<?php
/**
 * Helper class for the index.php entry point.
 *
 * 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 Liuggio\StatsdClient\Sender\SocketSender;
use MediaWiki\HookContainer\ProtectedHookAccessorTrait;
use MediaWiki\Logger\LoggerFactory;
use MediaWiki\MainConfigNames;
use MediaWiki\MediaWikiServices;
use MediaWiki\Permissions\PermissionStatus;
use MediaWiki\Request\DerivativeRequest;
use MediaWiki\Request\WebResponse;
use MediaWiki\Title\Title;
use MediaWiki\WikiMap\WikiMap;
use Psr\Log\LoggerInterface;
use Wikimedia\AtEase\AtEase;
use Wikimedia\Rdbms\ChronologyProtector;
use Wikimedia\Rdbms\DBConnectionError;
use Wikimedia\ScopedCallback;

/**
 * The MediaWiki class is the helper class for the index.php entry point.
 */
class MediaWiki {
	use ProtectedHookAccessorTrait;

	/** @var IContextSource */
	private $context;
	/** @var Config */
	private $config;
	/** @var int Class DEFER_* constant; how non-blocking post-response tasks should run */
	private $postSendStrategy;

	/** Call fastcgi_finish_request() to make post-send updates async */
	private const DEFER_FASTCGI_FINISH_REQUEST = 1;
	/** Set Content-Length and call ob_end_flush()/flush() to make post-send updates async */
	private const DEFER_SET_LENGTH_AND_FLUSH = 2;
	/** Do not try to make post-send updates async (e.g. for CLI mode) */
	private const DEFER_CLI_MODE = 3;

	/**
	 * @param IContextSource|null $context
	 */
	public function __construct( IContextSource $context = null ) {
		$this->context = $context ?: RequestContext::getMain();
		$this->config = $this->context->getConfig();

		if ( $GLOBALS['wgCommandLineMode'] ) {
			$this->postSendStrategy = self::DEFER_CLI_MODE;
		} elseif ( function_exists( 'fastcgi_finish_request' ) ) {
			$this->postSendStrategy = self::DEFER_FASTCGI_FINISH_REQUEST;
		} else {
			$this->postSendStrategy = self::DEFER_SET_LENGTH_AND_FLUSH;
		}
	}

	/**
	 * Parse the request to get the Title object
	 *
	 * @throws MalformedTitleException If a title has been provided by the user, but is invalid.
	 * @return Title Title object to be $wgTitle
	 */
	private function parseTitle() {
		$request = $this->context->getRequest();
		$curid = $request->getInt( 'curid' );
		$title = $request->getText( 'title' );

		$ret = null;
		if ( $curid ) {
			// URLs like this are generated by RC, because rc_title isn't always accurate
			$ret = Title::newFromID( $curid );
		}
		if ( $ret === null ) {
			$ret = Title::newFromURL( $title );
			if ( $ret !== null ) {
				// Alias NS_MEDIA page URLs to NS_FILE...we only use NS_MEDIA
				// in wikitext links to tell Parser to make a direct file link
				if ( $ret->getNamespace() === NS_MEDIA ) {
					$ret = Title::makeTitle( NS_FILE, $ret->getDBkey() );
				}
				// Check variant links so that interwiki links don't have to worry
				// about the possible different language variants
				$services = MediaWikiServices::getInstance();
				$languageConverter = $services
					->getLanguageConverterFactory()
					->getLanguageConverter( $services->getContentLanguage() );
				if ( $languageConverter->hasVariants() && !$ret->exists() ) {
					$languageConverter->findVariantLink( $title, $ret );
				}
			}
		}

		// If title is not provided, always allow oldid and diff to set the title.
		// If title is provided, allow oldid and diff to override the title, unless
		// we are talking about a special page which might use these parameters for
		// other purposes.
		if ( $ret === null || !$ret->isSpecialPage() ) {
			// We can have urls with just ?diff=,?oldid= or even just ?diff=
			$oldid = $request->getInt( 'oldid' );
			$oldid = $oldid ?: $request->getInt( 'diff' );
			// Allow oldid to override a changed or missing title
			if ( $oldid ) {
				$revRecord = MediaWikiServices::getInstance()
					->getRevisionLookup()
					->getRevisionById( $oldid );
				if ( $revRecord ) {
					$ret = Title::newFromLinkTarget(
						$revRecord->getPageAsLinkTarget()
					);
				}
			}
		}

		if ( $ret === null && $request->getCheck( 'search' ) ) {
			// Compatibility with old search URLs which didn't use Special:Search
			// Just check for presence here, so blank requests still
			// show the search page when using ugly URLs (T10054).
			$ret = SpecialPage::getTitleFor( 'Search' );
		}

		// Use the main page as default title if nothing else has been provided
		if ( $ret === null
			&& strval( $title ) === ''
			&& !$request->getCheck( 'curid' )
			&& $request->getRawVal( 'action' ) !== 'delete'
		) {
			$ret = Title::newMainPage();
		}

		if ( $ret === null || ( $ret->getDBkey() == '' && !$ret->isExternal() ) ) {
			// If we get here, we definitely don't have a valid title; throw an exception.
			// Try to get detailed invalid title exception first, fall back to MalformedTitleException.
			Title::newFromTextThrow( $title );
			throw new MalformedTitleException( 'badtitletext', $title );
		}

		return $ret;
	}

	/**
	 * Get the Title object that we'll be acting on, as specified in the WebRequest
	 * @return Title
	 */
	public function getTitle() {
		if ( !$this->context->hasTitle() ) {
			try {
				$this->context->setTitle( $this->parseTitle() );
			} catch ( MalformedTitleException $ex ) {
				$this->context->setTitle( SpecialPage::getTitleFor( 'Badtitle' ) );
			}
		}
		return $this->context->getTitle();
	}

	/**
	 * Returns the name of the action that will be executed.
	 *
	 * @return string Action
	 */
	public function getAction(): string {
		return $this->context->getActionName();
	}

	/**
	 * Performs the request.
	 * - bad titles
	 * - read restriction
	 * - local interwiki redirects
	 * - redirect loop
	 * - special pages
	 * - normal pages
	 *
	 * @throws PermissionsError|BadTitleError|HttpError
	 * @return void
	 */
	private function performRequest() {
		global $wgTitle;

		$request = $this->context->getRequest();
		$output = $this->context->getOutput();

		if ( $request->getRawVal( 'printable' ) === 'yes' ) {
			$output->setPrintable();
		}

		$user = $this->context->getUser();
		$title = $this->context->getTitle();
		$requestTitle = $title;
		$this->getHookRunner()->onBeforeInitialize( $title, null, $output, $user, $request, $this );

		// Invalid titles. T23776: The interwikis must redirect even if the page name is empty.
		if ( $title === null || ( $title->getDBkey() == '' && !$title->isExternal() )
			|| $title->isSpecial( 'Badtitle' )
		) {
			$this->context->setTitle( SpecialPage::getTitleFor( 'Badtitle' ) );
			try {
				$this->parseTitle();
			} catch ( MalformedTitleException $ex ) {
				throw new BadTitleError( $ex );
			}
			throw new BadTitleError();
		}

		// Check user's permissions to read this page.
		// We have to check here to catch special pages etc.
		// We will check again in Article::view().
		$permissionStatus = PermissionStatus::newEmpty();
		if ( !$this->context->getAuthority()->authorizeRead( 'read', $title, $permissionStatus ) ) {
			// T34276: allowing the skin to generate output with $wgTitle or
			// $this->context->title set to the input title would allow anonymous users to
			// determine whether a page exists, potentially leaking private data. In fact, the
			// curid and oldid request  parameters would allow page titles to be enumerated even
			// when they are not guessable. So we reset the title to Special:Badtitle before the
			// permissions error is displayed.

			// The skin mostly uses $this->context->getTitle() these days, but some extensions
			// still use $wgTitle.
			$badTitle = SpecialPage::getTitleFor( 'Badtitle' );
			$this->context->setTitle( $badTitle );
			$wgTitle = $badTitle;

			throw new PermissionsError( 'read', $permissionStatus );
		}

		// Interwiki redirects
		if ( $title->isExternal() ) {
			$rdfrom = $request->getVal( 'rdfrom' );
			if ( $rdfrom ) {
				$url = $title->getFullURL( [ 'rdfrom' => $rdfrom ] );
			} else {
				$query = $request->getValues();
				unset( $query['title'] );
				$url = $title->getFullURL( $query );
			}
			// Check for a redirect loop
			if ( !preg_match( '/^' . preg_quote( $this->config->get( MainConfigNames::Server ), '/' ) . '/', $url )
				&& $title->isLocal()
			) {
				// 301 so google et al report the target as the actual url.
				$output->redirect( $url, 301 );
			} else {
				$this->context->setTitle( SpecialPage::getTitleFor( 'Badtitle' ) );
				try {
					$this->parseTitle();
				} catch ( MalformedTitleException $ex ) {
					throw new BadTitleError( $ex );
				}
				throw new BadTitleError();
			}
		// Handle any other redirects.
		// Redirect loops, titleless URL, $wgUsePathInfo URLs, and URLs with a variant
		} elseif ( !$this->tryNormaliseRedirect( $title ) ) {
			// Prevent information leak via Special:MyPage et al (T109724)
			$spFactory = MediaWikiServices::getInstance()->getSpecialPageFactory();
			if ( $title->isSpecialPage() ) {
				$specialPage = $spFactory->getPage( $title->getDBkey() );
				if ( $specialPage instanceof RedirectSpecialPage ) {
					$specialPage->setContext( $this->context );
					if ( $this->config->get( MainConfigNames::HideIdentifiableRedirects )
						&& $specialPage->personallyIdentifiableTarget()
					) {
						[ , $subpage ] = $spFactory->resolveAlias( $title->getDBkey() );
						$target = $specialPage->getRedirect( $subpage );
						// Target can also be true. We let that case fall through to normal processing.
						if ( $target instanceof Title ) {
							if ( $target->isExternal() ) {
								// Handle interwiki redirects
								$target = SpecialPage::getTitleFor(
									'GoToInterwiki',
									'force/' . $target->getPrefixedDBkey()
								);
							}

							$query = $specialPage->getRedirectQuery( $subpage ) ?: [];
							$derivateRequest = new DerivativeRequest( $request, $query );
							$derivateRequest->setRequestURL( $request->getRequestURL() );
							$this->context->setRequest( $derivateRequest );
							// Do not varnish cache these. May vary even for anons
							$output->lowerCdnMaxage( 0 );
							// NOTE: This also clears any action cache.
							// Action should not have been computed yet, but if it was,
							// we reset it because special pages only support "view".
							$this->context->setTitle( $target );
							$wgTitle = $target;
							$title = $target;
							$output->addJsConfigVars( [
								'wgInternalRedirectTargetUrl' => $target->getLinkURL( $query ),
							] );
							$output->addModules( 'mediawiki.action.view.redirect' );

							// If the title is invalid, redirect but show the correct bad title error - T297407
							if ( !$target->isValid() ) {
								try {
									MediaWikiServices::getInstance()->getTitleParser()
										->parseTitle( $target->getPrefixedText() );
								} catch ( MalformedTitleException $ex ) {
									throw new BadTitleError( $ex );
								}
								throw new BadTitleError();
							}
						}
					}
				}
			}

			// Special pages ($title may have changed since if statement above)
			if ( $title->isSpecialPage() ) {
				// Actions that need to be made when we have a special pages
				$spFactory->executePath( $title, $this->context );
			} else {
				// ...otherwise treat it as an article view. The article
				// may still be a wikipage redirect to another article or URL.
				$article = $this->initializeArticle();
				if ( is_object( $article ) ) {
					$this->performAction( $article, $requestTitle );
				} elseif ( is_string( $article ) ) {
					$output->redirect( $article );
				} else {
					throw new UnexpectedValueException( "Shouldn't happen: MediaWiki::initializeArticle()"
						. " returned neither an object nor a URL" );
				}
			}
			$output->considerCacheSettingsFinal();
		}
	}

	/**
	 * Handle redirects for uncanonical title requests.
	 *
	 * Handles:
	 * - Redirect loops.
	 * - No title in URL.
	 * - $wgUsePathInfo URLs.
	 * - URLs with a variant.
	 * - Other non-standard URLs (as long as they have no extra query parameters).
	 *
	 * Behaviour:
	 * - Normalise title values:
	 *   /wiki/Foo%20Bar -> /wiki/Foo_Bar
	 * - Normalise empty title:
	 *   /wiki/ -> /wiki/Main
	 *   /w/index.php?title= -> /wiki/Main
	 * - Don't redirect anything with query parameters other than 'title' or 'action=view'.
	 *
	 * @param Title $title
	 * @return bool True if a redirect was set.
	 * @throws HttpError
	 */
	private function tryNormaliseRedirect( Title $title ) {
		$request = $this->context->getRequest();
		$output = $this->context->getOutput();

		if ( $request->getRawVal( 'action', 'view' ) != 'view'
			|| $request->wasPosted()
			|| ( $request->getCheck( 'title' )
				&& $title->getPrefixedDBkey() == $request->getText( 'title' ) )
			|| count( $request->getValueNames( [ 'action', 'title' ] ) )
			|| !$this->getHookRunner()->onTestCanonicalRedirect( $request, $title, $output )
		) {
			return false;
		}

		if ( $this->config->get( MainConfigNames::MainPageIsDomainRoot ) && $request->getRequestURL() === '/' ) {
			return false;
		}

		if ( $title->isSpecialPage() ) {
			[ $name, $subpage ] = MediaWikiServices::getInstance()->getSpecialPageFactory()->
				resolveAlias( $title->getDBkey() );
			if ( $name ) {
				$title = SpecialPage::getTitleFor( $name, $subpage );
			}
		}
		// Redirect to canonical url, make it a 301 to allow caching
		$targetUrl = wfExpandUrl( $title->getFullURL(), PROTO_CURRENT );
		if ( $targetUrl == $request->getFullRequestURL() ) {
			$message = "Redirect loop detected!\n\n" .
				"This means the wiki got confused about what page was " .
				"requested; this sometimes happens when moving a wiki " .
				"to a new server or changing the server configuration.\n\n";

			if ( $this->config->get( MainConfigNames::UsePathInfo ) ) {
				$message .= "The wiki is trying to interpret the page " .
					"title from the URL path portion (PATH_INFO), which " .
					"sometimes fails depending on the web server. Try " .
					"setting \"\$wgUsePathInfo = false;\" in your " .
					"LocalSettings.php, or check that \$wgArticlePath " .
					"is correct.";
			} else {
				$message .= "Your web server was detected as possibly not " .
					"supporting URL path components (PATH_INFO) correctly; " .
					"check your LocalSettings.php for a customized " .
					"\$wgArticlePath setting and/or toggle \$wgUsePathInfo " .
					"to true.";
			}
			throw new HttpError( 500, $message );
		}
		$output->setCdnMaxage( 1200 );
		$output->redirect( $targetUrl, '301' );
		return true;
	}

	/**
	 * Initialize the main Article object for "standard" actions (view, etc)
	 * Create an Article object for the page, following redirects if needed.
	 *
	 * @return Article|string An Article, or a string to redirect to another URL
	 */
	private function initializeArticle() {
		$title = $this->context->getTitle();
		$services = MediaWikiServices::getInstance();
		if ( $this->context->canUseWikiPage() ) {
			// Optimization: Reuse the WikiPage instance from context, to avoid
			// repeat fetching or computation of data already loaded.
			$page = $this->context->getWikiPage();
		} else {
			// This case should not happen, but just in case.
			// @TODO: remove this or use an exception
			$page = $services->getWikiPageFactory()->newFromTitle( $title );
			$this->context->setWikiPage( $page );
			wfWarn( "RequestContext::canUseWikiPage() returned false" );
		}

		// Make GUI wrapper for the WikiPage
		$article = Article::newFromWikiPage( $page, $this->context );

		// Skip some unnecessary code if the content model doesn't support redirects
		// Use the page content model rather than invoking Title::getContentModel()
		// to avoid querying page data twice (T206498)
		if ( !$page->getContentHandler()->supportsRedirects() ) {
			return $article;
		}

		$request = $this->context->getRequest();

		// Namespace might change when using redirects
		// Check for redirects ...
		$action = $request->getRawVal( 'action', 'view' );
		$file = ( $page instanceof WikiFilePage ) ? $page->getFile() : null;
		if ( ( $action == 'view' || $action == 'render' ) // ... for actions that show content
			&& !$request->getCheck( 'oldid' ) // ... and are not old revisions
			&& !$request->getCheck( 'diff' ) // ... and not when showing diff
			&& $request->getRawVal( 'redirect' ) !== 'no' // ... unless explicitly told not to
			// ... and the article is not a non-redirect image page with associated file
			&& !( is_object( $file ) && $file->exists() && !$file->getRedirected() )
		) {
			// Give extensions a change to ignore/handle redirects as needed
			$ignoreRedirect = $target = false;

			$this->getHookRunner()->onInitializeArticleMaybeRedirect( $title, $request,
				// @phan-suppress-next-line PhanTypeMismatchArgument Type mismatch on pass-by-ref args
				$ignoreRedirect, $target, $article );
			$page = $article->getPage(); // reflect any hook changes

			// Follow redirects only for... redirects.
			// If $target is set, then a hook wanted to redirect.
			if ( !$ignoreRedirect && ( $target || $page->isRedirect() ) ) {
				// Is the target already set by an extension?
				$target = $target ?: $page->followRedirect();
				if ( is_string( $target ) && !$this->config->get( MainConfigNames::DisableHardRedirects ) ) {
					// we'll need to redirect
					return $target;
				}
				if ( is_object( $target ) ) {
					// Rewrite environment to redirected article
					$rpage = $services->getWikiPageFactory()->newFromTitle( $target );
					$rpage->loadPageData();
					if ( $rpage->exists() || ( is_object( $file ) && !$file->isLocal() ) ) {
						$rarticle = Article::newFromWikiPage( $rpage, $this->context );
						$rarticle->setRedirectedFrom( $title );

						$article = $rarticle;
						// NOTE: This also clears any action cache
						//
						// Temporarily silence "Unexpected clearActionName after getActionName"
						// warnings until FlaggedRevs is fixed to not rely on computed
						// RequestContext::getActionName (T323254).
						//
						// phpcs:ignore Generic.PHP.NoSilencedErrors.Discouraged
						@$this->context->setTitle( $target );
						$this->context->setWikiPage( $article->getPage() );
					}
				}
			}
		}

		return $article;
	}

	/**
	 * Perform one of the "standard" actions
	 *
	 * @param Article $article
	 * @param Title $requestTitle The original title, before any redirects were applied
	 */
	private function performAction( Article $article, Title $requestTitle ) {
		$request = $this->context->getRequest();
		$output = $this->context->getOutput();
		$title = $this->context->getTitle();
		$user = $this->context->getUser();

		if ( !$this->getHookRunner()->onMediaWikiPerformAction(
			$output, $article, $title, $user, $request, $this )
		) {
			return;
		}

		$t = microtime( true );
		$actionName = $this->getAction();
		$services = MediaWikiServices::getInstance();
		$action = $services->getActionFactory()->getAction( $actionName, $article, $this->context );

		if ( $action instanceof Action ) {
			// Check read permissions
			if ( $action->needsReadRights() && !$user->isAllowed( 'read' ) ) {
				throw new PermissionsError( 'read' );
			}

			// Narrow DB query expectations for this HTTP request
			if ( $request->wasPosted() && !$action->doesWrites() ) {
				$trxProfiler = Profiler::instance()->getTransactionProfiler();
				$trxLimits = $this->config->get( MainConfigNames::TrxProfilerLimits );
				$trxProfiler->setExpectations( $trxLimits['POST-nonwrite'], __METHOD__ );
				$request->markAsSafeRequest();
			}

			// Let CDN cache things if we can purge them.
			// Also unconditionally cache page views.
			if ( $this->config->get( MainConfigNames::UseCdn ) ) {
				$htmlCacheUpdater = $services->getHtmlCacheUpdater();
				if ( $request->matchURLForCDN( $htmlCacheUpdater->getUrls( $requestTitle ) ) ) {
					$output->setCdnMaxage( $this->config->get( MainConfigNames::CdnMaxAge ) );
				} elseif ( $action instanceof ViewAction ) {
					$output->setCdnMaxage( 3600 );
				}
			}

			$action->show();

			$runTime = microtime( true ) - $t;
			$services->getStatsdDataFactory()->timing(
				'action.' . strtr( $actionName, '.', '_' ) . '.executeTiming',
				1000 * $runTime
			);
			return;
		}

		// If we've not found out which action it is by now, it's unknown
		$output->setStatusCode( 404 );
		$output->showErrorPage( 'nosuchaction', 'nosuchactiontext' );
	}

	/**
	 * Run the current MediaWiki instance; index.php just calls this
	 */
	public function run() {
		try {
			$this->main();
		} catch ( Exception $e ) {
			$context = $this->context;
			$action = $context->getRequest()->getRawVal( 'action', 'view' );
			if (
				$e instanceof DBConnectionError &&
				$context->hasTitle() &&
				$context->getTitle()->canExist() &&
				in_array( $action, [ 'view', 'history' ], true ) &&
				HTMLFileCache::useFileCache( $context, HTMLFileCache::MODE_OUTAGE )
			) {
				// Try to use any (even stale) file during outages...
				$cache = new HTMLFileCache( $context->getTitle(), $action );
				if ( $cache->isCached() ) {
					$cache->loadFromFileCache( $context, HTMLFileCache::MODE_OUTAGE );
					print MWExceptionRenderer::getHTML( $e );
					exit;
				}
			}
			MWExceptionHandler::handleException( $e, MWExceptionHandler::CAUGHT_BY_ENTRYPOINT );
		} catch ( Throwable $e ) {
			// Type errors and such: at least handle it now and clean up the LBFactory state
			MWExceptionHandler::handleException( $e, MWExceptionHandler::CAUGHT_BY_ENTRYPOINT );
		}

		$this->doPostOutputShutdown();
	}

	/**
	 * If enabled, after everything specific to this request is done, occasionally run jobs
	 */
	private function schedulePostSendJobs() {
		$jobRunRate = $this->config->get( MainConfigNames::JobRunRate );
		if (
			// Post-send job running disabled
			$jobRunRate <= 0 ||
			// Recursion guard for $wgRunJobsAsync
			$this->getTitle()->isSpecial( 'RunJobs' ) ||
			// Jobs cannot run due to site read-only mode
			MediaWikiServices::getInstance()->getReadOnlyMode()->isReadOnly() ||
			// HTTP response body and Content-Length headers likely to not match,
			// causing post-send updates to block the client when using mod_php
			$this->context->getRequest()->getMethod() === 'HEAD' ||
			$this->context->getRequest()->getHeader( 'If-Modified-Since' ) ||
			$this->context->getRequest()->getHeader( 'If-None-Match' )
		) {
			return;
		}

		if ( $jobRunRate < 1 ) {
			$max = mt_getrandmax();
			if ( mt_rand( 0, $max ) > $max * $jobRunRate ) {
				return; // the higher the job run rate, the less likely we return here
			}
			$n = 1;
		} else {
			$n = intval( $jobRunRate );
		}

		// Note that DeferredUpdates will catch and log any errors (T88312)
		DeferredUpdates::addUpdate( new TransactionRoundDefiningUpdate( function () use ( $n ) {
			$logger = LoggerFactory::getInstance( 'runJobs' );
			if ( $this->config->get( MainConfigNames::RunJobsAsync ) ) {
				// Send an HTTP request to the job RPC entry point if possible
				$invokedWithSuccess = $this->triggerAsyncJobs( $n, $logger );
				if ( !$invokedWithSuccess ) {
					// Fall back to blocking on running the job(s)
					$logger->warning( "Jobs switched to blocking; Special:RunJobs disabled" );
					$this->triggerSyncJobs( $n );
				}
			} else {
				$this->triggerSyncJobs( $n );
			}
		}, __METHOD__ ) );
	}

	/**
	 * @see MediaWiki::preOutputCommit()
	 * @since 1.26
	 */
	private function doPreOutputCommit() {
		self::preOutputCommit( $this->context );
	}

	/**
	 * This function commits all DB and session changes as needed *before* the
	 * client can receive a response (in case DB commit fails) and thus also before
	 * the response can trigger a subsequent related request by the client
	 *
	 * If there is a significant amount of content to flush, it can be done in $postCommitWork
	 *
	 * @param IContextSource $context
	 * @param callable|null $postCommitWork Unused as of MediaWiki 1.39
	 * @since 1.27
	 */
	public static function preOutputCommit(
		IContextSource $context, $postCommitWork = null
	) {
		$config = $context->getConfig();
		$request = $context->getRequest();
		$output = $context->getOutput();
		$services = MediaWikiServices::getInstance();
		$lbFactory = $services->getDBLoadBalancerFactory();

		// Try to make sure that all RDBMs, session, and other storage updates complete
		ignore_user_abort( true );

		// Commit all RDBMs changes from the main transaction round
		$lbFactory->commitPrimaryChanges(
			__METHOD__,
			// Abort if any transaction was too big
			$config->get( MainConfigNames::MaxUserDBWriteDuration )
		);
		wfDebug( __METHOD__ . ': primary transaction round committed' );

		// Run updates that need to block the client or affect output (this is the last chance)
		DeferredUpdates::doUpdates(
			$config->get( MainConfigNames::ForceDeferredUpdatesPreSend )
				? DeferredUpdates::ALL
				: DeferredUpdates::PRESEND
		);

		wfDebug( __METHOD__ . ': pre-send deferred updates completed' );

		// Persist the session to avoid race conditions on subsequent requests by the client
		$request->getSession()->save(); // T214471
		wfDebug( __METHOD__ . ': session changes committed' );

		// Subsequent requests by the client should see the DB replication positions written
		// during the shutdown() call below, even if the position store itself has asynchronous
		// replication. Setting the cpPosIndex cookie is normally enough. However, this might not
		// work for cross-domain redirects to foreign wikis, so set the ?cpPoxIndex in that case.
		$isCrossWikiRedirect = (
			$output->getRedirect() &&
			$lbFactory->hasOrMadeRecentPrimaryChanges( INF ) &&
			self::getUrlDomainDistance( $output->getRedirect() ) === 'remote'
		);

		// Persist replication positions for DBs modified by this request (at this point).
		// These help provide "session consistency" for the client on their next requests.
		$cpIndex = null;
		$cpClientId = null;
		$lbFactory->shutdown(
			$lbFactory::SHUTDOWN_NORMAL,
			null,
			$cpIndex,
			$cpClientId
		);
		$now = time();

		$allowHeaders = !( $output->isDisabled() || headers_sent() );

		if ( $cpIndex > 0 ) {
			if ( $allowHeaders ) {
				$expires = $now + ChronologyProtector::POSITION_COOKIE_TTL;
				$options = [ 'prefix' => '' ];
				$value = $lbFactory::makeCookieValueFromCPIndex( $cpIndex, $now, $cpClientId );
				$request->response()->setCookie( 'cpPosIndex', $value, $expires, $options );
			}

			if ( $isCrossWikiRedirect ) {
				if ( $output->getRedirect() ) {
					$safeUrl = $lbFactory->appendShutdownCPIndexAsQuery(
						$output->getRedirect(),
						$cpIndex
					);
					$output->redirect( $safeUrl );
				} else {
					MWExceptionHandler::logException(
						new LogicException( "No redirect; cannot append cpPosIndex parameter." ),
						MWExceptionHandler::CAUGHT_BY_ENTRYPOINT
					);
				}
			}
		}

		if ( $allowHeaders ) {
			// Set a cookie to tell all CDN edge nodes to "stick" the user to the DC that
			// handles this POST request (e.g. the "primary" data center). Also have the user
			// briefly bypass CDN so ChronologyProtector works for cacheable URLs.
			if ( $request->wasPosted() && $lbFactory->hasOrMadeRecentPrimaryChanges() ) {
				$expires = $now + max(
					ChronologyProtector::POSITION_COOKIE_TTL,
					$config->get( MainConfigNames::DataCenterUpdateStickTTL )
				);
				$options = [ 'prefix' => '' ];
				$request->response()->setCookie( 'UseDC', 'master', $expires, $options );
				$request->response()->setCookie( 'UseCDNCache', 'false', $expires, $options );
			}

			// Avoid letting a few seconds of replica DB lag cause a month of stale data.
			// This logic is also intimately related to the value of $wgCdnReboundPurgeDelay.
			if ( $lbFactory->laggedReplicaUsed() ) {
				$maxAge = $config->get( MainConfigNames::CdnMaxageLagged );
				$output->lowerCdnMaxage( $maxAge );
				$request->response()->header( "X-Database-Lagged: true" );
				wfDebugLog( 'replication',
					"Lagged DB used; CDN cache TTL limited to $maxAge seconds" );
			}

			// Avoid long-term cache pollution due to message cache rebuild timeouts (T133069)
			if ( $services->getMessageCache()->isDisabled() ) {
				$maxAge = $config->get( MainConfigNames::CdnMaxageSubstitute );
				$output->lowerCdnMaxage( $maxAge );
				$request->response()->header( "X-Response-Substitute: true" );
			}

			if ( !$output->couldBePublicCached() || $output->haveCacheVaryCookies() ) {
				// Autoblocks: If this user is autoblocked (and the cookie block feature is enabled
				// for autoblocks), then set a cookie to track this block.
				// This has to be done on all logged-in page loads (not just upon saving edits),
				// because an autoblocked editor might not edit again from the same IP address.
				//
				// IP blocks: For anons, if their IP is blocked (and cookie block feature is enabled
				// for IP blocks), we also want to set the cookie whenever it is safe to do.
				// Basically from any url that are definitely not publicly cacheable (like viewing
				// EditPage), or when the HTTP response is personalised for other reasons (e.g. viewing
				// articles within the same browsing session after making an edit).
				$user = $context->getUser();
				$services->getBlockManager()
					->trackBlockWithCookie( $user, $request->response() );
			}
		}
	}

	/**
	 * @param string $url
	 * @return string Either "local", "remote" if in the farm, "external" otherwise
	 */
	private static function getUrlDomainDistance( $url ) {
		$clusterWiki = WikiMap::getWikiFromUrl( $url );
		if ( WikiMap::isCurrentWikiId( $clusterWiki ) ) {
			return 'local'; // the current wiki
		}
		if ( $clusterWiki !== false ) {
			return 'remote'; // another wiki in this cluster/farm
		}

		return 'external';
	}

	/**
	 * This function does work that can be done *after* the
	 * user gets the HTTP response so they don't block on it
	 *
	 * This manages deferred updates, job insertion,
	 * final commit, and the logging of profiling data
	 *
	 * @since 1.26
	 */
	public function doPostOutputShutdown() {
		// Record backend request timing
		$timing = $this->context->getTiming();
		$timing->mark( 'requestShutdown' );

		// Defer everything else if possible...
		if ( $this->postSendStrategy === self::DEFER_FASTCGI_FINISH_REQUEST ) {
			// Flush the output to the client, continue processing, and avoid further output
			fastcgi_finish_request();
		} elseif ( $this->postSendStrategy === self::DEFER_SET_LENGTH_AND_FLUSH ) {
			// Flush the output to the client, continue processing, and avoid further output
			if ( ob_get_level() ) {
				// phpcs:ignore Generic.PHP.NoSilencedErrors.Discouraged
				@ob_end_flush();
			}
			// Flush the web server output buffer to the client/proxy if possible
			// phpcs:ignore Generic.PHP.NoSilencedErrors.Discouraged
			@flush();
		}

		// Since the headers and output where already flushed, disable WebResponse setters
		// during post-send processing to warnings and unexpected behavior (T191537)
		WebResponse::disableForPostSend();
		// Run post-send updates while preventing further output...
		ob_start( static function () {
			return ''; // do not output uncaught exceptions
		} );
		try {
			$this->restInPeace();
		} catch ( Throwable $e ) {
			MWExceptionHandler::rollbackPrimaryChangesAndLog(
				$e,
				MWExceptionHandler::CAUGHT_BY_ENTRYPOINT
			);
		}
		$length = ob_get_length();
		if ( $length > 0 ) {
			trigger_error( __METHOD__ . ": suppressed $length byte(s)", E_USER_NOTICE );
		}
		ob_end_clean();
	}

	/**
	 * Determine and send the response headers and body for this web request
	 */
	private function main() {
		global $wgTitle;

		// Get title from request parameters,
		// is set on the fly by parseTitle the first time.
		$title = $this->getTitle();
		$wgTitle = $title;

		$request = $this->context->getRequest();
		// Set DB query expectations for this HTTP request
		$trxLimits = $this->config->get( MainConfigNames::TrxProfilerLimits );
		$trxProfiler = Profiler::instance()->getTransactionProfiler();
		$trxProfiler->setLogger( LoggerFactory::getInstance( 'rdbms' ) );
		$statsFactory = MediaWikiServices::getInstance()->getStatsdDataFactory();
		$trxProfiler->setStatsdDataFactory( $statsFactory );
		$trxProfiler->setRequestMethod( $request->getMethod() );
		if ( $request->hasSafeMethod() ) {
			$trxProfiler->setExpectations( $trxLimits['GET'], __METHOD__ );
		} else {
			$trxProfiler->setExpectations( $trxLimits['POST'], __METHOD__ );
		}

		if ( $this->maybeDoHttpsRedirect() ) {
			return;
		}

		$output = $this->context->getOutput();
		if ( $title->canExist() && HTMLFileCache::useFileCache( $this->context ) ) {
			// getAction() may trigger DB queries, so avoid eagerly initializing it if possible.
			// This reduces the cost of requests that exit early due to tryNormaliseRedirect()
			// or a MediaWikiPerformAction / BeforeInitialize hook handler.
			$action = $this->getAction();
			// Try low-level file cache hit
			$cache = new HTMLFileCache( $title, $action );
			if ( $cache->isCacheGood( /* Assume up to date */ ) ) {
				// Check incoming headers to see if client has this cached
				$timestamp = $cache->cacheTimestamp();
				if ( !$output->checkLastModified( $timestamp ) ) {
					$cache->loadFromFileCache( $this->context );
				}
				// Do any stats increment/watchlist stuff, assuming user is viewing the
				// latest revision (which should always be the case for file cache)
				$this->context->getWikiPage()->doViewUpdates( $this->context->getAuthority() );
				// Tell OutputPage that output is taken care of
				$output->disable();

				return;
			}
		}

		try {
			// Actually do the work of the request and build up any output
			$this->performRequest();
		} catch ( ErrorPageError $e ) {
			// TODO: Should ErrorPageError::report accept a OutputPage parameter?
			$e->report( ErrorPageError::STAGE_OUTPUT );
			$output->considerCacheSettingsFinal();
			// T64091: while exceptions are convenient to bubble up GUI errors,
			// they are not internal application faults. As with normal requests, this
			// should commit, print the output, do deferred updates, jobs, and profiling.
		}

		// Commit any changes in the current transaction round so that:
		// a) the transaction is not rolled back after success output was already sent
		// b) error output is not jumbled together with success output in the response
		$this->doPreOutputCommit();
		// If needed, push a deferred update to run jobs after the output is sent
		$this->schedulePostSendJobs();
		// Ask OutputPage/Skin to stage the output (HTTP response body and headers).
		// Flush the output to the client unless an exception occurred.
		$this->outputResponsePayload( $output->output( true ) );
	}

	/**
	 * Check if an HTTP->HTTPS redirect should be done. It may still be aborted
	 * by a hook, so this is not the final word.
	 *
	 * @return bool
	 */
	private function shouldDoHttpRedirect() {
		$request = $this->context->getRequest();

		// Don't redirect if we're already on HTTPS
		if ( $request->getProtocol() !== 'http' ) {
			return false;
		}

		$force = $this->config->get( MainConfigNames::ForceHTTPS );

		// Don't redirect if $wgServer is explicitly HTTP. We test for this here
		// by checking whether wfExpandUrl() is able to force HTTPS.
		if ( !preg_match( '#^https://#', wfExpandUrl( $request->getRequestURL(), PROTO_HTTPS ) ) ) {
			if ( $force ) {
				throw new RuntimeException( '$wgForceHTTPS is true but the server is not HTTPS' );
			}
			return false;
		}

		// Configured $wgForceHTTPS overrides the remaining conditions
		if ( $force ) {
			return true;
		}

		// Check if HTTPS is required by the session or user preferences
		return $request->getSession()->shouldForceHTTPS() ||
			// Check the cookie manually, for paranoia
			$request->getCookie( 'forceHTTPS', '' ) ||
			$this->context->getUser()->requiresHTTPS();
	}

	/**
	 * If the stars are suitably aligned, do an HTTP->HTTPS redirect
	 *
	 * Note: Do this after $wgTitle is setup, otherwise the hooks run from
	 * isRegistered() will do all sorts of weird stuff.
	 *
	 * @return bool True if the redirect was done. Handling of the request
	 *   should be aborted. False if no redirect was done.
	 */
	private function maybeDoHttpsRedirect() {
		if ( !$this->shouldDoHttpRedirect() ) {
			return false;
		}

		$request = $this->context->getRequest();
		$oldUrl = $request->getFullRequestURL();
		$redirUrl = preg_replace( '#^http://#', 'https://', $oldUrl );

		if ( $request->wasPosted() ) {
			// This is weird and we'd hope it almost never happens. This
			// means that a POST came in via HTTP and policy requires us
			// redirecting to HTTPS. It's likely such a request is going
			// to fail due to post data being lost, but let's try anyway
			// and just log the instance.

			// @todo FIXME: See if we could issue a 307 or 308 here, need
			// to see how clients (automated & browser) behave when we do
			wfDebugLog( 'RedirectedPosts', "Redirected from HTTP to HTTPS: $oldUrl" );
		}
		// Setup dummy Title, otherwise OutputPage::redirect will fail
		$title = Title::newFromText( 'REDIR', NS_MAIN );
		$this->context->setTitle( $title );
		// Since we only do this redir to change proto, always send a vary header
		$output = $this->context->getOutput();
		$output->addVaryHeader( 'X-Forwarded-Proto' );
		$output->redirect( $redirUrl );
		$output->output();

		return true;
	}

	/**
	 * Print a response body to the current buffer (if there is one) or the server (otherwise)
	 *
	 * This method should be called after doPreOutputCommit() and before doPostOutputShutdown()
	 *
	 * Any accompanying Content-Type header is assumed to have already been set
	 *
	 * @param string $content Response content, usually from OutputPage::output()
	 */
	private function outputResponsePayload( $content ) {
		// Append any visible profiling data in a manner appropriate for the Content-Type
		ob_start();
		try {
			Profiler::instance()->logDataPageOutputOnly();
		} finally {
			$content .= ob_get_clean();
		}

		// By default, usually one output buffer is active now, either the internal PHP buffer
		// started by "output_buffering" in php.ini or the buffer started by MW_SETUP_CALLBACK.
		// The MW_SETUP_CALLBACK buffer has an unlimited chunk size, while the internal PHP
		// buffer only has an unlimited chunk size if output_buffering="On". If the buffer was
		// filled up to the chunk size with printed data, then HTTP headers will have already
		// been sent. Also, if the entry point had to stream content to the client, then HTTP
		// headers will have already been sent as well, regardless of chunk size.

		// Disable mod_deflate compression since it interferes with the output buffer set
		// by MW_SETUP_CALLBACK and can also cause the client to wait on deferred updates
		if ( function_exists( 'apache_setenv' ) ) {
			// phpcs:ignore Generic.PHP.NoSilencedErrors.Discouraged
			@apache_setenv( 'no-gzip', '1' );
		}

		if (
			// "Content-Length" is used to prevent clients from waiting on deferred updates
			$this->postSendStrategy === self::DEFER_SET_LENGTH_AND_FLUSH &&
			// The HTTP response code clearly allows for a meaningful body
			in_array( http_response_code(), [ 200, 404 ], true ) &&
			// The queue of (post-send) deferred updates is non-empty
			DeferredUpdates::pendingUpdatesCount() &&
			// Any buffered output is not spread out across multiple output buffers
			ob_get_level() <= 1 &&
			// It is not too late to set additional HTTP headers
			!headers_sent()
		) {
			$response = $this->context->getRequest()->response();

			$obStatus = ob_get_status();
			if ( !isset( $obStatus['name'] ) ) {
				// No output buffer is active
				$response->header( 'Content-Length: ' . strlen( $content ) );
			} elseif ( $obStatus['name'] === 'default output handler' ) {
				// Internal PHP "output_buffering" output buffer (note that the internal PHP
				// "zlib.output_compression" output buffer is named "zlib output compression")
				$response->header( 'Content-Length: ' . ( ob_get_length() + strlen( $content ) ) );
			}

			// The MW_SETUP_CALLBACK output buffer ("MediaWiki\OutputHandler::handle") sets
			// "Content-Length" where applicable. Other output buffer types might not set this
			// header, and since they might mangle or compress the payload, it is not possible
			// to determine the final payload size here.

			// Tell the client to immediately end the connection as soon as the response payload
			// has been read (informed by any "Content-Length" header). This prevents the client
			// from waiting on deferred updates.
			// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Connection
			if ( ( $_SERVER['SERVER_PROTOCOL'] ?? '' ) === 'HTTP/1.1' ) {
				$response->header( 'Connection: close' );
			}
		}

		// Print the content *after* adjusting HTTP headers and disabling mod_deflate since
		// calling "print" will send the output to the client if there is no output buffer or
		// if the output buffer chunk size is reached
		print $content;
	}

	/**
	 * Ends this task peacefully
	 */
	public function restInPeace() {
		// Either all DB and deferred updates should happen or none.
		// The latter should not be cancelled due to client disconnect.
		ignore_user_abort( true );

		$services = MediaWikiServices::getInstance();
		$lbFactory = $services->getDBLoadBalancerFactory();
		// Assure deferred updates are not in the main transaction
		$lbFactory->commitPrimaryChanges( __METHOD__ );

		// Loosen DB query expectations since the HTTP client is unblocked
		$profiler = Profiler::instance();
		$trxProfiler = $profiler->getTransactionProfiler();
		$trxProfiler->redefineExpectations(
			$this->context->getRequest()->hasSafeMethod()
				? $this->config->get( MainConfigNames::TrxProfilerLimits )['PostSend-GET']
				: $this->config->get( MainConfigNames::TrxProfilerLimits )['PostSend-POST'],
			__METHOD__
		);

		// Do any deferred jobs; preferring to run them now if a client will not wait on them
		DeferredUpdates::doUpdates();

		// Handle external profiler outputs.
		// Any embedded profiler outputs were already processed in outputResponsePayload().
		$profiler->logData();

		self::emitBufferedStatsdData(
			$services->getStatsdDataFactory(),
			$this->config
		);

		// Send metrics gathered by StatsFactory
		$services->getStatsFactory()->flush();

		// Commit and close up!
		$lbFactory->commitPrimaryChanges( __METHOD__ );
		$lbFactory->shutdown( $lbFactory::SHUTDOWN_NO_CHRONPROT );

		wfDebug( "Request ended normally" );
	}

	/**
	 * Send out any buffered statsd data according to sampling rules
	 *
	 * For web requests, this is called once by MediaWiki::restInPeace(),
	 * which is post-send (after the response is sent to the client).
	 *
	 * For maintenance scripts, especially long-running CLI scripts, it is called
	 * more often, to avoid OOM, since we buffer stats (T181385), based on the
	 * following heuristics:
	 *
	 * - Long-running scripts that involve database writes often use transactions
	 *   to commit chunks of work. We flush from IDatabase::setTransactionListener,
	 *   as wired up by MWLBFactory::applyGlobalState.
	 *
	 * - Long-running scripts that involve database writes but don't need any
	 *   transactions will still periodically wait for replication to be
	 *   graceful to the databases. We flush from ILBFactory::setWaitForReplicationListener
	 *   as wired up by MWLBFactory::applyGlobalState.
	 *
	 * - Any other long-running scripts will probably report progress to stdout
	 *   in some way. We also flush from Maintenance::output().
	 *
	 * @param IBufferingStatsdDataFactory $stats
	 * @param Config $config
	 * @throws ConfigException
	 * @since 1.31
	 */
	public static function emitBufferedStatsdData(
		IBufferingStatsdDataFactory $stats, Config $config
	) {
		if ( $config->get( MainConfigNames::StatsdServer ) && $stats->hasData() ) {
			try {
				$statsdServer = explode( ':', $config->get( MainConfigNames::StatsdServer ), 2 );
				$statsdHost = $statsdServer[0];
				$statsdPort = $statsdServer[1] ?? 8125;
				$statsdSender = new SocketSender( $statsdHost, $statsdPort );
				$statsdClient = new SamplingStatsdClient( $statsdSender, true, false );
				$statsdClient->setSamplingRates( $config->get( MainConfigNames::StatsdSamplingRates ) );
				$statsdClient->send( $stats->getData() );
			} catch ( Exception $e ) {
				MWExceptionHandler::logException( $e, MWExceptionHandler::CAUGHT_BY_ENTRYPOINT );
			}
		}
		// empty buffer for the next round
		$stats->clearData();
	}

	/**
	 * @param int $n Number of jobs to try to run
	 */
	private function triggerSyncJobs( $n ) {
		$scope = Profiler::instance()->getTransactionProfiler()->silenceForScope();
		$runner = MediaWikiServices::getInstance()->getJobRunner();
		$runner->run( [ 'maxJobs' => $n ] );
		ScopedCallback::consume( $scope );
	}

	/**
	 * @param int $n Number of jobs to try to run
	 * @param LoggerInterface $runJobsLogger
	 * @return bool Success
	 */
	private function triggerAsyncJobs( $n, LoggerInterface $runJobsLogger ) {
		$services = MediaWikiServices::getInstance();
		// Do not send request if there are probably no jobs
		$group = $services->getJobQueueGroupFactory()->makeJobQueueGroup();
		if ( !$group->queuesHaveJobs( JobQueueGroup::TYPE_DEFAULT ) ) {
			return true;
		}

		$query = [ 'title' => 'Special:RunJobs',
			'tasks' => 'jobs', 'maxjobs' => $n, 'sigexpiry' => time() + 5 ];
		$query['signature'] = SpecialRunJobs::getQuerySignature(
			$query, $this->config->get( MainConfigNames::SecretKey ) );

		$errno = $errstr = null;
		$info = wfParseUrl( $this->config->get( MainConfigNames::CanonicalServer ) );
		$host = $info ? $info['host'] : null;
		$port = 80;
		if ( isset( $info['scheme'] ) && $info['scheme'] == 'https' ) {
			$host = "tls://" . $host;
			$port = 443;
		}
		if ( isset( $info['port'] ) ) {
			$port = $info['port'];
		}

		AtEase::suppressWarnings();
		$sock = $host ? fsockopen(
			$host,
			$port,
			$errno,
			$errstr,
			// If it takes more than 100ms to connect to ourselves there is a problem...
			0.100
		) : false;
		AtEase::restoreWarnings();

		$invokedWithSuccess = true;
		if ( $sock ) {
			$special = $services->getSpecialPageFactory()->getPage( 'RunJobs' );
			$url = $special->getPageTitle()->getCanonicalURL( $query );
			$req = (
				"POST $url HTTP/1.1\r\n" .
				"Host: {$info['host']}\r\n" .
				"Connection: Close\r\n" .
				"Content-Length: 0\r\n\r\n"
			);

			$runJobsLogger->info( "Running $n job(s) via '$url'" );
			// Send a cron API request to be performed in the background.
			// Give up if this takes too long to send (which should be rare).
			stream_set_timeout( $sock, 2 );
			$bytes = fwrite( $sock, $req );
			if ( $bytes !== strlen( $req ) ) {
				$invokedWithSuccess = false;
				$runJobsLogger->error( "Failed to start cron API (socket write error)" );
			} else {
				// Do not wait for the response (the script should handle client aborts).
				// Make sure that we don't close before that script reaches ignore_user_abort().
				$start = microtime( true );
				$status = fgets( $sock );
				$sec = microtime( true ) - $start;
				if ( !preg_match( '#^HTTP/\d\.\d 202 #', $status ) ) {
					$invokedWithSuccess = false;
					$runJobsLogger->error( "Failed to start cron API: received '$status' ($sec)" );
				}
			}
			fclose( $sock );
		} else {
			$invokedWithSuccess = false;
			$runJobsLogger->error( "Failed to start cron API (socket error $errno): $errstr" );
		}

		return $invokedWithSuccess;
	}
}
