/**
 * @file   bspline.hpp
 * @author Julian Iseringhausen <isering@ins.uni-bonn.de>
 * @date   Mon Nov 21 13:27:22 2011
 *
 * @brief  B-Splines for molecular dynamics.
 *
 */

#ifndef BSPLINE_HPP_
#define BSPLINE_HPP_

#include "base/helper.hpp"
#include "base/polynomial.hpp"
#include "base/vector.hpp"

namespace VMG
{

class BSpline
{
public:
  BSpline(const vmg_float& width);

  vmg_float EvaluateSpline(const vmg_float& val)
  {
    for (unsigned int i=0; i<intervals.size(); ++i)
      if (val < intervals[i])
	return spline_nom[i](val) / spline_denom[i](val);
    return 0.0;
  }

  vmg_float EvaluatePotential(const vmg_float& val)
  {
    for (unsigned int i=0; i<intervals.size(); ++i)
      if (val < intervals[i])
	return potential_nom[i](val) / potential_denom[i](val);
    return potential_nom.back()(val) / potential_denom.back()(val);
  }

  vmg_float EvaluateDerivative(const Vector& v, const int& dv);

  const vmg_float& GetAntiDerivativeZero() const
  {
    return antid;
  }

private:
  std::vector<Polynomial> spline_nom, spline_denom;
  std::vector<Polynomial> potential_nom, potential_denom;
  vmg_float antid;
  std::vector<vmg_float> intervals;

  vmg_float R;
};

}

#endif /* BSPLINE_HPP_ */