/*
 * File: TemperatureApplet.java
 * Author: Java, Java, Java
 * Description: This applet provides a GUI to test the Temperature class.
 */

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

public class TemperatureApplet extends Applet implements ActionListener
{
    private TextField inField = new TextField(15);     // GUI components
    private TextField resultField = new TextField(15);
    private Label prompt1 = new Label("Input Temperature >>");
    private Label prompt2 = new Label("Conversion Result:");
    private Button celsToFahr = new Button("C to F");
    private Button fahrToCels = new Button("F to C");

    private Temperature temperature = new Temperature();  // The temperature object

    /**
     *  init() sets up the applet's interface
     */
    public void init()
    {                      // Set up the user interface
        add(prompt1);        // Input elements
        add(inField);
        add(celsToFahr);     // Control buttons
        add(fahrToCels);
        add(prompt2);        // Output elements
        add(resultField);
        celsToFahr.addActionListener(this);  // Register buttons with listeners
        fahrToCels.addActionListener(this);
        setSize(175,200);
    } // init()

    /**
     *  actionPerformed() handles clicks on the applet's two buttons. Note
     *   that the TextField input must be converted from String to double.
     *  @param e -- the ActionEvent that caused this method to be called
     */
    public void actionPerformed(ActionEvent e)
    {
        String inputStr = inField.getText();                 // Get user's input
        double userInput = convertStringTodouble (inputStr); // Convert it to double
        double result = 0;

        if (e.getSource() == celsToFahr) {                   // Process and report
            result = temperature.celsToFahr(userInput);
            resultField.setText(inputStr + " C = " + result  + " F \n");
        } else {
            result = temperature.fahrToCels(userInput);
            resultField.setText(inputStr + " F = " +  result  + " C \n");
        }
    } // actionPerformed

    /**
     *  convertStringTodouble() converts a String of the form "54.87" into
     *  its corresponding double value (54.87).
     *  @param s -- stores the string to be converted
     *  @return A double is returned
     */
    private double convertStringTodouble(String s)
    {
        return Double.valueOf(s).doubleValue();
    }
} // end of TemperatureApplet