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

/**
 * 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.
 */
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;

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

	/**
	 * 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 );
		return $t == null ? null : new static( $t );
	}

	/**
	 * Create an Article object of the appropriate class for the given page.
	 *
	 * @param Title $title
	 * @param IContextSource $context
	 * @return Article
	 */
	public static function newFromTitle( $title, IContextSource $context ) {
		if ( NS_MEDIA == $title->getNamespace() ) {
			// FIXME: where should this go?
			$title = Title::makeTitle( NS_FILE, $title->getDBkey() );
		}

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

		return $page;
	}

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

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

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

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

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

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

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

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

	/**
	 * Returns a Content object representing the pages effective display content,
	 * not necessarily the revision's content!
	 *
	 * Note that getContent does not follow redirects anymore.
	 * If you need to fetch redirectable content easily, try
	 * the shortcut in WikiPage::getRedirectTarget()
	 *
	 * This function has side effects! Do not use this function if you
	 * only want the real revision text if any.
	 *
	 * @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 = [ 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;
	}

	/**
	 * 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', [ $oldid ] );

		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 {
			$oldid = $this->mPage->getLatest();
			if ( !$oldid ) {
				wfDebug( __METHOD__ . " failed to find page data for title " .
					$this->getTitle()->getPrefixedText() . "\n" );
				return false;
			}

			# Update error message with correct oldid
			$this->mContentObject = new MessageContent( 'missing-revision', [ $oldid ] );

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

			if ( !$this->mRevision ) {
				wfDebug( __METHOD__ . " failed to retrieve current page, rev_id $oldid\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();

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

		Hooks::run(
			'ArticleAfterFetchContentObject',
			[ &$articlePage, &$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, $wgDebugToolbar;

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

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

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

			return;
		}

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

			return;
		}

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

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

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

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

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

				return;
			}
		}

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

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

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

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

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

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

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

						$outputPage->wrapWikiMsg(
							"<div id='mw-clearyourcache' lang='$lang' dir='$dir' class='mw-content-$dir'>\n$1\n</div>",
							'clearyourcache'
						);
					} elseif ( !Hooks::run( 'ArticleContentViewCustom',
						[ $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( Html::errorBox( $errortext ) );
						}
						# Connection or timeout error
						return;
					}

					$this->mParserOutput = $poolArticleView->getParserOutput();
					$outputPage->addParserOutput( $this->mParserOutput, $poOptions );
					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->setCdnMaxage( 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() );
			}
		}

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

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

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

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

	/**
	 * 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 );
	}

	/**
	 * 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 (T13443)
		if ( ( $ns == NS_USER || $ns == NS_USER_TALK ) && !$this->getTitle()->isSubpage() ) {
			$specificTarget = null;
			$vagueTarget = null;
			$titleText = $this->getTitle()->getText();
			if ( IP::isValid( $titleText ) ) {
				$vagueTarget = $titleText;
			} else {
				$specificTarget = $titleText;
			}
			if ( Block::newFromTarget( $specificTarget, $vagueTarget ) instanceof Block ) {
				return [
					'index' => 'noindex',
					'follow' => 'nofollow'
				];
			}
		}

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

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

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

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

		return $policy;
	}

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

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

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

		return $arr;
	}

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

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

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

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

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

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

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

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

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

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

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

				return true;
			}
		}

		return false;
	}

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

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

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

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

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

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

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

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

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

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

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

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

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

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

			return false;
		}

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

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

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

			return false;
		}

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

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

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

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

		return true;
	}

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

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

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

		$title = $this->getTitle();

		# Show info in user (talk) namespace. Does the user exist? Is he blocked?
		if ( $title->getNamespace() == NS_USER
			|| $title->getNamespace() == NS_USER_TALK
		) {
			$rootPart = explode( '/', $title->getText() )[0];
			$user = User::newFromName( $rootPart, false /* allow IP users */ );
			$ip = User::isIP( $rootPart );
			$block = 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>",
					[ '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(),
					'',
					[
						'lim' => 1,
						'showIfEmpty' => false,
						'msgKey' => [
							'blocked-notice-logextract',
							$user->getName() # Support GENDER in notice
						]
					]
				);
				$validUserPage = !$title->isSubpage();
			} else {
				$validUserPage = !$title->isSubpage();
			}
		}

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

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

			$dbr = wfGetDB( DB_REPLICA );

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

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

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

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

		if ( !$hookResult ) {
			return;
		}

		# Show error message
		$oldid = $this->getOldID();
		if ( !$oldid && $title->getNamespace() === NS_MEDIAWIKI && $title->hasSourceText() ) {
			$outputPage->addParserOutput( $this->getContentObject()->getParserOutput( $title ) );
		} else {
			if ( $oldid ) {
				$text = wfMessage( 'missing-revision', $oldid )->plain();
			} 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();
			}

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

	/**
	 * If the revision requested for view is deleted, check permissions.
	 * Send either an error message or a warning header to the output.
	 *
	 * @return bool True if the view is allowed, false if not.
	 */
	public function showDeletedRevisionHeader() {
		if ( !$this->mRevision->isDeleted( 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",
				[ $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 ) {
		// Avoid PHP 7.1 warning of passing $this by reference
		$articlePage = $this;

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

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

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

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

		$timestamp = $revision->getTimestamp();

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

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

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

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

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

		$lnk = $current
			? $context->msg( 'currentrevisionlink' )->escaped()
			: Linker::linkKnown(
				$this->getTitle(),
				$context->msg( 'currentrevisionlink' )->escaped(),
				[],
				$extraParams
			);
		$curdiff = $current
			? $context->msg( 'diff' )->escaped()
			: Linker::linkKnown(
				$this->getTitle(),
				$context->msg( 'diff' )->escaped(),
				[],
				[
					'diff' => 'cur',
					'oldid' => $oldid
				] + $extraParams
			);
		$prev = $this->getTitle()->getPreviousRevisionID( $oldid );
		$prevlink = $prev
			? Linker::linkKnown(
				$this->getTitle(),
				$context->msg( 'previousrevision' )->escaped(),
				[],
				[
					'direction' => 'prev',
					'oldid' => $oldid
				] + $extraParams
			)
			: $context->msg( 'previousrevision' )->escaped();
		$prevdiff = $prev
			? Linker::linkKnown(
				$this->getTitle(),
				$context->msg( 'diff' )->escaped(),
				[],
				[
					'diff' => 'prev',
					'oldid' => $oldid
				] + $extraParams
			)
			: $context->msg( 'diff' )->escaped();
		$nextlink = $current
			? $context->msg( 'nextrevision' )->escaped()
			: Linker::linkKnown(
				$this->getTitle(),
				$context->msg( 'nextrevision' )->escaped(),
				[],
				[
					'direction' => 'next',
					'oldid' => $oldid
				] + $extraParams
			);
		$nextdiff = $current
			? $context->msg( 'diff' )->escaped()
			: Linker::linkKnown(
				$this->getTitle(),
				$context->msg( 'diff' )->escaped(),
				[],
				[
					'diff' => 'next',
					'oldid' => $oldid
				] + $extraParams
			);

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

			return;
		}

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

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

		if ( $request->wasPosted() && $user->matchEditToken( $request->getVal( 'wpEditToken' ),
			[ 'delete', $this->getTitle()->getPrefixedText() ] )
		) {
			# Flag to hide all contents of the archived revisions
			$suppress = $request->getCheck( 'wpSuppress' ) && $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_REPLICA );
			$revisions = $edits = (int)$dbr->selectField(
				'revision',
				'COUNT(rev_page)',
				[ '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(),
					[],
					[ 'action' => 'history' ] ) .
				'</strong>'
			);

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

		$this->confirmDelete( $reason );
	}

	/**
	 * Output deletion confirmation dialog
	 * @todo 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();
		$outputPage->setPageTitle( wfMessage( 'delete-confirm', $title->getPrefixedText() ) );
		$outputPage->addBacklinkSubtitle( $title );
		$outputPage->setRobotPolicy( 'noindex,nofollow' );
		$outputPage->addModules( 'mediawiki.action.delete' );

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

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

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

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

		$outputPage->enableOOUI();

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

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

		// HTML maxlength uses "UTF-16 code units", which means that characters outside BMP
		// (e.g. emojis) count for two each. This limit is overridden in JS to instead count
		// Unicode codepoints (or 255 UTF-8 bytes for old schema).
		$conf = $this->getContext()->getConfig();
		$oldCommentSchema = $conf->get( 'CommentTableSchemaMigrationStage' ) === MIGRATION_OLD;
		$fields[] = new OOUI\FieldLayout(
			new OOUI\TextInputWidget( [
				'name' => 'wpReason',
				'inputId' => 'wpReason',
				'tabIndex' => 2,
				'maxLength' => $oldCommentSchema ? 255 : CommentStore::COMMENT_CHARACTER_LIMIT,
				'infusable' => true,
				'value' => $reason,
				'autofocus' => true,
			] ),
			[
				'label' => $ctx->msg( 'deleteotherreason' )->text(),
				'align' => 'top',
			]
		);

		if ( $user->isLoggedIn() ) {
			$fields[] = new OOUI\FieldLayout(
				new OOUI\CheckboxInputWidget( [
					'name' => 'wpWatch',
					'inputId' => 'wpWatch',
					'tabIndex' => 3,
					'selected' => $checkWatch,
				] ),
				[
					'label' => $ctx->msg( 'watchthis' )->text(),
					'align' => 'inline',
					'infusable' => true,
				]
			);
		}

		if ( $user->isAllowed( 'suppressrevision' ) ) {
			$fields[] = new OOUI\FieldLayout(
				new OOUI\CheckboxInputWidget( [
					'name' => 'wpSuppress',
					'inputId' => 'wpSuppress',
					'tabIndex' => 4,
				] ),
				[
					'label' => $ctx->msg( 'revdelete-suppress' )->text(),
					'align' => 'inline',
					'infusable' => true,
				]
			);
		}

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

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

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

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

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

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

	/**
	 * Perform a deletion and output success or failure messages
	 * @param string $reason
	 * @param bool $suppress
	 */
	public function doDelete( $reason, $suppress = false ) {
		$error = '';
		$context = $this->getContext();
		$outputPage = $context->getOutput();
		$user = $context->getUser();
		$status = $this->mPage->doDeleteArticleReal( $reason, $suppress, 0, true, $error, $user );

		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', [ $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( $this->getContext() );
				return true;
			} else {
				wfDebug( "Article::tryFileCache(): starting buffer\n" );
				ob_start( [ &$cache, 'saveToFileCache' ] );
			}
		} else {
			wfDebug( "Article::tryFileCache(): not cacheable\n" );
		}

		return false;
	}

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

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

		return $cacheable;
	}

	/**#@-*/

	/**
	 * Lightweight method to get the parser output for a page, checking the parser cache
	 * and so on. Doesn't consider most of the stuff that 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, [ 'mContext', 'mPage' ] ) ) {
			$this->mPage->$fname = $fvalue;
		} else {
			trigger_error( 'Inaccessible property via __set(): ' . $fname, E_USER_NOTICE );
		}
	}

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

	/**
	 * @param string $reason
	 * @param bool $suppress
	 * @param int $u1 Unused
	 * @param bool $u2 Unused
	 * @param string &$error
	 * @return bool
	 */
	public function doDeleteArticle(
		$reason, $suppress = false, $u1 = null, $u2 = null, &$error = ''
	) {
		return $this->mPage->doDeleteArticle( $reason, $suppress, $u1, $u2, $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 );
	}

	// ******
}
