/*
Project for CS 131
Michael Hecht

Note: the Integer class built-in to Java does not have any "set...()" methods,
making aliases useless. That's where Int comes in.

*/

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

//---Convert class---
public class Convert extends Applet
implements TextListener {

  private int numUnits=3;
  private String[] unitNames={"Fahrenheit","Celcius","Kelvin"};
  private double[] unitScale={9.0/5.0,1,1};
  private double[] unitShift={32,0,-273};

  private Int sourcePos=new Int(0); //index of source unit
  private Int targetPos=new Int(0); //index of target unit

  private Label conversionSourceUnitLabel=new Label();
  private Label conversionTargetUnitLabel=new Label();
  private Label conversionTargetUnitLabelSf=new Label();
  private TextField result=new TextField();
  private TextField resultSf=new TextField();

  private TextField sourceField=new TextField("0");

  private Panel topPanel=new Panel();
  private Panel bottomPanel=new Panel();
  private Panel sourcePanel=new Panel();
  private Panel destPanel=new Panel();
  private Panel unitPanel=new Panel();
  private Panel valuePanel=new Panel();

  //---applet's init() function---
  public void init() {
    result.setEditable(false);
    resultSf.setEditable(false);
    setBackground(new Color(.85f,.85f,.85f));
    setLayout(new BorderLayout());
    add(topPanel,BorderLayout.NORTH);
    add(bottomPanel,BorderLayout.CENTER);

    topPanel.add(new Label("Unit Converter for Temperature"));

    bottomPanel.setLayout(new BorderLayout());
    bottomPanel.add(unitPanel,BorderLayout.NORTH);
    bottomPanel.add(valuePanel,BorderLayout.SOUTH);

    unitPanel.setLayout(new BorderLayout());
    unitPanel.add(sourcePanel,BorderLayout.WEST);
    unitPanel.add(destPanel,BorderLayout.EAST);

    valuePanel.setLayout(new GridLayout(0,3));
    valuePanel.add(new Label("Original Temperature: ",Label.RIGHT));
    valuePanel.add(sourceField);
    sourceField.addTextListener(this);
    valuePanel.add(conversionSourceUnitLabel);

    valuePanel.add(new Label("Converted Temperature (sf): ",Label.RIGHT));
    valuePanel.add(resultSf);
    valuePanel.add(conversionTargetUnitLabelSf);

    valuePanel.add(new Label("Converted Temperature: ",Label.RIGHT));
    valuePanel.add(result);
    valuePanel.add(conversionTargetUnitLabel);




    sourcePanel.setLayout(new BorderLayout());
    sourcePanel.add(new UnitBox("Source Units",sourcePos),BorderLayout.WEST);

    destPanel.setLayout(new BorderLayout());
    destPanel.add(new UnitBox("Target Units",targetPos),BorderLayout.EAST);

    doConversion();

    } //end init() function

  //---function doConversion(): performs conversion and updates all fields---
  public void doConversion() {

    try {
      double s=(Double.valueOf(sourceField.getText()).doubleValue());
      double t=(s - unitShift[sourcePos.value]) / unitScale[sourcePos.value] * unitScale[targetPos.value] + unitShift[targetPos.value];

      result.setText(String.valueOf(t));
      int sf=countSigFigs(sourceField.getText());
      int tBaseSf=countSigFigs(String.valueOf(Math.round(Math.abs(t))));
      t=Math.round(t*Math.pow(10,sf-tBaseSf))/Math.pow(10,sf-tBaseSf);

      resultSf.setText(String.valueOf(t));

      conversionSourceUnitLabel.setText("degrees " + unitNames[sourcePos.value].toLowerCase());
      conversionTargetUnitLabelSf.setText("degrees " + unitNames[targetPos.value].toLowerCase() + " (sf)");
      conversionTargetUnitLabel.setText("degrees " + unitNames[targetPos.value].toLowerCase());

      }
    catch(Exception e) {
      result.setText("n/a");
      conversionTargetUnitLabel.setText("");
      resultSf.setText("n/a");
      conversionTargetUnitLabelSf.setText("");

      }

    } //end doConversion()

  public void textValueChanged(TextEvent t) {
    doConversion();
    }

  public int countSigFigs(String s) {
    int i=0,n=0;
    while(i<s.length() && (s.charAt(i)=='0' || s.charAt(i)=='-')) i++;
    for(;i<s.length();i++) {
      if(Character.isDigit(s.charAt(i))) n++;
      else if(s.charAt(i)=='.') {
        }
      else break;
      }
    return (n>0)?n:1;
    }


  //---class UnitBox---
  private class UnitBox extends Panel
  implements ItemListener {
    private CheckboxGroup unitGroup=new CheckboxGroup();
    private Checkbox[] unitType=new Checkbox[numUnits];
    private Int myIndex;

    //---UnitBox constructor---
    public UnitBox(String label,Int myIndex) {
      this.myIndex=myIndex; //REFERENCE to index in outer class
      setLayout(new GridLayout(0,1));
      add(new Label(label));
      for(int i=0;i<numUnits;i++) {
        unitType[i]=new Checkbox(unitNames[i],unitGroup,false);
        add(unitType[i]);
        unitType[i].addItemListener(this);
        }
      unitType[0].setState(true);

      } //end UnitBox constructor

    //---itemListener implementation---
    public void itemStateChanged(ItemEvent e) {
      Object source=e.getSource();
      for(int i=0;i<numUnits;i++) {
        if(source==unitType[i]) {
          if(myIndex.value!=i) {
            myIndex.value=i;
            doConversion(); //call function to convert units in outer class
            }
          }
        }
      } //end itemListener implementation
    } //end UnitBox class

    //---class Int, for int pass/store by reference
    public class Int {
      public int value;

      Int(int value) {
        this.value=value;
        }
      } //end class Int


  } //end Convert class