/* Introduction a l'informatique II (ITI 1521)
 * Introduction to Computing II (ITI 1121)
 */

/**
 * Array-based implementation of a <code>Queue</code>.
 *
 * @author Marcel Turcotte
 */

import java.util.NoSuchElementException;

public class CircularQueue<E> implements Queue<E> {

	private static final int DEFAULT_CAPACITY = 100;
	private int front, rear, size;
	private E[] elems;

	public CircularQueue( int capacity ) {
		elems = (E[]) new Object[ capacity ];
		front = 0;
		rear = -1;
		size = 0;
	}

	private class QueueIterator implements Iterator<E> {
	    private int current = -1;
	    public E next() {
		if ( ! hasNext() ) {
		    throw new NoSuchElementException();
		}
		if (current == -1) {
		    current = front;
		} else {
		    current = (current + 1) % elems.length;
		}
		return elems[ current ];
	    }
	    public boolean hasNext() {
		return size != 0 && (current == -1 || current != rear);
	    }
	}

	public Iterator<E> iterator() {
	    return new QueueIterator();
	}

	public boolean isEmpty() {
		return ( size == 0 );
	}
	public void enqueue( E value ) {
		rear = ( rear+1 ) % elems.length;
		elems[ rear ] = value;
		size++;
	}
	public E dequeue() {
	    if ( isEmpty() ) {
		throw new EmptyQueueException();
	    }
	    E savedValue = elems[ front ];
	    elems[ front ] = null; // ``scrubbing''
	    size--;
	    front =  ( front+1 ) % elems.length;
	    return savedValue;
	}

	public String toString() {

	    StringBuffer str = new StringBuffer( "[" );

	    if ( size > 0 ) {

		int offset = 0;

		str.append( elems[ front ] );
		offset = offset + 1;

		while ( offset < size ) {
		    
		    str.append( ", " );
		    str.append( elems[ ( front + offset ) % elems.length ] );
		    offset = offset + 1;

		}

	    }

	    str.append( "]" );

	    return str.toString();

	}

}