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   /*
    * Copyright 2014 The Netty Project
    *
    * The Netty Project 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:
    *
    *   https://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.netty.util.concurrent;
  
  import io.netty.util.internal.PromiseNotificationUtil;
  import io.netty.util.internal.logging.InternalLogger;
  import io.netty.util.internal.logging.InternalLoggerFactory;
  
  import static io.netty.util.internal.ObjectUtil.checkNotNull;
  import static io.netty.util.internal.ObjectUtil.checkNotNullWithIAE;
  
  /**
   * {@link GenericFutureListener} implementation which takes other {@link Promise}s
   * and notifies them on completion.
   *
   * @param <V> the type of value returned by the future
   * @param <F> the type of future
   */
  public class PromiseNotifier<V, F extends Future<V>> implements GenericFutureListener<F> {
  
      private static final InternalLogger logger = InternalLoggerFactory.getInstance(PromiseNotifier.class);
      private final Promise<? super V>[] promises;
      private final boolean logNotifyFailure;
  
      /**
       * Create a new instance.
       *
       * @param promises  the {@link Promise}s to notify once this {@link GenericFutureListener} is notified.
       */
      @SafeVarargs
      public PromiseNotifier(Promise<? super V>... promises) {
          this(true, promises);
      }
  
      /**
       * Create a new instance.
       *
       * @param logNotifyFailure {@code true} if logging should be done in case notification fails.
       * @param promises  the {@link Promise}s to notify once this {@link GenericFutureListener} is notified.
       */
      @SafeVarargs
      public PromiseNotifier(boolean logNotifyFailure, Promise<? super V>... promises) {
          checkNotNull(promises, "promises");
          for (Promise<? super V> promise: promises) {
              checkNotNullWithIAE(promise, "promise");
          }
          this.promises = promises.clone();
          this.logNotifyFailure = logNotifyFailure;
      }
  
      /**
       * Link the {@link Future} and {@link Promise} such that if the {@link Future} completes the {@link Promise}
       * will be notified. Cancellation is propagated both ways such that if the {@link Future} is cancelled
       * the {@link Promise} is cancelled and vise-versa.
       *
       * @param future    the {@link Future} which will be used to listen to for notifying the {@link Promise}.
       * @param promise   the {@link Promise} which will be notified
       * @param <V>       the type of the value.
       * @param <F>       the type of the {@link Future}
       * @return          the passed in {@link Future}
       */
      public static <V, F extends Future<V>> F cascade(final F future, final Promise<? super V> promise) {
          return cascade(true, future, promise);
      }
  
      /**
       * Link the {@link Future} and {@link Promise} such that if the {@link Future} completes the {@link Promise}
       * will be notified. Cancellation is propagated both ways such that if the {@link Future} is cancelled
       * the {@link Promise} is cancelled and vise-versa.
       *
       * @param logNotifyFailure  {@code true} if logging should be done in case notification fails.
       * @param future            the {@link Future} which will be used to listen to for notifying the {@link Promise}.
       * @param promise           the {@link Promise} which will be notified
       * @param <V>               the type of the value.
       * @param <F>               the type of the {@link Future}
       * @return                  the passed in {@link Future}
       */
      @SuppressWarnings({"unchecked", "rawtypes"})
      public static <V, F extends Future<V>> F cascade(boolean logNotifyFailure, final F future,
                                                       final Promise<? super V> promise) {
          promise.addListener(new FutureListener() {
              @Override
              public void operationComplete(Future f) {
                  if (f.isCancelled()) {
                      future.cancel(false);
                  }
             }
         });
         future.addListener(new PromiseNotifier(logNotifyFailure, promise) {
             @Override
             public void operationComplete(Future f) throws Exception {
                 if (promise.isCancelled() && f.isCancelled()) {
                     // Just return if we propagate a cancel from the promise to the future and both are notified already
                     return;
                 }
                 super.operationComplete(future);
             }
         });
         return future;
     }
 
     @Override
     public void operationComplete(F future) throws Exception {
         InternalLogger internalLogger = logNotifyFailure ? logger : null;
         if (future.isSuccess()) {
             V result = future.get();
             for (Promise<? super V> p: promises) {
                 PromiseNotificationUtil.trySuccess(p, result, internalLogger);
             }
         } else if (future.isCancelled()) {
             for (Promise<? super V> p: promises) {
                 PromiseNotificationUtil.tryCancel(p, internalLogger);
             }
         } else {
             Throwable cause = future.cause();
             for (Promise<? super V> p: promises) {
                 PromiseNotificationUtil.tryFailure(p, cause, internalLogger);
             }
         }
     }
 }