content: /*
   * Copyright (C) 2020 ActiveJ 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 io.activej.service;
  
  import java.util.List;
  import java.util.concurrent.CompletableFuture;
  import java.util.concurrent.CompletionStage;
  import java.util.concurrent.atomic.AtomicInteger;
  import java.util.concurrent.atomic.AtomicReference;
  
  public class Utils {
  
  	public static CompletableFuture<Void> combineAll(List<? extends CompletionStage<?>> futures) {
  		if (futures.isEmpty()) return CompletableFuture.completedFuture(null);
  		CompletableFuture<Void> result = new CompletableFuture<>();
  		AtomicInteger count = new AtomicInteger(futures.size());
  		AtomicReference<Throwable> exception = new AtomicReference<>();
  		for (CompletionStage<?> future : futures) {
  			future.whenComplete(($, e) -> {
  				if (e != null) {
  					exception.compareAndSet(null, e);
  				}
  				if (count.decrementAndGet() == 0) {
  					if (exception.get() == null) {
  						result.complete(null);
  					} else {
  						result.completeExceptionally(exception.get());
  					}
  				}
  			});
  		}
  		return result;
  	}
  
  	public static <T> CompletableFuture<T> completedExceptionallyFuture(Throwable e) {
  		CompletableFuture<T> future = new CompletableFuture<>();
  		future.completeExceptionally(e);
  		return future;
  	}
  
  }
  