/**
* This Applet demonstrates the use of 2D arrays and some aspects of String
* processing.
*
* A square of letters is provided, clicking on a square changes the letter
* in the square either up or down the list of allowable characters.
*
* It could form a starting point for some entertaining games...
*/
import java.awt.*;
import java.awt.event.*;
import java.applet.Applet;

public class WordSquare extends java.applet.Applet implements ActionListener
{
  static final int ROWS = 5; // number of rows in the word square
  static final int COLS = 5; // number of columns in the word square

  // The set of allowable characters in the alphabet
  static final String ALLOWABLE = "*abcdefghijklmnopqrstuvwxyz ,.";

  // When clicked, the square goes up one letter or down according to
  // the value in direction
  int direction = 1;

  Button square [][] = new Button[ROWS][COLS]; // button grid;
  Button increment = new Button ("inc");       // increment letters
  Button decrement = new Button ("dec");       // decrement letters

  /*
   * This method initialises the Applet and sets up the display
   */
  public void init()
  {
    // a panel for the button grid
    Panel theSquare = new Panel();
    theSquare.setLayout( new GridLayout(ROWS, COLS) );

    // for each array element
    for (int c = 0; c < COLS; c++)
    {
      for (int r = 0; r < ROWS; r++)
      {
        int start = 0; // starting letter

        // take single letter from string of allowable characters
        square[r][c] = new Button(ALLOWABLE.substring(start, ++start) );
        theSquare.add( square[r][c] );        // add the element
        square[r][c].addActionListener(this); // add action listener
      }
    }
    add(theSquare); // add the button panel
    add(increment); // add the inc and dec buttons
    add(decrement); // and listen for presses on them
    increment.addActionListener(this);
    decrement.addActionListener(this);

    increment.setEnabled(false); // disable the increment button at the start
  }
  
  /*
   * This method listens for the Button presses and processes them
   * 
   * @param the Button which caused the method to be executed
   */
  public void actionPerformed(ActionEvent e)
  {
    for (int c = 0; c < COLS; c++)
    {
      for (int r = 0; r < ROWS; r++)
      {
        // find out which element was clicked
        if (e.getSource() == square[r][c]) 
        {
          // get the current letter value from the button label and 
          // work out what the next one should be.
          int start = ALLOWABLE.indexOf( square[r][c].getLabel() );
          start = (start + direction);

          // check to see if we went out of range
          if (start >= ALLOWABLE.length())
          {
            start = 0;
          }
          if (start < 0)
          {
            start = ALLOWABLE.length()-1;
          } 

          // set the label to the new letter
          square[r][c].setLabel(ALLOWABLE.substring(start, ++start));
        }
      }
    }
    // check for a press on increment/decrement buttons
    if (e.getSource() == increment) // increment clicked
    {
      increment.setEnabled(false);  // disable it
      decrement.setEnabled(true);   // enable the decrement button
      direction = 1;                // set direction up
    }
    if (e.getSource() == decrement) // decrement clicked
    {
      increment.setEnabled(true);   // similar process
      decrement.setEnabled(false); 
      direction = -1;               // except direction down
    }
  }
}