RevisionRenderer.php

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<?php
namespace MediaWiki\Revision;

use Html;
use InvalidArgumentException;
use ParserOptions;
use ParserOutput;
use Psr\Log\LoggerInterface;
use Psr\Log\NullLogger;
use Title;
use User;
use Wikimedia\Rdbms\ILoadBalancer;

class RevisionRenderer {

    private $saveParseLogger;

    private $loadBalancer;

    private $roleRegistery;

    private $dbDomain;

    public function __construct(
        ILoadBalancer $loadBalancer,
        SlotRoleRegistry $roleRegistry,
        $dbDomain = false
    ) {
        $this->loadBalancer = $loadBalancer;
        $this->roleRegistery = $roleRegistry;
        $this->dbDomain = $dbDomain;
        $this->saveParseLogger = new NullLogger();
    }

    public function setLogger( LoggerInterface $saveParseLogger ) {
        $this->saveParseLogger = $saveParseLogger;
    }

    public function getRenderedRevision(
        RevisionRecord $rev,
        ParserOptions $options = null,
        User $forUser = null,
        array $hints = []
    ) {
        if ( $rev->getWikiId() !== $this->dbDomain ) {
            throw new InvalidArgumentException( 'Mismatching wiki ID ' . $rev->getWikiId() );
        }

        $audience = $hints['audience']
            ?? ( $forUser ? RevisionRecord::FOR_THIS_USER : RevisionRecord::FOR_PUBLIC );

        if ( !$rev->audienceCan( RevisionRecord::DELETED_TEXT, $audience, $forUser ) ) {
            // Returning null here is awkward, but consist with the signature of
            // Revision::getContent() and RevisionRecord::getContent().
            return null;
        }

        if ( !$options ) {
            $options = ParserOptions::newCanonical( $forUser ?: 'canonical' );
        }

        $useMaster = $hints['use-master'] ?? false;

        $dbIndex = $useMaster
            ? DB_MASTER // use latest values
            : DB_REPLICA; // T154554

        $options->setSpeculativeRevIdCallback( function () use ( $dbIndex ) {
            return $this->getSpeculativeRevId( $dbIndex );
        } );
        $options->setSpeculativePageIdCallback( function () use ( $dbIndex ) {
            return $this->getSpeculativePageId( $dbIndex );
        } );

        if ( !$rev->getId() && $rev->getTimestamp() ) {
            // This is an unsaved revision with an already determined timestamp.
            // Make the "current" time used during parsing match that of the revision.
            // Any REVISION* parser variables will match up if the revision is saved.
            $options->setTimestamp( $rev->getTimestamp() );
        }

        $title = Title::newFromLinkTarget( $rev->getPageAsLinkTarget() );

        $renderedRevision = new RenderedRevision(
            $title,
            $rev,
            $options,
            function ( RenderedRevision $rrev, array $hints ) {
                return $this->combineSlotOutput( $rrev, $hints );
            },
            $audience,
            $forUser
        );

        $renderedRevision->setSaveParseLogger( $this->saveParseLogger );

        if ( isset( $hints['known-revision-output'] ) ) {
            $renderedRevision->setRevisionParserOutput( $hints['known-revision-output'] );
        }

        return $renderedRevision;
    }

    private function getSpeculativeRevId( $dbIndex ) {
        // Use a separate master connection in order to see the latest data, by avoiding
        // stale data from REPEATABLE-READ snapshots.
        $flags = ILoadBalancer::CONN_TRX_AUTOCOMMIT;

        $db = $this->loadBalancer->getConnectionRef( $dbIndex, [], $this->dbDomain, $flags );

        return 1 + (int)$db->selectField(
            'revision',
            'MAX(rev_id)',
            [],
            __METHOD__
        );
    }

    private function getSpeculativePageId( $dbIndex ) {
        // Use a separate master connection in order to see the latest data, by avoiding
        // stale data from REPEATABLE-READ snapshots.
        $flags = ILoadBalancer::CONN_TRX_AUTOCOMMIT;

        $db = $this->loadBalancer->getConnectionRef( $dbIndex, [], $this->dbDomain, $flags );

        return 1 + (int)$db->selectField(
            'page',
            'MAX(page_id)',
            [],
            __METHOD__
        );
    }

    private function combineSlotOutput( RenderedRevision $rrev, array $hints = [] ) {
        $revision = $rrev->getRevision();
        $slots = $revision->getSlots()->getSlots();

        $withHtml = $hints['generate-html'] ?? true;

        // short circuit if there is only the main slot
        if ( array_keys( $slots ) === [ SlotRecord::MAIN ] ) {
            return $rrev->getSlotParserOutput( SlotRecord::MAIN );
        }

        // move main slot to front
        if ( isset( $slots[SlotRecord::MAIN] ) ) {
            $slots = [ SlotRecord::MAIN => $slots[SlotRecord::MAIN] ] + $slots;
        }

        $combinedOutput = new ParserOutput( null );
        $slotOutput = [];

        $options = $rrev->getOptions();
        $options->registerWatcher( [ $combinedOutput, 'recordOption' ] );

        foreach ( $slots as $role => $slot ) {
            $out = $rrev->getSlotParserOutput( $role, $hints );
            $slotOutput[$role] = $out;

            // XXX: should the SlotRoleHandler be able to intervene here?
            $combinedOutput->mergeInternalMetaDataFrom( $out );
            $combinedOutput->mergeTrackingMetaDataFrom( $out );
        }

        if ( $withHtml ) {
            $html = '';
            $first = true;
            foreach ( $slotOutput as $role => $out ) {
                $roleHandler = $this->roleRegistery->getRoleHandler( $role );

                // TODO: put more fancy layout logic here, see T200915.
                $layout = $roleHandler->getOutputLayoutHints();
                $display = $layout['display'] ?? 'section';

                if ( $display === 'none' ) {
                    continue;
                }

                if ( $first ) {
                    // skip header for the first slot
                    $first = false;
                } else {
                    // NOTE: this placeholder is hydrated by ParserOutput::getText().
                    $headText = Html::element( 'mw:slotheader', [], $role );
                    $html .= Html::rawElement( 'h1', [ 'class' => 'mw-slot-header' ], $headText );
                }

                // XXX: do we want to put a wrapper div around the output?
                // Do we want to let $roleHandler do that?
                $html .= $out->getRawText();
                $combinedOutput->mergeHtmlMetaDataFrom( $out );
            }

            $combinedOutput->setText( $html );
        }

        $options->registerWatcher( null );
        return $combinedOutput;
    }

}