Uh, also I shouldn't introduce syntax errors while fixing regressions.
[lhc/web/wiklou.git] / includes / SearchEngine.php
index 00cb185..916e1fd 100644 (file)
@@ -1,7 +1,14 @@
 <?php
+/**
+ * @defgroup Search Search
+ *
+ * @file
+ * @ingroup Search
+ */
+
 /**
  * Contain a class for special pages
- * @addtogroup Search
+ * @ingroup Search
  */
 class SearchEngine {
        var $limit = 10;
@@ -59,50 +66,38 @@ class SearchEngine {
                        if (is_null($title))
                                return NULL;
 
-                       if ( $title->getNamespace() == NS_SPECIAL || $title->exists() ) {
+                       if ( $title->getNamespace() == NS_SPECIAL || $title->isExternal() 
+                            || $title->exists() ) {
                                return $title;
                        }
 
                        # Now try all lower case (i.e. first letter capitalized)
                        #
                        $title = Title::newFromText( $wgContLang->lc( $term ) );
-                       if ( $title->exists() ) {
+                       if ( $title && $title->exists() ) {
                                return $title;
                        }
 
                        # Now try capitalized string
                        #
                        $title = Title::newFromText( $wgContLang->ucwords( $term ) );
-                       if ( $title->exists() ) {
+                       if ( $title && $title->exists() ) {
                                return $title;
                        }
 
                        # Now try all upper case
                        #
                        $title = Title::newFromText( $wgContLang->uc( $term ) );
-                       if ( $title->exists() ) {
+                       if ( $title && $title->exists() ) {
                                return $title;
                        }
 
                        # Now try Word-Caps-Breaking-At-Word-Breaks, for hyphenated names etc
                        $title = Title::newFromText( $wgContLang->ucwordbreaks($term) );
-                       if ( $title->exists() ) {
+                       if ( $title && $title->exists() ) {
                                return $title;
                        }
 
-                       global $wgCapitalLinks, $wgContLang;
-                       if( !$wgCapitalLinks ) {
-                               // Catch differs-by-first-letter-case-only
-                               $title = Title::newFromText( $wgContLang->ucfirst( $term ) );
-                               if ( $title->exists() ) {
-                                       return $title;
-                               }
-                               $title = Title::newFromText( $wgContLang->lcfirst( $term ) );
-                               if ( $title->exists() ) {
-                                       return $title;
-                               }
-                       }
-
                        // Give hooks a chance at better match variants
                        $title = null;
                        if( !wfRunHooks( 'SearchGetNearMatch', array( $term, &$title ) ) ) {
@@ -190,7 +185,7 @@ class SearchEngine {
                        return $query; // nothing to do
 
                $parsed = $query;
-               $allkeyword = wfMsg('searchall').":";
+               $allkeyword = wfMsgForContent('searchall').":";
                if( strncmp($query, $allkeyword, strlen($allkeyword)) == 0 ){
                        $this->namespaces = null;
                        $parsed = substr($query,strlen($allkeyword));
@@ -250,8 +245,9 @@ class SearchEngine {
         */
        public static function userHighlightPrefs( &$user ){
                //$contextlines = $user->getOption( 'contextlines',  5 );
+               //$contextchars = $user->getOption( 'contextchars', 50 );
                $contextlines = 2; // Hardcode this. Old defaults sucked. :)
-               $contextchars = $user->getOption( 'contextchars', 50 );
+               $contextchars = 75; // same as above.... :P
                return array($contextlines, $contextchars);
        }
        
@@ -281,6 +277,8 @@ class SearchEngine {
         * Load up the appropriate search engine class for the currently
         * active database backend, and return a configured instance.
         *
+        * @fixme Ask the database class for his default search class
+        * instead of knowing about every backend here.
         * @return SearchEngine
         */
        public static function create() {
@@ -358,9 +356,8 @@ class SearchEngine {
        }
 }
 
-
 /**
- * @addtogroup Search
+ * @ingroup Search
  */
 class SearchResultSet {
        /**
@@ -478,7 +475,7 @@ class SearchResultSet {
 
 
 /**
- * @addtogroup Search
+ * @ingroup Search
  */
 class SearchResultTooMany {
        ## Some search engines may bail out if too many matches are found
@@ -486,9 +483,13 @@ class SearchResultTooMany {
 
 
 /**
- * @addtogroup Search
+ * @fixme This class is horribly factored. It would probably be better to have
+ * a useful base class to which you pass some standard information, then let
+ * the fancy self-highlighters extend that.
+ * @ingroup Search
  */
 class SearchResult {
+       var $mRevision = null;
 
        function SearchResult( $row ) {
                $this->mTitle = Title::makeTitle( $row->page_namespace, $row->page_title );
@@ -543,71 +544,20 @@ class SearchResult {
                        $this->mText = $this->mRevision->getText();
                }
        }
-
+       
        /**
         * @param array $terms terms to highlight
         * @return string highlighted text snippet, null (and not '') if not supported 
         */
        function getTextSnippet($terms){
-               global $wgUser;
+               global $wgUser, $wgAdvancedSearchHighlighting;
                $this->initText();
                list($contextlines,$contextchars) = SearchEngine::userHighlightPrefs($wgUser);
-               return $this->extractText( $this->mText, $terms, $contextlines, $contextchars);                 
-       }
-       
-       /**
-        * Default implementation of snippet extraction
-        *
-        * @param string $text
-        * @param array $terms
-        * @param int $contextlines
-        * @param int $contextchars
-        * @return string
-        */
-       protected function extractText( $text, $terms, $contextlines, $contextchars ) {
-               global $wgLang, $wgContLang;
-               $fname = __METHOD__;
-       
-               $lines = explode( "\n", $text );
-               
-               $terms = implode( '|', $terms );
-               $max = intval( $contextchars ) + 1;
-               $pat1 = "/(.*)($terms)(.{0,$max})/i";
-
-               $lineno = 0;
-
-               $extract = "";
-               wfProfileIn( "$fname-extract" );
-               foreach ( $lines as $line ) {
-                       if ( 0 == $contextlines ) {
-                               break;
-                       }
-                       ++$lineno;
-                       $m = array();
-                       if ( ! preg_match( $pat1, $line, $m ) ) {
-                               continue;
-                       }
-                       --$contextlines;
-                       $pre = $wgContLang->truncate( $m[1], -$contextchars, ' ... ' );
-
-                       if ( count( $m ) < 3 ) {
-                               $post = '';
-                       } else {
-                               $post = $wgContLang->truncate( $m[3], $contextchars, ' ... ' );
-                       }
-
-                       $found = $m[2];
-
-                       $line = htmlspecialchars( $pre . $found . $post );
-                       $pat2 = '/(' . $terms . ")/i";
-                       $line = preg_replace( $pat2,
-                         "<span class='searchmatch'>\\1</span>", $line );
-
-                       $extract .= "${line}\n";
-               }
-               wfProfileOut( "$fname-extract" );
-               
-               return $extract;
+               $h = new SearchHighlighter();
+               if( $wgAdvancedSearchHighlighting )
+                       return $h->highlightText( $this->mText, $terms, $contextlines, $contextchars );
+               else
+                       return $h->highlightSimple( $this->mText, $terms, $contextlines, $contextchars );
        }
        
        /**
@@ -686,16 +636,506 @@ class SearchResult {
 }
 
 /**
- * @addtogroup Search
+ * Highlight bits of wikitext
+ * 
+ * @ingroup Search
  */
-class SearchEngineDummy {
-       function search( $term ) {
-               return null;
+class SearchHighlighter {      
+       var $mCleanWikitext = true;
+       
+       function SearchHighlighter($cleanupWikitext = true){
+               $this->mCleanWikitext = $cleanupWikitext;
+       }
+       
+       /**
+        * Default implementation of wikitext highlighting
+        *
+        * @param string $text
+        * @param array $terms Terms to highlight (unescaped)
+        * @param int $contextlines
+        * @param int $contextchars
+        * @return string
+        */
+       public function highlightText( $text, $terms, $contextlines, $contextchars ) {
+               global $wgLang, $wgContLang;
+               global $wgSearchHighlightBoundaries;
+               $fname = __METHOD__;
+               
+               if($text == '')
+                       return '';
+                               
+               // spli text into text + templates/links/tables
+               $spat = "/(\\{\\{)|(\\[\\[[^\\]:]+:)|(\n\\{\\|)";
+               // first capture group is for detecting nested templates/links/tables/references
+               $endPatterns = array(
+                       1 => '/(\{\{)|(\}\})/', // template
+                       2 => '/(\[\[)|(\]\])/', // image
+                       3 => "/(\n\\{\\|)|(\n\\|\\})/"); // table
+                        
+               // FIXME: this should prolly be a hook or something
+               if(function_exists('wfCite')){
+                       $spat .= '|(<ref>)'; // references via cite extension
+                       $endPatterns[4] = '/(<ref>)|(<\/ref>)/';
+               }
+               $spat .= '/';
+               $textExt = array(); // text extracts
+               $otherExt = array();  // other extracts
+               wfProfileIn( "$fname-split" );
+               $start = 0;
+               $textLen = strlen($text);
+               $count = 0; // sequence number to maintain ordering
+               while( $start < $textLen ){
+                       // find start of template/image/table
+                       if( preg_match( $spat, $text, $matches, PREG_OFFSET_CAPTURE, $start ) ){
+                               $epat = '';     
+                               foreach($matches as $key => $val){
+                                       if($key > 0 && $val[1] != -1){
+                                               if($key == 2){
+                                                       // see if this is an image link
+                                                       $ns = substr($val[0],2,-1);
+                                                       if( $wgContLang->getNsIndex($ns) != NS_IMAGE )
+                                                               break;
+                                                       
+                                               }
+                                               $epat = $endPatterns[$key];
+                                               $this->splitAndAdd( $textExt, $count, substr( $text, $start, $val[1] - $start ) );                                              
+                                               $start = $val[1];
+                                               break;
+                                       }
+                               }
+                               if( $epat ){
+                                       // find end (and detect any nested elements)
+                                       $level = 0; 
+                                       $offset = $start + 1;
+                                       $found = false;
+                                       while( preg_match( $epat, $text, $endMatches, PREG_OFFSET_CAPTURE, $offset ) ){
+                                               if( array_key_exists(2,$endMatches) ){
+                                                       // found end
+                                                       if($level == 0){
+                                                               $len = strlen($endMatches[2][0]);
+                                                               $off = $endMatches[2][1];
+                                                               $this->splitAndAdd( $otherExt, $count, 
+                                                                       substr( $text, $start, $off + $len  - $start ) );
+                                                               $start = $off + $len;
+                                                               $found = true;
+                                                               break;
+                                                       } else{
+                                                               // end of nested element
+                                                               $level -= 1;
+                                                       }
+                                               } else{
+                                                       // nested
+                                                       $level += 1;
+                                               }
+                                               $offset = $endMatches[0][1] + strlen($endMatches[0][0]);
+                                       }
+                                       if( ! $found ){
+                                               // couldn't find appropriate closing tag, skip
+                                               $this->splitAndAdd( $textExt, $count, substr( $text, $start, strlen($matches[0][0]) ) );
+                                               $start += strlen($matches[0][0]);
+                                       }
+                                       continue;
+                               }
+                       }
+                       // else: add as text extract
+                       $this->splitAndAdd( $textExt, $count, substr($text,$start) );
+                       break;
+               }
+               
+               $all = $textExt + $otherExt; // these have disjunct key sets
+               
+               wfProfileOut( "$fname-split" );
+               
+               // prepare regexps
+               foreach( $terms as $index => $term ) {
+                       $terms[$index] = preg_quote( $term, '/' );                      
+                       // manually do upper/lowercase stuff for utf-8 since PHP won't do it
+                       if(preg_match('/[\x80-\xff]/', $term) ){
+                               $terms[$index] = preg_replace_callback('/./us',array($this,'caseCallback'),$terms[$index]);
+                       }
+                       
+                       
+               }
+               $anyterm = implode( '|', $terms );
+               $phrase = implode("$wgSearchHighlightBoundaries+", $terms );
+
+               // FIXME: a hack to scale contextchars, a correct solution
+               // would be to have contextchars actually be char and not byte
+               // length, and do proper utf-8 substrings and lengths everywhere,
+               // but PHP is making that very hard and unclean to implement :(
+               $scale = strlen($anyterm) / mb_strlen($anyterm);
+               $contextchars = intval( $contextchars * $scale );
+               
+               $patPre = "(^|$wgSearchHighlightBoundaries)";
+               $patPost = "($wgSearchHighlightBoundaries|$)"; 
+               
+               $pat1 = "/(".$phrase.")/ui";
+               $pat2 = "/$patPre(".$anyterm.")$patPost/ui";
+               
+               wfProfileIn( "$fname-extract" );
+               
+               $left = $contextlines;
+
+               $snippets = array();
+               $offsets = array();             
+               
+               // show beginning only if it contains all words
+               $first = 0;
+               $firstText = '';
+               foreach($textExt as $index => $line){
+                       if(strlen($line)>0 && $line[0] != ';' && $line[0] != ':'){
+                               $firstText = $this->extract( $line, 0, $contextchars * $contextlines );
+                               $first = $index;
+                               break;
+                       }
+               }
+               if( $firstText ){
+                       $succ = true;
+                       // check if first text contains all terms
+                       foreach($terms as $term){
+                               if( ! preg_match("/$patPre".$term."$patPost/ui", $firstText) ){
+                                       $succ = false;
+                                       break;
+                               }
+                       }
+                       if( $succ ){
+                               $snippets[$first] = $firstText;
+                               $offsets[$first] = 0; 
+                       }
+               }
+               if( ! $snippets ) {             
+                       // match whole query on text 
+                       $this->process($pat1, $textExt, $left, $contextchars, $snippets, $offsets);
+                       // match whole query on templates/tables/images
+                       $this->process($pat1, $otherExt, $left, $contextchars, $snippets, $offsets);
+                       // match any words on text
+                       $this->process($pat2, $textExt, $left, $contextchars, $snippets, $offsets);
+                       // match any words on templates/tables/images
+                       $this->process($pat2, $otherExt, $left, $contextchars, $snippets, $offsets);
+                       
+                       ksort($snippets);
+               }
+               
+               // add extra chars to each snippet to make snippets constant size
+               $extended = array();                                            
+               if( count( $snippets ) == 0){
+                       // couldn't find the target words, just show beginning of article
+                       $targetchars = $contextchars * $contextlines;
+                       $snippets[$first] = '';
+                       $offsets[$first] = 0;
+               } else{
+                       // if begin of the article contains the whole phrase, show only that !! 
+                       if( array_key_exists($first,$snippets) && preg_match($pat1,$snippets[$first]) 
+                           && $offsets[$first] < $contextchars * 2 ){
+                               $snippets = array ($first => $snippets[$first]);
+                       }
+                       
+                       // calc by how much to extend existing snippets
+                       $targetchars = intval( ($contextchars * $contextlines) / count ( $snippets ) );
+               }  
+
+               foreach($snippets as $index => $line){
+                       $extended[$index] = $line;
+                       $len = strlen($line);
+                       if( $len < $targetchars - 20 ){
+                               // complete this line
+                               if($len < strlen( $all[$index] )){
+                                       $extended[$index] = $this->extract( $all[$index], $offsets[$index], $offsets[$index]+$targetchars, $offsets[$index]);
+                                       $len = strlen( $extended[$index] );
+                               }
+                               
+                               // add more lines
+                               $add = $index + 1;
+                               while( $len < $targetchars - 20 
+                                      && array_key_exists($add,$all) 
+                                      && !array_key_exists($add,$snippets) ){
+                                   $offsets[$add] = 0;
+                                   $tt = "\n".$this->extract( $all[$add], 0, $targetchars - $len, $offsets[$add] );
+                                       $extended[$add] = $tt;
+                                       $len += strlen( $tt );
+                                       $add++;                                         
+                               }
+                       } 
+               }
+               
+               //$snippets = array_map('htmlspecialchars', $extended);
+               $snippets = $extended;
+               $last = -1;
+               $extract = '';
+               foreach($snippets as $index => $line){
+                       if($last == -1) 
+                               $extract .= $line; // first line
+                       elseif($last+1 == $index && $offsets[$last]+strlen($snippets[$last]) >= strlen($all[$last]))
+                               $extract .= " ".$line; // continous lines
+                       else
+                               $extract .= '<b> ... </b>' . $line;
+
+                       $last = $index;
+               }
+               if( $extract )
+                       $extract .= '<b> ... </b>';
+               
+               $processed = array();
+               foreach($terms as $term){
+                       if( ! isset($processed[$term]) ){
+                               $pat3 = "/$patPre(".$term.")$patPost/ui"; // highlight word  
+                               $extract = preg_replace( $pat3,
+                                       "\\1<span class='searchmatch'>\\2</span>\\3", $extract );
+                               $processed[$term] = true;
+                       }
+               }
+               
+               wfProfileOut( "$fname-extract" );
+               
+               return $extract;
+       }
+       
+       /**
+        * Split text into lines and add it to extracts array
+        *
+        * @param array $extracts index -> $line
+        * @param int $count
+        * @param string $text
+        */
+       function splitAndAdd(&$extracts, &$count, $text){
+               $split = explode( "\n", $this->mCleanWikitext? $this->removeWiki($text) : $text );
+               foreach($split as $line){
+                       $tt = trim($line);
+                       if( $tt )
+                               $extracts[$count++] = $tt;
+               }
+       }
+       
+       /**
+        * Do manual case conversion for non-ascii chars
+        *
+        * @param unknown_type $matches
+        */
+       function caseCallback($matches){
+               global $wgContLang;
+               if( strlen($matches[0]) > 1 ){
+                       return '['.$wgContLang->lc($matches[0]).$wgContLang->uc($matches[0]).']';
+               } else
+                       return $matches[0];
+       }
+       
+       /**
+        * Extract part of the text from start to end, but by
+        * not chopping up words
+        * @param string $text
+        * @param int $start
+        * @param int $end
+        * @param int $posStart (out) actual start position
+        * @param int $posEnd (out) actual end position
+        * @return string  
+        */
+       function extract($text, $start, $end, &$posStart = null, &$posEnd = null ){
+               global $wgContLang;             
+               
+               if( $start != 0)
+                       $start = $this->position( $text, $start, 1 );
+               if( $end >= strlen($text) )
+                       $end = strlen($text);
+               else
+                       $end = $this->position( $text, $end );
+                       
+               if(!is_null($posStart))
+                       $posStart = $start;
+               if(!is_null($posEnd))
+                       $posEnd = $end;
+               
+               if($end > $start)
+                       return substr($text, $start, $end-$start);
+               else
+                       return '';
+       } 
+       
+       /**
+        * Find a nonletter near a point (index) in the text
+        *
+        * @param string $text
+        * @param int $point
+        * @param int $offset to found index
+        * @return int nearest nonletter index, or beginning of utf8 char if none
+        */
+       function position($text, $point, $offset=0 ){
+               $tolerance = 10;
+               $s = max( 0, $point - $tolerance );
+               $l = min( strlen($text), $point + $tolerance ) - $s;
+               $m = array();
+               if( preg_match('/[ ,.!?~!@#$%^&*\(\)+=\-\\\|\[\]"\'<>]/', substr($text,$s,$l), $m, PREG_OFFSET_CAPTURE ) ){
+                       return $m[0][1] + $s + $offset;
+               } else{
+                       // check if point is on a valid first UTF8 char
+                       $char = ord( $text[$point] );
+                       while( $char >= 0x80 && $char < 0xc0 ) {
+                               // skip trailing bytes
+                               $point++;
+                               if($point >= strlen($text))
+                                       return strlen($text);
+                               $char = ord( $text[$point] );
+                       }
+                       return $point;
+                       
+               }
        }
-       function setLimitOffset($l, $o) {}
-       function legalSearchChars() {}
-       function update() {}
-       function setnamespaces() {}
-       function searchtitle() {}
-       function searchtext() {}
+       
+       /**
+        * Search extracts for a pattern, and return snippets
+        *
+        * @param string $pattern regexp for matching lines
+        * @param array $extracts extracts to search   
+        * @param int $linesleft number of extracts to make
+        * @param int $contextchars length of snippet
+        * @param array $out map for highlighted snippets
+        * @param array $offsets map of starting points of snippets
+        * @protected
+        */
+       function process( $pattern, $extracts, &$linesleft, &$contextchars, &$out, &$offsets ){
+               if($linesleft == 0)
+                       return; // nothing to do
+               foreach($extracts as $index => $line){                  
+                       if( array_key_exists($index,$out) )
+                               continue; // this line already highlighted
+                               
+                       $m = array();
+                       if ( !preg_match( $pattern, $line, $m, PREG_OFFSET_CAPTURE ) )
+                               continue;
+                               
+                       $offset = $m[0][1];
+                       $len = strlen($m[0][0]);
+                       if($offset + $len < $contextchars)
+                               $begin = 0; 
+                       elseif( $len > $contextchars)
+                               $begin = $offset;
+                       else
+                               $begin = $offset + intval( ($len - $contextchars) / 2 );
+                       
+                       $end = $begin + $contextchars;
+                       
+                       $posBegin = $begin;
+                       // basic snippet from this line
+                       $out[$index] = $this->extract($line,$begin,$end,$posBegin);
+                       $offsets[$index] = $posBegin;
+                       $linesleft--;                   
+                       if($linesleft == 0)
+                               return;
+               }
+       }
+       
+       /** 
+        * Basic wikitext removal
+        * @protected
+        */
+       function removeWiki($text) {
+               $fname = __METHOD__;
+               wfProfileIn( $fname );
+               
+               //$text = preg_replace("/'{2,5}/", "", $text);
+               //$text = preg_replace("/\[[a-z]+:\/\/[^ ]+ ([^]]+)\]/", "\\2", $text);
+               //$text = preg_replace("/\[\[([^]|]+)\]\]/", "\\1", $text);
+               //$text = preg_replace("/\[\[([^]]+\|)?([^|]]+)\]\]/", "\\2", $text);
+               //$text = preg_replace("/\\{\\|(.*?)\\|\\}/", "", $text);
+               //$text = preg_replace("/\\[\\[[A-Za-z_-]+:([^|]+?)\\]\\]/", "", $text);
+               $text = preg_replace("/\\{\\{([^|]+?)\\}\\}/", "", $text);
+               $text = preg_replace("/\\{\\{([^|]+\\|)(.*?)\\}\\}/", "\\2", $text);
+               $text = preg_replace("/\\[\\[([^|]+?)\\]\\]/", "\\1", $text);           
+               $text = preg_replace_callback("/\\[\\[([^|]+\\|)(.*?)\\]\\]/", array($this,'linkReplace'), $text);
+               //$text = preg_replace("/\\[\\[([^|]+\\|)(.*?)\\]\\]/", "\\2", $text);
+               $text = preg_replace("/<\/?[^>]+>/", "", $text);
+               $text = preg_replace("/'''''/", "", $text);
+               $text = preg_replace("/('''|<\/?[iIuUbB]>)/", "", $text);
+               $text = preg_replace("/''/", "", $text);
+               
+               wfProfileOut( $fname );
+               return $text;
+       }
+       
+       /**
+        * callback to replace [[target|caption]] kind of links, if
+        * the target is category or image, leave it
+        *
+        * @param array $matches
+        */
+       function linkReplace($matches){
+               $colon = strpos( $matches[1], ':' ); 
+               if( $colon === false )
+                       return $matches[2]; // replace with caption
+               global $wgContLang;
+               $ns = substr( $matches[1], 0, $colon );
+               $index = $wgContLang->getNsIndex($ns);
+               if( $index !== false && ($index == NS_IMAGE || $index == NS_CATEGORY) )
+                       return $matches[0]; // return the whole thing 
+               else
+                       return $matches[2];
+               
+       }
+
+       /**
+     * Simple & fast snippet extraction, but gives completely unrelevant
+     * snippets
+     *
+     * @param string $text
+     * @param array $terms
+     * @param int $contextlines
+     * @param int $contextchars
+     * @return string
+     */
+    public function highlightSimple( $text, $terms, $contextlines, $contextchars ) {
+        global $wgLang, $wgContLang;
+        $fname = __METHOD__;
+    
+        $lines = explode( "\n", $text );
+        
+        $terms = implode( '|', $terms );
+        $terms = str_replace( '/', "\\/", $terms);
+        $max = intval( $contextchars ) + 1;
+        $pat1 = "/(.*)($terms)(.{0,$max})/i";
+
+        $lineno = 0;
+
+        $extract = "";
+        wfProfileIn( "$fname-extract" );
+        foreach ( $lines as $line ) {
+            if ( 0 == $contextlines ) {
+                break;
+            }
+            ++$lineno;
+            $m = array();
+            if ( ! preg_match( $pat1, $line, $m ) ) {
+                continue;
+            }
+            --$contextlines;
+            $pre = $wgContLang->truncate( $m[1], -$contextchars, ' ... ' );
+
+            if ( count( $m ) < 3 ) {
+                $post = '';
+            } else {
+                $post = $wgContLang->truncate( $m[3], $contextchars, ' ... ' );
+            }
+
+            $found = $m[2];
+
+            $line = htmlspecialchars( $pre . $found . $post );
+            $pat2 = '/(' . $terms . ")/i";
+            $line = preg_replace( $pat2,
+              "<span class='searchmatch'>\\1</span>", $line );
+
+            $extract .= "${line}\n";
+        }
+        wfProfileOut( "$fname-extract" );
+        
+        return $extract;
+    }
+       
+}
+
+/**
+ * Dummy class to be used when non-supported Database engine is present.
+ * @fixme Dummy class should probably try something at least mildly useful,
+ * such as a LIKE search through titles.
+ * @ingroup Search
+ */
+class SearchEngineDummy extends SearchEngine {
+       // no-op
 }