PrefixSearch.php

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<?php
use MediaWiki\MediaWikiServices;

abstract class PrefixSearch {
    public function search( $search, $limit, $namespaces = [], $offset = 0 ) {
        $search = trim( $search );
        if ( $search == '' ) {
            return []; // Return empty result
        }

        $hasNamespace = SearchEngine::parseNamespacePrefixes( $search, false, true );
        if ( $hasNamespace !== false ) {
            list( $search, $namespaces ) = $hasNamespace;
        }

        return $this->searchBackend( $namespaces, $search, $limit, $offset );
    }

    public function searchWithVariants( $search, $limit, array $namespaces, $offset = 0 ) {
        $searches = $this->search( $search, $limit, $namespaces, $offset );

        // if the content language has variants, try to retrieve fallback results
        $fallbackLimit = $limit - count( $searches );
        if ( $fallbackLimit > 0 ) {
            $fallbackSearches = MediaWikiServices::getInstance()->getContentLanguage()->
                autoConvertToAllVariants( $search );
            $fallbackSearches = array_diff( array_unique( $fallbackSearches ), [ $search ] );

            foreach ( $fallbackSearches as $fbs ) {
                $fallbackSearchResult = $this->search( $fbs, $fallbackLimit, $namespaces );
                $searches = array_merge( $searches, $fallbackSearchResult );
                $fallbackLimit -= count( $fallbackSearchResult );

                if ( $fallbackLimit == 0 ) {
                    break;
                }
            }
        }
        return $searches;
    }

    abstract protected function titles( array $titles );

    abstract protected function strings( array $strings );

    protected function searchBackend( $namespaces, $search, $limit, $offset ) {
        if ( count( $namespaces ) == 1 ) {
            $ns = $namespaces[0];
            if ( $ns == NS_MEDIA ) {
                $namespaces = [ NS_FILE ];
            } elseif ( $ns == NS_SPECIAL ) {
                return $this->titles( $this->specialSearch( $search, $limit, $offset ) );
            }
        }
        $srchres = [];
        if ( Hooks::run(
            'PrefixSearchBackend',
            [ $namespaces, $search, $limit, &$srchres, $offset ]
        ) ) {
            return $this->titles( $this->defaultSearchBackend( $namespaces, $search, $limit, $offset ) );
        }
        return $this->strings(
            $this->handleResultFromHook( $srchres, $namespaces, $search, $limit, $offset ) );
    }

    private function handleResultFromHook( $srchres, $namespaces, $search, $limit, $offset ) {
        if ( $offset === 0 ) {
            // Only perform exact db match if offset === 0
            // This is still far from perfect but at least we avoid returning the
            // same title afain and again when the user is scrolling with a query
            // that matches a title in the db.
            $rescorer = new SearchExactMatchRescorer();
            $srchres = $rescorer->rescore( $search, $namespaces, $srchres, $limit );
        }
        return $srchres;
    }

    protected function specialSearch( $search, $limit, $offset ) {
        $searchParts = explode( '/', $search, 2 );
        $searchKey = $searchParts[0];
        $subpageSearch = $searchParts[1] ?? null;

        // Handle subpage search separately.
        $spFactory = MediaWikiServices::getInstance()->getSpecialPageFactory();
        if ( $subpageSearch !== null ) {
            // Try matching the full search string as a page name
            $specialTitle = Title::makeTitleSafe( NS_SPECIAL, $searchKey );
            if ( !$specialTitle ) {
                return [];
            }
            $special = $spFactory->getPage( $specialTitle->getText() );
            if ( $special ) {
                $subpages = $special->prefixSearchSubpages( $subpageSearch, $limit, $offset );
                return array_map( function ( $sub ) use ( $specialTitle ) {
                    return $specialTitle->getSubpage( $sub );
                }, $subpages );
            } else {
                return [];
            }
        }

        # normalize searchKey, so aliases with spaces can be found - T27675
        $contLang = MediaWikiServices::getInstance()->getContentLanguage();
        $searchKey = str_replace( ' ', '_', $searchKey );
        $searchKey = $contLang->caseFold( $searchKey );

        // Unlike SpecialPage itself, we want the canonical forms of both
        // canonical and alias title forms...
        $keys = [];
        foreach ( $spFactory->getNames() as $page ) {
            $keys[$contLang->caseFold( $page )] = [ 'page' => $page, 'rank' => 0 ];
        }

        foreach ( $contLang->getSpecialPageAliases() as $page => $aliases ) {
            if ( !in_array( $page, $spFactory->getNames() ) ) {# T22885
                continue;
            }

            foreach ( $aliases as $key => $alias ) {
                $keys[$contLang->caseFold( $alias )] = [ 'page' => $alias, 'rank' => $key ];
            }
        }
        ksort( $keys );

        $matches = [];
        foreach ( $keys as $pageKey => $page ) {
            if ( $searchKey === '' || strpos( $pageKey, $searchKey ) === 0 ) {
                // T29671: Don't use SpecialPage::getTitleFor() here because it
                // localizes its input leading to searches for e.g. Special:All
                // returning Spezial:MediaWiki-Systemnachrichten and returning
                // Spezial:Alle_Seiten twice when $wgLanguageCode == 'de'
                $matches[$page['rank']][] = Title::makeTitleSafe( NS_SPECIAL, $page['page'] );

                if ( isset( $matches[0] ) && count( $matches[0] ) >= $limit + $offset ) {
                    // We have enough items in primary rank, no use to continue
                    break;
                }
            }

        }

        // Ensure keys are in order
        ksort( $matches );
        // Flatten the array
        $matches = array_reduce( $matches, 'array_merge', [] );

        return array_slice( $matches, $offset, $limit );
    }

    public function defaultSearchBackend( $namespaces, $search, $limit, $offset ) {
        // Backwards compatability with old code. Default to NS_MAIN if no namespaces provided.
        if ( $namespaces === null ) {
            $namespaces = [];
        }
        if ( !$namespaces ) {
            $namespaces[] = NS_MAIN;
        }

        // Construct suitable prefix for each namespace. They differ in cases where
        // some namespaces always capitalize and some don't.
        $prefixes = [];
        foreach ( $namespaces as $namespace ) {
            // For now, if special is included, ignore the other namespaces
            if ( $namespace == NS_SPECIAL ) {
                return $this->specialSearch( $search, $limit, $offset );
            }

            $title = Title::makeTitleSafe( $namespace, $search );
            // Why does the prefix default to empty?
            $prefix = $title ? $title->getDBkey() : '';
            $prefixes[$prefix][] = $namespace;
        }

        $dbr = wfGetDB( DB_REPLICA );
        // Often there is only one prefix that applies to all requested namespaces,
        // but sometimes there are two if some namespaces do not always capitalize.
        $conds = [];
        foreach ( $prefixes as $prefix => $namespaces ) {
            $condition = [
                'page_namespace' => $namespaces,
                'page_title' . $dbr->buildLike( $prefix, $dbr->anyString() ),
            ];
            $conds[] = $dbr->makeList( $condition, LIST_AND );
        }

        $table = 'page';
        $fields = [ 'page_id', 'page_namespace', 'page_title' ];
        $conds = $dbr->makeList( $conds, LIST_OR );
        $options = [
            'LIMIT' => $limit,
            'ORDER BY' => [ 'page_title', 'page_namespace' ],
            'OFFSET' => $offset
        ];

        $res = $dbr->select( $table, $fields, $conds, __METHOD__, $options );

        return iterator_to_array( TitleArray::newFromResult( $res ) );
    }

    protected function validateNamespaces( $namespaces ) {
        // We will look at each given namespace against content language namespaces
        $validNamespaces = MediaWikiServices::getInstance()->getContentLanguage()->getNamespaces();
        if ( is_array( $namespaces ) && count( $namespaces ) > 0 ) {
            $valid = [];
            foreach ( $namespaces as $ns ) {
                if ( is_numeric( $ns ) && array_key_exists( $ns, $validNamespaces ) ) {
                    $valid[] = $ns;
                }
            }
            if ( count( $valid ) > 0 ) {
                return $valid;
            }
        }

        return [ NS_MAIN ];
    }
}