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

/**
 * The "model" (vs. user interface) part of this program
 */
public class Model {
    /** Model or application data */
    private ArrayList<Square> squares = new ArrayList<Square> ();
    private boolean drawX = false;

    private Canvas canvas;
    private Square current; //*2 Private = no other class can cause the bug

    public Model (int n, Canvas canvas) {
	// Stash ivar
	this.canvas = canvas;

	// Create the n objects
	for (int i=0; i<n; i++) {
	    squares.add (new Square(canvas));
	}

	// Initialize to some arbitrary square so current is never null
	Square current = squares.get(0); //*1 Initialize current

	// assert => we expect this always to be true
	assert current != null; //*4 Should always be true
    }

    public void draw (Graphics g) {
	// The background X
	if (drawX) {
	    Dimension size = canvas.getSize();
	    g.drawLine (0, 0, size.width, size.height);
	    g.drawLine (0, size.height, size.width, 0);
	}

	// Enumerate our list
	for (Square s: squares) {
	    // N.B. (s==current) is a boolean expr,
	    // evaluates to true or false
	    s.draw (g, s==current);
	}

	assert current != null; //*4
    }

    public void setX (boolean newX) {
	drawX = newX;
	canvas.repaint();

	assert current != null; //*4
    }

    Square getCurrent () { //*3 We provided read-only access to current
	assert current != null; //*4
	return current; //*3
    }

    public void doMouse (Point p) {
	for (Square s: squares) {
	    if (s.isInside(p)) {
		current = s;
		break;
	    }
	}
	
	canvas.repaint();

	assert current != null; //*4
    }
}