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

/**
 * A SimplePaint2 panel is a drawing surface on which the user can
 * sketch curves.  The class has a createMenuBar() method that can
 * be used to get a menu bar containing drawing commands and options.
 * It has a main() routine that enables the class to be run as a
 * standalone application; the program just opens a window that 
 * shows a SimplePaint2 panel and its menu par.
 * 
 * The real point of this example is to demonstrate ArrayList<T>.
 */
public class SimplePaint2 extends JPanel {
   
   /**
    * main() routine opens a window that shows a SimplePaint2 panel
    * and its menu bar.  The program ends when the user closes the window.
    */
   public static void main(String[] args) {
      JFrame window = new JFrame("SimplePaint2");
      SimplePaint2 content = new SimplePaint2();
      window.setContentPane(content);
      window.setJMenuBar(content.createMenuBar());
      window.pack();
      window.setLocation(100,100);
      window.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
      window.setResizable(false);  
      window.setVisible(true);
   }
   
      
   /**
    * An object of type CurveData represents the data required to redraw one
    * of the curves that have been sketched by the user.
    */
   private static class CurveData {
      Color color;  // The color of the curve.
      boolean symmetric;  // Are horizontal and vertical reflections also drawn?
      ArrayList<Point> points;  // The points on the curve.
   }
   
   
   private ArrayList<CurveData> curves;  // A list of all curves in the picture.

   private Color currentColor;   // When a curve is created, its color is taken
                                 //     from this variable.  The value is changed
                                 //     using commands in the "Color" menu.

   private boolean useSymmetry;  // When a curve is created, its "symmetric"
                                 // property is copied from this variable.  Its
                                 // value is set by the "Use Symmetry" command in
                                 // the "Control" menu.

   
   /**
    * Constructor.  Sets background color to white, adds a gray border, sets up
    * a listener for mouse and mouse motion events, and sets the preferred size
    * of the panel to be 500-by-500.
    */
   public SimplePaint2() {
      curves = new ArrayList<CurveData>();
      setBackground(Color.WHITE);
      setBorder(BorderFactory.createLineBorder(Color.GRAY, 2));
      MouseHandler listener = new MouseHandler();
      addMouseListener(listener);
      addMouseMotionListener(listener);
      setPreferredSize( new Dimension(500,500) );
   }

   
   /**
    * This class defines the object that is used as a mouse listener and mouse
    * motion listener on this panel.  When the user presses the mouse, a new
    * CurveData object is created and is added to the ArrayList, curves. The
    * color of the curve is copied from currentColor, and the symmetric property
    * of the curve is copied from useSymmetry.  As the user drags the mouse, points
    * are added to the curve.  If the user doesn't move the mouse, there will only
    * be one point in the list of points; since this is not really a curve, the
    * CurveData objects is removed in this case from the curves list.  This is
    * done in the mouseReleased method.
    */
   private class MouseHandler implements MouseListener, MouseMotionListener {
      CurveData currentCurve;
      boolean dragging;
      public void mousePressed(MouseEvent evt) {
         if (dragging)
            return;
         dragging = true;
         currentCurve = new CurveData();
         currentCurve.color = currentColor;
         currentCurve.symmetric = useSymmetry;
         currentCurve.points = new ArrayList<Point>();
         currentCurve.points.add( new Point(evt.getX(), evt.getY()) );
         curves.add(currentCurve);
      }
      public void mouseDragged(MouseEvent evt) {
         if (!dragging)
            return;
         currentCurve.points.add( new Point(evt.getX(),evt.getY()) );
         repaint();  // redraw panel with newly added point.
      }
      public void mouseReleased(MouseEvent evt) {
         if (!dragging)
            return;
         dragging = false;
         if (currentCurve.points.size() < 2)
            curves.remove(currentCurve);
         currentCurve = null;
      }
      public void mouseClicked(MouseEvent evt) { }
      public void mouseEntered(MouseEvent evt) { }
      public void mouseExited(MouseEvent evt) { }
      public void mouseMoved(MouseEvent evt) { }
   } // end nested class MouseHandler
   
   
   /**
    * Fills the panel with the current background color and draws all the
    * curves that have been sketched by the user.
    */
   public void paintComponent(Graphics g) {
      super.paintComponent(g);
      for ( CurveData curve : curves) {
         g.setColor(curve.color);
         for (int i = 1; i < curve.points.size(); i++) {
               // Draw a line segment from point number i-1 to point number i.
            int x1 = curve.points.get(i-1).x;
            int y1 = curve.points.get(i-1).y;
            int x2 = curve.points.get(i).x;
            int y2 = curve.points.get(i).y;
            g.drawLine(x1,y1,x2,y2);
            if (curve.symmetric) {
                  // Also draw the horizontal and vertical reflections
                  // of the line segment.
               int w = getWidth();
               int h = getHeight();
               g.drawLine(w-x1,y1,w-x2,y2);
               g.drawLine(x1,h-y1,x2,h-y2);
               g.drawLine(w-x1,h-y1,w-x2,h-y2);
            }
         }
      }
   } // end paintComponent()
   
   
   /**
    * Creates a menu bar for use with this panel.  It contains
    * three menus: "Control", "Color", and "BackgroundColor".
    */
   public JMenuBar createMenuBar() {

      /* Create the menu bar object */
      
      JMenuBar menuBar = new JMenuBar();
      
      /* Create the menu bar and add them to the menu bar. */
      
      JMenu controlMenu = new JMenu("Control");
      JMenu colorMenu = new JMenu("Color");
      JMenu bgColorMenu = new JMenu("BackgroundColor");
      menuBar.add(controlMenu);
      menuBar.add(colorMenu);
      menuBar.add(bgColorMenu);
      
      /* Add commands to the "Control" menu.  It contains an Undo
       * command that will remove the most recently drawn curve
       * from the list of curves; a "Clear" command that removes
       * all the curves that have been drawn; and a "Use Symmetry"
       * checkbox that determines whether symmetry should be used.
       */
      
      JMenuItem undo = new JMenuItem("Undo");
      controlMenu.add(undo);
      undo.addActionListener( new ActionListener() {
         public void actionPerformed(ActionEvent evt) {
            if (curves.size() > 0) {
               curves.remove( curves.size() - 1);
               repaint();  // Redraw without the curve that has been removed.
            }
         }
      });
      JMenuItem clear = new JMenuItem("Clear");
      controlMenu.add(clear);
      clear.addActionListener( new ActionListener() {
         public void actionPerformed(ActionEvent evt) {
            curves = new ArrayList<CurveData>();
            repaint();  // Redraw with no curves shown.
         }
      });
      JCheckBoxMenuItem sym = new JCheckBoxMenuItem("Use Symmetry");
      controlMenu.add(sym);
      sym.addActionListener( new ActionListener() {
         public void actionPerformed(ActionEvent evt) {
            useSymmetry = ((JCheckBoxMenuItem)evt.getSource()).isSelected();
               // This does not affect the current drawing; it affects
               // curves that are drawn in the future.
         }
      });
      
      /* Add commands to the "Color" menu.  The menu contains commands for
       * setting the current drawing color.  When the user chooses one of these
       * commands, it has not immediate effect on the drawing.  It justs sets
       * the color that will be used for future drawing.
       */
      
      colorMenu.add(makeColorMenuItem("Black", Color.BLACK));
      colorMenu.add(makeColorMenuItem("White", Color.WHITE));
      colorMenu.add(makeColorMenuItem("Red", Color.RED));
      colorMenu.add(makeColorMenuItem("Green", Color.GREEN));
      colorMenu.add(makeColorMenuItem("Blue", Color.BLUE));
      colorMenu.add(makeColorMenuItem("Cyan", Color.CYAN));
      colorMenu.add(makeColorMenuItem("Magenta", Color.MAGENTA));
      colorMenu.add(makeColorMenuItem("Yellow", Color.YELLOW));
      JMenuItem customColor = new JMenuItem("Custom...");
      colorMenu.add(customColor);
      customColor.addActionListener( new ActionListener() { 
             // The "Custom..." color command lets the user select the current
             // drawing color using a JColorChoice dialog.
         public void actionPerformed(ActionEvent evt) {
            Color c = JColorChooser.showDialog(SimplePaint2.this,
                  "Select Drawing Color", currentColor);
            if (c != null)
               currentColor = c;
         }
      });
      
      /* Add commands to the "BackgroundColor" menu.  The menu contains commands
       * for setting the background color of the panel.  When the user chooses
       * one of these commands, the panel is immediately redrawn with the new
       * background color.  Any curves that have been drawn are still there.
       */

      bgColorMenu.add(makeBgColorMenuItem("Black", Color.BLACK));
      bgColorMenu.add(makeBgColorMenuItem("White", Color.WHITE));
      bgColorMenu.add(makeBgColorMenuItem("Red", Color.RED));
      bgColorMenu.add(makeBgColorMenuItem("Green", Color.GREEN));
      bgColorMenu.add(makeBgColorMenuItem("Blue", Color.BLUE));
      bgColorMenu.add(makeBgColorMenuItem("Cyan", Color.CYAN));
      bgColorMenu.add(makeBgColorMenuItem("Magenta", Color.MAGENTA));
      bgColorMenu.add(makeBgColorMenuItem("Yellow", Color.YELLOW));
      JMenuItem customBgColor = new JMenuItem("Custom...");
      bgColorMenu.add(customBgColor);
      customBgColor.addActionListener( new ActionListener() { 
         public void actionPerformed(ActionEvent evt) {
            Color c = JColorChooser.showDialog(SimplePaint2.this,
                  "Select Background Color", getBackground());
            if (c != null)
               setBackground(c);
         }
      });
      
      /* Return the menu bar that has been constructed. */
      
      return menuBar;

   } // end createMenuBar


   /**
    * This utility method is used to create a JMenuItem that sets the
    * current drawing color.
    * @param command  the text that will appear in the menu
    * @param color  the drawing color that is selected by this command.  (Note that
    *    this parameter is "final" for a technical reason: This is a requirement for
    *    a local variable that is used in an anonymous inner class.)
    * @return  the JMenuItem that has been created.
    */
   private JMenuItem makeBgColorMenuItem(String command, final Color color) {
      JMenuItem item = new JMenuItem(command);
      item.addActionListener( new ActionListener()  {
         public void actionPerformed(ActionEvent evt) {
            setBackground(color);
         }
      });
      return item;
   }


   /**
    * This utility method is used to create a JMenuItem that sets the
    * background color of the panel.
    * @param command  the text that will appear in the menu
    * @param color  the background color that is selected by this command.
    * @return  the JMenuItem that has been created.
    */
   private JMenuItem makeColorMenuItem(String command, final Color color) {
      JMenuItem item = new JMenuItem(command);
      item.addActionListener( new ActionListener()  {
         public void actionPerformed(ActionEvent evt) {
            currentColor = color;
         }
      });
      return item;
   }

}