using C_.Datastructures.BinarySearchTree;
using System;

namespace C_.Datastructures.BinarySearchTree
{
    internal class Tree<T> where T:IComparable
    {
        public TreeNode<T>? Root { get; set; }
        public int Count { get; set; }

        public static Tree<T> Create(){
            //Create a new Tree with no Head
            return new Tree<T>{
                Root = null,
                Count = 0
            };
        }

        public static Tree<T> Create(T value){
            //Create a new Tree with Head
            return new Tree<T>{
                Root = TreeNode<T>.Create(value)
            };
        }

        public void Add(T value)
        {//Add item to the correct position in the tree (Input cannot be null)
            Count++;

            if (Root == default)
            {//If new node should become the root
                Root = TreeNode<T>.Create(value);
                return;
            }

            //Find position to insert
            TreeNode<T> node = Root;
            node = Descend(value, node)!;

            if (value.CompareTo(node.Value) < 0)
            {//Insert to left
                node.Left = TreeNode<T>.Create(value);
                return;
            }
            //Insert to right
            node.Right = TreeNode<T>.Create(value);
            return;
        }

        public bool Find(T value)
        {//Return true if the item can be found within the tree
            if (Root == default || Root.Value!.Equals(default))
                return false;

            TreeNode<T>? current = Root;

            while (current != default)
            {
                //Compare value at node to see if we are looking for the root item
                if (current.Value!.Equals(value))
                    return true;

                current = Traverse(value, current);
            }
            return false;
        }

        private TreeNode<T>? Traverse(T value, TreeNode<T> node)
        {//T is comparable so use methods to determine which way to traverse
            if(node == default)
                return default;

            if (value.CompareTo(node.Value) < 0)
            {//Traverse Left
                return node.Left;
            }
            //Traverse Right
            return node.Right;
        }

        private TreeNode<T>? Descend(T value, TreeNode<T>? current)
        {//Keep trying to determine whether to go left or right until null node is found that can be appended to
            if (current == default)
                return default;

            TreeNode<T>? node;

            node = Descend(value, Traverse(value, current));
            if (node == null)
            {
                return current;
            }
            return node;
        } 
    }
}