// clang-format off
/*----------------------------------------------------------------------
  PuReMD - Purdue ReaxFF Molecular Dynamics Program

  Copyright (2010) Purdue University
  Hasan Metin Aktulga, hmaktulga@lbl.gov
  Joseph Fogarty, jcfogart@mail.usf.edu
  Sagar Pandit, pandit@usf.edu
  Ananth Y Grama, ayg@cs.purdue.edu

  Please cite the related publication:
  H. M. Aktulga, J. C. Fogarty, S. A. Pandit, A. Y. Grama,
  "Parallel Reactive Molecular Dynamics: Numerical Methods and
  Algorithmic Techniques", Parallel Computing, in press.

  This program is free software; you can redistribute it and/or
  modify it under the terms of the GNU General Public License as
  published by the Free Software Foundation; either version 2 of
  the License, or (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  See the GNU General Public License for more details:
  <https://www.gnu.org/licenses/>.
  ----------------------------------------------------------------------*/

#include "reaxff_api.h"

#include <cmath>

#include "pair.h"
#include "error.h"

namespace ReaxFF {
  void Calculate_Theta(rvec dvec_ji, double d_ji, rvec dvec_jk, double d_jk,
                        double *theta, double *cos_theta)
  {
    (*cos_theta) = rvec_Dot(dvec_ji,dvec_jk) / (d_ji * d_jk);
    if (*cos_theta > 1.) *cos_theta  = 1.0;
    if (*cos_theta < -1.) *cos_theta  = -1.0;

    (*theta) = acos(*cos_theta);
  }

  void Calculate_dCos_Theta(rvec dvec_ji, double d_ji, rvec dvec_jk, double d_jk,
                             rvec* dcos_theta_di,
                             rvec* dcos_theta_dj,
                             rvec* dcos_theta_dk)
  {
    int t;
    double sqr_d_ji = SQR(d_ji);
    double sqr_d_jk = SQR(d_jk);
    double inv_dists = 1.0 / (d_ji * d_jk);
    double inv_dists3 = CUBE(inv_dists);
    double dot_dvecs = rvec_Dot(dvec_ji,dvec_jk);
    double Cdot_inv3 = dot_dvecs * inv_dists3;

    for (t = 0; t < 3; ++t) {
      (*dcos_theta_di)[t] = dvec_jk[t] * inv_dists -
        Cdot_inv3 * sqr_d_jk * dvec_ji[t];
      (*dcos_theta_dj)[t] = -(dvec_jk[t] + dvec_ji[t]) * inv_dists +
        Cdot_inv3 * (sqr_d_jk * dvec_ji[t] + sqr_d_ji * dvec_jk[t]);
      (*dcos_theta_dk)[t] = dvec_ji[t] * inv_dists -
        Cdot_inv3 * sqr_d_ji * dvec_jk[t];
    }
  }


  void Valence_Angles(reax_system *system, control_params *control, simulation_data *data,
                      storage *workspace, reax_list **lists)
  {
    int i, j, pi, k, pk, t;
    int type_i, type_j, type_k;
    int start_j, end_j, start_pk, end_pk;
    int cnt, num_thb_intrs;

    double temp, temp_bo_jt, pBOjt7;
    double p_val1, p_val2, p_val3, p_val4, p_val5;
    double p_val6, p_val7, p_val8, p_val9, p_val10;
    double p_pen1, p_pen2, p_pen3, p_pen4;
    double p_coa1, p_coa2, p_coa3, p_coa4;
    double trm8, expval6, expval7, expval2theta, expval12theta, exp3ij, exp3jk;
    double exp_pen2ij, exp_pen2jk, exp_pen3, exp_pen4, trm_pen34, exp_coa2;
    double dSBO1, dSBO2, SBO, SBO2, CSBO2, SBOp, prod_SBO, vlpadj;
    double CEval1, CEval2, CEval3, CEval4, CEval5, CEval6, CEval7, CEval8;
    double CEpen1, CEpen2, CEpen3;
    double e_ang, e_coa, e_pen;
    double CEcoa1, CEcoa2, CEcoa3, CEcoa4, CEcoa5;
    double Cf7ij, Cf7jk, Cf8j, Cf9j;
    double f7_ij, f7_jk, f8_Dj, f9_Dj;
    double Ctheta_0, theta_0, theta_00, theta, cos_theta, sin_theta;
    double BOA_ij, BOA_jk;

    // Tallying variables
    double eng_tmp, fi_tmp[3], fj_tmp[3], fk_tmp[3];
    double delij[3], delkj[3];

    three_body_header *thbh;
    three_body_parameters *thbp;
    three_body_interaction_data *p_ijk, *p_kji;
    bond_data *pbond_ij, *pbond_jk, *pbond_jt;
    bond_order_data *bo_ij, *bo_jk, *bo_jt;
    reax_list *bonds = (*lists) + BONDS;
    reax_list *thb_intrs =  (*lists) + THREE_BODIES;

    /* global parameters used in these calculations */
    p_val6 = system->reax_param.gp.l[14];
    p_val8 = system->reax_param.gp.l[33];
    p_val9 = system->reax_param.gp.l[16];
    p_val10 = system->reax_param.gp.l[17];
    num_thb_intrs = 0;


    for (j = 0; j < system->N; ++j) {
      type_j = system->my_atoms[j].type;
      if (type_j < 0) continue;
      start_j = Start_Index(j, bonds);
      end_j = End_Index(j, bonds);

      p_val3 = system->reax_param.sbp[type_j].p_val3;
      p_val5 = system->reax_param.sbp[type_j].p_val5;

      SBOp = 0, prod_SBO = 1;
      for (t = start_j; t < end_j; ++t) {
        bo_jt = &(bonds->select.bond_list[t].bo_data);
        SBOp += (bo_jt->BO_pi + bo_jt->BO_pi2);
        temp = SQR(bo_jt->BO);
        temp *= temp;
        temp *= temp;
        prod_SBO *= exp(-temp);
      }

      if (workspace->vlpex[j] >= 0) {
        vlpadj = 0;
        dSBO2 = prod_SBO - 1;
      } else {
        vlpadj = workspace->nlp[j];
        dSBO2 = (prod_SBO - 1) * (1 - p_val8 * workspace->dDelta_lp[j]);
      }

      SBO = SBOp + (1 - prod_SBO) * (-workspace->Delta_boc[j] - p_val8 * vlpadj);
      dSBO1 = -8 * prod_SBO * (workspace->Delta_boc[j] + p_val8 * vlpadj);

      if (SBO <= 0)
        SBO2 = 0, CSBO2 = 0;
      else if (SBO > 0 && SBO <= 1) {
        SBO2 = pow(SBO, p_val9);
        CSBO2 = p_val9 * pow(SBO, p_val9 - 1);
      }
      else if (SBO > 1 && SBO < 2) {
        SBO2 = 2 - pow(2-SBO, p_val9);
        CSBO2 = p_val9 * pow(2 - SBO, p_val9 - 1);
      }
      else
        SBO2 = 2, CSBO2 = 0;

      expval6 = exp(p_val6 * workspace->Delta_boc[j]);

      for (pi = start_j; pi < end_j; ++pi) {
        Set_Start_Index(pi, num_thb_intrs, thb_intrs);
        pbond_ij = &(bonds->select.bond_list[pi]);
        bo_ij = &(pbond_ij->bo_data);
        BOA_ij = bo_ij->BO - control->thb_cut;


        if (BOA_ij/*bo_ij->BO*/ > 0.0 &&
             (j < system->n || pbond_ij->nbr < system->n)) {
          i = pbond_ij->nbr;
          type_i = system->my_atoms[i].type;

          for (pk = start_j; pk < pi; ++pk) {
            start_pk = Start_Index(pk, thb_intrs);
            end_pk = End_Index(pk, thb_intrs);

            for (t = start_pk; t < end_pk; ++t)
              if (thb_intrs->select.three_body_list[t].thb == i) {
                p_ijk = &(thb_intrs->select.three_body_list[num_thb_intrs]);
                p_kji = &(thb_intrs->select.three_body_list[t]);

                p_ijk->thb = bonds->select.bond_list[pk].nbr;
                p_ijk->pthb  = pk;
                p_ijk->theta = p_kji->theta;
                rvec_Copy(p_ijk->dcos_di, p_kji->dcos_dk);
                rvec_Copy(p_ijk->dcos_dj, p_kji->dcos_dj);
                rvec_Copy(p_ijk->dcos_dk, p_kji->dcos_di);

                ++num_thb_intrs;
                break;
              }
          }

          for (pk = pi+1; pk < end_j; ++pk) {
            pbond_jk = &(bonds->select.bond_list[pk]);
            bo_jk    = &(pbond_jk->bo_data);
            BOA_jk   = bo_jk->BO - control->thb_cut;
            k        = pbond_jk->nbr;
            type_k   = system->my_atoms[k].type;
            p_ijk    = &(thb_intrs->select.three_body_list[num_thb_intrs]);

            Calculate_Theta(pbond_ij->dvec, pbond_ij->d,
                             pbond_jk->dvec, pbond_jk->d,
                             &theta, &cos_theta);

            Calculate_dCos_Theta(pbond_ij->dvec, pbond_ij->d,
                                  pbond_jk->dvec, pbond_jk->d,
                                  &(p_ijk->dcos_di), &(p_ijk->dcos_dj),
                                  &(p_ijk->dcos_dk));
            p_ijk->thb = k;
            p_ijk->pthb = pk;
            p_ijk->theta = theta;

            sin_theta = sin(theta);
            if (sin_theta < 1.0e-5)
              sin_theta = 1.0e-5;

            ++num_thb_intrs;

            if ((j < system->n) && (BOA_jk > 0.0) &&
                (bo_ij->BO > control->thb_cut) &&
                (bo_jk->BO > control->thb_cut) &&
                (bo_ij->BO * bo_jk->BO > control->thb_cutsq)) {
              thbh = &(system->reax_param.thbp[type_i][type_j][type_k]);

              for (cnt = 0; cnt < thbh->cnt; ++cnt) {
                if (fabs(thbh->prm[cnt].p_val1) > 0.001) {
                  thbp = &(thbh->prm[cnt]);

                  /* ANGLE ENERGY */
                  p_val1 = thbp->p_val1;
                  p_val2 = thbp->p_val2;
                  p_val4 = thbp->p_val4;
                  p_val7 = thbp->p_val7;
                  theta_00 = thbp->theta_00;

                  exp3ij = exp(-p_val3 * pow(BOA_ij, p_val4));
                  f7_ij = 1.0 - exp3ij;
                  Cf7ij = p_val3 * p_val4 * pow(BOA_ij, p_val4 - 1.0) * exp3ij;

                  exp3jk = exp(-p_val3 * pow(BOA_jk, p_val4));
                  f7_jk = 1.0 - exp3jk;
                  Cf7jk = p_val3 * p_val4 * pow(BOA_jk, p_val4 - 1.0) * exp3jk;

                  expval7 = exp(-p_val7 * workspace->Delta_boc[j]);
                  trm8 = 1.0 + expval6 + expval7;
                  f8_Dj = p_val5 - ((p_val5 - 1.0) * (2.0 + expval6) / trm8);
                  Cf8j = ((1.0 - p_val5) / SQR(trm8)) *
                    (p_val6 * expval6 * trm8 -
                      (2.0 + expval6) * (p_val6*expval6 - p_val7*expval7));

                  theta_0 = 180.0 - theta_00 * (1.0 -
                                                exp(-p_val10 * (2.0 - SBO2)));
                  theta_0 = DEG2RAD(theta_0);

                  expval2theta  = exp(-p_val2 * SQR(theta_0 - theta));
                  if (p_val1 >= 0)
                    expval12theta = p_val1 * (1.0 - expval2theta);
                  else // To avoid linear Me-H-Me angles (6/6/06)
                    expval12theta = p_val1 * -expval2theta;

                  CEval1 = Cf7ij * f7_jk * f8_Dj * expval12theta;
                  CEval2 = Cf7jk * f7_ij * f8_Dj * expval12theta;
                  CEval3 = Cf8j  * f7_ij * f7_jk * expval12theta;
                  CEval4 = -2.0 * p_val1 * p_val2 * f7_ij * f7_jk * f8_Dj *
                    expval2theta * (theta_0 - theta);

                  Ctheta_0 = p_val10 * DEG2RAD(theta_00) *
                    exp(-p_val10 * (2.0 - SBO2));

                  CEval5 = -CEval4 * Ctheta_0 * CSBO2;
                  CEval6 = CEval5 * dSBO1;
                  CEval7 = CEval5 * dSBO2;
                  CEval8 = -CEval4 / sin_theta;

                  data->my_en.e_ang += e_ang =
                    f7_ij * f7_jk * f8_Dj * expval12theta;
                  /* END ANGLE ENERGY*/

                  /* PENALTY ENERGY */
                  p_pen1 = thbp->p_pen1;
                  p_pen2 = system->reax_param.gp.l[19];
                  p_pen3 = system->reax_param.gp.l[20];
                  p_pen4 = system->reax_param.gp.l[21];

                  exp_pen2ij = exp(-p_pen2 * SQR(BOA_ij - 2.0));
                  exp_pen2jk = exp(-p_pen2 * SQR(BOA_jk - 2.0));
                  exp_pen3 = exp(-p_pen3 * workspace->Delta[j]);
                  exp_pen4 = exp( p_pen4 * workspace->Delta[j]);
                  trm_pen34 = 1.0 + exp_pen3 + exp_pen4;
                  f9_Dj = (2.0 + exp_pen3) / trm_pen34;
                  Cf9j = (-p_pen3 * exp_pen3 * trm_pen34 -
                           (2.0 + exp_pen3) * (-p_pen3 * exp_pen3 +
                                                p_pen4 * exp_pen4)) /
                    SQR(trm_pen34);

                  data->my_en.e_pen += e_pen =
                    p_pen1 * f9_Dj * exp_pen2ij * exp_pen2jk;

                  CEpen1 = e_pen * Cf9j / f9_Dj;
                  temp   = -2.0 * p_pen2 * e_pen;
                  CEpen2 = temp * (BOA_ij - 2.0);
                  CEpen3 = temp * (BOA_jk - 2.0);
                  /* END PENALTY ENERGY */

                  /* COALITION ENERGY */
                  p_coa1 = thbp->p_coa1;
                  p_coa2 = system->reax_param.gp.l[2];
                  p_coa3 = system->reax_param.gp.l[38];
                  p_coa4 = system->reax_param.gp.l[30];

                  exp_coa2 = exp(p_coa2 * workspace->Delta_val[j]);
                  data->my_en.e_coa += e_coa =
                    p_coa1 / (1. + exp_coa2) *
                    exp(-p_coa3 * SQR(workspace->total_bond_order[i]-BOA_ij)) *
                    exp(-p_coa3 * SQR(workspace->total_bond_order[k]-BOA_jk)) *
                    exp(-p_coa4 * SQR(BOA_ij - 1.5)) *
                    exp(-p_coa4 * SQR(BOA_jk - 1.5));

                  CEcoa1 = -2 * p_coa4 * (BOA_ij - 1.5) * e_coa;
                  CEcoa2 = -2 * p_coa4 * (BOA_jk - 1.5) * e_coa;
                  CEcoa3 = -p_coa2 * exp_coa2 * e_coa / (1 + exp_coa2);
                  CEcoa4 = -2 * p_coa3 *
                    (workspace->total_bond_order[i]-BOA_ij) * e_coa;
                  CEcoa5 = -2 * p_coa3 *
                    (workspace->total_bond_order[k]-BOA_jk) * e_coa;
                  /* END COALITION ENERGY */

                  /* FORCES */
                  bo_ij->Cdbo += (CEval1 + CEpen2 + (CEcoa1 - CEcoa4));
                  bo_jk->Cdbo += (CEval2 + CEpen3 + (CEcoa2 - CEcoa5));
                  workspace->CdDelta[j] += ((CEval3 + CEval7) + CEpen1 + CEcoa3);
                  workspace->CdDelta[i] += CEcoa4;
                  workspace->CdDelta[k] += CEcoa5;

                  for (t = start_j; t < end_j; ++t) {
                    pbond_jt = &(bonds->select.bond_list[t]);
                    bo_jt = &(pbond_jt->bo_data);
                    temp_bo_jt = bo_jt->BO;
                    temp = CUBE(temp_bo_jt);
                    pBOjt7 = temp * temp * temp_bo_jt;

                    bo_jt->Cdbo += (CEval6 * pBOjt7);
                    bo_jt->Cdbopi += CEval5;
                    bo_jt->Cdbopi2 += CEval5;
                  }

                  rvec_ScaledAdd(workspace->f[i], CEval8, p_ijk->dcos_di);
                  rvec_ScaledAdd(workspace->f[j], CEval8, p_ijk->dcos_dj);
                  rvec_ScaledAdd(workspace->f[k], CEval8, p_ijk->dcos_dk);

                  /* tally energy */
                  if (system->pair_ptr->eflag_either) {
                    eng_tmp = e_ang + e_pen + e_coa;
                    system->pair_ptr->ev_tally(j,j,system->N,1,eng_tmp,0.0,0.0,0.0,0.0,0.0);
                  }

                  /* tally virial */
                  if (system->pair_ptr->vflag_either) {

                    /* Acquire vectors */
                    rvec_ScaledSum(delij, 1., system->my_atoms[i].x, -1., system->my_atoms[j].x);
                    rvec_ScaledSum(delkj, 1., system->my_atoms[k].x, -1., system->my_atoms[j].x);
                    rvec_Scale(fi_tmp, -CEval8, p_ijk->dcos_di);
                    rvec_Scale(fj_tmp, -CEval8, p_ijk->dcos_dj);
                    rvec_Scale(fk_tmp, -CEval8, p_ijk->dcos_dk);
                    system->pair_ptr->v_tally3(i,j,k,fi_tmp,fk_tmp,delij,delkj);
                  }
                }
              }
            }
          }
        }

        Set_End_Index(pi, num_thb_intrs, thb_intrs);
      }
    }

    if (num_thb_intrs >= thb_intrs->num_intrs * DANGER_ZONE) {
      workspace->realloc.num_3body = num_thb_intrs;
      if (num_thb_intrs > thb_intrs->num_intrs)
        control->error_ptr->one(FLERR, fmt::format("step {}: ran out of space on "
                                                   "angle_list: top={}, max={}",
                                                   data->step, num_thb_intrs,
                                                   thb_intrs->num_intrs));
    }
  }
}
