/*
 * File: ZHLinkedQueue.java
 */

package zhstructures;

import java.util.Iterator;
import java.util.NoSuchElementException;

/**
 * Class implementing a ZHQueue using a one-way linked structure.
 * 
 * @author J. Andrew Holey
 * @version August 11, 2008
 */
public class ZHLinkedQueue<ElementType> implements ZHQueue<ElementType> {
	
	/**
	 * A reference to the first node in this queue.
	 */
	protected QueueNode front;
	/**
	 * A reference to the empty node at the back of this queue.
	 */
	protected QueueNode rear;
	
	/**
	 * Creates a new empty queue.
	 */
	public ZHLinkedQueue() {
		this.front = new QueueNode();
		this.rear = this.front;
	}

	/* (non-Javadoc)
	 * @see zhstructures.ZHQueue#getFirst()
	 */
	public ElementType peek() {
		if (this.isEmpty()) throw new NoSuchElementException();
		return this.front.element;
	}

	/* (non-Javadoc)
	 * @see zhstructures.ZHQueue#dequeue()
	 */
	public ElementType dequeue() {
		if (this.isEmpty()) throw new NoSuchElementException();
		ElementType result = this.front.element;
		this.front = this.front.next;
		return result;
	}

	/* (non-Javadoc)
	 * @see zhstructures.ZHStack#push(java.lang.Object)
	 */
	public void enqueue(ElementType element) {
		this.rear.element = element;
		this.rear.next = new QueueNode();
		this.rear.state = ZHComponentState.NOT_EMPTY;
		this.rear = this.rear.next;
	}

	/* (non-Javadoc)
	 * @see zhstructures.ZHCollection#contains(java.lang.Object)
	 */
	public boolean contains(ElementType element) {
		return this.front.contains(element);
	}

	/* (non-Javadoc)
	 * @see zhstructures.ZHCollection#isEmpty()
	 */
	public boolean isEmpty() {
		return this.front.isEmpty();
	}

	/* (non-Javadoc)
	 * @see zhstructures.ZHCollection#iterator()
	 */
	public Iterator<ElementType> iterator() {
		return this.front.iterator();
	}

	/**
	 * Class implementing nodes for this queue.
	 */
	protected class QueueNode extends ZHOneWayLinkedStructure<ElementType, QueueNode> {

		/**
		 * Creates a new empty queue node.
		 */
		protected QueueNode() {
			super();
		}
		
	}

}