Merge "StringUtils: Add a utility for checking if a string is a valid regex"

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

<?php
/**
 * User interface for page actions.
 *
 * 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\Block\DatabaseBlock;
use MediaWiki\MediaWikiServices;
use MediaWiki\Revision\MutableRevisionRecord;
use MediaWiki\Revision\RevisionRecord;
use MediaWiki\Revision\SlotRecord;

/**
 * Class for viewing MediaWiki article and history.
 *
 * This maintains WikiPage functions for backwards compatibility.
 *
 * @todo Move and rewrite code to an Action class
 *
 * Note: edit user interface and cache support functions have been
 * moved to separate EditPage and HTMLFileCache classes.
 */
class Article implements Page {
        /**
         * @var IContextSource|null The context this Article is executed in.
         * If null, RequestContext::getMain() is used.
         */
        protected $mContext;

        /** @var WikiPage|null The WikiPage object of this instance */
        protected $mPage;

        /**
         * @var ParserOptions|null ParserOptions object for $wgUser articles.
         * Initialized by getParserOptions by calling $this->mPage->makeParserOptions().
         */
        public $mParserOptions;

        /**
         * @var Content|null Content of the main slot of $this->mRevision.
         * @note This variable is read only, setting it has no effect.
         *       Extensions that wish to override the output of Article::view should use a hook.
         * @todo MCR: Remove in 1.33
         * @deprecated since 1.32
         * @since 1.21
         */
        public $mContentObject;

        /**
         * @var bool Is the target revision loaded? Set by fetchRevisionRecord().
         *
         * @deprecated since 1.32. Whether content has been loaded should not be relevant to
         * code outside this class.
         */
        public $mContentLoaded = false;

        /**
         * @var int|null The oldid of the article that was requested to be shown,
         * 0 for the current revision.
         * @see $mRevIdFetched
         */
        public $mOldId;

        /** @var Title|null Title from which we were redirected here, if any. */
        public $mRedirectedFrom = null;

        /** @var string|bool URL to redirect to or false if none */
        public $mRedirectUrl = false;

        /**
         * @var int Revision ID of revision that was loaded.
         * @see $mOldId
         * @deprecated since 1.32, use getRevIdFetched() instead.
         */
        public $mRevIdFetched = 0;

        /**
         * @var Status|null represents the outcome of fetchRevisionRecord().
         * $fetchResult->value is the RevisionRecord object, if the operation was successful.
         *
         * The information in $fetchResult is duplicated by the following deprecated public fields:
         * $mRevIdFetched, $mContentLoaded. $mRevision (and $mContentObject) also typically duplicate
         * information of the loaded revision, but may be overwritten by extensions or due to errors.
         */
        private $fetchResult = null;

        /**
         * @var Revision|null Revision to be shown. Initialized by getOldIDFromRequest()
         * or fetchContentObject(). Normally loaded from the database, but may be replaced
         * by an extension, or be a fake representing an error message or some such.
         * While the output of Article::view is typically based on this revision,
         * it may be overwritten by error messages or replaced by extensions.
         */
        public $mRevision = null;

        /**
         * @var ParserOutput|null|false The ParserOutput generated for viewing the page,
         * initialized by view(). If no ParserOutput could be generated, this is set to false.
         * @deprecated since 1.32
         */
        public $mParserOutput = null;

        /**
         * @var bool Whether render() was called. With the way subclasses work
         * here, there doesn't seem to be any other way to stop calling
         * OutputPage::enableSectionEditLinks() and still have it work as it did before.
         */
        protected $viewIsRenderAction = false;

        /**
         * Constructor and clear the article
         * @param Title $title Reference to a Title object.
         * @param int|null $oldId Revision ID, null to fetch from request, zero for current
         */
        public function __construct( Title $title, $oldId = null ) {
                $this->mOldId = $oldId;
                $this->mPage = $this->newPage( $title );
        }

        /**
         * @param Title $title
         * @return WikiPage
         */
        protected function newPage( Title $title ) {
                return new WikiPage( $title );
        }

        /**
         * Constructor from a page id
         * @param int $id Article ID to load
         * @return Article|null
         */
        public static function newFromID( $id ) {
                $t = Title::newFromID( $id );
                return $t == null ? null : new static( $t );
        }

        /**
         * Create an Article object of the appropriate class for the given page.
         *
         * @param Title $title
         * @param IContextSource $context
         * @return Article
         */
        public static function newFromTitle( $title, IContextSource $context ) {
                if ( NS_MEDIA == $title->getNamespace() ) {
                        // XXX: This should not be here, but where should it go?
                        $title = Title::makeTitle( NS_FILE, $title->getDBkey() );
                }

                $page = null;
                Hooks::run( 'ArticleFromTitle', [ &$title, &$page, $context ] );
                if ( !$page ) {
                        switch ( $title->getNamespace() ) {
                                case NS_FILE:
                                        $page = new ImagePage( $title );
                                        break;
                                case NS_CATEGORY:
                                        $page = new CategoryPage( $title );
                                        break;
                                default:
                                        $page = new Article( $title );
                        }
                }
                $page->setContext( $context );

                return $page;
        }

        /**
         * Create an Article object of the appropriate class for the given page.
         *
         * @param WikiPage $page
         * @param IContextSource $context
         * @return Article
         */
        public static function newFromWikiPage( WikiPage $page, IContextSource $context ) {
                $article = self::newFromTitle( $page->getTitle(), $context );
                $article->mPage = $page; // override to keep process cached vars
                return $article;
        }

        /**
         * Get the page this view was redirected from
         * @return Title|null
         * @since 1.28
         */
        public function getRedirectedFrom() {
                return $this->mRedirectedFrom;
        }

        /**
         * Tell the page view functions that this view was redirected
         * from another page on the wiki.
         * @param Title $from
         */
        public function setRedirectedFrom( Title $from ) {
                $this->mRedirectedFrom = $from;
        }

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

        /**
         * Get the WikiPage object of this instance
         *
         * @since 1.19
         * @return WikiPage
         */
        public function getPage() {
                return $this->mPage;
        }

        /**
         * Clear the object
         */
        public function clear() {
                $this->mContentLoaded = false;

                $this->mRedirectedFrom = null; # Title object if set
                $this->mRevIdFetched = 0;
                $this->mRedirectUrl = false;
                $this->mRevision = null;
                $this->mContentObject = null;
                $this->fetchResult = null;

                // TODO hard-deprecate direct access to public fields

                $this->mPage->clear();
        }

        /**
         * Returns a Content object representing the pages effective display content,
         * not necessarily the revision's content!
         *
         * Note that getContent does not follow redirects anymore.
         * If you need to fetch redirectable content easily, try
         * the shortcut in WikiPage::getRedirectTarget()
         *
         * This function has side effects! Do not use this function if you
         * only want the real revision text if any.
         *
         * @deprecated since 1.32, use getRevisionFetched() or fetchRevisionRecord() instead.
         *
         * @return Content
         *
         * @since 1.21
         */
        protected function getContentObject() {
                if ( $this->mPage->getId() === 0 ) {
                        $content = $this->getSubstituteContent();
                } else {
                        $this->fetchContentObject();
                        $content = $this->mContentObject;
                }

                return $content;
        }

        /**
         * Returns Content object to use when the page does not exist.
         *
         * @return Content
         */
        private function getSubstituteContent() {
                # If this is a MediaWiki:x message, then load the messages
                # and return the message value for x.
                if ( $this->getTitle()->getNamespace() == NS_MEDIAWIKI ) {
                        $text = $this->getTitle()->getDefaultMessageText();
                        if ( $text === false ) {
                                $text = '';
                        }

                        $content = ContentHandler::makeContent( $text, $this->getTitle() );
                } else {
                        $message = $this->getContext()->getUser()->isLoggedIn() ? 'noarticletext' : 'noarticletextanon';
                        $content = new MessageContent( $message, null );
                }

                return $content;
        }

        /**
         * Returns ParserOutput to use when a page does not exist. In some cases, we still want to show
         * "virtual" content, e.g. in the MediaWiki namespace, or in the File namespace for non-local
         * files.
         *
         * @param ParserOptions $options
         *
         * @return ParserOutput
         */
        protected function getEmptyPageParserOutput( ParserOptions $options ) {
                $content = $this->getSubstituteContent();

                return $content->getParserOutput( $this->getTitle(), 0, $options );
        }

        /**
         * @see getOldIDFromRequest()
         * @see getRevIdFetched()
         *
         * @return int The oldid of the article that is was requested in the constructor or via the
         *         context's WebRequest.
         */
        public function getOldID() {
                if ( is_null( $this->mOldId ) ) {
                        $this->mOldId = $this->getOldIDFromRequest();
                }

                return $this->mOldId;
        }

        /**
         * Sets $this->mRedirectUrl to a correct URL if the query parameters are incorrect
         *
         * @return int The old id for the request
         */
        public function getOldIDFromRequest() {
                $this->mRedirectUrl = false;

                $request = $this->getContext()->getRequest();
                $oldid = $request->getIntOrNull( 'oldid' );

                if ( $oldid === null ) {
                        return 0;
                }

                if ( $oldid !== 0 ) {
                        # Load the given revision and check whether the page is another one.
                        # In that case, update this instance to reflect the change.
                        if ( $oldid === $this->mPage->getLatest() ) {
                                $this->mRevision = $this->mPage->getRevision();
                        } else {
                                $this->mRevision = Revision::newFromId( $oldid );
                                if ( $this->mRevision !== null ) {
                                        // Revision title doesn't match the page title given?
                                        if ( $this->mPage->getId() != $this->mRevision->getPage() ) {
                                                $function = get_class( $this->mPage ) . '::newFromID';
                                                $this->mPage = $function( $this->mRevision->getPage() );
                                        }
                                }
                        }
                }

                $rl = MediaWikiServices::getInstance()->getRevisionLookup();
                $oldRev = $this->mRevision ? $this->mRevision->getRevisionRecord() : null;
                if ( $request->getVal( 'direction' ) == 'next' ) {
                        $nextid = 0;
                        if ( $oldRev ) {
                                $nextRev = $rl->getNextRevision( $oldRev );
                                if ( $nextRev ) {
                                        $nextid = $nextRev->getId();
                                }
                        }
                        if ( $nextid ) {
                                $oldid = $nextid;
                                $this->mRevision = null;
                        } else {
                                $this->mRedirectUrl = $this->getTitle()->getFullURL( 'redirect=no' );
                        }
                } elseif ( $request->getVal( 'direction' ) == 'prev' ) {
                        $previd = 0;
                        if ( $oldRev ) {
                                $prevRev = $rl->getPreviousRevision( $oldRev );
                                if ( $prevRev ) {
                                        $previd = $prevRev->getId();
                                }
                        }
                        if ( $previd ) {
                                $oldid = $previd;
                                $this->mRevision = null;
                        }
                }

                $this->mRevIdFetched = $this->mRevision ? $this->mRevision->getId() : 0;

                return $oldid;
        }

        /**
         * Get text content object
         * Does *NOT* follow redirects.
         * @todo When is this null?
         * @deprecated since 1.32, use fetchRevisionRecord() instead.
         *
         * @note Code that wants to retrieve page content from the database should
         * use WikiPage::getContent().
         *
         * @return Content|null|bool
         *
         * @since 1.21
         */
        protected function fetchContentObject() {
                if ( !$this->mContentLoaded ) {
                        $this->fetchRevisionRecord();
                }

                return $this->mContentObject;
        }

        /**
         * Fetches the revision to work on.
         * The revision is typically loaded from the database, but may also be a fake representing
         * an error message or content supplied by an extension. Refer to $this->fetchResult for
         * the revision actually loaded from the database, and any errors encountered while doing
         * that.
         *
         * @return RevisionRecord|null
         */
        protected function fetchRevisionRecord() {
                if ( $this->fetchResult ) {
                        return $this->mRevision ? $this->mRevision->getRevisionRecord() : null;
                }

                $this->mContentLoaded = true;
                $this->mContentObject = null;

                $oldid = $this->getOldID();

                // $this->mRevision might already be fetched by getOldIDFromRequest()
                if ( !$this->mRevision ) {
                        if ( !$oldid ) {
                                $this->mRevision = $this->mPage->getRevision();

                                if ( !$this->mRevision ) {
                                        wfDebug( __METHOD__ . " failed to find page data for title " .
                                                $this->getTitle()->getPrefixedText() . "\n" );

                                        // Just for sanity, output for this case is done by showMissingArticle().
                                        $this->fetchResult = Status::newFatal( 'noarticletext' );
                                        $this->applyContentOverride( $this->makeFetchErrorContent() );
                                        return null;
                                }
                        } else {
                                $this->mRevision = Revision::newFromId( $oldid );

                                if ( !$this->mRevision ) {
                                        wfDebug( __METHOD__ . " failed to load revision, rev_id $oldid\n" );

                                        $this->fetchResult = Status::newFatal( 'missing-revision', $oldid );
                                        $this->applyContentOverride( $this->makeFetchErrorContent() );
                                        return null;
                                }
                        }
                }

                $this->mRevIdFetched = $this->mRevision->getId();
                $this->fetchResult = Status::newGood( $this->mRevision );

                if (
                        !$this->mRevision->userCan( RevisionRecord::DELETED_TEXT, $this->getContext()->getUser() )
                ) {
                        wfDebug( __METHOD__ . " failed to retrieve content of revision " .
                                $this->mRevision->getId() . "\n" );

                        // Just for sanity, output for this case is done by showDeletedRevisionHeader().
                        $this->fetchResult = Status::newFatal( 'rev-deleted-text-permission' );
                        $this->applyContentOverride( $this->makeFetchErrorContent() );
                        return null;
                }

                if ( Hooks::isRegistered( 'ArticleAfterFetchContentObject' ) ) {
                        $contentObject = $this->mRevision->getContent(
                                RevisionRecord::FOR_THIS_USER,
                                $this->getContext()->getUser()
                        );

                        $hookContentObject = $contentObject;

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

                        Hooks::run(
                                'ArticleAfterFetchContentObject',
                                [ &$articlePage, &$hookContentObject ],
                                '1.32'
                        );

                        if ( $hookContentObject !== $contentObject ) {
                                // A hook handler is trying to override the content
                                $this->applyContentOverride( $hookContentObject );
                        }
                }

                // For B/C only
                $this->mContentObject = $this->mRevision->getContent(
                        RevisionRecord::FOR_THIS_USER,
                        $this->getContext()->getUser()
                );

                return $this->mRevision->getRevisionRecord();
        }

        /**
         * Returns a Content object representing any error in $this->fetchContent, or null
         * if there is no such error.
         *
         * @return Content|null
         */
        private function makeFetchErrorContent() {
                if ( !$this->fetchResult || $this->fetchResult->isOK() ) {
                        return null;
                }

                return new MessageContent( $this->fetchResult->getMessage() );
        }

        /**
         * Applies a content override by constructing a fake Revision object and assigning
         * it to mRevision. The fake revision will not have a user, timestamp or summary set.
         *
         * This mechanism exists mainly to accommodate extensions that use the
         * ArticleAfterFetchContentObject. Once that hook has been removed, there should no longer
         * be a need for a fake revision object. fetchRevisionRecord() presently also uses this mechanism
         * to report errors, but that could be changed to use $this->fetchResult instead.
         *
         * @param Content $override Content to be used instead of the actual page content,
         *        coming from an extension or representing an error message.
         */
        private function applyContentOverride( Content $override ) {
                // Construct a fake revision
                $rev = new MutableRevisionRecord( $this->getTitle() );
                $rev->setContent( SlotRecord::MAIN, $override );

                $this->mRevision = new Revision( $rev );

                // For B/C only
                $this->mContentObject = $override;
        }

        /**
         * Returns true if the currently-referenced revision is the current edit
         * to this page (and it exists).
         * @return bool
         */
        public function isCurrent() {
                # If no oldid, this is the current version.
                if ( $this->getOldID() == 0 ) {
                        return true;
                }

                return $this->mPage->exists() && $this->mRevision && $this->mRevision->isCurrent();
        }

        /**
         * Get the fetched Revision object depending on request parameters or null
         * on failure. The revision returned may be a fake representing an error message or
         * wrapping content supplied by an extension. Refer to $this->fetchResult for the
         * revision actually loaded from the database.
         *
         * @since 1.19
         * @return Revision|null
         */
        public function getRevisionFetched() {
                $this->fetchRevisionRecord();

                if ( $this->fetchResult->isOK() ) {
                        return $this->mRevision;
                }
        }

        /**
         * Use this to fetch the rev ID used on page views
         *
         * Before fetchRevisionRecord was called, this returns the page's latest revision,
         * regardless of what getOldID() returns.
         *
         * @return int Revision ID of last article revision
         */
        public function getRevIdFetched() {
                if ( $this->fetchResult && $this->fetchResult->isOK() ) {
                        return $this->fetchResult->value->getId();
                } else {
                        return $this->mPage->getLatest();
                }
        }

        /**
         * This is the default action of the index.php entry point: just view the
         * page of the given title.
         */
        public function view() {
                global $wgUseFileCache;

                # Get variables from query string
                # As side effect this will load the revision and update the title
                # in a revision ID is passed in the request, so this should remain
                # the first call of this method even if $oldid is used way below.
                $oldid = $this->getOldID();

                $user = $this->getContext()->getUser();
                # Another whitelist check in case getOldID() is altering the title
                $permErrors = $this->getTitle()->getUserPermissionsErrors( 'read', $user );
                if ( count( $permErrors ) ) {
                        wfDebug( __METHOD__ . ": denied on secondary read check\n" );
                        throw new PermissionsError( 'read', $permErrors );
                }

                $outputPage = $this->getContext()->getOutput();
                # getOldID() may as well want us to redirect somewhere else
                if ( $this->mRedirectUrl ) {
                        $outputPage->redirect( $this->mRedirectUrl );
                        wfDebug( __METHOD__ . ": redirecting due to oldid\n" );

                        return;
                }

                # If we got diff in the query, we want to see a diff page instead of the article.
                if ( $this->getContext()->getRequest()->getCheck( 'diff' ) ) {
                        wfDebug( __METHOD__ . ": showing diff page\n" );
                        $this->showDiffPage();

                        return;
                }

                # Set page title (may be overridden by DISPLAYTITLE)
                $outputPage->setPageTitle( $this->getTitle()->getPrefixedText() );

                $outputPage->setArticleFlag( true );
                # Allow frames by default
                $outputPage->allowClickjacking();

                $parserCache = MediaWikiServices::getInstance()->getParserCache();

                $parserOptions = $this->getParserOptions();
                $poOptions = [];
                # Render printable version, use printable version cache
                if ( $outputPage->isPrintable() ) {
                        $parserOptions->setIsPrintable( true );
                        $poOptions['enableSectionEditLinks'] = false;
                } elseif ( $this->viewIsRenderAction || !$this->isCurrent() ||
                        !MediaWikiServices::getInstance()->getPermissionManager()
                                ->quickUserCan( 'edit', $user, $this->getTitle() )
                ) {
                        $poOptions['enableSectionEditLinks'] = false;
                }

                # Try client and file cache
                if ( $oldid === 0 && $this->mPage->checkTouched() ) {
                        # Try to stream the output from file cache
                        if ( $wgUseFileCache && $this->tryFileCache() ) {
                                wfDebug( __METHOD__ . ": done file cache\n" );
                                # tell wgOut that output is taken care of
                                $outputPage->disable();
                                $this->mPage->doViewUpdates( $user, $oldid );

                                return;
                        }
                }

                # Should the parser cache be used?
                $useParserCache = $this->mPage->shouldCheckParserCache( $parserOptions, $oldid );
                wfDebug( 'Article::view using parser cache: ' . ( $useParserCache ? 'yes' : 'no' ) . "\n" );
                if ( $user->getStubThreshold() ) {
                        MediaWikiServices::getInstance()->getStatsdDataFactory()->increment( 'pcache_miss_stub' );
                }

                $this->showRedirectedFromHeader();
                $this->showNamespaceHeader();

                # Iterate through the possible ways of constructing the output text.
                # Keep going until $outputDone is set, or we run out of things to do.
                $pass = 0;
                $outputDone = false;
                $this->mParserOutput = false;

                while ( !$outputDone && ++$pass ) {
                        switch ( $pass ) {
                                case 1:
                                        // Avoid PHP 7.1 warning of passing $this by reference
                                        $articlePage = $this;
                                        Hooks::run( 'ArticleViewHeader', [ &$articlePage, &$outputDone, &$useParserCache ] );
                                        break;
                                case 2:
                                        # Early abort if the page doesn't exist
                                        if ( !$this->mPage->exists() ) {
                                                wfDebug( __METHOD__ . ": showing missing article\n" );
                                                $this->showMissingArticle();
                                                $this->mPage->doViewUpdates( $user );
                                                return;
                                        }

                                        # Try the parser cache
                                        if ( $useParserCache ) {
                                                $this->mParserOutput = $parserCache->get( $this->mPage, $parserOptions );

                                                if ( $this->mParserOutput !== false ) {
                                                        if ( $oldid ) {
                                                                wfDebug( __METHOD__ . ": showing parser cache contents for current rev permalink\n" );
                                                                $this->setOldSubtitle( $oldid );
                                                        } else {
                                                                wfDebug( __METHOD__ . ": showing parser cache contents\n" );
                                                        }
                                                        $outputPage->addParserOutput( $this->mParserOutput, $poOptions );
                                                        # Ensure that UI elements requiring revision ID have
                                                        # the correct version information.
                                                        $outputPage->setRevisionId( $this->mPage->getLatest() );
                                                        # Preload timestamp to avoid a DB hit
                                                        $cachedTimestamp = $this->mParserOutput->getTimestamp();
                                                        if ( $cachedTimestamp !== null ) {
                                                                $outputPage->setRevisionTimestamp( $cachedTimestamp );
                                                                $this->mPage->setTimestamp( $cachedTimestamp );
                                                        }
                                                        $outputDone = true;
                                                }
                                        }
                                        break;
                                case 3:
                                        # Are we looking at an old revision
                                        $rev = $this->fetchRevisionRecord();
                                        if ( $oldid && $this->fetchResult->isOK() ) {
                                                $this->setOldSubtitle( $oldid );

                                                if ( !$this->showDeletedRevisionHeader() ) {
                                                        wfDebug( __METHOD__ . ": cannot view deleted revision\n" );
                                                        return;
                                                }
                                        }

                                        # Ensure that UI elements requiring revision ID have
                                        # the correct version information.
                                        $outputPage->setRevisionId( $this->getRevIdFetched() );
                                        # Preload timestamp to avoid a DB hit
                                        $outputPage->setRevisionTimestamp( $this->mPage->getTimestamp() );

                                        # Pages containing custom CSS or JavaScript get special treatment
                                        if ( $this->getTitle()->isSiteConfigPage() || $this->getTitle()->isUserConfigPage() ) {
                                                $dir = $this->getContext()->getLanguage()->getDir();
                                                $lang = $this->getContext()->getLanguage()->getHtmlCode();

                                                $outputPage->wrapWikiMsg(
                                                        "<div id='mw-clearyourcache' lang='$lang' dir='$dir' class='mw-content-$dir'>\n$1\n</div>",
                                                        'clearyourcache'
                                                );
                                        } elseif ( !Hooks::run( 'ArticleRevisionViewCustom', [
                                                        $rev,
                                                        $this->getTitle(),
                                                        $oldid,
                                                        $outputPage,
                                                ] )
                                        ) {
                                                // NOTE: sync with hooks called in DifferenceEngine::renderNewRevision()
                                                // Allow extensions do their own custom view for certain pages
                                                $outputDone = true;
                                        } elseif ( !Hooks::run( 'ArticleContentViewCustom',
                                                [ $this->fetchContentObject(), $this->getTitle(), $outputPage ], '1.32' )
                                        ) {
                                                // NOTE: sync with hooks called in DifferenceEngine::renderNewRevision()
                                                // Allow extensions do their own custom view for certain pages
                                                $outputDone = true;
                                        }
                                        break;
                                case 4:
                                        # Run the parse, protected by a pool counter
                                        wfDebug( __METHOD__ . ": doing uncached parse\n" );

                                        $rev = $this->fetchRevisionRecord();
                                        $error = null;

                                        if ( $rev ) {
                                                $poolArticleView = new PoolWorkArticleView(
                                                        $this->getPage(),
                                                        $parserOptions,
                                                        $this->getRevIdFetched(),
                                                        $useParserCache,
                                                        $rev,
                                                        // permission checking was done earlier via showDeletedRevisionHeader()
                                                        RevisionRecord::RAW
                                                );
                                                $ok = $poolArticleView->execute();
                                                $error = $poolArticleView->getError();
                                                $this->mParserOutput = $poolArticleView->getParserOutput() ?: null;

                                                # Don't cache a dirty ParserOutput object
                                                if ( $poolArticleView->getIsDirty() ) {
                                                        $outputPage->setCdnMaxage( 0 );
                                                        $outputPage->addHTML( "<!-- parser cache is expired, " .
                                                                "sending anyway due to pool overload-->\n" );
                                                }
                                        } else {
                                                $ok = false;
                                        }

                                        if ( !$ok ) {
                                                if ( $error ) {
                                                        $outputPage->clearHTML(); // for release() errors
                                                        $outputPage->enableClientCache( false );
                                                        $outputPage->setRobotPolicy( 'noindex,nofollow' );

                                                        $errortext = $error->getWikiText( false, 'view-pool-error' );
                                                        $outputPage->wrapWikiTextAsInterface( 'errorbox', $errortext );
                                                }
                                                # Connection or timeout error
                                                return;
                                        }

                                        if ( $this->mParserOutput ) {
                                                $outputPage->addParserOutput( $this->mParserOutput, $poOptions );
                                        }

                                        if ( $rev && $this->getRevisionRedirectTarget( $rev ) ) {
                                                $outputPage->addSubtitle( "<span id=\"redirectsub\">" .
                                                        $this->getContext()->msg( 'redirectpagesub' )->parse() . "</span>" );
                                        }

                                        $outputDone = true;
                                        break;
                                # Should be unreachable, but just in case...
                                default:
                                        break 2;
                        }
                }

                // Get the ParserOutput actually *displayed* here.
                // Note that $this->mParserOutput is the *current*/oldid version output.
                // Note that the ArticleViewHeader hook is allowed to set $outputDone to a
                // ParserOutput instance.
                $pOutput = ( $outputDone instanceof ParserOutput )
                        ? $outputDone // object fetched by hook
                        : ( $this->mParserOutput ?: null ); // ParserOutput or null, avoid false

                # Adjust title for main page & pages with displaytitle
                if ( $pOutput ) {
                        $this->adjustDisplayTitle( $pOutput );
                }

                # For the main page, overwrite the <title> element with the con-
                # tents of 'pagetitle-view-mainpage' instead of the default (if
                # that's not empty).
                # This message always exists because it is in the i18n files
                if ( $this->getTitle()->isMainPage() ) {
                        $msg = wfMessage( 'pagetitle-view-mainpage' )->inContentLanguage();
                        if ( !$msg->isDisabled() ) {
                                $outputPage->setHTMLTitle( $msg->title( $this->getTitle() )->text() );
                        }
                }

                # Use adaptive TTLs for CDN so delayed/failed purges are noticed less often.
                # This could use getTouched(), but that could be scary for major template edits.
                $outputPage->adaptCdnTTL( $this->mPage->getTimestamp(), IExpiringStore::TTL_DAY );

                # Check for any __NOINDEX__ tags on the page using $pOutput
                $policy = $this->getRobotPolicy( 'view', $pOutput ?: null );
                $outputPage->setIndexPolicy( $policy['index'] );
                $outputPage->setFollowPolicy( $policy['follow'] ); // FIXME: test this

                $this->showViewFooter();
                $this->mPage->doViewUpdates( $user, $oldid ); // FIXME: test this

                # Load the postEdit module if the user just saved this revision
                # See also EditPage::setPostEditCookie
                $request = $this->getContext()->getRequest();
                $cookieKey = EditPage::POST_EDIT_COOKIE_KEY_PREFIX . $this->getRevIdFetched();
                $postEdit = $request->getCookie( $cookieKey );
                if ( $postEdit ) {
                        # Clear the cookie. This also prevents caching of the response.
                        $request->response()->clearCookie( $cookieKey );
                        $outputPage->addJsConfigVars( 'wgPostEdit', $postEdit );
                        $outputPage->addModules( 'mediawiki.action.view.postEdit' ); // FIXME: test this
                }
        }

        /**
         * @param RevisionRecord $revision
         * @return null|Title
         */
        private function getRevisionRedirectTarget( RevisionRecord $revision ) {
                // TODO: find a *good* place for the code that determines the redirect target for
                // a given revision!
                // NOTE: Use main slot content. Compare code in DerivedPageDataUpdater::revisionIsRedirect.
                $content = $revision->getContent( SlotRecord::MAIN );
                return $content ? $content->getRedirectTarget() : null;
        }

        /**
         * Adjust title for pages with displaytitle, -{T|}- or language conversion
         * @param ParserOutput $pOutput
         */
        public function adjustDisplayTitle( ParserOutput $pOutput ) {
                $out = $this->getContext()->getOutput();

                # Adjust the title if it was set by displaytitle, -{T|}- or language conversion
                $titleText = $pOutput->getTitleText();
                if ( strval( $titleText ) !== '' ) {
                        $out->setPageTitle( $titleText );
                        $out->setDisplayTitle( $titleText );
                }
        }

        /**
         * Show a diff page according to current request variables. For use within
         * Article::view() only, other callers should use the DifferenceEngine class.
         */
        protected function showDiffPage() {
                $request = $this->getContext()->getRequest();
                $user = $this->getContext()->getUser();
                $diff = $request->getVal( 'diff' );
                $rcid = $request->getVal( 'rcid' );
                $diffOnly = $request->getBool( 'diffonly', $user->getOption( 'diffonly' ) );
                $purge = $request->getVal( 'action' ) == 'purge';
                $unhide = $request->getInt( 'unhide' ) == 1;
                $oldid = $this->getOldID();

                $rev = $this->getRevisionFetched();

                if ( !$rev ) {
                        $this->getContext()->getOutput()->setPageTitle( wfMessage( 'errorpagetitle' ) );
                        $msg = $this->getContext()->msg( 'difference-missing-revision' )
                                ->params( $oldid )
                                ->numParams( 1 )
                                ->parseAsBlock();
                        $this->getContext()->getOutput()->addHTML( $msg );
                        return;
                }

                $contentHandler = $rev->getContentHandler();
                $de = $contentHandler->createDifferenceEngine(
                        $this->getContext(),
                        $oldid,
                        $diff,
                        $rcid,
                        $purge,
                        $unhide
                );

                // DifferenceEngine directly fetched the revision:
                $this->mRevIdFetched = $de->getNewid();
                $de->showDiffPage( $diffOnly );

                // Run view updates for the newer revision being diffed (and shown
                // below the diff if not $diffOnly).
                list( $old, $new ) = $de->mapDiffPrevNext( $oldid, $diff );
                // New can be false, convert it to 0 - this conveniently means the latest revision
                $this->mPage->doViewUpdates( $user, (int)$new );
        }

        /**
         * Get the robot policy to be used for the current view
         * @param string $action The action= GET parameter
         * @param ParserOutput|null $pOutput
         * @return array The policy that should be set
         * @todo actions other than 'view'
         */
        public function getRobotPolicy( $action, ParserOutput $pOutput = null ) {
                global $wgArticleRobotPolicies, $wgNamespaceRobotPolicies, $wgDefaultRobotPolicy;

                $ns = $this->getTitle()->getNamespace();

                # Don't index user and user talk pages for blocked users (T13443)
                if ( ( $ns == NS_USER || $ns == NS_USER_TALK ) && !$this->getTitle()->isSubpage() ) {
                        $specificTarget = null;
                        $vagueTarget = null;
                        $titleText = $this->getTitle()->getText();
                        if ( IP::isValid( $titleText ) ) {
                                $vagueTarget = $titleText;
                        } else {
                                $specificTarget = $titleText;
                        }
                        if ( DatabaseBlock::newFromTarget( $specificTarget, $vagueTarget ) instanceof DatabaseBlock ) {
                                return [
                                        'index' => 'noindex',
                                        'follow' => 'nofollow'
                                ];
                        }
                }

                if ( $this->mPage->getId() === 0 || $this->getOldID() ) {
                        # Non-articles (special pages etc), and old revisions
                        return [
                                'index' => 'noindex',
                                'follow' => 'nofollow'
                        ];
                } elseif ( $this->getContext()->getOutput()->isPrintable() ) {
                        # Discourage indexing of printable versions, but encourage following
                        return [
                                'index' => 'noindex',
                                'follow' => 'follow'
                        ];
                } elseif ( $this->getContext()->getRequest()->getInt( 'curid' ) ) {
                        # For ?curid=x urls, disallow indexing
                        return [
                                'index' => 'noindex',
                                'follow' => 'follow'
                        ];
                }

                # Otherwise, construct the policy based on the various config variables.
                $policy = self::formatRobotPolicy( $wgDefaultRobotPolicy );

                if ( isset( $wgNamespaceRobotPolicies[$ns] ) ) {
                        # Honour customised robot policies for this namespace
                        $policy = array_merge(
                                $policy,
                                self::formatRobotPolicy( $wgNamespaceRobotPolicies[$ns] )
                        );
                }
                if ( $this->getTitle()->canUseNoindex() && is_object( $pOutput ) && $pOutput->getIndexPolicy() ) {
                        # __INDEX__ and __NOINDEX__ magic words, if allowed. Incorporates
                        # a final sanity check that we have really got the parser output.
                        $policy = array_merge(
                                $policy,
                                [ 'index' => $pOutput->getIndexPolicy() ]
                        );
                }

                if ( isset( $wgArticleRobotPolicies[$this->getTitle()->getPrefixedText()] ) ) {
                        # (T16900) site config can override user-defined __INDEX__ or __NOINDEX__
                        $policy = array_merge(
                                $policy,
                                self::formatRobotPolicy( $wgArticleRobotPolicies[$this->getTitle()->getPrefixedText()] )
                        );
                }

                return $policy;
        }

        /**
         * Converts a String robot policy into an associative array, to allow
         * merging of several policies using array_merge().
         * @param array|string $policy Returns empty array on null/false/'', transparent
         *   to already-converted arrays, converts string.
         * @return array 'index' => \<indexpolicy\>, 'follow' => \<followpolicy\>
         */
        public static function formatRobotPolicy( $policy ) {
                if ( is_array( $policy ) ) {
                        return $policy;
                } elseif ( !$policy ) {
                        return [];
                }

                $policy = explode( ',', $policy );
                $policy = array_map( 'trim', $policy );

                $arr = [];
                foreach ( $policy as $var ) {
                        if ( in_array( $var, [ 'index', 'noindex' ] ) ) {
                                $arr['index'] = $var;
                        } elseif ( in_array( $var, [ 'follow', 'nofollow' ] ) ) {
                                $arr['follow'] = $var;
                        }
                }

                return $arr;
        }

        /**
         * If this request is a redirect view, send "redirected from" subtitle to
         * the output. Returns true if the header was needed, false if this is not
         * a redirect view. Handles both local and remote redirects.
         *
         * @return bool
         */
        public function showRedirectedFromHeader() {
                global $wgRedirectSources;

                $context = $this->getContext();
                $outputPage = $context->getOutput();
                $request = $context->getRequest();
                $rdfrom = $request->getVal( 'rdfrom' );

                // Construct a URL for the current page view, but with the target title
                $query = $request->getValues();
                unset( $query['rdfrom'] );
                unset( $query['title'] );
                if ( $this->getTitle()->isRedirect() ) {
                        // Prevent double redirects
                        $query['redirect'] = 'no';
                }
                $redirectTargetUrl = $this->getTitle()->getLinkURL( $query );

                if ( isset( $this->mRedirectedFrom ) ) {
                        // Avoid PHP 7.1 warning of passing $this by reference
                        $articlePage = $this;

                        // This is an internally redirected page view.
                        // We'll need a backlink to the source page for navigation.
                        if ( Hooks::run( 'ArticleViewRedirect', [ &$articlePage ] ) ) {
                                $redir = Linker::linkKnown(
                                        $this->mRedirectedFrom,
                                        null,
                                        [],
                                        [ 'redirect' => 'no' ]
                                );

                                $outputPage->addSubtitle( "<span class=\"mw-redirectedfrom\">" .
                                        $context->msg( 'redirectedfrom' )->rawParams( $redir )->parse()
                                . "</span>" );

                                // Add the script to update the displayed URL and
                                // set the fragment if one was specified in the redirect
                                $outputPage->addJsConfigVars( [
                                        'wgInternalRedirectTargetUrl' => $redirectTargetUrl,
                                ] );
                                $outputPage->addModules( 'mediawiki.action.view.redirect' );

                                // Add a <link rel="canonical"> tag
                                $outputPage->setCanonicalUrl( $this->getTitle()->getCanonicalURL() );

                                // Tell the output object that the user arrived at this article through a redirect
                                $outputPage->setRedirectedFrom( $this->mRedirectedFrom );

                                return true;
                        }
                } elseif ( $rdfrom ) {
                        // This is an externally redirected view, from some other wiki.
                        // If it was reported from a trusted site, supply a backlink.
                        if ( $wgRedirectSources && preg_match( $wgRedirectSources, $rdfrom ) ) {
                                $redir = Linker::makeExternalLink( $rdfrom, $rdfrom );
                                $outputPage->addSubtitle( "<span class=\"mw-redirectedfrom\">" .
                                        $context->msg( 'redirectedfrom' )->rawParams( $redir )->parse()
                                . "</span>" );

                                // Add the script to update the displayed URL
                                $outputPage->addJsConfigVars( [
                                        'wgInternalRedirectTargetUrl' => $redirectTargetUrl,
                                ] );
                                $outputPage->addModules( 'mediawiki.action.view.redirect' );

                                return true;
                        }
                }

                return false;
        }

        /**
         * Show a header specific to the namespace currently being viewed, like
         * [[MediaWiki:Talkpagetext]]. For Article::view().
         */
        public function showNamespaceHeader() {
                if ( $this->getTitle()->isTalkPage() && !wfMessage( 'talkpageheader' )->isDisabled() ) {
                        $this->getContext()->getOutput()->wrapWikiMsg(
                                "<div class=\"mw-talkpageheader\">\n$1\n</div>",
                                [ 'talkpageheader' ]
                        );
                }
        }

        /**
         * Show the footer section of an ordinary page view
         */
        public function showViewFooter() {
                # check if we're displaying a [[User talk:x.x.x.x]] anonymous talk page
                if ( $this->getTitle()->getNamespace() == NS_USER_TALK
                        && IP::isValid( $this->getTitle()->getText() )
                ) {
                        $this->getContext()->getOutput()->addWikiMsg( 'anontalkpagetext' );
                }

                // Show a footer allowing the user to patrol the shown revision or page if possible
                $patrolFooterShown = $this->showPatrolFooter();

                Hooks::run( 'ArticleViewFooter', [ $this, $patrolFooterShown ] );
        }

        /**
         * If patrol is possible, output a patrol UI box. This is called from the
         * footer section of ordinary page views. If patrol is not possible or not
         * desired, does nothing.
         * Side effect: When the patrol link is build, this method will call
         * OutputPage::preventClickjacking() and load mediawiki.page.patrol.ajax.
         *
         * @return bool
         */
        public function showPatrolFooter() {
                global $wgUseNPPatrol, $wgUseRCPatrol, $wgUseFilePatrol;

                // Allow hooks to decide whether to not output this at all
                if ( !Hooks::run( 'ArticleShowPatrolFooter', [ $this ] ) ) {
                        return false;
                }

                $outputPage = $this->getContext()->getOutput();
                $user = $this->getContext()->getUser();
                $title = $this->getTitle();
                $rc = false;

                if ( !MediaWikiServices::getInstance()->getPermissionManager()
                                ->quickUserCan( 'patrol', $user, $title )
                        || !( $wgUseRCPatrol || $wgUseNPPatrol
                                || ( $wgUseFilePatrol && $title->inNamespace( NS_FILE ) ) )
                ) {
                        // Patrolling is disabled or the user isn't allowed to
                        return false;
                }

                if ( $this->mRevision
                        && !RecentChange::isInRCLifespan( $this->mRevision->getTimestamp(), 21600 )
                ) {
                        // The current revision is already older than what could be in the RC table
                        // 6h tolerance because the RC might not be cleaned out regularly
                        return false;
                }

                // Check for cached results
                $cache = MediaWikiServices::getInstance()->getMainWANObjectCache();
                $key = $cache->makeKey( 'unpatrollable-page', $title->getArticleID() );
                if ( $cache->get( $key ) ) {
                        return false;
                }

                $dbr = wfGetDB( DB_REPLICA );
                $oldestRevisionTimestamp = $dbr->selectField(
                        'revision',
                        'MIN( rev_timestamp )',
                        [ 'rev_page' => $title->getArticleID() ],
                        __METHOD__
                );

                // New page patrol: Get the timestamp of the oldest revison which
                // the revision table holds for the given page. Then we look
                // whether it's within the RC lifespan and if it is, we try
                // to get the recentchanges row belonging to that entry
                // (with rc_new = 1).
                $recentPageCreation = false;
                if ( $oldestRevisionTimestamp
                        && RecentChange::isInRCLifespan( $oldestRevisionTimestamp, 21600 )
                ) {
                        // 6h tolerance because the RC might not be cleaned out regularly
                        $recentPageCreation = true;
                        $rc = RecentChange::newFromConds(
                                [
                                        'rc_new' => 1,
                                        'rc_timestamp' => $oldestRevisionTimestamp,
                                        'rc_namespace' => $title->getNamespace(),
                                        'rc_cur_id' => $title->getArticleID()
                                ],
                                __METHOD__
                        );
                        if ( $rc ) {
                                // Use generic patrol message for new pages
                                $markPatrolledMsg = wfMessage( 'markaspatrolledtext' );
                        }
                }

                // File patrol: Get the timestamp of the latest upload for this page,
                // check whether it is within the RC lifespan and if it is, we try
                // to get the recentchanges row belonging to that entry
                // (with rc_type = RC_LOG, rc_log_type = upload).
                $recentFileUpload = false;
                if ( ( !$rc || $rc->getAttribute( 'rc_patrolled' ) ) && $wgUseFilePatrol
                        && $title->getNamespace() === NS_FILE ) {
                        // Retrieve timestamp of most recent upload
                        $newestUploadTimestamp = $dbr->selectField(
                                'image',
                                'MAX( img_timestamp )',
                                [ 'img_name' => $title->getDBkey() ],
                                __METHOD__
                        );
                        if ( $newestUploadTimestamp
                                && RecentChange::isInRCLifespan( $newestUploadTimestamp, 21600 )
                        ) {
                                // 6h tolerance because the RC might not be cleaned out regularly
                                $recentFileUpload = true;
                                $rc = RecentChange::newFromConds(
                                        [
                                                'rc_type' => RC_LOG,
                                                'rc_log_type' => 'upload',
                                                'rc_timestamp' => $newestUploadTimestamp,
                                                'rc_namespace' => NS_FILE,
                                                'rc_cur_id' => $title->getArticleID()
                                        ],
                                        __METHOD__
                                );
                                if ( $rc ) {
                                        // Use patrol message specific to files
                                        $markPatrolledMsg = wfMessage( 'markaspatrolledtext-file' );
                                }
                        }
                }

                if ( !$recentPageCreation && !$recentFileUpload ) {
                        // Page creation and latest upload (for files) is too old to be in RC

                        // We definitely can't patrol so cache the information
                        // When a new file version is uploaded, the cache is cleared
                        $cache->set( $key, '1' );

                        return false;
                }

                if ( !$rc ) {
                        // Don't cache: This can be hit if the page gets accessed very fast after
                        // its creation / latest upload or in case we have high replica DB lag. In case
                        // the revision is too old, we will already return above.
                        return false;
                }

                if ( $rc->getAttribute( 'rc_patrolled' ) ) {
                        // Patrolled RC entry around

                        // Cache the information we gathered above in case we can't patrol
                        // Don't cache in case we can patrol as this could change
                        $cache->set( $key, '1' );

                        return false;
                }

                if ( $rc->getPerformer()->equals( $user ) ) {
                        // Don't show a patrol link for own creations/uploads. If the user could
                        // patrol them, they already would be patrolled
                        return false;
                }

                $outputPage->preventClickjacking();
                if ( MediaWikiServices::getInstance()
                                ->getPermissionManager()
                                ->userHasRight( $user, 'writeapi' )
                ) {
                        $outputPage->addModules( 'mediawiki.page.patrol.ajax' );
                }

                $link = Linker::linkKnown(
                        $title,
                        $markPatrolledMsg->escaped(),
                        [],
                        [
                                'action' => 'markpatrolled',
                                'rcid' => $rc->getAttribute( 'rc_id' ),
                        ]
                );

                $outputPage->addHTML(
                        "<div class='patrollink' data-mw='interface'>" .
                                wfMessage( 'markaspatrolledlink' )->rawParams( $link )->escaped() .
                        '</div>'
                );

                return true;
        }

        /**
         * Purge the cache used to check if it is worth showing the patrol footer
         * For example, it is done during re-uploads when file patrol is used.
         * @param int $articleID ID of the article to purge
         * @since 1.27
         */
        public static function purgePatrolFooterCache( $articleID ) {
                $cache = MediaWikiServices::getInstance()->getMainWANObjectCache();
                $cache->delete( $cache->makeKey( 'unpatrollable-page', $articleID ) );
        }

        /**
         * Show the error text for a missing article. For articles in the MediaWiki
         * namespace, show the default message text. To be called from Article::view().
         */
        public function showMissingArticle() {
                global $wgSend404Code;

                $outputPage = $this->getContext()->getOutput();
                // Whether the page is a root user page of an existing user (but not a subpage)
                $validUserPage = false;

                $title = $this->getTitle();

                $services = MediaWikiServices::getInstance();

                # Show info in user (talk) namespace. Does the user exist? Is he blocked?
                if ( $title->getNamespace() == NS_USER
                        || $title->getNamespace() == NS_USER_TALK
                ) {
                        $rootPart = explode( '/', $title->getText() )[0];
                        $user = User::newFromName( $rootPart, false /* allow IP users */ );
                        $ip = User::isIP( $rootPart );
                        $block = DatabaseBlock::newFromTarget( $user, $user );

                        if ( !( $user && $user->isLoggedIn() ) && !$ip ) { # User does not exist
                                $outputPage->wrapWikiMsg( "<div class=\"mw-userpage-userdoesnotexist error\">\n\$1\n</div>",
                                        [ 'userpage-userdoesnotexist-view', wfEscapeWikiText( $rootPart ) ] );
                        } elseif (
                                !is_null( $block ) &&
                                $block->getType() != DatabaseBlock::TYPE_AUTO &&
                                ( $block->isSitewide() || $user->isBlockedFrom( $title ) )
                        ) {
                                // Show log extract if the user is sitewide blocked or is partially
                                // blocked and not allowed to edit their user page or user talk page
                                LogEventsList::showLogExtract(
                                        $outputPage,
                                        'block',
                                        $services->getNamespaceInfo()->getCanonicalName( NS_USER ) . ':' .
                                                $block->getTarget(),
                                        '',
                                        [
                                                'lim' => 1,
                                                'showIfEmpty' => false,
                                                'msgKey' => [
                                                        'blocked-notice-logextract',
                                                        $user->getName() # Support GENDER in notice
                                                ]
                                        ]
                                );
                                $validUserPage = !$title->isSubpage();
                        } else {
                                $validUserPage = !$title->isSubpage();
                        }
                }

                Hooks::run( 'ShowMissingArticle', [ $this ] );

                # Show delete and move logs if there were any such events.
                # The logging query can DOS the site when bots/crawlers cause 404 floods,
                # so be careful showing this. 404 pages must be cheap as they are hard to cache.
                $dbCache = ObjectCache::getInstance( 'db-replicated' );
                $key = $dbCache->makeKey( 'page-recent-delete', md5( $title->getPrefixedText() ) );
                $loggedIn = $this->getContext()->getUser()->isLoggedIn();
                $sessionExists = $this->getContext()->getRequest()->getSession()->isPersistent();
                if ( $loggedIn || $dbCache->get( $key ) || $sessionExists ) {
                        $logTypes = [ 'delete', 'move', 'protect' ];

                        $dbr = wfGetDB( DB_REPLICA );

                        $conds = [ 'log_action != ' . $dbr->addQuotes( 'revision' ) ];
                        // Give extensions a chance to hide their (unrelated) log entries
                        Hooks::run( 'Article::MissingArticleConditions', [ &$conds, $logTypes ] );
                        LogEventsList::showLogExtract(
                                $outputPage,
                                $logTypes,
                                $title,
                                '',
                                [
                                        'lim' => 10,
                                        'conds' => $conds,
                                        'showIfEmpty' => false,
                                        'msgKey' => [ $loggedIn || $sessionExists
                                                ? 'moveddeleted-notice'
                                                : 'moveddeleted-notice-recent'
                                        ]
                                ]
                        );
                }

                if ( !$this->mPage->hasViewableContent() && $wgSend404Code && !$validUserPage ) {
                        // If there's no backing content, send a 404 Not Found
                        // for better machine handling of broken links.
                        $this->getContext()->getRequest()->response()->statusHeader( 404 );
                }

                // Also apply the robot policy for nonexisting pages (even if a 404 was used for sanity)
                $policy = $this->getRobotPolicy( 'view' );
                $outputPage->setIndexPolicy( $policy['index'] );
                $outputPage->setFollowPolicy( $policy['follow'] );

                $hookResult = Hooks::run( 'BeforeDisplayNoArticleText', [ $this ] );

                if ( !$hookResult ) {
                        return;
                }

                # Show error message
                $oldid = $this->getOldID();
                $pm = MediaWikiServices::getInstance()->getPermissionManager();
                if ( !$oldid && $title->getNamespace() === NS_MEDIAWIKI && $title->hasSourceText() ) {
                        // use fake Content object for system message
                        $parserOptions = ParserOptions::newCanonical( 'canonical' );
                        $outputPage->addParserOutput( $this->getEmptyPageParserOutput( $parserOptions ) );
                } else {
                        if ( $oldid ) {
                                $text = wfMessage( 'missing-revision', $oldid )->plain();
                        } elseif ( $pm->quickUserCan( 'create', $this->getContext()->getUser(), $title ) &&
                                $pm->quickUserCan( 'edit', $this->getContext()->getUser(), $title )
                        ) {
                                $message = $this->getContext()->getUser()->isLoggedIn() ? 'noarticletext' : 'noarticletextanon';
                                $text = wfMessage( $message )->plain();
                        } else {
                                $text = wfMessage( 'noarticletext-nopermission' )->plain();
                        }

                        $dir = $this->getContext()->getLanguage()->getDir();
                        $lang = $this->getContext()->getLanguage()->getHtmlCode();
                        $outputPage->addWikiTextAsInterface( Xml::openElement( 'div', [
                                'class' => "noarticletext mw-content-$dir",
                                'dir' => $dir,
                                'lang' => $lang,
                        ] ) . "\n$text\n</div>" );
                }
        }

        /**
         * If the revision requested for view is deleted, check permissions.
         * Send either an error message or a warning header to the output.
         *
         * @return bool True if the view is allowed, false if not.
         */
        public function showDeletedRevisionHeader() {
                if ( !$this->mRevision->isDeleted( RevisionRecord::DELETED_TEXT ) ) {
                        // Not deleted
                        return true;
                }

                $outputPage = $this->getContext()->getOutput();
                $user = $this->getContext()->getUser();
                // If the user is not allowed to see it...
                if ( !$this->mRevision->userCan( RevisionRecord::DELETED_TEXT, $user ) ) {
                        $outputPage->wrapWikiMsg( "<div class='mw-warning plainlinks'>\n$1\n</div>\n",
                                'rev-deleted-text-permission' );

                        return false;
                // If the user needs to confirm that they want to see it...
                } elseif ( $this->getContext()->getRequest()->getInt( 'unhide' ) != 1 ) {
                        # Give explanation and add a link to view the revision...
                        $oldid = intval( $this->getOldID() );
                        $link = $this->getTitle()->getFullURL( "oldid={$oldid}&unhide=1" );
                        $msg = $this->mRevision->isDeleted( RevisionRecord::DELETED_RESTRICTED ) ?
                                'rev-suppressed-text-unhide' : 'rev-deleted-text-unhide';
                        $outputPage->wrapWikiMsg( "<div class='mw-warning plainlinks'>\n$1\n</div>\n",
                                [ $msg, $link ] );

                        return false;
                // We are allowed to see...
                } else {
                        $msg = $this->mRevision->isDeleted( RevisionRecord::DELETED_RESTRICTED ) ?
                                'rev-suppressed-text-view' : 'rev-deleted-text-view';
                        $outputPage->wrapWikiMsg( "<div class='mw-warning plainlinks'>\n$1\n</div>\n", $msg );

                        return true;
                }
        }

        /**
         * Generate the navigation links when browsing through an article revisions
         * It shows the information as:
         *   Revision as of \<date\>; view current revision
         *   \<- Previous version | Next Version -\>
         *
         * @param int $oldid Revision ID of this article revision
         */
        public function setOldSubtitle( $oldid = 0 ) {
                // Avoid PHP 7.1 warning of passing $this by reference
                $articlePage = $this;

                if ( !Hooks::run( 'DisplayOldSubtitle', [ &$articlePage, &$oldid ] ) ) {
                        return;
                }

                $context = $this->getContext();
                $unhide = $context->getRequest()->getInt( 'unhide' ) == 1;

                # Cascade unhide param in links for easy deletion browsing
                $extraParams = [];
                if ( $unhide ) {
                        $extraParams['unhide'] = 1;
                }

                if ( $this->mRevision && $this->mRevision->getId() === $oldid ) {
                        $revision = $this->mRevision;
                } else {
                        $revision = Revision::newFromId( $oldid );
                }

                $timestamp = $revision->getTimestamp();

                $current = ( $oldid == $this->mPage->getLatest() );
                $language = $context->getLanguage();
                $user = $context->getUser();

                $td = $language->userTimeAndDate( $timestamp, $user );
                $tddate = $language->userDate( $timestamp, $user );
                $tdtime = $language->userTime( $timestamp, $user );

                # Show user links if allowed to see them. If hidden, then show them only if requested...
                $userlinks = Linker::revUserTools( $revision, !$unhide );

                $infomsg = $current && !$context->msg( 'revision-info-current' )->isDisabled()
                        ? 'revision-info-current'
                        : 'revision-info';

                $outputPage = $context->getOutput();
                $revisionInfo = "<div id=\"mw-{$infomsg}\">" .
                        $context->msg( $infomsg, $td )
                                ->rawParams( $userlinks )
                                ->params( $revision->getId(), $tddate, $tdtime, $revision->getUserText() )
                                ->rawParams( Linker::revComment( $revision, true, true ) )
                                ->parse() .
                        "</div>";

                $lnk = $current
                        ? $context->msg( 'currentrevisionlink' )->escaped()
                        : Linker::linkKnown(
                                $this->getTitle(),
                                $context->msg( 'currentrevisionlink' )->escaped(),
                                [],
                                $extraParams
                        );
                $curdiff = $current
                        ? $context->msg( 'diff' )->escaped()
                        : Linker::linkKnown(
                                $this->getTitle(),
                                $context->msg( 'diff' )->escaped(),
                                [],
                                [
                                        'diff' => 'cur',
                                        'oldid' => $oldid
                                ] + $extraParams
                        );
                $rl = MediaWikiServices::getInstance()->getRevisionLookup();
                $prevExist = (bool)$rl->getPreviousRevision( $revision->getRevisionRecord() );
                $prevlink = $prevExist
                        ? Linker::linkKnown(
                                $this->getTitle(),
                                $context->msg( 'previousrevision' )->escaped(),
                                [],
                                [
                                        'direction' => 'prev',
                                        'oldid' => $oldid
                                ] + $extraParams
                        )
                        : $context->msg( 'previousrevision' )->escaped();
                $prevdiff = $prevExist
                        ? Linker::linkKnown(
                                $this->getTitle(),
                                $context->msg( 'diff' )->escaped(),
                                [],
                                [
                                        'diff' => 'prev',
                                        'oldid' => $oldid
                                ] + $extraParams
                        )
                        : $context->msg( 'diff' )->escaped();
                $nextlink = $current
                        ? $context->msg( 'nextrevision' )->escaped()
                        : Linker::linkKnown(
                                $this->getTitle(),
                                $context->msg( 'nextrevision' )->escaped(),
                                [],
                                [
                                        'direction' => 'next',
                                        'oldid' => $oldid
                                ] + $extraParams
                        );
                $nextdiff = $current
                        ? $context->msg( 'diff' )->escaped()
                        : Linker::linkKnown(
                                $this->getTitle(),
                                $context->msg( 'diff' )->escaped(),
                                [],
                                [
                                        'diff' => 'next',
                                        'oldid' => $oldid
                                ] + $extraParams
                        );

                $cdel = Linker::getRevDeleteLink( $user, $revision, $this->getTitle() );
                if ( $cdel !== '' ) {
                        $cdel .= ' ';
                }

                // the outer div is need for styling the revision info and nav in MobileFrontend
                $outputPage->addSubtitle( "<div class=\"mw-revision\">" . $revisionInfo .
                        "<div id=\"mw-revision-nav\">" . $cdel .
                        $context->msg( 'revision-nav' )->rawParams(
                                $prevdiff, $prevlink, $lnk, $curdiff, $nextlink, $nextdiff
                        )->escaped() . "</div></div>" );
        }

        /**
         * Return the HTML for the top of a redirect page
         *
         * Chances are you should just be using the ParserOutput from
         * WikitextContent::getParserOutput instead of calling this for redirects.
         *
         * @param Title|array $target Destination(s) to redirect
         * @param bool $appendSubtitle [optional]
         * @param bool $forceKnown Should the image be shown as a bluelink regardless of existence?
         * @return string Containing HTML with redirect link
         *
         * @deprecated since 1.30
         */
        public function viewRedirect( $target, $appendSubtitle = true, $forceKnown = false ) {
                $lang = $this->getTitle()->getPageLanguage();
                $out = $this->getContext()->getOutput();
                if ( $appendSubtitle ) {
                        $out->addSubtitle( wfMessage( 'redirectpagesub' ) );
                }
                $out->addModuleStyles( 'mediawiki.action.view.redirectPage' );
                return static::getRedirectHeaderHtml( $lang, $target, $forceKnown );
        }

        /**
         * Return the HTML for the top of a redirect page
         *
         * Chances are you should just be using the ParserOutput from
         * WikitextContent::getParserOutput instead of calling this for redirects.
         *
         * @since 1.23
         * @param Language $lang
         * @param Title|array $target Destination(s) to redirect
         * @param bool $forceKnown Should the image be shown as a bluelink regardless of existence?
         * @return string Containing HTML with redirect link
         */
        public static function getRedirectHeaderHtml( Language $lang, $target, $forceKnown = false ) {
                if ( !is_array( $target ) ) {
                        $target = [ $target ];
                }

                $html = '<ul class="redirectText">';
                /** @var Title $title */
                foreach ( $target as $title ) {
                        $html .= '<li>' . Linker::link(
                                $title,
                                htmlspecialchars( $title->getFullText() ),
                                [],
                                // Make sure wiki page redirects are not followed
                                $title->isRedirect() ? [ 'redirect' => 'no' ] : [],
                                ( $forceKnown ? [ 'known', 'noclasses' ] : [] )
                        ) . '</li>';
                }
                $html .= '</ul>';

                $redirectToText = wfMessage( 'redirectto' )->inLanguage( $lang )->escaped();

                return '<div class="redirectMsg">' .
                        '<p>' . $redirectToText . '</p>' .
                        $html .
                        '</div>';
        }

        /**
         * Adds help link with an icon via page indicators.
         * Link target can be overridden by a local message containing a wikilink:
         * the message key is: 'namespace-' + namespace number + '-helppage'.
         * @param string $to Target MediaWiki.org page title or encoded URL.
         * @param bool $overrideBaseUrl Whether $url is a full URL, to avoid MW.o.
         * @since 1.25
         */
        public function addHelpLink( $to, $overrideBaseUrl = false ) {
                $msg = wfMessage(
                        'namespace-' . $this->getTitle()->getNamespace() . '-helppage'
                );

                $out = $this->getContext()->getOutput();
                if ( !$msg->isDisabled() ) {
                        $helpUrl = Skin::makeUrl( $msg->plain() );
                        $out->addHelpLink( $helpUrl, true );
                } else {
                        $out->addHelpLink( $to, $overrideBaseUrl );
                }
        }

        /**
         * Handle action=render
         */
        public function render() {
                $this->getContext()->getRequest()->response()->header( 'X-Robots-Tag: noindex' );
                $this->getContext()->getOutput()->setArticleBodyOnly( true );
                // We later set 'enableSectionEditLinks=false' based on this; also used by ImagePage
                $this->viewIsRenderAction = true;
                $this->view();
        }

        /**
         * action=protect handler
         */
        public function protect() {
                $form = new ProtectionForm( $this );
                $form->execute();
        }

        /**
         * action=unprotect handler (alias)
         */
        public function unprotect() {
                $this->protect();
        }

        /**
         * UI entry point for page deletion
         */
        public function delete() {
                # This code desperately needs to be totally rewritten

                $title = $this->getTitle();
                $context = $this->getContext();
                $user = $context->getUser();
                $request = $context->getRequest();

                # Check permissions
                $permissionErrors = $title->getUserPermissionsErrors( 'delete', $user );
                if ( count( $permissionErrors ) ) {
                        throw new PermissionsError( 'delete', $permissionErrors );
                }

                # Read-only check...
                if ( wfReadOnly() ) {
                        throw new ReadOnlyError;
                }

                # Better double-check that it hasn't been deleted yet!
                $this->mPage->loadPageData(
                        $request->wasPosted() ? WikiPage::READ_LATEST : WikiPage::READ_NORMAL
                );
                if ( !$this->mPage->exists() ) {
                        $deleteLogPage = new LogPage( 'delete' );
                        $outputPage = $context->getOutput();
                        $outputPage->setPageTitle( $context->msg( 'cannotdelete-title', $title->getPrefixedText() ) );
                        $outputPage->wrapWikiMsg( "<div class=\"error mw-error-cannotdelete\">\n$1\n</div>",
                                        [ 'cannotdelete', wfEscapeWikiText( $title->getPrefixedText() ) ]
                                );
                        $outputPage->addHTML(
                                Xml::element( 'h2', null, $deleteLogPage->getName()->text() )
                        );
                        LogEventsList::showLogExtract(
                                $outputPage,
                                'delete',
                                $title
                        );

                        return;
                }

                $deleteReasonList = $request->getText( 'wpDeleteReasonList', 'other' );
                $deleteReason = $request->getText( 'wpReason' );

                if ( $deleteReasonList == 'other' ) {
                        $reason = $deleteReason;
                } elseif ( $deleteReason != '' ) {
                        // Entry from drop down menu + additional comment
                        $colonseparator = wfMessage( 'colon-separator' )->inContentLanguage()->text();
                        $reason = $deleteReasonList . $colonseparator . $deleteReason;
                } else {
                        $reason = $deleteReasonList;
                }

                if ( $request->wasPosted() && $user->matchEditToken( $request->getVal( 'wpEditToken' ),
                        [ 'delete', $this->getTitle()->getPrefixedText() ] )
                ) {
                        # Flag to hide all contents of the archived revisions

                        $suppress = $request->getCheck( 'wpSuppress' ) && MediaWikiServices::getInstance()
                                        ->getPermissionManager()
                                        ->userHasRight( $user, 'suppressrevision' );

                        $this->doDelete( $reason, $suppress );

                        WatchAction::doWatchOrUnwatch( $request->getCheck( 'wpWatch' ), $title, $user );

                        return;
                }

                // Generate deletion reason
                $hasHistory = false;
                if ( !$reason ) {
                        try {
                                $reason = $this->generateReason( $hasHistory );
                        } catch ( Exception $e ) {
                                # if a page is horribly broken, we still want to be able to
                                # delete it. So be lenient about errors here.
                                wfDebug( "Error while building auto delete summary: $e" );
                                $reason = '';
                        }
                }

                // If the page has a history, insert a warning
                if ( $hasHistory ) {
                        $title = $this->getTitle();

                        // The following can use the real revision count as this is only being shown for users
                        // that can delete this page.
                        // This, as a side-effect, also makes sure that the following query isn't being run for
                        // pages with a larger history, unless the user has the 'bigdelete' right
                        // (and is about to delete this page).
                        $dbr = wfGetDB( DB_REPLICA );
                        $revisions = $edits = (int)$dbr->selectField(
                                'revision',
                                'COUNT(rev_page)',
                                [ 'rev_page' => $title->getArticleID() ],
                                __METHOD__
                        );

                        // @todo i18n issue/patchwork message
                        $context->getOutput()->addHTML(
                                '<strong class="mw-delete-warning-revisions">' .
                                $context->msg( 'historywarning' )->numParams( $revisions )->parse() .
                                $context->msg( 'word-separator' )->escaped() . Linker::linkKnown( $title,
                                        $context->msg( 'history' )->escaped(),
                                        [],
                                        [ 'action' => 'history' ] ) .
                                '</strong>'
                        );

                        if ( $title->isBigDeletion() ) {
                                global $wgDeleteRevisionsLimit;
                                $context->getOutput()->wrapWikiMsg( "<div class='error'>\n$1\n</div>\n",
                                        [
                                                'delete-warning-toobig',
                                                $context->getLanguage()->formatNum( $wgDeleteRevisionsLimit )
                                        ]
                                );
                        }
                }

                $this->confirmDelete( $reason );
        }

        /**
         * Output deletion confirmation dialog
         * @todo Move to another file?
         * @param string $reason Prefilled reason
         */
        public function confirmDelete( $reason ) {
                wfDebug( "Article::confirmDelete\n" );

                $title = $this->getTitle();
                $ctx = $this->getContext();
                $outputPage = $ctx->getOutput();
                $outputPage->setPageTitle( wfMessage( 'delete-confirm', $title->getPrefixedText() ) );
                $outputPage->addBacklinkSubtitle( $title );
                $outputPage->setRobotPolicy( 'noindex,nofollow' );
                $outputPage->addModules( 'mediawiki.action.delete' );

                $backlinkCache = $title->getBacklinkCache();
                if ( $backlinkCache->hasLinks( 'pagelinks' ) || $backlinkCache->hasLinks( 'templatelinks' ) ) {
                        $outputPage->wrapWikiMsg( "<div class='mw-warning plainlinks'>\n$1\n</div>\n",
                                'deleting-backlinks-warning' );
                }

                $subpageQueryLimit = 51;
                $subpages = $title->getSubpages( $subpageQueryLimit );
                $subpageCount = count( $subpages );
                if ( $subpageCount > 0 ) {
                        $outputPage->wrapWikiMsg( "<div class='mw-warning plainlinks'>\n$1\n</div>\n",
                                [ 'deleting-subpages-warning', Message::numParam( $subpageCount ) ] );
                }
                $outputPage->addWikiMsg( 'confirmdeletetext' );

                Hooks::run( 'ArticleConfirmDelete', [ $this, $outputPage, &$reason ] );

                $user = $this->getContext()->getUser();
                $checkWatch = $user->getBoolOption( 'watchdeletion' ) || $user->isWatched( $title );

                $outputPage->enableOOUI();

                $fields = [];

                $options = Xml::listDropDownOptions(
                        $ctx->msg( 'deletereason-dropdown' )->inContentLanguage()->text(),
                        [ 'other' => $ctx->msg( 'deletereasonotherlist' )->inContentLanguage()->text() ]
                );
                $options = Xml::listDropDownOptionsOoui( $options );

                $fields[] = new OOUI\FieldLayout(
                        new OOUI\DropdownInputWidget( [
                                'name' => 'wpDeleteReasonList',
                                'inputId' => 'wpDeleteReasonList',
                                'tabIndex' => 1,
                                'infusable' => true,
                                'value' => '',
                                'options' => $options
                        ] ),
                        [
                                'label' => $ctx->msg( 'deletecomment' )->text(),
                                'align' => 'top',
                        ]
                );

                // HTML maxlength uses "UTF-16 code units", which means that characters outside BMP
                // (e.g. emojis) count for two each. This limit is overridden in JS to instead count
                // Unicode codepoints.
                $fields[] = new OOUI\FieldLayout(
                        new OOUI\TextInputWidget( [
                                'name' => 'wpReason',
                                'inputId' => 'wpReason',
                                'tabIndex' => 2,
                                'maxLength' => CommentStore::COMMENT_CHARACTER_LIMIT,
                                'infusable' => true,
                                'value' => $reason,
                                'autofocus' => true,
                        ] ),
                        [
                                'label' => $ctx->msg( 'deleteotherreason' )->text(),
                                'align' => 'top',
                        ]
                );

                if ( $user->isLoggedIn() ) {
                        $fields[] = new OOUI\FieldLayout(
                                new OOUI\CheckboxInputWidget( [
                                        'name' => 'wpWatch',
                                        'inputId' => 'wpWatch',
                                        'tabIndex' => 3,
                                        'selected' => $checkWatch,
                                ] ),
                                [
                                        'label' => $ctx->msg( 'watchthis' )->text(),
                                        'align' => 'inline',
                                        'infusable' => true,
                                ]
                        );
                }
                $permissionManager = MediaWikiServices::getInstance()->getPermissionManager();
                if ( $permissionManager->userHasRight( $user, 'suppressrevision' ) ) {
                        $fields[] = new OOUI\FieldLayout(
                                new OOUI\CheckboxInputWidget( [
                                        'name' => 'wpSuppress',
                                        'inputId' => 'wpSuppress',
                                        'tabIndex' => 4,
                                ] ),
                                [
                                        'label' => $ctx->msg( 'revdelete-suppress' )->text(),
                                        'align' => 'inline',
                                        'infusable' => true,
                                ]
                        );
                }

                $fields[] = new OOUI\FieldLayout(
                        new OOUI\ButtonInputWidget( [
                                'name' => 'wpConfirmB',
                                'inputId' => 'wpConfirmB',
                                'tabIndex' => 5,
                                'value' => $ctx->msg( 'deletepage' )->text(),
                                'label' => $ctx->msg( 'deletepage' )->text(),
                                'flags' => [ 'primary', 'destructive' ],
                                'type' => 'submit',
                        ] ),
                        [
                                'align' => 'top',
                        ]
                );

                $fieldset = new OOUI\FieldsetLayout( [
                        'label' => $ctx->msg( 'delete-legend' )->text(),
                        'id' => 'mw-delete-table',
                        'items' => $fields,
                ] );

                $form = new OOUI\FormLayout( [
                        'method' => 'post',
                        'action' => $title->getLocalURL( 'action=delete' ),
                        'id' => 'deleteconfirm',
                ] );
                $form->appendContent(
                        $fieldset,
                        new OOUI\HtmlSnippet(
                                Html::hidden( 'wpEditToken', $user->getEditToken( [ 'delete', $title->getPrefixedText() ] ) )
                        )
                );

                $outputPage->addHTML(
                        new OOUI\PanelLayout( [
                                'classes' => [ 'deletepage-wrapper' ],
                                'expanded' => false,
                                'padded' => true,
                                'framed' => true,
                                'content' => $form,
                        ] )
                );

                if ( $permissionManager->userHasRight( $user, 'editinterface' ) ) {
                        $link = Linker::linkKnown(
                                $ctx->msg( 'deletereason-dropdown' )->inContentLanguage()->getTitle(),
                                wfMessage( 'delete-edit-reasonlist' )->escaped(),
                                [],
                                [ 'action' => 'edit' ]
                        );
                        $outputPage->addHTML( '<p class="mw-delete-editreasons">' . $link . '</p>' );
                }

                $deleteLogPage = new LogPage( 'delete' );
                $outputPage->addHTML( Xml::element( 'h2', null, $deleteLogPage->getName()->text() ) );
                LogEventsList::showLogExtract( $outputPage, 'delete', $title );
        }

        /**
         * Perform a deletion and output success or failure messages
         * @param string $reason
         * @param bool $suppress
         * @param bool $immediate false allows deleting over time via the job queue
         * @throws FatalError
         * @throws MWException
         */
        public function doDelete( $reason, $suppress = false, $immediate = false ) {
                $error = '';
                $context = $this->getContext();
                $outputPage = $context->getOutput();
                $user = $context->getUser();
                $status = $this->mPage->doDeleteArticleReal( $reason, $suppress, 0, true, $error, $user,
                        [], 'delete', $immediate );

                if ( $status->isOK() ) {
                        $deleted = $this->getTitle()->getPrefixedText();

                        $outputPage->setPageTitle( wfMessage( 'actioncomplete' ) );
                        $outputPage->setRobotPolicy( 'noindex,nofollow' );

                        if ( $status->isGood() ) {
                                $loglink = '[[Special:Log/delete|' . wfMessage( 'deletionlog' )->text() . ']]';
                                $outputPage->addWikiMsg( 'deletedtext', wfEscapeWikiText( $deleted ), $loglink );
                                Hooks::run( 'ArticleDeleteAfterSuccess', [ $this->getTitle(), $outputPage ] );
                        } else {
                                $outputPage->addWikiMsg( 'delete-scheduled', wfEscapeWikiText( $deleted ) );
                        }

                        $outputPage->returnToMain( false );
                } else {
                        $outputPage->setPageTitle(
                                wfMessage( 'cannotdelete-title',
                                        $this->getTitle()->getPrefixedText() )
                        );

                        if ( $error == '' ) {
                                $outputPage->wrapWikiTextAsInterface(
                                        'error mw-error-cannotdelete',
                                        $status->getWikiText()
                                );
                                $deleteLogPage = new LogPage( 'delete' );
                                $outputPage->addHTML( Xml::element( 'h2', null, $deleteLogPage->getName()->text() ) );

                                LogEventsList::showLogExtract(
                                        $outputPage,
                                        'delete',
                                        $this->getTitle()
                                );
                        } else {
                                $outputPage->addHTML( $error );
                        }
                }
        }

        /* Caching functions */

        /**
         * checkLastModified returns true if it has taken care of all
         * output to the client that is necessary for this request.
         * (that is, it has sent a cached version of the page)
         *
         * @return bool True if cached version send, false otherwise
         */
        protected function tryFileCache() {
                static $called = false;

                if ( $called ) {
                        wfDebug( "Article::tryFileCache(): called twice!?\n" );
                        return false;
                }

                $called = true;
                if ( $this->isFileCacheable() ) {
                        $cache = new HTMLFileCache( $this->getTitle(), 'view' );
                        if ( $cache->isCacheGood( $this->mPage->getTouched() ) ) {
                                wfDebug( "Article::tryFileCache(): about to load file\n" );
                                $cache->loadFromFileCache( $this->getContext() );
                                return true;
                        } else {
                                wfDebug( "Article::tryFileCache(): starting buffer\n" );
                                ob_start( [ &$cache, 'saveToFileCache' ] );
                        }
                } else {
                        wfDebug( "Article::tryFileCache(): not cacheable\n" );
                }

                return false;
        }

        /**
         * Check if the page can be cached
         * @param int $mode One of the HTMLFileCache::MODE_* constants (since 1.28)
         * @return bool
         */
        public function isFileCacheable( $mode = HTMLFileCache::MODE_NORMAL ) {
                $cacheable = false;

                if ( HTMLFileCache::useFileCache( $this->getContext(), $mode ) ) {
                        $cacheable = $this->mPage->getId()
                                && !$this->mRedirectedFrom && !$this->getTitle()->isRedirect();
                        // Extension may have reason to disable file caching on some pages.
                        if ( $cacheable ) {
                                // Avoid PHP 7.1 warning of passing $this by reference
                                $articlePage = $this;
                                $cacheable = Hooks::run( 'IsFileCacheable', [ &$articlePage ] );
                        }
                }

                return $cacheable;
        }

        /** #@- */

        /**
         * Lightweight method to get the parser output for a page, checking the parser cache
         * and so on. Doesn't consider most of the stuff that Article::view() is forced to
         * consider, so it's not appropriate to use there.
         *
         * @since 1.16 (r52326) for LiquidThreads
         *
         * @param int|null $oldid Revision ID or null
         * @param User|null $user The relevant user
         * @return ParserOutput|bool ParserOutput or false if the given revision ID is not found
         */
        public function getParserOutput( $oldid = null, User $user = null ) {
                // XXX: bypasses mParserOptions and thus setParserOptions()

                if ( $user === null ) {
                        $parserOptions = $this->getParserOptions();
                } else {
                        $parserOptions = $this->mPage->makeParserOptions( $user );
                }

                return $this->mPage->getParserOutput( $parserOptions, $oldid );
        }

        /**
         * Override the ParserOptions used to render the primary article wikitext.
         *
         * @param ParserOptions $options
         * @throws MWException If the parser options where already initialized.
         */
        public function setParserOptions( ParserOptions $options ) {
                if ( $this->mParserOptions ) {
                        throw new MWException( "can't change parser options after they have already been set" );
                }

                // clone, so if $options is modified later, it doesn't confuse the parser cache.
                $this->mParserOptions = clone $options;
        }

        /**
         * Get parser options suitable for rendering the primary article wikitext
         * @return ParserOptions
         */
        public function getParserOptions() {
                if ( !$this->mParserOptions ) {
                        $this->mParserOptions = $this->mPage->makeParserOptions( $this->getContext() );
                }
                // Clone to allow modifications of the return value without affecting cache
                return clone $this->mParserOptions;
        }

        /**
         * Sets the context this Article is executed in
         *
         * @param IContextSource $context
         * @since 1.18
         */
        public function setContext( $context ) {
                $this->mContext = $context;
        }

        /**
         * Gets the context this Article is executed in
         *
         * @return IContextSource
         * @since 1.18
         */
        public function getContext() {
                if ( $this->mContext instanceof IContextSource ) {
                        return $this->mContext;
                } else {
                        wfDebug( __METHOD__ . " called and \$mContext is null. " .
                                "Return RequestContext::getMain(); for sanity\n" );
                        return RequestContext::getMain();
                }
        }

        /**
         * Use PHP's magic __get handler to handle accessing of
         * raw WikiPage fields for backwards compatibility.
         *
         * @param string $fname Field name
         * @return mixed
         */
        public function __get( $fname ) {
                if ( property_exists( $this->mPage, $fname ) ) {
                        # wfWarn( "Access to raw $fname field " . __CLASS__ );
                        return $this->mPage->$fname;
                }
                trigger_error( 'Inaccessible property via __get(): ' . $fname, E_USER_NOTICE );
        }

        /**
         * Use PHP's magic __set handler to handle setting of
         * raw WikiPage fields for backwards compatibility.
         *
         * @param string $fname Field name
         * @param mixed $fvalue New value
         */
        public function __set( $fname, $fvalue ) {
                if ( property_exists( $this->mPage, $fname ) ) {
                        # wfWarn( "Access to raw $fname field of " . __CLASS__ );
                        $this->mPage->$fname = $fvalue;
                // Note: extensions may want to toss on new fields
                } elseif ( !in_array( $fname, [ 'mContext', 'mPage' ] ) ) {
                        $this->mPage->$fname = $fvalue;
                } else {
                        trigger_error( 'Inaccessible property via __set(): ' . $fname, E_USER_NOTICE );
                }
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::checkFlags
         */
        public function checkFlags( $flags ) {
                return $this->mPage->checkFlags( $flags );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::checkTouched
         */
        public function checkTouched() {
                return $this->mPage->checkTouched();
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::clearPreparedEdit
         */
        public function clearPreparedEdit() {
                $this->mPage->clearPreparedEdit();
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::doDeleteArticleReal
         */
        public function doDeleteArticleReal(
                $reason, $suppress = false, $u1 = null, $u2 = null, &$error = '', User $user = null,
                $tags = [], $immediate = false
        ) {
                return $this->mPage->doDeleteArticleReal(
                        $reason, $suppress, $u1, $u2, $error, $user, $tags, 'delete', $immediate
                );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::doDeleteUpdates
         */
        public function doDeleteUpdates(
                $id,
                Content $content = null,
                $revision = null,
                User $user = null
        ) {
                $this->mPage->doDeleteUpdates( $id, $content, $revision, $user );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @deprecated since 1.29. Use WikiPage::doEditContent() directly instead
         * @see WikiPage::doEditContent
         */
        public function doEditContent( Content $content, $summary, $flags = 0, $originalRevId = false,
                User $user = null, $serialFormat = null
        ) {
                wfDeprecated( __METHOD__, '1.29' );
                return $this->mPage->doEditContent( $content, $summary, $flags, $originalRevId,
                        $user, $serialFormat
                );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::doEditUpdates
         */
        public function doEditUpdates( Revision $revision, User $user, array $options = [] ) {
                return $this->mPage->doEditUpdates( $revision, $user, $options );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::doPurge
         * @note In 1.28 (and only 1.28), this took a $flags parameter that
         *  controlled how much purging was done.
         */
        public function doPurge() {
                return $this->mPage->doPurge();
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::doViewUpdates
         */
        public function doViewUpdates( User $user, $oldid = 0 ) {
                $this->mPage->doViewUpdates( $user, $oldid );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::exists
         */
        public function exists() {
                return $this->mPage->exists();
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::followRedirect
         */
        public function followRedirect() {
                return $this->mPage->followRedirect();
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see ContentHandler::getActionOverrides
         */
        public function getActionOverrides() {
                return $this->mPage->getActionOverrides();
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::getAutoDeleteReason
         */
        public function getAutoDeleteReason( &$hasHistory ) {
                return $this->mPage->getAutoDeleteReason( $hasHistory );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::getCategories
         */
        public function getCategories() {
                return $this->mPage->getCategories();
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::getComment
         */
        public function getComment( $audience = RevisionRecord::FOR_PUBLIC, User $user = null ) {
                return $this->mPage->getComment( $audience, $user );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::getContentHandler
         */
        public function getContentHandler() {
                return $this->mPage->getContentHandler();
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::getContentModel
         */
        public function getContentModel() {
                return $this->mPage->getContentModel();
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::getContributors
         */
        public function getContributors() {
                return $this->mPage->getContributors();
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::getCreator
         */
        public function getCreator( $audience = RevisionRecord::FOR_PUBLIC, User $user = null ) {
                return $this->mPage->getCreator( $audience, $user );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::getDeletionUpdates
         */
        public function getDeletionUpdates( Content $content = null ) {
                return $this->mPage->getDeletionUpdates( $content );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::getHiddenCategories
         */
        public function getHiddenCategories() {
                return $this->mPage->getHiddenCategories();
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::getId
         */
        public function getId() {
                return $this->mPage->getId();
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::getLatest
         */
        public function getLatest() {
                return $this->mPage->getLatest();
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::getLinksTimestamp
         */
        public function getLinksTimestamp() {
                return $this->mPage->getLinksTimestamp();
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::getMinorEdit
         */
        public function getMinorEdit() {
                return $this->mPage->getMinorEdit();
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::getOldestRevision
         */
        public function getOldestRevision() {
                return $this->mPage->getOldestRevision();
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::getRedirectTarget
         */
        public function getRedirectTarget() {
                return $this->mPage->getRedirectTarget();
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::getRedirectURL
         */
        public function getRedirectURL( $rt ) {
                return $this->mPage->getRedirectURL( $rt );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::getRevision
         */
        public function getRevision() {
                return $this->mPage->getRevision();
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::getTimestamp
         */
        public function getTimestamp() {
                return $this->mPage->getTimestamp();
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::getTouched
         */
        public function getTouched() {
                return $this->mPage->getTouched();
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::getUndoContent
         */
        public function getUndoContent( Revision $undo, Revision $undoafter = null ) {
                return $this->mPage->getUndoContent( $undo, $undoafter );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::getUser
         */
        public function getUser( $audience = RevisionRecord::FOR_PUBLIC, User $user = null ) {
                return $this->mPage->getUser( $audience, $user );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::getUserText
         */
        public function getUserText( $audience = RevisionRecord::FOR_PUBLIC, User $user = null ) {
                return $this->mPage->getUserText( $audience, $user );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::hasViewableContent
         */
        public function hasViewableContent() {
                return $this->mPage->hasViewableContent();
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::insertOn
         */
        public function insertOn( $dbw, $pageId = null ) {
                return $this->mPage->insertOn( $dbw, $pageId );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::insertProtectNullRevision
         */
        public function insertProtectNullRevision( $revCommentMsg, array $limit,
                array $expiry, $cascade, $reason, $user = null
        ) {
                return $this->mPage->insertProtectNullRevision( $revCommentMsg, $limit,
                        $expiry, $cascade, $reason, $user
                );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::insertRedirect
         */
        public function insertRedirect() {
                return $this->mPage->insertRedirect();
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::insertRedirectEntry
         */
        public function insertRedirectEntry( Title $rt, $oldLatest = null ) {
                return $this->mPage->insertRedirectEntry( $rt, $oldLatest );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::isCountable
         */
        public function isCountable( $editInfo = false ) {
                return $this->mPage->isCountable( $editInfo );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::isRedirect
         */
        public function isRedirect() {
                return $this->mPage->isRedirect();
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::loadFromRow
         */
        public function loadFromRow( $data, $from ) {
                return $this->mPage->loadFromRow( $data, $from );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::loadPageData
         */
        public function loadPageData( $from = 'fromdb' ) {
                $this->mPage->loadPageData( $from );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::lockAndGetLatest
         */
        public function lockAndGetLatest() {
                return $this->mPage->lockAndGetLatest();
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::makeParserOptions
         */
        public function makeParserOptions( $context ) {
                return $this->mPage->makeParserOptions( $context );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::pageDataFromId
         */
        public function pageDataFromId( $dbr, $id, $options = [] ) {
                return $this->mPage->pageDataFromId( $dbr, $id, $options );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::pageDataFromTitle
         */
        public function pageDataFromTitle( $dbr, $title, $options = [] ) {
                return $this->mPage->pageDataFromTitle( $dbr, $title, $options );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::prepareContentForEdit
         */
        public function prepareContentForEdit(
                Content $content, $revision = null, User $user = null,
                $serialFormat = null, $useCache = true
        ) {
                return $this->mPage->prepareContentForEdit(
                        $content, $revision, $user,
                        $serialFormat, $useCache
                );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::protectDescription
         */
        public function protectDescription( array $limit, array $expiry ) {
                return $this->mPage->protectDescription( $limit, $expiry );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::protectDescriptionLog
         */
        public function protectDescriptionLog( array $limit, array $expiry ) {
                return $this->mPage->protectDescriptionLog( $limit, $expiry );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::replaceSectionAtRev
         */
        public function replaceSectionAtRev( $sectionId, Content $sectionContent,
                $sectionTitle = '', $baseRevId = null
        ) {
                return $this->mPage->replaceSectionAtRev( $sectionId, $sectionContent,
                        $sectionTitle, $baseRevId
                );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::replaceSectionContent
         */
        public function replaceSectionContent(
                $sectionId, Content $sectionContent, $sectionTitle = '', $edittime = null
        ) {
                return $this->mPage->replaceSectionContent(
                        $sectionId, $sectionContent, $sectionTitle, $edittime
                );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::setTimestamp
         */
        public function setTimestamp( $ts ) {
                $this->mPage->setTimestamp( $ts );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::shouldCheckParserCache
         */
        public function shouldCheckParserCache( ParserOptions $parserOptions, $oldId ) {
                return $this->mPage->shouldCheckParserCache( $parserOptions, $oldId );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::supportsSections
         */
        public function supportsSections() {
                return $this->mPage->supportsSections();
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::triggerOpportunisticLinksUpdate
         */
        public function triggerOpportunisticLinksUpdate( ParserOutput $parserOutput ) {
                return $this->mPage->triggerOpportunisticLinksUpdate( $parserOutput );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::updateCategoryCounts
         */
        public function updateCategoryCounts( array $added, array $deleted, $id = 0 ) {
                return $this->mPage->updateCategoryCounts( $added, $deleted, $id );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::updateIfNewerOn
         */
        public function updateIfNewerOn( $dbw, $revision ) {
                return $this->mPage->updateIfNewerOn( $dbw, $revision );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::updateRedirectOn
         */
        public function updateRedirectOn( $dbw, $redirectTitle, $lastRevIsRedirect = null ) {
                return $this->mPage->updateRedirectOn( $dbw, $redirectTitle, $lastRevIsRedirect );
        }

        /**
         * Call to WikiPage function for backwards compatibility.
         * @see WikiPage::updateRevisionOn
         */
        public function updateRevisionOn( $dbw, $revision, $lastRevision = null,
                $lastRevIsRedirect = null
        ) {
                return $this->mPage->updateRevisionOn( $dbw, $revision, $lastRevision,
                        $lastRevIsRedirect
                );
        }

        /**
         * @param array $limit
         * @param array $expiry
         * @param bool &$cascade
         * @param string $reason
         * @param User $user
         * @return Status
         */
        public function doUpdateRestrictions( array $limit, array $expiry, &$cascade,
                $reason, User $user
        ) {
                return $this->mPage->doUpdateRestrictions( $limit, $expiry, $cascade, $reason, $user );
        }

        /**
         * @param array $limit
         * @param string $reason
         * @param int &$cascade
         * @param array $expiry
         * @return bool
         */
        public function updateRestrictions( $limit = [], $reason = '',
                &$cascade = 0, $expiry = []
        ) {
                return $this->mPage->doUpdateRestrictions(
                        $limit,
                        $expiry,
                        $cascade,
                        $reason,
                        $this->getContext()->getUser()
                );
        }

        /**
         * @param string $reason
         * @param bool $suppress
         * @param int|null $u1 Unused
         * @param bool|null $u2 Unused
         * @param string &$error
         * @param bool $immediate false allows deleting over time via the job queue
         * @return bool
         * @throws FatalError
         * @throws MWException
         */
        public function doDeleteArticle(
                $reason, $suppress = false, $u1 = null, $u2 = null, &$error = '', $immediate = false
        ) {
                return $this->mPage->doDeleteArticle( $reason, $suppress, $u1, $u2, $error,
                        null, $immediate );
        }

        /**
         * @param string $fromP
         * @param string $summary
         * @param string $token
         * @param bool $bot
         * @param array &$resultDetails
         * @param User|null $user
         * @return array
         */
        public function doRollback( $fromP, $summary, $token, $bot, &$resultDetails, User $user = null ) {
                if ( !$user ) {
                        $user = $this->getContext()->getUser();
                }

                return $this->mPage->doRollback( $fromP, $summary, $token, $bot, $resultDetails, $user );
        }

        /**
         * @param string $fromP
         * @param string $summary
         * @param bool $bot
         * @param array &$resultDetails
         * @param User|null $guser
         * @return array
         */
        public function commitRollback( $fromP, $summary, $bot, &$resultDetails, User $guser = null ) {
                if ( !$guser ) {
                        $guser = $this->getContext()->getUser();
                }

                return $this->mPage->commitRollback( $fromP, $summary, $bot, $resultDetails, $guser );
        }

        /**
         * @param bool &$hasHistory
         * @return mixed
         */
        public function generateReason( &$hasHistory ) {
                $title = $this->mPage->getTitle();
                $handler = ContentHandler::getForTitle( $title );
                return $handler->getAutoDeleteReason( $title, $hasHistory );
        }

        // ******
}