#format java
/**
 * CommandPattern example
 */

import java.util.*;
import java.util.Iterator;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

interface Command {
    public abstract void execute();
}

class MacroCommand implements Command {
    private Stack commands = new Stack();  // for easy undo use Stack
    public void execute() {  // using Recursion
        Iterator it = commands.iterator();
        while(it.hasNext()) {
            ((Command)it.next()).execute();
        }
    }
    public void append(Command cmd) {
        if(cmd != this) {
            commands.push(cmd);
        }
    }
    public void undo() {
        if(!commands.empty()) {
            commands.pop();
        }
    }
    public void clear() {
        commands.clear();
    }
}

class DrawCommand implements Command {
    protected Drawable drawable;
    private Point position;
    public DrawCommand(Drawable drawable, Point position) {
        this.drawable = drawable;
        this.position = position;
    }
    public void execute() {
        drawable.draw(position.x, position.y);
    }
}

interface Drawable {
    public abstract void draw(int x, int y);
}

class DrawCanvas extends Canvas implements Drawable {
    private Color color = Color.red;
    private int radius = 6;
    private MacroCommand history;
    public DrawCanvas(int width, int height, MacroCommand history) {
        setSize(width, height);
        setBackground(Color.white);
        this.history = history;
    }
    // entire drawing using MacroCommand
    public void paint(Graphics g) {
        history.execute();
    }
    public void draw(int x, int y) {
        Graphics g = getGraphics();
        g.setColor(color);
        g.fillOval(x-radius, y-radius, radius*2, radius*2);
    }
}

public class CommandDrawer extends JFrame implements ActionListener, 
        MouseMotionListener, WindowListener {
    private MacroCommand history = new MacroCommand();
    private DrawCanvas canvas = new DrawCanvas(400,400,history);
    private JButton clearButton = new JButton("clear");
    public CommandDrawer(String title) {
        super(title);
        this.addWindowListener(this);
        canvas.addMouseMotionListener(this);
        clearButton.addActionListener(this);

        Box buttonBox = new Box(BoxLayout.X_AXIS);
        buttonBox.add(clearButton);
        Box mainBox = new Box(BoxLayout.Y_AXIS);
        mainBox.add(buttonBox);
        mainBox.add(canvas);
        getContentPane().add(mainBox);
        pack();
        setVisible(true);
    }
    
    // ActionListener implementation
    public void actionPerformed(ActionEvent e) {
        if(e.getSource() == clearButton) {
            history.clear();
            canvas.repaint();
        }
    }
    public void mouseMoved(MouseEvent e) {
    }
    // when mouse event, creat command to draw oval and execute
    public void mouseDragged(MouseEvent e) {
        Command cmd = new DrawCommand(canvas, e.getPoint());
        history.append(cmd);
        cmd.execute();
    }

    public void windowClosing(WindowEvent e) {
        System.exit(0);
    }
    public void windowActivated(WindowEvent e) {}
    public void windowClosed(WindowEvent e) {}
    public void windowDeactivated(WindowEvent e) {}
    public void windowDeiconified(WindowEvent e) {}
    public void windowIconified(WindowEvent e) {}
    public void windowOpened(WindowEvent e) {}

    public static void main(String[] args) {
        new CommandDrawer("Command Pattern Sample");
    }
}