// Checkerboard.java
// Solution to Short Assignment 9 by THC.
// Draws a checkerboard with black and red squares.  Whichever square is
// clicked on flashes between its regular color and yellow.
// Uses private inner classes as listeners.

import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
import javax.swing.Timer;

public class Checkerboard extends Applet {
  private final int DIMENSION = 8; // Want 8 x 8 board
  private final int SQUARE_SIZE = 30; // Each square is 30 x 30 pixels

  private Point clickPoint; // Where the mouse was clicked
  private boolean clickedIsYellow;  // true if we're drawing the clicked point in yellow
  
  private Timer flashing; // Timer for the flashing square

  public void init() {
    // Set the size of the applet to be exactly the checkerboard size.
    setSize(DIMENSION * SQUARE_SIZE, DIMENSION * SQUARE_SIZE);
    
    // Nothing is clicked yet.
    clickPoint = null;
    clickedIsYellow = false;

    // Register this applet as the listener for mouse clicks.
    addMouseListener(new ClickListener());
    
    // Create the Timer for flashing and make this applet be the listener.
    final int DELAY = 500;
    flashing = new Timer(DELAY, new TimerListener());
    flashing.start();

    // Draw the initial checkerboard.
    repaint();
  }

  public void paint(Graphics page) {
    // Draw all the black and red squares.
    drawCheckerboard(page);

    // If we've clicked a point, and if we're in part of the Timer cycle when
    // we draw in yellow, then draw it in yellow.
    if (clickPoint != null && clickedIsYellow) {
      int row = clickPoint.y / SQUARE_SIZE; // Row that was clicked on
      int column = clickPoint.x / SQUARE_SIZE; // Column that was clicked on
      drawSquare(page, row, column, Color.yellow);
    }
  }

  // Draw the entire checkerboard in black and red.
  public void drawCheckerboard(Graphics page) {
    Color squareColor; // Color of the current square

    for (int row = 0; row < DIMENSION; row++) {
      for (int column = 0; column < DIMENSION; column++) {
        // A square is black if the row and column numbers are both even
        // or both odd. Otherwise, the square is red.
        if (row % 2 == column % 2)
          squareColor = Color.black;
        else
          squareColor = Color.red;

        drawSquare(page, row, column, squareColor);
      }
    }
  }

  // Draw a given square of the checkerboard. Row and column numbers start
  // from 0.
  public void drawSquare(Graphics page, int row, int column, Color color) {
    page.setColor(color);
    page.fillRect(column * SQUARE_SIZE, row * SQUARE_SIZE, SQUARE_SIZE,
        SQUARE_SIZE);
  }

  // Private inner class to listen for mouse events.
  private class ClickListener implements MouseListener {
    // Handle a mouse click by remembering the clicked point and repainting.
    public void mouseClicked(MouseEvent event) {
      // Save where the click was.
      clickPoint = event.getPoint();
  
      // Redraw the checkerboard with the square clicked on flashing yellow.
      clickedIsYellow = true;
  
      repaint();
    }
  
    // Provide empty definitions for unused event methods.
    public void mousePressed(MouseEvent event) {}
    public void mouseReleased(MouseEvent event) {}
    public void mouseEntered(MouseEvent event) {}
    public void mouseExited(MouseEvent event) {}
  }
  
  // Private inner class to handle timer events.
  private class TimerListener implements ActionListener {
    // Handle a timer event by reversing whether we draw the clicked square in yellow
    // and then repainting.
    public void actionPerformed(ActionEvent event) {
      clickedIsYellow = !clickedIsYellow;
      repaint();
    }
  }
}