// Simulator of hydrostatic pressure across a HOH permiable membrane
//	R. Bowen 5/97

import java.awt.*;

public class hydrostatic extends java.applet.Applet
{
	LabCanvas		lab;
	TextField		textR = new TextField("0."), textL = new TextField("0.");
	Label          labelR = new Label("", Label.CENTER), labelL = new Label("", Label.CENTER);
	
	Choice		chRSolute = new Choice(), chLSolute = new Choice();
	Choice         chRConc = new Choice(), chLConc = new Choice();
	Button		btRun = new Button("  Run  ");

     public void init()
     {

		setBackground(Color.white);
		setLayout(new BorderLayout());

		Color colorL = new Color(255,255,192);
		Color colorR = new Color(192,255,192);

		chLSolute.setBackground(colorL);
		chLConc.setBackground(colorL);
		textL.setBackground(colorL);
		labelL.setBackground(colorL);
		chRSolute.setBackground(colorR);
		chRConc.setBackground(colorR);
		textR.setBackground(colorR);
		labelR.setBackground(colorR);
		
		chLSolute.addItem("NaCl (58 g/mole)");
		chLSolute.addItem("sucrose (342 g/mole)");
		chLSolute.addItem("albumin (66000 g/mole)");
		chRSolute.addItem("NaCl (58 g/mole)");
		chRSolute.addItem("sucrose (342 g/mole)");
		chRSolute.addItem("albumin (66000 g/mole)");

		chLConc.addItem("grams/liter");
		chLConc.addItem("molar");
		chRConc.addItem("grams/liter");
		chRConc.addItem("molar");

		Panel rPanel = new Panel();
		rPanel.setLayout(new GridLayout(1,2));
		rPanel.add(textR);
		rPanel.add(chRConc);
		Panel lPanel = new Panel();
		lPanel.setLayout(new GridLayout(1,2));
		lPanel.add(textL);
		lPanel.add(chLConc);

		Panel rightPanel = new Panel();
		rightPanel.setLayout(new GridLayout(3,1));
		rightPanel.add(chRSolute);
		rightPanel.add(rPanel);
		rightPanel.add(labelR);
		Panel leftPanel = new Panel();
		leftPanel.setLayout(new GridLayout(3,1));
		leftPanel.add(chLSolute);
		leftPanel.add(lPanel);
		leftPanel.add(labelL);

		Panel bottom = new Panel();
		bottom.setLayout(new FlowLayout());
          	bottom.add(leftPanel);
          	bottom.add(btRun);
          	bottom.add(rightPanel);

		lab = new LabCanvas(400,270,this.size().width);
          add("South", bottom);
		add("North", lab);
     }

	public boolean action(Event evt, Object arg)
	{
		if (arg.equals("  Run  ")) {
			btRun.setLabel("Reset");
			flow();					
		}
		else if (arg.equals("Reset")) {
			labelR.setText("");
			labelL.setText("");
			btRun.setLabel("  Run  ");
			lab.reset();
		}
		return true;
	}

	private String dString(double d, int n) {
		// converts double to string with max of n digits after decimal point
		String s = Double.toString(d);
		String stemp;
		int length = s.length();
		int pindex = s.indexOf('.');
		
		int eindex = s.indexOf('E');
		if (eindex == -1) eindex = s.indexOf('e');
		if (eindex != -1) {
			stemp = s.substring(0, Math.min(pindex+3,length)) + s.substring(eindex);
			s = stemp;
		}
		else if (d == 0.) s = "0.0";
		else if (d >= 1.0) s = s.substring(0, Math.min(pindex+3,length));
		else { // convert to sci notation
			int i = pindex + 1;
			while (i < length && s.charAt(i) == '0') ++i;
			int exponent = i - pindex;
			stemp = s.substring(i,i+1) + ".";
			++i;
			for (int k = 0; k < n && i < length; ++k) {
				stemp += s.charAt(i);
				++i;
			}
			stemp += "E-" + Integer.toString(exponent);
			s = stemp;
		}
		return s;
	}

	public void flow() {
		double	concR, concL, molarityR = 0., molarityL = 0., mw = -1;
		int		iR = 1, iL = 1, index;
		int		cmHOH;
		String 	moleculeR, moleculeL;
		boolean	flow_to_right, badLeft = false, badRight = false;

		try {
			concR = Double.valueOf(textR.getText()).doubleValue();
			if (concR < 0.) badRight = true;
			else {
				index = chRSolute.getSelectedIndex();
				if (index == 0) mw = 58.44;
				else if (index == 1) mw = 342.3; 
				else if (index == 2) mw = 66000.;
				if (chRConc.getSelectedItem().equals("molar")) {
					molarityR = concR;
					labelR.setText(dString(molarityR * mw, 2) + " g/l");
				}
				else {
					molarityR = concR/mw;
					labelR.setText(dString(molarityR, 2) + " M");
				}
			}
		}
		catch (NumberFormatException e) { badRight = true; }
		if (badRight) labelR.setText("Bad value");

		try {
			concL = Double.valueOf(textL.getText()).doubleValue();
			if (concL < 0.) badLeft = true;
			else {
				index = chLSolute.getSelectedIndex();
				if (index == 0) mw = 58.44;
				else if (index == 1) mw = 342.3; 
				else if (index == 2) mw = 66000.;
				if (chLConc.getSelectedItem().equals("molar")) {
					molarityL = concL;
					labelL.setText(dString(molarityL * mw, 2) + " g/l");
				}
				else {
					molarityL = concL/mw;
					labelL.setText(dString(molarityL, 2) + " M");
				}
			}
		}
		catch (NumberFormatException e) { badLeft = true; }
		if (badLeft) labelL.setText("Bad value");

		if (badRight || badLeft) return;
		if (chRSolute.getSelectedIndex() == 0) iR = 2;
		if (chLSolute.getSelectedIndex() == 0) iL = 2;
		System.out.println("About to execute");
		lab.execute(molarityR, iR, molarityL, iL);
	}
}

class LabCanvas extends Canvas implements Runnable
{
	int		cmHOH, nLines, paintRow, xoffset;
	double	molarityR, molarityL;
	double	effect_molR, effect_molL;	// effective molarity (1 except NaCl which is 2)
	String	errorStr;
	boolean	error = false;
	boolean	running = false;
	boolean	flow_to_right;
	Thread	runner;

	LabCanvas(int width, int height, int applet_width) {
		resize(width, height);
		xoffset = (applet_width - width)/2;
		System.out.println("Offset = " + xoffset);
	}

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

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

	public void run()
	{
		for (int i = 0; i < nLines; ++i) {
			paintRow = i;
			repaint();
			try { Thread.sleep(50); }
			catch (InterruptedException e) { }
		}
	}

	public void execute(double molR, int iR, double molL, int iL) {
		effect_molR = (double) iR * molR;
		effect_molL = (double) iL * molL;
		// 1 molar dif == 23974.6 cm HOH pressure
		cmHOH = (int) (23974.6 * (effect_molR - effect_molL));
		if (cmHOH < 0) {
			flow_to_right = false;
			cmHOH = -cmHOH;
		}
		else flow_to_right = true;

		if (cmHOH < 1) {
			errorStr = "Pressure < 1 cm water";
			error = true;
			nLines = 0;
		}
		else if (cmHOH <= 10) nLines = (int) (((float) cmHOH)/0.1);
		else if (cmHOH <= 100) nLines = cmHOH;
		else if (cmHOH <= 1000) nLines = cmHOH/10;
		else if (cmHOH <= 10000) nLines = cmHOH/100;
		else {
			errorStr = "Pressure > 10000 cm !";
			error = true;
			nLines = 0;
		}
		if (nLines != 0) {
			running = true;
			start();
		}
		else repaint();
	}

	public void reset() {
		running = false;
		stop();
		repaint();
	}

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

	public void paint(Graphics g) {
		int		rowY, xpos;
		String	str;
		Font 	f = new Font("TimesRoman", Font.BOLD, 12);
		FontMetrics fm = g.getFontMetrics(f);

		g.setFont(f);

		if (error) {
			g.setColor(Color.red);
			xpos = (this.size().width - fm.stringWidth(errorStr))/2;
			// xpos = xoffset + 100 + ((200 - fm.stringWidth(errorStr))/2);
			g.drawString(errorStr, xpos, 115);
			error = false;
			return;			
		}

		if (running) {
			if (paintRow == 0) {		//  graphically open the membrane
				g.setColor(Color.cyan);
				g.drawLine(xoffset+200,210,xoffset+200,260);
				g.setColor(Color.black);
				for (int k = 212; k < 260; k += 10) g.drawLine(xoffset+200,k,xoffset+200,k+5);
				//str = Double.toString(molarityL) + " M";
				//xpos = xoffset + 50 + ((150 - fm.stringWidth(str))/2);
				//g.drawString(str,xpos,250);
				//str = Double.toString(molarityR) + " M";
				//xpos = xoffset + 200 + ((150 - fm.stringWidth(str))/2);
				//g.drawString(str,xpos,250);
			}
			else if (paintRow == nLines - 1) {
				g.setColor(Color.blue);
				rowY = 110 - paintRow;
				g.drawLine(xoffset+101, rowY, xoffset+299, rowY);
				rowY = 110 + paintRow;
				g.drawLine(xoffset+101, rowY, xoffset+299, rowY);
				str = "P = " + Integer.toString(cmHOH) + " cm water";
				xpos = xoffset + 100 + ((200 - fm.stringWidth(str))/2);
				g.drawString(str,xpos,115);
			}

			if (flow_to_right) {
				g.setColor(Color.cyan);
				rowY = 110 - paintRow;
				g.drawLine(xoffset+300, rowY, xoffset+350, rowY);
				g.setColor(Color.white);
				rowY = 110 + paintRow;
				g.drawLine(xoffset+50, rowY, xoffset+100, rowY);
			}
			else {
				g.setColor(Color.cyan);
				rowY = 110 - paintRow;
				g.drawLine(xoffset+50, rowY, xoffset+100, rowY);
				g.setColor(Color.white);
				rowY = 110 + paintRow;
				g.drawLine(xoffset+300, rowY, xoffset+350, rowY);
			}
		}

		else { // reset
			g.setColor(Color.white);
			g.fillRect(xoffset+0, 0, xoffset+this.size().width, this.size().height);

			g.setColor(Color.cyan);
			g.fillRect(xoffset+50, 210, 300, 50);
			g.fillRect(xoffset+50, 110, 50, 100);
			g.fillRect(xoffset+300 ,110, 50, 100);
	
			g.setColor(Color.black);
			g.drawLine(xoffset+49,5,xoffset+49,261);
			g.drawLine(xoffset+49,261,xoffset+351,261);
			g.drawLine(xoffset+351,261,xoffset+351,5);
			g.drawLine(xoffset+101,5,xoffset+101,209);
			g.drawLine(xoffset+101,209,xoffset+299,209);
			g.drawLine(xoffset+299,209,xoffset+299,5);
			g.drawLine(xoffset+200,210,xoffset+200,260);
		}
	}

}