/*
 * 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
 *
 *   https://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 org.apache.accumulo.tserver;

import static java.util.Objects.requireNonNull;

import java.util.concurrent.ConcurrentHashMap;

import org.apache.accumulo.core.dataImpl.KeyExtent;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class ActiveAssignmentRunnable implements Runnable {
  private static final Logger log = LoggerFactory.getLogger(ActiveAssignmentRunnable.class);

  private final ConcurrentHashMap<KeyExtent,RunnableStartedAt> activeAssignments;
  private final KeyExtent extent;
  private final Runnable delegate;

  // Make sure that the other thread calling getException will see the assignment by the thread
  // calling run()
  private volatile Thread executingThread;

  public ActiveAssignmentRunnable(ConcurrentHashMap<KeyExtent,RunnableStartedAt> activeAssignments,
      KeyExtent extent, Runnable delegate) {
    this.activeAssignments = requireNonNull(activeAssignments);
    this.extent = requireNonNull(extent);
    this.delegate = requireNonNull(delegate);
  }

  @Override
  public void run() {
    if (activeAssignments.containsKey(extent)) {
      throw new IllegalStateException("Active assignment already exists for " + extent);
    }

    executingThread = Thread.currentThread();

    try {
      RunnableStartedAt runnableWithStartTime =
          new RunnableStartedAt(this, System.currentTimeMillis());
      log.trace("Started assignment for {} at {}", extent, runnableWithStartTime.getStartTime());
      activeAssignments.put(extent, runnableWithStartTime);
      delegate.run();
    } finally {
      if (log.isTraceEnabled()) {
        // Avoid the call to currentTimeMillis if we'd just throw it away anyways
        log.trace("Finished assignment for {} at {}", extent, System.currentTimeMillis());
      }
      activeAssignments.remove(extent);
    }
  }

  public Exception getException() {
    final Exception e = new Exception("Assignment of " + extent);
    if (executingThread != null) {
      e.setStackTrace(executingThread.getStackTrace());
    }
    return e;
  }
}
