using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Generics.BinaryTrees
{
    public class BinaryTree<T> : IEnumerable<T> where T : IComparable, new()
    {
        private BinaryNode<T> Top;

        public BinaryNode<T> Left => Top.Left;

        public BinaryNode<T> Right => Top.Right;

        public T Value => Top.Value;

        public BinaryTree(T value)
        {
            Top = new BinaryNode<T>(value);
        }

        public BinaryTree()
        {
            Top = null;
        }

        private void AddHelper(ref BinaryNode<T> node, T value)
        {
            if (node == null)
            {
                var newNode = new BinaryNode<T>(value);
                node = newNode;
                return;
            }
            if (value.CompareTo(node.Value) <= 0)
            {
                AddHelper(ref node.Left, value);
                return;
            }
            if (value.CompareTo(node.Value) > -1)
            {
                AddHelper(ref node.Right, value);
                return;
            }

        }
        public void Add(T value)
        {
            AddHelper(ref Top,value);
        }

        public IEnumerator<T> GetEnumerator()
        {
            if (Top == null) yield break;

            var stack = new Stack<BinaryNode<T>>();
            var node = Top;

            while (stack.Count > 0 || node != null)
            {
                if (node == null)
                {
                    node = stack.Pop();
                    yield return node.Value;
                    node = node.Right;
                }
                else
                {
                    stack.Push(node);
                    node = node.Left;
                }
            }
        }

        IEnumerator IEnumerable.GetEnumerator()
        {
            return GetEnumerator();
        }
    }

    public class BinaryNode<T> where T : IComparable
    {
        public T Value;
        public BinaryNode(T value)
        {
            Value = value;
        }

        public BinaryNode<T> Left;

        public BinaryNode<T> Right;
    }

    public class BinaryTree
    {
        public static BinaryTree<T> Create<T>(params T[] items) where T : IComparable, new()
        {
            var result = new BinaryTree<T>();
            foreach (var item in items)
            {
                result.Add(item);
            }

            return result;
        }
    }
}