1 /* 2 * Copyright 2022 Google LLC 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 package com.google.android.libraries.mobiledatadownload.downloader; 17 18 import com.google.android.libraries.mobiledatadownload.DownloadException; 19 import com.google.common.util.concurrent.Futures; 20 import com.google.common.util.concurrent.ListenableFuture; 21 import com.google.errorprone.annotations.CheckReturnValue; 22 23 /** 24 * Responsible for downloading files in MDD. 25 * 26 * <p>Implement this interface to replace the MDD networking stack. 27 */ 28 public interface FileDownloader { 29 /** 30 * Start downloading the file. The download result is provided asynchronously as a {@link 31 * ListenableFuture} that resolves when the download is complete. 32 * 33 * <p>The download can be cancelled by calling {@link ListenableFuture#cancel} on the future 34 * instance returned by this method. Cancellation is best-effort and does not guarantee that the 35 * download will stop immediately, as it is impossible to stop a thread that is in the middle of 36 * reading bytes off the network. 37 * 38 * @param downloadRequest the download request. 39 * @return - A ListenableFuture representing the download state of the file. The ListenableFuture 40 * fails with {@link DownloadException} if downloading fails. 41 */ 42 @CheckReturnValue startDownloading(DownloadRequest downloadRequest)43 ListenableFuture<Void> startDownloading(DownloadRequest downloadRequest); 44 45 /** 46 * Checks if the content of url is changed. The ListenableFuture throws {@link DownloadException} 47 * when it fails. 48 */ 49 @CheckReturnValue isContentChanged( CheckContentChangeRequest checkContentChangeRequest)50 default ListenableFuture<CheckContentChangeResponse> isContentChanged( 51 CheckContentChangeRequest checkContentChangeRequest) { 52 return Futures.immediateFailedFuture(new UnsupportedOperationException("Not implemented")); 53 } 54 } 55