from FileDeleteForm)
                                $logEntry->publish( $logid );
                        },
                        __METHOD__
                );

                $dbw->endAtomic( __METHOD__ );

                $this->doDeleteUpdates( $id, $content, $revision, $deleter );

                Hooks::run( 'ArticleDeleteComplete', [
                        &$wikiPageBeforeDelete,
                        &$deleter,
                        $reason,
                        $id,
                        $content,
                        $logEntry,
                        $archivedRevisionCount
                ] );
                $status->value = $logid;

                // Show log excerpt on 404 pages rather than just a link
                $cache = MediaWikiServices::getInstance()->getMainObjectStash();
                $key = $cache->makeKey( 'page-recent-delete', md5( $logTitle->getPrefixedText() ) );
                $cache->set( $key, 1, $cache::TTL_DAY );

                return $status;
        }

        /**
         * Lock the page row for this title+id and return page_latest (or 0)
         *
         * @return int Returns 0 if no row was found with this title+id
         * @since 1.27
         */
        public function lockAndGetLatest() {
                return (int)wfGetDB( DB_MASTER )->selectField(
                        'page',
                        'page_latest',
                        [
                                'page_id' => $this->getId(),
                                // Typically page_id is enough, but some code might try to do
                                // updates assuming the title is the same, so verify that
                                'page_namespace' => $this->getTitle()->getNamespace(),
                                'page_title' => $this->getTitle()->getDBkey()
                        ],
                        __METHOD__,
                        [ 'FOR UPDATE' ]
                );
        }

        /**
         * Do some database updates after deletion
         *
         * @param int $id The page_id value of the page being deleted
         * @param Content|null $content Optional page content to be used when determining
         *   the required updates. This may be needed because $this->getContent()
         *   may already return null when the page proper was deleted.
         * @param Revision|null $revision The latest page revision
         * @param User|null $user The user that caused the deletion
         */
        public function doDeleteUpdates(
                $id, Content $content = null, Revision $revision = null, User $user = null
        ) {
                try {
                        $countable = $this->isCountable();
                } catch ( Exception $ex ) {
                        // fallback for deleting broken pages for which we cannot load the content for
                        // some reason. Note that doDeleteArticleReal() already logged this problem.
                        $countable = false;
                }

                // Update site status
                DeferredUpdates::addUpdate( SiteStatsUpdate::factory(
                        [ 'edits' => 1, 'articles' => -$countable, 'pages' => -1 ]
                ) );

                // Delete pagelinks, update secondary indexes, etc
                $updates = $this->getDeletionUpdates( $content );
                foreach ( $updates as $update ) {
                        DeferredUpdates::addUpdate( $update );
                }

                $causeAgent = $user ? $user->getName() : 'unknown';
                // Reparse any pages transcluding this page
                LinksUpdate::queueRecursiveJobsForTable(
                        $this->mTitle, 'templatelinks', 'delete-page', $causeAgent );
                // Reparse any pages including this image
                if ( $this->mTitle->getNamespace() == NS_FILE ) {
                        LinksUpdate::queueRecursiveJobsForTable(
                                $this->mTitle, 'imagelinks', 'delete-page', $causeAgent );
                }

                // Clear caches
                self::onArticleDelete( $this->mTitle );
                ResourceLoaderWikiModule::invalidateModuleCache(
                        $this->mTitle, $revision, null, wfWikiID()
                );

                // Reset this object and the Title object
                $this->loadFromRow( false, self::READ_LATEST );

                // Search engine
                DeferredUpdates::addUpdate( new SearchUpdate( $id, $this->mTitle ) );
        }

        /**
         * Roll back the most recent consecutive set of edits to a page
         * from the same user; fails if there are no eligible edits to
         * roll back to, e.g. user is the sole contributor. This function
         * performs permissions checks on $user, then calls commitRollback()
         * to do the dirty work
         *
         * @todo Separate the business/permission stuff out from backend code
         * @todo Remove $token parameter. Already verified by RollbackAction and ApiRollback.
         *
         * @param string $fromP Name of the user whose edits to rollback.
         * @param string $summary Custom summary. Set to default summary if empty.
         * @param string $token Rollback token.
         * @param bool $bot If true, mark all reverted edits as bot.
         *
         * @param array &$resultDetails Array contains result-specific array of additional values
         *    'alreadyrolled' : 'current' (rev)
         *    success        : 'summary' (str), 'current' (rev), 'target' (rev)
         *
         * @param User $user The user performing the rollback
         * @param array|null $tags Change tags to apply to the rollback
         * Callers are responsible for permission checks
         * (with ChangeTags::canAddTagsAccompanyingChange)
         *
         * @return array Array of errors, each error formatted as
         *   array(messagekey, param1, param2, ...).
         * On success, the array is empty.  This array can also be passed to
         * OutputPage::showPermissionsErrorPage().
         */
        public function doRollback(
                $fromP, $summary, $token, $bot, &$resultDetails, User $user, $tags = null
        ) {
                $resultDetails = null;

                // Check permissions
                $editErrors = $this->mTitle->getUserPermissionsErrors( 'edit', $user );
                $rollbackErrors = $this->mTitle->getUserPermissionsErrors( 'rollback', $user );
                $errors = array_merge( $editErrors, wfArrayDiff2( $rollbackErrors, $editErrors ) );

                if ( !$user->matchEditToken( $token, 'rollback' ) ) {
                        $errors[] = [ 'sessionfailure' ];
                }

                if ( $user->pingLimiter( 'rollback' ) || $user->pingLimiter() ) {
                        $errors[] = [ 'actionthrottledtext' ];
                }

                // If there were errors, bail out now
                if ( !empty( $errors ) ) {
                        return $errors;
                }

                return $this->commitRollback( $fromP, $summary, $bot, $resultDetails, $user, $tags );
        }

        /**
         * Backend implementation of doRollback(), please refer there for parameter
         * and return value documentation
         *
         * NOTE: This function does NOT check ANY permissions, it just commits the
         * rollback to the DB. Therefore, you should only call this function direct-
         * ly if you want to use custom permissions checks. If you don't, use
         * doRollback() instead.
         * @param string $fromP Name of the user whose edits to rollback.
         * @param string $summary Custom summary. Set to default summary if empty.
         * @param bool $bot If true, mark all reverted edits as bot.
         *
         * @param array &$resultDetails Contains result-specific array of additional values
         * @param User $guser The user performing the rollback
         * @param array|null $tags Change tags to apply to the rollback
         * Callers are responsible for permission checks
         * (with ChangeTags::canAddTagsAccompanyingChange)
         *
         * @return array An array of error messages, as returned by Status::getErrorsArray()
         */
        public function commitRollback( $fromP, $summary, $bot,
                &$resultDetails, User $guser, $tags = null
        ) {
                global $wgUseRCPatrol, $wgContLang;

                $dbw = wfGetDB( DB_MASTER );

                if ( wfReadOnly() ) {
                        return [ [ 'readonlytext' ] ];
                }

                // Begin revision creation cycle by creating a PageUpdater.
                // If the page is changed concurrently after grabParentRevision(), the rollback will fail.
                $updater = $this->newPageUpdater( $guser );
                $current = $updater->grabParentRevision();

                if ( is_null( $current ) ) {
                        // Something wrong... no page?
                        return [ [ 'notanarticle' ] ];
                }

                $currentEditorForPublic = $current->getUser( RevisionRecord::FOR_PUBLIC );
                $legacyCurrent = new Revision( $current );
                $from = str_replace( '_', ' ', $fromP );

                // User name given should match up with the top revision.
                // If the revision's user is not visible, then $from should be empty.
                if ( $from !== ( $currentEditorForPublic ? $currentEditorForPublic->getName() : '' ) ) {
                        $resultDetails = [ 'current' => $legacyCurrent ];
                        return [ [ 'alreadyrolled',
                                htmlspecialchars( $this->mTitle->getPrefixedText() ),
                                htmlspecialchars( $fromP ),
                                htmlspecialchars( $currentEditorForPublic ? $currentEditorForPublic->getName() : '' )
                        ] ];
                }

                // Get the last edit not by this person...
                // Note: these may not be public values
                $actorWhere = ActorMigration::newMigration()->getWhere(
                        $dbw,
                        'rev_user',
                        $current->getUser( RevisionRecord::RAW )
                );

                $s = $dbw->selectRow(
                        [ 'revision' ] + $actorWhere['tables'],
                        [ 'rev_id', 'rev_timestamp', 'rev_deleted' ],
                        [
                                'rev_page' => $current->getPageId(),
                                'NOT(' . $actorWhere['conds'] . ')',
                        ],
                        __METHOD__,
                        [
                                'USE INDEX' => [ 'revision' => 'page_timestamp' ],
                                'ORDER BY' => 'rev_timestamp DESC'
                        ],
                        $actorWhere['joins']
                );
                if ( $s === false ) {
                        // No one else ever edited this page
                        return [ [ 'cantrollback' ] ];
                } elseif ( $s->rev_deleted & RevisionRecord::DELETED_TEXT
                        || $s->rev_deleted & RevisionRecord::DELETED_USER
                ) {
                        // Only admins can see this text
                        return [ [ 'notvisiblerev' ] ];
                }

                // Generate the edit summary if necessary
                $target = $this->getRevisionStore()->getRevisionById(
                        $s->rev_id,
                        RevisionStore::READ_LATEST
                );
                if ( empty( $summary ) ) {
                        if ( !$currentEditorForPublic ) { // no public user name
                                $summary = wfMessage( 'revertpage-nouser' );
                        } else {
                                $summary = wfMessage( 'revertpage' );
                        }
                }
                $legacyTarget = new Revision( $target );
                $targetEditorForPublic = $target->getUser( RevisionRecord::FOR_PUBLIC );

                // Allow the custom summary to use the same args as the default message
                $args = [
                        $targetEditorForPublic ? $targetEditorForPublic->getName() : null,
                        $currentEditorForPublic ? $currentEditorForPublic->getName() : null,
                        $s->rev_id,
                        $wgContLang->timeanddate( wfTimestamp( TS_MW, $s->rev_timestamp ) ),
                        $current->getId(),
                        $wgContLang->timeanddate( $current->getTimestamp() )
                ];
                if ( $summary instanceof Message ) {
                        $summary = $summary->params( $args )->inContentLanguage()->text();
                } else {
                        $summary = wfMsgReplaceArgs( $summary, $args );
                }

                // Trim spaces on user supplied text
                $summary = trim( $summary );

                // Save
                $flags = EDIT_UPDATE | EDIT_INTERNAL;

                if ( $guser->isAllowed( 'minoredit' ) ) {
                        $flags |= EDIT_MINOR;
                }

                if ( $bot && ( $guser->isAllowedAny( 'markbotedits', 'bot' ) ) ) {
                        $flags |= EDIT_FORCE_BOT;
                }

                // TODO: MCR: also log model changes in other slots, in case that becomes possible!
                $currentContent = $current->getContent( 'main' );
                $targetContent = $target->getContent( 'main' );
                $changingContentModel = $targetContent->getModel() !== $currentContent->getModel();

                if ( in_array( 'mw-rollback', ChangeTags::getSoftwareTags() ) ) {
                        $tags[] = 'mw-rollback';
                }

                // Build rollback revision:
                // Restore old content
                // TODO: MCR: test this once we can store multiple slots
                foreach ( $target->getSlots()->getSlots() as $slot ) {
                        $updater->inheritSlot( $slot );
                }

                // Remove extra slots
                // TODO: MCR: test this once we can store multiple slots
                foreach ( $current->getSlotRoles() as $role ) {
                        if ( !$target->hasSlot( $role ) ) {
                                $updater->removeSlot( $role );
                        }
                }

                $updater->setOriginalRevisionId( $target->getId() );
                $updater->setUndidRevisionId( $current->getId() );
                $updater->addTags( $tags );

                // Actually store the rollback
                $rev = $updater->saveRevision(
                        CommentStoreComment::newUnsavedComment( $summary ),
                        $flags
                );

                // Set patrolling and bot flag on the edits, which gets rollbacked.
                // This is done even on edit failure to have patrolling in that case (T64157).
                $set = [];
                if ( $bot && $guser->isAllowed( 'markbotedits' ) ) {
                        // Mark all reverted edits as bot
                        $set['rc_bot'] = 1;
                }

                if ( $wgUseRCPatrol ) {
                        // Mark all reverted edits as patrolled
                        $set['rc_patrolled'] = RecentChange::PRC_PATROLLED;
                }

                if ( count( $set ) ) {
                        $actorWhere = ActorMigration::newMigration()->getWhere(
                                $dbw,
                                'rc_user',
                                $current->getUser( RevisionRecord::RAW ),
                                false
                        );
                        $dbw->update( 'recentchanges', $set,
                                [ /* WHERE */
                                        'rc_cur_id' => $current->getPageId(),
                                        'rc_timestamp > ' . $dbw->addQuotes( $s->rev_timestamp ),
                                        $actorWhere['conds'], // No tables/joins are needed for rc_user
                                ],
                                __METHOD__
                        );
                }

                if ( !$updater->wasSuccessful() ) {
                        return $updater->getStatus()->getErrorsArray();
                }

                // Report if the edit was not created because it did not change the content.
                if ( $updater->isUnchanged() ) {
                        $resultDetails = [ 'current' => $legacyCurrent ];
                        return [ [ 'alreadyrolled',
                                        htmlspecialchars( $this->mTitle->getPrefixedText() ),
                                        htmlspecialchars( $fromP ),
                                        htmlspecialchars( $targetEditorForPublic ? $targetEditorForPublic->getName() : '' )
                        ] ];
                }

                if ( $changingContentModel ) {
                        // If the content model changed during the rollback,
                        // make sure it gets logged to Special:Log/contentmodel
                        $log = new ManualLogEntry( 'contentmodel', 'change' );
                        $log->setPerformer( $guser );
                        $log->setTarget( $this->mTitle );
                        $log->setComment( $summary );
                        $log->setParameters( [
                                '4::oldmodel' => $currentContent->getModel(),
                                '5::newmodel' => $targetContent->getModel(),
                        ] );

                        $logId = $log->insert( $dbw );
                        $log->publish( $logId );
                }

                $revId = $rev->getId();

                Hooks::run( 'ArticleRollbackComplete', [ $this, $guser, $legacyTarget, $legacyCurrent ] );

                $resultDetails = [
                        'summary' => $summary,
                        'current' => $legacyCurrent,
                        'target' => $legacyTarget,
                        'newid' => $revId,
                        'tags' => $tags
                ];

                // TODO: make this return a Status object and wrap $resultDetails in that.
                return [];
        }

        /**
         * The onArticle*() functions are supposed to be a kind of hooks
         * which should be called whenever any of the specified actions
         * are done.
         *
         * This is a good place to put code to clear caches, for instance.
         *
         * This is called on page move and undelete, as well as edit
         *
         * @param Title $title
         */
        public static function onArticleCreate( Title $title ) {
                // TODO: move this into a PageEventEmitter service

                // Update existence markers on article/talk tabs...
                $other = $title->getOtherPage();

                $other->purgeSquid();

                $title->touchLinks();
                $title->purgeSquid();
                $title->deleteTitleProtection();

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

                // Invalidate caches of articles which include this page
                DeferredUpdates::addUpdate(
                        new HTMLCacheUpdate( $title, 'templatelinks', 'page-create' )
                );

                if ( $title->getNamespace() == NS_CATEGORY ) {
                        // Load the Category object, which will schedule a job to create
                        // the category table row if necessary. Checking a replica DB is ok
                        // here, in the worst case it'll run an unnecessary recount job on
                        // a category that probably doesn't have many members.
                        Category::newFromTitle( $title )->getID();
                }
        }

        /**
         * Clears caches when article is deleted
         *
         * @param Title $title
         */
        public static function onArticleDelete( Title $title ) {
                // TODO: move this into a PageEventEmitter service

                // Update existence markers on article/talk tabs...
                // Clear Backlink cache first so that purge jobs use more up-to-date backlink information
                BacklinkCache::get( $title )->clear();
                $other = $title->getOtherPage();

                $other->purgeSquid();

                $title->touchLinks();
                $title->purgeSquid();

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

                // File cache
                HTMLFileCache::clearFileCache( $title );
                InfoAction::invalidateCache( $title );

                // Messages
                if ( $title->getNamespace() == NS_MEDIAWIKI ) {
                        MessageCache::singleton()->updateMessageOverride( $title, null );
                }

                // Images
                if ( $title->getNamespace() == NS_FILE ) {
                        DeferredUpdates::addUpdate(
                                new HTMLCacheUpdate( $title, 'imagelinks', 'page-delete' )
                        );
                }

                // User talk pages
                if ( $title->getNamespace() == NS_USER_TALK ) {
                        $user = User::newFromName( $title->getText(), false );
                        if ( $user ) {
                                $user->setNewtalk( false );
                        }
                }

                // Image redirects
                RepoGroup::singleton()->getLocalRepo()->invalidateImageRedirect( $title );
        }

        /**
         * Purge caches on page update etc
         *
         * @param Title $title
         * @param Revision|null $revision Revision that was just saved, may be null
         * @param string[]|null $slotsChanged The role names of the slots that were changed.
         *        If not given, all slots are assumed to have changed.
         */
        public static function onArticleEdit(
                Title $title,
                Revision $revision = null,
                $slotsChanged = null
        ) {
                // TODO: move this into a PageEventEmitter service

                if ( $slotsChanged === null || in_array( 'main',  $slotsChanged ) ) {
                        // Invalidate caches of articles which include this page.
                        // Only for the main slot, because only the main slot is transcluded.
                        // TODO: MCR: not true for TemplateStyles! [SlotHandler]
                        DeferredUpdates::addUpdate(
                                new HTMLCacheUpdate( $title, 'templatelinks', 'page-edit' )
                        );
                }

                // Invalidate the caches of all pages which redirect here
                DeferredUpdates::addUpdate(
                        new HTMLCacheUpdate( $title, 'redirect', 'page-edit' )
                );

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

                // Purge CDN for this page only
                $title->purgeSquid();
                // Clear file cache for this page only
                HTMLFileCache::clearFileCache( $title );

                $revid = $revision ? $revision->getId() : null;
                DeferredUpdates::addCallableUpdate( function () use ( $title, $revid ) {
                        InfoAction::invalidateCache( $title, $revid );
                } );
        }

        /**#@-*/

        /**
         * Returns a list of categories this page is a member of.
         * Results will include hidden categories
         *
         * @return TitleArray
         */
        public function getCategories() {
                $id = $this->getId();
                if ( $id == 0 ) {
                        return TitleArray::newFromResult( new FakeResultWrapper( [] ) );
                }

                $dbr = wfGetDB( DB_REPLICA );
                $res = $dbr->select( 'categorylinks',
                        [ 'cl_to AS page_title, ' . NS_CATEGORY . ' AS page_namespace' ],
                        // Have to do that since Database::fieldNamesWithAlias treats numeric indexes
                        // as not being aliases, and NS_CATEGORY is numeric
                        [ 'cl_from' => $id ],
                        __METHOD__ );

                return TitleArray::newFromResult( $res );
        }

        /**
         * Returns a list of hidden categories this page is a member of.
         * Uses the page_props and categorylinks tables.
         *
         * @return array Array of Title objects
         */
        public function getHiddenCategories() {
                $result = [];
                $id = $this->getId();

                if ( $id == 0 ) {
                        return [];
                }

                $dbr = wfGetDB( DB_REPLICA );
                $res = $dbr->select( [ 'categorylinks', 'page_props', 'page' ],
                        [ 'cl_to' ],
                        [ 'cl_from' => $id, 'pp_page=page_id', 'pp_propname' => 'hiddencat',
                                'page_namespace' => NS_CATEGORY, 'page_title=cl_to' ],
                        __METHOD__ );

                if ( $res !== false ) {
                        foreach ( $res as $row ) {
                                $result[] = Title::makeTitle( NS_CATEGORY, $row->cl_to );
                        }
                }

                return $result;
        }

        /**
         * Auto-generates a deletion reason
         *
         * @param bool &$hasHistory Whether the page has a history
         * @return string|bool String containing deletion reason or empty string, or boolean false
         *    if no revision occurred
         */
        public function getAutoDeleteReason( &$hasHistory ) {
                return $this->getContentHandler()->getAutoDeleteReason( $this->getTitle(), $hasHistory );
        }

        /**
         * Update all the appropriate counts in the category table, given that
         * we've added the categories $added and deleted the categories $deleted.
         *
         * This should only be called from deferred updates or jobs to avoid contention.
         *
         * @param array $added The names of categories that were added
         * @param array $deleted The names of categories that were deleted
         * @param int $id Page ID (this should be the original deleted page ID)
         */
        public function updateCategoryCounts( array $added, array $deleted, $id = 0 ) {
                $id = $id ?: $this->getId();
                $ns = $this->getTitle()->getNamespace();

                $addFields = [ 'cat_pages = cat_pages + 1' ];
                $removeFields = [ 'cat_pages = cat_pages - 1' ];
                if ( $ns == NS_CATEGORY ) {
                        $addFields[] = 'cat_subcats = cat_subcats + 1';
                        $removeFields[] = 'cat_subcats = cat_subcats - 1';
                } elseif ( $ns == NS_FILE ) {
                        $addFields[] = 'cat_files = cat_files + 1';
                        $removeFields[] = 'cat_files = cat_files - 1';
                }

                $dbw = wfGetDB( DB_MASTER );

                if ( count( $added ) ) {
                        $existingAdded = $dbw->selectFieldValues(
                                'category',
                                'cat_title',
                                [ 'cat_title' => $added ],
                                __METHOD__
                        );

                        // For category rows that already exist, do a plain
                        // UPDATE instead of INSERT...ON DUPLICATE KEY UPDATE
                        // to avoid creating gaps in the cat_id sequence.
                        if ( count( $existingAdded ) ) {
                                $dbw->update(
                                        'category',
                                        $addFields,
                                        [ 'cat_title' => $existingAdded ],
                                        __METHOD__
                                );
                        }

                        $missingAdded = array_diff( $added, $existingAdded );
                        if ( count( $missingAdded ) ) {
                                $insertRows = [];
                                foreach ( $missingAdded as $cat ) {
                                        $insertRows[] = [
                                                'cat_title'   => $cat,
                                                'cat_pages'   => 1,
                                                'cat_subcats' => ( $ns == NS_CATEGORY ) ? 1 : 0,
                                                'cat_files'   => ( $ns == NS_FILE ) ? 1 : 0,
                                        ];
                                }
                                $dbw->upsert(
                                        'category',
                                        $insertRows,
                                        [ 'cat_title' ],
                                        $addFields,
                                        __METHOD__
                                );
                        }
                }

                if ( count( $deleted ) ) {
                        $dbw->update(
                                'category',
                                $removeFields,
                                [ 'cat_title' => $deleted ],
                                __METHOD__
                        );
                }

                foreach ( $added as $catName ) {
                        $cat = Category::newFromName( $catName );
                        Hooks::run( 'CategoryAfterPageAdded', [ $cat, $this ] );
                }

                foreach ( $deleted as $catName ) {
                        $cat = Category::newFromName( $catName );
                        Hooks::run( 'CategoryAfterPageRemoved', [ $cat, $this, $id ] );
                }

                // Refresh counts on categories that should be empty now
                if ( count( $deleted ) ) {
                        $rows = $dbw->select(
                                'category',
                                [ 'cat_id', 'cat_title', 'cat_pages', 'cat_subcats', 'cat_files' ],
                                [ 'cat_title' => $deleted, 'cat_pages <= 100' ],
                                __METHOD__
                        );
                        foreach ( $rows as $row ) {
                                $cat = Category::newFromRow( $row );
                                // T166757: do the update after this DB commit
                                DeferredUpdates::addCallableUpdate( function () use ( $cat ) {
                                        $cat->refreshCounts();
                                } );
                        }
                }
        }

        /**
         * Opportunistically enqueue link update jobs given fresh parser output if useful
         *
         * @param ParserOutput $parserOutput Current version page output
         * @since 1.25
         */
        public function triggerOpportunisticLinksUpdate( ParserOutput $parserOutput ) {
                if ( wfReadOnly() ) {
                        return;
                }

                if ( !Hooks::run( 'OpportunisticLinksUpdate',
                        [ $this, $this->mTitle, $parserOutput ]
                ) ) {
                        return;
                }

                $config = RequestContext::getMain()->getConfig();

                $params = [
                        'isOpportunistic' => true,
                        'rootJobTimestamp' => $parserOutput->getCacheTime()
                ];

                if ( $this->mTitle->areRestrictionsCascading() ) {
                        // If the page is cascade protecting, the links should really be up-to-date
                        JobQueueGroup::singleton()->lazyPush(
                                RefreshLinksJob::newPrioritized( $this->mTitle, $params )
                        );
                } elseif ( !$config->get( 'MiserMode' ) && $parserOutput->hasDynamicContent() ) {
                        // Assume the output contains "dynamic" time/random based magic words.
                        // Only update pages that expired due to dynamic content and NOT due to edits
                        // to referenced templates/files. When the cache expires due to dynamic content,
                        // page_touched is unchanged. We want to avoid triggering redundant jobs due to
                        // views of pages that were just purged via HTMLCacheUpdateJob. In that case, the
                        // template/file edit already triggered recursive RefreshLinksJob jobs.
                        if ( $this->getLinksTimestamp() > $this->getTouched() ) {
                                // If a page is uncacheable, do not keep spamming a job for it.
                                // Although it would be de-duplicated, it would still waste I/O.
                                $cache = ObjectCache::getLocalClusterInstance();
                                $key = $cache->makeKey( 'dynamic-linksupdate', 'last', $this->getId() );
                                $ttl = max( $parserOutput->getCacheExpiry(), 3600 );
                                if ( $cache->add( $key, time(), $ttl ) ) {
                                        JobQueueGroup::singleton()->lazyPush(
                                                RefreshLinksJob::newDynamic( $this->mTitle, $params )
                                        );
                                }
                        }
                }
        }

        /**
         * Returns a list of updates to be performed when this page is deleted. The
         * updates should remove any information about this page from secondary data
         * stores such as links tables.
         *
         * @param Content|null $content Optional Content object for determining the
         *   necessary updates.
         * @return DeferrableUpdate[]
         */
        public function getDeletionUpdates( Content $content = null ) {
                if ( !$content ) {
                        // load content object, which may be used to determine the necessary updates.
                        // XXX: the content may not be needed to determine the updates.
                        try {
                                $content = $this->getContent( Revision::RAW );
                        } catch ( Exception $ex ) {
                                // If we can't load the content, something is wrong. Perhaps that's why
                                // the user is trying to delete the page, so let's not fail in that case.
                                // Note that doDeleteArticleReal() will already have logged an issue with
                                // loading the content.
                        }
                }

                if ( !$content ) {
                        $updates = [];
                } else {
                        $updates = $content->getDeletionUpdates( $this );
                }

                Hooks::run( 'WikiPageDeletionUpdates', [ $this, $content, &$updates ] );
                return $updates;
        }

        /**
         * Whether this content displayed on this page
         * comes from the local database
         *
         * @since 1.28
         * @return bool
         */
        public function isLocal() {
                return true;
        }

        /**
         * The display name for the site this content
         * come from. If a subclass overrides isLocal(),
         * this could return something other than the
         * current site name
         *
         * @since 1.28
         * @return string
         */
        public function getWikiDisplayName() {
                global $wgSitename;
                return $wgSitename;
        }

        /**
         * Get the source URL for the content on this page,
         * typically the canonical URL, but may be a remote
         * link if the content comes from another site
         *
         * @since 1.28
         * @return string
         */
        public function getSourceURL() {
                return $this->getTitle()->getCanonicalURL();
        }

        /**
         * @param WANObjectCache $cache
         * @return string[]
         * @since 1.28
         */
        public function getMutableCacheKeys( WANObjectCache $cache ) {
                $linkCache = MediaWikiServices::getInstance()->getLinkCache();

                return $linkCache->getMutableCacheKeys( $cache, $this->getTitle()->getTitleValue() );
        }

}