using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Windows.Forms;

namespace GravityBalls
{
    public class WorldModel
    {
        public double BallX;
        public double BallY;
        public double BallRadius;
        public double WorldWidth;
        public double WorldHeight;
        public Color BallColor;
        public int CursorX;
        public int CursorY;

        Random rnd = new Random();

        public double horizontalSpeed = 400.0;
        public double verticalSpeed = 400.0;

        public double coefficientResistance = 0.7;
        public double coefficientAttraction = 0.2;

        public void SimulateTimeframe(double dt)
        {
            BallX = Math.Max(BallRadius, Math.Min(BallX + CalculateHorizontalSpeed(horizontalSpeed) * dt, WorldWidth - BallRadius));
            BallY = Math.Max(BallRadius, Math.Min(BallY + CalculateVerticalSpeed(verticalSpeed) * dt, WorldHeight - BallRadius));
            if (BallX >= WorldWidth - BallRadius || BallX <= BallRadius)
            {
                BallColor = GetRandomColor();
                horizontalSpeed *= -1;
            }
            if (BallY >= WorldHeight - BallRadius || BallY <= BallRadius)
            {
                BallColor = GetRandomColor();
                verticalSpeed *= -1;
            }
        }

        private double CalculateHorizontalSpeed(double speed)
        {
            return speed * coefficientResistance + 20 / GetDistanceToCursor();
        }

        private double CalculateVerticalSpeed(double speed)
        {
            if (speed >= 0)
                return speed * coefficientResistance * (1 + coefficientAttraction) + 20 / GetDistanceToCursor();
            return speed * coefficientResistance * (1 - coefficientAttraction) + 20 / GetDistanceToCursor();
        }

        private Color GetRandomColor()
        {
            return Color.FromArgb(rnd.Next() % 255, rnd.Next() % 255, rnd.Next() % 255);
        }

        private double GetDistanceToCursor()
        {
            return Math.Sqrt((CursorX - BallX) * (CursorX - BallX) + (CursorY - BallY) * (CursorY - BallY));
        }
    }
}