/*
 * JBoss, Home of Professional Open Source
 * Copyright 2011, Red Hat, Inc. and individual contributors
 * by the @authors tag. See the copyright.txt in the distribution for a
 * full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */

package org.mobicents.protocols.ss7.scheduler;

/**
 * Implements queue of tasks.
 *
 *
 * @author kulikov
 */
public class OrderedTaskQueue {
    // inner holder for tasks
    private ConcurrentLinkedList<Task>[] taskList = new ConcurrentLinkedList[2];

    private Integer activeIndex = 0;

    public OrderedTaskQueue() {
        // intitalize task list
        taskList[0] = new ConcurrentLinkedList<Task>();
        taskList[1] = new ConcurrentLinkedList<Task>();
    }

    /**
     * Shows if this queue is empty.
     *
     * @return true if queue is currently empty
     */
    public boolean isEmpty() {
        return taskList[activeIndex].isEmpty();
    }

    /**
     * Queues specified task using tasks dead line time.
     *
     * @param task the task to be queued.
     * @return TaskExecutor for the scheduled task.
     */
    public void accept(Task task) {
        if ((activeIndex + 1) % 2 == 0) {
            if (!task.isInQueue0()) {
                taskList[0].offer(task);
                task.storedInQueue0();
            }
        } else {
            if (!task.isInQueue1()) {
                taskList[1].offer(task);
                task.storedInQueue1();
            }
        }
    }

    /**
     * Retrieves the task with earliest dead line and removes it from queue.
     *
     * @return task which has earliest dead line
     */
    public Task poll() {
        Task result = taskList[activeIndex].poll();
        if (result != null) {
            if (activeIndex == 0)
                result.removeFromQueue0();
            else
                result.removeFromQueue1();
        }

        return result;
    }

    public void changePool() {
        activeIndex = (activeIndex + 1) % 2;
    }

    /**
     * Clean the queue.
     */
    public void clear() {
        taskList[0].clear();
        taskList[1].clear();
    }

    /**
     * Gets the size of this queue.
     *
     * @return the size of the queue.
     */
    public int size() {
        return taskList[activeIndex].size();
    }

    protected void remove(Task task) {
        if (task.isInQueue0()) {
            taskList[0].remove(task);
            task.removeFromQueue0();
        }

        if (task.isInQueue1()) {
            taskList[1].remove(task);
            task.removeFromQueue1();
        }
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append("Queue[");

        int len = Math.min(30, taskList[activeIndex].size());
        for (int i = 0; i < len - 1; i++) {
            // sb.append(taskList[activeIndex].get(i).getPriority());
            sb.append(",");
        }

        // if(!taskList[activeIndex].isEmpty())
        // sb.append(taskList[activeIndex].get(len - 1).getPriority());
        sb.append("]");
        return sb.toString();
    }
}