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

/**
 * The DrawPanel contains everything for creating a drawing 
 * 
 * @author Stuart Hansen 
 * @version December 22, 2000
 * modified October 16, 2001 -- added alternative colors
 * modified February 5, 2002 -- made resizing work
 * modified February 4, 2003 -- changed to drawing with lines
 */
public class DrawPanel extends JPanel implements Serializable
{
    Vector vectorOfCurves;   // the drawing is a vector of curves
    Vector currentCurve;     // the current curve being drawn
 
    Color currentColor;      // the current drawing color
    
    /** the constructor sets up the panel */
    public DrawPanel ()
    {
        vectorOfCurves = new Vector();
        setBackground(Color.white);
        currentColor = Color.black;
        setUI(new DrawPanelUI());
        addMouseListener(new MouseHandler());
        addMouseMotionListener(new MouseMotionHandler());
    }
  
    /** get the current color */
    public Color getCurrentColor () {
        return currentColor;
    }

    /** set the current color */
    public void setCurrentColor (Color c) {
        currentColor = c;
    }

    /** clear the drawing */
    public void clear () 
    {
        vectorOfCurves = new Vector();
        repaint();
    }

    /** This inner class knows how to draw the DrawPanel */
    class DrawPanelUI extends ComponentUI
    {
        public void paint (Graphics g, JComponent c) {                
            // We iterate across the Vector of curves, drawing each
            Iterator curvesIterator = vectorOfCurves.iterator();
            while (curvesIterator.hasNext()) {
 
                // We iterate across each curve drawing it
                Vector curve = (Vector)curvesIterator.next();
                Iterator oneCurveIterator = curve.iterator();
 
                // The first thing in a curve is its color
                g.setColor((Color)oneCurveIterator.next());
 
                // The remainder of the curve is a sequence of Points
                Point p1 = (Point) oneCurveIterator.next();
                    
                while (oneCurveIterator.hasNext()) {
                    Point p2 = (Point) oneCurveIterator.next();
                    g.drawLine((int)p1.getX(), (int)p1.getY(),
                               (int)p2.getX(), (int)p2.getY());
                    p1 = p2;
                }
            }         
        }
    }

    /** This adds points to the current vector */
    private class MouseMotionHandler extends MouseMotionAdapter{
        public void mouseDragged (MouseEvent e){
            if (SwingUtilities.isLeftMouseButton(e)){
                currentCurve.add(e.getPoint());
                repaint(); 
            }
        }
    }

    /** When the mouse is pressed a new curve is started */
    private class MouseHandler extends MouseAdapter {
        public void mousePressed (MouseEvent e) {
            currentCurve = new Vector();
            currentCurve.add(currentColor);
            currentCurve.add(e.getPoint());
            vectorOfCurves.add(currentCurve);
        }
    }
}