package queue;

import exceptions.EmptyQueueException;

/**
 * Created with xgiovio.macbookair.
 * User: xgiovio
 * Date: 10/03/14
 * Time: 15:49
 */
public class ArrayQueue<E> implements Queue<E> {

      public ArrayQueue(){
          queue = (E[])new Object[def_size];
      }

    public ArrayQueue(int in_size){
        queue = (E[])new Object[in_size];
    }


    @Override
    public void enqueue(E element) {
            if (front == -1){
                front++;
            }
            if ( rear == mod( front - 1,queue.length) ){
                //reallocate;
                E[] new_queue = (E[]) new Object[queue.length * 2];
                for (int i= 0 ;i<(queue.length -1); i++){
                    new_queue[i] = queue[(front + i) % queue.length];
                }
                rear = queue.length - 1;
                front = 0;
                queue = new_queue;
                queue[rear]= element;
                rear = (rear + 1) % queue.length;

            }  else {
                queue[rear]= element;
                rear = (rear + 1) % queue.length;
            }

    }

    @Override
    public E dequeue() throws EmptyQueueException {

        if (front == -1){
            throw new EmptyQueueException();
        }else{
            E temp = queue[front];
            front = (front + 1)%queue.length;
            if (front == rear){
                front = -1;
                rear = 0;
            }
            return temp;
        }


    }

    @Override
    public E front() throws EmptyQueueException {
        if (front == -1){
            throw new EmptyQueueException();
        }else{
            return queue[front];
        }
    }

    @Override
    public boolean isEmpty() {
        if (size() == 0){
             return true;
        }else{
             return false;
        }
    }


    @Override
    public int size() {
        if (front == -1){
            return 0;
        }
        if (front < rear){
              return (rear - front);
        }else{
            return (queue.length - (front - rear));
        }
    }

    @Override
    public String toString() {
        String to_return = "";
        to_return = to_return + "[";
        for (int i = 0;i<size();i++){
            if ( ((i+front)%queue.length) == mod(rear - 1,queue.length)){
                to_return+=(queue[(i+front)%queue.length].toString());
            }else{
                to_return+=(queue[(i+front)%queue.length].toString() + ",");
            }
        }
        to_return = to_return + "]";

        return to_return;
    }

    private int mod(int a,int b){
        return (((a % b) + b) % b);
    }

    int def_size = 100;
    E[] queue ;
    int front = -1;
    int rear = 0;


}