content: /*
   * Copyright (C) 2019 The Android Open Source Project
   *
   * 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.exoplayer2.upstream;
  
  import static com.google.android.exoplayer2.util.Assertions.checkNotNull;
  
  import android.net.Uri;
  import androidx.annotation.Nullable;
  import java.io.IOException;
  import java.util.List;
  import java.util.Map;
  
  /** {@link DataSource} wrapper allowing just-in-time resolution of {@link DataSpec DataSpecs}. */
  public final class ResolvingDataSource implements DataSource {
  
    /** Resolves {@link DataSpec DataSpecs}. */
    public interface Resolver {
  
      /**
       * Resolves a {@link DataSpec} before forwarding it to the wrapped {@link DataSource}. This
       * method is allowed to block until the {@link DataSpec} has been resolved.
       *
       * <p>Note that this method is called for every new connection, so caching of results is
       * recommended, especially if network operations are involved.
       *
       * @param dataSpec The original {@link DataSpec}.
       * @return The resolved {@link DataSpec}.
       * @throws IOException If an {@link IOException} occurred while resolving the {@link DataSpec}.
       */
      DataSpec resolveDataSpec(DataSpec dataSpec) throws IOException;
  
      /**
       * Resolves a URI reported by {@link DataSource#getUri()} for event reporting and caching
       * purposes.
       *
       * <p>Implementations do not need to overwrite this method unless they want to change the
       * reported URI.
       *
       * <p>This method is <em>not</em> allowed to block.
       *
       * @param uri The URI as reported by {@link DataSource#getUri()}.
       * @return The resolved URI used for event reporting and caching.
       */
      default Uri resolveReportedUri(Uri uri) {
        return uri;
      }
    }
  
    /** {@link DataSource.Factory} for {@link ResolvingDataSource} instances. */
    public static final class Factory implements DataSource.Factory {
  
      private final DataSource.Factory upstreamFactory;
      private final Resolver resolver;
  
      /**
       * @param upstreamFactory The wrapped {@link DataSource.Factory} for handling resolved {@link
       *     DataSpec DataSpecs}.
       * @param resolver The {@link Resolver} to resolve the {@link DataSpec DataSpecs}.
       */
      public Factory(DataSource.Factory upstreamFactory, Resolver resolver) {
        this.upstreamFactory = upstreamFactory;
        this.resolver = resolver;
      }
  
      @Override
      public ResolvingDataSource createDataSource() {
        return new ResolvingDataSource(upstreamFactory.createDataSource(), resolver);
      }
    }
  
    private final DataSource upstreamDataSource;
    private final Resolver resolver;
  
    private boolean upstreamOpened;
  
    /**
     * @param upstreamDataSource The wrapped {@link DataSource}.
     * @param resolver The {@link Resolver} to resolve the {@link DataSpec DataSpecs}.
     */
    public ResolvingDataSource(DataSource upstreamDataSource, Resolver resolver) {
      this.upstreamDataSource = upstreamDataSource;
      this.resolver = resolver;
    }
  
    @Override
    public void addTransferListener(TransferListener transferListener) {
      checkNotNull(transferListener);
      upstreamDataSource.addTransferListener(transferListener);
    }
  
    @Override
    public long open(DataSpec dataSpec) throws IOException {
      DataSpec resolvedDataSpec = resolver.resolveDataSpec(dataSpec);
      upstreamOpened = true;
      return upstreamDataSource.open(resolvedDataSpec);
    }
  
    @Override
    public int read(byte[] buffer, int offset, int length) throws IOException {
      return upstreamDataSource.read(buffer, offset, length);
    }
  
    @Override
    @Nullable
    public Uri getUri() {
      @Nullable Uri reportedUri = upstreamDataSource.getUri();
      return reportedUri == null ? null : resolver.resolveReportedUri(reportedUri);
    }
  
    @Override
    public Map<String, List<String>> getResponseHeaders() {
      return upstreamDataSource.getResponseHeaders();
    }
  
    @Override
    public void close() throws IOException {
      if (upstreamOpened) {
        upstreamOpened = false;
        upstreamDataSource.close();
      }
    }
  }
  