import java.applet.Applet;
import java.applet.AudioClip;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;
import java.net.MalformedURLException;
import java.net.URL;

import javax.swing.ImageIcon;
import javax.swing.JPanel;

// contains the drawing of the various elements of the game, such as the
/* 
 * The Arena is where the main action happens. It is responsible for all graphics
 * and sounds, and runs the secondary thread to move the aliens, control the shots,
 * etc.
 */
public class Arena extends JPanel implements Runnable
{
	// The Thread that will act as secondary thread to control aliens and shots
	Thread thread = null;
	// (x,y) coordinates of the single 'alien'
	int xUFO = 10;
	int yUFO = 10;
	// height, width of the single 'alien'
	int wUFO = 40;
	int hUFO = 40;
	// direction of the alien ufo (1 moves left to right, -1 move right to left)
	int dirUFO = 1;
	// speed of the alien ufo, in ‘clock ticks’
	int speedUFO = 30;
	
	int xBullet;
	int yBullet;
	int speedBullet = 1;
	// speed of the thread, i.e. the alien movement by providing ‘clock ticks’
	int sleepTime = 5;
	long tick = 0L;
	
	AudioClip ufo = null;
	AudioClip fire = null;
	AudioClip die = null;
	
	ImageIcon icon1 = null;
	ImageIcon icon2 = null;
	ImageIcon icon = null;
	
	// Constructor. Is called automatically whenever a new Arena is created. Includes
	// setup instructions and other initializations (we’ll add those later).
	public Arena()
	{
        try 
        {
			ufo = Applet.newAudioClip(new URL("file:" + System.getProperty("user.dir") + "/invader.wav"));
			fire = Applet.newAudioClip(new URL("file:" + System.getProperty("user.dir") + "/shoot.wav"));
			die = Applet.newAudioClip(new URL("file:" + System.getProperty("user.dir") + "/invaderkilled.wav"));

			icon1 = new ImageIcon(new URL("file:" + System.getProperty("user.dir") + "/invader1.jpg"));
			icon2 = new ImageIcon(new URL("file:" + System.getProperty("user.dir") + "/invader2.jpg"));
			icon = icon1;
			
			yBullet = getHeight();
			xBullet = getWidth()/2;
        }
        catch (MalformedURLException e) 
        {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	
	// Starts a new thread if no thread is currently active. The thread will execute
	// the 'run' method automatically when started because of the this use.
	public void start()
	{
		if (thread == null)
		{
			thread = new Thread(this);
			thread.start();
			
			xBullet = getWidth()/2;
			yBullet = getHeight();
		}
	}
	
	// Stops the current thread from running. Can be restarted by calling 'start'
	public void stop()
	{
		thread = null;
	}
	
	// Run method controls the game by moving the alien space ships, bullets, etc.
	// Also needs to contain code checking for any hits, update the score, etc.
	public void run()
	{
		while (thread != null)
		{
			if ((tick % speedBullet) == 0)
			{
				yBullet = yBullet - 2;
			}
			
			if ((tick % speedUFO) == 0)
			{
				if (xUFO >= getWidth()-wUFO)
				{
					dirUFO = -1;
					yUFO = yUFO + hUFO;
					xUFO = getWidth() - wUFO - 1;
				}
				else if (xUFO < 0)
				{
					dirUFO = 1;
					yUFO = yUFO + hUFO;
					xUFO = 1;
				}
				
				xUFO = xUFO + dirUFO*wUFO/2;
				if (icon.getImage() == icon1.getImage())
					icon = icon2;
				else
					icon = icon1;
				
				ufo.play();
			}		
			
			detectHit();
			
			if (yUFO > getHeight())
				stop();
			
			try 
			{
				tick = tick + 1;
				thread.sleep(sleepTime);
			} 
			catch (InterruptedException e) 
			{
				e.printStackTrace();
			}
			repaint();
		}
	}
	
	public void detectHit()
	{
		if ((xBullet > xUFO) && (xBullet < xUFO + wUFO) &&
			(yBullet > yUFO) && (yBullet < yUFO + hUFO))
		{
			speedUFO = speedUFO - 5;
			die.play();
			stop();
		}
	}
	// Draws everything, using variables for their locations. If the variables
	// change, the corresponding object is drawn at its new location. Standard method
	// for all Java program containing some custom drawing.
	public void paintComponent(Graphics g)
	{
		// the following line must be the first line in this method
		super.paintComponent(g);
		
		g.drawImage(icon.getImage(), xUFO, yUFO, wUFO, wUFO, null);
		xBullet = getWidth()/2;
		
		g.setColor(Color.red);
		g.fillOval(xBullet, yBullet, 6, 6);
	}

	public void fire() 
	{
		yBullet = getHeight();
		fire.play();	
	}
}