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The official Couchbase Java SDK
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/**
 * Copyright (C) 2009-2013 Couchbase, Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALING
 * IN THE SOFTWARE.
 */

package com.couchbase.client.internal;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicReference;

import net.spy.memcached.internal.AbstractListenableFuture;
import net.spy.memcached.internal.GenericCompletionListener;
import net.spy.memcached.internal.GetFuture;

/**
 * Represents the future result of a ReplicaGet operation.
 */
public class ReplicaGetFuture
  extends AbstractListenableFuture
  implements Future {

  private final long timeout;
  private AtomicReference> completedFuture;
  private final List> monitoredFutures;
  private volatile boolean cancelled = false;

  public ReplicaGetFuture(long timeout, ExecutorService service) {
    super(service);
    this.timeout = timeout;
    monitoredFutures = Collections.synchronizedList(
      new ArrayList>()
    );
    completedFuture = new AtomicReference>();
  }

  /**
   * Add a {@link GetFuture} to mointor.
   *
   * Note that this method is for internal use only.
   *
   * @param future the future to monitor.
   */
  public void addFutureToMonitor(Future future) {
    monitoredFutures.add(future);
  }

  /**
   * Mark a monitored future as complete.
   *
   * Note that this method is for internal use only. It will also cancel
   * all other registered futures.
   *
   * @param future the future to mark as completed.
   * @return true if this future is the one that will be used.
   */
  public boolean setCompletedFuture(Future future) {
    boolean firstComplete = completedFuture.compareAndSet(null, future);
    if (firstComplete) {
      cancelOtherFutures(completedFuture.get());
    }
    return firstComplete;
  }

  @Override
  public T get() throws InterruptedException, ExecutionException {
    try {
      return get(timeout, TimeUnit.MILLISECONDS);
    } catch (TimeoutException e) {
      throw new RuntimeException("Timed out waiting for operation", e);
    }
  }

  @Override
  @SuppressWarnings("unchecked")
  public T get(long userTimeout, TimeUnit unit) throws InterruptedException,
    ExecutionException, TimeoutException {
    long start = System.currentTimeMillis();
    long timeoutMs = TimeUnit.MILLISECONDS.convert(userTimeout, unit);

    while(System.currentTimeMillis() - start <= timeoutMs) {
      if (isDone() && !completedFuture.get().isCancelled()) {
        return completedFuture.get().get();
      }
    }

    throw new TimeoutException("No replica get future returned with success "
      + "before timeout.");
  }

  /**
   * Cancel all other futures that are not completed.
   *
   * @param successFuture
   */
  private void cancelOtherFutures(Future successFuture) {
    synchronized (monitoredFutures) {
      Iterator it = monitoredFutures.iterator();
      while (it.hasNext()) {
        Future future = (Future) it.next();
        if (!future.equals(successFuture)) {
          future.cancel(true);
        }
      }
    }
  }

  @Override
  public boolean cancel(boolean ign) {
    cancelled = true;
    boolean allCancelled = true;
    synchronized (monitoredFutures) {
      Iterator it = monitoredFutures.iterator();
      while (it.hasNext()) {
        Future future = (Future) it.next();
        if (!future.cancel(ign)) {
          allCancelled = false;
        }
      }
    }
    notifyListeners();
    return allCancelled;
  }

  @Override
  public boolean isCancelled() {
    return cancelled;
  }

  @Override
  public boolean isDone() {
    return completedFuture.get() != null && completedFuture.get().isDone();
  }

  @Override
  @SuppressWarnings("unchecked")
  public ReplicaGetFuture addListener(
    ReplicaGetCompletionListener listener) {
    addToListeners((GenericCompletionListener) listener);
    return this;
  }

  @Override
  @SuppressWarnings("unchecked")
  public ReplicaGetFuture removeListener(
    ReplicaGetCompletionListener listener) {
    removeFromListeners((GenericCompletionListener) listener);
    return this;
  }

  /**
   * Signals that this future is complete.
   */
  public void signalComplete() {
    notifyListeners();
  }


}