wikimedia/mediawiki-extensions-Wikibase

<?php

namespace Wikibase\Lib\Store;

use Wikibase\DataModel\Entity\EntityId;
use Wikibase\DataModel\Entity\EntityRedirect;
use Wikimedia\Assert\Assert;

/**
 * Implementation of EntityLookup that caches the obtained entities.
 *
 * @license GPL-2.0-or-later
 * @author Daniel Kinzler
 */
class CachingEntityRevisionLookup implements EntityRevisionLookup, EntityStoreWatcher {

    /**
     * @var EntityRevisionCache
     */
    private $entityRevisionCache;

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

    /**
     * @var CacheRetrievingEntityRevisionLookup
     */
    private $cacheRetrievingLookup;

    /**
     * @var bool
     */
    private $shouldVerifyRevision = false;

    public function __construct(
        EntityRevisionCache $entityRevisionCache,
        EntityRevisionLookup $entityRevisionLookup
    ) {
        $this->entityRevisionCache = $entityRevisionCache;
        $this->lookup = $entityRevisionLookup;

        $this->cacheRetrievingLookup = new CacheRetrievingEntityRevisionLookup(
            $entityRevisionCache,
            $entityRevisionLookup
        );
    }

    /**
     * Determine whether the revision of the cached entity should be verified against the
     * current revision in the underlying lookup.
     *
     * @param bool $shouldVerifyRevision
     */
    public function setVerifyRevision( $shouldVerifyRevision ) {
        $this->shouldVerifyRevision = $shouldVerifyRevision;
        $this->cacheRetrievingLookup->setVerifyRevision( $shouldVerifyRevision );
    }

    /**
     * @see EntityRevisionLookup::getEntityRevision
     *
     * @note If this lookup is configured to verify revisions, getLatestRevisionId()
     * will be called on the underlying lookup to check whether the cached revision is
     * still the latest. Otherwise, any cached revision will be used if $revisionId=0.
     *
     * @param EntityId $entityId
     * @param int $revisionId The desired revision id, or 0 for the latest revision.
     * @param string $mode LATEST_FROM_REPLICA, LATEST_FROM_REPLICA_WITH_FALLBACK or
     *        LATEST_FROM_MASTER.
     *
     * @throws StorageException
     * @return EntityRevision|null
     */
    public function getEntityRevision(
        EntityId $entityId,
        $revisionId = 0,
        $mode = LookupConstants::LATEST_FROM_REPLICA
    ) {
        Assert::parameterType( 'integer', $revisionId, '$revisionId' );
        Assert::parameterType( 'string', $mode, '$mode' );

        $entityRevision = $this->cacheRetrievingLookup->getEntityRevisionFromCache( $entityId, $revisionId, $mode );

        if ( $entityRevision === null ) {
            $entityRevision = $this->fetchEntityRevision( $entityId, $revisionId, $mode );
        }

        return $entityRevision;
    }

    /**
     * Fetches the EntityRevision and updates the cache accordingly.
     *
     * @param EntityId $entityId
     * @param int $revisionId
     * @param string $mode
     *
     * @throws StorageException
     * @return EntityRevision|null
     */
    private function fetchEntityRevision( EntityId $entityId, $revisionId, $mode ) {
        $entityRevision = $this->lookup->getEntityRevision( $entityId, $revisionId, $mode );

        if ( $revisionId === 0 ) {
            if ( $entityRevision === null ) {
                $this->entityRevisionCache->delete( $entityId );
            } else {
                $this->entityRevisionCache->set( $entityRevision );
            }
        }

        return $entityRevision;
    }

    /**
     * @see EntityRevisionLookup::getLatestRevisionId
     *
     * @param EntityId $entityId
     * @param string $mode
     *
     * @return LatestRevisionIdResult
     */
    public function getLatestRevisionId( EntityId $entityId, $mode = LookupConstants::LATEST_FROM_REPLICA ) {
        return $this->cacheRetrievingLookup->getLatestRevisionId( $entityId, $mode );
    }

    /**
     * Notifies the cache that an Entity was created or updated.
     *
     * @param EntityRevision $entityRevision
     */
    public function entityUpdated( EntityRevision $entityRevision ) {
        $this->entityRevisionCache->set( $entityRevision );
    }

    /**
     * Notifies the cache that a redirect was created or updated.
     *
     * @param EntityRedirect $entityRedirect
     * @param int $revisionId
     */
    public function redirectUpdated( EntityRedirect $entityRedirect, $revisionId ) {
        //TODO: cache redirects
        $this->entityRevisionCache->delete( $entityRedirect->getEntityId() );
    }

    /**
     * Notifies the cache that an Entity or redirect was deleted.
     *
     * @param EntityId $entityId
     */
    public function entityDeleted( EntityId $entityId ) {
        $this->entityRevisionCache->delete( $entityId );
        // XXX: if $this->lookup supports purging, purge?
    }

}