ApiQueryRevisionsBase.php

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<?php
use MediaWiki\CommentFormatter\CommentFormatter;
use MediaWiki\Content\IContentHandlerFactory;
use MediaWiki\Content\Renderer\ContentRenderer;
use MediaWiki\Content\Transform\ContentTransformer;
use MediaWiki\Content\WikitextContent;
use MediaWiki\Context\DerivativeContext;
use MediaWiki\Logger\LoggerFactory;
use MediaWiki\MainConfigNames;
use MediaWiki\MediaWikiServices;
use MediaWiki\Parser\Parser;
use MediaWiki\Revision\RevisionAccessException;
use MediaWiki\Revision\RevisionRecord;
use MediaWiki\Revision\RevisionStore;
use MediaWiki\Revision\SlotRecord;
use MediaWiki\Revision\SlotRoleRegistry;
use MediaWiki\Title\Title;
use MediaWiki\User\TempUser\TempUserCreator;
use MediaWiki\User\UserFactory;
use MediaWiki\User\UserNameUtils;
use Wikimedia\ParamValidator\ParamValidator;
use Wikimedia\ParamValidator\TypeDef\EnumDef;
use Wikimedia\ParamValidator\TypeDef\IntegerDef;
 
abstract class ApiQueryRevisionsBase extends ApiQueryGeneratorBase {
 
    // region Constants for internal use. Don't use externally.
    // Bits to indicate the results of the revdel permission check on a revision,
    // see self::checkRevDel()
    private const IS_DELETED = 1; // Whether the field is revision-deleted
    private const CANNOT_VIEW = 2; // Whether the user cannot view the field due to revdel
 
    private const LIMIT_PARSE = 1;
 
    // endregion
 
    protected $limit;
    protected $diffto;
    protected $difftotext;
    protected $difftotextpst;
    protected $expandTemplates;
    protected $generateXML;
    protected $section;
    protected $parseContent;
    protected $fetchContent;
    protected $contentFormat;
    protected bool $setParsedLimit = true;
    protected ?array $slotRoles = null;
    protected $slotContentFormats;
    protected $needSlots;
 
    protected bool $fld_ids = false;
    protected bool $fld_flags = false;
    protected bool $fld_timestamp = false;
    protected bool $fld_size = false;
    protected bool $fld_slotsize = false;
    protected bool $fld_sha1 = false;
    protected bool $fld_slotsha1 = false;
    protected bool $fld_comment = false;
    protected bool $fld_parsedcomment = false;
    protected bool $fld_user = false;
    protected bool $fld_userid = false;
    protected bool $fld_content = false;
    protected bool $fld_tags = false;
    protected bool $fld_contentmodel = false;
    protected bool $fld_roles = false;
    protected bool $fld_parsetree = false;
 
    private $numUncachedDiffs = 0;
 
    private RevisionStore $revisionStore;
    private IContentHandlerFactory $contentHandlerFactory;
    private ParserFactory $parserFactory;
    private SlotRoleRegistry $slotRoleRegistry;
    private ContentRenderer $contentRenderer;
    private ContentTransformer $contentTransformer;
    private CommentFormatter $commentFormatter;
    private TempUserCreator $tempUserCreator;
    private UserFactory $userFactory;
    private UserNameUtils $userNameUtils;
 
    public function __construct(
        ApiQuery $queryModule,
        $moduleName,
        $paramPrefix = '',
        RevisionStore $revisionStore = null,
        IContentHandlerFactory $contentHandlerFactory = null,
        ParserFactory $parserFactory = null,
        SlotRoleRegistry $slotRoleRegistry = null,
        ContentRenderer $contentRenderer = null,
        ContentTransformer $contentTransformer = null,
        CommentFormatter $commentFormatter = null,
        TempUserCreator $tempUserCreator = null,
        UserFactory $userFactory = null,
        UserNameUtils $userNameUtils = null
    ) {
        parent::__construct( $queryModule, $moduleName, $paramPrefix );
        // This class is part of the stable interface and
        // therefor fallback to global state, if services are not provided
        $services = MediaWikiServices::getInstance();
        $this->revisionStore = $revisionStore ?? $services->getRevisionStore();
        $this->contentHandlerFactory = $contentHandlerFactory ?? $services->getContentHandlerFactory();
        $this->parserFactory = $parserFactory ?? $services->getParserFactory();
        $this->slotRoleRegistry = $slotRoleRegistry ?? $services->getSlotRoleRegistry();
        $this->contentRenderer = $contentRenderer ?? $services->getContentRenderer();
        $this->contentTransformer = $contentTransformer ?? $services->getContentTransformer();
        $this->commentFormatter = $commentFormatter ?? $services->getCommentFormatter();
        $this->tempUserCreator = $tempUserCreator ?? $services->getTempUserCreator();
        $this->userFactory = $userFactory ?? $services->getUserFactory();
        $this->userNameUtils = $userNameUtils ?? $services->getUserNameUtils();
    }
 
    public function execute() {
        $this->run();
    }
 
    public function executeGenerator( $resultPageSet ) {
        $this->run( $resultPageSet );
    }
 
    abstract protected function run( ApiPageSet $resultPageSet = null );
 
    protected function parseParameters( $params ) {
        $prop = array_fill_keys( $params['prop'], true );
 
        $this->fld_ids = isset( $prop['ids'] );
        $this->fld_flags = isset( $prop['flags'] );
        $this->fld_timestamp = isset( $prop['timestamp'] );
        $this->fld_comment = isset( $prop['comment'] );
        $this->fld_parsedcomment = isset( $prop['parsedcomment'] );
        $this->fld_size = isset( $prop['size'] );
        $this->fld_slotsize = isset( $prop['slotsize'] );
        $this->fld_sha1 = isset( $prop['sha1'] );
        $this->fld_slotsha1 = isset( $prop['slotsha1'] );
        $this->fld_content = isset( $prop['content'] );
        $this->fld_contentmodel = isset( $prop['contentmodel'] );
        $this->fld_userid = isset( $prop['userid'] );
        $this->fld_user = isset( $prop['user'] );
        $this->fld_tags = isset( $prop['tags'] );
        $this->fld_roles = isset( $prop['roles'] );
        $this->fld_parsetree = isset( $prop['parsetree'] );
 
        $this->slotRoles = $params['slots'];
 
        if ( $this->slotRoles !== null ) {
            if ( $this->fld_parsetree ) {
                $this->dieWithError( [
                    'apierror-invalidparammix-cannotusewith',
                    $this->encodeParamName( 'prop=parsetree' ),
                    $this->encodeParamName( 'slots' ),
                ], 'invalidparammix' );
            }
            foreach ( [
                'expandtemplates', 'generatexml', 'parse', 'diffto', 'difftotext', 'difftotextpst',
                'contentformat'
            ] as $p ) {
                if ( $params[$p] !== null && $params[$p] !== false ) {
                    $this->dieWithError( [
                        'apierror-invalidparammix-cannotusewith',
                        $this->encodeParamName( $p ),
                        $this->encodeParamName( 'slots' ),
                    ], 'invalidparammix' );
                }
            }
            $this->slotContentFormats = [];
            foreach ( $this->slotRoles as $slotRole ) {
                if ( isset( $params['contentformat-' . $slotRole] ) ) {
                    $this->slotContentFormats[$slotRole] = $params['contentformat-' . $slotRole];
                }
            }
        }
 
        if ( !empty( $params['contentformat'] ) ) {
            $this->contentFormat = $params['contentformat'];
        }
 
        $this->limit = $params['limit'];
 
        if ( $params['difftotext'] !== null ) {
            $this->difftotext = $params['difftotext'];
            $this->difftotextpst = $params['difftotextpst'];
        } elseif ( $params['diffto'] !== null ) {
            if ( $params['diffto'] == 'cur' ) {
                $params['diffto'] = 0;
            }
            if ( ( !ctype_digit( $params['diffto'] ) || $params['diffto'] < 0 )
                && $params['diffto'] != 'prev' && $params['diffto'] != 'next'
            ) {
                $p = $this->getModulePrefix();
                $this->dieWithError( [ 'apierror-baddiffto', $p ], 'diffto' );
            }
            // Check whether the revision exists and is readable,
            // DifferenceEngine returns a rather ambiguous empty
            // string if that's not the case
            if ( is_numeric( $params['diffto'] ) && $params['diffto'] != 0 ) {
                $difftoRev = $this->revisionStore->getRevisionById( $params['diffto'] );
                if ( !$difftoRev ) {
                    $this->dieWithError( [ 'apierror-nosuchrevid', $params['diffto'] ] );
                }
                // @phan-suppress-next-line PhanTypeMismatchArgumentNullable T240141
                $revDel = $this->checkRevDel( $difftoRev, RevisionRecord::DELETED_TEXT );
                if ( $revDel & self::CANNOT_VIEW ) {
                    $this->addWarning( [ 'apiwarn-difftohidden', $difftoRev->getId() ] );
                    $params['diffto'] = null;
                }
            }
            $this->diffto = $params['diffto'];
        }
 
        $this->fetchContent = $this->fld_content || $this->diffto !== null
            || $this->difftotext !== null || $this->fld_parsetree;
 
        $smallLimit = false;
        if ( $this->fetchContent ) {
            $smallLimit = true;
            $this->expandTemplates = $params['expandtemplates'];
            $this->generateXML = $params['generatexml'];
            $this->parseContent = $params['parse'];
            if ( $this->parseContent ) {
                // Must manually initialize unset limit
                $this->limit ??= self::LIMIT_PARSE;
            }
            $this->section = $params['section'] ?? false;
        }
 
        $userMax = $this->parseContent ? self::LIMIT_PARSE :
            ( $smallLimit ? ApiBase::LIMIT_SML1 : ApiBase::LIMIT_BIG1 );
        $botMax = $this->parseContent ? self::LIMIT_PARSE :
            ( $smallLimit ? ApiBase::LIMIT_SML2 : ApiBase::LIMIT_BIG2 );
        if ( $this->limit == 'max' ) {
            $this->limit = $this->getMain()->canApiHighLimits() ? $botMax : $userMax;
            if ( $this->setParsedLimit ) {
                $this->getResult()->addParsedLimit( $this->getModuleName(), $this->limit );
            }
        }
 
        $this->limit = $this->getMain()->getParamValidator()->validateValue(
            $this, 'limit', $this->limit ?? 10, [
                ParamValidator::PARAM_TYPE => 'limit',
                IntegerDef::PARAM_MIN => 1,
                IntegerDef::PARAM_MAX => $userMax,
                IntegerDef::PARAM_MAX2 => $botMax,
                IntegerDef::PARAM_IGNORE_RANGE => true,
            ]
        );
 
        $this->needSlots = $this->fetchContent || $this->fld_contentmodel ||
            $this->fld_slotsize || $this->fld_slotsha1;
        if ( $this->needSlots && $this->slotRoles === null ) {
            $encParam = $this->encodeParamName( 'slots' );
            $name = $this->getModuleName();
            $parent = $this->getParent();
            $parentParam = $parent->encodeParamName( $parent->getModuleManager()->getModuleGroup( $name ) );
            $this->addDeprecation(
                [ 'apiwarn-deprecation-missingparam', $encParam ],
                "action=query&{$parentParam}={$name}&!{$encParam}"
            );
        }
    }
 
    private function checkRevDel( RevisionRecord $revision, $field ) {
        $ret = $revision->isDeleted( $field ) ? self::IS_DELETED : 0;
        if ( $ret ) {
            $canSee = $revision->userCan( $field, $this->getAuthority() );
            $ret |= ( $canSee ? 0 : self::CANNOT_VIEW );
        }
        return $ret;
    }
 
    protected function extractRevisionInfo( RevisionRecord $revision, $row ) {
        $vals = [];
        $anyHidden = false;
 
        if ( $this->fld_ids ) {
            $vals['revid'] = (int)$revision->getId();
            if ( $revision->getParentId() !== null ) {
                $vals['parentid'] = (int)$revision->getParentId();
            }
        }
 
        if ( $this->fld_flags ) {
            $vals['minor'] = $revision->isMinor();
        }
 
        if ( $this->fld_user || $this->fld_userid ) {
            $revDel = $this->checkRevDel( $revision, RevisionRecord::DELETED_USER );
            if ( $revDel & self::IS_DELETED ) {
                $vals['userhidden'] = true;
                $anyHidden = true;
            }
            if ( !( $revDel & self::CANNOT_VIEW ) ) {
                $u = $revision->getUser( RevisionRecord::RAW );
                if ( $this->fld_user ) {
                    $vals['user'] = $u->getName();
                }
                if ( $this->userNameUtils->isTemp( $u->getName() ) ) {
                    $vals['temp'] = true;
                }
                if ( !$u->isRegistered() ) {
                    $vals['anon'] = true;
                }
 
                if ( $this->fld_userid ) {
                    $vals['userid'] = $u->getId();
                }
            }
        }
 
        if ( $this->fld_timestamp ) {
            $vals['timestamp'] = wfTimestamp( TS_ISO_8601, $revision->getTimestamp() );
        }
 
        if ( $this->fld_size ) {
            try {
                $vals['size'] = (int)$revision->getSize();
            } catch ( RevisionAccessException $e ) {
                // Back compat: If there's no size, return 0.
                // @todo: Gergő says to mention T198099 as a "todo" here.
                $vals['size'] = 0;
            }
        }
 
        if ( $this->fld_sha1 ) {
            $revDel = $this->checkRevDel( $revision, RevisionRecord::DELETED_TEXT );
            if ( $revDel & self::IS_DELETED ) {
                $vals['sha1hidden'] = true;
                $anyHidden = true;
            }
            if ( !( $revDel & self::CANNOT_VIEW ) ) {
                try {
                    $vals['sha1'] = Wikimedia\base_convert( $revision->getSha1(), 36, 16, 40 );
                } catch ( RevisionAccessException $e ) {
                    // Back compat: If there's no sha1, return empty string.
                    // @todo: Gergő says to mention T198099 as a "todo" here.
                    $vals['sha1'] = '';
                }
            }
        }
 
        try {
            if ( $this->fld_roles ) {
                $vals['roles'] = $revision->getSlotRoles();
            }
 
            if ( $this->needSlots ) {
                $revDel = $this->checkRevDel( $revision, RevisionRecord::DELETED_TEXT );
                if ( ( $this->fld_slotsha1 || $this->fetchContent ) && ( $revDel & self::IS_DELETED ) ) {
                    $anyHidden = true;
                }
                $vals = array_merge( $vals, $this->extractAllSlotInfo( $revision, $revDel ) );
            }
        } catch ( RevisionAccessException $ex ) {
            // This is here so T212428 doesn't spam the log.
            // TODO: find out why T212428 happens in the first place!
            $vals['slotsmissing'] = true;
 
            LoggerFactory::getInstance( 'api-warning' )->error(
                'Failed to access revision slots',
                [ 'revision' => $revision->getId(), 'exception' => $ex, ]
            );
        }
 
        if ( $this->fld_comment || $this->fld_parsedcomment ) {
            $revDel = $this->checkRevDel( $revision, RevisionRecord::DELETED_COMMENT );
            if ( $revDel & self::IS_DELETED ) {
                $vals['commenthidden'] = true;
                $anyHidden = true;
            }
            if ( !( $revDel & self::CANNOT_VIEW ) ) {
                $comment = $revision->getComment( RevisionRecord::RAW );
                $comment = $comment->text ?? '';
 
                if ( $this->fld_comment ) {
                    $vals['comment'] = $comment;
                }
 
                if ( $this->fld_parsedcomment ) {
                    $vals['parsedcomment'] = $this->commentFormatter->format(
                        $comment, Title::newFromLinkTarget( $revision->getPageAsLinkTarget() )
                    );
                }
            }
        }
 
        if ( $this->fld_tags ) {
            if ( $row->ts_tags ) {
                $tags = explode( ',', $row->ts_tags );
                ApiResult::setIndexedTagName( $tags, 'tag' );
                $vals['tags'] = $tags;
            } else {
                $vals['tags'] = [];
            }
        }
 
        if ( $anyHidden && $revision->isDeleted( RevisionRecord::DELETED_RESTRICTED ) ) {
            $vals['suppressed'] = true;
        }
 
        return $vals;
    }
 
    private function extractAllSlotInfo( RevisionRecord $revision, $revDel ): array {
        $vals = [];
 
        if ( $this->slotRoles === null ) {
            try {
                $slot = $revision->getSlot( SlotRecord::MAIN, RevisionRecord::RAW );
            } catch ( RevisionAccessException $e ) {
                // Back compat: If there's no slot, there's no content, so set 'textmissing'
                // @todo: Gergő says to mention T198099 as a "todo" here.
                $vals['textmissing'] = true;
                $slot = null;
            }
 
            if ( $slot ) {
                $content = null;
                $vals += $this->extractSlotInfo( $slot, $revDel, $content );
                if ( !empty( $vals['nosuchsection'] ) ) {
                    $this->dieWithError(
                        [
                            'apierror-nosuchsection-what',
                            wfEscapeWikiText( $this->section ),
                            $this->msg( 'revid', $revision->getId() )
                        ],
                        'nosuchsection'
                    );
                }
                if ( $content ) {
                    $vals += $this->extractDeprecatedContent( $content, $revision );
                }
            }
        } else {
            $roles = array_intersect( $this->slotRoles, $revision->getSlotRoles() );
            $vals['slots'] = [
                ApiResult::META_KVP_MERGE => true,
            ];
            foreach ( $roles as $role ) {
                try {
                    $slot = $revision->getSlot( $role, RevisionRecord::RAW );
                } catch ( RevisionAccessException $e ) {
                    // Don't error out here so the client can still process other slots/revisions.
                    // @todo: Gergő says to mention T198099 as a "todo" here.
                    $vals['slots'][$role]['missing'] = true;
                    continue;
                }
                $content = null;
                $vals['slots'][$role] = $this->extractSlotInfo( $slot, $revDel, $content );
                // @todo Move this into extractSlotInfo() (and remove its $content parameter)
                // when extractDeprecatedContent() is no more.
                if ( $content ) {
                    $model = $content->getModel();
                    $format = $this->slotContentFormats[$role] ?? $content->getDefaultFormat();
                    if ( !$content->isSupportedFormat( $format ) ) {
                        $this->addWarning( [
                            'apierror-badformat',
                            $format,
                            $model,
                            $this->msg( 'revid', $revision->getId() )
                        ] );
                        $vals['slots'][$role]['badcontentformat'] = true;
                    } else {
                        $vals['slots'][$role]['contentmodel'] = $model;
                        $vals['slots'][$role]['contentformat'] = $format;
                        ApiResult::setContentValue(
                            $vals['slots'][$role],
                            'content',
                            $content->serialize( $format )
                        );
                    }
                }
            }
            ApiResult::setArrayType( $vals['slots'], 'kvp', 'role' );
            ApiResult::setIndexedTagName( $vals['slots'], 'slot' );
        }
        return $vals;
    }
 
    private function extractSlotInfo( SlotRecord $slot, $revDel, &$content = null ) {
        $vals = [];
        ApiResult::setArrayType( $vals, 'assoc' );
 
        if ( $this->fld_slotsize ) {
            $vals['size'] = (int)$slot->getSize();
        }
 
        if ( $this->fld_slotsha1 ) {
            if ( $revDel & self::IS_DELETED ) {
                $vals['sha1hidden'] = true;
            }
            if ( !( $revDel & self::CANNOT_VIEW ) ) {
                if ( $slot->getSha1() != '' ) {
                    $vals['sha1'] = Wikimedia\base_convert( $slot->getSha1(), 36, 16, 40 );
                } else {
                    $vals['sha1'] = '';
                }
            }
        }
 
        if ( $this->fld_contentmodel ) {
            $vals['contentmodel'] = $slot->getModel();
        }
 
        $content = null;
        if ( $this->fetchContent ) {
            if ( $revDel & self::IS_DELETED ) {
                $vals['texthidden'] = true;
            }
            if ( !( $revDel & self::CANNOT_VIEW ) ) {
                try {
                    $content = $slot->getContent();
                } catch ( RevisionAccessException $e ) {
                    // @todo: Gergő says to mention T198099 as a "todo" here.
                    $vals['textmissing'] = true;
                }
                // Expand templates after getting section content because
                // template-added sections don't count and Parser::preprocess()
                // will have less input
                if ( $content && $this->section !== false ) {
                    $content = $content->getSection( $this->section );
                    if ( !$content ) {
                        $vals['nosuchsection'] = true;
                    }
                }
            }
        }
 
        return $vals;
    }
 
    private function extractDeprecatedContent( Content $content, RevisionRecord $revision ) {
        $vals = [];
        $title = Title::newFromLinkTarget( $revision->getPageAsLinkTarget() );
 
        if ( $this->fld_parsetree || ( $this->fld_content && $this->generateXML ) ) {
            if ( $content->getModel() === CONTENT_MODEL_WIKITEXT ) {
                '@phan-var WikitextContent $content';
                $t = $content->getText(); # note: don't set $text
 
                $parser = $this->parserFactory->create();
                $parser->startExternalParse(
                    $title,
                    ParserOptions::newFromContext( $this->getContext() ),
                    Parser::OT_PREPROCESS
                );
                $dom = $parser->preprocessToDom( $t );
                // @phan-suppress-next-line PhanUndeclaredMethodInCallable
                if ( is_callable( [ $dom, 'saveXML' ] ) ) {
                    // @phan-suppress-next-line PhanUndeclaredMethod
                    $xml = $dom->saveXML();
                } else {
                    // @phan-suppress-next-line PhanUndeclaredMethod
                    $xml = $dom->__toString();
                }
                $vals['parsetree'] = $xml;
            } else {
                $vals['badcontentformatforparsetree'] = true;
                $this->addWarning(
                    [
                        'apierror-parsetree-notwikitext-title',
                        wfEscapeWikiText( $title->getPrefixedText() ),
                        $content->getModel()
                    ],
                    'parsetree-notwikitext'
                );
            }
        }
 
        if ( $this->fld_content ) {
            $text = null;
 
            if ( $this->expandTemplates && !$this->parseContent ) {
                if ( $content->getModel() === CONTENT_MODEL_WIKITEXT ) {
                    '@phan-var WikitextContent $content';
                    $text = $content->getText();
 
                    $text = $this->parserFactory->create()->preprocess(
                        $text,
                        $title,
                        ParserOptions::newFromContext( $this->getContext() )
                    );
                } else {
                    $this->addWarning( [
                        'apierror-templateexpansion-notwikitext',
                        wfEscapeWikiText( $title->getPrefixedText() ),
                        $content->getModel()
                    ] );
                    $vals['badcontentformat'] = true;
                    $text = false;
                }
            }
            if ( $this->parseContent ) {
                $popts = ParserOptions::newFromContext( $this->getContext() );
                $po = $this->contentRenderer->getParserOutput(
                    $content,
                    $title,
                    $revision,
                    $popts
                );
                // TODO T371004 move runOutputPipeline out of $parserOutput
                $text = $po->runOutputPipeline( $popts, [] )->getContentHolderText();
            }
 
            if ( $text === null ) {
                $format = $this->contentFormat ?: $content->getDefaultFormat();
                $model = $content->getModel();
 
                if ( !$content->isSupportedFormat( $format ) ) {
                    $name = wfEscapeWikiText( $title->getPrefixedText() );
                    $this->addWarning( [ 'apierror-badformat', $this->contentFormat, $model, $name ] );
                    $vals['badcontentformat'] = true;
                    $text = false;
                } else {
                    $text = $content->serialize( $format );
                    // always include format and model.
                    // Format is needed to deserialize, model is needed to interpret.
                    $vals['contentformat'] = $format;
                    $vals['contentmodel'] = $model;
                }
            }
 
            if ( $text !== false ) {
                ApiResult::setContentValue( $vals, 'content', $text );
            }
        }
 
        if ( $content && ( $this->diffto !== null || $this->difftotext !== null ) ) {
            if ( $this->numUncachedDiffs < $this->getConfig()->get( MainConfigNames::APIMaxUncachedDiffs ) ) {
                $vals['diff'] = [];
                $context = new DerivativeContext( $this->getContext() );
                $context->setTitle( $title );
                $handler = $content->getContentHandler();
 
                if ( $this->difftotext !== null ) {
                    $model = $title->getContentModel();
 
                    if ( $this->contentFormat
                        && !$this->contentHandlerFactory->getContentHandler( $model )
                            ->isSupportedFormat( $this->contentFormat )
                    ) {
                        $name = wfEscapeWikiText( $title->getPrefixedText() );
                        $this->addWarning( [ 'apierror-badformat', $this->contentFormat, $model, $name ] );
                        $vals['diff']['badcontentformat'] = true;
                        $engine = null;
                    } else {
                        $difftocontent = $this->contentHandlerFactory->getContentHandler( $model )
                            ->unserializeContent( $this->difftotext, $this->contentFormat );
 
                        if ( $this->difftotextpst ) {
                            $popts = ParserOptions::newFromContext( $this->getContext() );
                            $difftocontent = $this->contentTransformer->preSaveTransform(
                                $difftocontent,
                                $title,
                                $this->getUserForPreview(),
                                $popts
                            );
                        }
 
                        $engine = $handler->createDifferenceEngine( $context );
                        $engine->setContent( $content, $difftocontent );
                    }
                } else {
                    $engine = $handler->createDifferenceEngine( $context, $revision->getId(), $this->diffto );
                    $vals['diff']['from'] = $engine->getOldid();
                    $vals['diff']['to'] = $engine->getNewid();
                }
                if ( $engine ) {
                    $difftext = $engine->getDiffBody();
                    ApiResult::setContentValue( $vals['diff'], 'body', $difftext );
                    if ( !$engine->wasCacheHit() ) {
                        $this->numUncachedDiffs++;
                    }
                    foreach ( $engine->getRevisionLoadErrors() as $msg ) {
                        $this->addWarning( $msg );
                    }
                }
            } else {
                $vals['diff']['notcached'] = true;
            }
        }
 
        return $vals;
    }
 
    private function getUserForPreview() {
        $user = $this->getUser();
        if ( $this->tempUserCreator->shouldAutoCreate( $user, 'edit' ) ) {
            return $this->userFactory->newUnsavedTempUser(
                $this->tempUserCreator->getStashedName( $this->getRequest()->getSession() )
            );
        }
        return $user;
    }
 
    public function getCacheMode( $params ) {
        if ( $this->userCanSeeRevDel() ) {
            return 'private';
        }
 
        return 'public';
    }
 
    public function getAllowedParams() {
        $slotRoles = $this->slotRoleRegistry->getKnownRoles();
        sort( $slotRoles, SORT_STRING );
        $smallLimit = $this->getMain()->canApiHighLimits() ? ApiBase::LIMIT_SML2 : ApiBase::LIMIT_SML1;
 
        return [
            'prop' => [
                ParamValidator::PARAM_ISMULTI => true,
                ParamValidator::PARAM_DEFAULT => 'ids|timestamp|flags|comment|user',
                ParamValidator::PARAM_TYPE => [
                    'ids',
                    'flags',
                    'timestamp',
                    'user',
                    'userid',
                    'size',
                    'slotsize',
                    'sha1',
                    'slotsha1',
                    'contentmodel',
                    'comment',
                    'parsedcomment',
                    'content',
                    'tags',
                    'roles',
                    'parsetree',
                ],
                ApiBase::PARAM_HELP_MSG => 'apihelp-query+revisions+base-param-prop',
                ApiBase::PARAM_HELP_MSG_PER_VALUE => [
                    'ids' => 'apihelp-query+revisions+base-paramvalue-prop-ids',
                    'flags' => 'apihelp-query+revisions+base-paramvalue-prop-flags',
                    'timestamp' => 'apihelp-query+revisions+base-paramvalue-prop-timestamp',
                    'user' => 'apihelp-query+revisions+base-paramvalue-prop-user',
                    'userid' => 'apihelp-query+revisions+base-paramvalue-prop-userid',
                    'size' => 'apihelp-query+revisions+base-paramvalue-prop-size',
                    'slotsize' => 'apihelp-query+revisions+base-paramvalue-prop-slotsize',
                    'sha1' => 'apihelp-query+revisions+base-paramvalue-prop-sha1',
                    'slotsha1' => 'apihelp-query+revisions+base-paramvalue-prop-slotsha1',
                    'contentmodel' => 'apihelp-query+revisions+base-paramvalue-prop-contentmodel',
                    'comment' => 'apihelp-query+revisions+base-paramvalue-prop-comment',
                    'parsedcomment' => 'apihelp-query+revisions+base-paramvalue-prop-parsedcomment',
                    'content' => [ 'apihelp-query+revisions+base-paramvalue-prop-content', $smallLimit ],
                    'tags' => 'apihelp-query+revisions+base-paramvalue-prop-tags',
                    'roles' => 'apihelp-query+revisions+base-paramvalue-prop-roles',
                    'parsetree' => [ 'apihelp-query+revisions+base-paramvalue-prop-parsetree',
                        CONTENT_MODEL_WIKITEXT, $smallLimit ],
                ],
                EnumDef::PARAM_DEPRECATED_VALUES => [
                    'parsetree' => true,
                ],
            ],
            'slots' => [
                ParamValidator::PARAM_TYPE => $slotRoles,
                ApiBase::PARAM_HELP_MSG => 'apihelp-query+revisions+base-param-slots',
                ParamValidator::PARAM_ISMULTI => true,
                ParamValidator::PARAM_ALL => true,
            ],
            'contentformat-{slot}' => [
                ApiBase::PARAM_TEMPLATE_VARS => [ 'slot' => 'slots' ],
                ApiBase::PARAM_HELP_MSG => 'apihelp-query+revisions+base-param-contentformat-slot',
                ParamValidator::PARAM_TYPE => $this->contentHandlerFactory->getAllContentFormats(),
            ],
            'limit' => [
                ParamValidator::PARAM_TYPE => 'limit',
                IntegerDef::PARAM_MIN => 1,
                IntegerDef::PARAM_MAX => ApiBase::LIMIT_BIG1,
                IntegerDef::PARAM_MAX2 => ApiBase::LIMIT_BIG2,
                ApiBase::PARAM_HELP_MSG => [ 'apihelp-query+revisions+base-param-limit',
                    $smallLimit, self::LIMIT_PARSE ],
            ],
            'expandtemplates' => [
                ParamValidator::PARAM_DEFAULT => false,
                ApiBase::PARAM_HELP_MSG => 'apihelp-query+revisions+base-param-expandtemplates',
                ParamValidator::PARAM_DEPRECATED => true,
            ],
            'generatexml' => [
                ParamValidator::PARAM_DEFAULT => false,
                ParamValidator::PARAM_DEPRECATED => true,
                ApiBase::PARAM_HELP_MSG => 'apihelp-query+revisions+base-param-generatexml',
            ],
            'parse' => [
                ParamValidator::PARAM_DEFAULT => false,
                ApiBase::PARAM_HELP_MSG => [ 'apihelp-query+revisions+base-param-parse', self::LIMIT_PARSE ],
                ParamValidator::PARAM_DEPRECATED => true,
            ],
            'section' => [
                ApiBase::PARAM_HELP_MSG => 'apihelp-query+revisions+base-param-section',
            ],
            'diffto' => [
                ApiBase::PARAM_HELP_MSG => [ 'apihelp-query+revisions+base-param-diffto', $smallLimit ],
                ParamValidator::PARAM_DEPRECATED => true,
            ],
            'difftotext' => [
                ApiBase::PARAM_HELP_MSG => [ 'apihelp-query+revisions+base-param-difftotext', $smallLimit ],
                ParamValidator::PARAM_DEPRECATED => true,
            ],
            'difftotextpst' => [
                ParamValidator::PARAM_DEFAULT => false,
                ApiBase::PARAM_HELP_MSG => 'apihelp-query+revisions+base-param-difftotextpst',
                ParamValidator::PARAM_DEPRECATED => true,
            ],
            'contentformat' => [
                ParamValidator::PARAM_TYPE => $this->contentHandlerFactory->getAllContentFormats(),
                ApiBase::PARAM_HELP_MSG => 'apihelp-query+revisions+base-param-contentformat',
                ParamValidator::PARAM_DEPRECATED => true,
            ],
        ];
    }
}