ApiStashEdit.php

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<?php
use MediaWiki\Logger\LoggerFactory;

class ApiStashEdit extends ApiBase {
    const ERROR_NONE = 'stashed';
    const ERROR_PARSE = 'error_parse';
    const ERROR_CACHE = 'error_cache';
    const ERROR_UNCACHEABLE = 'uncacheable';

    const PRESUME_FRESH_TTL_SEC = 5;

    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(), [ '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(), [ 'status' => $status ] );
    }

    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', [ $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;
    }

    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;
    }

    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.no_stash' );
            $logger->debug( "No cache value for key '$key'." );
            return false;
        }

        $age = time() - wfTimestamp( TS_UNIX, $editInfo->output->getCacheTime() );
        if ( $age <= self::PRESUME_FRESH_TTL_SEC ) {
            $stats->increment( 'editstash.cache_hits.presumed_fresh' );
            $logger->debug( "Timestamp-based cache hit for key '$key' (age: $age sec)." );
            return $editInfo; // assume nothing changed
        }

        $dbr = wfGetDB( DB_SLAVE );

        $templates = []; // 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',
                [ '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.proven_stale' );
                $logger->info( "Stale cache for key '$key'; template changed. (age: $age sec)" );
                return false;
            }
        }

        $files = []; // 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',
                [ 'name' => 'img_name', 'img_sha1' ],
                [ '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.proven_stale' );
                $logger->info( "Stale cache for key '$key'; file changed. (age: $age sec)" );
                return false;
            }
        }

        $stats->increment( 'editstash.cache_hits.proven_fresh' );
        $logger->debug( "Verified cache hit for key '$key' (age: $age sec)." );

        return $editInfo;
    }

    protected static function getStashKey( Title $title, Content $content, User $user ) {
        $hash = sha1( implode( ':', [
            $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 );
    }

    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)[
                'pstContent' => $pstContent,
                'output'     => $parserOutput,
                'timestamp'  => $timestamp
            ];
            return [ $stashInfo, $ttl ];
        }

        return [ null, 0 ];
    }

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

    public function needsToken() {
        return 'csrf';
    }

    public function mustBePosted() {
        return true;
    }

    public function isWriteMode() {
        return true;
    }

    public function isInternal() {
        return true;
    }
}