wikimedia/mediawiki-core

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includes/search/SearchEngine.php

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<?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\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;
    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
     * @throws InvalidArgumentException
     * @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;
    }

}