CachingVideoDownloadManagerDatabase.java

package org.khanacademy.core.net.downloadmanager;

import org.khanacademy.core.net.downloadmanager.persistence.database.VideoDownloadManagerDatabase;
import org.khanacademy.core.net.downloadmanager.persistence.models.VideoDownloadEntity;
import org.khanacademy.core.topictree.identifiers.ContentItemIdentifier;

import com.google.common.base.Optional;
import com.google.common.base.Preconditions;
import com.google.common.collect.Maps;

import java.util.Map;

/**
 * TODO(mgp)
 */
public class CachingVideoDownloadManagerDatabase {

    private final VideoDownloadManagerDatabase mDatabase;
    private final Map<ContentItemIdentifier, VideoDownloadEntity> mEntities;

    public Foo(final VideoDownloadManagerDatabase database) {
        mDatabase = Preconditions.checkNotNull(database);
        mEntities = Maps.newHashMap();
    }

    public VideoDownloadEntity createVideoItemDownload(
            final ContentItemIdentifier contentItemIdentifier) {
        final VideoDownloadEntity videoDownloadEntity =
                mDatabase.createVideoItemDownload(contentItemIdentifier);

    }

    /**
     * @see VideoDownloadManagerDatabase#fetchVideoDownloadEntity(ContentItemIdentifier)
     */
    public Optional<VideoDownloadEntity> fetchVideoDownloadEntity(
            final ContentItemIdentifier contentItemIdentifier) {
        final VideoDownloadEntity cachedVideoDownloadEntity = mEntities.get(contentItemIdentifier);
        if (cachedVideoDownloadEntity != null) {
            return Optional.of(cachedVideoDownloadEntity);
        }

        final Optional<VideoDownloadEntity> downloadEntityOptional =
                mDatabase.fetchVideoDownloadEntity(contentItemIdentifier);
        if (downloadEntityOptional.isPresent()) {
            VideoDownloadEntity videoDownloadEntity = downloadEntityOptional.get();
            mEntities.put(contentItemIdentifier, videoDownloadEntity);
        }
        return downloadEntityOptional;
    }


}