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 /**
  29  * Contain a class for special pages
  30  * @ingroup Search
  31  */
  32 class SearchEngine {
  33         var $limit = 10;
  34         var $offset = 0;
  35         var $prefix = '';
  36         var $searchTerms = array();
  37         var $namespaces = array( NS_MAIN );
  38         var $showRedirects = false;
  39
  40         /// Feature values
  41         protected $features = array();
  42
  43         /**
  44          * @var DatabaseBase
  45          */
  46         protected $db;
  47
  48         function __construct( $db = null ) {
  49                 if ( $db ) {
  50                         $this->db = $db;
  51                 } else {
  52                         $this->db = wfGetDB( DB_SLAVE );
  53                 }
  54         }
  55
  56         /**
  57          * Perform a full text search query and return a result set.
  58          * If title searches are not supported or disabled, return null.
  59          * STUB
  60          *
  61          * @param string $term raw search term
  62          * @return SearchResultSet|Status|null
  63          */
  64         function searchText( $term ) {
  65                 return null;
  66         }
  67
  68         /**
  69          * Perform a title-only search query and return a result set.
  70          * If title searches are not supported or disabled, return null.
  71          * STUB
  72          *
  73          * @param string $term raw search term
  74          * @return SearchResultSet|null
  75          */
  76         function searchTitle( $term ) {
  77                 return null;
  78         }
  79
  80         /**
  81          * If this search backend can list/unlist redirects
  82          * @deprecated since 1.18 Call supports( 'list-redirects' );
  83          * @return bool
  84          */
  85         function acceptListRedirects() {
  86                 wfDeprecated( __METHOD__, '1.18' );
  87                 return $this->supports( 'list-redirects' );
  88         }
  89
  90         /**
  91          * @since 1.18
  92          * @param $feature String
  93          * @return Boolean
  94          */
  95         public function supports( $feature ) {
  96                 switch ( $feature ) {
  97                 case 'list-redirects':
  98                         return true;
  99                 case 'title-suffix-filter':
 100                 default:
 101                         return false;
 102                 }
 103         }
 104
 105         /**
 106          * Way to pass custom data for engines
 107          * @since 1.18
 108          * @param $feature String
 109          * @param $data Mixed
 110          * @return bool
 111          */
 112         public function setFeatureData( $feature, $data ) {
 113                 $this->features[$feature] = $data;
 114         }
 115
 116         /**
 117          * When overridden in derived class, performs database-specific conversions
 118          * on text to be used for searching or updating search index.
 119          * Default implementation does nothing (simply returns $string).
 120          *
 121          * @param string $string String to process
 122          * @return string
 123          */
 124         public function normalizeText( $string ) {
 125                 global $wgContLang;
 126
 127                 // Some languages such as Chinese require word segmentation
 128                 return $wgContLang->segmentByWord( $string );
 129         }
 130
 131         /**
 132          * Transform search term in cases when parts of the query came as different GET params (when supported)
 133          * e.g. for prefix queries: search=test&prefix=Main_Page/Archive -> test prefix:Main Page/Archive
 134          */
 135         function transformSearchTerm( $term ) {
 136                 return $term;
 137         }
 138
 139         /**
 140          * If an exact title match can be found, or a very slightly close match,
 141          * return the title. If no match, returns NULL.
 142          *
 143          * @param $searchterm String
 144          * @return Title
 145          */
 146         public static function getNearMatch( $searchterm ) {
 147                 $title = self::getNearMatchInternal( $searchterm );
 148
 149                 wfRunHooks( 'SearchGetNearMatchComplete', array( $searchterm, &$title ) );
 150                 return $title;
 151         }
 152
 153         /**
 154          * Do a near match (see SearchEngine::getNearMatch) and wrap it into a
 155          * SearchResultSet.
 156          *
 157          * @param $searchterm string
 158          * @return SearchResultSet
 159          */
 160         public static function getNearMatchResultSet( $searchterm ) {
 161                 return new SearchNearMatchResultSet( self::getNearMatch( $searchterm ) );
 162         }
 163
 164         /**
 165          * Really find the title match.
 166          * @return null|Title
 167          */
 168         private static function getNearMatchInternal( $searchterm ) {
 169                 global $wgContLang, $wgEnableSearchContributorsByIP;
 170
 171                 $allSearchTerms = array( $searchterm );
 172
 173                 if ( $wgContLang->hasVariants() ) {
 174                         $allSearchTerms = array_merge( $allSearchTerms, $wgContLang->autoConvertToAllVariants( $searchterm ) );
 175                 }
 176
 177                 $titleResult = null;
 178                 if ( !wfRunHooks( 'SearchGetNearMatchBefore', array( $allSearchTerms, &$titleResult ) ) ) {
 179                         return $titleResult;
 180                 }
 181
 182                 foreach ( $allSearchTerms as $term ) {
 183
 184                         # Exact match? No need to look further.
 185                         $title = Title::newFromText( $term );
 186                         if ( is_null( $title ) ) {
 187                                 return null;
 188                         }
 189
 190                         # Try files if searching in the Media: namespace
 191                         if ( $title->getNamespace() == NS_MEDIA ) {
 192                                 $title = Title::makeTitle( NS_FILE, $title->getText() );
 193                         }
 194
 195                         if ( $title->isSpecialPage() || $title->isExternal() || $title->exists() ) {
 196                                 return $title;
 197                         }
 198
 199                         # See if it still otherwise has content is some sane sense
 200                         $page = WikiPage::factory( $title );
 201                         if ( $page->hasViewableContent() ) {
 202                                 return $title;
 203                         }
 204
 205                         if ( !wfRunHooks( 'SearchAfterNoDirectMatch', array( $term, &$title ) ) ) {
 206                                 return $title;
 207                         }
 208
 209                         # Now try all lower case (i.e. first letter capitalized)
 210                         $title = Title::newFromText( $wgContLang->lc( $term ) );
 211                         if ( $title && $title->exists() ) {
 212                                 return $title;
 213                         }
 214
 215                         # Now try capitalized string
 216                         $title = Title::newFromText( $wgContLang->ucwords( $term ) );
 217                         if ( $title && $title->exists() ) {
 218                                 return $title;
 219                         }
 220
 221                         # Now try all upper case
 222                         $title = Title::newFromText( $wgContLang->uc( $term ) );
 223                         if ( $title && $title->exists() ) {
 224                                 return $title;
 225                         }
 226
 227                         # Now try Word-Caps-Breaking-At-Word-Breaks, for hyphenated names etc
 228                         $title = Title::newFromText( $wgContLang->ucwordbreaks( $term ) );
 229                         if ( $title && $title->exists() ) {
 230                                 return $title;
 231                         }
 232
 233                         // Give hooks a chance at better match variants
 234                         $title = null;
 235                         if ( !wfRunHooks( 'SearchGetNearMatch', array( $term, &$title ) ) ) {
 236                                 return $title;
 237                         }
 238                 }
 239
 240                 $title = Title::newFromText( $searchterm );
 241
 242                 # Entering an IP address goes to the contributions page
 243                 if ( $wgEnableSearchContributorsByIP ) {
 244                         if ( ( $title->getNamespace() == NS_USER && User::isIP( $title->getText() ) )
 245                                 || User::isIP( trim( $searchterm ) ) ) {
 246                                 return SpecialPage::getTitleFor( 'Contributions', $title->getDBkey() );
 247                         }
 248                 }
 249
 250                 # Entering a user goes to the user page whether it's there or not
 251                 if ( $title->getNamespace() == NS_USER ) {
 252                         return $title;
 253                 }
 254
 255                 # Go to images that exist even if there's no local page.
 256                 # There may have been a funny upload, or it may be on a shared
 257                 # file repository such as Wikimedia Commons.
 258                 if ( $title->getNamespace() == NS_FILE ) {
 259                         $image = wfFindFile( $title );
 260                         if ( $image ) {
 261                                 return $title;
 262                         }
 263                 }
 264
 265                 # MediaWiki namespace? Page may be "implied" if not customized.
 266                 # Just return it, with caps forced as the message system likes it.
 267                 if ( $title->getNamespace() == NS_MEDIAWIKI ) {
 268                         return Title::makeTitle( NS_MEDIAWIKI, $wgContLang->ucfirst( $title->getText() ) );
 269                 }
 270
 271                 # Quoted term? Try without the quotes...
 272                 $matches = array();
 273                 if ( preg_match( '/^"([^"]+)"$/', $searchterm, $matches ) ) {
 274                         return SearchEngine::getNearMatch( $matches[1] );
 275                 }
 276
 277                 return null;
 278         }
 279
 280         public static function legalSearchChars() {
 281                 return "A-Za-z_'.0-9\\x80-\\xFF\\-";
 282         }
 283
 284         /**
 285          * Set the maximum number of results to return
 286          * and how many to skip before returning the first.
 287          *
 288          * @param $limit Integer
 289          * @param $offset Integer
 290          */
 291         function setLimitOffset( $limit, $offset = 0 ) {
 292                 $this->limit = intval( $limit );
 293                 $this->offset = intval( $offset );
 294         }
 295
 296         /**
 297          * Set which namespaces the search should include.
 298          * Give an array of namespace index numbers.
 299          *
 300          * @param $namespaces Array
 301          */
 302         function setNamespaces( $namespaces ) {
 303                 $this->namespaces = $namespaces;
 304         }
 305
 306         /**
 307          * Parse some common prefixes: all (search everything)
 308          * or namespace names
 309          *
 310          * @param $query String
 311          * @return string
 312          */
 313         function replacePrefixes( $query ) {
 314                 global $wgContLang;
 315
 316                 $parsed = $query;
 317                 if ( strpos( $query, ':' ) === false ) { // nothing to do
 318                         wfRunHooks( 'SearchEngineReplacePrefixesComplete', array( $this, $query, &$parsed ) );
 319                         return $parsed;
 320                 }
 321
 322                 $allkeyword = wfMessage( 'searchall' )->inContentLanguage()->text() . ":";
 323                 if ( strncmp( $query, $allkeyword, strlen( $allkeyword ) ) == 0 ) {
 324                         $this->namespaces = null;
 325                         $parsed = substr( $query, strlen( $allkeyword ) );
 326                 } elseif ( strpos( $query, ':' ) !== false ) {
 327                         $prefix = substr( $query, 0, strpos( $query, ':' ) );
 328                         $index = $wgContLang->getNsIndex( $prefix );
 329                         if ( $index !== false ) {
 330                                 $this->namespaces = array( $index );
 331                                 $parsed = substr( $query, strlen( $prefix ) + 1 );
 332                         }
 333                 }
 334                 if ( trim( $parsed ) == '' ) {
 335                         $parsed = $query; // prefix was the whole query
 336                 }
 337
 338                 wfRunHooks( 'SearchEngineReplacePrefixesComplete', array( $this, $query, &$parsed ) );
 339
 340                 return $parsed;
 341         }
 342
 343         /**
 344          * Make a list of searchable namespaces and their canonical names.
 345          * @return Array
 346          */
 347         public static function searchableNamespaces() {
 348                 global $wgContLang;
 349                 $arr = array();
 350                 foreach ( $wgContLang->getNamespaces() as $ns => $name ) {
 351                         if ( $ns >= NS_MAIN ) {
 352                                 $arr[$ns] = $name;
 353                         }
 354                 }
 355
 356                 wfRunHooks( 'SearchableNamespaces', array( &$arr ) );
 357                 return $arr;
 358         }
 359
 360         /**
 361          * Extract default namespaces to search from the given user's
 362          * settings, returning a list of index numbers.
 363          *
 364          * @param $user User
 365          * @return Array
 366          */
 367         public static function userNamespaces( $user ) {
 368                 global $wgSearchEverythingOnlyLoggedIn;
 369
 370                 $searchableNamespaces = SearchEngine::searchableNamespaces();
 371
 372                 // get search everything preference, that can be set to be read for logged-in users
 373                 // it overrides other options
 374                 if ( !$wgSearchEverythingOnlyLoggedIn || $user->isLoggedIn() ) {
 375                         if ( $user->getOption( 'searcheverything' ) ) {
 376                                 return array_keys( $searchableNamespaces );
 377                         }
 378                 }
 379
 380                 $arr = array();
 381                 foreach ( $searchableNamespaces as $ns => $name ) {
 382                         if ( $user->getOption( 'searchNs' . $ns ) ) {
 383                                 $arr[] = $ns;
 384                         }
 385                 }
 386
 387                 return $arr;
 388         }
 389
 390         /**
 391          * Find snippet highlight settings for all users
 392          *
 393          * @return Array contextlines, contextchars
 394          */
 395         public static function userHighlightPrefs() {
 396                 $contextlines = 2; // Hardcode this. Old defaults sucked. :)
 397                 $contextchars = 75; // same as above.... :P
 398                 return array( $contextlines, $contextchars );
 399         }
 400
 401         /**
 402          * An array of namespaces indexes to be searched by default
 403          *
 404          * @return Array
 405          */
 406         public static function defaultNamespaces() {
 407                 global $wgNamespacesToBeSearchedDefault;
 408
 409                 return array_keys( $wgNamespacesToBeSearchedDefault, true );
 410         }
 411
 412         /**
 413          * Get a list of namespace names useful for showing in tooltips
 414          * and preferences
 415          *
 416          * @param $namespaces Array
 417          * @return array
 418          */
 419         public static function namespacesAsText( $namespaces ) {
 420                 global $wgContLang;
 421
 422                 $formatted = array_map( array( $wgContLang, 'getFormattedNsText' ), $namespaces );
 423                 foreach ( $formatted as $key => $ns ) {
 424                         if ( empty( $ns ) ) {
 425                                 $formatted[$key] = wfMessage( 'blanknamespace' )->text();
 426                         }
 427                 }
 428                 return $formatted;
 429         }
 430
 431         /**
 432          * Return the help namespaces to be shown on Special:Search
 433          *
 434          * @return Array
 435          */
 436         public static function helpNamespaces() {
 437                 global $wgNamespacesToBeSearchedHelp;
 438
 439                 return array_keys( $wgNamespacesToBeSearchedHelp, true );
 440         }
 441
 442         /**
 443          * Return a 'cleaned up' search string
 444          *
 445          * @param $text String
 446          * @return String
 447          */
 448         function filter( $text ) {
 449                 $lc = $this->legalSearchChars();
 450                 return trim( preg_replace( "/[^{$lc}]/", " ", $text ) );
 451         }
 452         /**
 453          * Load up the appropriate search engine class for the currently
 454          * active database backend, and return a configured instance.
 455          *
 456          * @return SearchEngine
 457          */
 458         public static function create() {
 459                 global $wgSearchType;
 460                 $dbr = null;
 461                 if ( $wgSearchType ) {
 462                         $class = $wgSearchType;
 463                 } else {
 464                         $dbr = wfGetDB( DB_SLAVE );
 465                         $class = $dbr->getSearchEngine();
 466                 }
 467                 $search = new $class( $dbr );
 468                 $search->setLimitOffset( 0, 0 );
 469                 return $search;
 470         }
 471
 472         /**
 473          * Create or update the search index record for the given page.
 474          * Title and text should be pre-processed.
 475          * STUB
 476          *
 477          * @param $id Integer
 478          * @param $title String
 479          * @param $text String
 480          */
 481         function update( $id, $title, $text ) {
 482                 // no-op
 483         }
 484
 485         /**
 486          * Update a search index record's title only.
 487          * Title should be pre-processed.
 488          * STUB
 489          *
 490          * @param $id Integer
 491          * @param $title String
 492          */
 493         function updateTitle( $id, $title ) {
 494                 // no-op
 495         }
 496
 497         /**
 498          * Delete an indexed page
 499          * Title should be pre-processed.
 500          * STUB
 501          *
 502          * @param Integer $id Page id that was deleted
 503          * @param String $title Title of page that was deleted
 504          */
 505         function delete( $id, $title ) {
 506                 // no-op
 507         }
 508
 509         /**
 510          * Get OpenSearch suggestion template
 511          *
 512          * @return String
 513          */
 514         public static function getOpenSearchTemplate() {
 515                 global $wgOpenSearchTemplate, $wgCanonicalServer;
 516                 if ( $wgOpenSearchTemplate ) {
 517                         return $wgOpenSearchTemplate;
 518                 } else {
 519                         $ns = implode( '|', SearchEngine::defaultNamespaces() );
 520                         if ( !$ns ) {
 521                                 $ns = "0";
 522                         }
 523                         return $wgCanonicalServer . wfScript( 'api' ) . '?action=opensearch&search={searchTerms}&namespace=' . $ns;
 524                 }
 525         }
 526
 527         /**
 528          * Get the raw text for updating the index from a content object
 529          * Nicer search backends could possibly do something cooler than
 530          * just returning raw text
 531          *
 532          * @todo This isn't ideal, we'd really like to have content-specific handling here
 533          * @param Title $t Title we're indexing
 534          * @param Content $c Content of the page to index
 535          * @return string
 536          */
 537         public function getTextFromContent( Title $t, Content $c = null ) {
 538                 return $c ? $c->getTextForSearchIndex() : '';
 539         }
 540 }
 541
 542 /**
 543  * @ingroup Search
 544  */
 545 class SearchResultSet {
 546         /**
 547          * Fetch an array of regular expression fragments for matching
 548          * the search terms as parsed by this engine in a text extract.
 549          * STUB
 550          *
 551          * @return Array
 552          */
 553         function termMatches() {
 554                 return array();
 555         }
 556
 557         function numRows() {
 558                 return 0;
 559         }
 560
 561         /**
 562          * Return true if results are included in this result set.
 563          * STUB
 564          *
 565          * @return Boolean
 566          */
 567         function hasResults() {
 568                 return false;
 569         }
 570
 571         /**
 572          * Some search modes return a total hit count for the query
 573          * in the entire article database. This may include pages
 574          * in namespaces that would not be matched on the given
 575          * settings.
 576          *
 577          * Return null if no total hits number is supported.
 578          *
 579          * @return Integer
 580          */
 581         function getTotalHits() {
 582                 return null;
 583         }
 584
 585         /**
 586          * Some search modes return a suggested alternate term if there are
 587          * no exact hits. Returns true if there is one on this set.
 588          *
 589          * @return Boolean
 590          */
 591         function hasSuggestion() {
 592                 return false;
 593         }
 594
 595         /**
 596          * @return String: suggested query, null if none
 597          */
 598         function getSuggestionQuery() {
 599                 return null;
 600         }
 601
 602         /**
 603          * @return String: HTML highlighted suggested query, '' if none
 604          */
 605         function getSuggestionSnippet() {
 606                 return '';
 607         }
 608
 609         /**
 610          * Return information about how and from where the results were fetched,
 611          * should be useful for diagnostics and debugging
 612          *
 613          * @return String
 614          */
 615         function getInfo() {
 616                 return null;
 617         }
 618
 619         /**
 620          * Return a result set of hits on other (multiple) wikis associated with this one
 621          *
 622          * @return SearchResultSet
 623          */
 624         function getInterwikiResults() {
 625                 return null;
 626         }
 627
 628         /**
 629          * Check if there are results on other wikis
 630          *
 631          * @return Boolean
 632          */
 633         function hasInterwikiResults() {
 634                 return $this->getInterwikiResults() != null;
 635         }
 636
 637         /**
 638          * Fetches next search result, or false.
 639          * STUB
 640          *
 641          * @return SearchResult
 642          */
 643         function next() {
 644                 return false;
 645         }
 646
 647         /**
 648          * Frees the result set, if applicable.
 649          */
 650         function free() {
 651                 // ...
 652         }
 653 }
 654
 655 /**
 656  * This class is used for different SQL-based search engines shipped with MediaWiki
 657  */
 658 class SqlSearchResultSet extends SearchResultSet {
 659
 660         protected $mResultSet;
 661
 662         function __construct( $resultSet, $terms ) {
 663                 $this->mResultSet = $resultSet;
 664                 $this->mTerms = $terms;
 665         }
 666
 667         function termMatches() {
 668                 return $this->mTerms;
 669         }
 670
 671         function numRows() {
 672                 if ( $this->mResultSet === false ) {
 673                         return false;
 674                 }
 675
 676                 return $this->mResultSet->numRows();
 677         }
 678
 679         function next() {
 680                 if ( $this->mResultSet === false ) {
 681                         return false;
 682                 }
 683
 684                 $row = $this->mResultSet->fetchObject();
 685                 if ( $row === false ) {
 686                         return false;
 687                 }
 688
 689                 return SearchResult::newFromRow( $row );
 690         }
 691
 692         function free() {
 693                 if ( $this->mResultSet === false ) {
 694                         return false;
 695                 }
 696
 697                 $this->mResultSet->free();
 698         }
 699 }
 700
 701 /**
 702  * @ingroup Search
 703  */
 704 class SearchResultTooMany {
 705         # # Some search engines may bail out if too many matches are found
 706 }
 707
 708 /**
 709  * @todo FIXME: This class is horribly factored. It would probably be better to
 710  * have a useful base class to which you pass some standard information, then
 711  * let the fancy self-highlighters extend that.
 712  * @ingroup Search
 713  */
 714 class SearchResult {
 715
 716         /**
 717          * @var Revision
 718          */
 719         var $mRevision = null;
 720         var $mImage = null;
 721
 722         /**
 723          * @var Title
 724          */
 725         var $mTitle;
 726
 727         /**
 728          * @var String
 729          */
 730         var $mText;
 731
 732         /**
 733          * Return a new SearchResult and initializes it with a title.
 734          *
 735          * @param $title Title
 736          * @return SearchResult
 737          */
 738         public static function newFromTitle( $title ) {
 739                 $result = new self();
 740                 $result->initFromTitle( $title );
 741                 return $result;
 742         }
 743         /**
 744          * Return a new SearchResult and initializes it with a row.
 745          *
 746          * @param $row object
 747          * @return SearchResult
 748          */
 749         public static function newFromRow( $row ) {
 750                 $result = new self();
 751                 $result->initFromRow( $row );
 752                 return $result;
 753         }
 754
 755         public function __construct( $row = null ) {
 756                 if ( !is_null( $row ) ) {
 757                         // Backwards compatibility with pre-1.17 callers
 758                         $this->initFromRow( $row );
 759                 }
 760         }
 761
 762         /**
 763          * Initialize from a database row. Makes a Title and passes that to
 764          * initFromTitle.
 765          *
 766          * @param $row object
 767          */
 768         protected function initFromRow( $row ) {
 769                 $this->initFromTitle( Title::makeTitle( $row->page_namespace, $row->page_title ) );
 770         }
 771
 772         /**
 773          * Initialize from a Title and if possible initializes a corresponding
 774          * Revision and File.
 775          *
 776          * @param $title Title
 777          */
 778         protected function initFromTitle( $title ) {
 779                 $this->mTitle = $title;
 780                 if ( !is_null( $this->mTitle ) ) {
 781                         $id = false;
 782                         wfRunHooks( 'SearchResultInitFromTitle', array( $title, &$id ) );
 783                         $this->mRevision = Revision::newFromTitle(
 784                                 $this->mTitle, $id, Revision::READ_NORMAL );
 785                         if ( $this->mTitle->getNamespace() === NS_FILE ) {
 786                                 $this->mImage = wfFindFile( $this->mTitle );
 787                         }
 788                 }
 789         }
 790
 791         /**
 792          * Check if this is result points to an invalid title
 793          *
 794          * @return Boolean
 795          */
 796         function isBrokenTitle() {
 797                 if ( is_null( $this->mTitle ) ) {
 798                         return true;
 799                 }
 800                 return false;
 801         }
 802
 803         /**
 804          * Check if target page is missing, happens when index is out of date
 805          *
 806          * @return Boolean
 807          */
 808         function isMissingRevision() {
 809                 return !$this->mRevision && !$this->mImage;
 810         }
 811
 812         /**
 813          * @return Title
 814          */
 815         function getTitle() {
 816                 return $this->mTitle;
 817         }
 818
 819         /**
 820          * @return float|null if not supported
 821          */
 822         function getScore() {
 823                 return null;
 824         }
 825
 826         /**
 827          * Lazy initialization of article text from DB
 828          */
 829         protected function initText() {
 830                 if ( !isset( $this->mText ) ) {
 831                         if ( $this->mRevision != null ) {
 832                                 $this->mText = SearchEngine::create()
 833                                         ->getTextFromContent( $this->mTitle, $this->mRevision->getContent() );
 834                         } else { // TODO: can we fetch raw wikitext for commons images?
 835                                 $this->mText = '';
 836                         }
 837                 }
 838         }
 839
 840         /**
 841          * @param array $terms terms to highlight
 842          * @return String: highlighted text snippet, null (and not '') if not supported
 843          */
 844         function getTextSnippet( $terms ) {
 845                 global $wgUser, $wgAdvancedSearchHighlighting;
 846                 $this->initText();
 847
 848                 // TODO: make highliter take a content object. Make ContentHandler a factory for SearchHighliter.
 849                 list( $contextlines, $contextchars ) = SearchEngine::userHighlightPrefs( $wgUser );
 850                 $h = new SearchHighlighter();
 851                 if ( $wgAdvancedSearchHighlighting ) {
 852                         return $h->highlightText( $this->mText, $terms, $contextlines, $contextchars );
 853                 } else {
 854                         return $h->highlightSimple( $this->mText, $terms, $contextlines, $contextchars );
 855                 }
 856         }
 857
 858         /**
 859          * @param array $terms terms to highlight
 860          * @return String: highlighted title, '' if not supported
 861          */
 862         function getTitleSnippet( $terms ) {
 863                 return '';
 864         }
 865
 866         /**
 867          * @param array $terms terms to highlight
 868          * @return String: highlighted redirect name (redirect to this page), '' if none or not supported
 869          */
 870         function getRedirectSnippet( $terms ) {
 871                 return '';
 872         }
 873
 874         /**
 875          * @return Title object for the redirect to this page, null if none or not supported
 876          */
 877         function getRedirectTitle() {
 878                 return null;
 879         }
 880
 881         /**
 882          * @return string highlighted relevant section name, null if none or not supported
 883          */
 884         function getSectionSnippet() {
 885                 return '';
 886         }
 887
 888         /**
 889          * @return Title object (pagename+fragment) for the section, null if none or not supported
 890          */
 891         function getSectionTitle() {
 892                 return null;
 893         }
 894
 895         /**
 896          * @return String: timestamp
 897          */
 898         function getTimestamp() {
 899                 if ( $this->mRevision ) {
 900                         return $this->mRevision->getTimestamp();
 901                 } elseif ( $this->mImage ) {
 902                         return $this->mImage->getTimestamp();
 903                 }
 904                 return '';
 905         }
 906
 907         /**
 908          * @return Integer: number of words
 909          */
 910         function getWordCount() {
 911                 $this->initText();
 912                 return str_word_count( $this->mText );
 913         }
 914
 915         /**
 916          * @return Integer: size in bytes
 917          */
 918         function getByteSize() {
 919                 $this->initText();
 920                 return strlen( $this->mText );
 921         }
 922
 923         /**
 924          * @return Boolean if hit has related articles
 925          */
 926         function hasRelated() {
 927                 return false;
 928         }
 929
 930         /**
 931          * @return String: interwiki prefix of the title (return iw even if title is broken)
 932          */
 933         function getInterwikiPrefix() {
 934                 return '';
 935         }
 936 }
 937 /**
 938  * A SearchResultSet wrapper for SearchEngine::getNearMatch
 939  */
 940 class SearchNearMatchResultSet extends SearchResultSet {
 941         private $fetched = false;
 942         /**
 943          * @param $match mixed Title if matched, else null
 944          */
 945         public function __construct( $match ) {
 946                 $this->result = $match;
 947         }
 948         public function hasResult() {
 949                 return (bool)$this->result;
 950         }
 951         public function numRows() {
 952                 return $this->hasResults() ? 1 : 0;
 953         }
 954         public function next() {
 955                 if ( $this->fetched || !$this->result ) {
 956                         return false;
 957                 }
 958                 $this->fetched = true;
 959                 return SearchResult::newFromTitle( $this->result );
 960         }
 961 }
 962
 963 /**
 964  * Highlight bits of wikitext
 965  *
 966  * @ingroup Search
 967  */
 968 class SearchHighlighter {
 969         var $mCleanWikitext = true;
 970
 971         function __construct( $cleanupWikitext = true ) {
 972                 $this->mCleanWikitext = $cleanupWikitext;
 973         }
 974
 975         /**
 976          * Default implementation of wikitext highlighting
 977          *
 978          * @param $text String
 979          * @param array $terms terms to highlight (unescaped)
 980          * @param $contextlines Integer
 981          * @param $contextchars Integer
 982          * @return String
 983          */
 984         public function highlightText( $text, $terms, $contextlines, $contextchars ) {
 985                 global $wgContLang;
 986                 global $wgSearchHighlightBoundaries;
 987                 $fname = __METHOD__;
 988
 989                 if ( $text == '' ) {
 990                         return '';
 991                 }
 992
 993                 // spli text into text + templates/links/tables
 994                 $spat = "/(\\{\\{)|(\\[\\[[^\\]:]+:)|(\n\\{\\|)";
 995                 // first capture group is for detecting nested templates/links/tables/references
 996                 $endPatterns = array(
 997                         1 => '/(\{\{)|(\}\})/', // template
 998                         2 => '/(\[\[)|(\]\])/', // image
 999                         3 => "/(\n\\{\\|)|(\n\\|\\})/" ); // table
1000
1001                 // @todo FIXME: This should prolly be a hook or something
1002                 if ( function_exists( 'wfCite' ) ) {
1003                         $spat .= '|(<ref>)'; // references via cite extension
1004                         $endPatterns[4] = '/(<ref>)|(<\/ref>)/';
1005                 }
1006                 $spat .= '/';
1007                 $textExt = array(); // text extracts
1008                 $otherExt = array(); // other extracts
1009                 wfProfileIn( "$fname-split" );
1010                 $start = 0;
1011                 $textLen = strlen( $text );
1012                 $count = 0; // sequence number to maintain ordering
1013                 while ( $start < $textLen ) {
1014                         // find start of template/image/table
1015                         if ( preg_match( $spat, $text, $matches, PREG_OFFSET_CAPTURE, $start ) ) {
1016                                 $epat = '';
1017                                 foreach ( $matches as $key => $val ) {
1018                                         if ( $key > 0 && $val[1] != - 1 ) {
1019                                                 if ( $key == 2 ) {
1020                                                         // see if this is an image link
1021                                                         $ns = substr( $val[0], 2, - 1 );
1022                                                         if ( $wgContLang->getNsIndex( $ns ) != NS_FILE ) {
1023                                                                 break;
1024                                                         }
1025
1026                                                 }
1027                                                 $epat = $endPatterns[$key];
1028                                                 $this->splitAndAdd( $textExt, $count, substr( $text, $start, $val[1] - $start ) );
1029                                                 $start = $val[1];
1030                                                 break;
1031                                         }
1032                                 }
1033                                 if ( $epat ) {
1034                                         // find end (and detect any nested elements)
1035                                         $level = 0;
1036                                         $offset = $start + 1;
1037                                         $found = false;
1038                                         while ( preg_match( $epat, $text, $endMatches, PREG_OFFSET_CAPTURE, $offset ) ) {
1039                                                 if ( array_key_exists( 2, $endMatches ) ) {
1040                                                         // found end
1041                                                         if ( $level == 0 ) {
1042                                                                 $len = strlen( $endMatches[2][0] );
1043                                                                 $off = $endMatches[2][1];
1044                                                                 $this->splitAndAdd( $otherExt, $count,
1045                                                                         substr( $text, $start, $off + $len - $start ) );
1046                                                                 $start = $off + $len;
1047                                                                 $found = true;
1048                                                                 break;
1049                                                         } else {
1050                                                                 // end of nested element
1051                                                                 $level -= 1;
1052                                                         }
1053                                                 } else {
1054                                                         // nested
1055                                                         $level += 1;
1056                                                 }
1057                                                 $offset = $endMatches[0][1] + strlen( $endMatches[0][0] );
1058                                         }
1059                                         if ( ! $found ) {
1060                                                 // couldn't find appropriate closing tag, skip
1061                                                 $this->splitAndAdd( $textExt, $count, substr( $text, $start, strlen( $matches[0][0] ) ) );
1062                                                 $start += strlen( $matches[0][0] );
1063                                         }
1064                                         continue;
1065                                 }
1066                         }
1067                         // else: add as text extract
1068                         $this->splitAndAdd( $textExt, $count, substr( $text, $start ) );
1069                         break;
1070                 }
1071
1072                 $all = $textExt + $otherExt; // these have disjunct key sets
1073
1074                 wfProfileOut( "$fname-split" );
1075
1076                 // prepare regexps
1077                 foreach ( $terms as $index => $term ) {
1078                         // manually do upper/lowercase stuff for utf-8 since PHP won't do it
1079                         if ( preg_match( '/[\x80-\xff]/', $term ) ) {
1080                                 $terms[$index] = preg_replace_callback( '/./us', array( $this, 'caseCallback' ), $terms[$index] );
1081                         } else {
1082                                 $terms[$index] = $term;
1083                         }
1084                 }
1085                 $anyterm = implode( '|', $terms );
1086                 $phrase = implode( "$wgSearchHighlightBoundaries+", $terms );
1087
1088                 // @todo FIXME: A hack to scale contextchars, a correct solution
1089                 // would be to have contextchars actually be char and not byte
1090                 // length, and do proper utf-8 substrings and lengths everywhere,
1091                 // but PHP is making that very hard and unclean to implement :(
1092                 $scale = strlen( $anyterm ) / mb_strlen( $anyterm );
1093                 $contextchars = intval( $contextchars * $scale );
1094
1095                 $patPre = "(^|$wgSearchHighlightBoundaries)";
1096                 $patPost = "($wgSearchHighlightBoundaries|$)";
1097
1098                 $pat1 = "/(" . $phrase . ")/ui";
1099                 $pat2 = "/$patPre(" . $anyterm . ")$patPost/ui";
1100
1101                 wfProfileIn( "$fname-extract" );
1102
1103                 $left = $contextlines;
1104
1105                 $snippets = array();
1106                 $offsets = array();
1107
1108                 // show beginning only if it contains all words
1109                 $first = 0;
1110                 $firstText = '';
1111                 foreach ( $textExt as $index => $line ) {
1112                         if ( strlen( $line ) > 0 && $line[0] != ';' && $line[0] != ':' ) {
1113                                 $firstText = $this->extract( $line, 0, $contextchars * $contextlines );
1114                                 $first = $index;
1115                                 break;
1116                         }
1117                 }
1118                 if ( $firstText ) {
1119                         $succ = true;
1120                         // check if first text contains all terms
1121                         foreach ( $terms as $term ) {
1122                                 if ( ! preg_match( "/$patPre" . $term . "$patPost/ui", $firstText ) ) {
1123                                         $succ = false;
1124                                         break;
1125                                 }
1126                         }
1127                         if ( $succ ) {
1128                                 $snippets[$first] = $firstText;
1129                                 $offsets[$first] = 0;
1130                         }
1131                 }
1132                 if ( ! $snippets ) {
1133                         // match whole query on text
1134                         $this->process( $pat1, $textExt, $left, $contextchars, $snippets, $offsets );
1135                         // match whole query on templates/tables/images
1136                         $this->process( $pat1, $otherExt, $left, $contextchars, $snippets, $offsets );
1137                         // match any words on text
1138                         $this->process( $pat2, $textExt, $left, $contextchars, $snippets, $offsets );
1139                         // match any words on templates/tables/images
1140                         $this->process( $pat2, $otherExt, $left, $contextchars, $snippets, $offsets );
1141
1142                         ksort( $snippets );
1143                 }
1144
1145                 // add extra chars to each snippet to make snippets constant size
1146                 $extended = array();
1147                 if ( count( $snippets ) == 0 ) {
1148                         // couldn't find the target words, just show beginning of article
1149                         if ( array_key_exists( $first, $all ) ) {
1150                                 $targetchars = $contextchars * $contextlines;
1151                                 $snippets[$first] = '';
1152                                 $offsets[$first] = 0;
1153                         }
1154                 } else {
1155                         // if begin of the article contains the whole phrase, show only that !!
1156                         if ( array_key_exists( $first, $snippets ) && preg_match( $pat1, $snippets[$first] )
1157                                 && $offsets[$first] < $contextchars * 2 ) {
1158                                 $snippets = array( $first => $snippets[$first] );
1159                         }
1160
1161                         // calc by how much to extend existing snippets
1162                         $targetchars = intval( ( $contextchars * $contextlines ) / count ( $snippets ) );
1163                 }
1164
1165                 foreach ( $snippets as $index => $line ) {
1166                         $extended[$index] = $line;
1167                         $len = strlen( $line );
1168                         if ( $len < $targetchars - 20 ) {
1169                                 // complete this line
1170                                 if ( $len < strlen( $all[$index] ) ) {
1171                                         $extended[$index] = $this->extract( $all[$index], $offsets[$index], $offsets[$index] + $targetchars, $offsets[$index] );
1172                                         $len = strlen( $extended[$index] );
1173                                 }
1174
1175                                 // add more lines
1176                                 $add = $index + 1;
1177                                 while ( $len < $targetchars - 20
1178                                                 && array_key_exists( $add, $all )
1179                                                 && !array_key_exists( $add, $snippets ) ) {
1180                                         $offsets[$add] = 0;
1181                                         $tt = "\n" . $this->extract( $all[$add], 0, $targetchars - $len, $offsets[$add] );
1182                                         $extended[$add] = $tt;
1183                                         $len += strlen( $tt );
1184                                         $add++;
1185                                 }
1186                         }
1187                 }
1188
1189                 // $snippets = array_map( 'htmlspecialchars', $extended );
1190                 $snippets = $extended;
1191                 $last = - 1;
1192                 $extract = '';
1193                 foreach ( $snippets as $index => $line ) {
1194                         if ( $last == - 1 ) {
1195                                 $extract .= $line; // first line
1196                         } elseif ( $last + 1 == $index && $offsets[$last] + strlen( $snippets[$last] ) >= strlen( $all[$last] ) ) {
1197                                 $extract .= " " . $line; // continous lines
1198                         } else {
1199                                 $extract .= '<b> ... </b>' . $line;
1200                         }
1201
1202                         $last = $index;
1203                 }
1204                 if ( $extract ) {
1205                         $extract .= '<b> ... </b>';
1206                 }
1207
1208                 $processed = array();
1209                 foreach ( $terms as $term ) {
1210                         if ( ! isset( $processed[$term] ) ) {
1211                                 $pat3 = "/$patPre(" . $term . ")$patPost/ui"; // highlight word
1212                                 $extract = preg_replace( $pat3,
1213                                         "\\1<span class='searchmatch'>\\2</span>\\3", $extract );
1214                                 $processed[$term] = true;
1215                         }
1216                 }
1217
1218                 wfProfileOut( "$fname-extract" );
1219
1220                 return $extract;
1221         }
1222
1223         /**
1224          * Split text into lines and add it to extracts array
1225          *
1226          * @param array $extracts index -> $line
1227          * @param $count Integer
1228          * @param $text String
1229          */
1230         function splitAndAdd( &$extracts, &$count, $text ) {
1231                 $split = explode( "\n", $this->mCleanWikitext ? $this->removeWiki( $text ) : $text );
1232                 foreach ( $split as $line ) {
1233                         $tt = trim( $line );
1234                         if ( $tt ) {
1235                                 $extracts[$count++] = $tt;
1236                         }
1237                 }
1238         }
1239
1240         /**
1241          * Do manual case conversion for non-ascii chars
1242          *
1243          * @param $matches Array
1244          * @return string
1245          */
1246         function caseCallback( $matches ) {
1247                 global $wgContLang;
1248                 if ( strlen( $matches[0] ) > 1 ) {
1249                         return '[' . $wgContLang->lc( $matches[0] ) . $wgContLang->uc( $matches[0] ) . ']';
1250                 } else {
1251                         return $matches[0];
1252                 }
1253         }
1254
1255         /**
1256          * Extract part of the text from start to end, but by
1257          * not chopping up words
1258          * @param $text String
1259          * @param $start Integer
1260          * @param $end Integer
1261          * @param $posStart Integer: (out) actual start position
1262          * @param $posEnd Integer: (out) actual end position
1263          * @return String
1264          */
1265         function extract( $text, $start, $end, &$posStart = null, &$posEnd = null ) {
1266                 if ( $start != 0 ) {
1267                         $start = $this->position( $text, $start, 1 );
1268                 }
1269                 if ( $end >= strlen( $text ) ) {
1270                         $end = strlen( $text );
1271                 } else {
1272                         $end = $this->position( $text, $end );
1273                 }
1274
1275                 if ( !is_null( $posStart ) ) {
1276                         $posStart = $start;
1277                 }
1278                 if ( !is_null( $posEnd ) ) {
1279                         $posEnd = $end;
1280                 }
1281
1282                 if ( $end > $start ) {
1283                         return substr( $text, $start, $end - $start );
1284                 } else {
1285                         return '';
1286                 }
1287         }
1288
1289         /**
1290          * Find a nonletter near a point (index) in the text
1291          *
1292          * @param $text String
1293          * @param $point Integer
1294          * @param $offset Integer: offset to found index
1295          * @return Integer: nearest nonletter index, or beginning of utf8 char if none
1296          */
1297         function position( $text, $point, $offset = 0 ) {
1298                 $tolerance = 10;
1299                 $s = max( 0, $point - $tolerance );
1300                 $l = min( strlen( $text ), $point + $tolerance ) - $s;
1301                 $m = array();
1302                 if ( preg_match( '/[ ,.!?~!@#$%^&*\(\)+=\-\\\|\[\]"\'<>]/', substr( $text, $s, $l ), $m, PREG_OFFSET_CAPTURE ) ) {
1303                         return $m[0][1] + $s + $offset;
1304                 } else {
1305                         // check if point is on a valid first UTF8 char
1306                         $char = ord( $text[$point] );
1307                         while ( $char >= 0x80 && $char < 0xc0 ) {
1308                                 // skip trailing bytes
1309                                 $point++;
1310                                 if ( $point >= strlen( $text ) ) {
1311                                         return strlen( $text );
1312                                 }
1313                                 $char = ord( $text[$point] );
1314                         }
1315                         return $point;
1316
1317                 }
1318         }
1319
1320         /**
1321          * Search extracts for a pattern, and return snippets
1322          *
1323          * @param string $pattern regexp for matching lines
1324          * @param array $extracts extracts to search
1325          * @param $linesleft Integer: number of extracts to make
1326          * @param $contextchars Integer: length of snippet
1327          * @param array $out map for highlighted snippets
1328          * @param array $offsets map of starting points of snippets
1329          * @protected
1330          */
1331         function process( $pattern, $extracts, &$linesleft, &$contextchars, &$out, &$offsets ) {
1332                 if ( $linesleft == 0 ) {
1333                         return; // nothing to do
1334                 }
1335                 foreach ( $extracts as $index => $line ) {
1336                         if ( array_key_exists( $index, $out ) ) {
1337                                 continue; // this line already highlighted
1338                         }
1339
1340                         $m = array();
1341                         if ( !preg_match( $pattern, $line, $m, PREG_OFFSET_CAPTURE ) ) {
1342                                 continue;
1343                         }
1344
1345                         $offset = $m[0][1];
1346                         $len = strlen( $m[0][0] );
1347                         if ( $offset + $len < $contextchars ) {
1348                                 $begin = 0;
1349                         } elseif ( $len > $contextchars ) {
1350                                 $begin = $offset;
1351                         } else {
1352                                 $begin = $offset + intval( ( $len - $contextchars ) / 2 );
1353                         }
1354
1355                         $end = $begin + $contextchars;
1356
1357                         $posBegin = $begin;
1358                         // basic snippet from this line
1359                         $out[$index] = $this->extract( $line, $begin, $end, $posBegin );
1360                         $offsets[$index] = $posBegin;
1361                         $linesleft--;
1362                         if ( $linesleft == 0 ) {
1363                                 return;
1364                         }
1365                 }
1366         }
1367
1368         /**
1369          * Basic wikitext removal
1370          * @protected
1371          * @return mixed
1372          */
1373         function removeWiki( $text ) {
1374                 $fname = __METHOD__;
1375                 wfProfileIn( $fname );
1376
1377                 // $text = preg_replace( "/'{2,5}/", "", $text );
1378                 // $text = preg_replace( "/\[[a-z]+:\/\/[^ ]+ ([^]]+)\]/", "\\2", $text );
1379                 // $text = preg_replace( "/\[\[([^]|]+)\]\]/", "\\1", $text );
1380                 // $text = preg_replace( "/\[\[([^]]+\|)?([^|]]+)\]\]/", "\\2", $text );
1381                 // $text = preg_replace( "/\\{\\|(.*?)\\|\\}/", "", $text );
1382                 // $text = preg_replace( "/\\[\\[[A-Za-z_-]+:([^|]+?)\\]\\]/", "", $text );
1383                 $text = preg_replace( "/\\{\\{([^|]+?)\\}\\}/", "", $text );
1384                 $text = preg_replace( "/\\{\\{([^|]+\\|)(.*?)\\}\\}/", "\\2", $text );
1385                 $text = preg_replace( "/\\[\\[([^|]+?)\\]\\]/", "\\1", $text );
1386                 $text = preg_replace_callback( "/\\[\\[([^|]+\\|)(.*?)\\]\\]/", array( $this, 'linkReplace' ), $text );
1387                 // $text = preg_replace("/\\[\\[([^|]+\\|)(.*?)\\]\\]/", "\\2", $text);
1388                 $text = preg_replace( "/<\/?[^>]+>/", "", $text );
1389                 $text = preg_replace( "/'''''/", "", $text );
1390                 $text = preg_replace( "/('''|<\/?[iIuUbB]>)/", "", $text );
1391                 $text = preg_replace( "/''/", "", $text );
1392
1393                 wfProfileOut( $fname );
1394                 return $text;
1395         }
1396
1397         /**
1398          * callback to replace [[target|caption]] kind of links, if
1399          * the target is category or image, leave it
1400          *
1401          * @param $matches Array
1402          */
1403         function linkReplace( $matches ) {
1404                 $colon = strpos( $matches[1], ':' );
1405                 if ( $colon === false ) {
1406                         return $matches[2]; // replace with caption
1407                 }
1408                 global $wgContLang;
1409                 $ns = substr( $matches[1], 0, $colon );
1410                 $index = $wgContLang->getNsIndex( $ns );
1411                 if ( $index !== false && ( $index == NS_FILE || $index == NS_CATEGORY ) ) {
1412                         return $matches[0]; // return the whole thing
1413                 } else {
1414                         return $matches[2];
1415                 }
1416         }
1417
1418         /**
1419          * Simple & fast snippet extraction, but gives completely unrelevant
1420          * snippets
1421          *
1422          * @param $text String
1423          * @param $terms Array
1424          * @param $contextlines Integer
1425          * @param $contextchars Integer
1426          * @return String
1427          */
1428         public function highlightSimple( $text, $terms, $contextlines, $contextchars ) {
1429                 global $wgContLang;
1430                 $fname = __METHOD__;
1431
1432                 $lines = explode( "\n", $text );
1433
1434                 $terms = implode( '|', $terms );
1435                 $max = intval( $contextchars ) + 1;
1436                 $pat1 = "/(.*)($terms)(.{0,$max})/i";
1437
1438                 $lineno = 0;
1439
1440                 $extract = "";
1441                 wfProfileIn( "$fname-extract" );
1442                 foreach ( $lines as $line ) {
1443                         if ( 0 == $contextlines ) {
1444                                 break;
1445                         }
1446                         ++$lineno;
1447                         $m = array();
1448                         if ( ! preg_match( $pat1, $line, $m ) ) {
1449                                 continue;
1450                         }
1451                         --$contextlines;
1452                         // truncate function changes ... to relevant i18n message.
1453                         $pre = $wgContLang->truncate( $m[1], - $contextchars, '...', false );
1454
1455                         if ( count( $m ) < 3 ) {
1456                                 $post = '';
1457                         } else {
1458                                 $post = $wgContLang->truncate( $m[3], $contextchars, '...', false );
1459                         }
1460
1461                         $found = $m[2];
1462
1463                         $line = htmlspecialchars( $pre . $found . $post );
1464                         $pat2 = '/(' . $terms . ")/i";
1465                         $line = preg_replace( $pat2, "<span class='searchmatch'>\\1</span>", $line );
1466
1467                         $extract .= "${line}\n";
1468                 }
1469                 wfProfileOut( "$fname-extract" );
1470
1471                 return $extract;
1472         }
1473
1474 }
1475
1476 /**
1477  * Dummy class to be used when non-supported Database engine is present.
1478  * @todo FIXME: Dummy class should probably try something at least mildly useful,
1479  * such as a LIKE search through titles.
1480  * @ingroup Search
1481  */
1482 class SearchEngineDummy extends SearchEngine {
1483         // no-op
1484 }