<?php
/**
 * Basic search engine
 *
 * @file
 * @ingroup Search
 */

/**
 * @defgroup Search Search
 */

/**
 * Contain a class for special pages
 * @ingroup Search
 */
class SearchEngine {
	var $limit = 10;
	var $offset = 0;
	var $prefix = '';
	var $searchTerms = array();
	var $namespaces = array( NS_MAIN );
	var $showRedirects = false;

	/// Feature values
	protected $features = array();

	/**
	 * @var DatabaseBase
	 */
	protected $db;

	function __construct($db = null) {
		if ( $db ) {
			$this->db = $db;
		} else {
			$this->db = wfGetDB( DB_SLAVE );
		}
	}

	/**
	 * Perform a full text search query and return a result set.
	 * If title searches are not supported or disabled, return null.
	 * STUB
	 *
	 * @param $term String: raw search term
	 * @return SearchResultSet
	 */
	function searchText( $term ) {
		return null;
	}

	/**
	 * Perform a title-only search query and return a result set.
	 * If title searches are not supported or disabled, return null.
	 * STUB
	 *
	 * @param $term String: raw search term
	 * @return SearchResultSet
	 */
	function searchTitle( $term ) {
		return null;
	}

	/**
	 * If this search backend can list/unlist redirects
	 * @deprecated since 1.18 Call supports( 'list-redirects' );
	 */
	function acceptListRedirects() {
		wfDeprecated( __METHOD__, '1.18' );
		return $this->supports( 'list-redirects' );
	}

	/**
	 * @since 1.18
	 * @param $feature String
	 * @return Boolean
	 */
	public function supports( $feature ) {
		switch( $feature ) {
		case 'list-redirects':
			return true;
		case 'title-suffix-filter':
		default:
			return false;
		}
	}

	/**
	 * Way to pass custom data for engines
	 * @since 1.18
	 * @param $feature String
	 * @param $data Mixed
	 * @return Noolean
	 */
	public function setFeatureData( $feature, $data ) {
		$this->features[$feature] = $data;
	}

	/**
	 * When overridden in derived class, performs database-specific conversions
	 * on text to be used for searching or updating search index.
	 * Default implementation does nothing (simply returns $string).
	 *
	 * @param $string string: String to process
	 * @return string
	 */
	public function normalizeText( $string ) {
		global $wgContLang;

		// Some languages such as Chinese require word segmentation
		return $wgContLang->segmentByWord( $string );
	}

	/**
	 * Transform search term in cases when parts of the query came as different GET params (when supported)
	 * e.g. for prefix queries: search=test&prefix=Main_Page/Archive -> test prefix:Main Page/Archive
	 */
	function transformSearchTerm( $term ) {
		return $term;
	}

	/**
	 * If an exact title match can be found, or a very slightly close match,
	 * return the title. If no match, returns NULL.
	 *
	 * @param $searchterm String
	 * @return Title
	 */
	public static function getNearMatch( $searchterm ) {
		$title = self::getNearMatchInternal( $searchterm );

		wfRunHooks( 'SearchGetNearMatchComplete', array( $searchterm, &$title ) );
		return $title;
	}

	/**
	 * Do a near match (see SearchEngine::getNearMatch) and wrap it into a
	 * SearchResultSet.
	 *
	 * @param $searchterm string
	 * @return SearchResultSet
	 */
	public static function getNearMatchResultSet( $searchterm ) {
		return new SearchNearMatchResultSet( self::getNearMatch( $searchterm ) );
	}

	/**
	 * Really find the title match.
	 */
	private static function getNearMatchInternal( $searchterm ) {
		global $wgContLang, $wgEnableSearchContributorsByIP;

		$allSearchTerms = array( $searchterm );

		if ( $wgContLang->hasVariants() ) {
			$allSearchTerms = array_merge( $allSearchTerms, $wgContLang->autoConvertToAllVariants( $searchterm ) );
		}

		$titleResult = null;
		if ( !wfRunHooks( 'SearchGetNearMatchBefore', array( $allSearchTerms, &$titleResult ) ) ) {
			return $titleResult;
		}

		foreach ( $allSearchTerms as $term ) {

			# Exact match? No need to look further.
			$title = Title::newFromText( $term );
			if ( is_null( $title ) ){
				return null;
			}

			if ( $title->isSpecialPage() || $title->isExternal() || $title->exists() ) {
				return $title;
			}

			# See if it still otherwise has content is some sane sense
			$page = WikiPage::factory( $title );
			if ( $page->hasViewableContent() ) {
				return $title;
			}

			# Now try all lower case (i.e. first letter capitalized)
			#
			$title = Title::newFromText( $wgContLang->lc( $term ) );
			if ( $title && $title->exists() ) {
				return $title;
			}

			# Now try capitalized string
			#
			$title = Title::newFromText( $wgContLang->ucwords( $term ) );
			if ( $title && $title->exists() ) {
				return $title;
			}

			# Now try all upper case
			#
			$title = Title::newFromText( $wgContLang->uc( $term ) );
			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 && $title->exists() ) {
				return $title;
			}

			// Give hooks a chance at better match variants
			$title = null;
			if ( !wfRunHooks( 'SearchGetNearMatch', array( $term, &$title ) ) ) {
				return $title;
			}
		}

		$title = Title::newFromText( $searchterm );


		# Entering an IP address goes to the contributions page
		if ( $wgEnableSearchContributorsByIP ) {
			if ( ( $title->getNamespace() == NS_USER && User::isIP( $title->getText() ) )
				|| User::isIP( trim( $searchterm ) ) ) {
				return SpecialPage::getTitleFor( 'Contributions', $title->getDBkey() );
			}
		}


		# Entering a user goes to the user page whether it's there or not
		if ( $title->getNamespace() == NS_USER ) {
			return $title;
		}

		# Go to images that exist even if there's no local page.
		# There may have been a funny upload, or it may be on a shared
		# file repository such as Wikimedia Commons.
		if ( $title->getNamespace() == NS_FILE ) {
			$image = wfFindFile( $title );
			if ( $image ) {
				return $title;
			}
		}

		# MediaWiki namespace? Page may be "implied" if not customized.
		# Just return it, with caps forced as the message system likes it.
		if ( $title->getNamespace() == NS_MEDIAWIKI ) {
			return Title::makeTitle( NS_MEDIAWIKI, $wgContLang->ucfirst( $title->getText() ) );
		}

		# Quoted term? Try without the quotes...
		$matches = array();
		if ( preg_match( '/^"([^"]+)"$/', $searchterm, $matches ) ) {
			return SearchEngine::getNearMatch( $matches[1] );
		}

		return null;
	}

	public static function legalSearchChars() {
		return "A-Za-z_'.0-9\\x80-\\xFF\\-";
	}

	/**
	 * Set the maximum number of results to return
	 * and how many to skip before returning the first.
	 *
	 * @param $limit Integer
	 * @param $offset Integer
	 */
	function setLimitOffset( $limit, $offset = 0 ) {
		$this->limit = intval( $limit );
		$this->offset = intval( $offset );
	}

	/**
	 * Set which namespaces the search should include.
	 * Give an array of namespace index numbers.
	 *
	 * @param $namespaces Array
	 */
	function setNamespaces( $namespaces ) {
		$this->namespaces = $namespaces;
	}

	/**
	 * Parse some common prefixes: all (search everything)
	 * or namespace names
	 *
	 * @param $query String
	 */
	function replacePrefixes( $query ) {
		global $wgContLang;

		$parsed = $query;
		if ( strpos( $query, ':' ) === false ) { // nothing to do
			wfRunHooks( 'SearchEngineReplacePrefixesComplete', array( $this, $query, &$parsed ) );
			return $parsed;
		}

		$allkeyword = wfMsgForContent( 'searchall' ) . ":";
		if ( strncmp( $query, $allkeyword, strlen( $allkeyword ) ) == 0 ) {
			$this->namespaces = null;
			$parsed = substr( $query, strlen( $allkeyword ) );
		} elseif ( strpos( $query, ':' ) !== false ) {
			$prefix = substr( $query, 0, strpos( $query, ':' ) );
			$index = $wgContLang->getNsIndex( $prefix );
			if ( $index !== false ) {
				$this->namespaces = array( $index );
				$parsed = substr( $query, strlen( $prefix ) + 1 );
			}
		}
		if ( trim( $parsed ) == '' )
			$parsed = $query; // prefix was the whole query

		wfRunHooks( 'SearchEngineReplacePrefixesComplete', array( $this, $query, &$parsed ) );

		return $parsed;
	}

	/**
	 * Make a list of searchable namespaces and their canonical names.
	 * @return Array
	 */
	public static function searchableNamespaces() {
		global $wgContLang;
		$arr = array();
		foreach ( $wgContLang->getNamespaces() as $ns => $name ) {
			if ( $ns >= NS_MAIN ) {
				$arr[$ns] = $name;
			}
		}

		wfRunHooks( 'SearchableNamespaces', array( &$arr ) );
		return $arr;
	}

	/**
	 * Extract default namespaces to search from the given user's
	 * settings, returning a list of index numbers.
	 *
	 * @param $user User
	 * @return Array
	 */
	public static function userNamespaces( $user ) {
		global $wgSearchEverythingOnlyLoggedIn;

		$searchableNamespaces = SearchEngine::searchableNamespaces();

		// get search everything preference, that can be set to be read for logged-in users
		// it overrides other options
		if ( !$wgSearchEverythingOnlyLoggedIn || $user->isLoggedIn() ) {
			if ( $user->getOption( 'searcheverything' ) ) {
				return array_keys( $searchableNamespaces );
			}
		}

		$arr = array();
		foreach ( $searchableNamespaces as $ns => $name ) {
			if ( $user->getOption( 'searchNs' . $ns ) ) {
				$arr[] = $ns;
			}
		}

		return $arr;
	}

	/**
	 * Find snippet highlight settings for all users
	 *
	 * @return Array contextlines, contextchars
	 */
	public static function userHighlightPrefs() {
		$contextlines = 2; // Hardcode this. Old defaults sucked. :)
		$contextchars = 75; // same as above.... :P
		return array( $contextlines, $contextchars );
	}

	/**
	 * An array of namespaces indexes to be searched by default
	 *
	 * @return Array
	 */
	public static function defaultNamespaces() {
		global $wgNamespacesToBeSearchedDefault;

		return array_keys( $wgNamespacesToBeSearchedDefault, true );
	}

	/**
	 * Get a list of namespace names useful for showing in tooltips
	 * and preferences
	 *
	 * @param $namespaces Array
	 */
	public static function namespacesAsText( $namespaces ) {
		global $wgContLang;

		$formatted = array_map( array( $wgContLang, 'getFormattedNsText' ), $namespaces );
		foreach ( $formatted as $key => $ns ) {
			if ( empty( $ns ) )
				$formatted[$key] = wfMsg( 'blanknamespace' );
		}
		return $formatted;
	}

	/**
	 * Return the help namespaces to be shown on Special:Search
	 *
	 * @return Array
	 */
	public static function helpNamespaces() {
		global $wgNamespacesToBeSearchedHelp;

		return array_keys( $wgNamespacesToBeSearchedHelp, true );
	}

	/**
	 * Return a 'cleaned up' search string
	 *
	 * @param $text String
	 * @return String
	 */
	function filter( $text ) {
		$lc = $this->legalSearchChars();
		return trim( preg_replace( "/[^{$lc}]/", " ", $text ) );
	}
	/**
	 * Load up the appropriate search engine class for the currently
	 * active database backend, and return a configured instance.
	 *
	 * @return SearchEngine
	 */
	public static function create() {
		global $wgSearchType;
		$dbr = null;
		if ( $wgSearchType ) {
			$class = $wgSearchType;
		} else {
			$dbr = wfGetDB( DB_SLAVE );
			$class = $dbr->getSearchEngine();
		}
		$search = new $class( $dbr );
		$search->setLimitOffset( 0, 0 );
		return $search;
	}

	/**
	 * Create or update the search index record for the given page.
	 * Title and text should be pre-processed.
	 * STUB
	 *
	 * @param $id Integer
	 * @param $title String
	 * @param $text String
	 */
	function update( $id, $title, $text ) {
		// no-op
	}

	/**
	 * Update a search index record's title only.
	 * Title should be pre-processed.
	 * STUB
	 *
	 * @param $id Integer
	 * @param $title String
	 */
	function updateTitle( $id, $title ) {
		// no-op
	}

	/**
	 * Get OpenSearch suggestion template
	 *
	 * @return String
	 */
	public static function getOpenSearchTemplate() {
		global $wgOpenSearchTemplate, $wgCanonicalServer;
		if ( $wgOpenSearchTemplate ) {
			return $wgOpenSearchTemplate;
		} else {
			$ns = implode( '|', SearchEngine::defaultNamespaces() );
			if ( !$ns ) {
				$ns = "0";
			}
			return $wgCanonicalServer . wfScript( 'api' ) . '?action=opensearch&search={searchTerms}&namespace=' . $ns;
		}
	}

	/**
	 * Get internal MediaWiki Suggest template
	 *
	 * @return String
	 */
	public static function getMWSuggestTemplate() {
		global $wgMWSuggestTemplate, $wgServer;
		if ( $wgMWSuggestTemplate )
			return $wgMWSuggestTemplate;
		else
			return $wgServer . wfScript( 'api' ) . '?action=opensearch&search={searchTerms}&namespace={namespaces}&suggest';
	}
}

/**
 * @ingroup Search
 */
class SearchResultSet {
	/**
	 * Fetch an array of regular expression fragments for matching
	 * the search terms as parsed by this engine in a text extract.
	 * STUB
	 *
	 * @return Array
	 */
	function termMatches() {
		return array();
	}

	function numRows() {
		return 0;
	}

	/**
	 * Return true if results are included in this result set.
	 * STUB
	 *
	 * @return Boolean
	 */
	function hasResults() {
		return false;
	}

	/**
	 * Some search modes return a total hit count for the query
	 * in the entire article database. This may include pages
	 * in namespaces that would not be matched on the given
	 * settings.
	 *
	 * Return null if no total hits number is supported.
	 *
	 * @return Integer
	 */
	function getTotalHits() {
		return null;
	}

	/**
	 * Some search modes return a suggested alternate term if there are
	 * no exact hits. Returns true if there is one on this set.
	 *
	 * @return Boolean
	 */
	function hasSuggestion() {
		return false;
	}

	/**
	 * @return String: suggested query, null if none
	 */
	function getSuggestionQuery() {
		return null;
	}

	/**
	 * @return String: HTML highlighted suggested query, '' if none
	 */
	function getSuggestionSnippet() {
		return '';
	}

	/**
	 * Return information about how and from where the results were fetched,
	 * should be useful for diagnostics and debugging
	 *
	 * @return String
	 */
	function getInfo() {
		return null;
	}

	/**
	 * Return a result set of hits on other (multiple) wikis associated with this one
	 *
	 * @return SearchResultSet
	 */
	function getInterwikiResults() {
		return null;
	}

	/**
	 * Check if there are results on other wikis
	 *
	 * @return Boolean
	 */
	function hasInterwikiResults() {
		return $this->getInterwikiResults() != null;
	}

	/**
	 * Fetches next search result, or false.
	 * STUB
	 *
	 * @return SearchResult
	 */
	function next() {
		return false;
	}

	/**
	 * Frees the result set, if applicable.
	 */
	function free() {
		// ...
	}
}

/**
 * This class is used for different SQL-based search engines shipped with MediaWiki
 */
class SqlSearchResultSet extends SearchResultSet {

	protected $mResultSet;

	function __construct( $resultSet, $terms ) {
		$this->mResultSet = $resultSet;
		$this->mTerms = $terms;
	}

	function termMatches() {
		return $this->mTerms;
	}

	function numRows() {
		if ( $this->mResultSet === false )
			return false;

		return $this->mResultSet->numRows();
	}

	function next() {
		if ( $this->mResultSet === false )
			return false;

		$row = $this->mResultSet->fetchObject();
		if ( $row === false )
			return false;

		return SearchResult::newFromRow( $row );
	}

	function free() {
		if ( $this->mResultSet === false )
			return false;

		$this->mResultSet->free();
	}
}

/**
 * @ingroup Search
 */
class SearchResultTooMany {
	# # Some search engines may bail out if too many matches are found
}


/**
 * @todo 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 Revision
	 */
	var $mRevision = null;
	var $mImage = null;

	/**
	 * @var Title
	 */
	var $mTitle;

	/**
	 * @var String
	 */
	var $mText;

	/**
	 * Return a new SearchResult and initializes it with a title.
	 *
	 * @param $title Title
	 * @return SearchResult
	 */
	public static function newFromTitle( $title ) {
		$result = new self();
		$result->initFromTitle( $title );
		return $result;
	}
	/**
	 * Return a new SearchResult and initializes it with a row.
	 *
	 * @param $row object
	 * @return SearchResult
	 */
	public static function newFromRow( $row ) {
		$result = new self();
		$result->initFromRow( $row );
		return $result;
	}

	public function __construct( $row = null ) {
		if ( !is_null( $row ) ) {
			// Backwards compatibility with pre-1.17 callers
			$this->initFromRow( $row );
		}
	}

	/**
	 * Initialize from a database row. Makes a Title and passes that to
	 * initFromTitle.
	 *
	 * @param $row object
	 */
	protected function initFromRow( $row ) {
		$this->initFromTitle( Title::makeTitle( $row->page_namespace, $row->page_title ) );
	}

	/**
	 * Initialize from a Title and if possible initializes a corresponding
	 * Revision and File.
	 *
	 * @param $title Title
	 */
	protected function initFromTitle( $title ) {
		$this->mTitle = $title;
		if ( !is_null( $this->mTitle ) ) {
			$this->mRevision = Revision::newFromTitle( $this->mTitle );
			if ( $this->mTitle->getNamespace() === NS_FILE )
				$this->mImage = wfFindFile( $this->mTitle );
		}
	}

	/**
	 * Check if this is result points to an invalid title
	 *
	 * @return Boolean
	 */
	function isBrokenTitle() {
		if ( is_null( $this->mTitle ) )
			return true;
		return false;
	}

	/**
	 * Check if target page is missing, happens when index is out of date
	 *
	 * @return Boolean
	 */
	function isMissingRevision() {
		return !$this->mRevision && !$this->mImage;
	}

	/**
	 * @return Title
	 */
	function getTitle() {
		return $this->mTitle;
	}

	/**
	 * @return Double or null if not supported
	 */
	function getScore() {
		return null;
	}

	/**
	 * Lazy initialization of article text from DB
	 */
	protected function initText() {
		if ( !isset( $this->mText ) ) {
			if ( $this->mRevision != null )
				$this->mText = $this->mRevision->getText();
			else // TODO: can we fetch raw wikitext for commons images?
				$this->mText = '';

		}
	}

	/**
	 * @param $terms Array: terms to highlight
	 * @return String: highlighted text snippet, null (and not '') if not supported
	 */
	function getTextSnippet( $terms ) {
		global $wgUser, $wgAdvancedSearchHighlighting;
		$this->initText();
		list( $contextlines, $contextchars ) = SearchEngine::userHighlightPrefs( $wgUser );
		$h = new SearchHighlighter();
		if ( $wgAdvancedSearchHighlighting )
			return $h->highlightText( $this->mText, $terms, $contextlines, $contextchars );
		else
			return $h->highlightSimple( $this->mText, $terms, $contextlines, $contextchars );
	}

	/**
	 * @param $terms Array: terms to highlight
	 * @return String: highlighted title, '' if not supported
	 */
	function getTitleSnippet( $terms ) {
		return '';
	}

	/**
	 * @param $terms Array: terms to highlight
	 * @return String: highlighted redirect name (redirect to this page), '' if none or not supported
	 */
	function getRedirectSnippet( $terms ) {
		return '';
	}

	/**
	 * @return Title object for the redirect to this page, null if none or not supported
	 */
	function getRedirectTitle() {
		return null;
	}

	/**
	 * @return string highlighted relevant section name, null if none or not supported
	 */
	function getSectionSnippet() {
		return '';
	}

	/**
	 * @return Title object (pagename+fragment) for the section, null if none or not supported
	 */
	function getSectionTitle() {
		return null;
	}

	/**
	 * @return String: timestamp
	 */
	function getTimestamp() {
		if ( $this->mRevision )
			return $this->mRevision->getTimestamp();
		elseif ( $this->mImage )
			return $this->mImage->getTimestamp();
		return '';
	}

	/**
	 * @return Integer: number of words
	 */
	function getWordCount() {
		$this->initText();
		return str_word_count( $this->mText );
	}

	/**
	 * @return Integer: size in bytes
	 */
	function getByteSize() {
		$this->initText();
		return strlen( $this->mText );
	}

	/**
	 * @return Boolean if hit has related articles
	 */
	function hasRelated() {
		return false;
	}

	/**
	 * @return String: interwiki prefix of the title (return iw even if title is broken)
	 */
	function getInterwikiPrefix() {
		return '';
	}
}
/**
 * A SearchResultSet wrapper for SearchEngine::getNearMatch
 */
class SearchNearMatchResultSet extends SearchResultSet {
	private $fetched = false;
	/**
	 * @param $match mixed Title if matched, else null
	 */
	public function __construct( $match ) {
		$this->result = $match;
	}
	public function hasResult() {
		return (bool)$this->result;
	}
	public function numRows() {
		return $this->hasResults() ? 1 : 0;
	}
	public function next() {
		if ( $this->fetched || !$this->result ) {
			return false;
		}
		$this->fetched = true;
		return SearchResult::newFromTitle( $this->result );
	}
}

/**
 * Highlight bits of wikitext
 *
 * @ingroup Search
 */
class SearchHighlighter {
	var $mCleanWikitext = true;

	function __construct( $cleanupWikitext = true ) {
		$this->mCleanWikitext = $cleanupWikitext;
	}

	/**
	 * Default implementation of wikitext highlighting
	 *
	 * @param $text String
	 * @param $terms Array: terms to highlight (unescaped)
	 * @param $contextlines Integer
	 * @param $contextchars Integer
	 * @return String
	 */
	public function highlightText( $text, $terms, $contextlines, $contextchars ) {
		global $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

		// @todo 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_FILE )
								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 ) {
			// 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] );
			} else {
				$terms[$index] = $term;
			}
		}
		$anyterm = implode( '|', $terms );
		$phrase = implode( "$wgSearchHighlightBoundaries+", $terms );

		// @todo 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
			if ( array_key_exists( $first, $all ) ) {
				$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 $extracts Array: index -> $line
	 * @param $count Integer
	 * @param $text String
	 */
	function splitAndAdd( &$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 $matches Array
	 */
	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 $text String
	 * @param $start Integer
	 * @param $end Integer
	 * @param $posStart Integer: (out) actual start position
	 * @param $posEnd Integer: (out) actual end position
	 * @return String
	 */
	function extract( $text, $start, $end, &$posStart = null, &$posEnd = null ) {
		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 $text String
	 * @param $point Integer
	 * @param $offset Integer: offset to found index
	 * @return Integer: 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;

		}
	}

	/**
	 * Search extracts for a pattern, and return snippets
	 *
	 * @param $pattern String: regexp for matching lines
	 * @param $extracts Array: extracts to search
	 * @param $linesleft Integer: number of extracts to make
	 * @param $contextchars Integer: length of snippet
	 * @param $out Array: map for highlighted snippets
	 * @param $offsets Array: 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 $matches Array
	 */
	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_FILE || $index == NS_CATEGORY ) )
			return $matches[0]; // return the whole thing
		else
			return $matches[2];

	}

	/**
	 * Simple & fast snippet extraction, but gives completely unrelevant
	 * snippets
	 *
	 * @param $text String
	 * @param $terms Array
	 * @param $contextlines Integer
	 * @param $contextchars Integer
	 * @return String
	 */
	public function highlightSimple( $text, $terms, $contextlines, $contextchars ) {
		global $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;
			// truncate function changes ... to relevant i18n message.
			$pre = $wgContLang->truncate( $m[1], - $contextchars, '...', false );

			if ( count( $m ) < 3 ) {
				$post = '';
			} else {
				$post = $wgContLang->truncate( $m[3], $contextchars, '...', false );
			}

			$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.
 * @todo 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
}
