/**
 * David Atkinson
 * IS6050
 * EX01: Create a GUI that calculates miles per gallon used
 * based on miles driven and gallons used
 */

package mpg;

import javax.swing.*; //Needed for JOptionPane
import java.awt.event.*; 
import java.text.DecimalFormat; //Needed for decimal format
        

public class MPGWindow extends JFrame 
//class needed to hold inputs, messages to user, window height/width
{
    private JPanel panel;
    private JLabel mpgCalc;
    private JLabel milesTrav;
    private JLabel galUsed;
    private JTextField mileTextField;
    private JTextField galTextField;
    private JButton calcButton;
    private JButton quitButton;
    private final int WINDOW_WIDTH = 255;
    private final int WINDOW_HEIGHT = 200;
    
    public MPGWindow() //Constructor
    {
        setTitle("MPG Calculator");
        setSize(WINDOW_WIDTH, WINDOW_HEIGHT);
        setLocationRelativeTo(null);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        buildPanel();
        add(panel);
        setVisible(true);
                 
    }
    
    private void buildPanel() //Adds label, text fields, buttons
    {
        mpgCalc = new JLabel();
        milesTrav = new JLabel("Miles Travelled:");
        galUsed = new JLabel("Gallons Used:");
        mileTextField = new JTextField(6);
        galTextField = new JTextField(6);
        calcButton = new JButton("Calculate MPG");
        quitButton = new JButton("Quit");
        calcButton.addActionListener(new CalcButtonListener());
        quitButton.addActionListener(new QuitButtonListener());
        panel = new JPanel();
        panel.add(mpgCalc);
        panel.add(milesTrav);
        panel.add(mileTextField);
        panel.add(galUsed);
        panel.add(galTextField);
        panel.add(calcButton);
        panel.add(quitButton);
            }
    
    private class CalcButtonListener implements ActionListener
    //Handles button clicks
    {
        public void actionPerformed(ActionEvent e)
        {
            double miles;
            double gallons;
            double mpg;
                miles = Double.parseDouble(mileTextField.getText());
                gallons = Double.parseDouble(galTextField.getText());
                mpg = miles/gallons;
                DecimalFormat formatter = new DecimalFormat("#00.00");
                JOptionPane.showMessageDialog(null, "Distance: " + formatter.format(miles) +
                        "\n Miles per Gallon: " + formatter.format(mpg));
            }
    }
    
    private class QuitButtonListener implements ActionListener {
        public void actionPerformed(ActionEvent e){
            System.exit(0);
                }
    }
}