PHPSessionHandler: Implement SessionHandlerInterface

[mediawiki.git] / includes / api / ApiStashEdit.php

<?php
/**
 * 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
 * @author Aaron Schulz
 */

use MediaWiki\Logger\LoggerFactory;

/**
 * Prepare an edit in shared cache so that it can be reused on edit
 *
 * This endpoint can be called via AJAX as the user focuses on the edit
 * summary box. By the time of submission, the parse may have already
 * finished, and can be immediately used on page save. Certain parser
 * functions like {{REVISIONID}} or {{CURRENTTIME}} may cause the cache
 * to not be used on edit. Template and files used are check for changes
 * since the output was generated. The cache TTL is also kept low for sanity.
 *
 * @ingroup API
 * @since 1.25
 */
class ApiStashEdit extends ApiBase {
        const ERROR_NONE = 'stashed';
        const ERROR_PARSE = 'error_parse';
        const ERROR_CACHE = 'error_cache';
        const ERROR_UNCACHEABLE = 'uncacheable';

        public function execute() {
                $user = $this->getUser();
                $params = $this->extractRequestParams();

                $page = $this->getTitleOrPageId( $params );
                $title = $page->getTitle();

                if ( !ContentHandler::getForModelID( $params['contentmodel'] )
                        ->isSupportedFormat( $params['contentformat'] )
                ) {
                        $this->dieUsage( "Unsupported content model/format", 'badmodelformat' );
                }

                // Trim and fix newlines so the key SHA1's match (see RequestContext::getText())
                $text = rtrim( str_replace( "\r\n", "\n", $params['text'] ) );
                $textContent = ContentHandler::makeContent(
                        $text, $title, $params['contentmodel'], $params['contentformat'] );

                $page = WikiPage::factory( $title );
                if ( $page->exists() ) {
                        // Page exists: get the merged content with the proposed change
                        $baseRev = Revision::newFromPageId( $page->getId(), $params['baserevid'] );
                        if ( !$baseRev ) {
                                $this->dieUsage( "No revision ID {$params['baserevid']}", 'missingrev' );
                        }
                        $currentRev = $page->getRevision();
                        if ( !$currentRev ) {
                                $this->dieUsage( "No current revision of page ID {$page->getId()}", 'missingrev' );
                        }
                        // Merge in the new version of the section to get the proposed version
                        $editContent = $page->replaceSectionAtRev(
                                $params['section'],
                                $textContent,
                                $params['sectiontitle'],
                                $baseRev->getId()
                        );
                        if ( !$editContent ) {
                                $this->dieUsage( "Could not merge updated section.", 'replacefailed' );
                        }
                        if ( $currentRev->getId() == $baseRev->getId() ) {
                                // Base revision was still the latest; nothing to merge
                                $content = $editContent;
                        } else {
                                // Merge the edit into the current version
                                $baseContent = $baseRev->getContent();
                                $currentContent = $currentRev->getContent();
                                if ( !$baseContent || !$currentContent ) {
                                        $this->dieUsage( "Missing content for page ID {$page->getId()}", 'missingrev' );
                                }
                                $handler = ContentHandler::getForModelID( $baseContent->getModel() );
                                $content = $handler->merge3( $baseContent, $editContent, $currentContent );
                        }
                } else {
                        // New pages: use the user-provided content model
                        $content = $textContent;
                }

                if ( !$content ) { // merge3() failed
                        $this->getResult()->addValue( null,
                                $this->getModuleName(), array( 'status' => 'editconflict' ) );
                        return;
                }

                // The user will abort the AJAX request by pressing "save", so ignore that
                ignore_user_abort( true );

                // Use the master DB for fast blocking locks
                $dbw = wfGetDB( DB_MASTER );

                // Get a key based on the source text, format, and user preferences
                $key = self::getStashKey( $title, $content, $user );
                // De-duplicate requests on the same key
                if ( $user->pingLimiter( 'stashedit' ) ) {
                        $status = 'ratelimited';
                } elseif ( $dbw->lock( $key, __METHOD__, 1 ) ) {
                        $status = self::parseAndStash( $page, $content, $user );
                        $dbw->unlock( $key, __METHOD__ );
                } else {
                        $status = 'busy';
                }

                $this->getResult()->addValue( null, $this->getModuleName(), array( 'status' => $status ) );
        }

        /**
         * @param WikiPage $page
         * @param Content $content
         * @param User $user
         * @return integer ApiStashEdit::ERROR_* constant
         * @since 1.25
         */
        public static function parseAndStash( WikiPage $page, Content $content, User $user ) {
                $cache = ObjectCache::getLocalClusterInstance();
                $logger = LoggerFactory::getInstance( 'StashEdit' );

                $format = $content->getDefaultFormat();
                $editInfo = $page->prepareContentForEdit( $content, null, $user, $format, false );

                if ( $editInfo && $editInfo->output ) {
                        $key = self::getStashKey( $page->getTitle(), $content, $user );

                        // Let extensions add ParserOutput metadata or warm other caches
                        Hooks::run( 'ParserOutputStashForEdit', array( $page, $content, $editInfo->output ) );

                        list( $stashInfo, $ttl ) = self::buildStashValue(
                                $editInfo->pstContent, $editInfo->output, $editInfo->timestamp
                        );

                        if ( $stashInfo ) {
                                $ok = $cache->set( $key, $stashInfo, $ttl );
                                if ( $ok ) {

                                        $logger->debug( "Cached parser output for key '$key'." );
                                        return self::ERROR_NONE;
                                } else {
                                        $logger->error( "Failed to cache parser output for key '$key'." );
                                        return self::ERROR_CACHE;
                                }
                        } else {
                                $logger->info( "Uncacheable parser output for key '$key'." );
                                return self::ERROR_UNCACHEABLE;
                        }
                }

                return self::ERROR_PARSE;
        }

        /**
         * Attempt to cache PST content and corresponding parser output in passing
         *
         * This method can be called when the output was already generated for other
         * reasons. Parsing should not be done just to call this method, however.
         * $pstOpts must be that of the user doing the edit preview. If $pOpts does
         * not match the options of WikiPage::makeParserOptions( 'canonical' ), this
         * will do nothing. Provided the values are cacheable, they will be stored
         * in memcached so that final edit submission might make use of them.
         *
         * @param Page|Article|WikiPage $page Page title
         * @param Content $content Proposed page content
         * @param Content $pstContent The result of preSaveTransform() on $content
         * @param ParserOutput $pOut The result of getParserOutput() on $pstContent
         * @param ParserOptions $pstOpts Options for $pstContent (MUST be for prospective author)
         * @param ParserOptions $pOpts Options for $pOut
         * @param string $timestamp TS_MW timestamp of parser output generation
         * @return bool Success
         */
        public static function stashEditFromPreview(
                Page $page, Content $content, Content $pstContent, ParserOutput $pOut,
                ParserOptions $pstOpts, ParserOptions $pOpts, $timestamp
        ) {
                $cache = ObjectCache::getLocalClusterInstance();
                $logger = LoggerFactory::getInstance( 'StashEdit' );

                // getIsPreview() controls parser function behavior that references things
                // like user/revision that don't exists yet. The user/text should already
                // be set correctly by callers, just double check the preview flag.
                if ( !$pOpts->getIsPreview() ) {
                        return false; // sanity
                } elseif ( $pOpts->getIsSectionPreview() ) {
                        return false; // short-circuit (need the full content)
                }

                // PST parser options are for the user (handles signatures, etc...)
                $user = $pstOpts->getUser();
                // Get a key based on the source text, format, and user preferences
                $key = self::getStashKey( $page->getTitle(), $content, $user );

                // Parser output options must match cannonical options.
                // Treat some options as matching that are different but don't matter.
                $canonicalPOpts = $page->makeParserOptions( 'canonical' );
                $canonicalPOpts->setIsPreview( true ); // force match
                $canonicalPOpts->setTimestamp( $pOpts->getTimestamp() ); // force match
                if ( !$pOpts->matches( $canonicalPOpts ) ) {
                        $logger->info( "Uncacheable preview output for key '$key' (options)." );
                        return false;
                }

                // Build a value to cache with a proper TTL
                list( $stashInfo, $ttl ) = self::buildStashValue( $pstContent, $pOut, $timestamp );
                if ( !$stashInfo ) {
                        $logger->info( "Uncacheable parser output for key '$key' (rev/TTL)." );
                        return false;
                }

                $ok = $cache->set( $key, $stashInfo, $ttl );
                if ( !$ok ) {
                        $logger->error( "Failed to cache preview parser output for key '$key'." );
                } else {
                        $logger->debug( "Cached preview output for key '$key'." );
                }

                return $ok;
        }

        /**
         * Check that a prepared edit is in cache and still up-to-date
         *
         * This method blocks if the prepared edit is already being rendered,
         * waiting until rendering finishes before doing final validity checks.
         *
         * The cache is rejected if template or file changes are detected.
         * Note that foreign template or file transclusions are not checked.
         *
         * The result is a map (pstContent,output,timestamp) with fields
         * extracted directly from WikiPage::prepareContentForEdit().
         *
         * @param Title $title
         * @param Content $content
         * @param User $user User to get parser options from
         * @return stdClass|bool Returns false on cache miss
         */
        public static function checkCache( Title $title, Content $content, User $user ) {
                $cache = ObjectCache::getLocalClusterInstance();
                $logger = LoggerFactory::getInstance( 'StashEdit' );
                $stats = RequestContext::getMain()->getStats();

                $key = self::getStashKey( $title, $content, $user );
                $editInfo = $cache->get( $key );
                if ( !is_object( $editInfo ) ) {
                        $start = microtime( true );
                        // We ignore user aborts and keep parsing. Block on any prior parsing
                        // so as to use its results and make use of the time spent parsing.
                        // Skip this logic if there no master connection in case this method
                        // is called on an HTTP GET request for some reason.
                        $lb = wfGetLB();
                        $dbw = $lb->getAnyOpenConnection( $lb->getWriterIndex() );
                        if ( $dbw && $dbw->lock( $key, __METHOD__, 30 ) ) {
                                $editInfo = $cache->get( $key );
                                $dbw->unlock( $key, __METHOD__ );
                        }

                        $timeMs = 1000 * max( 0, microtime( true ) - $start );
                        $stats->timing( 'editstash.lock-wait-time', $timeMs );
                }

                if ( !is_object( $editInfo ) || !$editInfo->output ) {
                        $stats->increment( 'editstash.cache-misses' );
                        $logger->debug( "No cache value for key '$key'." );
                        return false;
                }

                $time = wfTimestamp( TS_UNIX, $editInfo->output->getTimestamp() );
                if ( ( time() - $time ) <= 3 ) {
                        $stats->increment( 'editstash.cache-hits' );
                        $logger->debug( "Timestamp-based cache hit for key '$key'." );
                        return $editInfo; // assume nothing changed
                }

                $dbr = wfGetDB( DB_SLAVE );

                $templates = array(); // conditions to find changes/creations
                $templateUses = 0; // expected existing templates
                foreach ( $editInfo->output->getTemplateIds() as $ns => $stuff ) {
                        foreach ( $stuff as $dbkey => $revId ) {
                                $templates[(string)$ns][$dbkey] = (int)$revId;
                                ++$templateUses;
                        }
                }
                // Check that no templates used in the output changed...
                if ( count( $templates ) ) {
                        $res = $dbr->select(
                                'page',
                                array( 'ns' => 'page_namespace', 'dbk' => 'page_title', 'page_latest' ),
                                $dbr->makeWhereFrom2d( $templates, 'page_namespace', 'page_title' ),
                                __METHOD__
                        );
                        $changed = false;
                        foreach ( $res as $row ) {
                                $changed = $changed || ( $row->page_latest != $templates[$row->ns][$row->dbk] );
                        }

                        if ( $changed || $res->numRows() != $templateUses ) {
                                $stats->increment( 'editstash.cache-misses' );
                                $logger->info( "Stale cache for key '$key'; template changed." );
                                return false;
                        }
                }

                $files = array(); // conditions to find changes/creations
                foreach ( $editInfo->output->getFileSearchOptions() as $name => $options ) {
                        $files[$name] = (string)$options['sha1'];
                }
                // Check that no files used in the output changed...
                if ( count( $files ) ) {
                        $res = $dbr->select(
                                'image',
                                array( 'name' => 'img_name', 'img_sha1' ),
                                array( 'img_name' => array_keys( $files ) ),
                                __METHOD__
                        );
                        $changed = false;
                        foreach ( $res as $row ) {
                                $changed = $changed || ( $row->img_sha1 != $files[$row->name] );
                        }

                        if ( $changed || $res->numRows() != count( $files ) ) {
                                $stats->increment( 'editstash.cache-misses' );
                                $logger->info( "Stale cache for key '$key'; file changed." );
                                return false;
                        }
                }

                $stats->increment( 'editstash.cache-hits' );
                $logger->debug( "Cache hit for key '$key'." );

                return $editInfo;
        }

        /**
         * Get the temporary prepared edit stash key for a user
         *
         * This key can be used for caching prepared edits provided:
         *   - a) The $user was used for PST options
         *   - b) The parser output was made from the PST using cannonical matching options
         *
         * @param Title $title
         * @param Content $content
         * @param User $user User to get parser options from
         * @return string
         */
        protected static function getStashKey( Title $title, Content $content, User $user ) {
                $hash = sha1( implode( ':', array(
                        $content->getModel(),
                        $content->getDefaultFormat(),
                        sha1( $content->serialize( $content->getDefaultFormat() ) ),
                        $user->getId() ?: md5( $user->getName() ), // account for user parser options
                        $user->getId() ? $user->getDBTouched() : '-' // handle preference change races
                ) ) );

                return wfMemcKey( 'prepared-edit', md5( $title->getPrefixedDBkey() ), $hash );
        }

        /**
         * Build a value to store in memcached based on the PST content and parser output
         *
         * This makes a simple version of WikiPage::prepareContentForEdit() as stash info
         *
         * @param Content $pstContent
         * @param ParserOutput $parserOutput
         * @param string $timestamp TS_MW
         * @return array (stash info array, TTL in seconds) or (null, 0)
         */
        protected static function buildStashValue(
                Content $pstContent, ParserOutput $parserOutput, $timestamp
        ) {
                // If an item is renewed, mind the cache TTL determined by config and parser functions
                $since = time() - wfTimestamp( TS_UNIX, $parserOutput->getTimestamp() );
                $ttl = min( $parserOutput->getCacheExpiry() - $since, 5 * 60 );

                if ( $ttl > 0 && !$parserOutput->getFlag( 'vary-revision' ) ) {
                        // Only store what is actually needed
                        $stashInfo = (object)array(
                                'pstContent' => $pstContent,
                                'output'     => $parserOutput,
                                'timestamp'  => $timestamp
                        );
                        return array( $stashInfo, $ttl );
                }

                return array( null, 0 );
        }

        public function getAllowedParams() {
                return array(
                        'title' => array(
                                ApiBase::PARAM_TYPE => 'string',
                                ApiBase::PARAM_REQUIRED => true
                        ),
                        'section' => array(
                                ApiBase::PARAM_TYPE => 'string',
                        ),
                        'sectiontitle' => array(
                                ApiBase::PARAM_TYPE => 'string'
                        ),
                        'text' => array(
                                ApiBase::PARAM_TYPE => 'text',
                                ApiBase::PARAM_REQUIRED => true
                        ),
                        'contentmodel' => array(
                                ApiBase::PARAM_TYPE => ContentHandler::getContentModels(),
                                ApiBase::PARAM_REQUIRED => true
                        ),
                        'contentformat' => array(
                                ApiBase::PARAM_TYPE => ContentHandler::getAllContentFormats(),
                                ApiBase::PARAM_REQUIRED => true
                        ),
                        'baserevid' => array(
                                ApiBase::PARAM_TYPE => 'integer',
                                ApiBase::PARAM_REQUIRED => true
                        )
                );
        }

        function needsToken() {
                return 'csrf';
        }

        function mustBePosted() {
                return true;
        }

        function isWriteMode() {
                return true;
        }

        function isInternal() {
                return true;
        }
}