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Java client for Arcus memcached
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/*
 * arcus-java-client : Arcus Java client
 * Copyright 2010-2014 NAVER Corp.
 *
 * 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 net.spy.memcached.internal;

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutionException;
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.MemcachedConnection;
import net.spy.memcached.OperationTimeoutException;
import net.spy.memcached.ops.CollectionOperationStatus;
import net.spy.memcached.ops.Operation;
import net.spy.memcached.ops.OperationState;

/**
 * Managed future for collection operations.
 *
 * Not intended for general use.
 *
 * @param  Type of object returned from this future.
 */
public class CollectionFuture implements Future {

  protected final CountDownLatch latch;
  protected final AtomicReference objRef;
  protected final long timeout;
  protected Operation op;
  protected CollectionOperationStatus opStatus;

  public CollectionFuture(CountDownLatch l, long opTimeout) {
    this(l, new AtomicReference(null), opTimeout);
  }

  public CollectionFuture(CountDownLatch l, AtomicReference oref,
                          long opTimeout) {
    super();
    latch = l;
    objRef = oref;
    timeout = opTimeout;
  }

  public boolean cancel(boolean ign) {
    assert op != null : "No operation";
    op.cancel("by application.");
    // This isn't exactly correct, but it's close enough.  If we're in
    // a writing state, we *probably* haven't started.
    return op.getState() == OperationState.WRITE_QUEUED;
  }

  public T get() throws InterruptedException, ExecutionException {
    try {
      return get(timeout, TimeUnit.MILLISECONDS);
    } catch (TimeoutException e) {
      throw new OperationTimeoutException(e);
    }
  }

  public T get(long duration, TimeUnit units)
          throws InterruptedException, TimeoutException, ExecutionException {
    if (!latch.await(duration, units)) {
      // whenever timeout occurs, continuous timeout counter will increase by 1.
      MemcachedConnection.opTimedOut(op);
      throw new CheckedOperationTimeoutException(duration, units, op);
    } else {
      // continuous timeout counter will be reset
      MemcachedConnection.opSucceeded(op);
    }
    if (op != null && op.hasErrored()) {
      throw new ExecutionException(op.getException());
    }
    if (op != null && op.isCancelled()) {
      throw new ExecutionException(new RuntimeException(op.getCancelCause()));
    }

    return objRef.get();
  }

  public void set(T o, CollectionOperationStatus status) {
    objRef.set(o);
    opStatus = status;
  }

  public void setOperation(Operation to) {
    op = to;
  }

  public boolean isCancelled() {
    assert op != null : "No operation";
    return op.isCancelled();
  }

  public boolean isDone() {
    assert op != null : "No operation";
    return latch.getCount() == 0 ||
            op.isCancelled() || op.getState() == OperationState.COMPLETE;
  }

  public CollectionOperationStatus getOperationStatus() {
    return (op.getState() == OperationState.COMPLETE) ? opStatus : null;
  }

}