package com.codebynumber.java3d.breakout;

import javax.media.j3d.Appearance;
import javax.media.j3d.Material;
import javax.media.j3d.Transform3D;
import javax.media.j3d.TransformGroup;
import javax.vecmath.Vector3d;

import com.sun.j3d.utils.geometry.Sphere;

/**
 * Transform group that contains the ball for Breakout. Methods update() and 
 * hitsomething() get called by TimeBehavior and Collision respectively. These
 * methods affect the translation position and direction of the TransformGroup for
 * the ball sphere.
 * @author codebynumber.com
 *
 */
public class Ball extends TransformGroup {
	/** Ball radius is 20 cm. */
	public static final float BALL_RADIUS = 0.2f;
	/** Move at 2.0 m/s. */
	private static final double moveRate = 2.0 / 1000;
	/** Place the ball 1.0 units into the scene to begin with */
	private Vector3d startingPosition = new Vector3d(0.0, 0.0, -1.1);
	/** Send it into the scene to the right to begin with */
	private Vector3d direction = new Vector3d(1.0, 0.0, -1.0);
	private Sphere ball;
	/** Last timestamp that an update was made, used in movement code. */
	private long lastUpdate;
	private Transform3D t3d;

	/**
	 * Create ball and add it to transform group, ready to place in scene.
	 */
	public Ball() {
		super();
		setCapability(TransformGroup.ALLOW_TRANSFORM_READ);
		setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);
		createBall();
	}

	/**
	 * Initializes ball and Transform3D for location.
	 */
	private void createBall() {
		t3d = new Transform3D();
		ball = new Sphere(BALL_RADIUS);
		Appearance app = new Appearance();

		Material greenMat = new Material(Breakout.green, Breakout.black, Breakout.green, Breakout.white, 65.0f);
		greenMat.setLightingEnable(true);
		app.setMaterial(greenMat);
		ball.setAppearance(app);

		//Grab the system time for movement
		lastUpdate = System.currentTimeMillis();

		t3d.setTranslation(startingPosition);
		TransformGroup tg = new TransformGroup(t3d);
		tg.addChild(ball);

		addChild(tg);
	}

	/**
	 * Move ball according to moveRate * elapsed frames
	 */
	public void update() {
		long currUpdate = System.currentTimeMillis();
		Transform3D newMove = new Transform3D();

		//Determine how much the ball should move in elapsed time
		double z = moveRate * (currUpdate-lastUpdate);
		if (direction.z < 0) {
			z = -z;
		}
		double x = 0.0;
		if (direction.x != 0.0) {
			x = moveRate * (currUpdate-lastUpdate);
			if (direction.x < 0) {
				x = -x;
			}
		}

		//Add amount to this.Transform3D
		getTransform(t3d);
		newMove.setTranslation(new Vector3d(x, 0.0, z));
		t3d.mul(newMove);
		setTransform(t3d);
		lastUpdate = currUpdate;
	}

	/**
	 * Change direction according to changeVect. Called after a collision.
	 * @param changeVect multiplier for direction (-1 to change)
	 */
	public void hitSomething(Vector3d changeVect) {
		direction.x = changeVect.x * direction.x;
		direction.y = changeVect.y * direction.y;
		direction.z = changeVect.z * direction.z;
	}
}