/*
 * Copyright (C) 2003-2011 eXo Platform SAS.
 *
 * 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.exoplatform.commons.api.notification.service;

import java.util.concurrent.BlockingQueue;
import java.util.concurrent.Callable;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorCompletionService;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

import org.exoplatform.container.xml.InitParams;
import org.exoplatform.container.xml.ValueParam;

public class NotificationCompletionService {

  private final String THREAD_NUMBER_KEY = "thread-number";

  private final String ASYNC_EXECUTION_KEY = "async-execution";
  
  private final String KEEP_ALIVE_TIME = "keepAliveTime";

  private Executor executor;

  private ExecutorCompletionService<?> ecs;
  
  //store runnable to process notification
  private BlockingQueue<Runnable> workQueue = new LinkedBlockingQueue<Runnable>();

  private final int DEFAULT_THREAD_NUMBER = 1;

  private final boolean DEFAULT_ASYNC_EXECUTION = true;

  private int configThreadNumber;
  
  private int keepAliveTime;

  private boolean configAsyncExecution;
  
  public NotificationCompletionService(InitParams params) {

    //
    ValueParam threadNumberValue = params.getValueParam(THREAD_NUMBER_KEY);
    ValueParam asyncExecution = params.getValueParam(ASYNC_EXECUTION_KEY);
    ValueParam aliveTime = params.getValueParam(KEEP_ALIVE_TIME);

    //
    try {
      configThreadNumber = Integer.valueOf(threadNumberValue.getValue());
    } catch (Exception e) {
      configThreadNumber = DEFAULT_THREAD_NUMBER;
    }

    //
    try {
      keepAliveTime = Integer.valueOf(aliveTime.getValue());
    } catch (Exception e) {
      keepAliveTime = 10;
    }

    //
    try {
      configAsyncExecution = Boolean.valueOf(asyncExecution.getValue());
    } catch (Exception e) {
      configAsyncExecution = DEFAULT_ASYNC_EXECUTION;
    }
    
    int threadNumber = configThreadNumber <= 0 ? configThreadNumber : Runtime.getRuntime().availableProcessors();

    ThreadFactory threadFactory = new ThreadFactory() {
      public Thread newThread(Runnable runable) {
        Thread t = new Thread(runable, "Notification-Thread");
        t.setPriority(Thread.MIN_PRIORITY);
        return t;
      }
    };
    //
    if (configAsyncExecution) {
      executor = new ThreadPoolExecutor(threadNumber, threadNumber, keepAliveTime, 
                                              TimeUnit.SECONDS, workQueue, threadFactory);
      ((ThreadPoolExecutor) executor).allowCoreThreadTimeOut(true);
    } else {
      executor = new DirectExecutor();
    }
    //
    ecs = new ExecutorCompletionService(executor);
  }

  public void addTask(Callable callable) {
    ecs.submit(callable);
  }

  public void waitCompletionFinished() {
    try {
      if (executor instanceof ExecutorService) {
        ((ExecutorService) executor).awaitTermination(1, TimeUnit.SECONDS);
      }
    }
    catch (InterruptedException e) {
      throw new RuntimeException(e);
    }
  }

  public boolean isAsync() {
    return configAsyncExecution;
  }

  private class DirectExecutor implements Executor {

    public void execute(final Runnable runnable) {
      if (Thread.interrupted()) throw new RuntimeException();

      runnable.run();
    }
  }
}
