import java.applet.Applet;
import java.awt.*;
import java.lang.Math;
import java.awt.event.*;
/*	Stefan Emet 1998. A tool for plotting orbits of 2-dimensional discrete dynamical systems.

	class two_dim controls the main-frame							*/
public class two_dim extends Applet implements Runnable, ActionListener{	
	double		X_0=3.0, Y_0=1.5, a=0.5, b=0.4;
	double[]	X_t = new double[3], Y_t = new double[3]; 
	int			time=0;
	Figure		Figure_plot;
	Panel		Panel_top, Panel_top_f, Panel_top_input,
				Panel_right, Panel_bottom;
	Label		Label_Status;
	TextField	TextField_parameter_a, TextField_parameter_b,
				TextField_X_0, TextField_Y_0;  
	Button		Button_Draw, Button_Stop, Button_Continue;        
	Checkbox	Checkbox_trace;	
	Thread		Thread_RUN=null;		// run -controller
	boolean		CLEAR, FIRST, DRAW, NEXT=false, TRACES=true;
				
public void init(){	
	setLayout(new BorderLayout(5,5));	// sets the main-border
	Panel_top = new Panel();		
	Panel_top_f = new Panel();
	Panel_top_f.setLayout(new GridLayout(2,1,2,2));
	Panel_top_f.add(new Label("X(t+1) = a X(t) + b Y(t)"));
	Panel_top_f.add(new Label("Y(t+1) = X(t)              , t = 0, 1, 2 ..."));
	Panel_top.add(Panel_top_f);
	Panel_top_input = new Panel();
	Panel_top_input.setLayout(new GridLayout(2,4,2,2));
	Panel_top_input.add(new Label("          a:"));
	Panel_top_input.add(TextField_parameter_a= new TextField(""+a,3));
	Panel_top_input.add(new Label("     X(0) :"));
	Panel_top_input.add(TextField_X_0= new TextField(""+X_0,3));
	Panel_top_input.add(new Label("          b:"));
	Panel_top_input.add(TextField_parameter_b= new TextField(""+b,3));
	Panel_top_input.add(new Label("     Y(0) :"));
	Panel_top_input.add(TextField_Y_0= new TextField(""+Y_0,3));
	Panel_top.add(Panel_top_input);	
	add("North",Panel_top);				// layout to the top of main border

	Panel_right = new Panel();
	Panel_right.setLayout(new GridLayout(0,1,5,5));
	Panel_right.add(Button_Draw = new Button("Draw"));
	Panel_right.add(Button_Continue = new Button("Continue"));
	Panel_right.add(Button_Stop = new Button("Stop"));		
	Button_Draw.addActionListener(this);
	Button_Stop.addActionListener(this);
	Button_Continue.addActionListener(this);
	Panel_right.add(new Label(" "));
	Panel_right.add(Checkbox_trace = new Checkbox("Traces",true));
	add("East",Panel_right);			// layout to the right of main border

	Panel_bottom = new Panel();
	Panel_bottom.add(Label_Status = new Label("Status - label"));
	add("South",Panel_bottom);			// layout to the bottom of main border

	Figure_plot = new Figure(this);
	add("Center",Figure_plot);			// the plottings/drawings in the middle
}
public void run() {
	read_values();			// reads values from input-fields
	X_t[0]=0; X_t[1]=X_0;	// sets the values
	Y_t[0]=0; Y_t[1]=Y_0;
	X_t[2]=f(X_0,Y_0)[0];	// calculates: 
	Y_t[2]=f(X_0,Y_0)[1];	//  {x(1),y(1)} = f(x(0),y(0))
	time=1;
	while (DRAW){		
		Figure_plot.repaint();
		wait_for_next();		// wait until the drawing is done
		X_t[0]=X_t[1];X_t[1]=X_t[2];// shifts the previous values
		Y_t[0]=Y_t[1];Y_t[1]=Y_t[2];
		X_t[2]=f(X_t[1],Y_t[1])[0];	// calculates: 
		Y_t[2]=f(X_t[1],Y_t[1])[1];	//  {x(t+1),y(t+1)} = f(x(t),y(t))
		time++;
	}
}
private void wait_for_next(){
	while (!NEXT) {;}
	NEXT=false;
}
public double[] f(double x, double y){
	double[] x_y=new double[2];
	x_y[0]=a*x+b*y;
	x_y[1]=x;
	return x_y;			
}
public double[] det(){// returns the determinants of a 2*2-matrix
	double[]	determinant=new double[2];
	determinant[0]=(double)(a+Math.sqrt(Math.pow(a,2)+4*b))/2;
	determinant[1]=(double)(a-Math.sqrt(Math.pow(a,2)+4*b))/2;
	return determinant;
}
public void read_values(){// reads the input-values
	a = Double.valueOf(TextField_parameter_a.getText()).doubleValue(); 		
	b = Double.valueOf(TextField_parameter_b.getText()).doubleValue();
	X_0 = Double.valueOf(TextField_X_0.getText()).doubleValue(); 		
	Y_0 = Double.valueOf(TextField_Y_0.getText()).doubleValue();
	TRACES=Checkbox_trace.getState();// checks whether checkbox is selected
}
public void start(){
	CLEAR=true;
	if (Thread_RUN==null){
		Thread_RUN=new Thread(this);
	}
	Thread_RUN.start();
}
public void stop(){
	Thread_RUN=null;
}
public  void actionPerformed(ActionEvent e){
Object source=e.getSource();
	if (source==Button_Draw){
		stop();
		FIRST=DRAW=true;
		NEXT=false;
		Button_Draw.setEnabled(false);
		Button_Continue.setEnabled(false);
		Button_Stop.setEnabled(true);
		start();
	}
	if (source==Button_Stop){
		Button_Draw.setEnabled(true);
		Button_Continue.setEnabled(true);
		Button_Stop.setEnabled(false);
		Thread_RUN.suspend();
	}
	if (source==Button_Continue){
		Button_Continue.setEnabled(false);
		Button_Stop.setEnabled(true);
		Thread_RUN.resume();
	}
}			
public void set_CLEAR(boolean set){
	CLEAR=set;
}
public void set_FIRST(boolean set){
	FIRST=set;
}
public void set_NEXT(boolean set){
	NEXT=set;
}
} // end of class two_dim

				
//	class Figure controls the plotting
class Figure extends Canvas{
	two_dim		two_dim_fig;
	double		X_min, X_max, Y_min, Y_max;	
	int			FIGURE_WIDTH, FIGURE_HEIGHT, 
				AXES_LEFT, AXES_RIGHT, AXES_TOP, AXES_BOTTOM,
				AXES_WIDTH, AXES_HEIGHT, X_unit, Y_unit; 				 
	final static boolean	ANIMATION=true, 
							NO_ANIMATION=false;

Figure (two_dim f){
	super();
	two_dim_fig = f;
}
public void paint(Graphics g){
	double		x_part=0.8, y_part=0.85;
	FIGURE_WIDTH=getSize().width;		// the width of the Plot-window	(Canvas)			
	FIGURE_HEIGHT=getSize().height;		// the height of the Plot-window (Canvas)						
	AXES_HEIGHT=(int)(y_part*FIGURE_HEIGHT);// height and width of 
	AXES_WIDTH=	(int)(x_part*FIGURE_WIDTH);	// the axes in the Plot-window
	AXES_LEFT=	(int)((1-x_part)/2*FIGURE_WIDTH);// the left of the axes
	AXES_RIGHT=	(int)((1+x_part)/2*FIGURE_WIDTH);// the right of the axes
	AXES_TOP=	(int)((1-y_part)/2*FIGURE_HEIGHT);// the top 
	AXES_BOTTOM=(int)((1+y_part)/2*FIGURE_HEIGHT);// the bottom
	update(g);
}
public void update(Graphics g){
	double[]	X_t=two_dim_fig.X_t,	// copy the values from   
				Y_t=two_dim_fig.Y_t;	// class two_dim

	if (two_dim_fig.CLEAR){
		two_dim_fig.set_CLEAR(false);
		range();
		coordinates(g);
	}
	if (two_dim_fig.FIRST){
		two_dim_fig.set_FIRST(false);
		cross(g,X_t[1],Y_t[1]);	   // puts a cross at the startpoint: (x(0),y(0))
		draw(g,X_t[1],Y_t[1],X_t[2],Y_t[2],ANIMATION); // draw a line between the points
		cross(g,X_t[2],Y_t[2]);	   // a cross at (x(1),y(1)) 
		two_dim_fig.set_NEXT(true);// indicates that the drawing is done
	}
	else if (two_dim_fig.DRAW){
		draw(g,X_t[1],Y_t[1],X_t[2],Y_t[2],ANIMATION); // draw a line between the points
		cross(g,X_t[2],Y_t[2]);	   // a cross at (x(1),y(1)) 
		two_dim_fig.set_NEXT(true);
	}
}
public void draw(Graphics g, double x0, double y0, double x1, double y1, boolean animate){
	double	dy;
	int		x0_pix=x_pixel(x0), x1_pix=x_pixel(x1),  
			y0_pix=y_pixel(y0), y1_pix=y_pixel(y1), 
			dx,istep,i;

	if (x0_pix == x1_pix && y0_pix == y1_pix){
		return;
	}
	else if (x0_pix != x1_pix){
		istep=Math.abs(x0_pix-x1_pix); // total x-pix-step

		dy=(double)(y1_pix-y0_pix)/istep;
		dx=(x0_pix > x1_pix)? -1: 1; 
	}
	else {
		istep=Math.abs(y0_pix-y1_pix); // total y-pix-step
		dx=0;
		dy=(y0_pix > y1_pix)? -1: 1; 
	}
	g.setColor(Color.magenta);
	for (i=1; i<= istep; i++){
		g.drawLine(	(int)(x0_pix+(i-1)*dx),(int)(y0_pix+(i-1)*dy),
					(int)(x0_pix+i*dx),(int)(y0_pix+i*dy));				
		pause(animate);
	}
	if (!two_dim_fig.TRACES){
		g.setColor(Color.white);
		for (i=1; i<= istep; i++){
			g.drawLine(	(int)(x0_pix+(i-1)*dx),(int)(y0_pix+(i-1)*dy),
						(int)(x0_pix+i*dx),(int)(y0_pix+i*dy));				
			pause(animate);
		}
	}	
	g.setColor(Color.black);
}
public void pause(boolean animate){
	if (animate){
		try { Thread.sleep(25);}// slows down the drawings 25 milliseconds
		catch ( InterruptedException e ) {}
	}
}
public void range(){ // determines the range of the axis
	double		det_min, det_min_abs, det_max, det_max_abs;	

	det_min=Math.min(two_dim_fig.det()[0],two_dim_fig.det()[1]);
	det_max=Math.max(two_dim_fig.det()[0],two_dim_fig.det()[1]);
	det_min_abs=Math.abs(det_min);  // the absolute values
	det_max_abs=Math.abs(det_max);  // of the determinants

	if (det_max_abs <= 1){
		X_max=Math.abs(two_dim_fig.X_0)+1;
		X_min=-X_max; 
		Y_max=Math.abs(two_dim_fig.Y_0)+1;
		Y_min=-Y_max;
	}
	else if (det_min_abs > 1 || det_max_abs >1){
		X_max=1000;
		X_min=-10;
		Y_max=1000;
		Y_min=-10;
	}
	//two_dim_fig.showStatus("X: "+X_min+ " : "+X_max+" , Y: "+Y_min+" : "+Y_max);	
	//two_dim_fig.Label_Status.setText("Det: "+roundoff(det_min,2)+" | "+roundoff(det_max,2));	
}
public void cross(Graphics g, double x, double y){
	int x_pix=x_pixel(x), y_pix=y_pixel(y);
	g.setColor(Color.blue);
	g.drawLine(x_pix-1,y_pix-1,x_pix+1,y_pix+1);
	g.drawLine(x_pix-1,y_pix+1,x_pix+1,y_pix-1);
	g.setColor(Color.black);
}
public void coordinates(Graphics g){
	double x0=two_dim_fig.X_0, y0=two_dim_fig.Y_0;
	g.setColor(Color.white);
	g.fillRect(0,0,FIGURE_WIDTH,FIGURE_HEIGHT);
	g.setColor(Color.black);
	g.drawRect(0,0,FIGURE_WIDTH-1,FIGURE_HEIGHT-1); // draws the frame around the head border	
	g.drawRect(AXES_LEFT,AXES_TOP,AXES_WIDTH,AXES_HEIGHT);// frame around the plot-window
	g.drawLine(x_pixel(x0),y_pixel(Y_min)+2,x_pixel(x0),y_pixel(Y_min)-2);// tickmark at
	g.drawString(""+roundoff(x0,2),x_pixel(x0)-10,y_pixel(Y_min)+12);	  // x(0)
	g.drawLine(x_pixel(X_min)-2,y_pixel(y0),x_pixel(X_min)+2,y_pixel(y0));// tickmark at
	g.drawString(""+roundoff(y0,2),x_pixel(X_min)-25,y_pixel(y0)+5);	  // y(0)
	g.drawString("Y",x_pixel(X_min)+1,y_pixel(Y_max)-4);	  // Y-axis label	
	g.drawString("X",x_pixel(X_max)+4,y_pixel(Y_min)+5);	  // X-axis label	
}
public double roundoff(double x, int n){
	// returns the double x with n decmals
	return (double)(Math.round(x*Math.pow(10,n)))/Math.pow(10,n);
}
public int x_pixel(double x){
	int pixvalue=AXES_LEFT;
	if (x>=X_min && x<=X_max){
		pixvalue=(int)(((double)(x-X_min)/(X_max-X_min))*AXES_WIDTH)+AXES_LEFT;			
	}
	return pixvalue;
}
public int y_pixel(double y){
	int pixvalue=AXES_BOTTOM;
	if (y>=Y_min && y<=Y_max){
		pixvalue=AXES_BOTTOM-(int)(((double)(y-Y_min)/(Y_max-Y_min))*AXES_HEIGHT);			
	}
	return pixvalue;
}
} // end of class Figure