/*
    * ====================================================================
    *
    *  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.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   *
   */
  
  package org.apache.http.pool;
  
  import java.io.IOException;
  import java.util.Date;
  import java.util.concurrent.ExecutionException;
  import java.util.concurrent.Future;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.TimeoutException;
  import java.util.concurrent.locks.Condition;
  import java.util.concurrent.locks.Lock;
  
  import org.apache.http.annotation.ThreadSafe;
  import org.apache.http.concurrent.FutureCallback;
  
  @ThreadSafe
  abstract class PoolEntryFuture<T> implements Future<T> {
  
      private final Lock lock;
      private final FutureCallback<T> callback;
      private final Condition condition;
      private volatile boolean cancelled;
      private volatile boolean completed;
      private T result;
  
      PoolEntryFuture(final Lock lock, final FutureCallback<T> callback) {
          super();
          this.lock = lock;
          this.condition = lock.newCondition();
          this.callback = callback;
      }
  
      public boolean cancel(boolean mayInterruptIfRunning) {
          this.lock.lock();
          try {
              if (this.completed) {
                  return false;
              }
              this.completed = true;
              this.cancelled = true;
              if (this.callback != null) {
                  this.callback.cancelled();
              }
              this.condition.signalAll();
              return true;
          } finally {
              this.lock.unlock();
          }
      }
  
      public boolean isCancelled() {
          return this.cancelled;
      }
  
      public boolean isDone() {
          return this.completed;
      }
  
      public T get() throws InterruptedException, ExecutionException {
          try {
              return get(0, TimeUnit.MILLISECONDS);
          } catch (TimeoutException ex) {
              throw new ExecutionException(ex);
          }
      }
  
      public T get(
              long timeout,
              final TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException {
          this.lock.lock();
          try {
              if (this.completed) {
                  return this.result;
              }
             this.result = getPoolEntry(timeout, unit);
             this.completed = true;
             if (this.callback != null) {
                 this.callback.completed(this.result);
             }
             return result;
         } catch (IOException ex) {
             this.completed = true;
             this.result = null;
             if (this.callback != null) {
                 this.callback.failed(ex);
             }
             throw new ExecutionException(ex);
         } finally {
             this.lock.unlock();
         }
     }
 
     protected abstract T getPoolEntry(
             long timeout, TimeUnit unit) throws IOException, InterruptedException, TimeoutException;
 
     public boolean await(final Date deadline) throws InterruptedException {
         this.lock.lock();
         try {
             if (this.cancelled) {
                 throw new InterruptedException("Operation interrupted");
             }
             boolean success = false;
             if (deadline != null) {
                 success = this.condition.awaitUntil(deadline);
             } else {
                 this.condition.await();
                 success = true;
             }
             if (this.cancelled) {
                 throw new InterruptedException("Operation interrupted");
             }
             return success;
         } finally {
             this.lock.unlock();
         }
 
     }
 
     public void wakeup() {
         this.lock.lock();
         try {
             this.condition.signalAll();
         } finally {
             this.lock.unlock();
         }
     }
 
 }