package rebelsky.vec;

/**
 * A vector in two space, implemented using Polar coordinates.
 *
 * @author CSC152 2004F
 * @version 1.0
 */
public class Polar
	extends Vec2D
{

// +--------+-------------------------------------------------------
// | Fields |
// +--------+

	/**
	 * The angle between the vector and the y=0 line.
	 */
	double theta;

	/**
	 * The distance from the point to the origin.
	 */
	double radius;


// +--------------+-------------------------------------------------
// | Constructors |
// +--------------+

	/**
	 * Build a new vector to (x,y).
	 */
	public Polar(double _radius, double _theta)
	{
		this.radius = _radius;
		this.theta = _theta;
	} // Polar(double,double)


// +-----------+----------------------------------------------------
// | Observers |
// +-----------+

	/**
	 * Get the X coordinate of this vector.
	 */
	public double getX()
	{
		return Math.cos(this.theta)*this.radius;
	} // getX()
	
	/**
	 * Get the Y coordinate of this vector.
	 */
	public double getY() 
	{
		return Math.sin(this.theta)*this.radius;
	} // getY()
	
	/**
	 * Get the angle of this vector from the origin.
	 */
	public double getAngle()
	{
		return this.theta;
	} // getAngle()

	/**
	 * Get the radius of this vector.
	 */
	public double getRadius()
	{
		return this.radius;
	} // getRadius()
	
	/**
	 * Rotate this vector for some amount around the origin.
	 */
	public Vec2D rotate(double angle)
	{
		double newtheta = this.theta + angle;
		if (newtheta > 2*Math.PI)
			newtheta = newtheta - 2*Math.PI;
		if (newtheta < 0)
			newtheta = newtheta + 2*Math.PI;
		return new Polar(this.radius, newtheta);
	} // rotate(double)
	
	/**
	 * Stretch this vector by some amount.
	 */
	public Vec2D stretch(double factor)
	{
		return new Polar(this.radius * factor, this.theta);
	} // stretch(double)

	/**
	 * Compute the unit vector for this vector (radius 1, same
	 * angle).
	 */
	public Vec2D unitVector()
	{
		return new Polar(1.0, this.theta);
	} // unitVector()
	
	/**
	 * Convert this vector to a string.
	 */
	public String toString()
	{
		return "<theta: " + this.theta + ",radius:" + this.radius + ">";
	} // toString()

} // class Polar