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

public class Paint
{
	private static PaintPanel p;				// actual drawing area, using mouse (MouseListener)
	private static GuiPanel gp;					// for GUI selections (JRadioButtons, JButtons)
	
	public static void main(String[] args)
	{
		JFrame f=new JFrame();
		f.setSize(800,800);
		f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		JPanel p1=new JPanel(new BorderLayout());		// add the two panels (p and gp) to a panel to insert
		p=new PaintPanel();								// into this JFrame
		gp=new GuiPanel();
		p1.add(p,BorderLayout.CENTER);
		p1.add(gp,BorderLayout.EAST);
		f.add(p1);
		f.setVisible(true);
	}
	
	// the following class implements one of the two JPanels.  In this case, it will be our GUI control panel
	// using JButtons for clearing the screen, undoing the last action, and quitting, and JRadioButtons to
	// select the Color and shape of object to draw
	
	private static class GuiPanel extends JPanel implements ActionListener
	{
		private JButton clear,undo,quit;					// these JButtons and JRadioButtons are our GUI controls
		private JRadioButton red, green, blue, black;
		private JRadioButton line, oval, rect;
		
		public GuiPanel()								// constructor sets up the ActionListener for the JButtons
		{												// only, instantiates all of these objects and inserts them
			clear=new JButton("clear");					// into JPanels for a decent appearance
			undo=new JButton("undo");
			quit=new JButton("quit");
			clear.addActionListener(this);
			undo.addActionListener(this);
			quit.addActionListener(this);
			red=new JRadioButton("red");				// JRadioButtons will not have their own listeners, we
			blue=new JRadioButton("blue");				// will test to see what is selected whenever the mouse
			green=new JRadioButton("green");			// is used to draw a new shape
			black=new JRadioButton("black");
			line=new JRadioButton("line");
			oval=new JRadioButton("oval");
			rect=new JRadioButton("rectangle");
			ButtonGroup b1=new ButtonGroup();			// b1 for the 4 color JRadioButtons
			b1.add(red);
			b1.add(green);
			b1.add(blue);
			b1.add(black);
			ButtonGroup b2=new ButtonGroup();			// b2 for the 3 shape JRadioButtons
			b2.add(line);
			b2.add(rect);
			b2.add(oval);
			JPanel p1=new JPanel(new GridLayout(3,1));	// the 3 JButtons in one JPanel
			p1.add(clear);
			p1.add(undo);
			p1.add(quit);
			JPanel p2=new JPanel(new GridLayout(4,1));	// the 4 color JRadioButtons in one JPanel
			p2.add(red);
			p2.add(green);
			p2.add(blue);
			p2.add(black);
			JPanel p3=new JPanel(new GridLayout(3,1));	// the 3 shape JRadioButtons in one JPanel
			p3.add(line);
			p3.add(oval);
			p3.add(rect);
			JPanel p4=new JPanel(new BorderLayout());	// coordinate the 3 JPanels into 1 JPanel going across
			p4.add(p1,BorderLayout.WEST);
			p4.add(p2,BorderLayout.CENTER);
			p4.add(p3,BorderLayout.EAST);
			add(p4);			
		}
		
		public void actionPerformed(ActionEvent e)		// when a JButton is clicked...
		{
			if(e.getSource()==quit) System.exit(0);		// on quit, exit the program
			else if(e.getSource()==clear) 				// on clear, call JPanel p's clear method
				p.clear();
			else if(e.getSource()==undo) 				// on undo, call JPanel p's undo method
				p.undo();
		}
		
		public Color getColor()						// we get called here from p when the user has released the mouse
		{											// to draw a new shape, p needs to get access to the selected Color
			if(red.isSelected()) return Color.red;		// return the Color of the JRadioButton selected
			else if(green.isSelected()) return Color.green;
			else if(blue.isSelected()) return Color.blue;
			else return Color.black;
		}		
			
		public int getType()			// we get called here from p when the user has released the mouse to draw a new
		{								// shape, p needs to get access to the type of shape as selected by the shape JRadioButtons
			if(line.isSelected()) return 0;
			else if(oval.isSelected()) return 1;
			else return 2;
		}
	}

	// this JPanel will be used for drawing (through Graphics/paintComponent) and implement MouseListener so that
	// the user can control drawing through the mouse
	
	private static class PaintPanel extends JPanel implements MouseListener
	{
		private class MyShape		// nested inner class to define a shape to be drawn, we limit this to just
		{							// lines, ovals and rectangles.  If we wanted to also allow Strings we would have
			private int x1,x2,y1,y2;	// to overload the constructor to allow for one with x, y, String and add
			private Color c;			// a JTextField to the GUI.  This makes the program somewhat more complicated
			private int type;	// all Shapes have an x1,y1 coordinate, a color and a type, also x2,y2 is used to indicate
			public MyShape(int x1, int y1, int x2, int y2, Color c, int type)	// where the line is drawn to, or how big the
			{																	// bounding box should be 
				this.x1=x1;			// initialize all of this shape's attributes
				this.x2=x2;
				this.y1=y1;
				this.y2=y2;
				this.c=c;
				this.type=type;
			}
			
			public void draw(Graphics g)		// tell this shape to draw itself on g
			{
				g.setColor(c);					
				int mx,my;
				mx=Math.min(x1,x2);				// mx, my is used in case the user has moved the mouse up or left giving
				my=Math.min(y1,y2);				// y2 or x2 values < y1 or x1 or both, needed for ovals and rectangles
				if(type==0) g.drawLine(x1,y1,x2,y2);
				else if(type==1) g.fillOval(mx,my,Math.abs(x1-x2),Math.abs(y1-y2));	// use abs to ensure that the size is not negative
				else if(type==2) g.fillRect(mx,my,Math.abs(x1-x2),Math.abs(y1-y2));				
			}
		}
		
		// here is the body of the PaintPanel class
		// our instance data
		private MyShape[] s;		// the shapes we will have drawn 
		private int num;			// the number of shapes currently to draw
		private int x1,x2,y1,y2;	// the mouse coordinates for when we press the mouse button or release it

		public PaintPanel()		// PaintPanel's constructor just initializes instance data and adds a mouse listener
		{
			s=new MyShape[1000];	// we'll assume no more than 1000 shapes will be drawn
			num=0;
			x1=x2=y1=y2=-1;			// initialize these to -1 just to have a value for them
			addMouseListener(this);
		}
		
		public void clear()			// this is called from the GuiPanel class gp when the Clear JButton is clicked
		{	
			num=0;					// to clear, reset num to 0 so that our for loop does not iterate through the
			repaint();				// s array to draw anything, and then call the paintComponent method
		}
		
		public void undo()			// this is called from the GuiPanel class gp when the Undo JButton is clicked
		{
			if(num>0)				// make sure num isn't already 0 or we can wind up with a negative number for num leading
			{						// to an exception
				num--;				// we decrement num to indicate that the for loop in paintComponent should not draw the
				repaint();			// most recently added shape
			}
		}
		
		public void mousePressed(MouseEvent e) 	// when mouse button is pressed, record its x,y coordinate in x1,y1
		{
			x1=e.getX();
			y1=e.getY();
		}
		public void mouseReleased(MouseEvent e) // when released, record its x,y coordinate in x2,y2 and get the
		{										// JRadioButton information from the GuiPanel (gp) to create a new MyShape
			Color c=gp.getColor();
			int type=gp.getType();
			x2=e.getX();
			y2=e.getY();
			s[num]=new MyShape(x1,y1,x2,y2,c,type);	// the new MyShape is added to s at position num and we then increment
			num++;									// num to indicate another shape has been added
			repaint();					// now redraw all of the shapes
		}
		public void mouseClicked(MouseEvent e) {}		// don't need to implement these
		public void mouseEntered(MouseEvent e) {}
		public void mouseExited(MouseEvent e) {}
		
		public void paintComponent(Graphics g)
		{
			super.paintComponent(g);			// blank the Graphics area
			for(int i=0;i<num;i++)				// draw each shape
					s[i].draw(g);
		}
	}
}