import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import java.util.*;

public class BouncyApplet extends Applet implements ActionListener{
	Ball bert;
	int nRings = 100;
	double drop=0, press, mass, radius=10, decay, kappa, dt;
	Panel header, footer, basics, options, results;
	MyCanvas diagram;
	Timer myTimer; 
	Label title, dropLbl, dropULbl, pressLbl, pressULbl,
		  ctLbl, ct, fpLbl,fp, efLbl, ef;
	TextField dropTxF, pressTxF, nRingsTxF, dtTxF, 
	          radiusTxF, massTxF, kappaTxF, decayTxF;
	Button goBtn, optBtn;
	int y = 0; // needed for graphical output of error reporting
	boolean ok = true;

	public void init() {
		setBackground(Color.white);
		setFont(new Font("SansSerif", Font.PLAIN,14));
		setLayout(new BorderLayout());
		
		GridBagLayout gridbag = new GridBagLayout();
		GridBagConstraints c = new GridBagConstraints();
		header = new Panel(gridbag);
			optBtn = new Button("show options");
			optBtn.setFont(new Font("SanSerif",Font.ITALIC,14));
			c.weightx = 1;
			gridbag.setConstraints(optBtn, c);
			header.add(optBtn);
			
			title = new Label("Bouncy Ball");
			title.setFont(new Font("Serif", Font.ITALIC + Font.BOLD, 24));
			c.gridwidth = GridBagConstraints.REMAINDER;
			gridbag.setConstraints(title, c);
		header.add(title);
		
		footer = new Panel(new GridLayout(2,1));
			results = new Panel();
			ctLbl = new Label("Contact", Label.RIGHT);
			ct = new Label("time   ");
			fpLbl = new Label("Footprint", Label.RIGHT);
			fp = new Label("diam.  ");
			efLbl = new Label("Effic.", Label.RIGHT);
			ef = new Label(" % ");
			results.add(ctLbl);
			results.add(ct);
			results.add(fpLbl);
			results.add(fp);
			results.add(efLbl);
			results.add(ef);
			
			basics = new Panel();
				dropLbl = new Label("Drop",Label.RIGHT);
				dropTxF = new TextField("1.0",4);
				dropULbl = new Label("m");
			basics.add(dropLbl);
			basics.add(dropTxF);
			basics.add(dropULbl);
				pressLbl = new Label("Pressure",Label.RIGHT);
				pressTxF = new TextField("20",4);
				pressULbl = new Label("kPa  ");
			basics.add(pressLbl);
			basics.add(pressTxF);
			basics.add(pressULbl);
			goBtn = new Button("  GO  ");
			goBtn.setFont(new Font("SanSerif",Font.BOLD, 16));
			basics.add(goBtn);
			// register the Listener: goBtn must send events somewhere.
			// In this case, we send them to the applet "this" which 
			// therefore must have an "actionPerformed()" method.
			goBtn.addActionListener(this);
		footer.add(basics);
		footer.add(results);
		add(footer, BorderLayout.SOUTH);
		
		diagram = new MyCanvas();
		add(diagram, BorderLayout.CENTER);
		validate();
		
		optBtn.addActionListener(this); // register the Listener (this Applet)
		add(header, BorderLayout.NORTH);
		
		// options panel is displayed dynamically
		// uses flow layout with items grouped by using secondary panels
		GridBagLayout gb39 = new GridBagLayout();
		GridBagConstraints c39 = new GridBagConstraints();
		c39.fill = GridBagConstraints.HORIZONTAL;
		options = new Panel(gb39);
		options.setFont(new Font("SanSerif", Font.PLAIN, 14));
		Label ballProps = new Label("The Ball ....");
		ballProps.setFont(new Font("Serif", Font.ITALIC, 16));
 		c39.gridwidth = GridBagConstraints.REMAINDER;
		gb39.setConstraints(ballProps,c39);
		options.add(ballProps);
		
		c39.weightx = 1;
		Label radiusLbl = new Label("radius");
		radiusTxF = new TextField("10",4);
		Label radiusULbl = new Label("cm");
 		c39.gridwidth = 1;
		gb39.setConstraints(radiusLbl,c39);
		gb39.setConstraints(radiusTxF,c39);
 		c39.gridwidth = GridBagConstraints.REMAINDER;
		gb39.setConstraints(radiusULbl,c39);
		options.add(radiusLbl);
		options.add(radiusTxF);
		options.add(radiusULbl);
		
		Label massLbl = new Label("mass");
		massTxF = new TextField("250",4);
		Label massULbl = new Label("g");
 		c39.gridwidth = 1;
		gb39.setConstraints(massLbl,c39);
		gb39.setConstraints(massTxF,c39);
		options.add(massLbl);
		options.add(massTxF);
 		c39.gridwidth = GridBagConstraints.REMAINDER;
		gb39.setConstraints(massULbl,c39);
		options.add(massULbl);
		
		Label kappaLbl = new Label("el. mod.");
		kappaTxF = new TextField("25",4);
		Label kappaULbl = new Label("kN/m");
 		c39.gridwidth = 1;
		gb39.setConstraints(kappaLbl,c39);
		gb39.setConstraints(kappaTxF,c39);
		options.add(kappaLbl);
		options.add(kappaTxF);
 		c39.gridwidth = GridBagConstraints.REMAINDER;
		gb39.setConstraints(kappaULbl,c39);
		options.add(kappaULbl);
		
		Label decayLbl = new Label("decay time");
		decayTxF = new TextField("5",4);
		Label decayULbl = new Label("ms");
 		c39.gridwidth = 1;
		gb39.setConstraints(decayLbl,c39);
		gb39.setConstraints(decayTxF,c39);
		options.add(decayLbl);
		options.add(decayTxF);
 		c39.gridwidth = GridBagConstraints.REMAINDER;
		gb39.setConstraints(decayULbl,c39);
		options.add(decayULbl);

		Label simPrec = new Label("Simulation");
		simPrec.setFont(new Font("Serif", Font.ITALIC, 16));
 		c39.gridwidth = GridBagConstraints.REMAINDER;
		gb39.setConstraints(simPrec,c39);
		options.add(simPrec);
		
		Label nRingsLbl = new Label("no. of rings");
		nRingsTxF = new TextField("100",4);
		Label nRingsULbl = new Label(" ");
 		c39.gridwidth = 1;
		gb39.setConstraints(nRingsLbl,c39);
		gb39.setConstraints(nRingsTxF,c39);
		options.add(nRingsLbl);
		options.add(nRingsTxF);
 		c39.gridwidth = GridBagConstraints.REMAINDER;
		gb39.setConstraints(nRingsULbl,c39);
		options.add(nRingsULbl); 

		
		Label dtLbl = new Label("time step");
		dtTxF = new TextField("10",4);
		Label dtULbl = new Label('\u00B5'+"s");
 		c39.gridwidth = 1;
		gb39.setConstraints(dtLbl,c39);
		gb39.setConstraints(dtTxF,c39);
		options.add(dtLbl);
		options.add(dtTxF);
 		c39.gridwidth = GridBagConstraints.REMAINDER;
		gb39.setConstraints(dtULbl,c39);
		options.add(dtULbl);
		
	}
	
	public void start() {
		bert = new Ball(this);
	}

		
	public void actionPerformed(ActionEvent ae) {
 		String str = ae.getActionCommand();
 		long msec ;
		if (str.equals("  GO  ")) {
			if (dataOK()) {
				goBtn.setLabel("STOP");
				bert = new Ball(this);
				ct.setText("time   ");
				fp.setText("diam.  ");
				ef.setText(" % ");
				MyTimerTask doFrame = new MyTimerTask();
				myTimer = new Timer();
				myTimer.scheduleAtFixedRate(doFrame,20,20);
			}
			else return;
		}
		else if (str.equals("STOP")) {
			myTimer.cancel();
			goBtn.setLabel("  GO  ");
		}
		else if (str.equals("show options")) {
			add(options, BorderLayout.WEST);
			optBtn.setLabel("hide options");
			validate();
		}
		else if (str.equals("hide options")) {
			remove(options);
			optBtn.setLabel("show options");
			validate();
		}	
	}
		
	boolean dataOK() {
		y = 0;
		ok = true;
		
		nRings = Integer.parseInt(nRingsTxF.getText());
		if (nRings < 8) {
			report("Minimum number of rings = 8");
			nRingsTxF.setText("8");
		}
		if (nRings > 1000) {
			report("Maximum number of rings = 1000");
			nRingsTxF.setText("1000");
		}
		
		press = Double.parseDouble(pressTxF.getText());
		if (press < 0) {
			report("Minimum pressure = 0");
			pressTxF.setText("0");
		}
		if (press > 1000) {
			report("Maximum pressure = 500kPa.");
			pressTxF.setText("500");
		}
		
		drop = Double.parseDouble(dropTxF.getText());
		if (drop < 0.01) {
			report("Minimum drop height = 0.01 m" );
			dropTxF.setText("0.01");
		}
		if (drop > 100) {
			report("Maximum drop height = 100 m");
			dropTxF.setText("100");
		}
		
		mass = Double.parseDouble(massTxF.getText());
		if (mass < 1) {
			report("Minimum mass = 1 g" );
			massTxF.setText("1");
		}
		if (mass > 5000) {
			report("Maximum mass = 5000 g");
			massTxF.setText("5000");
		}
		
		radius = Double.parseDouble(radiusTxF.getText());
		if (radius <1) {
			report("Minimum radius = 1 cm" );
			radiusTxF.setText("1");
		}
		if (radius > 50) {
			report("Maximum radius = 50 cm");
			dropTxF.setText("50");
		}
		
		if (ok) {
			double dti = Math.sqrt(mass/press/radius)/nRings/6;
			dti = Double.parseDouble(dps(dti*10000,0));
			if (dti<1)  {
				report("Impossible combination of data!");
			}
			dt = Double.parseDouble(dtTxF.getText());
			if (dt < 1) {
				report("Minimum time step = 1 "+'\u00B5'+"s");
				dtTxF.setText("1");
			}
			if (dt > dti) {
				report("Maximum time step = " + dti);
				dtTxF.setText("" + dti);
			}
			
			kappa = Double.parseDouble(kappaTxF.getText());
			if (kappa < 1) {
				report("Minimum elastic mod. = 1 kN/m");
				kappaTxF.setText("1");
			}
			if (kappa > 500) {
				report("Maximum elastic mod. = 500");
				kappaTxF.setText("500");
			}
		}
		
		if (ok) {
			double decay0 = dt*nRings*nRings/20000;
			decay0 = Double.parseDouble(dps(decay0,0));
			decay = Double.parseDouble(decayTxF.getText());
			if (decay < decay0) {
				report("Minimum decay time = " + decay0 + " ms");
				decayTxF.setText("" + decay0);
			}
			if (decay > 1000) {
				report("Maximum decay time = 1000 ms");
				decayTxF.setText("1000");
			}
		}
			if (!ok) report("Review values and try again.");
		return ok;
	}
	
	void report(String str) {
		Graphics g = diagram.getGraphics();
		g.setColor(Color.white);
		g.fillRect(0,y,400,50);
		g.setColor(Color.black);
		g.drawString(str,5,y+20);
		y +=25;
		ok = false;
	}

	String dps(double x, int d) {
		String s = "" + x;
		int i = s.indexOf(".");
		if (i < 0) return s;
		else return s.substring(0,i+d);
	} 

	class MyCanvas extends Canvas {
		public MyCanvas() {;}
		
		
		public void paint(Graphics g) {
			Dimension d = getSize();
		 	double scale = 2.5*d.height;
		 	int dia = (int) scale/5;
			int mid = d.width/2;
			int floor = d.height-6;
			int n = nRings*2;
	 		int x[] = new int[n];
			int y[] = new int[n];
	 		g.setColor(Color.white);
			g.fillRect(0,0,d.width,floor+1);
			g.setColor(Color.lightGray);
			g.fillRect(0,floor+1,d.width,5);
			g.setColor(Color.black);
			for (int i = 0; i<nRings; i++) {
				x[i] = (int)(bert.r[i]*scale);
				x[n-1-i] = mid -x[i];
				x[i] += mid;
				y[i] = floor - (int)(bert.h[i]*scale);
				y[n-1-i] = y[i];
			}
			g.drawPolygon(x,y,n);
		}
	}
		
	class MyTimerTask extends TimerTask {
		public void run() {
			boolean endTask = false;
			double t = 0;
//			calculate what happens in the next 100µs and draw
			while ((t += dt)<= 1e2) {  
				bert.calcChange();
				bert.damping();
				if (bert.onFloor() == 3) endTask = true;
			}
			Graphics g = diagram.getGraphics();
			diagram.paint(g);
//			cancel the Timer and show the results			
			if (endTask) {
				myTimer.cancel();
				ct.setText(dps(bert.contact*1000,2)+"ms");
				fp.setText(dps(bert.frmax*2000,0) + "mm");
				ef.setText(dps(bert.effic*100, 0) + "%");
				goBtn.setLabel("  GO  ");
			}
		}
	}
						
}