/* Copyright (C) 2002 J. M. Spivey */

import java.awt.*;
import java.awt.event.*;

/** Main class for the CountDown applet
 * 
 * This class presents the GUI for the applet.  The only interesting 
 * aspect is the random selection of numbers, where we want to make 
 * all (N choose K) selections equally likely.
 */
public class CountDown extends DemoFrame {
    public static final int N = 6;
    
    Panel panel0 = new Panel(new FlowLayout());
    Panel panel0a = new Panel(new FlowLayout());
    Panel panel1 = new Panel(new BorderLayout(5,5));
    Panel panel1a = new Panel(new GridLayout(4,1));
    Panel panel1b = new Panel(new GridLayout(5,4));
    Panel panel1c = new Panel();                              
    Panel panel2 = new Panel(new BorderLayout(5,5));
    Panel panel2a = new Panel();
    Panel panel2b = new Panel();
    Panel panel3 = new Panel();
    TextField solution = new TextField(50);
    Button solveButton;
    TextField target = new TextField(3);
    int targval;
    
    Checkbox bigCheck[] = new Checkbox[4];
    Checkbox smallCheck[] = new Checkbox[20];
    int bigNums[] = { 25, 50, 75, 100 };
    int nchoices = 0;
        // Number of numbers chosen
    Checkbox choices[] = new Checkbox[N];
        // The checkboxes for the chosen numbers
                                       
    private Button addButton(String name, Panel p, ActionListener action) {
        Button b = new Button(name);
        b.addActionListener(action);
        p.add(b);
        return b;
    }
    
    private ItemListener checkListener = new ItemListener() {
            public void itemStateChanged(ItemEvent e) { 
                click((Checkbox) e.getSource()); }
        };
    
    private Checkbox addCheckbox(int value, Panel p) {
        Checkbox chk = new Checkbox(Integer.toString(value));
        chk.addItemListener(checkListener);
        p.add(chk);
        return chk;
    }
    
    
    public CountDown() {
        super("CountDown");
        
        add(panel0, "Center");
        panel0.add(panel1);
        panel1.add(panel1a, "East");
        panel1.add(panel1b, "West");
        panel1.add(panel1c, "South");
        add(panel0a, "East");
        panel0a.add(panel2);
        panel2.add(panel2a, "Center");
        panel2.add(panel2b, "South");
        add(panel3, "South");
        
        for (int i = 0; i < bigNums.length; i++)
            bigCheck[i] = addCheckbox(bigNums[i], panel1a);
        
        for (int i = 0; i < 5; i++) {
            smallCheck[2*i] = addCheckbox(i+1, panel1b);
            smallCheck[2*i+1] = addCheckbox(i+1, panel1b);
            smallCheck[2*i+10] = addCheckbox(i+6, panel1b);
            smallCheck[2*i+11] = addCheckbox(i+6, panel1b);
        }
        
        addButton("Clear", panel1c,
            new ActionListener() {
                public void actionPerformed(ActionEvent e) { clearChoices(); }
            });
        addButton("Random", panel1c,
            new ActionListener() {
                public void actionPerformed(ActionEvent e) { randomChoices(); }
            });
        solveButton = addButton("Solve", panel1c,
            new ActionListener() {
                public void actionPerformed(ActionEvent e) { solve(); }
            });
        solveButton.setEnabled(false);
        addButton("Quit", panel1c,
            new ActionListener() {
                public void actionPerformed(ActionEvent e) { die(); }
            });
        
        Font targetFont = new Font("Sans", Font.PLAIN, 20);
        target.setFont(targetFont);
        target.setForeground(Color.green);
	target.setBackground(Color.black);
        target.addTextListener(new TextListener() {
                public void textValueChanged(TextEvent e) { checkState(); }
            });
        target.addActionListener(new ActionListener() {
                public void actionPerformed(ActionEvent e) {
                    if (solveButton.isEnabled()) solve();
                }
            });
        panel2a.add(target);
        
        addButton("Random", panel2b,
            new ActionListener() {
                public void actionPerformed(ActionEvent e) { randomTarget(); }
            });
        
                
        Font solutionFont = new Font("Monospaced", Font.PLAIN, 12);
        solution.setFont(solutionFont);
        solution.setEditable(false);
        panel3.add(solution);
        
        pack();
        setResizable(false);
    }
    
    /** Respond to a state change for a checkbox */
    private void click(Checkbox chk) {
        boolean state = chk.getState();
        
        if (state) {
            // A new choice
            if (nchoices == N) {
                // Undo the oldest choice, so there are never more than N
                nchoices--;
                choices[0].setState(false);
                for (int i = 0; i < nchoices; i++)
                    choices[i] = choices[i+1];
            }
            choices[nchoices++] = chk;
        } else {
            // Cancelling an old choice
            nchoices--;
            int j = 0;
            while (choices[j] != chk) j++;
            for (int i = j; i < nchoices; i++)
                choices[i] = choices[i+1];
        }
        
        checkState();
    }
    
    private void clearChoices() {
        for (int i = 0; i < bigCheck.length; i++)
            bigCheck[i].setState(false);
        
        for (int i = 0; i < smallCheck.length; i++)
            smallCheck[i].setState(false);
        
        nchoices = 0;
        checkState();
    }
    
    private void randomChoices() {
        clearChoices();
        
        int big = (int) (4 * Math.random());
        bigCheck[big].setState(true);
        choices[nchoices++] = bigCheck[big];
        
        for (int i = 0; i < 20; i++) {
            // Choose checkbox i with the appropriate probability
            if (Math.random() < (double) (N - nchoices)/(20 - i)) {
                smallCheck[i].setState(true);
                choices[nchoices++] = smallCheck[i];
            }
        }
        
        checkState();
    }
    
    /** Choose a random target number */
    private void randomTarget() {
        // All numbers from 101 to 999 are equally likely
        target.setText(Integer.toString(101 + (int) (899 * Math.random())));
        checkState();
    }
    
    /** Return the chosen numbers as an array */
    private int[] draw() {
        int pick[] = new int[nchoices];
        int n = 0;
        
        for (int i = 0; i < 20; i++)
            if (smallCheck[i].getState())
                pick[n++] = i/2 + 1;
        
        for (int i = 0; i < 4; i++)
            if (bigCheck[i].getState())
                pick[n++] = bigNums[i];
        
        return pick;
    }
        
    /** Enable the Solve button if everything is ready for it */
    private void checkState() {
        // List the choices in the solution box
        StringBuffer buf = new StringBuffer();
        int pick[] = draw();
        for (int i = 0; i < pick.length; i++)
            buf.append(pick[i] + " ");
        solution.setText(buf.toString());
        
        // Check if we are ready to solve the problem
        boolean ok;
        try {
            targval = Integer.parseInt(target.getText());
            ok = (nchoices == N && targval > 0);
        } catch (NumberFormatException e) { 
            ok = false;
        }
        solveButton.setEnabled(ok);
    }
    
    /** Compute the best solution */
    private void solve() {
        solution.setText(Solver.Solve(draw(), targval));
    }
    
    public static void main(String args[]) {
        Frame frame = new CountDown();
        frame.setVisible(true);
    }
}