/*
 * Copyright (C) 2016 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.android.tools.build.apkzlib.zip.compress;

import com.android.tools.build.apkzlib.bytestorage.ByteStorage;
import com.android.tools.build.apkzlib.zip.CompressionResult;
import com.android.tools.build.apkzlib.zip.Compressor;
import com.android.tools.build.apkzlib.zip.utils.CloseableByteSource;
import com.google.common.util.concurrent.ListenableFuture;
import com.google.common.util.concurrent.SettableFuture;
import java.util.concurrent.Executor;

/**
 * A synchronous compressor is a compressor that computes the result of compression immediately and
 * never returns an uncomputed future object.
 */
public abstract class ExecutorCompressor implements Compressor {

  /** The executor that does the work. */
  private final Executor executor;

  /**
   * Compressor that delegates execution into the given executor.
   *
   * @param executor the executor that will do the compress
   */
  public ExecutorCompressor(Executor executor) {
    this.executor = executor;
  }

  @Override
  public ListenableFuture<CompressionResult> compress(
      CloseableByteSource source, ByteStorage storage) {
    final SettableFuture<CompressionResult> future = SettableFuture.create();
    executor.execute(
        () -> {
          try {
            future.set(immediateCompress(source, storage));
          } catch (Throwable e) {
            future.setException(e);
          }
        });

    return future;
  }

  /**
   * Immediately compresses a source.
   *
   * @param source the source to compress
   * @param storage a byte storage where the compressor can obtain data sources from
   * @return the result of compression
   * @throws Exception failed to compress
   */
  protected abstract CompressionResult immediateCompress(
      CloseableByteSource source, ByteStorage storage) throws Exception;
}