content: /*
   * 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.bookkeeper.common.util;
  
  import static com.google.common.util.concurrent.MoreExecutors.directExecutor;
  import static org.apache.bookkeeper.common.concurrent.FutureUtils.createFuture;
  
  import com.google.common.util.concurrent.FutureCallback;
  import com.google.common.util.concurrent.Futures;
  import com.google.common.util.concurrent.ListenableFuture;
  import java.util.concurrent.CompletableFuture;
  import java.util.function.Function;
  import lombok.AccessLevel;
  import lombok.NoArgsConstructor;
  
  /**
   * Utils to convert {@link com.google.common.util.concurrent.ListenableFuture} to
   * java {@link java.util.concurrent.CompletableFuture}.
   */
  @NoArgsConstructor(access = AccessLevel.PRIVATE)
  public final class ListenableFutures {
  
      /**
       * Convert a {@link ListenableFuture} to a {@link CompletableFuture}.
       *
       * @param listenableFuture listenable future to convert.
       * @return the completable future.
       */
      public static <T> CompletableFuture<T> fromListenableFuture(ListenableFuture<T> listenableFuture) {
          return fromListenableFuture(listenableFuture, Function.identity());
      }
  
      /**
       * Convert a {@link ListenableFuture} to a {@link CompletableFuture} and do a transformation.
       *
       * @param listenableFuture listenable future
       * @param mapFn            a map function that transform results
       * @return the completable future after transformation.
       */
      public static <T, R> CompletableFuture<R> fromListenableFuture(
          ListenableFuture<T> listenableFuture,
          Function<? super T, ? extends R> mapFn) {
          CompletableFuture<R> completableFuture = createFuture();
          Futures.addCallback(listenableFuture, new FutureCallback<T>() {
              @Override
              public void onSuccess(T result) {
                  try {
                      R uResult = mapFn.apply(result);
                      completableFuture.complete(uResult);
                  } catch (Exception e) {
                      completableFuture.completeExceptionally(e);
                  }
              }
  
              @Override
              public void onFailure(Throwable t) {
                  completableFuture.completeExceptionally(t);
              }
          }, directExecutor());
          return completableFuture;
      }
  
      /**
       * Convert a {@link ListenableFuture} to a {@link CompletableFuture} and do a transformation.
       *
       * @param listenableFuture listenable future
       * @param mapFn            a map function that transform results
       * @return the completable future after transformation.
       */
      public static <T, R> CompletableFuture<R> fromListenableFuture(
          ListenableFuture<T> listenableFuture,
          ExceptionalFunction<? super T, ? extends R> mapFn) {
          CompletableFuture<R> completableFuture = createFuture();
          Futures.addCallback(listenableFuture, new FutureCallback<T>() {
              @Override
              public void onSuccess(T result) {
                  try {
                      R uResult = mapFn.apply(result);
                      completableFuture.complete(uResult);
                  } catch (Exception e) {
                      completableFuture.completeExceptionally(e);
                  }
              }
  
              @Override
              public void onFailure(Throwable t) {
                  completableFuture.completeExceptionally(t);
              }
          }, directExecutor());
          return completableFuture;
      }
  }
  