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                 return $this->features[$feature] ?? null;
 223         }
 224
 225         /**
 226          * When overridden in derived class, performs database-specific conversions
 227          * on text to be used for searching or updating search index.
 228          * Default implementation does nothing (simply returns $string).
 229          *
 230          * @param string $string String to process
 231          * @return string
 232          */
 233         public function normalizeText( $string ) {
 234                 // Some languages such as Chinese require word segmentation
 235                 return MediaWikiServices::getInstance()->getContentLanguage()->segmentByWord( $string );
 236         }
 237
 238         /**
 239          * Transform search term in cases when parts of the query came as different
 240          * GET params (when supported), e.g. for prefix queries:
 241          * search=test&prefix=Main_Page/Archive -> test prefix:Main Page/Archive
 242          * @param string $term
 243          * @return string
 244          * @deprecated since 1.32 this should now be handled internally by the
 245          * search engine
 246          */
 247         public function transformSearchTerm( $term ) {
 248                 return $term;
 249         }
 250
 251         /**
 252          * Get service class to finding near matches.
 253          * @param Config $config Configuration to use for the matcher.
 254          * @return SearchNearMatcher
 255          */
 256         public function getNearMatcher( Config $config ) {
 257                 return new SearchNearMatcher( $config,
 258                         MediaWikiServices::getInstance()->getContentLanguage() );
 259         }
 260
 261         /**
 262          * Get near matcher for default SearchEngine.
 263          * @return SearchNearMatcher
 264          */
 265         protected static function defaultNearMatcher() {
 266                 $services = MediaWikiServices::getInstance();
 267                 $config = $services->getMainConfig();
 268                 return $services->newSearchEngine()->getNearMatcher( $config );
 269         }
 270
 271         /**
 272          * If an exact title match can be found, or a very slightly close match,
 273          * return the title. If no match, returns NULL.
 274          * @deprecated since 1.27; Use SearchEngine::getNearMatcher()
 275          * @param string $searchterm
 276          * @return Title
 277          */
 278         public static function getNearMatch( $searchterm ) {
 279                 return static::defaultNearMatcher()->getNearMatch( $searchterm );
 280         }
 281
 282         /**
 283          * Get chars legal for search
 284          * NOTE: usage as static is deprecated and preserved only as BC measure
 285          * @param int $type type of search chars (see self::CHARS_ALL
 286          * and self::CHARS_NO_SYNTAX). Defaults to CHARS_ALL
 287          * @return string
 288          */
 289         public static function legalSearchChars( $type = self::CHARS_ALL ) {
 290                 return "A-Za-z_'.0-9\\x80-\\xFF\\-";
 291         }
 292
 293         /**
 294          * Set the maximum number of results to return
 295          * and how many to skip before returning the first.
 296          *
 297          * @param int $limit
 298          * @param int $offset
 299          */
 300         function setLimitOffset( $limit, $offset = 0 ) {
 301                 $this->limit = intval( $limit );
 302                 $this->offset = intval( $offset );
 303         }
 304
 305         /**
 306          * Set which namespaces the search should include.
 307          * Give an array of namespace index numbers.
 308          *
 309          * @param int[]|null $namespaces
 310          */
 311         function setNamespaces( $namespaces ) {
 312                 if ( $namespaces ) {
 313                         // Filter namespaces to only keep valid ones
 314                         $validNs = $this->searchableNamespaces();
 315                         $namespaces = array_filter( $namespaces, function ( $ns ) use( $validNs ) {
 316                                 return $ns < 0 || isset( $validNs[$ns] );
 317                         } );
 318                 } else {
 319                         $namespaces = [];
 320                 }
 321                 $this->namespaces = $namespaces;
 322         }
 323
 324         /**
 325          * Set whether the searcher should try to build a suggestion.  Note: some searchers
 326          * don't support building a suggestion in the first place and others don't respect
 327          * this flag.
 328          *
 329          * @param bool $showSuggestion Should the searcher try to build suggestions
 330          */
 331         function setShowSuggestion( $showSuggestion ) {
 332                 $this->showSuggestion = $showSuggestion;
 333         }
 334
 335         /**
 336          * Get the valid sort directions.  All search engines support 'relevance' but others
 337          * might support more. The default in all implementations must be 'relevance.'
 338          *
 339          * @since 1.25
 340          * @return string[] the valid sort directions for setSort
 341          */
 342         public function getValidSorts() {
 343                 return [ self::DEFAULT_SORT ];
 344         }
 345
 346         /**
 347          * Set the sort direction of the search results. Must be one returned by
 348          * SearchEngine::getValidSorts()
 349          *
 350          * @since 1.25
 351          * @throws InvalidArgumentException
 352          * @param string $sort sort direction for query result
 353          */
 354         public function setSort( $sort ) {
 355                 if ( !in_array( $sort, $this->getValidSorts() ) ) {
 356                         throw new InvalidArgumentException( "Invalid sort: $sort. " .
 357                                 "Must be one of: " . implode( ', ', $this->getValidSorts() ) );
 358                 }
 359                 $this->sort = $sort;
 360         }
 361
 362         /**
 363          * Get the sort direction of the search results
 364          *
 365          * @since 1.25
 366          * @return string
 367          */
 368         public function getSort() {
 369                 return $this->sort;
 370         }
 371
 372         /**
 373          * Parse some common prefixes: all (search everything)
 374          * or namespace names and set the list of namespaces
 375          * of this class accordingly.
 376          *
 377          * @deprecated since 1.32; should be handled internally by the search engine
 378          * @param string $query
 379          * @return string
 380          */
 381         function replacePrefixes( $query ) {
 382                 return $query;
 383         }
 384
 385         /**
 386          * Parse some common prefixes: all (search everything)
 387          * or namespace names
 388          *
 389          * @param string $query
 390          * @param bool $withAllKeyword activate support of the "all:" keyword and its
 391          * translations to activate searching on all namespaces.
 392          * @param bool $withPrefixSearchExtractNamespaceHook call the PrefixSearchExtractNamespace hook
 393          *  if classic namespace identification did not match.
 394          * @return false|array false if no namespace was extracted, an array
 395          * with the parsed query at index 0 and an array of namespaces at index
 396          * 1 (or null for all namespaces).
 397          * @throws FatalError
 398          * @throws MWException
 399          */
 400         public static function parseNamespacePrefixes(
 401                 $query,
 402                 $withAllKeyword = true,
 403                 $withPrefixSearchExtractNamespaceHook = false
 404         ) {
 405                 $parsed = $query;
 406                 if ( strpos( $query, ':' ) === false ) { // nothing to do
 407                         return false;
 408                 }
 409                 $extractedNamespace = null;
 410
 411                 $allQuery = false;
 412                 if ( $withAllKeyword ) {
 413                         $allkeywords = [];
 414
 415                         $allkeywords[] = wfMessage( 'searchall' )->inContentLanguage()->text() . ":";
 416                         // force all: so that we have a common syntax for all the wikis
 417                         if ( !in_array( 'all:', $allkeywords ) ) {
 418                                 $allkeywords[] = 'all:';
 419                         }
 420
 421                         foreach ( $allkeywords as $kw ) {
 422                                 if ( strncmp( $query, $kw, strlen( $kw ) ) == 0 ) {
 423                                         $extractedNamespace = null;
 424                                         $parsed = substr( $query, strlen( $kw ) );
 425                                         $allQuery = true;
 426                                         break;
 427                                 }
 428                         }
 429                 }
 430
 431                 if ( !$allQuery && strpos( $query, ':' ) !== false ) {
 432                         $prefix = str_replace( ' ', '_', substr( $query, 0, strpos( $query, ':' ) ) );
 433                         $index = MediaWikiServices::getInstance()->getContentLanguage()->getNsIndex( $prefix );
 434                         if ( $index !== false ) {
 435                                 $extractedNamespace = [ $index ];
 436                                 $parsed = substr( $query, strlen( $prefix ) + 1 );
 437                         } elseif ( $withPrefixSearchExtractNamespaceHook ) {
 438                                 $hookNamespaces = [ NS_MAIN ];
 439                                 $hookQuery = $query;
 440                                 Hooks::run( 'PrefixSearchExtractNamespace', [ &$hookNamespaces, &$hookQuery ] );
 441                                 if ( $hookQuery !== $query ) {
 442                                         $parsed = $hookQuery;
 443                                         $extractedNamespace = $hookNamespaces;
 444                                 } else {
 445                                         return false;
 446                                 }
 447                         } else {
 448                                 return false;
 449                         }
 450                 }
 451
 452                 return [ $parsed, $extractedNamespace ];
 453         }
 454
 455         /**
 456          * Find snippet highlight settings for all users
 457          * @return array Contextlines, contextchars
 458          */
 459         public static function userHighlightPrefs() {
 460                 $contextlines = 2; // Hardcode this. Old defaults sucked. :)
 461                 $contextchars = 75; // same as above.... :P
 462                 return [ $contextlines, $contextchars ];
 463         }
 464
 465         /**
 466          * Create or update the search index record for the given page.
 467          * Title and text should be pre-processed.
 468          * STUB
 469          *
 470          * @param int $id
 471          * @param string $title
 472          * @param string $text
 473          */
 474         function update( $id, $title, $text ) {
 475                 // no-op
 476         }
 477
 478         /**
 479          * Update a search index record's title only.
 480          * Title should be pre-processed.
 481          * STUB
 482          *
 483          * @param int $id
 484          * @param string $title
 485          */
 486         function updateTitle( $id, $title ) {
 487                 // no-op
 488         }
 489
 490         /**
 491          * Delete an indexed page
 492          * Title should be pre-processed.
 493          * STUB
 494          *
 495          * @param int $id Page id that was deleted
 496          * @param string $title Title of page that was deleted
 497          */
 498         function delete( $id, $title ) {
 499                 // no-op
 500         }
 501
 502         /**
 503          * Get the raw text for updating the index from a content object
 504          * Nicer search backends could possibly do something cooler than
 505          * just returning raw text
 506          *
 507          * @todo This isn't ideal, we'd really like to have content-specific handling here
 508          * @param Title $t Title we're indexing
 509          * @param Content|null $c Content of the page to index
 510          * @return string
 511          */
 512         public function getTextFromContent( Title $t, Content $c = null ) {
 513                 return $c ? $c->getTextForSearchIndex() : '';
 514         }
 515
 516         /**
 517          * If an implementation of SearchEngine handles all of its own text processing
 518          * in getTextFromContent() and doesn't require SearchUpdate::updateText()'s
 519          * rather silly handling, it should return true here instead.
 520          *
 521          * @return bool
 522          */
 523         public function textAlreadyUpdatedForIndex() {
 524                 return false;
 525         }
 526
 527         /**
 528          * Makes search simple string if it was namespaced.
 529          * Sets namespaces of the search to namespaces extracted from string.
 530          * @param string $search
 531          * @return string Simplified search string
 532          */
 533         protected function normalizeNamespaces( $search ) {
 534                 $queryAndNs = self::parseNamespacePrefixes( $search, false, true );
 535                 if ( $queryAndNs !== false ) {
 536                         $this->setNamespaces( $queryAndNs[1] );
 537                         return $queryAndNs[0];
 538                 }
 539                 return $search;
 540         }
 541
 542         /**
 543          * Perform an overfetch of completion search results. This allows
 544          * determining if another page of results is available.
 545          *
 546          * @param string $search
 547          * @return SearchSuggestionSet
 548          */
 549         protected function completionSearchBackendOverfetch( $search ) {
 550                 $this->limit++;
 551                 try {
 552                         return $this->completionSearchBackend( $search );
 553                 } finally {
 554                         $this->limit--;
 555                 }
 556         }
 557
 558         /**
 559          * Perform a completion search.
 560          * Does not resolve namespaces and does not check variants.
 561          * Search engine implementations may want to override this function.
 562          * @param string $search
 563          * @return SearchSuggestionSet
 564          */
 565         protected function completionSearchBackend( $search ) {
 566                 $results = [];
 567
 568                 $search = trim( $search );
 569
 570                 if ( !in_array( NS_SPECIAL, $this->namespaces ) && // We do not run hook on Special: search
 571                          !Hooks::run( 'PrefixSearchBackend',
 572                                 [ $this->namespaces, $search, $this->limit, &$results, $this->offset ]
 573                 ) ) {
 574                         // False means hook worked.
 575                         // FIXME: Yes, the API is weird. That's why it is going to be deprecated.
 576
 577                         return SearchSuggestionSet::fromStrings( $results );
 578                 } else {
 579                         // Hook did not do the job, use default simple search
 580                         $results = $this->simplePrefixSearch( $search );
 581                         return SearchSuggestionSet::fromTitles( $results );
 582                 }
 583         }
 584
 585         /**
 586          * Perform a completion search.
 587          * @param string $search
 588          * @return SearchSuggestionSet
 589          */
 590         public function completionSearch( $search ) {
 591                 if ( trim( $search ) === '' ) {
 592                         return SearchSuggestionSet::emptySuggestionSet(); // Return empty result
 593                 }
 594                 $search = $this->normalizeNamespaces( $search );
 595                 $suggestions = $this->completionSearchBackendOverfetch( $search );
 596                 return $this->processCompletionResults( $search, $suggestions );
 597         }
 598
 599         /**
 600          * Perform a completion search with variants.
 601          * @param string $search
 602          * @return SearchSuggestionSet
 603          */
 604         public function completionSearchWithVariants( $search ) {
 605                 if ( trim( $search ) === '' ) {
 606                         return SearchSuggestionSet::emptySuggestionSet(); // Return empty result
 607                 }
 608                 $search = $this->normalizeNamespaces( $search );
 609
 610                 $results = $this->completionSearchBackendOverfetch( $search );
 611                 $fallbackLimit = 1 + $this->limit - $results->getSize();
 612                 if ( $fallbackLimit > 0 ) {
 613                         $fallbackSearches = MediaWikiServices::getInstance()->getContentLanguage()->
 614                                 autoConvertToAllVariants( $search );
 615                         $fallbackSearches = array_diff( array_unique( $fallbackSearches ), [ $search ] );
 616
 617                         foreach ( $fallbackSearches as $fbs ) {
 618                                 $this->setLimitOffset( $fallbackLimit );
 619                                 $fallbackSearchResult = $this->completionSearch( $fbs );
 620                                 $results->appendAll( $fallbackSearchResult );
 621                                 $fallbackLimit -= $fallbackSearchResult->getSize();
 622                                 if ( $fallbackLimit <= 0 ) {
 623                                         break;
 624                                 }
 625                         }
 626                 }
 627                 return $this->processCompletionResults( $search, $results );
 628         }
 629
 630         /**
 631          * Extract titles from completion results
 632          * @param SearchSuggestionSet $completionResults
 633          * @return Title[]
 634          */
 635         public function extractTitles( SearchSuggestionSet $completionResults ) {
 636                 return $completionResults->map( function ( SearchSuggestion $sugg ) {
 637                         return $sugg->getSuggestedTitle();
 638                 } );
 639         }
 640
 641         /**
 642          * Process completion search results.
 643          * Resolves the titles and rescores.
 644          * @param string $search
 645          * @param SearchSuggestionSet $suggestions
 646          * @return SearchSuggestionSet
 647          */
 648         protected function processCompletionResults( $search, SearchSuggestionSet $suggestions ) {
 649                 // We over-fetched to determine pagination. Shrink back down if we have extra results
 650                 // and mark if pagination is possible
 651                 $suggestions->shrink( $this->limit );
 652
 653                 $search = trim( $search );
 654                 // preload the titles with LinkBatch
 655                 $lb = new LinkBatch( $suggestions->map( function ( SearchSuggestion $sugg ) {
 656                         return $sugg->getSuggestedTitle();
 657                 } ) );
 658                 $lb->setCaller( __METHOD__ );
 659                 $lb->execute();
 660
 661                 $diff = $suggestions->filter( function ( SearchSuggestion $sugg ) {
 662                         return $sugg->getSuggestedTitle()->isKnown();
 663                 } );
 664                 if ( $diff > 0 ) {
 665                         MediaWikiServices::getInstance()->getStatsdDataFactory()
 666                                 ->updateCount( 'search.completion.missing', $diff );
 667                 }
 668
 669                 $results = $suggestions->map( function ( SearchSuggestion $sugg ) {
 670                         return $sugg->getSuggestedTitle()->getPrefixedText();
 671                 } );
 672
 673                 if ( $this->offset === 0 ) {
 674                         // Rescore results with an exact title match
 675                         // NOTE: in some cases like cross-namespace redirects
 676                         // (frequently used as shortcuts e.g. WP:WP on huwiki) some
 677                         // backends like Cirrus will return no results. We should still
 678                         // try an exact title match to workaround this limitation
 679                         $rescorer = new SearchExactMatchRescorer();
 680                         $rescoredResults = $rescorer->rescore( $search, $this->namespaces, $results, $this->limit );
 681                 } else {
 682                         // No need to rescore if offset is not 0
 683                         // The exact match must have been returned at position 0
 684                         // if it existed.
 685                         $rescoredResults = $results;
 686                 }
 687
 688                 if ( count( $rescoredResults ) > 0 ) {
 689                         $found = array_search( $rescoredResults[0], $results );
 690                         if ( $found === false ) {
 691                                 // If the first result is not in the previous array it
 692                                 // means that we found a new exact match
 693                                 $exactMatch = SearchSuggestion::fromTitle( 0, Title::newFromText( $rescoredResults[0] ) );
 694                                 $suggestions->prepend( $exactMatch );
 695                                 $suggestions->shrink( $this->limit );
 696                         } else {
 697                                 // if the first result is not the same we need to rescore
 698                                 if ( $found > 0 ) {
 699                                         $suggestions->rescore( $found );
 700                                 }
 701                         }
 702                 }
 703
 704                 return $suggestions;
 705         }
 706
 707         /**
 708          * Simple prefix search for subpages.
 709          * @param string $search
 710          * @return Title[]
 711          */
 712         public function defaultPrefixSearch( $search ) {
 713                 if ( trim( $search ) === '' ) {
 714                         return [];
 715                 }
 716
 717                 $search = $this->normalizeNamespaces( $search );
 718                 return $this->simplePrefixSearch( $search );
 719         }
 720
 721         /**
 722          * Call out to simple search backend.
 723          * Defaults to TitlePrefixSearch.
 724          * @param string $search
 725          * @return Title[]
 726          */
 727         protected function simplePrefixSearch( $search ) {
 728                 // Use default database prefix search
 729                 $backend = new TitlePrefixSearch;
 730                 return $backend->defaultSearchBackend( $this->namespaces, $search, $this->limit, $this->offset );
 731         }
 732
 733         /**
 734          * Make a list of searchable namespaces and their canonical names.
 735          * @deprecated since 1.27; use SearchEngineConfig::searchableNamespaces()
 736          * @return array
 737          */
 738         public static function searchableNamespaces() {
 739                 return MediaWikiServices::getInstance()->getSearchEngineConfig()->searchableNamespaces();
 740         }
 741
 742         /**
 743          * Extract default namespaces to search from the given user's
 744          * settings, returning a list of index numbers.
 745          * @deprecated since 1.27; use SearchEngineConfig::userNamespaces()
 746          * @param user $user
 747          * @return array
 748          */
 749         public static function userNamespaces( $user ) {
 750                 return MediaWikiServices::getInstance()->getSearchEngineConfig()->userNamespaces( $user );
 751         }
 752
 753         /**
 754          * An array of namespaces indexes to be searched by default
 755          * @deprecated since 1.27; use SearchEngineConfig::defaultNamespaces()
 756          * @return array
 757          */
 758         public static function defaultNamespaces() {
 759                 return MediaWikiServices::getInstance()->getSearchEngineConfig()->defaultNamespaces();
 760         }
 761
 762         /**
 763          * Get a list of namespace names useful for showing in tooltips
 764          * and preferences
 765          * @deprecated since 1.27; use SearchEngineConfig::namespacesAsText()
 766          * @param array $namespaces
 767          * @return array
 768          */
 769         public static function namespacesAsText( $namespaces ) {
 770                 return MediaWikiServices::getInstance()->getSearchEngineConfig()->namespacesAsText( $namespaces );
 771         }
 772
 773         /**
 774          * Load up the appropriate search engine class for the currently
 775          * active database backend, and return a configured instance.
 776          * @deprecated since 1.27; Use SearchEngineFactory::create
 777          * @param string $type Type of search backend, if not the default
 778          * @return SearchEngine
 779          */
 780         public static function create( $type = null ) {
 781                 return MediaWikiServices::getInstance()->getSearchEngineFactory()->create( $type );
 782         }
 783
 784         /**
 785          * Return the search engines we support. If only $wgSearchType
 786          * is set, it'll be an array of just that one item.
 787          * @deprecated since 1.27; use SearchEngineConfig::getSearchTypes()
 788          * @return array
 789          */
 790         public static function getSearchTypes() {
 791                 return MediaWikiServices::getInstance()->getSearchEngineConfig()->getSearchTypes();
 792         }
 793
 794         /**
 795          * Get a list of supported profiles.
 796          * Some search engine implementations may expose specific profiles to fine-tune
 797          * its behaviors.
 798          * The profile can be passed as a feature data with setFeatureData( $profileType, $profileName )
 799          * The array returned by this function contains the following keys:
 800          * - name: the profile name to use with setFeatureData
 801          * - desc-message: the i18n description
 802          * - default: set to true if this profile is the default
 803          *
 804          * @since 1.28
 805          * @param string $profileType the type of profiles
 806          * @param User|null $user the user requesting the list of profiles
 807          * @return array|null the list of profiles or null if none available
 808          */
 809         public function getProfiles( $profileType, User $user = null ) {
 810                 return null;
 811         }
 812
 813         /**
 814          * Create a search field definition.
 815          * Specific search engines should override this method to create search fields.
 816          * @param string $name
 817          * @param int $type One of the types in SearchIndexField::INDEX_TYPE_*
 818          * @return SearchIndexField
 819          * @since 1.28
 820          */
 821         public function makeSearchFieldMapping( $name, $type ) {
 822                 return new NullIndexField();
 823         }
 824
 825         /**
 826          * Get fields for search index
 827          * @since 1.28
 828          * @return SearchIndexField[] Index field definitions for all content handlers
 829          */
 830         public function getSearchIndexFields() {
 831                 $models = ContentHandler::getContentModels();
 832                 $fields = [];
 833                 $seenHandlers = new SplObjectStorage();
 834                 foreach ( $models as $model ) {
 835                         try {
 836                                 $handler = ContentHandler::getForModelID( $model );
 837                         }
 838                         catch ( MWUnknownContentModelException $e ) {
 839                                 // If we can find no handler, ignore it
 840                                 continue;
 841                         }
 842                         // Several models can have the same handler, so avoid processing it repeatedly
 843                         if ( $seenHandlers->contains( $handler ) ) {
 844                                 // We already did this one
 845                                 continue;
 846                         }
 847                         $seenHandlers->attach( $handler );
 848                         $handlerFields = $handler->getFieldsForSearchIndex( $this );
 849                         foreach ( $handlerFields as $fieldName => $fieldData ) {
 850                                 if ( empty( $fields[$fieldName] ) ) {
 851                                         $fields[$fieldName] = $fieldData;
 852                                 } else {
 853                                         // TODO: do we allow some clashes with the same type or reject all of them?
 854                                         $mergeDef = $fields[$fieldName]->merge( $fieldData );
 855                                         if ( !$mergeDef ) {
 856                                                 throw new InvalidArgumentException( "Duplicate field $fieldName for model $model" );
 857                                         }
 858                                         $fields[$fieldName] = $mergeDef;
 859                                 }
 860                         }
 861                 }
 862                 // Hook to allow extensions to produce search mapping fields
 863                 Hooks::run( 'SearchIndexFields', [ &$fields, $this ] );
 864                 return $fields;
 865         }
 866
 867         /**
 868          * Augment search results with extra data.
 869          *
 870          * @param SearchResultSet $resultSet
 871          */
 872         public function augmentSearchResults( SearchResultSet $resultSet ) {
 873                 $setAugmentors = [];
 874                 $rowAugmentors = [];
 875                 Hooks::run( "SearchResultsAugment", [ &$setAugmentors, &$rowAugmentors ] );
 876                 if ( !$setAugmentors && !$rowAugmentors ) {
 877                         // We're done here
 878                         return;
 879                 }
 880
 881                 // Convert row augmentors to set augmentor
 882                 foreach ( $rowAugmentors as $name => $row ) {
 883                         if ( isset( $setAugmentors[$name] ) ) {
 884                                 throw new InvalidArgumentException( "Both row and set augmentors are defined for $name" );
 885                         }
 886                         $setAugmentors[$name] = new PerRowAugmentor( $row );
 887                 }
 888
 889                 foreach ( $setAugmentors as $name => $augmentor ) {
 890                         $data = $augmentor->augmentAll( $resultSet );
 891                         if ( $data ) {
 892                                 $resultSet->setAugmentedData( $name, $data );
 893                         }
 894                 }
 895         }
 896 }