Elephant/elephant/src/main/java/org/turro/queue/Tasks.java

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/*
 * Turró i Cutiller Foundation. License notice.
 * Copyright (C) 2015 Lluis Turró Cutiller <http://www.turro.org/>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
package org.turro.queue;
 
import java.util.Iterator;
import org.amic.util.date.CheckDate;
import org.turro.elephant.context.Application;
 
public class Tasks implements Runnable {
  
  private static final int MINUTES_OLD = 15;
  private static final long WAIT_BEFORE_STOP = 1000 * 60 * 60;
  
  private final TaskQueue queue;
  private Thread execution;
  private long startExecution;
 
  public static void execute() {
    getInstance().doExecute();
  }
  
  public static void add(Task task) {
    Tasks tasks = getInstance();
    tasks.doAdd(task);
    tasks.doExecute();
  }
  
  public static TaskQueue tasks() {
    return getInstance().queue;
  }
  
  public static boolean isInterrupted() {
    Thread t = getInstance().execution;
    return t == null || t.isInterrupted();
  }
  
  private static Tasks getInstance() {
    Application app = Application.getApplication();
    Tasks tasks = (Tasks) app.getConstructor().getSessionAttribute("elephant_task_queue");
    if(tasks == null) {
      tasks = new Tasks();
      app.getConstructor().setSessionAttribute("elephant_task_queue", tasks);
    }
    return tasks;
  }
  
  private Tasks() {
    this.queue = new TaskQueue();
  }
  
  private void doAdd(Task task) {
    queue.add(task);
  }
  
  private void doExecute() {
    if(execution == null || !execution.isAlive()) {
      startExecution = System.currentTimeMillis();
      execution = new Thread(this);
      execution.start();
    } else if((System.currentTimeMillis() - startExecution) > WAIT_BEFORE_STOP) {
      execution.interrupt();
    }
  }
  
  @Override
  public void run() {
    Iterator<Task> tasks = queue.iterator();
    while(tasks.hasNext()) {
      Task task = tasks.next();
      if(task.getStatus().equals(TaskStatus.TASK_EXECUTING)) {
        break;
      } else if(task.getStatus().equals(TaskStatus.TASK_PENDING)) {
        task.execute();
        break;
      } else if(task.getStatus().equals(TaskStatus.TASK_FAILED)) {
        if(task.isReintent()) {
          task.execute();
          break;
        } else if(isOld(task)) {
          tasks.remove();
        }
      } else {
        if(isOld(task)) {
          tasks.remove();
        }
      }
    }
  }
 
  private boolean isOld(Task task) {
    return task.getExecution().before(new CheckDate().addMinutes(-MINUTES_OLD).getDate());
  }
 
}