SpecialDoubleRedirects.php

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<?php
class DoubleRedirectsPage extends QueryPage {
    function __construct( $name = 'DoubleRedirects' ) {
        parent::__construct( $name );
    }

    public function isExpensive() {
        return true;
    }

    function isSyndicated() {
        return false;
    }

    function sortDescending() {
        return false;
    }

    function getPageHeader() {
        return $this->msg( 'doubleredirectstext' )->parseAsBlock();
    }

    function reallyGetQueryInfo( $namespace = null, $title = null ) {
        $limitToTitle = !( $namespace === null && $title === null );
        $dbr = wfGetDB( DB_REPLICA );
        $retval = [
            'tables' => [
                'ra' => 'redirect',
                'rb' => 'redirect',
                'pa' => 'page',
                'pb' => 'page'
            ],
            'fields' => [
                'namespace' => 'pa.page_namespace',
                'title' => 'pa.page_title',
                'value' => 'pa.page_title',

                'nsb' => 'pb.page_namespace',
                'tb' => 'pb.page_title',

                // Select fields from redirect instead of page. Because there may
                // not actually be a page table row for this target (e.g. for interwiki redirects)
                'nsc' => 'rb.rd_namespace',
                'tc' => 'rb.rd_title',
                'iwc' => 'rb.rd_interwiki',
            ],
            'conds' => [
                'ra.rd_from = pa.page_id',

                // Filter out redirects where the target goes interwiki (bug 40353).
                // This isn't an optimization, it is required for correct results,
                // otherwise a non-double redirect like Bar -> w:Foo will show up
                // like "Bar -> Foo -> w:Foo".

                // Need to check both NULL and "" for some reason,
                // apparently either can be stored for non-iw entries.
                'ra.rd_interwiki IS NULL OR ra.rd_interwiki = ' . $dbr->addQuotes( '' ),

                'pb.page_namespace = ra.rd_namespace',
                'pb.page_title = ra.rd_title',

                'rb.rd_from = pb.page_id',
            ]
        ];

        if ( $limitToTitle ) {
            $retval['conds']['pa.page_namespace'] = $namespace;
            $retval['conds']['pa.page_title'] = $title;
        }

        return $retval;
    }

    public function getQueryInfo() {
        return $this->reallyGetQueryInfo();
    }

    function getOrderFields() {
        return [ 'ra.rd_namespace', 'ra.rd_title' ];
    }

    function formatResult( $skin, $result ) {
        $titleA = Title::makeTitle( $result->namespace, $result->title );

        // If only titleA is in the query, it means this came from
        // querycache (which only saves 3 columns).
        // That does save the bulk of the query cost, but now we need to
        // get a little more detail about each individual entry quickly
        // using the filter of reallyGetQueryInfo.
        if ( $result && !isset( $result->nsb ) ) {
            $dbr = wfGetDB( DB_REPLICA );
            $qi = $this->reallyGetQueryInfo(
                $result->namespace,
                $result->title
            );
            $res = $dbr->select(
                $qi['tables'],
                $qi['fields'],
                $qi['conds'],
                __METHOD__
            );

            if ( $res ) {
                $result = $dbr->fetchObject( $res );
            }
        }
        if ( !$result ) {
            return '<del>' . Linker::link( $titleA, null, [], [ 'redirect' => 'no' ] ) . '</del>';
        }

        $titleB = Title::makeTitle( $result->nsb, $result->tb );
        $titleC = Title::makeTitle( $result->nsc, $result->tc, '', $result->iwc );

        $linkA = Linker::linkKnown(
            $titleA,
            null,
            [],
            [ 'redirect' => 'no' ]
        );

        // if the page is editable, add an edit link
        if (
            // check user permissions
            $this->getUser()->isAllowed( 'edit' ) &&
            // check, if the content model is editable through action=edit
            ContentHandler::getForTitle( $titleA )->supportsDirectEditing()
        ) {
            $edit = Linker::linkKnown(
                $titleA,
                $this->msg( 'parentheses', $this->msg( 'editlink' )->text() )->escaped(),
                [],
                [
                    'action' => 'edit'
                ]
            );
        } else {
            $edit = '';
        }

        $linkB = Linker::linkKnown(
            $titleB,
            null,
            [],
            [ 'redirect' => 'no' ]
        );

        $linkC = Linker::linkKnown( $titleC );

        $lang = $this->getLanguage();
        $arr = $lang->getArrow() . $lang->getDirMark();

        return ( "{$linkA} {$edit} {$arr} {$linkB} {$arr} {$linkC}" );
    }

    function preprocessResults( $db, $res ) {
        if ( !$res->numRows() ) {
            return;
        }

        $batch = new LinkBatch;
        foreach ( $res as $row ) {
            $batch->add( $row->namespace, $row->title );
            if ( isset( $row->nsb ) ) {
                // lazy loaded when using cached results
                $batch->add( $row->nsb, $row->tb );
            }
            if ( isset( $row->iwc ) && !$row->iwc ) {
                // lazy loaded when using cached result, not added when interwiki link
                $batch->add( $row->nsc, $row->tc );
            }
        }
        $batch->execute();

        // Back to start for display
        $res->seek( 0 );
    }

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