package rebelsky.vec;

/**
 * A vector in two space, implemented by (x,y) pair.
 *
 * @author CSC152 2004F
 * @version 0.5 of September 2004
 */
public class Point
	extends Vec2D
{

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

	/** The x coordinate. */
	double x;

	/** The y coordinate. */
	double y;


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

	/**
	 * Construct the point (_x,_y).
	 */
	public Point(double _x, double _y)
	{
		this.x = _x;
		this.y = _y;
	} // Point(double, double)


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

	/**
	 * Get the X coordinate of this vector.
	 */
	public double getX() 
	{
		return this.x;
	} // getX()
	
	/**
	 * Get the Y coordinate of this vector.
	 */
	public double getY()
	{
		return this.y;
	} // getY()
	
	/**
	 * Get the angle of this vector from the origin.
	 */
	public double getAngle()
	{
		// Special case: 0 for (0.0,0.0)
		if (Math.abs(this.x) + Math.abs(this.y) < 0.00001)
			return 0.0;
		return Math.asin(this.y/this.getRadius());
	} // getAngle()

	/**
	 * Get the radius of this vector.
	 */
	public double getRadius()
	{
		return Math.sqrt(this.x*this.x + this.y*this.y);
	} // getRadius()

	/**
	 * Rotate this vector for some amount around the origin.
	 */
	public Vec2D rotate(double angle)
	{
		// New x: xcosangle - ysinangle, xsinangle + ycosangle
		return new Point(this.x*Math.cos(angle) - this.y*Math.sin(angle), 
		                 this.x*Math.sin(angle) + this.y*Math.cos(angle));
	} // rotate(double)

	/**
	 * Increase the length of this vector by a factor of factor.
	 */
	public Vec2D stretch(double factor)
	{
		return new Point(factor*this.x, factor*this.y);
	} // stretch(double)
	
	/**
	 * Compute the unit vector for this vector (radius 1, same
	 * angle).
	 */
	public Vec2D unitVector() 
	{
		double theta = this.getAngle();
		return new Point(Math.cos(theta), Math.sin(theta));
	} // stretch(double)
	
	/**
	 * Convert this vector to a string.
	 */
	public String toString() 
	{
		return "(x:" + this.x + ",y:" + this.y + ")";
	} // toString()

} // interface Vec2D