/* Program extracts from Chapter 3 of
   "Data Structures and Program Design in C++"
   by Robert L. Kruse and Alexander J. Ryba
   Copyright (C) 1999 by Prentice-Hall, Inc.  All rights reserved.
   Extracts from this file may be used in the construction of other programs,
   but this code will not compile or execute as given here. */

#include "utility.h"
#include <cstdlib>
// Section 3.1:


typedef double Queue_entry;

// Section 3.3:

const int maxqueue = 10; //  small value for testing

class Queue {
public:
   Queue();
   bool empty() const;
   Error_code serve();
   Error_code append(const Queue_entry &item);
   Error_code retrieve(Queue_entry &item) const;

protected:
   int count;
   int front, rear;
   Queue_entry entry[maxqueue];
};


Queue::Queue()
/*
Post: The Queue is initialized to be empty.
*/
{
   count = 0;
   rear = maxqueue - 1;
   front = 0;
}


bool Queue::empty() const
/*
Post: Return true if the Queue is empty, otherwise return false.
*/
{
   return count == 0;
}


Error_code Queue::append(const Queue_entry &item)
/*
Post: item is added to the rear of the Queue. If the Queue is full
return an Error_code of overflow and leave the Queue unchanged.
*/

{
   if (count >= maxqueue) return overflow;
   count++;
   rear = ((rear + 1) == maxqueue) ? 0 : (rear + 1);
   //rear = (rear + 1) % maxqueue;
   entry[rear] = item;
   return success;
}


Error_code Queue::serve()
/*
Post: The front of the Queue is removed. If the Queue
is empty return an Error_code of underflow.
*/

{
   if (count <= 0) return underflow;
   count--;
   front = ((front + 1) == maxqueue) ? 0 : (front + 1);
   return success;
}


Error_code Queue::retrieve(Queue_entry &item) const
/*
Post: The front of the Queue retrieved to the output
      parameter item. If the Queue is empty return an Error_code of underflow.
*/

{
   if (count <= 0) return underflow;
   item = entry[front];
   return success;
}




class Extended_queue: public Queue {
public:
   bool full() const;
   int size() const;
   void clear();
   Error_code serve_and_retrieve(Queue_entry &item);
};

int Extended_queue::size() const
/*
Post:   Return the number of entries in the Extended_queue.
*/
{
   return count;
}

bool Extended_queue::full() const
{
	return (count == maxqueue);
}

void Extended_queue::clear()
{
	count = 0;
	rear = maxqueue - 1;
    front = 0;
	
	for(int i = 0; i < maxqueue; i++)
		entry[i] = NULL;

}

Error_code Extended_queue::serve_and_retrieve(Queue_entry &item)
{
	if (count <= 0) 
		return underflow;

	count--;
	front = ((front + 1) == maxqueue) ? 0 : (front + 1);
    item = entry[front];
	return success;
}