using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Drawing.Drawing2D;

namespace TriangleClipping
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();

            pictureBox1.Resize += new EventHandler(pictureBox1_Resize);
        }

        void pictureBox1_Resize(object sender, EventArgs e)
        {
            pictureBox1.Invalidate();
        }

        private void pictureBox1_Click(object sender, EventArgs e)
        {
            _clickPosition = PointToClient(Cursor.Position);
            pictureBox1.Invalidate();
        }

        Point _clickPosition = new Point(128 / 2, 128 / 2);

        public static Point RotatePoint(PointF p, PointF p2, double angle)
        { //angle in radians.
            return new Point((int)(Math.Cos(angle) * (p.X - p2.X) - Math.Sin(angle) * (p.Y - p2.Y) + p2.X), (int)(Math.Sin(angle) * (p.X - p2.X) + Math.Cos(angle) * (p.Y - p2.Y) + p2.Y));
        }
        public static double DegreeToRadian(double angle)
        {
            return Math.PI * angle / 180.0;
        }
        public static double RadianToDegree(double angle)
        {
            return angle * 180.0 / Math.PI;
        }

        public static Point[] Triangle(int w, int h, int angle)
        {
            Point first = RotatePoint(new Point(w, h), new Point(w / 2, h / 2), DegreeToRadian(angle));
            return new Point[3] { first, RotatePoint(first, new Point(w / 2, h / 2), DegreeToRadian(120)), RotatePoint(first, new Point(w / 2, h / 2), DegreeToRadian(240)) };
        }

        public static Bitmap ColorTriangle(int angle, int size, int multisampling)
        {
            size = size * multisampling;
            using (Bitmap b = new Bitmap(size, size))
            {
                using (Graphics g = Graphics.FromImage(b))
                {
                    GraphicsPath gp = new GraphicsPath();

                    Point origin = new Point(size / 2, size / 2);
                    PointF first = new PointF(size, size / 2.0f);
                    gp.AddPolygon(new PointF[3] { first, RotatePoint(first, origin, DegreeToRadian(120)), RotatePoint(first, origin, DegreeToRadian(240)) });

                    using (PathGradientBrush pgb = new PathGradientBrush(gp))
                    {
                        pgb.SurroundColors = new Color[] { Color.Black, Color.White };
                        pgb.CenterPoint = RotatePoint(first, origin, DegreeToRadian(120));
                        pgb.CenterColor = Color.White;//ColorManager.HSVtoRGB((short)angle, (byte)100, (byte)100, (byte)255);
                        g.FillPath(pgb, gp);

                    }
                    return (Bitmap)b.Clone();// ResizeImage(rotateImage(b, (float)angle - 120), size / multisampling);

                }
            }
        }

        static PointF CenterPolygon(PointF[] points)
        {
            PointF added = new PointF();

            foreach (var p in points)
                added = new PointF(added.X + p.X, added.Y + p.Y);

            added = new PointF(added.X / points.Length, added.Y / points.Length);
            return added;
        }

        private void pictureBox1_Paint(object sender, PaintEventArgs e)
        {
            var triangle = Triangle(pictureBox1.Width, pictureBox1.Height, 6);

            e.Graphics.SmoothingMode = SmoothingMode.AntiAlias;

            e.Graphics.DrawImage(ColorTriangle(0, pictureBox1.Width / 2, 2), new Point(0, 0));

            Point origin = new Point(pictureBox1.Width / 2, pictureBox1.Width / 2);
            PointF first = new PointF(pictureBox1.Width, pictureBox1.Width / 2.0f);
            var polygon = new PointF[3] { first, RotatePoint(first, origin, DegreeToRadian(120)), RotatePoint(first, origin, DegreeToRadian(240)) };

            e.Graphics.DrawEllipse(Pens.Red, new RectangleF(PointF.Subtract(_clickPosition, new SizeF(2, 2)), new SizeF(4, 4)));

            int width = (int)(polygon[0].X - polygon[1].X);
            int height = (int)(polygon[1].Y - polygon[2].Y);

            Point offsetFromPoint = new Point((int)polygon[0].X - _clickPosition.X, (int)polygon[0].Y - _clickPosition.Y);

            int maxY = (int)(((polygon[0].X - _clickPosition.X) / (float)width) * (float)height);
            int highestY = (int)(((polygon[0].X - polygon[1].X) / (float)width) * (float)height);

            Text = highestY + " : " + maxY;

            var p = Pens.Green;
            if (offsetFromPoint.Y > maxY - (maxY / 2) ||
                offsetFromPoint.Y < -(maxY - (maxY / 2)) ||
                offsetFromPoint.X > width)
                p = Pens.Red;

            Point clippedPosition = _clickPosition;

            if (offsetFromPoint.X > width)
            {
                clippedPosition.X = (int)polygon[1].X;
                maxY = highestY;
            }

            if (offsetFromPoint.Y > maxY - (maxY / 2))
                clippedPosition.Y = (int)(polygon[0].Y - (maxY - (maxY / 2)));
            else if (offsetFromPoint.Y < -(maxY - (maxY / 2)))
                clippedPosition.Y = (int)(polygon[0].Y + (maxY - (maxY / 2)));

            e.Graphics.DrawEllipse(Pens.Red, new RectangleF(PointF.Subtract(clippedPosition, new SizeF(2, 2)), new SizeF(4, 4)));

            e.Graphics.DrawLine(p, polygon[0].X, _clickPosition.Y, polygon[0].X - width, _clickPosition.Y);
            e.Graphics.DrawLine(p, _clickPosition.X, polygon[0].Y + (height / 2), _clickPosition.X, polygon[0].Y - (height / 2));
            e.Graphics.DrawLine(p, _clickPosition.X, polygon[0].Y + (height / 2), _clickPosition.X, polygon[0].Y - (height / 2));
        }
    }
}