wikimedia/mediawiki-extensions-Wikibase

<?php

namespace Wikibase\Lib\Store;

use Wikibase\DataModel\Entity\EntityId;

/**
 * @license GPL-2.0-or-later
 */
class RedirectResolvingLatestRevisionLookup {

    /**
     * @var EntityRevisionLookup
     */
    private $revisionLookup;

    /** @var array results of previously resolved entities keyed by entity id */
    private $resolvedEntities = [];

    public function __construct( EntityRevisionLookup $revisionLookup ) {
        $this->revisionLookup = $revisionLookup;
    }

    /**
     * @param EntityId $entityId
     * @return array|null Returns a tuple containing revision ID and target entity ID.
     *                    If the entity is not present or there is a double redirect null
     *                    is returned.
     * @phan-return array{0:int,1:EntityId}
     */
    public function lookupLatestRevisionResolvingRedirect( EntityId $entityId ) {
        if ( isset( $this->resolvedEntities[$entityId->getSerialization()] ) ) {
            return $this->resolvedEntities[$entityId->getSerialization()];
        }

        $revisionIdResult = $this->revisionLookup->getLatestRevisionId( $entityId );
        $returnNull = function () {
            return null;
        };

        $resolutionResult = $revisionIdResult
            ->onConcreteRevision( function ( $revisionId ) use ( $entityId ) {
                return [ $revisionId, $entityId ];
            } )
            ->onNonexistentEntity( $returnNull )
            ->onRedirect( function ( $revisionId, EntityId $redirectsTo ) use ( $returnNull ) {
                return $this->revisionLookup->getLatestRevisionId( $redirectsTo )
                    ->onNonexistentEntity( $returnNull )
                    ->onRedirect( $returnNull )
                    ->onConcreteRevision( function ( $revisionId ) use ( $redirectsTo ) {
                        return [ $revisionId, $redirectsTo ];
                    } )
                    ->map();
            } )
            ->map();

        $this->resolvedEntities[$entityId->getSerialization()] = $resolutionResult;

        return $resolutionResult;
    }

}