DihedralTerm.h

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#ifndef MOLECULARMECHANICS_DIHEDRALTERM_H
#define MOLECULARMECHANICS_DIHEDRALTERM_H

#include "../Topology/DihedralType.h"
#include "Dihedral.h"
#include "InteractionTermBase.h"
#include <Utils/Math/AutomaticDifferentiation/Second3D.h>
#include <Utils/Typenames.h>

namespace Scine {

namespace Utils {
class AtomicSecondDerivativeCollection;
class Tensor33;
} // namespace Utils

namespace MolecularMechanics {
class DihedralTerm : public InteractionTermBase {
 public:
  using AtomIndex = int;

  DihedralTerm(AtomIndex firstAtom, AtomIndex secondAtom, AtomIndex thirdAtom, AtomIndex fourthAtom,
               const Dihedral& dihedral, const DihedralType& typeOfDihedral);
  ~DihedralTerm();

  double evaluateDihedralTerm(const Utils::PositionCollection& positions,
                              Utils::AtomicSecondDerivativeCollection& derivatives) const;

  static double getTheta(const Eigen::Vector3d& A, const Eigen::Vector3d& B, const Eigen::Vector3d& G);
  DihedralType getTypeOfDihedral() const;

  int getFirstAtom() const;

  int getSecondAtom() const;

  int getThirdAtom() const;

  int getFourthAtom() const;

 private:
  Utils::AutomaticDifferentiation::Second3D threeDimDer(const Utils::AutomaticDifferentiation::Second1D& energy,
                                                        const Utils::AutomaticDifferentiation::Second3D& alpha) const;
  void setSecondDerivative(Utils::AutomaticDifferentiation::Second3D& h, const Utils::Tensor33& tensor, double derFirst,
                           double derSecond) const;

  AtomIndex firstAtom_, secondAtom_, thirdAtom_, fourthAtom_;
  Dihedral dihedral_;
  DihedralType typeOfDihedral_;
};

} // namespace MolecularMechanics
} // namespace Scine

#endif // MOLECULARMECHANICS_DIHEDRALTERM_H