includes/search/SearchEngine.php

   1 <?php
   2 /**
   3  * Basic search engine
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup Search
  22  */
  23
  24 /**
  25  * @defgroup Search Search
  26  */
  27
  28 use MediaWiki\MediaWikiServices;
  29
  30 /**
  31  * Contain a class for special pages
  32  * @ingroup Search
  33  */
  34 abstract class SearchEngine {
  35         const DEFAULT_SORT = 'relevance';
  36
  37         /** @var string */
  38         public $prefix = '';
  39
  40         /** @var int[]|null */
  41         public $namespaces = [ NS_MAIN ];
  42
  43         /** @var int */
  44         protected $limit = 10;
  45
  46         /** @var int */
  47         protected $offset = 0;
  48
  49         /** @var array|string */
  50         protected $searchTerms = [];
  51
  52         /** @var bool */
  53         protected $showSuggestion = true;
  54         private $sort = self::DEFAULT_SORT;
  55
  56         /** @var array Feature values */
  57         protected $features = [];
  58
  59         /** @const string profile type for completionSearch */
  60         const COMPLETION_PROFILE_TYPE = 'completionSearchProfile';
  61
  62         /** @const string profile type for query independent ranking features */
  63         const FT_QUERY_INDEP_PROFILE_TYPE = 'fulltextQueryIndepProfile';
  64
  65         /** @const int flag for legalSearchChars: includes all chars allowed in a search query */
  66         const CHARS_ALL = 1;
  67
  68         /** @const int flag for legalSearchChars: includes all chars allowed in a search term */
  69         const CHARS_NO_SYNTAX = 2;
  70
  71         /**
  72          * Perform a full text search query and return a result set.
  73          * If full text searches are not supported or disabled, return null.
  74          *
  75          * As of 1.32 overriding this function is deprecated. It will
  76          * be converted to final in 1.34. Override self::doSearchText().
  77          *
  78          * @param string $term Raw search term
  79          * @return SearchResultSet|Status|null
  80          */
  81         public function searchText( $term ) {
  82                 return $this->maybePaginate( function () use ( $term ) {
  83                         return $this->doSearchText( $term );
  84                 } );
  85         }
  86
  87         /**
  88          * Perform a full text search query and return a result set.
  89          *
  90          * @param string $term Raw search term
  91          * @return SearchResultSet|Status|null
  92          * @since 1.32
  93          */
  94         protected function doSearchText( $term ) {
  95                 return null;
  96         }
  97
  98         /**
  99          * Perform a title search in the article archive.
 100          * NOTE: these results still should be filtered by
 101          * matching against PageArchive, permissions checks etc
 102          * The results returned by this methods are only sugegstions and
 103          * may not end up being shown to the user.
 104          *
 105          * As of 1.32 overriding this function is deprecated. It will
 106          * be converted to final in 1.34. Override self::doSearchArchiveTitle().
 107          *
 108          * @param string $term Raw search term
 109          * @return Status<Title[]>
 110          * @since 1.29
 111          */
 112         public function searchArchiveTitle( $term ) {
 113                 return $this->doSearchArchiveTitle( $term );
 114         }
 115
 116         /**
 117          * Perform a title search in the article archive.
 118          *
 119          * @param string $term Raw search term
 120          * @return Status<Title[]>
 121          * @since 1.32
 122          */
 123         protected function doSearchArchiveTitle( $term ) {
 124                 return Status::newGood( [] );
 125         }
 126
 127         /**
 128          * Perform a title-only search query and return a result set.
 129          * If title searches are not supported or disabled, return null.
 130          * STUB
 131          *
 132          * As of 1.32 overriding this function is deprecated. It will
 133          * be converted to final in 1.34. Override self::doSearchTitle().
 134          *
 135          * @param string $term Raw search term
 136          * @return SearchResultSet|null
 137          */
 138         public function searchTitle( $term ) {
 139                 return $this->maybePaginate( function () use ( $term ) {
 140                         return $this->doSearchTitle( $term );
 141                 } );
 142         }
 143
 144         /**
 145          * Perform a title-only search query and return a result set.
 146          *
 147          * @param string $term Raw search term
 148          * @return SearchResultSet|null
 149          * @since 1.32
 150          */
 151         protected function doSearchTitle( $term ) {
 152                 return null;
 153         }
 154
 155         /**
 156          * Performs an overfetch and shrink operation to determine if
 157          * the next page is available for search engines that do not
 158          * explicitly implement their own pagination.
 159          *
 160          * @param Closure $fn Takes no arguments
 161          * @return SearchResultSet|Status<SearchResultSet>|null Result of calling $fn
 162          */
 163         private function maybePaginate( Closure $fn ) {
 164                 if ( $this instanceof PaginatingSearchEngine ) {
 165                         return $fn();
 166                 }
 167                 $this->limit++;
 168                 try {
 169                         $resultSetOrStatus = $fn();
 170                 } finally {
 171                         $this->limit--;
 172                 }
 173
 174                 $resultSet = null;
 175                 if ( $resultSetOrStatus instanceof SearchResultSet ) {
 176                         $resultSet = $resultSetOrStatus;
 177                 } elseif ( $resultSetOrStatus instanceof Status &&
 178                         $resultSetOrStatus->getValue() instanceof SearchResultSet
 179                 ) {
 180                         $resultSet = $resultSetOrStatus->getValue();
 181                 }
 182                 if ( $resultSet ) {
 183                         $resultSet->shrink( $this->limit );
 184                 }
 185
 186                 return $resultSetOrStatus;
 187         }
 188
 189         /**
 190          * @since 1.18
 191          * @param string $feature
 192          * @return bool
 193          */
 194         public function supports( $feature ) {
 195                 switch ( $feature ) {
 196                         case 'search-update':
 197                                 return true;
 198                         case 'title-suffix-filter':
 199                         default:
 200                                 return false;
 201                 }
 202         }
 203
 204         /**
 205          * Way to pass custom data for engines
 206          * @since 1.18
 207          * @param string $feature
 208          * @param mixed $data
 209          */
 210         public function setFeatureData( $feature, $data ) {
 211                 $this->features[$feature] = $data;
 212         }
 213
 214         /**
 215          * Way to retrieve custom data set by setFeatureData
 216          * or by the engine itself.
 217          * @since 1.29
 218          * @param string $feature feature name
 219          * @return mixed the feature value or null if unset
 220          */
 221         public function getFeatureData( $feature ) {
 222                 if ( isset( $this->features[$feature] ) ) {
 223                         return $this->features[$feature];
 224                 }
 225                 return null;
 226         }
 227
 228         /**
 229          * When overridden in derived class, performs database-specific conversions
 230          * on text to be used for searching or updating search index.
 231          * Default implementation does nothing (simply returns $string).
 232          *
 233          * @param string $string String to process
 234          * @return string
 235          */
 236         public function normalizeText( $string ) {
 237                 // Some languages such as Chinese require word segmentation
 238                 return MediaWikiServices::getInstance()->getContentLanguage()->segmentByWord( $string );
 239         }
 240
 241         /**
 242          * Transform search term in cases when parts of the query came as different
 243          * GET params (when supported), e.g. for prefix queries:
 244          * search=test&prefix=Main_Page/Archive -> test prefix:Main Page/Archive
 245          * @param string $term
 246          * @return string
 247          * @deprecated since 1.32 this should now be handled internally by the
 248          * search engine
 249          */
 250         public function transformSearchTerm( $term ) {
 251                 return $term;
 252         }
 253
 254         /**
 255          * Get service class to finding near matches.
 256          * @param Config $config Configuration to use for the matcher.
 257          * @return SearchNearMatcher
 258          */
 259         public function getNearMatcher( Config $config ) {
 260                 return new SearchNearMatcher( $config,
 261                         MediaWikiServices::getInstance()->getContentLanguage() );
 262         }
 263
 264         /**
 265          * Get near matcher for default SearchEngine.
 266          * @return SearchNearMatcher
 267          */
 268         protected static function defaultNearMatcher() {
 269                 $services = MediaWikiServices::getInstance();
 270                 $config = $services->getMainConfig();
 271                 return $services->newSearchEngine()->getNearMatcher( $config );
 272         }
 273
 274         /**
 275          * If an exact title match can be found, or a very slightly close match,
 276          * return the title. If no match, returns NULL.
 277          * @deprecated since 1.27; Use SearchEngine::getNearMatcher()
 278          * @param string $searchterm
 279          * @return Title
 280          */
 281         public static function getNearMatch( $searchterm ) {
 282                 return static::defaultNearMatcher()->getNearMatch( $searchterm );
 283         }
 284
 285         /**
 286          * Do a near match (see SearchEngine::getNearMatch) and wrap it into a
 287          * SearchResultSet.
 288          * @deprecated since 1.27; Use SearchEngine::getNearMatcher()
 289          * @param string $searchterm
 290          * @return SearchResultSet
 291          */
 292         public static function getNearMatchResultSet( $searchterm ) {
 293                 return static::defaultNearMatcher()->getNearMatchResultSet( $searchterm );
 294         }
 295
 296         /**
 297          * Get chars legal for search
 298          * NOTE: usage as static is deprecated and preserved only as BC measure
 299          * @param int $type type of search chars (see self::CHARS_ALL
 300          * and self::CHARS_NO_SYNTAX). Defaults to CHARS_ALL
 301          * @return string
 302          */
 303         public static function legalSearchChars( $type = self::CHARS_ALL ) {
 304                 return "A-Za-z_'.0-9\\x80-\\xFF\\-";
 305         }
 306
 307         /**
 308          * Set the maximum number of results to return
 309          * and how many to skip before returning the first.
 310          *
 311          * @param int $limit
 312          * @param int $offset
 313          */
 314         function setLimitOffset( $limit, $offset = 0 ) {
 315                 $this->limit = intval( $limit );
 316                 $this->offset = intval( $offset );
 317         }
 318
 319         /**
 320          * Set which namespaces the search should include.
 321          * Give an array of namespace index numbers.
 322          *
 323          * @param int[]|null $namespaces
 324          */
 325         function setNamespaces( $namespaces ) {
 326                 if ( $namespaces ) {
 327                         // Filter namespaces to only keep valid ones
 328                         $validNs = $this->searchableNamespaces();
 329                         $namespaces = array_filter( $namespaces, function ( $ns ) use( $validNs ) {
 330                                 return $ns < 0 || isset( $validNs[$ns] );
 331                         } );
 332                 } else {
 333                         $namespaces = [];
 334                 }
 335                 $this->namespaces = $namespaces;
 336         }
 337
 338         /**
 339          * Set whether the searcher should try to build a suggestion.  Note: some searchers
 340          * don't support building a suggestion in the first place and others don't respect
 341          * this flag.
 342          *
 343          * @param bool $showSuggestion Should the searcher try to build suggestions
 344          */
 345         function setShowSuggestion( $showSuggestion ) {
 346                 $this->showSuggestion = $showSuggestion;
 347         }
 348
 349         /**
 350          * Get the valid sort directions.  All search engines support 'relevance' but others
 351          * might support more. The default in all implementations must be 'relevance.'
 352          *
 353          * @since 1.25
 354          * @return string[] the valid sort directions for setSort
 355          */
 356         public function getValidSorts() {
 357                 return [ self::DEFAULT_SORT ];
 358         }
 359
 360         /**
 361          * Set the sort direction of the search results. Must be one returned by
 362          * SearchEngine::getValidSorts()
 363          *
 364          * @since 1.25
 365          * @throws InvalidArgumentException
 366          * @param string $sort sort direction for query result
 367          */
 368         public function setSort( $sort ) {
 369                 if ( !in_array( $sort, $this->getValidSorts() ) ) {
 370                         throw new InvalidArgumentException( "Invalid sort: $sort. " .
 371                                 "Must be one of: " . implode( ', ', $this->getValidSorts() ) );
 372                 }
 373                 $this->sort = $sort;
 374         }
 375
 376         /**
 377          * Get the sort direction of the search results
 378          *
 379          * @since 1.25
 380          * @return string
 381          */
 382         public function getSort() {
 383                 return $this->sort;
 384         }
 385
 386         /**
 387          * Parse some common prefixes: all (search everything)
 388          * or namespace names and set the list of namespaces
 389          * of this class accordingly.
 390          *
 391          * @deprecated since 1.32; should be handled internally by the search engine
 392          * @param string $query
 393          * @return string
 394          */
 395         function replacePrefixes( $query ) {
 396                 return $query;
 397         }
 398
 399         /**
 400          * Parse some common prefixes: all (search everything)
 401          * or namespace names
 402          *
 403          * @param string $query
 404          * @param bool $withAllKeyword activate support of the "all:" keyword and its
 405          * translations to activate searching on all namespaces.
 406          * @param bool $withPrefixSearchExtractNamespaceHook call the PrefixSearchExtractNamespace hook
 407          *  if classic namespace identification did not match.
 408          * @return false|array false if no namespace was extracted, an array
 409          * with the parsed query at index 0 and an array of namespaces at index
 410          * 1 (or null for all namespaces).
 411          * @throws FatalError
 412          * @throws MWException
 413          */
 414         public static function parseNamespacePrefixes(
 415                 $query,
 416                 $withAllKeyword = true,
 417                 $withPrefixSearchExtractNamespaceHook = false
 418         ) {
 419                 $parsed = $query;
 420                 if ( strpos( $query, ':' ) === false ) { // nothing to do
 421                         return false;
 422                 }
 423                 $extractedNamespace = null;
 424
 425                 $allQuery = false;
 426                 if ( $withAllKeyword ) {
 427                         $allkeywords = [];
 428
 429                         $allkeywords[] = wfMessage( 'searchall' )->inContentLanguage()->text() . ":";
 430                         // force all: so that we have a common syntax for all the wikis
 431                         if ( !in_array( 'all:', $allkeywords ) ) {
 432                                 $allkeywords[] = 'all:';
 433                         }
 434
 435                         foreach ( $allkeywords as $kw ) {
 436                                 if ( strncmp( $query, $kw, strlen( $kw ) ) == 0 ) {
 437                                         $extractedNamespace = null;
 438                                         $parsed = substr( $query, strlen( $kw ) );
 439                                         $allQuery = true;
 440                                         break;
 441                                 }
 442                         }
 443                 }
 444
 445                 if ( !$allQuery && strpos( $query, ':' ) !== false ) {
 446                         $prefix = str_replace( ' ', '_', substr( $query, 0, strpos( $query, ':' ) ) );
 447                         $index = MediaWikiServices::getInstance()->getContentLanguage()->getNsIndex( $prefix );
 448                         if ( $index !== false ) {
 449                                 $extractedNamespace = [ $index ];
 450                                 $parsed = substr( $query, strlen( $prefix ) + 1 );
 451                         } elseif ( $withPrefixSearchExtractNamespaceHook ) {
 452                                 $hookNamespaces = [ NS_MAIN ];
 453                                 $hookQuery = $query;
 454                                 Hooks::run( 'PrefixSearchExtractNamespace', [ &$hookNamespaces, &$hookQuery ] );
 455                                 if ( $hookQuery !== $query ) {
 456                                         $parsed = $hookQuery;
 457                                         $extractedNamespace = $hookNamespaces;
 458                                 } else {
 459                                         return false;
 460                                 }
 461                         } else {
 462                                 return false;
 463                         }
 464                 }
 465
 466                 return [ $parsed, $extractedNamespace ];
 467         }
 468
 469         /**
 470          * Find snippet highlight settings for all users
 471          * @return array Contextlines, contextchars
 472          */
 473         public static function userHighlightPrefs() {
 474                 $contextlines = 2; // Hardcode this. Old defaults sucked. :)
 475                 $contextchars = 75; // same as above.... :P
 476                 return [ $contextlines, $contextchars ];
 477         }
 478
 479         /**
 480          * Create or update the search index record for the given page.
 481          * Title and text should be pre-processed.
 482          * STUB
 483          *
 484          * @param int $id
 485          * @param string $title
 486          * @param string $text
 487          */
 488         function update( $id, $title, $text ) {
 489                 // no-op
 490         }
 491
 492         /**
 493          * Update a search index record's title only.
 494          * Title should be pre-processed.
 495          * STUB
 496          *
 497          * @param int $id
 498          * @param string $title
 499          */
 500         function updateTitle( $id, $title ) {
 501                 // no-op
 502         }
 503
 504         /**
 505          * Delete an indexed page
 506          * Title should be pre-processed.
 507          * STUB
 508          *
 509          * @param int $id Page id that was deleted
 510          * @param string $title Title of page that was deleted
 511          */
 512         function delete( $id, $title ) {
 513                 // no-op
 514         }
 515
 516         /**
 517          * Get the raw text for updating the index from a content object
 518          * Nicer search backends could possibly do something cooler than
 519          * just returning raw text
 520          *
 521          * @todo This isn't ideal, we'd really like to have content-specific handling here
 522          * @param Title $t Title we're indexing
 523          * @param Content|null $c Content of the page to index
 524          * @return string
 525          */
 526         public function getTextFromContent( Title $t, Content $c = null ) {
 527                 return $c ? $c->getTextForSearchIndex() : '';
 528         }
 529
 530         /**
 531          * If an implementation of SearchEngine handles all of its own text processing
 532          * in getTextFromContent() and doesn't require SearchUpdate::updateText()'s
 533          * rather silly handling, it should return true here instead.
 534          *
 535          * @return bool
 536          */
 537         public function textAlreadyUpdatedForIndex() {
 538                 return false;
 539         }
 540
 541         /**
 542          * Makes search simple string if it was namespaced.
 543          * Sets namespaces of the search to namespaces extracted from string.
 544          * @param string $search
 545          * @return string Simplified search string
 546          */
 547         protected function normalizeNamespaces( $search ) {
 548                 $queryAndNs = self::parseNamespacePrefixes( $search, false, true );
 549                 if ( $queryAndNs !== false ) {
 550                         $this->setNamespaces( $queryAndNs[1] );
 551                         return $queryAndNs[0];
 552                 }
 553                 return $search;
 554         }
 555
 556         /**
 557          * Perform an overfetch of completion search results. This allows
 558          * determining if another page of results is available.
 559          *
 560          * @param string $search
 561          * @return SearchSuggestionSet
 562          */
 563         protected function completionSearchBackendOverfetch( $search ) {
 564                 $this->limit++;
 565                 try {
 566                         return $this->completionSearchBackend( $search );
 567                 } finally {
 568                         $this->limit--;
 569                 }
 570         }
 571
 572         /**
 573          * Perform a completion search.
 574          * Does not resolve namespaces and does not check variants.
 575          * Search engine implementations may want to override this function.
 576          * @param string $search
 577          * @return SearchSuggestionSet
 578          */
 579         protected function completionSearchBackend( $search ) {
 580                 $results = [];
 581
 582                 $search = trim( $search );
 583
 584                 if ( !in_array( NS_SPECIAL, $this->namespaces ) && // We do not run hook on Special: search
 585                          !Hooks::run( 'PrefixSearchBackend',
 586                                 [ $this->namespaces, $search, $this->limit, &$results, $this->offset ]
 587                 ) ) {
 588                         // False means hook worked.
 589                         // FIXME: Yes, the API is weird. That's why it is going to be deprecated.
 590
 591                         return SearchSuggestionSet::fromStrings( $results );
 592                 } else {
 593                         // Hook did not do the job, use default simple search
 594                         $results = $this->simplePrefixSearch( $search );
 595                         return SearchSuggestionSet::fromTitles( $results );
 596                 }
 597         }
 598
 599         /**
 600          * Perform a completion search.
 601          * @param string $search
 602          * @return SearchSuggestionSet
 603          */
 604         public function completionSearch( $search ) {
 605                 if ( trim( $search ) === '' ) {
 606                         return SearchSuggestionSet::emptySuggestionSet(); // Return empty result
 607                 }
 608                 $search = $this->normalizeNamespaces( $search );
 609                 $suggestions = $this->completionSearchBackendOverfetch( $search );
 610                 return $this->processCompletionResults( $search, $suggestions );
 611         }
 612
 613         /**
 614          * Perform a completion search with variants.
 615          * @param string $search
 616          * @return SearchSuggestionSet
 617          */
 618         public function completionSearchWithVariants( $search ) {
 619                 if ( trim( $search ) === '' ) {
 620                         return SearchSuggestionSet::emptySuggestionSet(); // Return empty result
 621                 }
 622                 $search = $this->normalizeNamespaces( $search );
 623
 624                 $results = $this->completionSearchBackendOverfetch( $search );
 625                 $fallbackLimit = 1 + $this->limit - $results->getSize();
 626                 if ( $fallbackLimit > 0 ) {
 627                         $fallbackSearches = MediaWikiServices::getInstance()->getContentLanguage()->
 628                                 autoConvertToAllVariants( $search );
 629                         $fallbackSearches = array_diff( array_unique( $fallbackSearches ), [ $search ] );
 630
 631                         foreach ( $fallbackSearches as $fbs ) {
 632                                 $this->setLimitOffset( $fallbackLimit );
 633                                 $fallbackSearchResult = $this->completionSearch( $fbs );
 634                                 $results->appendAll( $fallbackSearchResult );
 635                                 $fallbackLimit -= $fallbackSearchResult->getSize();
 636                                 if ( $fallbackLimit <= 0 ) {
 637                                         break;
 638                                 }
 639                         }
 640                 }
 641                 return $this->processCompletionResults( $search, $results );
 642         }
 643
 644         /**
 645          * Extract titles from completion results
 646          * @param SearchSuggestionSet $completionResults
 647          * @return Title[]
 648          */
 649         public function extractTitles( SearchSuggestionSet $completionResults ) {
 650                 return $completionResults->map( function ( SearchSuggestion $sugg ) {
 651                         return $sugg->getSuggestedTitle();
 652                 } );
 653         }
 654
 655         /**
 656          * Process completion search results.
 657          * Resolves the titles and rescores.
 658          * @param string $search
 659          * @param SearchSuggestionSet $suggestions
 660          * @return SearchSuggestionSet
 661          */
 662         protected function processCompletionResults( $search, SearchSuggestionSet $suggestions ) {
 663                 // We over-fetched to determine pagination. Shrink back down if we have extra results
 664                 // and mark if pagination is possible
 665                 $suggestions->shrink( $this->limit );
 666
 667                 $search = trim( $search );
 668                 // preload the titles with LinkBatch
 669                 $lb = new LinkBatch( $suggestions->map( function ( SearchSuggestion $sugg ) {
 670                         return $sugg->getSuggestedTitle();
 671                 } ) );
 672                 $lb->setCaller( __METHOD__ );
 673                 $lb->execute();
 674
 675                 $diff = $suggestions->filter( function ( SearchSuggestion $sugg ) {
 676                         return $sugg->getSuggestedTitle()->isKnown();
 677                 } );
 678                 if ( $diff > 0 ) {
 679                         MediaWikiServices::getInstance()->getStatsdDataFactory()
 680                                 ->updateCount( 'search.completion.missing', $diff );
 681                 }
 682
 683                 $results = $suggestions->map( function ( SearchSuggestion $sugg ) {
 684                         return $sugg->getSuggestedTitle()->getPrefixedText();
 685                 } );
 686
 687                 if ( $this->offset === 0 ) {
 688                         // Rescore results with an exact title match
 689                         // NOTE: in some cases like cross-namespace redirects
 690                         // (frequently used as shortcuts e.g. WP:WP on huwiki) some
 691                         // backends like Cirrus will return no results. We should still
 692                         // try an exact title match to workaround this limitation
 693                         $rescorer = new SearchExactMatchRescorer();
 694                         $rescoredResults = $rescorer->rescore( $search, $this->namespaces, $results, $this->limit );
 695                 } else {
 696                         // No need to rescore if offset is not 0
 697                         // The exact match must have been returned at position 0
 698                         // if it existed.
 699                         $rescoredResults = $results;
 700                 }
 701
 702                 if ( count( $rescoredResults ) > 0 ) {
 703                         $found = array_search( $rescoredResults[0], $results );
 704                         if ( $found === false ) {
 705                                 // If the first result is not in the previous array it
 706                                 // means that we found a new exact match
 707                                 $exactMatch = SearchSuggestion::fromTitle( 0, Title::newFromText( $rescoredResults[0] ) );
 708                                 $suggestions->prepend( $exactMatch );
 709                                 $suggestions->shrink( $this->limit );
 710                         } else {
 711                                 // if the first result is not the same we need to rescore
 712                                 if ( $found > 0 ) {
 713                                         $suggestions->rescore( $found );
 714                                 }
 715                         }
 716                 }
 717
 718                 return $suggestions;
 719         }
 720
 721         /**
 722          * Simple prefix search for subpages.
 723          * @param string $search
 724          * @return Title[]
 725          */
 726         public function defaultPrefixSearch( $search ) {
 727                 if ( trim( $search ) === '' ) {
 728                         return [];
 729                 }
 730
 731                 $search = $this->normalizeNamespaces( $search );
 732                 return $this->simplePrefixSearch( $search );
 733         }
 734
 735         /**
 736          * Call out to simple search backend.
 737          * Defaults to TitlePrefixSearch.
 738          * @param string $search
 739          * @return Title[]
 740          */
 741         protected function simplePrefixSearch( $search ) {
 742                 // Use default database prefix search
 743                 $backend = new TitlePrefixSearch;
 744                 return $backend->defaultSearchBackend( $this->namespaces, $search, $this->limit, $this->offset );
 745         }
 746
 747         /**
 748          * Make a list of searchable namespaces and their canonical names.
 749          * @deprecated since 1.27; use SearchEngineConfig::searchableNamespaces()
 750          * @return array
 751          */
 752         public static function searchableNamespaces() {
 753                 return MediaWikiServices::getInstance()->getSearchEngineConfig()->searchableNamespaces();
 754         }
 755
 756         /**
 757          * Extract default namespaces to search from the given user's
 758          * settings, returning a list of index numbers.
 759          * @deprecated since 1.27; use SearchEngineConfig::userNamespaces()
 760          * @param user $user
 761          * @return array
 762          */
 763         public static function userNamespaces( $user ) {
 764                 return MediaWikiServices::getInstance()->getSearchEngineConfig()->userNamespaces( $user );
 765         }
 766
 767         /**
 768          * An array of namespaces indexes to be searched by default
 769          * @deprecated since 1.27; use SearchEngineConfig::defaultNamespaces()
 770          * @return array
 771          */
 772         public static function defaultNamespaces() {
 773                 return MediaWikiServices::getInstance()->getSearchEngineConfig()->defaultNamespaces();
 774         }
 775
 776         /**
 777          * Get a list of namespace names useful for showing in tooltips
 778          * and preferences
 779          * @deprecated since 1.27; use SearchEngineConfig::namespacesAsText()
 780          * @param array $namespaces
 781          * @return array
 782          */
 783         public static function namespacesAsText( $namespaces ) {
 784                 return MediaWikiServices::getInstance()->getSearchEngineConfig()->namespacesAsText( $namespaces );
 785         }
 786
 787         /**
 788          * Load up the appropriate search engine class for the currently
 789          * active database backend, and return a configured instance.
 790          * @deprecated since 1.27; Use SearchEngineFactory::create
 791          * @param string $type Type of search backend, if not the default
 792          * @return SearchEngine
 793          */
 794         public static function create( $type = null ) {
 795                 return MediaWikiServices::getInstance()->getSearchEngineFactory()->create( $type );
 796         }
 797
 798         /**
 799          * Return the search engines we support. If only $wgSearchType
 800          * is set, it'll be an array of just that one item.
 801          * @deprecated since 1.27; use SearchEngineConfig::getSearchTypes()
 802          * @return array
 803          */
 804         public static function getSearchTypes() {
 805                 return MediaWikiServices::getInstance()->getSearchEngineConfig()->getSearchTypes();
 806         }
 807
 808         /**
 809          * Get a list of supported profiles.
 810          * Some search engine implementations may expose specific profiles to fine-tune
 811          * its behaviors.
 812          * The profile can be passed as a feature data with setFeatureData( $profileType, $profileName )
 813          * The array returned by this function contains the following keys:
 814          * - name: the profile name to use with setFeatureData
 815          * - desc-message: the i18n description
 816          * - default: set to true if this profile is the default
 817          *
 818          * @since 1.28
 819          * @param string $profileType the type of profiles
 820          * @param User|null $user the user requesting the list of profiles
 821          * @return array|null the list of profiles or null if none available
 822          */
 823         public function getProfiles( $profileType, User $user = null ) {
 824                 return null;
 825         }
 826
 827         /**
 828          * Create a search field definition.
 829          * Specific search engines should override this method to create search fields.
 830          * @param string $name
 831          * @param int $type One of the types in SearchIndexField::INDEX_TYPE_*
 832          * @return SearchIndexField
 833          * @since 1.28
 834          */
 835         public function makeSearchFieldMapping( $name, $type ) {
 836                 return new NullIndexField();
 837         }
 838
 839         /**
 840          * Get fields for search index
 841          * @since 1.28
 842          * @return SearchIndexField[] Index field definitions for all content handlers
 843          */
 844         public function getSearchIndexFields() {
 845                 $models = ContentHandler::getContentModels();
 846                 $fields = [];
 847                 $seenHandlers = new SplObjectStorage();
 848                 foreach ( $models as $model ) {
 849                         try {
 850                                 $handler = ContentHandler::getForModelID( $model );
 851                         }
 852                         catch ( MWUnknownContentModelException $e ) {
 853                                 // If we can find no handler, ignore it
 854                                 continue;
 855                         }
 856                         // Several models can have the same handler, so avoid processing it repeatedly
 857                         if ( $seenHandlers->contains( $handler ) ) {
 858                                 // We already did this one
 859                                 continue;
 860                         }
 861                         $seenHandlers->attach( $handler );
 862                         $handlerFields = $handler->getFieldsForSearchIndex( $this );
 863                         foreach ( $handlerFields as $fieldName => $fieldData ) {
 864                                 if ( empty( $fields[$fieldName] ) ) {
 865                                         $fields[$fieldName] = $fieldData;
 866                                 } else {
 867                                         // TODO: do we allow some clashes with the same type or reject all of them?
 868                                         $mergeDef = $fields[$fieldName]->merge( $fieldData );
 869                                         if ( !$mergeDef ) {
 870                                                 throw new InvalidArgumentException( "Duplicate field $fieldName for model $model" );
 871                                         }
 872                                         $fields[$fieldName] = $mergeDef;
 873                                 }
 874                         }
 875                 }
 876                 // Hook to allow extensions to produce search mapping fields
 877                 Hooks::run( 'SearchIndexFields', [ &$fields, $this ] );
 878                 return $fields;
 879         }
 880
 881         /**
 882          * Augment search results with extra data.
 883          *
 884          * @param SearchResultSet $resultSet
 885          */
 886         public function augmentSearchResults( SearchResultSet $resultSet ) {
 887                 $setAugmentors = [];
 888                 $rowAugmentors = [];
 889                 Hooks::run( "SearchResultsAugment", [ &$setAugmentors, &$rowAugmentors ] );
 890                 if ( !$setAugmentors && !$rowAugmentors ) {
 891                         // We're done here
 892                         return;
 893                 }
 894
 895                 // Convert row augmentors to set augmentor
 896                 foreach ( $rowAugmentors as $name => $row ) {
 897                         if ( isset( $setAugmentors[$name] ) ) {
 898                                 throw new InvalidArgumentException( "Both row and set augmentors are defined for $name" );
 899                         }
 900                         $setAugmentors[$name] = new PerRowAugmentor( $row );
 901                 }
 902
 903                 foreach ( $setAugmentors as $name => $augmentor ) {
 904                         $data = $augmentor->augmentAll( $resultSet );
 905                         if ( $data ) {
 906                                 $resultSet->setAugmentedData( $name, $data );
 907                         }
 908                 }
 909         }
 910 }
 911
 912 /**
 913  * Dummy class to be used when non-supported Database engine is present.
 914  * @todo FIXME: Dummy class should probably try something at least mildly useful,
 915  * such as a LIKE search through titles.
 916  * @ingroup Search
 917  */
 918 class SearchEngineDummy extends SearchEngine {
 919         // no-op
 920 }