/*
 * Ball.java
 *
 * License: The code is released under Creative Commons Attribution 2.5 License
 * (http://creativecommons.org/licenses/by/2.5/)
 */

import java.awt.Insets;

/**
 *
 * @author rbair
 */
public class Ball {
    private Model model = new Model();
    protected double _x = 0;
    protected double _y = 0;
    protected double _vx = 0;
    protected double _vy = 0;
    protected double _r = 0;
    protected double _d = 0;
    protected double _d2 = 0;
    
    public Ball() {
        //default provisioning
        // default provisioning
        this._x = (model.walls.right - model.walls.left - 2*model.ballRadius)*Math.random();
        this._y = (model.walls.bottom - model.walls.top - 2*model.ballRadius)*Math.random();
        this._vx = 2*model.maxSpeed*Math.random() - model.maxSpeed;
        this._vy = 2*model.maxSpeed*Math.random() - model.maxSpeed;
        this._r = model.ballRadius; // d = 52 px
        this._d = 2*this._r;
        this._d2 = this._d*this._d;
    }
    
    public void move() {
        this._x += this._vx;
        this._y += this._vy;
        // walls collisons
        
        // left
        if (this._x < model.walls.left && this._vx<0) {
            //this._vx += (this._x - walls.left)*elastity;
            this._vx = -this._vx;
        }
        // top
        if (this._y < model.walls.top && this._vy<0) {
            //this._vy += (this._y - walls.top)*elastity;
            this._vy = -this._vy;
        }
        // right
        if (this._x > model.walls.right - this._d && this._vx>0) {
            //this._vx += (this._x - walls.right + this._d)*elastity;
            this._vx = -this._vx;
        }
        // bottom
        if (this._y > model.walls.bottom - this._d && this._vy>0) {
            //this._vy += (this._y - walls.bottom + this._d)*elastity;
            this._vy = -this._vy;
        }
    }
    
    public boolean doCollide(Ball b) {
        // calculate some vectors
        double dx = this._x - b._x;
        double dy = this._y - b._y;
        double dvx = this._vx - b._vx;
        double dvy = this._vy - b._vy;
        double distance2 = dx*dx + dy*dy;
        
        if (Math.abs(dx) > this._d || Math.abs(dy) > this._d)
            return false;
        if (distance2 > this._d2)
            return false;
        
        // make absolutely elastic collision
        double mag = dvx*dx + dvy*dy;
        
        // test that balls move towards each other
        if (mag > 0)
            return false;
        
        mag /= distance2;
        
        double delta_vx = dx*mag;
        double delta_vy = dy*mag;
        
        this._vx -= delta_vx;
        this._vy -= delta_vy;
        
        b._vx += delta_vx;
        b._vy += delta_vy;
        
        return true;
    }
    
    private static final class Model {
        private Insets walls = new Insets(0, 0, 300, 500);
        private double elastity = -.02;
        private double ballRadius = 26;
        private double maxSpeed = 3.0;
    }
}