package cse1030.drawing;

/**
 * A class that rotates points about the origin. The amount of rotation is
 * controlled by a scalar parameter called the rotation angle. A positive
 * rotation angle causes points to rotate counterclockwise about the origin.
 * 
 * @author CSE1030Z
 * 
 */
public class Rotation extends Transformation {

  private double angle;

  /**
   * Construct a rotation transformation given its name and the angle
   * of rotation in radians.
   * 
   * @param name the name of the transformation
   * @param radians the rotation angle in radians
   */
  public Rotation(String name, double radians) {
    super(name);
    this.angle = radians;
  }

  /**
   * Transform a point changing its coordinates. For a rotation of
   * <code>theta</code> radians the <code>x</code> and <code>y</code>
   * coordinates of the point are transformed as follows:
   * 
   * <p>
   * <code>newx = cos(theta) * x - sin(theta) * y</code><br />
   * <code>newy = sin(theta) * x + cos(theta) * y</code><br />
   * 
   * @see cse1030.drawing.Transformation#transform(cse1030.drawing.Point2D)
   * 
   * @param p
   *          the point to transform
   */
  @Override
  public void transform(Point2D p) {
    double c = Math.cos(this.angle);
    double s = Math.sin(this.angle);
    double x = p.getX();
    double y = p.getY();
    p.setX(c * x - s * y);
    p.setY(s * x + c * y);
  }

  /**
   * Apply the rotation to a point to produce a new point leaving the
   * original point unchanged.
   * 
   * @see cse1030.drawing.Rotation#transform(cse1030.drawing.Point2D)
   * 
   * @see cse1030.drawing.Transformation#apply(cse1030.drawing.Point2D)
   * 
   * @param p the point to apply the transformation to
   * @return a new point equal to rotating the input point <code>p</code>
   */
  @Override
  public Point2D apply(Point2D p) {
    Point2D q = new Point2D(p);
    this.transform(q);
    return q;
  }

  /**
   * Get a string representation of the rotation. The returned string is the
   * name of the rotation followed by the string <code>" : rotation of "</code>
   * followed by the angle in radians followed by the string
   * <code>" radians"</code>. For example, a rotation of 90 degrees named
   * <code>T1</code> has the following string representation:
   * 
   * <p>
   * <code>"T1 : rotation of 1.5707963267948966 radians"</code>
   * 
   * @see cse1030.drawing.Transformation#toString()
   * 
   * @return the string representation of the rotation
   */
  @Override
  public String toString() {
    return super.toString() + " : rotation of " + this.angle + " radians";
  }

}