using Queue_3102;

/*
 * Queue for CSC 3102 Data Structures Portfolio
 * using Qtype
*/

/*
 * --REQUIRED METHODS--
 * Queue()
 * Enqueue(Qtype item)
 * Qtype Dequeue()
 * Qtype Peek()
 * int size()
 * --OPTIONAL METHODS--
 * bool IsEmpty()
 * Qtype PeekAhead(int num)
 * printArray()
*/

namespace Queue_3102
{
   
    class Queue<Qtype>
    {
        internal class QueueNode<Q> 
        {
            public QueueNode<Q>? next;
            public QueueNode<Q>? prev;
            public Q? data;

            public QueueNode(Q value, QueueNode<Q>? prev = null, QueueNode<Q>? next = null)
            {
                data = value;
                this.next = next;
                this.prev = prev;
            } 
        }

        private QueueNode<Qtype>? front, back;
        public int size;

        //default constuctor
        public Queue()
        {
            front = null;
            back = null;
            size = 0;
        }

        /*
         * Adds an item to the back of the Queue
         * @item - the value of the item you are adding
        */
        public void Enqueue(Qtype item)
        {
            var newNode = new QueueNode<Qtype>(item, null, back);
            back = newNode;
            if (size == 0)
            {
                front = newNode;
            }
            if (size != 0)
            {
                newNode.next.prev = back;
            }           
            size++;
        }

        public Qtype Dequeue()
        {
            if (size == 0)
            {
                throw new Exception("The Queue is empty");
            }
            else if (size == 1)
            {
                var node = front.data;
                front = null;
                back = null;
                size = 0;
                return node;
            }
            else
            {
                var retNode = front.data;
                front.prev.next = null;
                front = front.prev;
                size--;
                return retNode;
            }                
        }

        /*
         * Returns the value at the front of the queue
        */
        public Qtype Peek()
        {
            if (front == null || front.data == null)
            {
                throw new Exception("The queue is empty");
            }
            else
            {
                return front.data;
            }           
        }

        /* 
         * Returns the size of the queue
        */
        public int Size()
        {
            return size;
        }

        /*
         * Prints the Queue from back to front
        */
        public void PrintArray()
        {
            Console.Write("[ ");
            var node = back;
            if (node == null)
            {
                Console.Write("'null'");
            }
            else
            {
                for (int i = 0; i < size; i++)
                {
                    Console.Write(node.data + " ");
                    node = node.next;
                }
            }
            Console.WriteLine(" ]");
        }
    }
}