package poly.visitor;

import poly.*;

public class ToString implements IVisitor
{
   // singleton pattern
   public static ToString Singleton = new ToString ( );

   /**
    * Private Constructor for singleton pattern
    */
   private ToString ( )
   {
   }

   /**
    * Called with constant polynomials.  The coefficient
    * could be anything including zero.  Just return the
    * string value of the coefficient.
    *
    * @param poly the constant polynomial to print as a string
    *
    * @param input ignored parameter
    *
    * @return the string representing this polynomial
    */
   public Object forConst ( ConstPoly poly, Object input )
   {
      return Double.toString ( poly.getLeadCoef ( ) );
   }

   /**
    * Called with non-constant polynomials.  The coefficient
    * could be anything except zero.  Return
    * coefficient x^ exponent and toStringHelp of rest
    *
    * @param poly the non-constant polynomial to print as a string
    *
    * @param input ignored parameter
    *
    * @return the string representing this polynomial
    */
   public Object forNonConst ( NonConstPoly poly, Object input )
   {
      return ( poly.getLeadCoef ( ) + "x^" + poly.getDegree ( ) +
               poly.getLowerPoly ( ).execute ( ToStringHelper.Singleton, null ) );
   }
}

class ToStringHelper implements IVisitor
{
   // singleton pattern
   public static ToStringHelper Singleton = new ToStringHelper ( );

   /**
    * Private Constructor for singleton pattern
    */
   private ToStringHelper ( )
   {
   }

   /**
    * Called with constant polynomials.  The coefficient
    * could be anything including zero.  Check to see if it's
    * zero.  If so, don't print anything.  Otherwise, print
    * "+ coefficient"
    *
    * @param poly the constant polynomial to print as a string
    *
    * @param input ignored parameter
    *
    * @return the string representing this polynomial
    */
   public Object forConst ( ConstPoly poly, Object input )
   {
      double coef = poly.getLeadCoef ( );

      if ( coef == 0.0 )
      {
         return "";
      }
      else if ( coef < 0 )
      {
         return  ( " - " + -coef );
      }
      else
      {
         return ( " + " + coef );
      }
   }

   /**
    * Called with non-constant polynomials.  The coefficient
    * could be anything except zero.  Return
    * "+ coefficient x^ exponent" and toStringHelp of rest
    *
    * @param poly the non-constant polynomial to print as a string
    *
    * @param input ignored parameter
    *
    * @return the string representing this polynomial
    */
   public Object forNonConst ( NonConstPoly poly, Object input )
   {
      double coef = poly.getLeadCoef ( );
      String lowerString =  "x^" + poly.getDegree ( ) +  poly.getLowerPoly ( ).execute ( this, null );
      return coef < 0?
               " - " + -coef  + lowerString:
               " + " + coef + lowerString;
   }
}