/****************************************************************************
** COPYRIGHT (C):    1997 Cay S. Horstmann. All Rights Reserved.
** PROJECT:          Practical OO Development with C++ and Java
** FILE:             Ellipse.java
** PURPOSE:          shape class
** VERSION           1.0
** PROGRAMMERS:      Cay Horstmann (CSH)
** RELEASE DATE:     3-15-97 (CSH)
** UPDATE HISTORY:
****************************************************************************/

package practicaloo;

import java.awt.Graphics;
import java.io.PrintStream;

public class Ellipse
{   public Ellipse(Point c, int a, int b)
    {   _center = c;
        _xradius = a;
        _yradius = b;
    }

    public void scale(Point center, double s)
    {   _center.scale(center, s);
        _xradius = (int)(_xradius * s);
        _yradius = (int)(_yradius * s);
    }

    public void move(int x, int y)
    {   _center.move(x, y);
    }

    public void plot(Graphics g)
    {   g.drawOval(_center.get_x() - _xradius, _center.get_y() - _yradius,
            2 * _xradius, 2 * _yradius);
    }

    public void print(PrintStream p)
    {   p.print(System.out);
    }

    public Point center()
    {   return _center;
    }

    public int xradius()
    {   return _xradius;
    }

    public int yradius()
    {   return _yradius;
    }

    public boolean is_inside(Point p)
    {   double x = (p.get_x() - _center.get_x()) / (double)_xradius;
        double y = (p.get_y() - _center.get_y()) / (double)_yradius;
        return Approx.lessOrEqual(x * x + y * y, 1.0);
    }

    public Point boundary_point(Point p)
    /*  PURPOSE:    Compute a point on the boundary of the shape
        RECEIVES:   p - a point distinct from the center
        RETURNS:    the intersection of the line joining the center and p with
               the boundary
    */
    {   double a = _center.angle(p);
        Point r = (Point)_center.clone();
        r.move((int)(_xradius * Math.cos(a)), (int)(_yradius * Math.sin(a)));
        return r;
    }

    private Point _center;
    private int _xradius;
    private int _yradius;
}