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

/**
 * Converts U.S units to SI units.
 *  http://www.ibluemojo.com
 *  @author H.Joon Kim   
 */
public class UnitConverter extends Applet implements ActionListener, ItemListener {
 
    // Array of ratio/factors between units
    private double factorArray[];
    private boolean complex; 
    
    // Interface components
    private Panel radio, field;
    private TextField input, output;
    private Button convert;
    private Label toLabel, status;
    private Checkbox area, energy, pressure, length, velocity, volume, weight, temperature;
    private CheckboxGroup units;
    private Choice inputChoice, outputChoice;    
    
    
    /**
     * Initialize the applet.
     */
    public void init() {
        setSize(380, 220);
		super.init();
		this.setLayout(null);
		this.setBackground(new Color(221, 238, 255));
	
		radio = new Panel(new FlowLayout());	
		field = new Panel(new GridLayout(2, 3, 5, 10));
		input = new TextField("1", 10);
		output = new TextField(10);
		convert = new Button("Convert!");
		toLabel = new Label("To", Label.CENTER);
		status = new Label();
		output.setEditable(false);
		
		output.setBackground(new Color(255, 255, 223));
		units = new CheckboxGroup();
		area = new Checkbox("Area", units, false);
		energy = new Checkbox("Energy", units, false);
		length = new Checkbox("Length", units, true);
		pressure = new Checkbox("Pressure", units, false);
		velocity = new Checkbox("Velocity", units, false);
		volume = new Checkbox("Volume", units, false);
		weight = new Checkbox("Weight", units, false);
		temperature = new Checkbox("Temperature", units, false);
	
		// Add components to event listeners
		convert.addActionListener(this);
		area.addItemListener(this);
		energy.addItemListener(this);
		length.addItemListener(this);
		pressure.addItemListener(this);
		velocity.addItemListener(this);
		volume.addItemListener(this);
		weight.addItemListener(this);
		temperature.addItemListener(this);
	
		inputChoice = new Choice();
		outputChoice = new Choice();
	
		inputChoice.setFont(new Font("", Font.PLAIN, 12));
		outputChoice.setFont(new Font("", Font.PLAIN, 12));
		
		// Set the default list with Choices for 'length'
		factorArray = lengthFactor();
		inputChoice.add("US: inch");
		inputChoice.add("US: feet");
		inputChoice.add("US: yard");
		inputChoice.add("US: mile");
		inputChoice.add("SI: mm");
		inputChoice.add("SI: cm");
		inputChoice.add("SI: m");
		inputChoice.add("SI: km");
		
		outputChoice.add("US: inch");
		outputChoice.add("US: feet");
		outputChoice.add("US: yard");
		outputChoice.add("US: mile");
		outputChoice.add("SI: mm");
		outputChoice.add("SI: cm");
		outputChoice.add("SI: m");
		outputChoice.add("SI: km");
	
		// Add Checkboxes to their panels
		radio.add(length);
		radio.add(weight);
		radio.add(velocity);
		radio.add(area);
		radio.add(volume);
		radio.add(temperature);
		radio.add(energy);		
		radio.add(pressure);		
	
		field.add(input);
		field.add(convert);
		field.add(output);
		field.add(inputChoice);
		field.add(toLabel);
		field.add(outputChoice);
	
		// Set the locations of interface comps.
		radio.setBounds(0, 45, 350, 60);
		field.setBounds(10, 110, 350, 60);
		status.setBounds(10, 180, 250, 30);
		
		// Add Panels and Labels to the applet
		this.add(radio);
		this.add(field);
		this.add(status);	
    }

    /**
     * Perform converting units.
     */
    public void actionPerformed(ActionEvent e) {
		try { 
		    // Obtain the base input value
		    String baseStr = input.getText();		    
		    Double baseRaw = new Double(baseStr);
		    double base = baseRaw.doubleValue();
		    
		    // Get index of selected units and assign them the respective 
		    // converting factor on the factor[] array.
		    int inputIndex = inputChoice.getSelectedIndex();
		    int outputIndex = outputChoice.getSelectedIndex();
		    
		    if (complex) {
		        double converted = doComplexConversion(base, inputIndex, outputIndex);
		        output.setText("" + converted);
			    status.setText("");
		    }
		    else {
		        double inputFactor = factorArray[inputIndex];
			    double outputFactor = factorArray[outputIndex];
			    
			    // Convert the input
			    double factor = inputFactor / outputFactor;
			    double converted = base * factor;
			    output.setText("" + converted);
			    status.setText("");
		    }		    
		}
		//check for valid input (numbers)
		catch (NumberFormatException nfe) {
		    status.setText("Error : You must input a number.");
		    input.setText("");
		}
    }
    
    /**
     * Change the item state of the drop-down menu, depending on the choice of
     * the type of units. 
     */
    public void itemStateChanged(ItemEvent e) {
		// Check for selected radio button
		Checkbox cb = (Checkbox)(e.getItemSelectable());
		output.setText("");
		inputChoice.removeAll();
		outputChoice.removeAll();
		//assign Choice values depending on selected Checkbox
		if (cb == area) {
		    complex = false; 
		    // Assign appropriate factors
		    factorArray = areaFactor();
		    
		    inputChoice.add("US: inch");
		    inputChoice.add("US: feet");
		    inputChoice.add("US: yard");
		    inputChoice.add("US: mile");
		    inputChoice.add("SI: cm");
		    inputChoice.add("SI: m");
		    inputChoice.add("SI: acre");
		    inputChoice.add("SI: km");
		    
		    outputChoice.add("US: inch");
		    outputChoice.add("US: feet");
		    outputChoice.add("US: yard");
		    outputChoice.add("US: mile");
		    outputChoice.add("SI: cm");
		    outputChoice.add("SI: m");
		    outputChoice.add("SI: acre");
		    outputChoice.add("SI: km");
	
		} else if (cb == energy) {
		    complex = false; 
		    // Assign appropriate factors
		    factorArray = energyFactor();
		    
		    inputChoice.add("US: in*lbf");
		    inputChoice.add("US: ft*lbf");
		    inputChoice.add("US: Btu's"); 
		    inputChoice.add("US: kcal");
		    inputChoice.add("SI: Joules"); 
		    inputChoice.add("SI: kw-hours");
		    inputChoice.add("SI: hp"); 
		    
		    outputChoice.add("US: in*lbf"); 
		    outputChoice.add("US: ft*lbf"); 
		    outputChoice.add("US: Btu's"); 
		    outputChoice.add("US: kcal");
		    outputChoice.add("SI: Joules"); 
		    outputChoice.add("SI: kw-hours"); 
		    outputChoice.add("SI: hp");
	
		} else if (cb == length) {
		    complex = false; 
		    // Assign appropriate factors
		    factorArray = lengthFactor();
		    
		    inputChoice.add("US: inch");
		    inputChoice.add("US: feet");
		    inputChoice.add("US: yard");
		    inputChoice.add("US: mile");
		    inputChoice.add("SI: mm");
		    inputChoice.add("SI: cm");
		    inputChoice.add("SI: m");
		    inputChoice.add("SI: km");
			    
		    outputChoice.add("US: inch");
		    outputChoice.add("US: feet");
		    outputChoice.add("US: yard");
		    outputChoice.add("US: mile");
		    outputChoice.add("SI: mm");
		    outputChoice.add("SI: cm");
		    outputChoice.add("SI: m");
		    outputChoice.add("SI: km");
	
		} else if (cb == pressure) {
		    complex = false; 
		    // Assign appropriate factors		    
		    factorArray = pressureFactor();
		    
		    inputChoice.add("US: psi");
		    inputChoice.add("US: psf");
		    inputChoice.add("US: mmHg, Torr");
		    inputChoice.add("US: atmospheres");
		    inputChoice.add("SI: Pascals");
		    inputChoice.add("SI: microbar");
		    inputChoice.add("SI: millibar");
		    inputChoice.add("SI: bar");  
		    inputChoice.add("SI: N/sq. mm.");
	
		    outputChoice.add("US: psi");
		    outputChoice.add("US: psf"); 
		    outputChoice.add("US: mmHg, Torr");
		    outputChoice.add("US: atmospheres");
		    outputChoice.add("SI: Pascals");
		    outputChoice.add("SI: microbar"); 
		    outputChoice.add("SI: millibar");
		    outputChoice.add("SI: bar");
		    outputChoice.add("SI: N/sq. mm.");
	
		} else if (cb == velocity) {
		    complex = false; 
		    // Assign appropriate factors		    
		    factorArray = velocityFactor();
		    
		    inputChoice.add("US: mph");
		    inputChoice.add("US: knots");
		    inputChoice.add("SI: km/h");
		    inputChoice.add("SI: m/s");
	  
		    outputChoice.add("US: mph");
		    outputChoice.add("US: knots");
		    outputChoice.add("SI: km/h");
		    outputChoice.add("SI: m/s");
			
		} else if (cb == volume) {
		    complex = false; 
		    // Assign appropriate factors		    
		    factorArray = volumeFactor();
		    
		    inputChoice.add("US: inch"); 
		    inputChoice.add("US: feet");
		    inputChoice.add("US: yard");
		    inputChoice.add("US: fl. ounces"); 
		    inputChoice.add("US: liq. pints");
		    inputChoice.add("US: liq. quarts");
		    inputChoice.add("US: gallon");
		    inputChoice.add("SI: mL"); 
		    inputChoice.add("SI: L");
		    inputChoice.add("SI: m"); 	    
		    
		    outputChoice.add("US: inch"); 
		    outputChoice.add("US: feet");
		    outputChoice.add("US: yard");
		    outputChoice.add("US: fl. ounces");
		    outputChoice.add("US: liq. pints"); 
		    outputChoice.add("US: liq. quarts");
		    outputChoice.add("US: gallon");
		    outputChoice.add("SI: mL");
		    outputChoice.add("SI: L");
		    outputChoice.add("SI: m");
	
		} else if (cb == weight) {
		    complex = false; 
		    // Assign appropriate factors		    
		    factorArray = weightFactor();
		    
		    inputChoice.add("US: drams");
		    inputChoice.add("US: ounces");
		    inputChoice.add("US: pounds");
		    inputChoice.add("US: hundredweight");
		    inputChoice.add("US: long ton");
		    inputChoice.add("SI: g");
		    inputChoice.add("SI: kg");
		    inputChoice.add("SI: t");
		    
		    outputChoice.add("US: drams");
		    outputChoice.add("US: ounces");
		    outputChoice.add("US: pounds");
		    outputChoice.add("US: hundredweight");
		    outputChoice.add("US: long ton");
		    outputChoice.add("SI: g");
		    outputChoice.add("SI: kg");
		    outputChoice.add("SI: t");
		    
		} else if (cb == temperature) {
		    // Converting involves addition or subtraction
		    complex = true;
		    
		    inputChoice.add("US: F");
		    inputChoice.add("SI: C");
		    
		    outputChoice.add("US: F");
		    outputChoice.add("SI: C");		   
		}
		
    }

    public void paint(Graphics g) {		
		g.setFont(new Font("", Font.BOLD, 20));	
		g.setColor(new Color(0, 0, 150));
	    g.drawString("Units Converter", 110, 30);
	    g.setFont(new Font("", Font.BOLD, 11));    
	    g.drawString("by H.Joon Kim", 270, 200);        
    }
    
    //////////////////////////////////////////////////////////////////////////////////
    //
    // The following methods return the appropriate converting factors to the caller.
    //
    private static double[] areaFactor() {	
		double cFactor[] = {0.0006452, 0.0929, 0.8361, 2590000, 0.0001, 1.0, 100, 1000000};
		return cFactor;
    }

    private static double[] energyFactor() {
		double cFactor[] = {0.112985, 1.35582, 1055.06, 4186.8, 1.0, 3600000, 2647800};
		return cFactor;
    }

    private static double[] lengthFactor() {		
		double cFactor[] = {0.0254, 0.3048, 0.9144, 1609.344, 0.001, 0.01, 1.0, 1000.0};
		return cFactor;
    }

    private static double[] pressureFactor() {
		double cFactor[] = {6894.76, 47.8803, 133.322, 101325, 1.0, 0.1, 100, 100000, 1000000};
		return cFactor;
    }

    private static double[] velocityFactor() {
		double cFactor[] = {1.60934, 1.852, 1.0, 3.6};
		return cFactor;
    }

    private static double[] volumeFactor() {
		double cFactor[] = {0.01639, 28.3168, 764.555, 0.029574, 0.47318, 0.94625, 3.785, 0.001, 1.0, 1000};
		return cFactor;
    }

    private static double[] weightFactor() {
		double cFactor[] = {0.00177184, 0.02834, 0.45359, 45.3592, 907.19404, 0.001, 1.0, 1000.0};
		return cFactor;
    }       
    //
    ////////////////////////////////////////////////////////////////////////////////////
    
    // Convert temperature between Fahrenheit and Celsius.
    private static double doComplexConversion(double base, int inputIndex, int outputIndex) {
        if (inputIndex == 0 && outputIndex == 1) {
            return ((base - 32.0)*(5.0/9.0));            
        } 
        else if (inputIndex == 1 && outputIndex == 0) {
            return (base*(9.0/5.0) +32);
        }
        else {
            return base;
        }        
    }
    
}