import java.applet.Applet;
import java.awt.*;
import java.lang.Math;
/*	Stefan Emet 1998. 

	class logistic_map controls the main-frame				*/
public class logistic_map extends Applet implements Runnable {	
	figure		figure_plot;  //	class figure controls the plotting
	double		a=2.5, X_0=0.2;
	double[]	X_t = new double[3]; 
	TextField	TextField_parameter_a,TextField_X_0;  
	Button		Button_Draw, Button_Stop, Button_Continue;        
	Thread		Thread_RUN=null;	// run -controller
	Panel		Panel_top, Panel_right, Panel_bottom;
	Label		Label_Status;
	boolean		CLEAR, FIRST, DRAW, NEXT=false;
				
public void init(){	
	setLayout(new BorderLayout(5,5));	// sets the main-border
	Panel_top = new Panel();
	Panel_top.add(new Label("X(t+1) = a X(t) ( 1-X(t) ) ,    t=0, 1, 2..."));
	Panel_top.add(new Label("    a:"));
	Panel_top.add(TextField_parameter_a= new TextField(""+a,3));
	Panel_top.add(new Label("X(0) :"));
	Panel_top.add(TextField_X_0= new TextField(""+X_0,3));
	add("North",Panel_top); // add to Logistic map

	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"));		
	Panel_right.add(new Label(" "));
	Panel_right.add(new Label(" "));
	add("East",Panel_right);

	Panel_bottom = new Panel();
	Panel_bottom.add(Label_Status = new Label("Status - label"));
	add("South",Panel_bottom);

	figure_plot = new figure(this);
	add("Center",figure_plot);
}
public void run() {// run() is called after start of the Thread_RUN
	// take value from button
	a = Double.valueOf(TextField_parameter_a.getText()).doubleValue(); 		
	X_0 = Double.valueOf(TextField_X_0.getText()).doubleValue();
	NEXT=false;
	X_t[0]=0; X_t[1]=X_0;
	X_t[2]= f(X_0);		
	while (DRAW){
		figure_plot.repaint(); 
		wait_for_next();	// wait until the animation is done	
		X_t[0]=X_t[1]; X_t[1]=X_t[2];
		X_t[2]= f(X_t[2]);	// calculate: x(t+1)=f(x(t))		
		DRAW=(DRAW)? DRAW_CHECK():DRAW;
		NEXT=false;
	} 					  
	Button_Draw.enable(); 
}
private void wait_for_next(){
	while (!NEXT){;}
	NEXT=false;
}
public boolean DRAW_CHECK(){							
        if (X_t[2]<0){
		Label_Status.setText("X(t) tends to -infinity");
		return false;
	}
	if (Thread_RUN==null)
		return false;
	return true;				
}
public double f(double x){
	return a*x*(1-x);
}
public void start(){
	CLEAR=true;
	if (Thread_RUN==null){
		Thread_RUN=new Thread(this);
	}
	Thread_RUN.start();		// calls the run -method
}
public void stop(){
	Thread_RUN=null;			// the thread to null
}
public boolean action(Event e, Object arg){
	if (e.target.equals(Button_Draw)){
		stop();
		FIRST = DRAW = true;
		Button_Draw.disable();
		Button_Continue.disable();
		Button_Stop.enable();
		Label_Status.setText("");
		start();		
	}
	if (e.target.equals(Button_Stop)){
		Button_Draw.enable();
		Button_Continue.enable();
		Button_Stop.disable();
		Thread_RUN.suspend();		
	}
	if (e.target.equals(Button_Continue)){
		Button_Continue.disable();
		Button_Stop.enable();
		Thread_RUN.resume();	
	}
	return false;
}
public void set_CLEAR(boolean set){
	CLEAR=set;
}
public void set_FIRST(boolean set){
	FIRST=set;
}
public void set_NEXT(boolean set){
	NEXT=set;
}
} // class logistic_map


//	class figure controls the plotting
class figure extends Canvas{
	logistic_map	logistic;
	double		X_min, X_max, Y_min, Y_max;	
	int		FIGURE_WIDTH, FIGURE_HEIGHT, 
			AXES_WIDTH, AXES_HEIGHT, UNIT,
			AXES_LEFT, AXES_RIGHT, AXES_TOP, AXES_BOTTOM,
			AXES_X_0, AXES_X_1, AXES_Y_0, AXES_Y_1; 
	final static boolean	ANIMATION=true, NO_ANIMATION=false;

figure (logistic_map initialize_map){
	super();
	logistic = initialize_map;
}
public void paint(Graphics g){
	FIGURE_WIDTH=size().width;		// the width of the Plot-window				
	FIGURE_HEIGHT=size().height;		// the height of the Plot-window						
	AXES_HEIGHT= (int)(0.85*FIGURE_HEIGHT);	// height and width of 
	AXES_WIDTH = (int)(0.80*FIGURE_WIDTH);	// the axes in the Plot-window
	AXES_LEFT  = (int)(0.1*FIGURE_WIDTH); 	// left and right of  
	AXES_RIGHT = AXES_LEFT+AXES_WIDTH; 	// the Plot-window
	AXES_TOP   = (int)(0.075*FIGURE_WIDTH);	// top and bottom of
	AXES_BOTTOM= AXES_TOP + AXES_HEIGHT; 	// Plot-window
	AXES_Y_1=(int)(0.2*FIGURE_HEIGHT);		// the pixel for y=1
	AXES_X_0=(int)(0.25*FIGURE_WIDTH);		// the pixel for x=0
	UNIT=(int)(0.6*FIGURE_HEIGHT); 			// the pixel for y in [0,1]
	AXES_Y_0=AXES_Y_1+UNIT;					// the pixel for y=0
	AXES_X_1=AXES_X_0 + UNIT; 				// the pixel for x=1
	X_min=-((double)(AXES_BOTTOM-AXES_Y_0)/UNIT);	// min(x)
	X_max=1+((double)(AXES_Y_1-AXES_TOP)/UNIT);		// max(x)
	Y_min=-((double)(AXES_BOTTOM-AXES_Y_0)/UNIT);	// min(y)
	Y_max=1+((double)(AXES_Y_1-AXES_TOP)/UNIT);		// max(y)
	update(g);
}
public void update(Graphics g){
	double X_t_0=logistic.X_t[0],X_t_1=logistic.X_t[1],X_t_2=logistic.X_t[2];

	if (logistic.CLEAR){			// clears the plot-window 	   
		logistic.set_CLEAR(false);
		coordinates(g);				// draw coordinates
		plot_function(g);			// draw the function
	}
	if (logistic.FIRST){
		logistic.set_FIRST(false);
		cross(g,X_t_1,X_t_0);		// put a cross at the startpoint
		draw(g,X_t_1,X_t_0,X_t_1,X_t_2,true);	
		cross(g,X_t_1,X_t_2);
		logistic.set_NEXT(true);
	}
	else if (logistic.DRAW){   
		draw(g,	X_t_0, X_t_1, X_t_1, X_t_1,ANIMATION);
		draw(g,	X_t_1, X_t_1, X_t_1, X_t_2,ANIMATION);
		cross(g,X_t_1,X_t_2);
		logistic.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);
	}
	g.setColor(Color.black);
}
public void plot_function(Graphics g){
	double	x1,y1,x2,y2,dx,
			interval_length=X_max-X_min;
	int		interval_xpix_length=AXES_RIGHT-AXES_LEFT;

	dx=(double)interval_length/interval_xpix_length;
	for (int i=1; i<=interval_xpix_length; i++){
		x1=X_min+(i-1)*dx;	y1=logistic.f(x1);
		x2=x1+dx;			y2=logistic.f(x2);
		if (y1>=Y_min && y2>=Y_min)
			draw(g,x1,y1,x2,y2,NO_ANIMATION); 
	}
}
public void pause(boolean animate){
	if (animate){
		try { Thread.sleep(25);}	// slows down the drawings with a tupplur 
		catch ( InterruptedException e ) {}
	}
}
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 int x_pixel(double x){
	int	pixvalue=AXES_X_0+(int)((X_min%1)*UNIT);
	if (x>=X_min){
		pixvalue=AXES_X_0 + (int)(x*UNIT);
	}
	return pixvalue;
}
public int y_pixel(double y){
	int pixvalue=AXES_BOTTOM;
	if (y >= Y_min){
		pixvalue=AXES_Y_0 - (int)(y*UNIT);
	}
	return pixvalue;
}
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 void coordinates(Graphics g){
	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);
	g.drawRect(AXES_X_0, AXES_Y_1, UNIT, UNIT);
	g.drawLine(AXES_LEFT,AXES_Y_0,AXES_RIGHT,AXES_Y_0);	// draws the x-axes
	g.drawLine(AXES_X_0,AXES_TOP,AXES_X_0,AXES_BOTTOM);	// draws the y-axes
	g.drawLine(x_pixel(X_min),y_pixel(Y_min),x_pixel(X_max),y_pixel(Y_max));// the diagonal x=y
	g.drawLine(x_pixel(X_min),AXES_Y_0-2,x_pixel(X_min),AXES_Y_0+2);// 
	g.drawLine(x_pixel(X_max),AXES_Y_0-2,x_pixel(X_max),AXES_Y_0+2);//
	g.drawString(""+roundoff(X_min,2), (x_pixel(X_min)-12),AXES_Y_0+12);
	g.drawString(""+roundoff(X_max,2), x_pixel(X_max)-8, AXES_Y_0+12);
	g.drawString("X(t+1)",AXES_X_0+2,AXES_TOP-4);
	g.drawString("X(t)",AXES_RIGHT+2,AXES_Y_0+12);
	g.drawString("0",AXES_X_0+2,AXES_Y_0+12);
	g.drawString("1",AXES_X_0-8,AXES_Y_1+2);
	g.drawString("1",AXES_X_1-3,AXES_Y_0+12);
}
} // class figure