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

namespace lab5_prog
{
    public class BSplineCurve
    {
        int degree;
        DoublyLinkedList<ControlPoint> controlPoints;
        float[] knots;

        //BSplineCurve()
        //{
        //    controlPoints = new DoublyLinkedList<ControlPoint>
        //}

        public void draw(Graphics g)
        {

        }
        public void addControlPoint(ControlPoint controlPoint)
        {
            controlPoints.Add(controlPoint);
            UpdatesNodes();
        }
        public void deleteControlPoint(ControlPoint controlPoint)
        {
            controlPoints.Remove(controlPoint);
            UpdatesNodes();
        }
        public void changeDegree(int degree)
        {

        }
        public void clear()
        {
            controlPoints.Clear();
        }
        private void UpdatesNodes()
        {
            knots = new float[controlPoints.Count + degree + 1];
            for(int i = 0; i < controlPoints.Count + degree + 1; i++)
            {
                if(i <= degree)
                {
                    knots[i] = 0f;
                }
                if ((i > degree)&&(i < controlPoints.Count))
                {
                    knots[i] = (float)(i - degree) / (controlPoints.Count - degree);
                }
                if (i >= controlPoints.Count)
                {
                    knots[i] = 1f;
                }
            }
        }
        private PointF value(float u)
        {
            PointF point = new PointF(0, 0);

            for (int i = 0; i < controlPoints.Count; i++)
            {
                point.X += controlPoints[i].X * rec(u, i, degree + 1);
                point.Y += controlPoints[i].Y * rec(u, i, degree + 1);
            }
            return point;
        }
        private float rec(float u, int i, int k)
        {
            if(k != 1)
            {
                return (u - knots[i]) * rec(u, i, k - 1) / (knots[i + k - 1] - knots[i]) + (knots[i + k] - u)*rec(u, i + 1, k - 1)/(knots[i + k] - knots[i + 1]);
            }
            else
            {
                if(knots[i] <= u && u < knots[i+1])
                {
                    return 1f;
                }
                else
                {
                    return 0f;
                }
            }
        }
    }
}