package cn.ksource.test;

import java.awt.Color;
import java.awt.GradientPaint;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Paint;
import java.awt.Point;
import java.awt.RadialGradientPaint;
import java.awt.RenderingHints;
import java.awt.Shape;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.GeneralPath;
import java.awt.geom.Point2D;
import java.util.HashMap;
import java.util.Map;
import java.util.Random;
import java.util.Set;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
 
@SuppressWarnings("serial")
public class Star extends JPanel {
    private Map<Shape, Point> stars = new HashMap<Shape, Point>();
    private Random rand = new Random(System.currentTimeMillis());
 
    public Star() {
        this.stars.put(createStar(5, 10, 15), new Point(40, 40));
 
        this.setFocusable(true);
        this.addMouseListener(new MouseAdapter() {
            @Override
            public void mousePressed(MouseEvent e) {
                int count = 2 + rand.nextInt(15);
                double innerRadius = 5 + rand.nextInt(20);
                double outerRadius = innerRadius + 10 + rand.nextInt(30);
                GeneralPath s = createStar(count, innerRadius, outerRadius);
                stars.put(s, new Point(e.getX(), e.getY()));
                repaint();
            }
        });
 
        this.addKeyListener(new KeyAdapter() {
            @Override
            public void keyReleased(KeyEvent e) {
                if (e.getKeyCode() == KeyEvent.VK_R) {
                    stars.clear();
                    repaint();
                }
            }
        });
    }
 
    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D) g;
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
 
        // Paint a gradient for the sky
        GradientPaint background = new GradientPaint(0f, 0f, Color.GRAY.darker(), 0f, getHeight(),
            Color.GRAY.brighter());
        g2d.setPaint(background);
        g2d.fillRect(0, 0, getWidth(), 4 * getHeight() / 5);
 
        // Paint a gradient for the ground
        background = new GradientPaint(0f, 4 * getHeight() / 5, Color.BLACK, 0f, getHeight(),
            Color.GRAY.darker());
        g2d.setPaint(background);
        g2d.fillRect(0, 4 * getHeight() / 5, getWidth(), getHeight() / 5 + 4);
 
        // Using a radial gradient paint
        float[] fractions = new float[] { 0.0f, 0.40f };
        Color[] colors = new Color[] { Color.WHITE, new Color(0.0f, 0.0f, 0.0f, 0.5f) };
        Paint p = new RadialGradientPaint(0, 0, 100, fractions, colors);
        g2d.setPaint(p);
 
        // Show the stars
        Set<Map.Entry<Shape, Point>> items = stars.entrySet();
        for (Map.Entry<Shape, Point> s : items) {
            g2d.translate(s.getValue().getX(), s.getValue().getY());
            g2d.fill(s.getKey());
            g2d.translate(-s.getValue().getX(), -s.getValue().getY());
        }
    }
 
    // 创建一个星形路径
    public static GeneralPath createStar(int count, double innerRadius, double outerRadius) {
        // 因为swing中缀坐标向下，所以正上方的中点坐标是负值
        GeneralPath star = new GeneralPath();
        double extentAngle = 360.0 / count;
 
        Point2D op = new Point2D.Double(0, -outerRadius);
        Point2D ip = GeometryUtil.rotate(0, -innerRadius, extentAngle / 2);
        star.moveTo(op.getX(), op.getY());
        star.lineTo(ip.getX(), ip.getY());
 
        for (int i = 0; i < count - 1; ++i) {
            op = GeometryUtil.rotate(op.getX(), op.getY(), extentAngle);
            star.lineTo(op.getX(), op.getY());
 
            ip = GeometryUtil.rotate(ip.getX(), ip.getY(), extentAngle);
            star.lineTo(ip.getX(), ip.getY());
        }
        star.closePath();
 
        return star;
    }
 
    private static void createGuiAndShow() {
        JFrame frame = new JFrame("Star");
        frame.getContentPane().add(new Star());
 
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(550, 400);
        frame.setAlwaysOnTop(true);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
 
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                createGuiAndShow();
            }
        });
    }
}