import java.awt.AWTEvent;
import java.awt.Color;
import java.awt.Component;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.MouseInfo;
import java.awt.Point;
import java.awt.PointerInfo;
import java.awt.RenderingHints;
import java.awt.event.ComponentEvent;
import javax.swing.JComponent;

public class EyeComponent extends JComponent {
    private int width;
    private int height;
    private int eyeWidth;
    private int eyeHeight;

    private int EYE_RATIO = 5;
    private int MIN_SIZE = 1;
    private int MAX_SIZE = 50;

    public EyeComponent() {
        enableEvents(AWTEvent.COMPONENT_EVENT_MASK);
    }

    protected void processComponentEvent(ComponentEvent event) {
        if (event.getID() == ComponentEvent.COMPONENT_RESIZED) {
            Component comp = event.getComponent();
            width = comp.getWidth();
            height = comp.getHeight();

            eyeWidth = width/EYE_RATIO;
            if (eyeWidth < MIN_SIZE) {
                eyeWidth = MIN_SIZE;
            } else if (eyeWidth > MAX_SIZE) {
                eyeWidth = MAX_SIZE;
            }

            eyeHeight = height/EYE_RATIO;
            if (eyeHeight < MIN_SIZE) {
                eyeHeight = MIN_SIZE;
            } else if (eyeHeight > MAX_SIZE) {
                eyeHeight = MAX_SIZE;
            }
        }

        super.processComponentEvent(event);
    }

    public void paintComponent(Graphics g) {
        Graphics2D g2d = (Graphics2D)g;
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

        PointerInfo pointerInfo = MouseInfo.getPointerInfo();
        Point absolute = pointerInfo.getLocation();

        Point relative = traslatePointRelativeToComponent(absolute);

        int x;
        if (relative.x < 0) {
            x = 0;
        } else if (relative.x > width - eyeWidth) {
            x = width - eyeWidth;
        } else {
            x = relative.x;
        }

        int y;
        if (relative.y < 0) {
            y = 0;
        } else if (relative.y > height - eyeHeight) {
            y = height - eyeHeight;
        } else {
            y = relative.y;
        }

        g.setColor(Color.BLACK);
        g.fillOval(x, y, eyeWidth, eyeHeight);
    }

    private Point traslatePointRelativeToComponent(Point absolute) {
        Point compCoords = getLocationOnScreen();
        return new Point(absolute.x - compCoords.x,
                         absolute.y - compCoords.y);
    }
}