import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
/**
 * This Applet gives a number conversion test, designed for the page: 
 * http://www.ib-computing.com/program/core/number_systems.html
 * 
 * @author Richard Jones
 * @version September 2004 
 */
public class BinDecHexText extends Applet implements ActionListener
{
  // GUI objects
  private Label explain = new Label( "Click new to get a problem, fill in " 
                                   + "the empty boxes, press Check answer.");
  private TextField bin_t = new TextField(10);
  private TextField dec_t = new TextField(10);
  private TextField hex_t = new TextField(10);
  private Label bin_l = new Label("binary:", Label.RIGHT);
  private Label dec_l = new Label("decimal:", Label.RIGHT);
  private Label hex_l = new Label("hexadecimal:", Label.RIGHT);
  private Button bin_b = new Button("new");
  private Button dec_b = new Button("new");
  private Button hex_b = new Button("new");
  private Button check = new Button("Check answer");
  private Label messages = new Label("Any system messages will appear here");
  
  // data members
  private boolean answered;
  private String currentProblem;
  private int currentAnswer;  
  /** 
   * Set up the Applet
   */
  public void init()
  {
    add(explain);
    // main Panel
    Panel main = new Panel();
    main.setLayout(new GridLayout(3, 3, 5, 5));
    main.add(bin_l); main.add(bin_t); main.add(bin_b);
    main.add(dec_l); main.add(dec_t); main.add(dec_b);
    main.add(hex_l); main.add(hex_t); main.add(hex_b);
    Panel system = new Panel();
    // Check answer button and message label
    system.setLayout(new GridLayout(2, 1, 5, 5));
    system.add(check);
    system.add(messages);
    add(main);
    add(system);
    // Causes button presses to be detected
    // set the listeners
    bin_b.addActionListener(this);
    dec_b.addActionListener(this);  
    hex_b.addActionListener(this);  
    check.addActionListener(this);
    // Initial states - set a binary problem
    answered = false;
    currentProblem = "bin";
    currentAnswer = (int) (100 + Math.random() * 156);
    newBinaryProblem(currentAnswer);  
  }
  /** 
   * Detects button presses and acts on them  
   * 
   * @param e carries details about the event that occurred
   */
  public void actionPerformed(ActionEvent e)
  {
    // see if the question has been answered correctly
    messages.setText("");
    if (e.getSource() == check)
    {
      if (checkAnswers())   // problem completed
      {
        messages.setText("Yes, well done");
        answered = true;
        clearBoxes();
        currentAnswer = (int) (100 + Math.random() * 156);
      }
      else
      {
          messages.setText("Sorry, not yet, please try again");
          answered = false;
      }
    }
    if (answered)   // if it was anwered correctly allow a new problem
    {
      // check the button presses
      if(e.getSource() == bin_b)
      {
        newBinaryProblem(currentAnswer);
        currentProblem = "bin";
      }
      else if (e.getSource() == dec_b)
      {
        newDecimalProblem(currentAnswer);
        currentProblem = "dec";
      }
      else if (e.getSource() == hex_b)
      {
        newHexProblem(currentAnswer);
        currentProblem = "hex";
      }
    }  
  } 
  /** 
   * Clears the text boxes and messages  
   */
  private void clearBoxes()
  {
    bin_t.setEnabled(true);
    dec_t.setEnabled(true);
    hex_t.setEnabled(true);      
    bin_t.setText("");
    dec_t.setText("");
    hex_t.setText("");
    bin_t.setBackground(Color.WHITE);
    dec_t.setBackground(Color.WHITE);
    hex_t.setBackground(Color.WHITE);
  }
  /** 
   * Sets a new binary conversion problem  
   */
  private void newBinaryProblem(int n)
  {
    bin_t.setText(Integer.toBinaryString(n));
    bin_t.setEnabled(false);
  }
  /** 
   * Sets a new decimal conversion problem  
   */
  private void newDecimalProblem(int n)
  {
    dec_t.setText(Integer.toString(n));
    dec_t.setEnabled(false);
  }
  /** 
   * Sets a new hexadecimal conversion problem  
   */
  private void newHexProblem(int n)
  {
    hex_t.setText(Integer.toHexString(n).toUpperCase());
    hex_t.setEnabled(false);
  }
  /** 
   * Checks the answers
   * 
   * @return true if the answers were correct
   */
  private boolean checkAnswers()
  {
    boolean correct = false;
    if (currentProblem.equals("bin"))
    {
      // Check the decimal and hexadecimal answers
      String hexAnswer = hex_t.getText().trim().toLowerCase();
      String decAnswer = dec_t.getText().trim(); 
      boolean hex_c = (hexAnswer.equals(Integer.toHexString(currentAnswer)));
      boolean dec_c = (decAnswer.equals(Integer.toString(currentAnswer)));
      setTextFieldColour(hex_t, hex_c);
      setTextFieldColour(dec_t, dec_c);
      correct = (hex_c && dec_c);
    }
    else if (currentProblem.equals("dec"))
    {
      // Check the binary and hexadecimal answers
      String hexAnswer = hex_t.getText().trim().toLowerCase();
      String binAnswer = bin_t.getText().trim();      
      boolean hex_c = (hexAnswer.equals(Integer.toHexString(currentAnswer)));
      boolean bin_c = (binAnswer.equals(Integer.toBinaryString(currentAnswer)));
      setTextFieldColour(hex_t, hex_c);
      setTextFieldColour(bin_t, bin_c);
      correct = (hex_c && bin_c);
    }
    else if (currentProblem.equals("hex"))
    {
      // Check the binary and decimal answers
      String decAnswer = dec_t.getText().trim();
      String binAnswer = bin_t.getText().trim();      
      boolean dec_c = (decAnswer.equals(Integer.toString(currentAnswer)));
      boolean bin_c = (binAnswer.equals(Integer.toBinaryString(currentAnswer)));
      setTextFieldColour(dec_t, dec_c);
      setTextFieldColour(bin_t, bin_c);
      correct = (dec_c && bin_c);
    }
    return correct;
  }
  /** 
   * Sets the background colour of the TextField
   *
   * @param the TextField to set the background colour of
   * @param the state to set - true (correct) or false
   */
  private void setTextFieldColour(TextField tf, boolean state)
  {
    if (state)
    {
      tf.setBackground(Color.GREEN);
    }
    else
    {
      tf.setBackground(Color.RED);
    }
  }
}