import javax.swing.*;
import javax.swing.plaf.*;
import java.awt.*;
import java.awt.event.*;
import java.util.*;
   
/**
 * DrawPanel implements a JPanel that can be drawn on using
 * the mouse
 * 
 * @author Stuart Hansen 
 * @version September 28, 2008
 */
 
// We specialize the JPanel to contain a drawing.
public class DrawPanel extends JPanel
{
   
   // The model used for the JPanel is a list of curves.    
   ArrayList<Curve> listOfCurves;
   
   // Two additional state variables to aid us in creating the drawing
   Curve  currentCurve;     // the current curve being drawn
   Color  currentColor;     // the current drawing color
 
   public DrawPanel()
   {
      super();
      
      // Initialize the model
      reset();
            
      // replace the view
      setUI (new DrawPanelUI());
      
      // add specialized control
      addMouseListener(new MouseHandler());
      addMouseMotionListener(new MouseMotionHandler());

   }
   
   // A setter for the color
   public void setColor(Color col)
   {
      currentColor = col;
   }
   
   // a getter for the color
   public Color getColor()
   {
      return currentColor;
   }
   
   // reset the drawPanel model
   public void reset()
   {
      listOfCurves = new ArrayList<Curve>();
      currentColor = Color.BLACK;
		repaint();
   }       
   
   // Each curve has a color and a list of points.
   // The points form a series of line segments, so it is really a poly-Line,
   // not a true curve.
   // We use an inner class to model the curve.
   private class Curve 
   {
      private Color color;                // the color of the curve
      private ArrayList<Point> points;  // the points on the curve

      // the constructor initializes the color and the list
      public Curve (Color c, Point p)
      {
         color = c;
         points = new ArrayList<Point>();
         points.add(p);
      }
      
      // get the Color
      Color getColor()
      {
         return color;
      }
      
      // returns an iterator over the points      
      public Iterator<Point> iterator()
      {
         return points.iterator();
      }
      
      // adds a Point
      public void add (Point p)
      {
         points.add(p);
      }
   }
      
   // The DrawPanelUI class knows how to display the drawing
   private class DrawPanelUI extends ComponentUI
   {
      public void paint (Graphics g, JComponent c) {                
         // We iterate across the list of curves, drawing each
         Iterator<Curve> curveIterator = listOfCurves.iterator();
         while (curveIterator.hasNext()) {
       
            // We iterate across each curve drawing it
            Curve curve = curveIterator.next();
            Iterator<Point> pointIterator = curve.iterator();
       
            // The first thing in a curve is its color
            g.setColor(curve.getColor());
       
            // The remainder of the curve is a sequence of Points
            Point p1 = pointIterator.next();
                          
            while (pointIterator.hasNext()) {
               Point p2 = pointIterator.next();
               g.drawLine((int)p1.getX(), (int)p1.getY(),
                        (int)p2.getX(), (int)p2.getY());
               p1 = p2;
            }
         }         
      }
   }
   
   // The following event handlers are part of the JPanel's control   
   // This class 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) {
         if (SwingUtilities.isLeftMouseButton(e)){
            currentCurve = new Curve(currentColor, e.getPoint());
            currentCurve.add(e.getPoint());
            listOfCurves.add(currentCurve);
         }
      }
   }

}