package javafoundations;
import javafoundations.exceptions.*;

public class LinkedQueue<T> implements QueueADT<T>
{
   private int count;
   private LinearNode<T> front, rear;

   /**
    * Creates an empty queue.
    */
   public LinkedQueue()
   {
      count = 0;
      front = rear = null;
   }

   /**
    * Adds the specified element to the rear of this queue.
    *
    * @param element  the element to be added to the rear of this queue
    */
   public void enqueue (T element)
   {
      LinearNode<T> node = new LinearNode<T>(element);

      if (isEmpty())
         front = node;
      else
         rear.setNext (node);

      rear = node;
      count++;
   }

   /**
    * Removes the element at the front of this queue and returns a
    * reference to it. Throws an EmptyCollectionException if the
    * queue is empty.
    *
    * @return                           the element at the front of this queue
    * @throws EmptyCollectionException  if an empty collection exception occurs
    */
   public T dequeue() throws EmptyCollectionException
   {
       if(isEmpty())
       {
           throw new EmptyCollectionException("queue");
       }
       else
       {
           front = front.getNext();
       }

       count--;
       return front.getElement();
   }

   /**
    * Returns a reference to the element at the front of this queue.
    * The element is not removed from the queue.  Throws an
    * EmptyCollectionException if the queue is empty.
    *
    * @return                            a reference to the first element in
    *                                    this queue
    * @throws EmptyCollectionsException  if an empty collection exception occurs
    */
   public T first() throws EmptyCollectionException
   {
       if(front == null)
       {
           throw new EmptyCollectionException("queue");
       }
       else
       {
           return front.getElement();
       }
   }

   /**
    * Returns true if this queue is empty and false otherwise.
    *
    * @return  true if this queue is empty and false if otherwise
    */
   public boolean isEmpty()
   {
        if(front == null)
        {
            return true;
        }
        else
        {
            return false;
        }
   }

   /**
    * Returns the number of elements currently in this queue.
    *
    * @return  the integer representation of the size of this queue
    */
   public int size()
   {
       System.out.println(count);
       return (count);
   }

   /**
    * Returns a string representation of this queue.
    *
    * @return  the string representation of this queue
    */
   public String toString()
   {
       while(front.getNext() != null)
       {
           System.out.println(front);
           front = front.getNext();
           count--;
       }
        return ("There are " + count + " elements in this queue.");
   }
}