OkHttpVideoDownloadManager.java

package org.khanacademy.core.net.videodownloadmanager;

import org.khanacademy.core.net.downloadmanager.DownloadManager;
import org.khanacademy.core.net.downloadmanager.okhttp.OkHttpDownloadManager;
import org.khanacademy.core.net.downloadmanager.okhttp.OkHttpDownloadManager.ResourceFunctions;
import org.khanacademy.core.topictree.models.Video;
import org.khanacademy.core.topictree.models.Video.DownloadFormat;

import com.squareup.okhttp.OkHttpClient;

import java.io.File;
import java.net.URI;

/**
 * Downloads videos using OkHttp.
 */
public final class OkHttpVideoDownloadManager {
    private static final ResourceFunctions<Video, String> RESOURCE_FUNCTIONS = new ResourceFunctions<Video, String>() {
        private static final String MP4_EXTENSION = "mp4";

        @Override
        public String getKey(final Video video) {
            return video.contentId;
        }

        @Override
        public URI getUri(final Video video) {
            return video.downloadUrls.get(DownloadFormat.MP4);
        }

        @Override
        public File getFile(final File storageDirectory, final Video video) {
            final String filename = String.format("%s.%s", video.contentId, MP4_EXTENSION);
            return new File(storageDirectory, filename);
        }
    };

    /**
     * @return a {@link DownloadManager} for {@link Video} instances
     */
    public static DownloadManager<Video> createVideoDownloadManager(
            final File storageDirectory, final OkHttpClient okHttpClient) {
        return new OkHttpDownloadManager<>(storageDirectory, okHttpClient, RESOURCE_FUNCTIONS);
    }

    // Static factory methods only.
    private OkHttpVideoDownloadManager() {}
}