// KAMTori.java
// This applet implements a nearly integrable system in action-angle
// variables and does a polar plot of theta_1 vs omega_1/omega_2 in the
// section of omega_2==0.

import java.awt.*;
import java.applet.*;

public class KAMTori extends Applet implements Runnable {
	public void init() {
		Panel tmp_panel;

		this.setLayout(new BorderLayout());

		bottom_panel=new Panel();
		bottom_panel.setLayout(new GridLayout(2,4));

		method_choice=new Choice();
		method_choice.addItem("Euler");
		method_choice.addItem("RK2");
		method_choice.addItem("RK4");
		method_choice.addItem("Symplectic Order 1");
		method_choice.addItem("Symplectic Order 2");
		method_choice.addItem("Symplectic Order 4");
		bottom_panel.add(method_choice);

		clear_button=new Button("Clear");
		bottom_panel.add(clear_button);

		tmp_panel=new Panel();
		tmp_panel.add(new Label("Epsilon: "));
		epsilon_text=new TextField("0.000");
		tmp_panel.add(epsilon_text);
		bottom_panel.add(tmp_panel);

		tmp_panel=new Panel();
		tmp_panel.add(new Label("dt: "));
		dt_text=new TextField("0.03");
		tmp_panel.add(dt_text);
		bottom_panel.add(tmp_panel);

		point_count=0;
		tmp_panel=new Panel();
		point_label=new Label("Points: 00000");
		tmp_panel.add(point_label);
		bottom_panel.add(tmp_panel);

		tmp_panel=new Panel();
		energy_label=new Label("Energy: 0.000");
		tmp_panel.add(energy_label);
		bottom_panel.add(tmp_panel);

		this.add("South",bottom_panel);

		top_panel=new Panel();
		this.add("Center",top_panel);
		this.layout();
		top_image=createImage(top_panel.size().width,top_panel.size().height);

		rule=new KAMSystem();
		action=1.0;
		angle=0.0;
		InitSystem();
	}

	public void run() {
		try {
			while(true) {
				sys.Advance();
				energy_label.setText("Energy: "+Double.toString(rule.Energy(sys.GetStateVector())));
				DrawSection();
				repaint();
				Thread.sleep(10);
			}
		}
		catch(InterruptedException e) {
			java.lang.System.out.println("Thread interrupted!");
		}
	}

	public void start() {
		if(thread==null) {
			thread=new Thread(this);
			thread.start();
		}
	}

	public void stop() {
		if(thread!=null) {
			thread.stop();
			thread=null;
		}
	}

	public void paint(Graphics g) {
		top_panel.getGraphics().drawImage(top_image,0,0,this);
	}

	public void update(Graphics g) {
		paint(g);
	}

	public boolean mouseDown(Event evt,int x,int y) {
		double dx,dy;
		int min_dim;

		// If in the top panel then set the action values.
		if(y<=top_panel.size().height) {
			min_dim=Math.min(top_panel.size().width,top_panel.size().height);
			dx=Math.abs(x-top_panel.size().width/2);
			dy=Math.abs(y-top_panel.size().height/2);
			action=Math.sqrt(dx*dx+dy*dy)*4.0/min_dim;
			angle=Math.atan2(dy,dx);
			point_count=0;
			InitSystem();
			return(true);
		}
		return(false);
	}

	public boolean action(Event evt,Object what) {
		Graphics g;

		if(evt.target==clear_button) {
			g=top_image.getGraphics();
			g.setColor(Color.white);
			g.fillRect(0,0,top_image.getWidth(this),top_image.getHeight(this));
			point_count=0;
			return(true);
		} else if(evt.target==method_choice) {
			InitSystem();
			return(true);
		}

		return(false);
	}

	public boolean lostFocus(Event evt,Object what) {
		if((evt.target==dt_text) || (evt.target==epsilon_text)) {
			InitSystem();
			return(true);
		}
		return(false);
	}

	// This function plots when sv[3] mod 2PI==0.  It plots a section of
	// the torus.
	private void DrawSection() {
		if(top_image==null) return;
		Graphics g=top_image.getGraphics();
		int x,y;
		int min_dim;
		double ef_sv0,ef_sv2;

		try {
		if(sys.Get(1)>=Math.PI) {
			min_dim=Math.min(top_image.getWidth(this),top_image.getHeight(this));
			ef_sv0=sv0+(sys.Get(0)-sv0)*(Math.PI-sv1)/(sys.Get(1)-sv1);
			ef_sv2=sv2+(sys.Get(2)-sv2)*(Math.PI-sv1)/(sys.Get(1)-sv1);
			x=(top_image.getWidth(this)>>1)+(int)(ef_sv2*Math.cos(ef_sv0)*min_dim/4.0);
			y=(top_image.getHeight(this)>>1)+(int)(ef_sv2*Math.sin(ef_sv0)*min_dim/4.0);
			g.setColor(Color.black);
			g.drawLine(x,y,x,y);
			point_count++;
			point_label.setText("Points: "+Integer.toString(point_count));
			sys.Set(1,sys.Get(1)-2.0*Math.PI);
		}
		while(sys.Get(0)>=Math.PI) sys.Set(0,sys.Get(0)-2.0*Math.PI);
		sv0=sys.Get(0);
		sv1=sys.Get(1);
		sv2=sys.Get(2);
		}
		catch(System.OutOfRangeException e) {}
	}

	private void InitSystem() {
		double dt,epsilon;

		switch(method_choice.getSelectedIndex()) {
		case 0:
			sys=new Euler(rule);
			break;
		case 1:
			sys=new Trapazoid(rule);
			break;
		case 2:
			sys=new RK4(rule);
			break;
		case 3:
			sys=new SimMap1(rule);
			break;
		case 4:
			sys=new SimMap2(rule);
			break;
		case 5:
			sys=new SimMap4(rule);
			break;
		}
		try {
			dt=Double.valueOf(dt_text.getText()).doubleValue();
		}
		catch(NumberFormatException ex) {
			dt=0.03;
			dt_text.setText("0.03");
		}
		try {
			epsilon=Double.valueOf(epsilon_text.getText()).doubleValue();
		}
		catch(NumberFormatException ex) {
			epsilon=0.0;
			epsilon_text.setText("0.0");
		}
		rule.epsilon=epsilon;
		sys.SetTimeStep(dt);
		try {
			sys.Set(0,angle);
			sys.Set(1,0.0);
			sys.Set(2,action);
			sys.Set(3,1.0);
		}
		catch(System.OutOfRangeException e) {}
	}

	private System sys;
	private KAMSystem rule;

	private Thread thread;
	private Panel bottom_panel;
	private Choice method_choice;
	private TextField epsilon_text;
	private TextField dt_text;
	private Button clear_button;
	private Panel top_panel;
	private Image top_image;
	private double action,angle;
	private Label point_label;
	private int point_count;
	private Label energy_label;
	private double sv0,sv1,sv2;
}