wikimedia/mediawiki-core

<?php
/**
 * 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
 */

namespace MediaWiki\Specials;

use MediaWiki\SpecialPage\SpecialPage;
use MediaWiki\Title\NamespaceInfo;
use MediaWiki\Title\Title;
use Wikimedia\Rdbms\IConnectionProvider;

/**
 * Redirect to a random page
 *
 * @ingroup SpecialPage
 * @author Rob Church <robchur@gmail.com>, Ilmari Karonen
 */
class SpecialRandomPage extends SpecialPage {
    private $namespaces; // namespaces to select pages from
    protected $isRedir = false; // should the result be a redirect?
    protected $extra = []; // Extra SQL statements

    private IConnectionProvider $dbProvider;

    /**
     * @param IConnectionProvider $dbProvider
     * @param NamespaceInfo $nsInfo
     */
    public function __construct(
        IConnectionProvider $dbProvider,
        NamespaceInfo $nsInfo
    ) {
        parent::__construct( 'Randompage' );
        $this->dbProvider = $dbProvider;
        $this->namespaces = $nsInfo->getContentNamespaces();
    }

    public function getNamespaces() {
        return $this->namespaces;
    }

    public function setNamespace( $ns ) {
        if ( !$this->isValidNS( $ns ) ) {
            $ns = NS_MAIN;
        }
        $this->namespaces = [ $ns ];
    }

    private function isValidNS( $ns ) {
        return $ns !== false && $ns >= 0;
    }

    // select redirects instead of normal pages?
    public function isRedirect() {
        return $this->isRedir;
    }

    public function execute( $par ) {
        $this->parsePar( $par );

        $title = $this->getRandomTitle();

        if ( $title === null ) {
            $this->setHeaders();
            // Message: randompage-nopages, randomredirect-nopages
            $this->getOutput()->addWikiMsg( strtolower( $this->getName() ) . '-nopages',
                $this->getNsList(), count( $this->namespaces ) );

            return;
        }

        $redirectParam = $this->isRedirect() ? [ 'redirect' => 'no' ] : [];
        $query = array_merge( $this->getRequest()->getValues(), $redirectParam );
        unset( $query['title'] );
        $this->getOutput()->redirect( $title->getFullURL( $query ) );
    }

    /**
     * Parse the subpage parameter that specifies namespaces
     *
     * @param string $par Subpage to special page
     */
    private function parsePar( $par ) {
        // Testing for stringiness since we want to catch
        // the empty string to mean main namespace only.
        if ( is_string( $par ) ) {
            $ns = $this->getContentLanguage()->getNsIndex( $par );
            if ( $ns === false && strpos( $par, ',' ) !== false ) {
                $nsList = [];
                // Comma separated list
                $parSplit = explode( ',', $par );
                foreach ( $parSplit as $potentialNs ) {
                    $ns = $this->getContentLanguage()->getNsIndex( $potentialNs );
                    if ( $this->isValidNS( $ns ) ) {
                        $nsList[] = $ns;
                    }
                    // Remove duplicate values, and re-index array
                    $nsList = array_unique( $nsList );
                    $nsList = array_values( $nsList );
                    if ( $nsList !== [] ) {
                        $this->namespaces = $nsList;
                    }
                }
            } else {
                // Note, that the case of $par being something
                // like "main" which is not a namespace, falls
                // through to here, and sets NS_MAIN, allowing
                // Special:Random/main or Special:Random/article
                // to work as expected.
                $this->setNamespace( $this->getContentLanguage()->getNsIndex( $par ) );
            }
        }
    }

    /**
     * Get a comma-delimited list of namespaces we don't have
     * any pages in
     * @return string
     */
    private function getNsList() {
        $contLang = $this->getContentLanguage();
        $nsNames = [];
        foreach ( $this->namespaces as $n ) {
            if ( $n === NS_MAIN ) {
                $nsNames[] = $this->msg( 'blanknamespace' )->plain();
            } else {
                $nsNames[] = $contLang->getNsText( $n );
            }
        }

        return $contLang->commaList( $nsNames );
    }

    /**
     * Choose a random title.
     * @return Title|null Title object (or null if nothing to choose from)
     */
    public function getRandomTitle() {
        $randstr = wfRandom();
        $title = null;

        if ( !$this->getHookRunner()->onSpecialRandomGetRandomTitle(
            $randstr, $this->isRedir, $this->namespaces,
            // @phan-suppress-next-line PhanTypeMismatchArgument Type mismatch on pass-by-ref args
            $this->extra, $title )
        ) {
            return $title;
        }

        $row = $this->selectRandomPageFromDB( $randstr, __METHOD__ );

        /* If we picked a value that was higher than any in
         * the DB, wrap around and select the page with the
         * lowest value instead!  One might think this would
         * skew the distribution, but in fact it won't cause
         * any more bias than what the page_random scheme
         * causes anyway.  Trust me, I'm a mathematician. :)
         */
        if ( !$row ) {
            $row = $this->selectRandomPageFromDB( "0", __METHOD__ );
        }

        if ( $row ) {
            return Title::makeTitleSafe( $row->page_namespace, $row->page_title );
        }

        return null;
    }

    protected function getQueryInfo( $randstr ) {
        $redirect = $this->isRedirect() ? 1 : 0;
        $tables = [ 'page' ];
        $conds = array_merge( [
            'page_namespace' => $this->namespaces,
            'page_is_redirect' => $redirect,
            'page_random >= ' . $randstr
        ], $this->extra );
        $joinConds = [];

        // Allow extensions to modify the query
        $this->getHookRunner()->onRandomPageQuery( $tables, $conds, $joinConds );

        return [
            'tables' => $tables,
            'fields' => [ 'page_title', 'page_namespace' ],
            'conds' => $conds,
            'options' => [
                'ORDER BY' => 'page_random',
                'LIMIT' => 1,
            ],
            'join_conds' => $joinConds
        ];
    }

    private function selectRandomPageFromDB( $randstr, $fname = __METHOD__ ) {
        $dbr = $this->dbProvider->getReplicaDatabase();

        $query = $this->getQueryInfo( $randstr );
        return $dbr->newSelectQueryBuilder()
            ->queryInfo( $query )
            ->caller( $fname )
            ->fetchRow();
    }

    protected function getGroupName() {
        return 'redirects';
    }
}

/**
 * Retain the old class name for backwards compatibility.
 * @deprecated since 1.41
 */
class_alias( SpecialRandomPage::class, 'SpecialRandomPage' );