using Stack_3102;


/*
 * Stack Data Structure for CSC 3102 Protfolio
 * Using Linked List as underlying imlementation
 * using Stype
*/

/*
 * --REQUIRED METHODS--
 * Stack()
 * Push(Stype item)
 * Stype Pop()
 * Stype Peek()
 * Size()
 * --OPTIONAL METHODS--
 * bool isEmpty()
 * override ToString() or printArray()
*/


namespace Stack_3102
{
    public class StackNode<T>
    {
        public T? data;
        public StackNode<T>? prev;

        public StackNode()
        {
            data = default;
            prev = null;
        }

        public StackNode(T value, StackNode<T>? prev = null)
        {
            this.data = value;
            this.prev = prev;
        }
    }

    public class Stack<Stype>
    {

        public StackNode<Stype>? top;
        public int size;

        //default constructor
        public Stack()
        {
            top = null;
            size = 0;
        }

        /*
         * Adds a new node to the top of the stack
         * @item - the data you are adding
        */
        public void Push(Stype item)
        {
            if (top == null)
            {
                var newTop = new StackNode<Stype>(item);
                top = newTop;
            }
            else
            {
                var newNode = new StackNode<Stype>(item, top);
                top = newNode;
            }            
            size++;
        }

        /*
         * Removes the node at the top of the stack
        */
        public Stype Pop()
        {
            if (top == null)
            {
                throw new Exception("Stack is empty");
            }
            var remItem = top.data;
            top = top.prev;
            size--;
            return remItem;
        }

        /*
         * Returns the data at the top of the stack
        */
        public Stype Peek()
        {
            if (top == null)
            {
                throw new Exception("There is no top value, bc stack is empty");
            }
            return top.data;
        }

        //returns the size of the stack
        public int Size()
        {
            return size;
        }

        bool isEmpty()
        {
            if (top == null)
            {
                return true;
            }
            else
            {
                return false;
            }
        }



        //prints the stack, starting with the top value
        public void PrintStack()
        {
            if (this.isEmpty())
            {
                Console.WriteLine("The stack is empty");
                return;
            }
            var travNode = this.top; 
            Console.Write("[");
            for (int i = 0; i < size; i++)
            {
                if (travNode.data != null)
                {
                    Console.Write(travNode.data + " ");
                }
                travNode = travNode.prev;
            }
            Console.WriteLine("]");
            Console.WriteLine("Printed from the top down");
        }
    }
}