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

public class FractionCalculator extends Applet {
    TextField fractionField, densityAField, densityBField;
    Button calculate;
    Label outputLabel, outputExplLabel, fractionLabel;
    double densityA, densityB, fraction;
    int calcWhich = 0;
    CheckboxGroup which;
    Checkbox[] choice;
     
    public void init() {
        Font font = new Font("TimesRoman",Font.PLAIN,14);
        setLayout(new GridLayout(0,2));
        setBackground(Color.white);

        which = new CheckboxGroup();
        choice = new Checkbox[2];
        choice[0] = new Checkbox("Volume Fraction", which, true);
        choice[1] = new Checkbox("Mass Fraction", which, false);
        choice[0].setFont(font);
        choice[1].setFont(font);
        add(choice[0]);
        add(choice[1]);
        
        Label densityALabel = new Label("Mass Density A (g/cm^3)");
        densityALabel.setFont(font);
        densityAField = new TextField(20);
        densityAField.setFont(font);
        add(densityALabel);
        add(densityAField);

        Label densityBLabel = new Label("Mass Density B (g/cm^3)");
        densityBLabel.setFont(font);
        densityBField = new TextField(20);
        densityBField.setFont(font);
        add(densityBLabel);
        add(densityBField);

        fractionLabel = new Label("Mass Fraction ([A]/[A+B])");
        fractionLabel.setFont(font);
        fractionField = new TextField(20);
        fractionField.setFont(font);
        add(fractionLabel);
        add(fractionField);

        Label spacer = new Label("  ");
        spacer.setFont(font);
        calculate = new Button("Calculate");
        calculate.setFont(font);
        add(spacer);
        add(calculate);

        outputExplLabel = new Label("Volume Fraction ([A]/[A+B])");
        outputExplLabel.setFont(font);
        add(outputExplLabel);
        outputLabel = new Label("0.0");
        outputLabel.setFont(font);
        add(outputLabel);

        validate();
    }
    
    public void updateFractionLabels() {
        String whichFraction = which.getCurrent().getLabel();
        String volFractionText = "Volume Fraction ([A]/[A+B])";
        String weightFractionText = "Mass Fraction ([A]/[A+B])";
        
        if( whichFraction.equalsIgnoreCase("Volume Fraction") ) {
            calcWhich = 0;
            fractionLabel.setText(weightFractionText);
            outputExplLabel.setText(volFractionText);
        } else {
            calcWhich = 1;
            fractionLabel.setText(volFractionText);
            outputExplLabel.setText(weightFractionText);
        }
        validate();
    }

    public boolean action(Event e, Object a) {

        if (e.target instanceof Button) {

            //parse densityA field
            densityA=-1.;
            String errorText = "Bad Value for Density of A";
            try {
                densityA=Double.valueOf(densityAField.getText()).doubleValue();
            } catch (NumberFormatException exc) {
                outputLabel.setText(errorText);
                return true;
            }
            if((densityA < 0.0) || Double.isNaN(densityA)){
                outputLabel.setText(errorText);
                return true;
            }

            //parse densityB field
            densityB=-1.;
            errorText = "Bad Value for Density of B";
            try {
                densityB=Double.valueOf(densityBField.getText()).doubleValue();
            } catch (NumberFormatException exc) {
                outputLabel.setText(errorText);
                return true;
            }
            if((densityB < 0.0) || Double.isNaN(densityB)){
                outputLabel.setText(errorText);
                return true;
            }

            //parse fraction field
            fraction=0.0;
            try {
                fraction=Double.valueOf(fractionField.getText()).doubleValue();
            } catch (NumberFormatException exc) { 
                fractionField.setText(String.valueOf(0.0));
            }

            if (fraction < 0.0) {
                fraction = 0.0;
                fractionField.setText(String.valueOf(0.0));
            }
            if (fraction > 1.0) {
                fraction = 1.0;
                fractionField.setText(String.valueOf(1.0));
            }

            String outputText = "";
            double output;
            if (calcWhich == 0) {
                output = NCNRUtils.getVolumeFraction(densityA, 
                                                     densityB,
                                                     fraction);
            } else {
                output = NCNRUtils.getWeightFraction(densityA, 
                                                     densityB,
                                                     fraction);
            }
            //Arrange fraction label
            if(Double.isNaN(output)) {
                outputText = "Error in calculation.";
                outputLabel.setText(outputText);
            } else {
                outputText = String.valueOf(NCNRUtils.sigfigs(output,4));
                outputLabel.setText(outputText);
            }
        }
        if (e.target instanceof Checkbox) {
            updateFractionLabels();
        }
        return true;
    }

}