package cse1030.drawing;

/**
 * Scale transformations cause objects to stretch or shrink in size.
 * Scale transformations are controlled by two scalar values:
 * 
 * <ol>
 * <li><code>sx</code>: the scale factor in the horizontal direction</li>
 * <li><code>sy</code>: the scale factor in the vertical direction</li>
 * </ol>
 * 
 * <p>
 * A positive value of <code>sx</code> greater than <code>1</code> causes the object
 * to stretch in the horizontal direction.
 * 
 * <p>
 * A positive value of <code>sx</code> less than <code>1</code> causes the object
 * to shrink in the horizontal direction.
 * 
 * <p>
 * A positive value of <code>sy</code> greater than <code>1</code> causes the object
 * to stretch in the vertical direction.
 * 
 * <p>
 * A positive value of <code>sy</code> less than <code>1</code> causes the object
 * to shrink in the vertical direction.
 * 
 * @author CSE1030Z
 *
 */
public class Scale extends Transformation {

  private double sx;
  private double sy;

  /**
   * Create a scale transformation that scales in the horizontal
   * and vertical directions.
   * 
   * @param name the name of the transformation
   * @param sx the scale factor in the horizontal direction
   * @param sy the scale factor in the vertical direction
   */
  public Scale(String name, double sx, double sy) {
    super(name);
    this.sx = sx;
    this.sy = sy;
  }

  /**
   * Transform a point changing its coordinates. For a scale of
   * <code>sx</code> and <code>sy</code> the
   * coordinates of the point are transformed as follows:
   * 
   * <p>
   * <code>newx = sx * x</code><br />
   * <code>newy = sy * y</code><br />
   * 
   * @see cse1030.drawing.Transformation#transform(cse1030.drawing.Point2D)
   * 
   * @param p
   *          the point to transform
   */
  @Override
  public void transform(Point2D p) {
    double x = p.getX();
    double y = p.getY();
    p.setX(this.sx * x);
    p.setY(this.sy * y);
  }

  /**
   * Apply the scale to a point to produce a new point leaving the
   * original point unchanged.
   * 
   * @see cse1030.drawing.Scale#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 scaling 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 scale. The returned string is the
   * name of the scale followed by the string <code>" : scale of factors "</code>
   * followed by <code>sx</code> followed by " and " followed by
   * <code>sy</code>. For example, a scale of factors <code>sx = 1.55</code>
   * and <code>sy = 3.008</code> named
   * <code>T1</code> has the following string representation:
   * 
   * <p>
   * <code>"T1 : scale of factors 1.55 and 3.008"</code>
   * 
   * @see cse1030.drawing.Transformation#toString()
   * 
   * @return the string representation of the shear
   */
  @Override
  public String toString() {
    return super.toString() + " : scale, sx = " + this.sx + ", sy = " + this.sy;
  }

}