wikimedia/mediawiki-extensions-CirrusSearch

<?php

namespace CirrusSearch\Parser\QueryStringRegex;

use CirrusSearch\Parser\AST\NegatedNode;
use CirrusSearch\Parser\AST\PhrasePrefixNode;
use CirrusSearch\Parser\AST\PhraseQueryNode;
use CirrusSearch\Search\Escaper;
use Wikimedia\Assert\Assert;

/**
 * Detects phrase queries:
 * "simple phrase" : use the plain fields
 * "simple phrase"~ : use the stem fields
 * "simple phrase"~2 : force the slop to be 2
 * "simple phrase"~2~ : force the slop to be 2 and use the stem fields
 *
 * The phrase can be negated using a ! or -
 * Quotes can be escaped using \
 *
 * Supports phrase prefix as well:
 * "simple phras*"
 * iff slop and stem are not provided otherwise we send a simple phrase node
 */
class PhraseQueryParser {

    /**
     * Start of a phrase
     */
    public const PHRASE_START = '/\G(?<negate>-|!)?"/';

    /**
     * Normal phrase detection
     */
    private const PHRASE_REGEX = '/\G(?<negate>-|!)?"(?<value>(?:\\\\.|[^"])*)"(?<slop>~(?<slopvalue>\d+))?(?<fuzzy>~)?/';

    /**
     * @var Escaper
     */
    private $escaper;

    public function __construct( Escaper $escaper ) {
        $this->escaper = $escaper;
    }

    /**
     * @param string $query
     * @param int $start
     * @param int $end
     * @return PhraseQueryNode|PhrasePrefixNode|null
     */
    public function parse( $query, $start, $end ) {
        $match = [];
        Assert::precondition( $start < $end, '$start < $end' );
        Assert::precondition( $end <= strlen( $query ), '$end <= strlen( $query )' );
        if ( preg_match( self::PHRASE_REGEX, $query, $match, 0, $start ) === 1 ) {
            if ( strlen( $match[0] ) + $start <= $end ) {
                $slop = -1;
                $phrasePrefix = false;
                $quotedvalue = $match['value'];
                // Detects phrase prefix (still unclear why we do not allow *)
                if ( preg_match( '/^(?:\\\\.|[^*])+[*]$/', $quotedvalue ) === 1 ) {
                    $phrasePrefix = true;
                }
                if ( isset( $match['slopvalue'] ) && strlen( $match['slopvalue'] ) > 0 ) {
                    $slop = intval( $match['slopvalue'] );
                    $phrasePrefix = false;
                }
                $stem = false;
                if ( isset( $match['fuzzy'] ) ) {
                    $stem = true;
                    $phrasePrefix = false;
                }
                $negated = $match['negate'];
                $phraseStart = $start + strlen( $match['negate'] );
                $value = $this->escaper->unescape( $quotedvalue );
                if ( $phrasePrefix ) {
                    $node = new PhrasePrefixNode( $phraseStart, strlen( $match[0] ) + $start, rtrim( $value, '*' ) );
                } else {
                    $node = new PhraseQueryNode( $phraseStart, strlen( $match[0] ) + $start, $value, $slop,
                        $stem );
                }
                if ( $negated !== '' ) {
                    $node = new NegatedNode( $start, $node->getEndOffset(), $node, $negated );
                }
                return $node;
            }
        }
        return null;
    }
}