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[mediawiki.git] / includes / search / SearchEngine.php

<?php
/**
 * Basic search engine
 *
 * 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
 * @ingroup Search
 */

/**
 * @defgroup Search Search
 */

use MediaWiki\Config\Config;
use MediaWiki\Content\Content;
use MediaWiki\HookContainer\HookContainer;
use MediaWiki\HookContainer\HookRunner;
use MediaWiki\MediaWikiServices;
use MediaWiki\Search\TitleMatcher;
use MediaWiki\Status\Status;
use MediaWiki\Title\Title;
use MediaWiki\User\User;

/**
 * Contain a class for special pages
 * @stable to extend
 * @ingroup Search
 */
abstract class SearchEngine {
        public const DEFAULT_SORT = 'relevance';

        /** @var string */
        public $prefix = '';

        /** @var int[]|null */
        public $namespaces = [ NS_MAIN ];

        /** @var int */
        protected $limit = 10;

        /** @var int */
        protected $offset = 0;

        /**
         * @var string[]
         * @deprecated since 1.34
         */
        protected $searchTerms = [];

        /** @var bool */
        protected $showSuggestion = true;
        /** @var string */
        private $sort = self::DEFAULT_SORT;

        /** @var array Feature values */
        protected $features = [];

        /** @var HookContainer */
        private $hookContainer;

        /** @var HookRunner */
        private $hookRunner;

        /** Profile type for completionSearch */
        public const COMPLETION_PROFILE_TYPE = 'completionSearchProfile';

        /** Profile type for query independent ranking features */
        public const FT_QUERY_INDEP_PROFILE_TYPE = 'fulltextQueryIndepProfile';

        /** Integer flag for legalSearchChars: includes all chars allowed in a search query */
        protected const CHARS_ALL = 1;

        /** Integer flag for legalSearchChars: includes all chars allowed in a search term */
        protected const CHARS_NO_SYNTAX = 2;

        /**
         * Perform a full text search query and return a result set.
         * If full text searches are not supported or disabled, return null.
         *
         * @note As of 1.32 overriding this function is deprecated. It will
         * be converted to final in 1.34. Override self::doSearchText().
         *
         * @param string $term Raw search term
         * @return ISearchResultSet|Status|null
         */
        public function searchText( $term ) {
                return $this->maybePaginate( function () use ( $term ) {
                        return $this->doSearchText( $term );
                } );
        }

        /**
         * Perform a full text search query and return a result set.
         *
         * @stable to override
         *
         * @param string $term Raw search term
         * @return ISearchResultSet|Status|null
         * @since 1.32
         */
        protected function doSearchText( $term ) {
                return null;
        }

        /**
         * Perform a title search in the article archive.
         * NOTE: these results still should be filtered by
         * matching against PageArchive, permissions checks etc
         * The results returned by this methods are only suggestions and
         * may not end up being shown to the user.
         *
         * @note As of 1.32 overriding this function is deprecated. It will
         * be converted to final in 1.34. Override self::doSearchArchiveTitle().
         *
         * @param string $term Raw search term
         * @return Status
         * @since 1.29
         */
        public function searchArchiveTitle( $term ) {
                return $this->doSearchArchiveTitle( $term );
        }

        /**
         * Perform a title search in the article archive.
         *
         * @stable to override
         *
         * @param string $term Raw search term
         * @return Status
         * @since 1.32
         */
        protected function doSearchArchiveTitle( $term ) {
                return Status::newGood( [] );
        }

        /**
         * Perform a title-only search query and return a result set.
         * If title searches are not supported or disabled, return null.
         * STUB
         *
         * @note As of 1.32 overriding this function is deprecated. It will
         * be converted to final in 1.34. Override self::doSearchTitle().
         *
         * @param string $term Raw search term
         * @return ISearchResultSet|null
         */
        public function searchTitle( $term ) {
                return $this->maybePaginate( function () use ( $term ) {
                        return $this->doSearchTitle( $term );
                } );
        }

        /**
         * Perform a title-only search query and return a result set.
         *
         * @stable to override
         *
         * @param string $term Raw search term
         * @return ISearchResultSet|null
         * @since 1.32
         */
        protected function doSearchTitle( $term ) {
                return null;
        }

        /**
         * Performs an overfetch and shrink operation to determine if
         * the next page is available for search engines that do not
         * explicitly implement their own pagination.
         *
         * @param Closure $fn Takes no arguments
         * @return ISearchResultSet|Status<ISearchResultSet>|null Result of calling $fn
         */
        private function maybePaginate( Closure $fn ) {
                if ( $this instanceof PaginatingSearchEngine ) {
                        return $fn();
                }
                $this->limit++;
                try {
                        $resultSetOrStatus = $fn();
                } finally {
                        $this->limit--;
                }

                $resultSet = null;
                if ( $resultSetOrStatus instanceof ISearchResultSet ) {
                        $resultSet = $resultSetOrStatus;
                } elseif ( $resultSetOrStatus instanceof Status &&
                        $resultSetOrStatus->getValue() instanceof ISearchResultSet
                ) {
                        $resultSet = $resultSetOrStatus->getValue();
                }
                if ( $resultSet ) {
                        $resultSet->shrink( $this->limit );
                }

                return $resultSetOrStatus;
        }

        /**
         * @since 1.18
         * @stable to override
         *
         * @param string $feature
         * @return bool
         */
        public function supports( $feature ) {
                switch ( $feature ) {
                        case 'search-update':
                                return true;
                        case 'title-suffix-filter':
                        default:
                                return false;
                }
        }

        /**
         * Way to pass custom data for engines
         * @since 1.18
         * @param string $feature
         * @param mixed $data
         */
        public function setFeatureData( $feature, $data ) {
                $this->features[$feature] = $data;
        }

        /**
         * Way to retrieve custom data set by setFeatureData
         * or by the engine itself.
         * @since 1.29
         * @param string $feature feature name
         * @return mixed the feature value or null if unset
         */
        public function getFeatureData( $feature ) {
                return $this->features[$feature] ?? null;
        }

        /**
         * When overridden in derived class, performs database-specific conversions
         * on text to be used for searching or updating search index.
         * Default implementation does nothing (simply returns $string).
         *
         * @param string $string String to process
         * @return string
         */
        public function normalizeText( $string ) {
                // Some languages such as Chinese require word segmentation
                return MediaWikiServices::getInstance()->getContentLanguage()->segmentByWord( $string );
        }

        /**
         * Get service class to finding near matches.
         *
         * @return TitleMatcher
         * @deprecated since 1.40, use MediaWikiServices::getInstance()->getTitleMatcher()
         */
        public function getNearMatcher( Config $config ) {
                return MediaWikiServices::getInstance()->getTitleMatcher();
        }

        /**
         * Get near matcher for default SearchEngine.
         *
         * @return TitleMatcher
         * @deprecated since 1.40, MediaWikiServices::getInstance()->getTitleMatcher()
         */
        protected static function defaultNearMatcher() {
                wfDeprecated( __METHOD__, '1.40' );
                return MediaWikiServices::getInstance()->getTitleMatcher();
        }

        /**
         * Get chars legal for search
         * @param int $type type of search chars (see self::CHARS_ALL
         * and self::CHARS_NO_SYNTAX). Defaults to CHARS_ALL
         * @return string
         */
        public function legalSearchChars( $type = self::CHARS_ALL ) {
                return "A-Za-z_'.0-9\\x80-\\xFF\\-";
        }

        /**
         * Set the maximum number of results to return
         * and how many to skip before returning the first.
         *
         * @param int $limit
         * @param int $offset
         */
        public function setLimitOffset( $limit, $offset = 0 ) {
                $this->limit = intval( $limit );
                $this->offset = intval( $offset );
        }

        /**
         * Set which namespaces the search should include.
         * Give an array of namespace index numbers.
         *
         * @param int[]|null $namespaces
         */
        public function setNamespaces( $namespaces ) {
                if ( $namespaces ) {
                        // Filter namespaces to only keep valid ones
                        $validNs = MediaWikiServices::getInstance()->getSearchEngineConfig()->searchableNamespaces();
                        $namespaces = array_filter( $namespaces, static function ( $ns ) use( $validNs ) {
                                return $ns < 0 || isset( $validNs[$ns] );
                        } );
                } else {
                        $namespaces = [];
                }
                $this->namespaces = $namespaces;
        }

        /**
         * Set whether the searcher should try to build a suggestion.  Note: some searchers
         * don't support building a suggestion in the first place and others don't respect
         * this flag.
         *
         * @param bool $showSuggestion Should the searcher try to build suggestions
         */
        public function setShowSuggestion( $showSuggestion ) {
                $this->showSuggestion = $showSuggestion;
        }

        /**
         * Get the valid sort directions.  All search engines support 'relevance' but others
         * might support more. The default in all implementations must be 'relevance.'
         *
         * @since 1.25
         * @stable to override
         *
         * @return string[] the valid sort directions for setSort
         */
        public function getValidSorts() {
                return [ self::DEFAULT_SORT ];
        }

        /**
         * Set the sort direction of the search results. Must be one returned by
         * SearchEngine::getValidSorts()
         *
         * @since 1.25
         * @param string $sort sort direction for query result
         */
        public function setSort( $sort ) {
                if ( !in_array( $sort, $this->getValidSorts() ) ) {
                        throw new InvalidArgumentException( "Invalid sort: $sort. " .
                                "Must be one of: " . implode( ', ', $this->getValidSorts() ) );
                }
                $this->sort = $sort;
        }

        /**
         * Get the sort direction of the search results
         *
         * @since 1.25
         * @return string
         */
        public function getSort() {
                return $this->sort;
        }

        /**
         * Parse some common prefixes: all (search everything)
         * or namespace names and set the list of namespaces
         * of this class accordingly.
         *
         * @deprecated since 1.32; should be handled internally by the search engine
         * @param string $query
         * @return string
         */
        public function replacePrefixes( $query ) {
                return $query;
        }

        /**
         * Parse some common prefixes: all (search everything)
         * or namespace names
         *
         * @param string $query
         * @param bool $withAllKeyword activate support of the "all:" keyword and its
         * translations to activate searching on all namespaces.
         * @param bool $withPrefixSearchExtractNamespaceHook call the PrefixSearchExtractNamespace hook
         *  if classic namespace identification did not match.
         * @return false|array false if no namespace was extracted, an array
         * with the parsed query at index 0 and an array of namespaces at index
         * 1 (or null for all namespaces).
         */
        public static function parseNamespacePrefixes(
                $query,
                $withAllKeyword = true,
                $withPrefixSearchExtractNamespaceHook = false
        ) {
                $parsed = $query;
                if ( strpos( $query, ':' ) === false ) { // nothing to do
                        return false;
                }
                $extractedNamespace = null;

                $allQuery = false;
                if ( $withAllKeyword ) {
                        $allkeywords = [];

                        $allkeywords[] = wfMessage( 'searchall' )->inContentLanguage()->text() . ":";
                        // force all: so that we have a common syntax for all the wikis
                        if ( !in_array( 'all:', $allkeywords ) ) {
                                $allkeywords[] = 'all:';
                        }

                        foreach ( $allkeywords as $kw ) {
                                if ( str_starts_with( $query, $kw ) ) {
                                        $parsed = substr( $query, strlen( $kw ) );
                                        $allQuery = true;
                                        break;
                                }
                        }
                }

                if ( !$allQuery && strpos( $query, ':' ) !== false ) {
                        $prefix = str_replace( ' ', '_', substr( $query, 0, strpos( $query, ':' ) ) );
                        $services = MediaWikiServices::getInstance();
                        $index = $services->getContentLanguage()->getNsIndex( $prefix );
                        if ( $index !== false ) {
                                $extractedNamespace = [ $index ];
                                $parsed = substr( $query, strlen( $prefix ) + 1 );
                        } elseif ( $withPrefixSearchExtractNamespaceHook ) {
                                $hookNamespaces = [ NS_MAIN ];
                                $hookQuery = $query;
                                ( new HookRunner( $services->getHookContainer() ) )
                                        ->onPrefixSearchExtractNamespace( $hookNamespaces, $hookQuery );
                                if ( $hookQuery !== $query ) {
                                        $parsed = $hookQuery;
                                        $extractedNamespace = $hookNamespaces;
                                } else {
                                        return false;
                                }
                        } else {
                                return false;
                        }
                }

                return [ $parsed, $extractedNamespace ];
        }

        /**
         * Find snippet highlight settings for all users
         * @return array Contextlines, contextchars
         * @deprecated since 1.34; use the SearchHighlighter constants directly
         * @see SearchHighlighter::DEFAULT_CONTEXT_CHARS
         * @see SearchHighlighter::DEFAULT_CONTEXT_LINES
         */
        public static function userHighlightPrefs() {
                $contextlines = SearchHighlighter::DEFAULT_CONTEXT_LINES;
                $contextchars = SearchHighlighter::DEFAULT_CONTEXT_CHARS;
                return [ $contextlines, $contextchars ];
        }

        /**
         * Create or update the search index record for the given page.
         * Title and text should be pre-processed.
         * STUB
         *
         * @param int $id
         * @param string $title
         * @param string $text
         */
        public function update( $id, $title, $text ) {
                // no-op
        }

        /**
         * Update a search index record's title only.
         * Title should be pre-processed.
         * STUB
         *
         * @param int $id
         * @param string $title
         */
        public function updateTitle( $id, $title ) {
                // no-op
        }

        /**
         * Delete an indexed page
         * Title should be pre-processed.
         * STUB
         *
         * @param int $id Page id that was deleted
         * @param string $title Title of page that was deleted
         */
        public function delete( $id, $title ) {
                // no-op
        }

        /**
         * Get the raw text for updating the index from a content object
         * Nicer search backends could possibly do something cooler than
         * just returning raw text
         *
         * @todo This isn't ideal, we'd really like to have content-specific handling here
         * @param Title $t Title we're indexing
         * @param Content|null $c Content of the page to index
         * @return string
         * @deprecated since 1.34 use Content::getTextForSearchIndex directly
         */
        public function getTextFromContent( Title $t, ?Content $c = null ) {
                return $c ? $c->getTextForSearchIndex() : '';
        }

        /**
         * If an implementation of SearchEngine handles all of its own text processing
         * in getTextFromContent() and doesn't require SearchUpdate::updateText()'s
         * rather silly handling, it should return true here instead.
         *
         * @return bool
         * @deprecated since 1.34 no longer needed since getTextFromContent is being deprecated
         */
        public function textAlreadyUpdatedForIndex() {
                return false;
        }

        /**
         * Makes search simple string if it was namespaced.
         * Sets namespaces of the search to namespaces extracted from string.
         * @param string $search
         * @return string Simplified search string
         */
        protected function normalizeNamespaces( $search ) {
                $queryAndNs = self::parseNamespacePrefixes( $search, false, true );
                if ( $queryAndNs !== false ) {
                        $this->setNamespaces( $queryAndNs[1] );
                        return $queryAndNs[0];
                }
                return $search;
        }

        /**
         * Perform an overfetch of completion search results. This allows
         * determining if another page of results is available.
         *
         * @param string $search
         * @return SearchSuggestionSet
         */
        protected function completionSearchBackendOverfetch( $search ) {
                $this->limit++;
                try {
                        return $this->completionSearchBackend( $search );
                } finally {
                        $this->limit--;
                }
        }

        /**
         * Perform a completion search.
         * Does not resolve namespaces and does not check variants.
         * Search engine implementations may want to override this function.
         *
         * @stable to override
         *
         * @param string $search
         * @return SearchSuggestionSet
         */
        protected function completionSearchBackend( $search ) {
                $results = [];

                $search = trim( $search );

                if ( !in_array( NS_SPECIAL, $this->namespaces ) && // We do not run hook on Special: search
                        !$this->getHookRunner()->onPrefixSearchBackend(
                                $this->namespaces, $search, $this->limit, $results, $this->offset )
                ) {
                        // False means hook worked.
                        // FIXME: Yes, the API is weird. That's why it is going to be deprecated.

                        return SearchSuggestionSet::fromStrings( $results );
                } else {
                        // Hook did not do the job, use default simple search
                        $results = $this->simplePrefixSearch( $search );
                        return SearchSuggestionSet::fromTitles( $results );
                }
        }

        /**
         * Perform a completion search.
         * @param string $search
         * @return SearchSuggestionSet
         */
        public function completionSearch( $search ) {
                if ( trim( $search ) === '' ) {
                        return SearchSuggestionSet::emptySuggestionSet(); // Return empty result
                }
                $search = $this->normalizeNamespaces( $search );
                $suggestions = $this->completionSearchBackendOverfetch( $search );
                return $this->processCompletionResults( $search, $suggestions );
        }

        /**
         * Perform a completion search with variants.
         * @stable to override
         *
         * @param string $search
         * @return SearchSuggestionSet
         */
        public function completionSearchWithVariants( $search ) {
                if ( trim( $search ) === '' ) {
                        return SearchSuggestionSet::emptySuggestionSet(); // Return empty result
                }
                $search = $this->normalizeNamespaces( $search );

                $results = $this->completionSearchBackendOverfetch( $search );
                $fallbackLimit = 1 + $this->limit - $results->getSize();
                if ( $fallbackLimit > 0 ) {
                        $services = MediaWikiServices::getInstance();
                        $fallbackSearches = $services->getLanguageConverterFactory()
                                ->getLanguageConverter( $services->getContentLanguage() )
                                ->autoConvertToAllVariants( $search );
                        $fallbackSearches = array_diff( array_unique( $fallbackSearches ), [ $search ] );

                        foreach ( $fallbackSearches as $fbs ) {
                                $this->setLimitOffset( $fallbackLimit );
                                $fallbackSearchResult = $this->completionSearch( $fbs );
                                $results->appendAll( $fallbackSearchResult );
                                $fallbackLimit -= $fallbackSearchResult->getSize();
                                if ( $fallbackLimit <= 0 ) {
                                        break;
                                }
                        }
                }
                return $this->processCompletionResults( $search, $results );
        }

        /**
         * Extract titles from completion results
         * @param SearchSuggestionSet $completionResults
         * @return Title[]
         */
        public function extractTitles( SearchSuggestionSet $completionResults ) {
                return $completionResults->map( static function ( SearchSuggestion $sugg ) {
                        return $sugg->getSuggestedTitle();
                } );
        }

        /**
         * Process completion search results.
         * Resolves the titles and rescores.
         * @param string $search
         * @param SearchSuggestionSet $suggestions
         * @return SearchSuggestionSet
         */
        protected function processCompletionResults( $search, SearchSuggestionSet $suggestions ) {
                // We over-fetched to determine pagination. Shrink back down if we have extra results
                // and mark if pagination is possible
                $suggestions->shrink( $this->limit );

                $search = trim( $search );
                // preload the titles with LinkBatch
                $linkBatchFactory = MediaWikiServices::getInstance()->getLinkBatchFactory();
                $lb = $linkBatchFactory->newLinkBatch( $suggestions->map( static function ( SearchSuggestion $sugg ) {
                        return $sugg->getSuggestedTitle();
                } ) );
                $lb->setCaller( __METHOD__ );
                $lb->execute();

                $diff = $suggestions->filter( static function ( SearchSuggestion $sugg ) {
                        return $sugg->getSuggestedTitle()->isKnown();
                } );
                if ( $diff > 0 ) {
                        MediaWikiServices::getInstance()->getStatsdDataFactory()
                                ->updateCount( 'search.completion.missing', $diff );
                }

                // SearchExactMatchRescorer should probably be refactored to work directly on top of a SearchSuggestionSet
                // instead of converting it to array and trying to infer if it has re-scored anything by inspected the head
                // of the returned array.
                $results = $suggestions->map( static function ( SearchSuggestion $sugg ) {
                        return $sugg->getSuggestedTitle()->getPrefixedText();
                } );

                $rescorer = new SearchExactMatchRescorer();
                if ( $this->offset === 0 ) {
                        // Rescore results with an exact title match
                        // NOTE: in some cases like cross-namespace redirects
                        // (frequently used as shortcuts e.g. WP:WP on huwiki) some
                        // backends like Cirrus will return no results. We should still
                        // try an exact title match to workaround this limitation
                        $rescoredResults = $rescorer->rescore( $search, $this->namespaces, $results, $this->limit );
                } else {
                        // No need to rescore if offset is not 0
                        // The exact match must have been returned at position 0
                        // if it existed.
                        $rescoredResults = $results;
                }

                if ( count( $rescoredResults ) > 0 ) {
                        $found = array_search( $rescoredResults[0], $results );
                        if ( $found === false ) {
                                // If the first result is not in the previous array it
                                // means that we found a new exact match
                                $exactMatch = SearchSuggestion::fromTitle( 0, Title::newFromText( $rescoredResults[0] ) );
                                $suggestions->prepend( $exactMatch );
                                if ( $rescorer->getReplacedRedirect() !== null ) {
                                        // the exact match rescorer replaced one of the suggestion found by the search engine
                                        // let's remove it from our suggestions set to avoid showing duplicates
                                        $suggestions->remove( SearchSuggestion::fromTitle( 0,
                                                Title::newFromText( $rescorer->getReplacedRedirect() ) ) );
                                }
                                $suggestions->shrink( $this->limit );
                        } else {
                                // if the first result is not the same we need to rescore
                                if ( $found > 0 ) {
                                        $suggestions->rescore( $found );
                                }
                        }
                }

                return $suggestions;
        }

        /**
         * Simple prefix search for subpages.
         * @param string $search
         * @return Title[]
         */
        public function defaultPrefixSearch( $search ) {
                if ( trim( $search ) === '' ) {
                        return [];
                }

                $search = $this->normalizeNamespaces( $search );
                return $this->simplePrefixSearch( $search );
        }

        /**
         * Call out to simple search backend.
         * Defaults to TitlePrefixSearch.
         * @param string $search
         * @return Title[]
         */
        protected function simplePrefixSearch( $search ) {
                // Use default database prefix search
                $backend = new TitlePrefixSearch;
                return $backend->defaultSearchBackend( $this->namespaces, $search, $this->limit, $this->offset );
        }

        /**
         * Get a list of supported profiles.
         * Some search engine implementations may expose specific profiles to fine-tune
         * its behaviors.
         * The profile can be passed as a feature data with setFeatureData( $profileType, $profileName )
         * The array returned by this function contains the following keys:
         * - name: the profile name to use with setFeatureData
         * - desc-message: the i18n description
         * - default: set to true if this profile is the default
         *
         * @since 1.28
         * @stable to override
         *
         * @param string $profileType the type of profiles
         * @param User|null $user the user requesting the list of profiles
         * @return array|null the list of profiles or null if none available
         * @phan-return null|array{name:string,desc-message:string,default?:bool}
         */
        public function getProfiles( $profileType, ?User $user = null ) {
                return null;
        }

        /**
         * Create a search field definition.
         * Specific search engines should override this method to create search fields.
         * @stable to override
         *
         * @param string $name
         * @param string $type One of the types in SearchIndexField::INDEX_TYPE_*
         * @return SearchIndexField
         * @since 1.28
         */
        public function makeSearchFieldMapping( $name, $type ) {
                return new NullIndexField();
        }

        /**
         * Get fields for search index
         * @since 1.28
         * @return SearchIndexField[] Index field definitions for all content handlers
         */
        public function getSearchIndexFields() {
                $models = MediaWikiServices::getInstance()->getContentHandlerFactory()->getContentModels();
                $fields = [];
                $seenHandlers = new SplObjectStorage();
                foreach ( $models as $model ) {
                        try {
                                $handler = MediaWikiServices::getInstance()
                                        ->getContentHandlerFactory()
                                        ->getContentHandler( $model );
                        } catch ( MWUnknownContentModelException $e ) {
                                // If we can find no handler, ignore it
                                continue;
                        }
                        // Several models can have the same handler, so avoid processing it repeatedly
                        if ( $seenHandlers->contains( $handler ) ) {
                                // We already did this one
                                continue;
                        }
                        $seenHandlers->attach( $handler );
                        $handlerFields = $handler->getFieldsForSearchIndex( $this );
                        foreach ( $handlerFields as $fieldName => $fieldData ) {
                                if ( empty( $fields[$fieldName] ) ) {
                                        $fields[$fieldName] = $fieldData;
                                } else {
                                        // TODO: do we allow some clashes with the same type or reject all of them?
                                        $mergeDef = $fields[$fieldName]->merge( $fieldData );
                                        if ( !$mergeDef ) {
                                                throw new InvalidArgumentException( "Duplicate field $fieldName for model $model" );
                                        }
                                        $fields[$fieldName] = $mergeDef;
                                }
                        }
                }
                // Hook to allow extensions to produce search mapping fields
                $this->getHookRunner()->onSearchIndexFields( $fields, $this );
                return $fields;
        }

        /**
         * Augment search results with extra data.
         *
         * @param ISearchResultSet $resultSet
         */
        public function augmentSearchResults( ISearchResultSet $resultSet ) {
                $setAugmentors = [];
                $rowAugmentors = [];
                $this->getHookRunner()->onSearchResultsAugment( $setAugmentors, $rowAugmentors );
                if ( !$setAugmentors && !$rowAugmentors ) {
                        // We're done here
                        return;
                }

                // Convert row augmentors to set augmentor
                foreach ( $rowAugmentors as $name => $row ) {
                        if ( isset( $setAugmentors[$name] ) ) {
                                throw new InvalidArgumentException( "Both row and set augmentors are defined for $name" );
                        }
                        $setAugmentors[$name] = new PerRowAugmentor( $row );
                }

                /**
                 * @var string $name
                 * @var ResultSetAugmentor $augmentor
                 */
                foreach ( $setAugmentors as $name => $augmentor ) {
                        $data = $augmentor->augmentAll( $resultSet );
                        if ( $data ) {
                                $resultSet->setAugmentedData( $name, $data );
                        }
                }
        }

        /**
         * @since 1.35
         * @internal
         * @param HookContainer $hookContainer
         */
        public function setHookContainer( HookContainer $hookContainer ) {
                $this->hookContainer = $hookContainer;
                $this->hookRunner = new HookRunner( $hookContainer );
        }

        /**
         * Get a HookContainer, for running extension hooks or for hook metadata.
         *
         * @since 1.35
         * @return HookContainer
         */
        protected function getHookContainer(): HookContainer {
                if ( !$this->hookContainer ) {
                        // This shouldn't be hit in core, but it is needed for CirrusSearch
                        // which commonly creates a CirrusSearch object without cirrus being
                        // configured in $wgSearchType/$wgSearchTypeAlternatives.
                        $this->hookContainer = MediaWikiServices::getInstance()->getHookContainer();
                }
                return $this->hookContainer;
        }

        /**
         * Get a HookRunner for running core hooks.
         *
         * @internal This is for use by core only. Hook interfaces may be removed
         *   without notice.
         * @since 1.35
         * @return HookRunner
         */
        protected function getHookRunner(): HookRunner {
                if ( !$this->hookRunner ) {
                        $this->hookRunner = new HookRunner( $this->getHookContainer() );
                }
                return $this->hookRunner;
        }

}