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[mediawiki.git] / includes / search / SearchHighlighter.php

<?php
/**
 * Basic search engine highlighting
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 * @ingroup Search
 */

use MediaWiki\MainConfigNames;
use MediaWiki\MediaWikiServices;
use MediaWiki\Parser\Sanitizer;
use MediaWiki\Registration\ExtensionRegistry;

/**
 * Highlight bits of wikitext
 *
 * @newable
 * @note marked as newable in 1.35 for lack of a better alternative,
 *       but should use a factory in the future.
 * @ingroup Search
 */
class SearchHighlighter {
        public const DEFAULT_CONTEXT_LINES = 2;
        public const DEFAULT_CONTEXT_CHARS = 75;

        /** @var bool */
        protected $mCleanWikitext = true;

        /**
         * @stable to call
         * @warning If you pass false to this constructor, then
         *  the caller is responsible for HTML escaping.
         * @param bool $cleanupWikitext
         */
        public function __construct( $cleanupWikitext = true ) {
                $this->mCleanWikitext = $cleanupWikitext;
        }

        /**
         * Wikitext highlighting when $wgAdvancedSearchHighlighting = true
         *
         * @param string $text
         * @param string[] $terms Terms to highlight (not html escaped but
         *   regex escaped via SearchDatabase::regexTerm())
         * @param int $contextlines
         * @param int $contextchars
         * @return string
         */
        public function highlightText(
                $text,
                $terms,
                $contextlines = self::DEFAULT_CONTEXT_LINES,
                $contextchars = self::DEFAULT_CONTEXT_CHARS
        ) {
                $searchHighlightBoundaries = MediaWikiServices::getInstance()
                        ->getMainConfig()->get( MainConfigNames::SearchHighlightBoundaries );

                if ( $text == '' ) {
                        return '';
                }

                // split text into text + templates/links/tables
                $spat = "/(\\{\\{)|(\\[\\[[^\\]:]+:)|(\n\\{\\|)";
                // first capture group is for detecting nested templates/links/tables/references
                $endPatterns = [
                        1 => '/(\{\{)|(\}\})/', // template
                        2 => '/(\[\[)|(\]\])/', // image
                        3 => "/(\n\\{\\|)|(\n\\|\\})/" ]; // table

                // @todo FIXME: This should prolly be a hook or something
                // instead of hardcoding the name of the Cite extension
                if ( ExtensionRegistry::getInstance()->isLoaded( 'Cite' ) ) {
                        $spat .= '|(<ref>)'; // references via cite extension
                        $endPatterns[4] = '/(<ref>)|(<\/ref>)/';
                }
                $spat .= '/';
                $textExt = []; // text extracts
                $otherExt = []; // other extracts
                $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 (
                                                                MediaWikiServices::getInstance()->getContentLanguage()->
                                                                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--;
                                                        }
                                                } else {
                                                        // nested
                                                        $level++;
                                                }
                                                $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;
                }
                '@phan-var string[] $textExt';

                $all = $textExt + $otherExt; // these have disjunct key sets

                // 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',
                                        [ $this, 'caseCallback' ],
                                        $terms[$index]
                                );
                        } else {
                                $terms[$index] = $term;
                        }
                }
                $anyterm = implode( '|', $terms );
                $phrase = implode( "{$searchHighlightBoundaries}+", $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 );

                $patPre = "(^|{$searchHighlightBoundaries})";
                $patPost = "({$searchHighlightBoundaries}|$)";

                $pat1 = "/(" . $phrase . ")/ui";
                $pat2 = "/$patPre(" . $anyterm . ")$patPost/ui";

                $left = $contextlines;

                $snippets = [];
                $offsets = [];

                // 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 = [];
                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 = [ $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 );
                        // @phan-suppress-next-next-line PhanPossiblyUndeclaredVariable
                        // $targetchars is set when $snippes contains anything
                        if ( $len < $targetchars - 20 ) {
                                // complete this line
                                if ( $len < strlen( $all[$index] ) ) {
                                        $extended[$index] = $this->extract(
                                                $all[$index],
                                                $offsets[$index],
                                                // @phan-suppress-next-next-line PhanPossiblyUndeclaredVariable
                                                // $targetchars is set when $snippes contains anything
                                                $offsets[$index] + $targetchars,
                                                $offsets[$index]
                                        );
                                        $len = strlen( $extended[$index] );
                                }

                                // add more lines
                                $add = $index + 1;
                                // @phan-suppress-next-next-line PhanPossiblyUndeclaredVariable
                                // $targetchars is set when $snippes contains anything
                                while ( $len < $targetchars - 20
                                                && array_key_exists( $add, $all )
                                                && !array_key_exists( $add, $snippets ) ) {
                                        $offsets[$add] = 0;
                                        // @phan-suppress-next-next-line PhanPossiblyUndeclaredVariable
                                        // $targetchars is set when $snippes contains anything
                                        $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; // continuous lines
                        } else {
                                $extract .= '<b> ... </b>' . $line;
                        }

                        $last = $index;
                }
                if ( $extract ) {
                        $extract .= '<b> ... </b>';
                }

                $processed = [];
                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;
                        }
                }

                return $extract;
        }

        /**
         * Split text into lines and add it to extracts array
         *
         * @param string[] &$extracts Index -> $line
         * @param int &$count
         * @param string $text
         */
        private function splitAndAdd( &$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 array $matches
         * @return string
         */
        private function caseCallback( $matches ) {
                if ( strlen( $matches[0] ) > 1 ) {
                        $contLang = MediaWikiServices::getInstance()->getContentLanguage();
                        return '[' . $contLang->lc( $matches[0] ) .
                                $contLang->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 $end
         * @param int|null &$posStart (out) actual start position
         * @param int|null &$posEnd (out) actual end position
         * @return string
         */
        private 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 ( $posStart !== null ) {
                        $posStart = $start;
                }
                if ( $posEnd !== null ) {
                        $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 Offset to found index
         * @return int Nearest nonletter index, or beginning of utf8 char if none
         */
        private function position( $text, $point, $offset = 0 ) {
                $tolerance = 10;
                $s = max( 0, $point - $tolerance );
                $l = min( strlen( $text ), $point + $tolerance ) - $s;
                $m = [];

                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 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
         */
        private 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 = [];
                        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
         * @param string $text
         * @return string
         */
        private function removeWiki( $text ) {
                $text = preg_replace( "/\\{\\{([^|]+?)\\}\\}/", "", $text );
                $text = preg_replace( "/\\{\\{([^|]+\\|)(.*?)\\}\\}/", "\\2", $text );
                $text = preg_replace( "/\\[\\[([^|]+?)\\]\\]/", "\\1", $text );
                $text = preg_replace_callback(
                        "/\\[\\[([^|]+\\|)(.*?)\\]\\]/",
                        [ $this, 'linkReplace' ],
                        $text
                );
                $text = preg_replace( "/<\/?[^>]+>/", "", $text );
                $text = preg_replace( "/'''''/", "", $text );
                $text = preg_replace( "/('''|<\/?[iIuUbB]>)/", "", $text );
                $text = preg_replace( "/''/", "", $text );

                // Note, the previous /<\/?[^>]+>/ is insufficient
                // for XSS safety as the HTML tag can span multiple
                // search results (T144845).
                $text = Sanitizer::escapeHtmlAllowEntities( $text );
                return $text;
        }

        /**
         * callback to replace [[target|caption]] kind of links, if
         * the target is category or image, leave it
         *
         * @param array $matches
         * @return string
         */
        private function linkReplace( $matches ) {
                $colon = strpos( $matches[1], ':' );
                if ( $colon === false ) {
                        return $matches[2]; // replace with caption
                }
                $ns = substr( $matches[1], 0, $colon );
                $index = MediaWikiServices::getInstance()->getContentLanguage()->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 irrelevant
         * snippets
         *
         * Used when $wgAdvancedSearchHighlighting is false.
         *
         * @param string $text
         * @param string[] $terms Escaped for regex by SearchDatabase::regexTerm()
         * @param int $contextlines
         * @param int $contextchars
         * @return string
         */
        public function highlightSimple(
                $text,
                $terms,
                $contextlines = self::DEFAULT_CONTEXT_LINES,
                $contextchars = self::DEFAULT_CONTEXT_CHARS
        ) {
                $lines = explode( "\n", $text );

                $terms = implode( '|', $terms );
                $max = intval( $contextchars ) + 1;
                $pat1 = "/(.*)($terms)(.{0,$max})/ui";

                $extract = '';
                $contLang = MediaWikiServices::getInstance()->getContentLanguage();
                foreach ( $lines as $line ) {
                        if ( $contextlines == 0 ) {
                                break;
                        }
                        $m = [];
                        if ( !preg_match( $pat1, $line, $m ) ) {
                                continue;
                        }
                        --$contextlines;
                        // truncate function changes ... to relevant i18n message.
                        $pre = $contLang->truncateForVisual( $m[1], -$contextchars, '...', false );

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

                        $found = $m[2];

                        $line = htmlspecialchars( $pre . $found . $post );
                        $pat2 = '/(' . $terms . ')/ui';
                        $line = preg_replace( $pat2, '<span class="searchmatch">\1</span>', $line );

                        $extract .= "{$line}\n";
                }

                return $extract;
        }

        /**
         * Returns the first few lines of the text
         *
         * @param string $text
         * @param int $contextlines Max number of returned lines
         * @param int $contextchars Average number of characters per line
         * @return string
         */
        public function highlightNone(
                $text,
                $contextlines = self::DEFAULT_CONTEXT_LINES,
                $contextchars = self::DEFAULT_CONTEXT_CHARS
        ) {
                $match = [];
                $text = ltrim( $text ) . "\n"; // make sure the preg_match may find the last line
                $text = str_replace( "\n\n", "\n", $text ); // remove empty lines
                preg_match( "/^(.*\n){0,$contextlines}/", $text, $match );

                // Trim and limit to max number of chars
                $text = htmlspecialchars( substr( trim( $match[0] ), 0, $contextlines * $contextchars ) );
                return str_replace( "\n", '<br>', $text );
        }
}