using C_.Datastructures.Nodes;

namespace C_.Datastructures
{
    public class Stack<T>
    {
        internal StackNode<T>? Head { get; set; }
        private int Count { get; set; } = 0;

        public static Stack<T> Create(){
            //Create a new stack without a head
            return new Stack<T>();
        }

        public static Stack<T> Create(T value){
            //Create a new Stack with a head
            return new Stack<T>{
                Head = StackNode<T>.Create(value, default),
                Count = 1
            };
        }

        public void Push(T value){
            //Add an Item to the top of the stack
            Count++;
            Head = StackNode<T>.Create(value, Head);
            return;
        }

        public T? Pop(){
            //Take the item off of the top of the stack
            T? value = default;
            if (Count > 0)
            {//Assign the default value if there are any items left in the stack
                Count--;
                value = Head!.Value;
                Head = Head.Next;
                if (Count == 0)
                {
                    Head = default;
                }
            }
            return value;
        }

        public T? Peek(){
            //View item on top of the stack
            if (Count > 0)
            {
                return Head!.Value;
            }
            return default;
        }
    }
}