Hitting a Moving Target: The Missile Guidance System

using System;
using System.Collections.Generic;
using System.Drawing;

namespace SimpleGuidanceSystemUI
{
	class Target : Shooter
	{
		public double DeltaTheta = Math.PI / 8.0;
		public double Acceleration = 0.5;

		public enum TurnType
		{
			Left,
			Right,
			None
		}

		public enum ThrustType
		{
			Forward,
			Backward,
			None
		}

		public Target(double pX, double pY, double vX, double vY, double Theta)
			: base(pX, pY, vX, vY, Theta)
		{
			this.pX = pX;
			this.pY = pY;
			this.vX = vX;
			this.vY = vY;
			this.Theta = (Theta + Math.PI) % (2.0 * Math.PI);
		}

		public override void OffsetX(double value)
		{
			this.offsetX += value;
			this.lastX += value;
		}

		public override void OffsetY(double value)
		{
			this.offsetY += value;
			this.lastY += value;
		}

		public void Update(TurnType Turn, ThrustType Thrust)
		{
			double deltaTheta = 0.0;
			switch (Turn)
			{
				case (TurnType.Left):
					deltaTheta = DeltaTheta;
					break;
				case (TurnType.Right):
					deltaTheta = -DeltaTheta;
					break;
			}
			switch (Thrust)
			{
				case (ThrustType.Forward):
					base.Update(Acceleration, deltaTheta, true);
					break;
				case (ThrustType.Backward):
					base.Update(-Acceleration, deltaTheta, true);
					break;
				default:
					base.Update(0.0, deltaTheta, true);
					thrusting = false;
					break;
			}
		}

		private const double DRAWSCALEFACTOR = 10.0;

		public override void DrawOn(Graphics g)
		{
			g.FillPolygon(thrusting ? Brushes.Orange : Brushes.Red, new Point[] {
				new Point((int)(this.drawX + 2.0 * DRAWSCALEFACTOR * Math.Sin(this.Theta)), (int)(this.drawY + 2.0 * DRAWSCALEFACTOR * Math.Cos(this.Theta))),
				new Point((int)(this.drawX + DRAWSCALEFACTOR * Math.Sin(this.Theta + 1.0 * Math.PI / 8.0)), (int)(this.drawY + DRAWSCALEFACTOR * Math.Cos(this.Theta + 1.0 * Math.PI / 8.0))),
				new Point((int)(this.drawX + 2.0 * DRAWSCALEFACTOR * Math.Sin(this.Theta + 3.0 * Math.PI / 8.0)), (int)(this.drawY + 2.0 * DRAWSCALEFACTOR * Math.Cos(this.Theta + 3.0 * Math.PI / 8.0))),
				new Point((int)(this.drawX + 0.7 * DRAWSCALEFACTOR * Math.Sin(this.Theta + 9.0 * Math.PI / 16.0)), (int)(this.drawY + 0.7 * DRAWSCALEFACTOR * Math.Cos(this.Theta + 9.0 * Math.PI / 16.0))),
				new Point((int)(this.drawX + DRAWSCALEFACTOR * Math.Sin(this.Theta + 3.0 * Math.PI / 4.0)), (int)(this.drawY + DRAWSCALEFACTOR * Math.Cos(this.Theta + 3.0 * Math.PI / 4.0))),
				new Point((int)(this.drawX + DRAWSCALEFACTOR * Math.Sin(this.Theta + 5.0 * Math.PI / 4.0)), (int)(this.drawY + DRAWSCALEFACTOR * Math.Cos(this.Theta + 5.0 * Math.PI / 4.0))),
				new Point((int)(this.drawX + 0.7 * DRAWSCALEFACTOR * Math.Sin(this.Theta + 23.0 * Math.PI / 16.0)), (int)(this.drawY + 0.7 * DRAWSCALEFACTOR * Math.Cos(this.Theta + 23.0 * Math.PI / 16.0))),
				new Point((int)(this.drawX + 2.0 * DRAWSCALEFACTOR * Math.Sin(this.Theta + 13.0 * Math.PI / 8.0)), (int)(this.drawY + 2.0 * DRAWSCALEFACTOR * Math.Cos(this.Theta + 13.0 * Math.PI / 8.0))),
				new Point((int)(this.drawX + DRAWSCALEFACTOR * Math.Sin(this.Theta + 15.0 * Math.PI / 8.0)), (int)(this.drawY + DRAWSCALEFACTOR * Math.Cos(this.Theta + 15.0 * Math.PI / 8.0)))
			});
			g.DrawLine(Pens.Yellow, new Point((int)this.drawX, (int)this.drawY), new Point((int)this.LastX, (int)this.LastY));
		}
	}
}