/* 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 org.activiti.engine.impl.asyncexecutor;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.atomic.AtomicBoolean;

import org.activiti.engine.ActivitiOptimisticLockingException;
import org.activiti.engine.impl.persistence.entity.JobEntity;
import org.activiti.engine.runtime.Job;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Runnable that checks the {@link Job} entities periodically for 'expired' jobs.
 * 
 * When a job is executed, it is first locked (lock owner and lock time is set).
 * A job is expired when this lock time is exceeded. This can happen when an executor 
 * goes down before completing a task.
 * 
 * This runnable will find such jobs and reset them, so they can be picked up again.
 * 
 * @author Joram Barrez
 */
public class ResetExpiredJobsRunnable implements Runnable {

  private static Logger log = LoggerFactory.getLogger(ResetExpiredJobsRunnable.class);

  protected final AsyncExecutor asyncExecutor;

  protected volatile boolean isInterrupted;
  protected final Object MONITOR = new Object();
  protected final AtomicBoolean isWaiting = new AtomicBoolean(false);

  public ResetExpiredJobsRunnable(AsyncExecutor asyncExecutor) {
    this.asyncExecutor = asyncExecutor;
  }

  public synchronized void run() {
    log.info("{} starting to reset expired jobs");
    Thread.currentThread().setName("activiti-reset-expired-jobs");

    while (!isInterrupted) {

      try {
        
        List<JobEntity> expiredJobs = asyncExecutor.getProcessEngineConfiguration().getCommandExecutor()
            .execute(new FindExpiredJobsCmd(asyncExecutor.getResetExpiredJobsPageSize()));
        
        List<String> expiredJobIds = new ArrayList<String>(expiredJobs.size());
        for (JobEntity expiredJob : expiredJobs) {
          expiredJobIds.add(expiredJob.getId());
        }
        
        if (expiredJobIds.size() > 0) {
          asyncExecutor.getProcessEngineConfiguration().getCommandExecutor().execute(
              new ResetExpiredJobsCmd(expiredJobIds));
        }
        
      } catch (Throwable e) {
        if (e instanceof ActivitiOptimisticLockingException) {
          log.debug("Optmistic lock exception while resetting locked jobs", e);
        } else {
          log.error("exception during resetting expired jobs", e.getMessage(), e);
        }
      }

      // Sleep
      try {
        
        synchronized (MONITOR) {
          if (!isInterrupted) {
            isWaiting.set(true);
            MONITOR.wait(asyncExecutor.getResetExpiredJobsInterval());
          }
        }

      } catch (InterruptedException e) {
        if (log.isDebugEnabled()) {
          log.debug("async reset expired jobs wait interrupted");
        }
      } finally {
        isWaiting.set(false);
      }
      
    }

    log.info("{} stopped resetting expired jobs");
  }

  public void stop() {
    synchronized (MONITOR) {
      isInterrupted = true;
      if (isWaiting.compareAndSet(true, false)) {
        MONITOR.notifyAll();
      }
    }
  }

  
  
}
