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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.hadoop.util.functional;

import javax.annotation.Nullable;
import java.io.IOException;
import java.io.UncheckedIOException;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.CancellationException;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CompletionException;
import java.util.concurrent.Executor;
import java.util.function.Supplier;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.apache.hadoop.util.DurationInfo;

import static org.apache.hadoop.util.functional.FutureIO.raiseInnerCause;

/**
 * A bridge from Callable to Supplier; catching exceptions
 * raised by the callable and wrapping them as appropriate.
 * @param  return type.
 */
public final class CommonCallableSupplier implements Supplier {

  private static final Logger LOG =
      LoggerFactory.getLogger(CommonCallableSupplier.class);

  private final Callable call;

  /**
   * Create.
   * @param call call to invoke.
   */
  public CommonCallableSupplier(final Callable call) {
    this.call = call;
  }

  @Override
  public T get() {
    try {
      return call.call();
    } catch (RuntimeException e) {
      throw e;
    } catch (IOException e) {
      throw new UncheckedIOException(e);
    } catch (Exception e) {
      throw new UncheckedIOException(new IOException(e));
    }
  }

  /**
   * Submit a callable into a completable future.
   * RTEs are rethrown.
   * Non RTEs are caught and wrapped; IOExceptions to
   * {@code RuntimeIOException} instances.
   * @param executor executor.
   * @param call     call to invoke
   * @param       type
   * @return the future to wait for
   */
  @SuppressWarnings("unchecked")
  public static  CompletableFuture submit(final Executor executor,
      final Callable call) {
    return CompletableFuture
        .supplyAsync(new CommonCallableSupplier(call), executor);
  }

  /**
   * Wait for a list of futures to complete. If the list is empty,
   * return immediately.
   *
   * @param futures list of futures.
   * @param  Generics Type T.
   * @throws IOException      if one of the called futures raised an IOE.
   * @throws RuntimeException if one of the futures raised one.
   */
  public static  void waitForCompletion(
      final List> futures) throws IOException {
    if (futures.isEmpty()) {
      return;
    }
    // await completion
    waitForCompletion(
        CompletableFuture.allOf(futures.toArray(new CompletableFuture[0])));
  }

  /**
   * Wait for a single of future to complete, extracting IOEs afterwards.
   *
   * @param  Generics Type T.
   * @param future future to wait for.
   * @throws IOException      if one of the called futures raised an IOE.
   * @throws RuntimeException if one of the futures raised one.
   */
  public static  void waitForCompletion(final CompletableFuture future)
      throws IOException {
    try (DurationInfo ignore = new DurationInfo(LOG, false,
        "Waiting for task completion")) {
      future.join();
    } catch (CancellationException e) {
      throw new IOException(e);
    } catch (CompletionException e) {
      raiseInnerCause(e);
    }
  }

  /**
   * Wait for a single of future to complete, ignoring exceptions raised.
   * @param future future to wait for.
   * @param  Generics Type T.
   */
  public static  void waitForCompletionIgnoringExceptions(
      @Nullable final CompletableFuture future) {
    if (future != null) {
      try (DurationInfo ignore = new DurationInfo(LOG, false,
          "Waiting for task completion")) {
        future.join();
      } catch (Exception e) {
        LOG.debug("Ignoring exception raised in task completion: ");
      }
    }
  }

  /**
   * Block awaiting completion for any non-null future passed in;
   * No-op if a null arg was supplied.
   * @param future future
   * @throws IOException      if one of the called futures raised an IOE.
   * @throws RuntimeException if one of the futures raised one.
   */
  public static void maybeAwaitCompletion(
      @Nullable final CompletableFuture future) throws IOException {
    if (future != null) {
      waitForCompletion(future);
    }
  }

}