/*

  * This software is licensed under the Apache License, Version 2.0

  * (the "License") agreement; 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 net.admin4j.util;

 import java.util.concurrent.atomic.AtomicBoolean;

 import java.util.concurrent.atomic.AtomicLong;

 import net.admin4j.deps.commons.lang3.Validate;

 import org.slf4j.Logger;

 import org.slf4j.LoggerFactory;

 /**

  * Generic Daemon worker thread that iterates through a work/sleep cycle forever.

  * @author D. Ashmore

  *

  */

 public class Daemon extends Thread {

     private static final AtomicBoolean jvmInShutdown = new AtomicBoolean(false);

     static {

         Runtime.getRuntime().addShutdownHook(new DaemonShutdownHook());

     }

     private Runnable task;

     static final long DEFAULT_SLEEP_TIME_IN_MILLIS = 600000;   // 10 minutes

     private final AtomicLong sleepTime = new AtomicLong(DEFAULT_SLEEP_TIME_IN_MILLIS);

     protected Logger logger = LoggerFactory.getLogger(this.getClass());

     public Daemon(Runnable task, String threadName) {        

         this(task, threadName, (Long)null);

     }

     /**

      * @Deprecated Use Long constructor instead

      * @param task

      * @param threadName

      * @param sleepTimeInMillis

      */

     public Daemon(Runnable task, String threadName, Integer sleepTimeInMillis) {

         this(task, threadName, sleepTimeInMillis == null ? (Long)null: sleepTimeInMillis.longValue());

     }

     public Daemon(Runnable task, String threadName, Long sleepTimeInMillis) {        

         Validate.notNull(task, "Null task not allowed.");

         Validate.notEmpty(threadName, "Null or blank threadName not allowed.");

         this.setDaemon(true);

         this.setName(threadName);

         if (sleepTimeInMillis != null && sleepTimeInMillis > 0) {

             this.sleepTime.set(sleepTimeInMillis);

         }

         this.task = task;

         this.start();

     }

     /* (non-Javadoc)

      * @see java.lang.Thread#run()

      */

     @Override

     public void run() {

         try

         {

             while (true)

             {

                 Thread.sleep(sleepTime.get());

                 try {this.task.run();}

                 catch (Throwable t)

                 {

                     logger.error(this.getName() + " errored out.", t);

                 }

             }

         }

         catch (Throwable t)

         {

             if ( !getJvminshutdown().get() ) {

                 logger.error(this.getName() + " restarted.", t);

                 this.start();

             }

         }

     }

     public Runnable getTask() {

         return task;

     }

     static AtomicBoolean getJvminshutdown() {

         return jvmInShutdown;

     }

 }

 class DaemonShutdownHook extends Thread {

     @Override

     public void run() {

         Daemon.getJvminshutdown().set(true);

     }

 }