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This project contains utility classes that are used by various products and projects inside Atlassian and may have some utility to the world at large.

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/**
 * Copyright 2008 Atlassian Pty Ltd
 *
 * 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 io.atlassian.util.concurrent;

import net.jcip.annotations.ThreadSafe;

import java.util.concurrent.Callable;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.FutureTask;
import java.util.function.Function;

import static java.util.Objects.requireNonNull;

@ThreadSafe public class ConcurrentOperationMapImpl implements ConcurrentOperationMap {

  private final ConcurrentMap> map = new ConcurrentHashMap>();
  private final Function, CallerRunsFuture> futureFactory;

  /**
   * Constructor for ConcurrentOperationMapImpl.
   */
  public ConcurrentOperationMapImpl() {
    this(CallerRunsFuture::new);
  }

  ConcurrentOperationMapImpl(final Function, CallerRunsFuture> futureFactory) {
    this.futureFactory = requireNonNull(futureFactory, "futureFactory");
  }

  /** {@inheritDoc} */
  public final R runOperation(final K key, final Callable operation) throws ExecutionException {
    CallerRunsFuture future = map.get(key);
    while (future == null) {
      map.putIfAbsent(key, futureFactory.apply(operation));
      future = map.get(key);
    }
    try {
      return future.get();
    } finally {
      map.remove(key, future);
    }
  }

  static class CallerRunsFuture extends FutureTask {
    CallerRunsFuture(final Callable callable) {
      super(callable);
    }

    @Override public T get() throws ExecutionException {
      run();
      try {
        return super.get();
      } catch (final InterruptedException e) {
        // /CLOVER:OFF
        // how to test?
        throw new RuntimeInterruptedException(e);
        // /CLOVER:ON
      } catch (final ExecutionException e) {
        final Throwable cause = e.getCause();
        if (cause instanceof RuntimeException) {
          throw (RuntimeException) cause;
        } else if (cause instanceof Error) {
          throw (Error) cause;
        } else {
          throw e;
        }
      }
    }
  }
}