package funpoly.visitor;

import funpoly.*;

/**
* Adds host polynomial to input polynomial.  Returns the resulting sum polynomial.
* @author Dung X. Nguyen
*/
public class AddAlgo implements IVisitor
{
	public final static AddAlgo Singleton = new AddAlgo ();

	private AddAlgo()
	{
	}
	/**
	 * @param poly a Constant polynomial
	 * @param input a APolynomial
	 * @return a APolynomial representing the sum of poly and input.
	 */
	public Object forConst(APolynomial poly, Object input)
	{
      APolynomial p = (APolynomial)input;
      int pDegree = p.getDegree();
      return
         0 == pDegree?
            PolyFactory.MakeConstPoly(poly.getLeadCoef() + p.getLeadCoef()):
            p.execute(this, poly);  // also: forNonConst (p, poly);
	}

	/**
	 * @param poly a non-constant APolynomial
	 * @param input a APolynomial
	 * @return a APolynomial representing the sum of poly and input.
	 */
	public Object forNonConst(APolynomial poly, Object input)
	{
      APolynomial p = (APolynomial)input;
      int pCoef = p.getLeadCoef();
      int pDegree = p.getDegree();
      int polyCoef = poly.getLeadCoef();
      int polyDegree = poly.getDegree();
      return
         (pDegree < polyDegree)?
            PolyFactory.MakePoly (polyCoef, polyDegree, (APolynomial)poly.getLowerPoly().execute (this, p)):
            (pDegree == polyDegree)?
               PolyFactory.MakePoly (polyCoef + pCoef, polyDegree, (APolynomial)poly.getLowerPoly().execute(this, p.getLowerPoly())):
               PolyFactory.MakePoly (pCoef, pDegree, (APolynomial)poly.execute(this, p.getLowerPoly()));
	}
}