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/**
 * Copyright (c) 2013, impossibl.com
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *  * Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *  * Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *  * Neither the name of impossibl.com nor the names of its contributors may
 *    be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
/*-------------------------------------------------------------------------
 *
 * Copyright (c) 2004-2011, PostgreSQL Global Development Group
 *
 *
 *-------------------------------------------------------------------------
 */
package com.impossibl.postgres.jdbc;


import java.util.concurrent.atomic.AtomicReference;


abstract class ExecutionTimerTask implements Runnable {

  enum State {
    NotStarted,
    Running,
    Cancelling,
    Completed
  }

  private final AtomicReference state = new AtomicReference<>(State.NotStarted);
  private Thread thread;

  protected abstract void go();

  boolean isCancelled() {
    return state.get() != State.Running || thread.isInterrupted();
  }

  @Override
  public void run() {

    try {

      thread = Thread.currentThread();

      if (!state.compareAndSet(State.NotStarted, State.Running))
        return;

      go();

    }
    catch (Throwable e) {
      // Ignore...
    }
    finally {
      state.set(State.Completed);
      synchronized (state) {
        state.notify();
      }
    }

  }

  void cancel() {

    if (this.state.getAndSet(State.Cancelling) == State.Running) {

      thread.interrupt();

      synchronized (state) {

        while (state.get() == State.Cancelling) {
          try {
            state.wait();
          }
          catch (InterruptedException e) {
            // Ignore
          }
        }
      }

    }

  }

}