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[mediawiki.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
 */

/**
 * Class for viewing MediaWiki article and history.
 *
 * This maintains WikiPage functions for backwards compatibility.
 *
 * @todo Move and rewrite code to an Action class
 *
 * See design.txt for an overview.
 * Note: edit user interface and cache support functions have been
 * moved to separate EditPage and HTMLFileCache classes.
 *
 * @internal documentation reviewed 15 Mar 2010
 */
class Article implements Page {
        /** @var IContextSource The context this Article is executed in */
        protected $mContext;

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

        /** @var ParserOptions ParserOptions object for $wgUser articles */
        public $mParserOptions;

        /**
         * @var string Text of the revision we are working on
         * @todo BC cruft
         */
        public $mContent;

        /**
         * @var Content Content of the revision we are working on
         * @since 1.21
         */
        public $mContentObject;

        /** @var bool Is the content ($mContent) already loaded? */
        public $mContentLoaded = false;

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

        /** @var Title Title from which we were redirected here */
        public $mRedirectedFrom = null;

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

        /** @var int Revision ID of revision we are working on */
        public $mRevIdFetched = 0;

        /** @var Revision Revision we are working on */
        public $mRevision = null;

        /** @var ParserOutput */
        public $mParserOutput;

        /**
         * Constructor and clear the article
         * @param Title $title Reference to a Title object.
         * @param int $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 );
                # @todo FIXME: Doesn't inherit right
                return $t == null ? null : new self( $t );
                # return $t == null ? null : new static( $t ); // PHP 5.3
        }

        /**
         * 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() ) {
                        // FIXME: where should this go?
                        $title = Title::makeTitle( NS_FILE, $title->getDBkey() );
                }

                $page = null;
                Hooks::run( 'ArticleFromTitle', array( &$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;
        }

        /**
         * 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->mPage->clear();
        }

        /**
         * Note that getContent/loadContent do 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 1.21; use WikiPage::getContent() instead
         *
         * @return string Return the text of this revision
         */
        public function getContent() {
                ContentHandler::deprecated( __METHOD__, '1.21' );
                $content = $this->getContentObject();
                return ContentHandler::getContentText( $content );
        }

        /**
         * Returns a Content object representing the pages effective display content,
         * not necessarily the revision's content!
         *
         * Note that getContent/loadContent do 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.
         *
         * @return Content Return the content of this revision
         *
         * @since 1.21
         */
        protected function getContentObject() {

                if ( $this->mPage->getID() === 0 ) {
                        # 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, 'parsemag' );
                        }
                } else {
                        $this->fetchContentObject();
                        $content = $this->mContentObject;
                }

                return $content;
        }

        /**
         * @return int The oldid of the article that is to be shown, 0 for the current revision
         */
        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 = array( get_class( $this->mPage ), 'newFromID' );
                                                $this->mPage = call_user_func( $function, $this->mRevision->getPage() );
                                        }
                                }
                        }
                }

                if ( $request->getVal( 'direction' ) == 'next' ) {
                        $nextid = $this->getTitle()->getNextRevisionID( $oldid );
                        if ( $nextid ) {
                                $oldid = $nextid;
                                $this->mRevision = null;
                        } else {
                                $this->mRedirectUrl = $this->getTitle()->getFullURL( 'redirect=no' );
                        }
                } elseif ( $request->getVal( 'direction' ) == 'prev' ) {
                        $previd = $this->getTitle()->getPreviousRevisionID( $oldid );
                        if ( $previd ) {
                                $oldid = $previd;
                                $this->mRevision = null;
                        }
                }

                return $oldid;
        }

        /**
         * Load the revision (including text) into this object
         *
         * @deprecated since 1.19; use fetchContent()
         */
        function loadContent() {
                wfDeprecated( __METHOD__, '1.19' );
                $this->fetchContent();
        }

        /**
         * Get text of an article from database
         * Does *NOT* follow redirects.
         *
         * @protected
         * @note This is really internal functionality that should really NOT be
         * used by other functions. For accessing article content, use the WikiPage
         * class, especially WikiBase::getContent(). However, a lot of legacy code
         * uses this method to retrieve page text from the database, so the function
         * has to remain public for now.
         *
         * @return string|bool String containing article contents, or false if null
         * @deprecated since 1.21, use WikiPage::getContent() instead
         */
        function fetchContent() { #BC cruft!
                ContentHandler::deprecated( __METHOD__, '1.21' );

                if ( $this->mContentLoaded && $this->mContent ) {
                        return $this->mContent;
                }

                $content = $this->fetchContentObject();

                if ( !$content ) {
                        return false;
                }

                // @todo Get rid of mContent everywhere!
                $this->mContent = ContentHandler::getContentText( $content );
                ContentHandler::runLegacyHooks( 'ArticleAfterFetchContent', array( &$this, &$this->mContent ) );

                return $this->mContent;
        }

        /**
         * Get text content object
         * Does *NOT* follow redirects.
         * @todo When is this null?
         *
         * @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 ) {
                        return $this->mContentObject;
                }

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

                $oldid = $this->getOldID();

                # Pre-fill content with error message so that if something
                # fails we'll have something telling us what we intended.
                //XXX: this isn't page content but a UI message. horrible.
                $this->mContentObject = new MessageContent( 'missing-revision', array( $oldid ), array() );

                if ( $oldid ) {
                        # $this->mRevision might already be fetched by getOldIDFromRequest()
                        if ( !$this->mRevision ) {
                                $this->mRevision = Revision::newFromId( $oldid );
                                if ( !$this->mRevision ) {
                                        wfDebug( __METHOD__ . " failed to retrieve specified revision, id $oldid\n" );
                                        return false;
                                }
                        }
                } else {
                        if ( !$this->mPage->getLatest() ) {
                                wfDebug( __METHOD__ . " failed to find page data for title " .
                                        $this->getTitle()->getPrefixedText() . "\n" );
                                return false;
                        }

                        $this->mRevision = $this->mPage->getRevision();

                        if ( !$this->mRevision ) {
                                wfDebug( __METHOD__ . " failed to retrieve current page, rev_id " .
                                        $this->mPage->getLatest() . "\n" );
                                return false;
                        }
                }

                // @todo FIXME: Horrible, horrible! This content-loading interface just plain sucks.
                // We should instead work with the Revision object when we need it...
                // Loads if user is allowed
                $content = $this->mRevision->getContent(
                        Revision::FOR_THIS_USER,
                        $this->getContext()->getUser()
                );

                if ( !$content ) {
                        wfDebug( __METHOD__ . " failed to retrieve content of revision " .
                                $this->mRevision->getId() . "\n" );
                        return false;
                }

                $this->mContentObject = $content;
                $this->mRevIdFetched = $this->mRevision->getId();

                Hooks::run( 'ArticleAfterFetchContentObject', array( &$this, &$this->mContentObject ) );

                return $this->mContentObject;
        }

        /**
         * 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.
         *
         * @since 1.19
         * @return Revision|null
         */
        public function getRevisionFetched() {
                $this->fetchContentObject();

                return $this->mRevision;
        }

        /**
         * Use this to fetch the rev ID used on page views
         *
         * @return int Revision ID of last article revision
         */
        public function getRevIdFetched() {
                if ( $this->mRevIdFetched ) {
                        return $this->mRevIdFetched;
                } 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, $wgUseETag, $wgDebugToolbar, $wgMaxRedirects;

                # 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 = ParserCache::singleton();

                $parserOptions = $this->getParserOptions();
                # Render printable version, use printable version cache
                if ( $outputPage->isPrintable() ) {
                        $parserOptions->setIsPrintable( true );
                        $parserOptions->setEditSection( false );
                } elseif ( !$this->isCurrent() || !$this->getTitle()->quickUserCan( 'edit', $user ) ) {
                        $parserOptions->setEditSection( false );
                }

                # Try client and file cache
                if ( !$wgDebugToolbar && $oldid === 0 && $this->mPage->checkTouched() ) {
                        if ( $wgUseETag ) {
                                $outputPage->setETag( $parserCache->getETag( $this, $parserOptions ) );
                        }

                        # Use the greatest of the page's timestamp or the timestamp of any
                        # redirect in the chain (bug 67849)
                        $timestamp = $this->mPage->getTouched();
                        if ( isset( $this->mRedirectedFrom ) ) {
                                $timestamp = max( $timestamp, $this->mRedirectedFrom->getTouched() );

                                # If there can be more than one redirect in the chain, we have
                                # to go through the whole chain too in case an intermediate
                                # redirect was changed.
                                if ( $wgMaxRedirects > 1 ) {
                                        $titles = Revision::newFromTitle( $this->mRedirectedFrom )
                                                ->getContent( Revision::FOR_THIS_USER, $user )
                                                ->getRedirectChain();
                                        $thisTitle = $this->getTitle();
                                        foreach ( $titles as $title ) {
                                                if ( Title::compare( $title, $thisTitle ) === 0 ) {
                                                        break;
                                                }
                                                $timestamp = max( $timestamp, $title->getTouched() );
                                        }
                                }
                        }

                        # Is it client cached?
                        if ( $outputPage->checkLastModified( $timestamp ) ) {
                                wfDebug( __METHOD__ . ": done 304\n" );

                                return;
                        # Try file cache
                        } elseif ( $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->isParserCacheUsed( $parserOptions, $oldid );
                wfDebug( 'Article::view using parser cache: ' . ( $useParserCache ? 'yes' : 'no' ) . "\n" );
                if ( $user->getStubThreshold() ) {
                        wfIncrStats( '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 ( $pass ) {
                                case 1:
                                        Hooks::run( 'ArticleViewHeader', array( &$this, &$outputDone, &$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, $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 );
                                                        # 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:
                                        # This will set $this->mRevision if needed
                                        $this->fetchContentObject();

                                        # Are we looking at an old revision
                                        if ( $oldid && $this->mRevision ) {
                                                $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->getTimestamp() );

                                        # Pages containing custom CSS or JavaScript get special treatment
                                        if ( $this->getTitle()->isCssOrJsPage() || $this->getTitle()->isCssJsSubpage() ) {
                                                wfDebug( __METHOD__ . ": showing CSS/JS source\n" );
                                                $this->showCssOrJsPage();
                                                $outputDone = true;
                                        } elseif ( !Hooks::run( 'ArticleContentViewCustom',
                                                        array( $this->fetchContentObject(), $this->getTitle(), $outputPage ) ) ) {

                                                # Allow extensions do their own custom view for certain pages
                                                $outputDone = true;
                                        } elseif ( !ContentHandler::runLegacyHooks( 'ArticleViewCustom',
                                                        array( $this->fetchContentObject(), $this->getTitle(), $outputPage ) ) ) {

                                                # 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" );

                                        $content = $this->getContentObject();
                                        $poolArticleView = new PoolWorkArticleView( $this->getPage(), $parserOptions,
                                                $this->getRevIdFetched(), $useParserCache, $content );

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

                                                        $errortext = $error->getWikiText( false, 'view-pool-error' );
                                                        $outputPage->addWikiText( '<div class="errorbox">' . $errortext . '</div>' );
                                                }
                                                # Connection or timeout error
                                                return;
                                        }

                                        $this->mParserOutput = $poolArticleView->getParserOutput();
                                        $outputPage->addParserOutput( $this->mParserOutput );
                                        if ( $content->getRedirectTarget() ) {
                                                $outputPage->addSubtitle( "<span id=\"redirectsub\">" .
                                                        $this->getContext()->msg( 'redirectpagesub' )->parse() . "</span>" );
                                        }

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

                                        $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.
                $pOutput = ( $outputDone instanceof ParserOutput )
                        ? $outputDone // object fetched by hook
                        : $this->mParserOutput;

                # 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() );
                        }
                }

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

                $this->showViewFooter();
                $this->mPage->doViewUpdates( $user, $oldid );

                $outputPage->addModules( 'mediawiki.action.view.postEdit' );

        }

        /**
         * Adjust title for pages with displaytitle, -{T|}- or language conversion
         * @param ParserOutput $pOutput
         */
        public function adjustDisplayTitle( ParserOutput $pOutput ) {
                # Adjust the title if it was set by displaytitle, -{T|}- or language conversion
                $titleText = $pOutput->getTitleText();
                if ( strval( $titleText ) !== '' ) {
                        $this->getContext()->getOutput()->setPageTitle( $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->mNewid;
                $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 );
        }

        /**
         * Show a page view for a page formatted as CSS or JavaScript. To be called by
         * Article::view() only.
         *
         * This exists mostly to serve the deprecated ShowRawCssJs hook (used to customize these views).
         * It has been replaced by the ContentGetParserOutput hook, which lets you do the same but with
         * more flexibility.
         *
         * @param bool $showCacheHint Whether to show a message telling the user
         *   to clear the browser cache (default: true).
         */
        protected function showCssOrJsPage( $showCacheHint = true ) {
                $outputPage = $this->getContext()->getOutput();

                if ( $showCacheHint ) {
                        $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'
                        );
                }

                $this->fetchContentObject();

                if ( $this->mContentObject ) {
                        // Give hooks a chance to customise the output
                        if ( ContentHandler::runLegacyHooks(
                                'ShowRawCssJs',
                                array( $this->mContentObject, $this->getTitle(), $outputPage ) )
                        ) {
                                // If no legacy hooks ran, display the content of the parser output, including RL modules,
                                // but excluding metadata like categories and language links
                                $po = $this->mContentObject->getParserOutput( $this->getTitle() );
                                $outputPage->addParserOutputContent( $po );
                        }
                }
        }

        /**
         * 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, $pOutput = null ) {
                global $wgArticleRobotPolicies, $wgNamespaceRobotPolicies, $wgDefaultRobotPolicy;

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

                # Don't index user and user talk pages for blocked users (bug 11443)
                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 ( Block::newFromTarget( $specificTarget, $vagueTarget ) instanceof Block ) {
                                return array(
                                        'index' => 'noindex',
                                        'follow' => 'nofollow'
                                );
                        }
                }

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

                if ( isset( $wgArticleRobotPolicies[$this->getTitle()->getPrefixedText()] ) ) {
                        # (bug 14900) 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 array();
                }

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

                $arr = array();
                foreach ( $policy as $var ) {
                        if ( in_array( $var, array( 'index', 'noindex' ) ) ) {
                                $arr['index'] = $var;
                        } elseif ( in_array( $var, array( '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( $this->mRedirectedFrom ) ) {
                        // This is an internally redirected page view.
                        // We'll need a backlink to the source page for navigation.
                        if ( Hooks::run( 'ArticleViewRedirect', array( &$this ) ) ) {
                                $redir = Linker::linkKnown(
                                        $this->mRedirectedFrom,
                                        null,
                                        array(),
                                        array( '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( array(
                                        'wgInternalRedirectTargetUrl' => $redirectTargetUrl,
                                ) );
                                $outputPage->addModules( 'mediawiki.action.view.redirect' );

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

                                // 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( array(
                                        '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() ) {
                        if ( !wfMessage( 'talkpageheader' )->isDisabled() ) {
                                $this->getContext()->getOutput()->wrapWikiMsg(
                                        "<div class=\"mw-talkpageheader\">\n$1\n</div>",
                                        array( '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', array( $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, $wgEnableAPI, $wgEnableWriteAPI;

                $outputPage = $this->getContext()->getOutput();
                $user = $this->getContext()->getUser();
                $cache = wfGetMainCache();
                $rc = false;

                if ( !$this->getTitle()->quickUserCan( 'patrol', $user )
                        || !( $wgUseRCPatrol || $wgUseNPPatrol )
                ) {
                        // Patrolling is disabled or the user isn't allowed to
                        return false;
                }

                // 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).

                // Check for cached results
                if ( $cache->get( wfMemcKey( 'NotPatrollablePage', $this->getTitle()->getArticleID() ) ) ) {
                        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;
                }

                $dbr = wfGetDB( DB_SLAVE );
                $oldestRevisionTimestamp = $dbr->selectField(
                        'revision',
                        'MIN( rev_timestamp )',
                        array( 'rev_page' => $this->getTitle()->getArticleID() ),
                        __METHOD__
                );

                if ( $oldestRevisionTimestamp
                        && RecentChange::isInRCLifespan( $oldestRevisionTimestamp, 21600 )
                ) {
                        // 6h tolerance because the RC might not be cleaned out regularly
                        $rc = RecentChange::newFromConds(
                                array(
                                        'rc_new' => 1,
                                        'rc_timestamp' => $oldestRevisionTimestamp,
                                        'rc_namespace' => $this->getTitle()->getNamespace(),
                                        'rc_cur_id' => $this->getTitle()->getArticleID(),
                                        'rc_patrolled' => 0
                                ),
                                __METHOD__,
                                array( 'USE INDEX' => 'new_name_timestamp' )
                        );
                }

                if ( !$rc ) {
                        // No 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( wfMemcKey( 'NotPatrollablePage', $this->getTitle()->getArticleID() ), '1' );

                        return false;
                }

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

                $rcid = $rc->getAttribute( 'rc_id' );

                $token = $user->getEditToken( $rcid );

                $outputPage->preventClickjacking();
                if ( $wgEnableAPI && $wgEnableWriteAPI && $user->isAllowed( 'writeapi' ) ) {
                        $outputPage->addModules( 'mediawiki.page.patrol.ajax' );
                }

                $link = Linker::linkKnown(
                        $this->getTitle(),
                        wfMessage( 'markaspatrolledtext' )->escaped(),
                        array(),
                        array(
                                'action' => 'markpatrolled',
                                'rcid' => $rcid,
                                'token' => $token,
                        )
                );

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

                return true;
        }

        /**
         * 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();

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

                        if ( !( $user && $user->isLoggedIn() ) && !$ip ) { # User does not exist
                                $outputPage->wrapWikiMsg( "<div class=\"mw-userpage-userdoesnotexist error\">\n\$1\n</div>",
                                        array( 'userpage-userdoesnotexist-view', wfEscapeWikiText( $rootPart ) ) );
                        } elseif ( !is_null( $block ) && $block->getType() != Block::TYPE_AUTO ) {
                                # Show log extract if the user is currently blocked
                                LogEventsList::showLogExtract(
                                        $outputPage,
                                        'block',
                                        MWNamespace::getCanonicalName( NS_USER ) . ':' . $block->getTarget(),
                                        '',
                                        array(
                                                'lim' => 1,
                                                'showIfEmpty' => false,
                                                'msgKey' => array(
                                                        'blocked-notice-logextract',
                                                        $user->getName() # Support GENDER in notice
                                                )
                                        )
                                );
                                $validUserPage = !$title->isSubpage();
                        } else {
                                $validUserPage = !$title->isSubpage();
                        }
                }

                Hooks::run( 'ShowMissingArticle', array( $this ) );

                // Give extensions a chance to hide their (unrelated) log entries
                $logTypes = array( 'delete', 'move' );
                $conds = array( "log_action != 'revision'" );
                Hooks::run( 'Article::MissingArticleConditions', array( &$conds, $logTypes ) );

                # Show delete and move logs
                LogEventsList::showLogExtract( $outputPage, $logTypes, $title, '',
                        array( 'lim' => 10,
                                'conds' => $conds,
                                'showIfEmpty' => false,
                                'msgKey' => array( 'moveddeleted-notice' ) )
                );

                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()->header( "HTTP/1.1 404 Not Found" );
                }

                // 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', array( $this ) );

                if ( !$hookResult ) {
                        return;
                }

                # Show error message
                $oldid = $this->getOldID();
                if ( $oldid ) {
                        $text = wfMessage( 'missing-revision', $oldid )->plain();
                } elseif ( $title->getNamespace() === NS_MEDIAWIKI ) {
                        // Use the default message text
                        $text = $title->getDefaultMessageText();
                } elseif ( $title->quickUserCan( 'create', $this->getContext()->getUser() )
                        && $title->quickUserCan( 'edit', $this->getContext()->getUser() )
                ) {
                        $message = $this->getContext()->getUser()->isLoggedIn() ? 'noarticletext' : 'noarticletextanon';
                        $text = wfMessage( $message )->plain();
                } else {
                        $text = wfMessage( 'noarticletext-nopermission' )->plain();
                }
                $text = "<div class='noarticletext'>\n$text\n</div>";

                $outputPage->addWikiText( $text );
        }

        /**
         * 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( Revision::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( Revision::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( Revision::DELETED_RESTRICTED ) ?
                                'rev-suppressed-text-unhide' : 'rev-deleted-text-unhide';
                        $outputPage->wrapWikiMsg( "<div class='mw-warning plainlinks'>\n$1\n</div>\n",
                                array( $msg, $link ) );

                        return false;
                // We are allowed to see...
                } else {
                        $msg = $this->mRevision->isDeleted( Revision::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( $oldid = 0 ) {
                if ( !Hooks::run( 'DisplayOldSubtitle', array( &$this, &$oldid ) ) ) {
                        return;
                }

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

                # Cascade unhide param in links for easy deletion browsing
                $extraParams = array();
                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();
                $outputPage->addSubtitle( "<div id=\"mw-{$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(),
                                array(),
                                $extraParams
                        );
                $curdiff = $current
                        ? $context->msg( 'diff' )->escaped()
                        : Linker::linkKnown(
                                $this->getTitle(),
                                $context->msg( 'diff' )->escaped(),
                                array(),
                                array(
                                        'diff' => 'cur',
                                        'oldid' => $oldid
                                ) + $extraParams
                        );
                $prev = $this->getTitle()->getPreviousRevisionID( $oldid );
                $prevlink = $prev
                        ? Linker::linkKnown(
                                $this->getTitle(),
                                $context->msg( 'previousrevision' )->escaped(),
                                array(),
                                array(
                                        'direction' => 'prev',
                                        'oldid' => $oldid
                                ) + $extraParams
                        )
                        : $context->msg( 'previousrevision' )->escaped();
                $prevdiff = $prev
                        ? Linker::linkKnown(
                                $this->getTitle(),
                                $context->msg( 'diff' )->escaped(),
                                array(),
                                array(
                                        'diff' => 'prev',
                                        'oldid' => $oldid
                                ) + $extraParams
                        )
                        : $context->msg( 'diff' )->escaped();
                $nextlink = $current
                        ? $context->msg( 'nextrevision' )->escaped()
                        : Linker::linkKnown(
                                $this->getTitle(),
                                $context->msg( 'nextrevision' )->escaped(),
                                array(),
                                array(
                                        'direction' => 'next',
                                        'oldid' => $oldid
                                ) + $extraParams
                        );
                $nextdiff = $current
                        ? $context->msg( 'diff' )->escaped()
                        : Linker::linkKnown(
                                $this->getTitle(),
                                $context->msg( 'diff' )->escaped(),
                                array(),
                                array(
                                        'diff' => 'next',
                                        'oldid' => $oldid
                                ) + $extraParams
                        );

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

                $outputPage->addSubtitle( "<div id=\"mw-revision-nav\">" . $cdel .
                        $context->msg( 'revision-nav' )->rawParams(
                                $prevdiff, $prevlink, $lnk, $curdiff, $nextlink, $nextdiff
                        )->escaped() . "</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
         */
        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 = array( $target );
                }

                $html = '<ul class="redirectText">';
                /** @var Title $title */
                foreach ( $target as $title ) {
                        $html .= '<li>' . Linker::link(
                                $title,
                                htmlspecialchars( $title->getFullText() ),
                                array(),
                                // Automatically append redirect=no to each link, since most of them are
                                // redirect pages themselves.
                                array( 'redirect' => 'no' ),
                                ( $forceKnown ? array( 'known', 'noclasses' ) : array() )
                        ) . '</li>';
                }
                $html .= '</ul>';

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

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

        /**
         * Handle action=render
         */
        public function render() {
                $this->getContext()->getRequest()->response()->header( 'X-Robots-Tag: noindex' );
                $this->getContext()->getOutput()->setArticleBodyOnly( true );
                $this->getContext()->getOutput()->enableSectionEditLinks( false );
                $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();

                # 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!
                $this->mPage->loadPageData( 'fromdbmaster' );
                if ( !$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>",
                                        array( 'cannotdelete', wfEscapeWikiText( $title->getPrefixedText() ) )
                                );
                        $outputPage->addHTML(
                                Xml::element( 'h2', null, $deleteLogPage->getName()->text() )
                        );
                        LogEventsList::showLogExtract(
                                $outputPage,
                                'delete',
                                $title
                        );

                        return;
                }

                $request = $context->getRequest();
                $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' ),
                        array( 'delete', $this->getTitle()->getPrefixedText() ) )
                ) {
                        # Flag to hide all contents of the archived revisions
                        $suppress = $request->getVal( 'wpSuppress' ) && $user->isAllowed( '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_SLAVE );
                        $revisions = $edits = (int)$dbr->selectField(
                                'revision',
                                'COUNT(rev_page)',
                                array( 'rev_page' => $title->getArticleID() ),
                                __METHOD__
                        );

                        // @todo FIXME: 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(),
                                        array( 'rel' => 'archives' ),
                                        array( 'action' => 'history' ) ) .
                                '</strong>'
                        );

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

                $this->confirmDelete( $reason );
        }

        /**
         * Output deletion confirmation dialog
         * @todo FIXME: 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();
                $useMediaWikiUIEverywhere = $ctx->getConfig()->get( 'UseMediaWikiUIEverywhere' );
                $outputPage->setPageTitle( wfMessage( 'delete-confirm', $title->getPrefixedText() ) );
                $outputPage->addBacklinkSubtitle( $title );
                $outputPage->setRobotPolicy( 'noindex,nofollow' );
                $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' );
                }
                $outputPage->addWikiMsg( 'confirmdeletetext' );

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

                $user = $this->getContext()->getUser();

                if ( $user->isAllowed( 'suppressrevision' ) ) {
                        $suppress = Html::openElement( 'div', array( 'id' => 'wpDeleteSuppressRow' ) ) .
                                "<strong>" .
                                                Xml::checkLabel( wfMessage( 'revdelete-suppress' )->text(),
                                                        'wpSuppress', 'wpSuppress', false, array( 'tabindex' => '4' ) ) .
                                        "</strong>" .
                                Html::closeElement( 'div' );
                } else {
                        $suppress = '';
                }
                $checkWatch = $user->getBoolOption( 'watchdeletion' ) || $user->isWatched( $title );

                $form = Html::openElement( 'form', array( 'method' => 'post',
                        'action' => $title->getLocalURL( 'action=delete' ), 'id' => 'deleteconfirm' ) ) .
                        Html::openElement( 'fieldset', array( 'id' => 'mw-delete-table' ) ) .
                        Html::element( 'legend', null, wfMessage( 'delete-legend' )->text() ) .
                        Html::openElement( 'div', array( 'id' => 'mw-deleteconfirm-table' ) ) .
                        Html::openElement( 'div', array( 'id' => 'wpDeleteReasonListRow' ) ) .
                        Html::label( wfMessage( 'deletecomment' )->text(), 'wpDeleteReasonList' ) .
                        '&nbsp;' .
                        Xml::listDropDown(
                                'wpDeleteReasonList',
                                wfMessage( 'deletereason-dropdown' )->inContentLanguage()->text(),
                                wfMessage( 'deletereasonotherlist' )->inContentLanguage()->text(),
                                '',
                                'wpReasonDropDown',
                                1
                        ) .
                        Html::closeElement( 'div' ) .
                        Html::openElement( 'div', array( 'id' => 'wpDeleteReasonRow' ) ) .
                        Html::label( wfMessage( 'deleteotherreason' )->text(), 'wpReason' ) .
                        '&nbsp;' .
                        Html::input( 'wpReason', $reason, 'text', array(
                                'size' => '60',
                                'maxlength' => '255',
                                'tabindex' => '2',
                                'id' => 'wpReason',
                                'class' => 'mw-ui-input-inline',
                                'autofocus'
                        ) ) .
                        Html::closeElement( 'div' );

                # Disallow watching if user is not logged in
                if ( $user->isLoggedIn() ) {
                        $form .=
                                        Xml::checkLabel( wfMessage( 'watchthis' )->text(),
                                                'wpWatch', 'wpWatch', $checkWatch, array( 'tabindex' => '3' ) );
                }

                $form .=
                                Html::openElement( 'div' ) .
                                $suppress .
                                        Xml::submitButton( wfMessage( 'deletepage' )->text(),
                                                array(
                                                        'name' => 'wpConfirmB',
                                                        'id' => 'wpConfirmB',
                                                        'tabindex' => '5',
                                                        'class' => $useMediaWikiUIEverywhere ? 'mw-ui-button mw-ui-destructive' : '',
                                                )
                                        ) .
                                Html::closeElement( 'div' ) .
                        Html::closeElement( 'div' ) .
                        Xml::closeElement( 'fieldset' ) .
                        Html::hidden(
                                'wpEditToken',
                                $user->getEditToken( array( 'delete', $title->getPrefixedText() ) )
                        ) .
                        Xml::closeElement( 'form' );

                        if ( $user->isAllowed( 'editinterface' ) ) {
                                $dropdownTitle = Title::makeTitle( NS_MEDIAWIKI, 'Deletereason-dropdown' );
                                $link = Linker::link(
                                        $dropdownTitle,
                                        wfMessage( 'delete-edit-reasonlist' )->escaped(),
                                        array(),
                                        array( 'action' => 'edit' )
                                );
                                $form .= '<p class="mw-delete-editreasons">' . $link . '</p>';
                        }

                $outputPage->addHTML( $form );

                $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
         */
        public function doDelete( $reason, $suppress = false ) {
                $error = '';
                $outputPage = $this->getContext()->getOutput();
                $status = $this->mPage->doDeleteArticleReal( $reason, $suppress, 0, true, $error );

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

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

                        $loglink = '[[Special:Log/delete|' . wfMessage( 'deletionlog' )->text() . ']]';

                        $outputPage->addWikiMsg( 'deletedtext', wfEscapeWikiText( $deleted ), $loglink );

                        Hooks::run( 'ArticleDeleteAfterSuccess', array( $this->getTitle(), $outputPage ) );

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

                        if ( $error == '' ) {
                                $outputPage->addWikiText(
                                        "<div class=\"error mw-error-cannotdelete\">\n" . $status->getWikiText() . "\n</div>"
                                );
                                $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( $this->getContext() );
                                return true;
                        } else {
                                wfDebug( "Article::tryFileCache(): starting buffer\n" );
                                ob_start( array( &$cache, 'saveToFileCache' ) );
                        }
                } else {
                        wfDebug( "Article::tryFileCache(): not cacheable\n" );
                }

                return false;
        }

        /**
         * Check if the page can be cached
         * @return bool
         */
        public function isFileCacheable() {
                $cacheable = false;

                if ( HTMLFileCache::useFileCache( $this->getContext() ) ) {
                        $cacheable = $this->mPage->getID()
                                && !$this->mRedirectedFrom && !$this->getTitle()->isRedirect();
                        // Extension may have reason to disable file caching on some pages.
                        if ( $cacheable ) {
                                $cacheable = Hooks::run( 'IsFileCacheable', array( &$this ) );
                        }
                }

                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 WikiPage::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 $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, array( 'mContext', 'mPage' ) ) ) {
                        $this->mPage->$fname = $fvalue;
                } else {
                        trigger_error( 'Inaccessible property via __set(): ' . $fname, E_USER_NOTICE );
                }
        }

        /**
         * Use PHP's magic __call handler to transform instance calls to
         * WikiPage functions for backwards compatibility.
         *
         * @param string $fname Name of called method
         * @param array $args Arguments to the method
         * @return mixed
         */
        public function __call( $fname, $args ) {
                if ( is_callable( array( $this->mPage, $fname ) ) ) {
                        #wfWarn( "Call to " . __CLASS__ . "::$fname; please use WikiPage instead" );
                        return call_user_func_array( array( $this->mPage, $fname ), $args );
                }
                trigger_error( 'Inaccessible function via __call(): ' . $fname, E_USER_ERROR );
        }

        // ****** B/C functions to work-around PHP silliness with __call and references ****** //

        /**
         * @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 = array(), $reason = '',
                &$cascade = 0, $expiry = array()
        ) {
                return $this->mPage->doUpdateRestrictions(
                        $limit,
                        $expiry,
                        $cascade,
                        $reason,
                        $this->getContext()->getUser()
                );
        }

        /**
         * @param string $reason
         * @param bool $suppress
         * @param int $id
         * @param bool $commit
         * @param string $error
         * @return bool
         */
        public function doDeleteArticle( $reason, $suppress = false, $id = 0,
                $commit = true, &$error = ''
        ) {
                return $this->mPage->doDeleteArticle( $reason, $suppress, $id, $commit, $error );
        }

        /**
         * @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 ) {
                $user = is_null( $user ) ? $this->getContext()->getUser() : $user;
                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 ) {
                $guser = is_null( $guser ) ? $this->getContext()->getUser() : $guser;
                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 );
        }

        // ****** B/C functions for static methods ( __callStatic is PHP>=5.3 ) ****** //

        /**
         * @return array
         *
         * @deprecated since 1.24, use WikiPage::selectFields() instead
         */
        public static function selectFields() {
                wfDeprecated( __METHOD__, '1.24' );
                return WikiPage::selectFields();
        }

        /**
         * @param Title $title
         *
         * @deprecated since 1.24, use WikiPage::onArticleCreate() instead
         */
        public static function onArticleCreate( $title ) {
                wfDeprecated( __METHOD__, '1.24' );
                WikiPage::onArticleCreate( $title );
        }

        /**
         * @param Title $title
         *
         * @deprecated since 1.24, use WikiPage::onArticleDelete() instead
         */
        public static function onArticleDelete( $title ) {
                wfDeprecated( __METHOD__, '1.24' );
                WikiPage::onArticleDelete( $title );
        }

        /**
         * @param Title $title
         *
         * @deprecated since 1.24, use WikiPage::onArticleEdit() instead
         */
        public static function onArticleEdit( $title ) {
                wfDeprecated( __METHOD__, '1.24' );
                WikiPage::onArticleEdit( $title );
        }

        /**
         * @param string $oldtext
         * @param string $newtext
         * @param int $flags
         * @return string
         * @deprecated since 1.21, use ContentHandler::getAutosummary() instead
         */
        public static function getAutosummary( $oldtext, $newtext, $flags ) {
                return WikiPage::getAutosummary( $oldtext, $newtext, $flags );
        }
        // ******
}