using System;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using C_.Datastructures.Nodes;

namespace C_.Datastructures
{
    internal class DoublyLinkedList<T>
    {
        internal DoublyLinkedListNode<T>? Head { get; set; } = default;
        internal DoublyLinkedListNode<T>? Tail { get; set; } = default;
        private int Count { get; set; } = 0;

        public static DoublyLinkedList<T> Create()
        {
            //Create a new empty list
            return new DoublyLinkedList<T>();
        }

        public static DoublyLinkedList<T> Create(T value)
        {
            //Create a new Class with a single item
            return new DoublyLinkedList<T>()
            {
                Head = DoublyLinkedListNode<T>.Create(value, null, null),
                Count = 1
            };
        }

        public T? this[int i]
        {
            get
            {
                //Check Range
                if (i >= Count) throw new System.Exception("Error! Index out of Bounds");

                //Return Value
                DoublyLinkedListNode<T>? node = Traverse(i);
                if (node != null) return node.Value;
                return default;
            }
            set
            {
                //Check Range
                if (i >= Count) throw new System.Exception("Error! Index out of Bounds");

                //Change Value
                DoublyLinkedListNode<T>? node = Traverse(i);
                node!.Value = value;
            }
        }


        private DoublyLinkedListNode<T>? Traverse()
        {
            //Return the final item in the list
            return Tail;
        }

        private DoublyLinkedListNode<T>? Traverse(int i)
        {
            //Determine whether to start at the start or end of the list
            int direction = 1;
            DoublyLinkedListNode<T>? node = Head;

            if (i > (Count/2))
            {
                direction = -1;
                node = Tail;
                i = Count - i;
            }

            if (node != null)
            {
                //continue to end of list
                for (int x = 0; x < i; x++)
                {
                    //Incomplete Traverse Functions
                }
            }
            return node;
        }
        private DoublyLinkedListNode<T>? Next(DoublyLinkedListNode<T> current)
        {
            if (current != null)
                return current.Next;

            return null;
        }

        private DoublyLinkedListNode<T>? Prev(DoublyLinkedListNode<T> current)
        {
            if (current != null)
                return current.Prev;

            return null;
        }
    }
}