/*
 * JavaEyes - a program that draws eyes that follows the mouse pointer.
 * October 2003
 *
 * @author Ben Bederson, (c) University of Maryland, Computer Science Department
 */

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

/**
 * The main class that represents the JavaEyes program.
 */
public class JavaEyes extends JPanel {
	// Constants to control look of eyes
	static final int EYE_RADIUS = 40;               // The radius of the eye (in pixels)
	static final int EYE_SPACE = 20;                // The space between the two eyes (in pixels)
	static final int PUPIL_RADIUS = 10;             // The radius of the pupil (in pixels)
	static final Color PUPIL_COLOR = Color.red;   // The color of the pupil

	// Constants to control physics of interaction
	static final int ATTRACTION = 1;
	static final int REPULSION = 2;

	// Variables representing current state of eyes
	int physics = ATTRACTION;       // What kind of physics to use
	int eyeRadius = EYE_RADIUS;		// Current radii of eyes
	int eyeSpace = EYE_SPACE;		// Current space between eyes
	int pupilRadius = PUPIL_RADIUS; // Current radii of pupils
	Color pupilColor = PUPIL_COLOR; // Current color of pupils;
	int leftEyeX, leftEyeY;         // Left eye upper-left corner
    int rightEyeX, rightEyeY;       // Right eye upper-left corner
	int leftPupilX, leftPupilY;     // Left pupil upper-left corner
	int rightPupilX, rightPupilY;   // Right pupil upper-left corner
	int pointerX, pointerY;			// Most recent position of pointer
	
	public JavaEyes() {
		setBackground(Color.white);
		addMouseMotionListener(new EyeListener(this));          // Register for changes in mouse position
		addComponentListener(new EyeComponentListener(this));   // Register for changes in window geometry

		// Create a top-level window to put the eyes in
		JFrame frame = new JFrame("Java Eyes");
		frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
		frame.setBounds(100, 100, 400, 300);
		frame.setContentPane(this);
		frame.show();
	}
	
	public void setPhysics(int newPhysics) {
		if ((newPhysics == ATTRACTION) || (newPhysics == REPULSION)) {
			physics = newPhysics;
			computeEyePositions();
			repaint();
		}
	}
	
	public void setEyeRadius(int newEyeRadius) {
		if (newEyeRadius > 0) {
			eyeRadius = newEyeRadius;
			computeEyePositions();
			repaint();
		}
	}
	
	public void setEyeSpace(int newEyeSpace) {
		if (newEyeSpace > 0) {
			eyeSpace = newEyeSpace;
			computeEyePositions();
			repaint();
		}
	}
	
	public void setPupilRadius(int newPupilRadius) {
		if (newPupilRadius > 0) {
			pupilRadius = newPupilRadius;
			computeEyePositions();
			repaint();
		}
	}
	
	public void setPupilColor(Color newPupilColor) {
		pupilColor = newPupilColor;
		repaint();
	}
	
	/**
	 * This should be called whenever the pointer is moved.
	 * It causes the pupil position to be recomputed, and 
	 * triggers repainting of the eyes.
	 * 
	 * @param pointerX The X position of the mouse pointer
	 * @param pointerY The Y position of the mouse pointer
	 */
	public void setPointerPosition(int newPointerX, int newPointerY) {
		pointerX = newPointerX;
		pointerY = newPointerY;
		computeEyePositions();
		repaint();
	}
	
	/**
	 * Paints the eyes (and pupils) on the screen using values
	 * that have been precomputed.
	 */
	public void paintComponent(Graphics g) {		
		super.paintComponent(g);
		
		g.setColor(Color.black);
		g.drawArc(leftEyeX, leftEyeY, eyeRadius * 2, eyeRadius * 2, 0, 360);
		g.drawArc(rightEyeX, rightEyeY, eyeRadius * 2, eyeRadius * 2, 0, 360);
		
		g.setColor(pupilColor);
		g.fillArc(leftPupilX, leftPupilY, pupilRadius * 2, pupilRadius * 2, 0, 360);
		g.fillArc(rightPupilX, rightPupilY, pupilRadius * 2, pupilRadius * 2, 0, 360);
	}

	/**
	 * This is the math part that computes the position of the eyes and the pupils
	 * based on the dimensions of the window, and the position of the pointer.
	 */
	void computeEyePositions() {
		// First compute the center of the eyes based on the window size
		int leftEyeCtrX = (getWidth() / 2) - eyeRadius - (eyeSpace / 2);
		int rightEyeCtrX = (getWidth() / 2) + eyeRadius + (eyeSpace / 2);
		int eyeCtrY = getHeight() / 2;
		
		// Then based on the center, compute the left and right sides of each eye
		leftEyeX = leftEyeCtrX - eyeRadius;
		leftEyeY = eyeCtrY - eyeRadius;
		rightEyeX = rightEyeCtrX - eyeRadius;
		rightEyeY = eyeCtrY - eyeRadius;
		
		// Now the tricky part - compute the position of the left pupil
		// This is calculated by using similar triangles based on the
		// center of the eye and the pointer position.
		int pupilDist = (int)(eyeRadius - (pupilRadius * 1.5));
		if (physics == REPULSION) {
			pupilDist *= -1;
		}
		int pointerDist = (int)Math.sqrt((pointerX - leftEyeCtrX)*(pointerX - leftEyeCtrX) + 
		                                 (pointerY - eyeCtrY)*(pointerY - eyeCtrY));
		if (pointerDist > 5) {
			leftPupilX = (int)(leftEyeCtrX + pupilDist * (pointerX - leftEyeCtrX) / pointerDist) - pupilRadius;
			leftPupilY = (int)(eyeCtrY + pupilDist * (pointerY - eyeCtrY) / pointerDist) - pupilRadius;
		}

		// And finally compute the position of the right pupil
		pointerDist = (int)Math.sqrt((pointerX - rightEyeCtrX)*(pointerX - rightEyeCtrX) + 
		                             (pointerY - eyeCtrY)*(pointerY - eyeCtrY));
		if (pointerDist > 5) {
			rightPupilX = (int)(rightEyeCtrX + pupilDist * (pointerX - rightEyeCtrX) / pointerDist) - pupilRadius;
			rightPupilY = (int)(eyeCtrY + pupilDist * (pointerY - eyeCtrY) / pointerDist) - pupilRadius;
		}
	}
	
	public static void main(String[] args) {
		new JavaEyes();
	}
}

/**
 * This is a utility class that reports mouse motion back to the eyes.
 */
class EyeListener extends MouseMotionAdapter {
	JavaEyes eyes;   // Store a reference back to the actual eyes
	
	public EyeListener(JavaEyes e) {
		eyes = e;
	}
	
	/**
	 * Gets notified whenever the mouse moves, and reports changes back to the eyes.
	 */
	public void mouseMoved(MouseEvent e) {
		eyes.setPointerPosition(e.getX(), e.getY());
	}
}

class EyeComponentListener extends ComponentAdapter {
	JavaEyes eyes;   // Store a reference back to the actual eyes
	
	public EyeComponentListener(JavaEyes e) {
		eyes = e;
	}
	
	/**
	 * Gets notified whenever the mouse moves, and reports changes back to the eyes.
	 */
	public void componentResized(ComponentEvent e) {
		eyes.computeEyePositions();
	}	
}