// Copyright 2020 The Bazel Authors. All rights reserved.
//
// 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.devtools.build.lib.bazel.repository.downloader;

import com.google.common.base.Optional;
import com.google.devtools.build.lib.events.ExtendedEventHandler;
import com.google.devtools.build.lib.vfs.Path;
import java.io.IOException;
import java.net.URI;
import java.net.URL;
import java.util.List;
import java.util.Map;

/** Interface for implementing the download of a file. */
public interface Downloader {

  /**
   * Downloads a file and writes it to the specified output path.
   *
   * <p>On failure the output file will be in an undefined state, and may or may not exist. The
   * caller is responsible for cleaning up outputs of failed downloads.
   *
   * @param urls list of mirror URLs with identical content
   * @param authHeaders map of authentication headers per URL
   * @param checksum valid checksum which is checked, or absent to disable
   * @param output path to the destination file to write
   * @throws IOException if download was attempted and ended up failing
   * @throws InterruptedException if this thread is being cast into oblivion
   */
  void download(
      List<URL> urls,
      Map<URI, Map<String, String>> authHeaders,
      Optional<Checksum> checksum,
      String canonicalId,
      Path output,
      ExtendedEventHandler eventHandler,
      Map<String, String> clientEnv)
      throws IOException, InterruptedException;
}