import java.awt.*;     // Needed for window and graphics (explained in COMP1406)
import javax.swing.*;  // Needed for window and graphics (explained in COMP1406)

// This application simulates birds flying in a window
public class BirdSimulation {
    // This variable stores the panel that displays the birds
    // (This is a topic discussed in COMP1406 course)
    public static BirdPanel   birdPanel;
    public static Bird[]      birds;      // an array to hold the birds

    public static void startSimulation() {
        while(true) {
            for (int i=0; i<birds.length; i++) 
                move(birds[i]);
            birdPanel.repaint();
            try{ Thread.sleep(60); } catch(Exception e){};
        }
    }

    // Code for moving a bird forwards
    public static void move(Bird b) {
        // Move the bird 10 pixels forward
        b.x = b.x + b.speed; 
  
        if (b.x > BirdPanel.WIDTH)
            b.x = -102; // 102 is the width of the Bird image

        b.currentFrame = (b.currentFrame + 1) % 8;
    }

    // Create a window, add birds, then start simulating
    public static void main(String args[]) {
        // Make some birds
        birds = new Bird[2500];      // an array to hold the birds
        for (int i=0; i<birds.length; i++) {
            birds[i] = new Bird((float)(Math.random()*BirdPanel.WIDTH), 
                                (float)(Math.random()*BirdPanel.HEIGHT/2));
        }
        
        JFrame frame = new JFrame("Bird Simulation");
        frame.add(birdPanel = new BirdPanel(birds));
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack(); // Makes size according to panel's preference
        frame.setVisible(true);
        
        startSimulation();
    }
}