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/*
 * Copyright 2011,2012 Metamarkets Group Inc.
 *
 * 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 com.metamx.common.guava;

import com.google.common.base.Throwables;

import java.io.IOException;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;

/**
 */
public class ExecutorExecutingSequence implements Sequence
{
  private final Sequence sequence;
  private final ExecutorService exec;

  public ExecutorExecutingSequence(
      Sequence sequence,
      ExecutorService exec
  )
  {
    this.sequence = sequence;
    this.exec = exec;
  }

  @Override
  public  OutType accumulate(final OutType initValue, final Accumulator accumulator)
  {
    Future future = exec.submit(
        new Callable()
        {
          @Override
          public OutType call() throws Exception
          {
            return sequence.accumulate(initValue, accumulator);
          }
        }
    );
    try {
      return future.get();
    }
    catch (InterruptedException e) {
      throw Throwables.propagate(e);
    }
    catch (ExecutionException e) {
      throw Throwables.propagate(e);
    }
  }

  @Override
  public  Yielder toYielder(final OutType initValue, final YieldingAccumulator accumulator)
  {
    Future> future = exec.submit(
        new Callable>()
        {
          @Override
          public Yielder call() throws Exception
          {
            return makeYielder(sequence.toYielder(initValue, accumulator));
          }
        }
    );
    try {
      return future.get();
    }
    catch (InterruptedException e) {
      throw Throwables.propagate(e);
    }
    catch (ExecutionException e) {
      throw Throwables.propagate(e);
    }
  }

  private  Yielder makeYielder(final Yielder yielder)
  {
    return new Yielder()
    {
      @Override
      public OutType get()
      {
        return yielder.get();
      }

      @Override
      public Yielder next(final OutType initValue)
      {
        Future> future = exec.submit(
            new Callable>()
            {
              @Override
              public Yielder call() throws Exception
              {
                return makeYielder(yielder.next(initValue));
              }
            }
        );
        try {
          return future.get();
        }
        catch (InterruptedException e) {
          throw Throwables.propagate(e);
        }
        catch (ExecutionException e) {
          throw Throwables.propagate(e);
        }
      }

      @Override
      public boolean isDone()
      {
        return yielder.isDone();
      }

      @Override
      public void close() throws IOException
      {
        yielder.close();
      }
    };
  }
}