Next Smaller Node

public Node getNextSmaller(Node r)
        {
            Node t = root;
            Node gp = root;
            Node p = root;
            t = root;

            while (t != null && !r.Equals(t))
            {
                gp = p;
                p = t;
                if (r.CompareTo(t) < 0)
                {
                    t = t.Left;

                }
                else
                {
                    t = t.Right;
                }

            }
            if (t.Data == this.getMin()) return null;
            if (t.Left == null && p.Data < t.Data) return p;
            if (t.Left == null && p.Data > t.Data) return gp;
            if (t.Left != null && t.Left.Right != null)
            {
                t = t.Left.Right;
                while (t.Right != null)
                {
                    t = t.Right;
                }
                return t;
            }
            if (t.Left != null && t.Left.Right == null) return t.Left;

            return null;
        }