/* ----------------------------------------------------------------------
   LIGGGHTS - LAMMPS Improved for General Granular and Granular Heat
   Transfer Simulations

   LIGGGHTS is part of the CFDEMproject
   www.liggghts.com | www.cfdem.com

   Christoph Kloss, christoph.kloss@cfdem.com
   Copyright 2009-2012 JKU Linz
   Copyright 2012-     DCS Computing GmbH, Linz

   LIGGGHTS is based on LAMMPS
   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
   http://lammps.sandia.gov, Sandia National Laboratories
   Steve Plimpton, sjplimp@sandia.gov

   This software is distributed under the GNU General Public License.

   See the README file in the top-level directory.
------------------------------------------------------------------------- */

/* ----------------------------------------------------------------------
   Contributing authors:
   Christoph Kloss (JKU Linz, DCS Computing GmbH, Linz)
   Richard Berger (JKU Linz)
------------------------------------------------------------------------- */
#ifdef NORMAL_MODEL
NORMAL_MODEL(HERTZ,hertz,3)
#else
#ifndef NORMAL_MODEL_HERTZ_H_
#define NORMAL_MODEL_HERTZ_H_
#include "global_properties.h"
#include "math.h"

namespace ContactModels
{
  template<typename Style>
  class NormalModel<HERTZ, Style> : protected Pointers
  {
  public:
    static const int MASK = CM_REGISTER_SETTINGS | CM_CONNECT_TO_PROPERTIES | CM_COLLISION;

    NormalModel(LAMMPS * lmp, IContactHistorySetup*) : Pointers(lmp),
      Yeff(NULL),
      Geff(NULL),
      betaeff(NULL)
    {
      
    }

    void registerSettings(Settings & settings)
    {
      settings.registerOnOff("tangential_damping", tangential_damping, true);
    }

    void connectToProperties(PropertyRegistry & registry) {
      registry.registerProperty("Yeff", &MODEL_PARAMS::createYeff);
      registry.registerProperty("Geff", &MODEL_PARAMS::createGeff);
      registry.registerProperty("betaeff", &MODEL_PARAMS::createBetaEff);

      registry.connect("Yeff", Yeff);
      registry.connect("Geff", Geff);
      registry.connect("betaeff", betaeff);
    }

    inline void collision(CollisionData & cdata, ForceData & i_forces, ForceData & j_forces)
    {
      const int itype = cdata.itype;
      const int jtype = cdata.jtype;
      double ri = cdata.radi;
      double rj = cdata.radj;
      double reff=cdata.is_wall ? cdata.radi : (ri*rj/(ri+rj));
      double meff=cdata.meff;

      double sqrtval = sqrt(reff*cdata.deltan);

      double Sn=2.*Yeff[itype][jtype]*sqrtval;
      double St=8.*Geff[itype][jtype]*sqrtval;

      double kn=4./3.*Yeff[itype][jtype]*sqrtval;
      double kt=St;
      const double sqrtFiveOverSix = 0.91287092917527685576161630466800355658790782499663875;
      double gamman=-2.*sqrtFiveOverSix*betaeff[itype][jtype]*sqrt(Sn*meff);
      double gammat=-2.*sqrtFiveOverSix*betaeff[itype][jtype]*sqrt(St*meff);
      if (!tangential_damping) gammat = 0.0;

      // convert Kn and Kt from pressure units to force/distance^2
      kn /= force->nktv2p;
      kt /= force->nktv2p;

      const double Fn_damping = -gamman*cdata.vn;
      const double Fn_contact = kn*(cdata.radsum-cdata.r);
      const double Fn = Fn_contact + Fn_damping;

      cdata.Fn = Fn;
      cdata.kn = kn;
      cdata.kt = kt;
      cdata.gamman = gamman;
      cdata.gammat = gammat;

      // apply normal force
      if(cdata.is_wall) {
        const double Fn_ = Fn * cdata.area_ratio;
        i_forces.delta_F[0] = Fn_ * cdata.en[0];
        i_forces.delta_F[1] = Fn_ * cdata.en[1];
        i_forces.delta_F[2] = Fn_ * cdata.en[2];
      } else {
        i_forces.delta_F[0] = cdata.Fn * cdata.en[0];
        i_forces.delta_F[1] = cdata.Fn * cdata.en[1];
        i_forces.delta_F[2] = cdata.Fn * cdata.en[2];

        j_forces.delta_F[0] = -i_forces.delta_F[0];
        j_forces.delta_F[1] = -i_forces.delta_F[1];
        j_forces.delta_F[2] = -i_forces.delta_F[2];
      }
    }

    void noCollision(ContactData&, ForceData&, ForceData&){}
    void beginPass(CollisionData&, ForceData&, ForceData&){}
    void endPass(CollisionData&, ForceData&, ForceData&){}

  protected:
    double ** Yeff;
    double ** Geff;
    double ** betaeff;

    bool tangential_damping;
  };

}
#endif
#endif
