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/*
* Copyright 2022 Google LLC
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.android.libraries.mobiledatadownload.downloader;
import android.net.Uri;
import androidx.annotation.VisibleForTesting;
import com.google.android.libraries.mobiledatadownload.DownloadException;
import com.google.android.libraries.mobiledatadownload.DownloadException.DownloadResultCode;
import com.google.android.libraries.mobiledatadownload.internal.logging.LogUtil;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableMap;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.errorprone.annotations.CheckReturnValue;
import java.net.MalformedURLException;
import java.util.HashMap;
import java.util.Map;
/**
* A composite {@link FileDownloader} that delegates to specific registered FileDownloaders based on
* URL scheme.
*/
public final class MultiSchemeFileDownloader implements FileDownloader {
private static final String TAG = "MultiSchemeFileDownloader";
/** Builder for {@link MultiSchemeFileDownloader}. */
public static final class Builder {
private final Map<String, FileDownloader> schemeToDownloader = new HashMap<>();
/** Associates a url scheme (e.g. "http") with a specific {@link FileDownloader} delegate. */
@CanIgnoreReturnValue
public MultiSchemeFileDownloader.Builder addScheme(String scheme, FileDownloader downloader) {
schemeToDownloader.put(
Preconditions.checkNotNull(scheme), Preconditions.checkNotNull(downloader));
return this;
}
public MultiSchemeFileDownloader build() {
return new MultiSchemeFileDownloader(this);
}
}
private final ImmutableMap<String, FileDownloader> schemeToDownloader;
/** Returns a Builder for {@link MultiSchemeFileDownloader}. */
public static Builder builder() {
return new Builder();
}
private MultiSchemeFileDownloader(Builder builder) {
this.schemeToDownloader = ImmutableMap.copyOf(builder.schemeToDownloader);
}
@Override
@CheckReturnValue
public ListenableFuture<Void> startDownloading(DownloadRequest downloadRequest) {
FileDownloader delegate;
try {
delegate = getDelegate(downloadRequest.urlToDownload());
} catch (DownloadException e) {
return Futures.immediateFailedFuture(e);
}
return delegate.startDownloading(downloadRequest);
}
@Override
@CheckReturnValue
public ListenableFuture<CheckContentChangeResponse> isContentChanged(
CheckContentChangeRequest checkContentChangeRequest) {
FileDownloader delegate;
try {
delegate = getDelegate(checkContentChangeRequest.url());
} catch (DownloadException e) {
return Futures.immediateFailedFuture(e);
}
return delegate.isContentChanged(checkContentChangeRequest);
}
/** Extract the scheme of a url string. */
@VisibleForTesting
static String getScheme(String url) throws MalformedURLException {
Uri parsed = Uri.parse(url);
if (parsed == null) {
throw new MalformedURLException("Could not parse URL.");
}
String scheme = parsed.getScheme();
if (scheme == null) {
throw new MalformedURLException("URL contained no scheme.");
}
return scheme;
}
/**
* Lookup the delegate FileDownloader that can handle a url, based on the url's scheme.
*
* @throws DownloadException If an appropriate delegate FileDownloader could not be found.
*/
FileDownloader getDelegate(String url) throws DownloadException {
String scheme;
try {
scheme = getScheme(url);
} catch (MalformedURLException e) {
LogUtil.e("%s: The download url is malformed, url = %s", TAG, url);
throw DownloadException.builder()
.setDownloadResultCode(DownloadResultCode.MALFORMED_DOWNLOAD_URL)
.setCause(e)
.build();
}
FileDownloader downloader = schemeToDownloader.get(scheme);
if (downloader == null) {
LogUtil.e(
"%s: No registered downloader supports the download url scheme, scheme = %s",
TAG, scheme);
throw DownloadException.builder()
.setDownloadResultCode(DownloadResultCode.UNSUPPORTED_DOWNLOAD_URL_SCHEME)
.build();
}
return downloader;
}
}
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