// -*- c++ -*-

// This file is part of the Collective Variables module (Colvars).
// The original version of Colvars and its updates are located at:
// https://github.com/colvars/colvars
// Please update all Colvars source files before making any changes.
// If you wish to distribute your changes, please submit them to the
// Colvars repository at GitHub.

#include "colvarmodule.h"
#include "colvar.h"
#include "colvarcomp.h"

#include <cmath>



colvar::angle::angle(std::string const &conf)
  : cvc(conf)
{
  function_type = "angle";
  provide(f_cvc_inv_gradient);
  provide(f_cvc_Jacobian);
  enable(f_cvc_com_based);

  group1 = parse_group(conf, "group1");
  group2 = parse_group(conf, "group2");
  group3 = parse_group(conf, "group3");

  init_total_force_params(conf);

  x.type(colvarvalue::type_scalar);
}


colvar::angle::angle(cvm::atom const &a1,
                     cvm::atom const &a2,
                     cvm::atom const &a3)
{
  function_type = "angle";
  provide(f_cvc_inv_gradient);
  provide(f_cvc_Jacobian);
  enable(f_cvc_com_based);

  group1 = new cvm::atom_group(std::vector<cvm::atom>(1, a1));
  group2 = new cvm::atom_group(std::vector<cvm::atom>(1, a2));
  group3 = new cvm::atom_group(std::vector<cvm::atom>(1, a3));
  atom_groups.push_back(group1);
  atom_groups.push_back(group2);
  atom_groups.push_back(group3);

  x.type(colvarvalue::type_scalar);
}


colvar::angle::angle()
{
  function_type = "angle";
  x.type(colvarvalue::type_scalar);
}


void colvar::angle::calc_value()
{
  cvm::atom_pos const g1_pos = group1->center_of_mass();
  cvm::atom_pos const g2_pos = group2->center_of_mass();
  cvm::atom_pos const g3_pos = group3->center_of_mass();

  r21  = cvm::position_distance(g2_pos, g1_pos);
  r21l = r21.norm();
  r23  = cvm::position_distance(g2_pos, g3_pos);
  r23l = r23.norm();

  cvm::real     const cos_theta = (r21*r23)/(r21l*r23l);

  x.real_value = (180.0/PI) * std::acos(cos_theta);
}


void colvar::angle::calc_gradients()
{
  cvm::real const cos_theta = (r21*r23)/(r21l*r23l);
  cvm::real const dxdcos = -1.0 / std::sqrt(1.0 - cos_theta*cos_theta);

  dxdr1 = (180.0/PI) * dxdcos *
    (1.0/r21l) * ( r23/r23l + (-1.0) * cos_theta * r21/r21l );

  dxdr3 = (180.0/PI) * dxdcos *
    (1.0/r23l) * ( r21/r21l + (-1.0) * cos_theta * r23/r23l );

  group1->set_weighted_gradient(dxdr1);
  group2->set_weighted_gradient((dxdr1 + dxdr3) * (-1.0));
  group3->set_weighted_gradient(dxdr3);
}


void colvar::angle::calc_force_invgrads()
{
  // This uses a force measurement on groups 1 and 3 only
  // to keep in line with the implicit variable change used to
  // evaluate the Jacobian term (essentially polar coordinates
  // centered on group2, which means group2 is kept fixed
  // when propagating changes in the angle)

  if (is_enabled(f_cvc_one_site_total_force)) {
    group1->read_total_forces();
    cvm::real norm_fact = 1.0 / dxdr1.norm2();
    ft.real_value = norm_fact * dxdr1 * group1->total_force();
  } else {
    group1->read_total_forces();
    group3->read_total_forces();
    cvm::real norm_fact = 1.0 / (dxdr1.norm2() + dxdr3.norm2());
    ft.real_value = norm_fact * ( dxdr1 * group1->total_force()
                                + dxdr3 * group3->total_force());
  }
  return;
}


void colvar::angle::calc_Jacobian_derivative()
{
  // det(J) = (2 pi) r^2 * sin(theta)
  // hence Jd = cot(theta)
  const cvm::real theta = x.real_value * PI / 180.0;
  jd = PI / 180.0 * (theta != 0.0 ? std::cos(theta) / std::sin(theta) : 0.0);
}


void colvar::angle::apply_force(colvarvalue const &force)
{
  if (!group1->noforce)
    group1->apply_colvar_force(force.real_value);

  if (!group2->noforce)
    group2->apply_colvar_force(force.real_value);

  if (!group3->noforce)
    group3->apply_colvar_force(force.real_value);
}


simple_scalar_dist_functions(angle)



colvar::dipole_angle::dipole_angle(std::string const &conf)
  : cvc(conf)
{
  function_type = "dipole_angle";
  group1 = parse_group(conf, "group1");
  group2 = parse_group(conf, "group2");
  group3 = parse_group(conf, "group3");

  init_total_force_params(conf);

  x.type(colvarvalue::type_scalar);
}


colvar::dipole_angle::dipole_angle(cvm::atom const &a1,
                      cvm::atom const &a2,
                      cvm::atom const &a3)
{
  function_type = "dipole_angle";

  group1 = new cvm::atom_group(std::vector<cvm::atom>(1, a1));
  group2 = new cvm::atom_group(std::vector<cvm::atom>(1, a2));
  group3 = new cvm::atom_group(std::vector<cvm::atom>(1, a3));
  atom_groups.push_back(group1);
  atom_groups.push_back(group2);
  atom_groups.push_back(group3);

  x.type(colvarvalue::type_scalar);
}


colvar::dipole_angle::dipole_angle()
{
  function_type = "dipole_angle";
  x.type(colvarvalue::type_scalar);
}


void colvar::dipole_angle::calc_value()
{
  cvm::atom_pos const g1_pos = group1->center_of_mass();
  cvm::atom_pos const g2_pos = group2->center_of_mass();
  cvm::atom_pos const g3_pos = group3->center_of_mass();

  group1->calc_dipole(g1_pos);

  r21 = group1->dipole();
  r21l = r21.norm();
  r23  = cvm::position_distance(g2_pos, g3_pos);
  r23l = r23.norm();

  cvm::real     const cos_theta = (r21*r23)/(r21l*r23l);

  x.real_value = (180.0/PI) * std::acos(cos_theta);
}

//to be implemented
//void colvar::dipole_angle::calc_force_invgrads(){}
//void colvar::dipole_angle::calc_Jacobian_derivative(){}

void colvar::dipole_angle::calc_gradients()
{
  cvm::real const cos_theta = (r21*r23)/(r21l*r23l);
  cvm::real const dxdcos = -1.0 / std::sqrt(1.0 - cos_theta*cos_theta);

  dxdr1 = (180.0/PI) * dxdcos *
  (1.0/r21l)* (r23/r23l + (-1.0) * cos_theta * r21/r21l );

  dxdr3 =  (180.0/PI) * dxdcos *
    (1.0/r23l) * ( r21/r21l + (-1.0) * cos_theta * r23/r23l );

  //this auxiliar variables are to avoid numerical errors inside "for"
  double aux1 = group1->total_charge/group1->total_mass;
  // double aux2 = group2->total_charge/group2->total_mass;
  // double aux3 = group3->total_charge/group3->total_mass;

  size_t i;
  for (i = 0; i < group1->size(); i++) {
    (*group1)[i].grad =((*group1)[i].charge + (-1)* (*group1)[i].mass * aux1) * (dxdr1);
  }

  for (i = 0; i < group2->size(); i++) {
    (*group2)[i].grad = ((*group2)[i].mass/group2->total_mass)* dxdr3 * (-1.0);
  }

  for (i = 0; i < group3->size(); i++) {
    (*group3)[i].grad =((*group3)[i].mass/group3->total_mass) * (dxdr3);
  }
}


void colvar::dipole_angle::apply_force(colvarvalue const &force)
{
  if (!group1->noforce)
    group1->apply_colvar_force(force.real_value);

  if (!group2->noforce)
    group2->apply_colvar_force(force.real_value);

  if (!group3->noforce)
    group3->apply_colvar_force(force.real_value);
}


simple_scalar_dist_functions(dipole_angle)



colvar::dihedral::dihedral(std::string const &conf)
  : cvc(conf)
{
  function_type = "dihedral";
  period = 360.0;
  b_periodic = true;
  provide(f_cvc_inv_gradient);
  provide(f_cvc_Jacobian);
  enable(f_cvc_com_based);

  group1 = parse_group(conf, "group1");
  group2 = parse_group(conf, "group2");
  group3 = parse_group(conf, "group3");
  group4 = parse_group(conf, "group4");

  init_total_force_params(conf);

  x.type(colvarvalue::type_scalar);
}


colvar::dihedral::dihedral(cvm::atom const &a1,
                           cvm::atom const &a2,
                           cvm::atom const &a3,
                           cvm::atom const &a4)
{
  if (cvm::debug())
    cvm::log("Initializing dihedral object from atom groups.\n");

  function_type = "dihedral";
  period = 360.0;
  b_periodic = true;
  provide(f_cvc_inv_gradient);
  provide(f_cvc_Jacobian);
  enable(f_cvc_com_based);

  b_1site_force = false;

  group1 = new cvm::atom_group(std::vector<cvm::atom>(1, a1));
  group2 = new cvm::atom_group(std::vector<cvm::atom>(1, a2));
  group3 = new cvm::atom_group(std::vector<cvm::atom>(1, a3));
  group4 = new cvm::atom_group(std::vector<cvm::atom>(1, a4));
  atom_groups.push_back(group1);
  atom_groups.push_back(group2);
  atom_groups.push_back(group3);
  atom_groups.push_back(group4);

  x.type(colvarvalue::type_scalar);

  if (cvm::debug())
    cvm::log("Done initializing dihedral object from atom groups.\n");
}


colvar::dihedral::dihedral()
{
  function_type = "dihedral";
  period = 360.0;
  b_periodic = true;
  provide(f_cvc_inv_gradient);
  provide(f_cvc_Jacobian);
  x.type(colvarvalue::type_scalar);
}


void colvar::dihedral::calc_value()
{
  cvm::atom_pos const g1_pos = group1->center_of_mass();
  cvm::atom_pos const g2_pos = group2->center_of_mass();
  cvm::atom_pos const g3_pos = group3->center_of_mass();
  cvm::atom_pos const g4_pos = group4->center_of_mass();

  // Usual sign convention: r12 = r2 - r1
  r12 = cvm::position_distance(g1_pos, g2_pos);
  r23 = cvm::position_distance(g2_pos, g3_pos);
  r34 = cvm::position_distance(g3_pos, g4_pos);

  cvm::rvector const n1 = cvm::rvector::outer(r12, r23);
  cvm::rvector const n2 = cvm::rvector::outer(r23, r34);

  cvm::real const cos_phi = n1 * n2;
  cvm::real const sin_phi = n1 * r34 * r23.norm();

  x.real_value = (180.0/PI) * std::atan2(sin_phi, cos_phi);
  this->wrap(x);
}


void colvar::dihedral::calc_gradients()
{
  cvm::rvector A = cvm::rvector::outer(r12, r23);
  cvm::real   rA = A.norm();
  cvm::rvector B = cvm::rvector::outer(r23, r34);
  cvm::real   rB = B.norm();
  cvm::rvector C = cvm::rvector::outer(r23, A);
  cvm::real   rC = C.norm();

  cvm::real const cos_phi = (A*B)/(rA*rB);
  cvm::real const sin_phi = (C*B)/(rC*rB);

  cvm::rvector f1, f2, f3;

  rB = 1.0/rB;
  B *= rB;

  if (std::fabs(sin_phi) > 0.1) {
    rA = 1.0/rA;
    A *= rA;
    cvm::rvector const dcosdA = rA*(cos_phi*A-B);
    cvm::rvector const dcosdB = rB*(cos_phi*B-A);
    rA = 1.0;

    cvm::real const K = (1.0/sin_phi) * (180.0/PI);

	f1 = K * cvm::rvector::outer(r23, dcosdA);
	f3 = K * cvm::rvector::outer(dcosdB, r23);
	f2 = K * (cvm::rvector::outer(dcosdA, r12)
		   +  cvm::rvector::outer(r34, dcosdB));
  }
  else {
    rC = 1.0/rC;
    C *= rC;
    cvm::rvector const dsindC = rC*(sin_phi*C-B);
    cvm::rvector const dsindB = rB*(sin_phi*B-C);
    rC = 1.0;

    cvm::real    const K = (-1.0/cos_phi) * (180.0/PI);

    f1.x = K*((r23.y*r23.y + r23.z*r23.z)*dsindC.x
              - r23.x*r23.y*dsindC.y
              - r23.x*r23.z*dsindC.z);
    f1.y = K*((r23.z*r23.z + r23.x*r23.x)*dsindC.y
              - r23.y*r23.z*dsindC.z
              - r23.y*r23.x*dsindC.x);
    f1.z = K*((r23.x*r23.x + r23.y*r23.y)*dsindC.z
              - r23.z*r23.x*dsindC.x
              - r23.z*r23.y*dsindC.y);

    f3 = cvm::rvector::outer(dsindB, r23);
    f3 *= K;

    f2.x = K*(-(r23.y*r12.y + r23.z*r12.z)*dsindC.x
              +(2.0*r23.x*r12.y - r12.x*r23.y)*dsindC.y
              +(2.0*r23.x*r12.z - r12.x*r23.z)*dsindC.z
              +dsindB.z*r34.y - dsindB.y*r34.z);
    f2.y = K*(-(r23.z*r12.z + r23.x*r12.x)*dsindC.y
              +(2.0*r23.y*r12.z - r12.y*r23.z)*dsindC.z
              +(2.0*r23.y*r12.x - r12.y*r23.x)*dsindC.x
              +dsindB.x*r34.z - dsindB.z*r34.x);
    f2.z = K*(-(r23.x*r12.x + r23.y*r12.y)*dsindC.z
              +(2.0*r23.z*r12.x - r12.z*r23.x)*dsindC.x
              +(2.0*r23.z*r12.y - r12.z*r23.y)*dsindC.y
              +dsindB.y*r34.x - dsindB.x*r34.y);
  }

  group1->set_weighted_gradient(-f1);
  group2->set_weighted_gradient(-f2 + f1);
  group3->set_weighted_gradient(-f3 + f2);
  group4->set_weighted_gradient(f3);
}


void colvar::dihedral::calc_force_invgrads()
{
  cvm::rvector const u12 = r12.unit();
  cvm::rvector const u23 = r23.unit();
  cvm::rvector const u34 = r34.unit();

  cvm::real const d12 = r12.norm();
  cvm::real const d34 = r34.norm();

  cvm::rvector const cross1 = (cvm::rvector::outer(u23, u12)).unit();
  cvm::rvector const cross4 = (cvm::rvector::outer(u23, u34)).unit();

  cvm::real const dot1 = u23 * u12;
  cvm::real const dot4 = u23 * u34;

  cvm::real const fact1 = d12 * std::sqrt(1.0 - dot1 * dot1);
  cvm::real const fact4 = d34 * std::sqrt(1.0 - dot4 * dot4);

  group1->read_total_forces();
  if (is_enabled(f_cvc_one_site_total_force)) {
    // This is only measuring the force on group 1
    ft.real_value = PI/180.0 * fact1 * (cross1 * group1->total_force());
  } else {
    // Default case: use groups 1 and 4
    group4->read_total_forces();
    ft.real_value = PI/180.0 * 0.5 * (fact1 * (cross1 * group1->total_force())
				      + fact4 * (cross4 * group4->total_force()));
  }
}


void colvar::dihedral::calc_Jacobian_derivative()
{
  // With this choice of inverse gradient ("internal coordinates"), Jacobian correction is 0
  jd = 0.0;
}


void colvar::dihedral::apply_force(colvarvalue const &force)
{
  if (!group1->noforce)
    group1->apply_colvar_force(force.real_value);

  if (!group2->noforce)
    group2->apply_colvar_force(force.real_value);

  if (!group3->noforce)
    group3->apply_colvar_force(force.real_value);

  if (!group4->noforce)
    group4->apply_colvar_force(force.real_value);
}


// metrics functions for cvc implementations with a periodicity

cvm::real colvar::dihedral::dist2(colvarvalue const &x1,
                                  colvarvalue const &x2) const
{
  cvm::real diff = x1.real_value - x2.real_value;
  diff = (diff < -180.0 ? diff + 360.0 : (diff > 180.0 ? diff - 360.0 : diff));
  return diff * diff;
}


colvarvalue colvar::dihedral::dist2_lgrad(colvarvalue const &x1,
                                          colvarvalue const &x2) const
{
  cvm::real diff = x1.real_value - x2.real_value;
  diff = (diff < -180.0 ? diff + 360.0 : (diff > 180.0 ? diff - 360.0 : diff));
  return 2.0 * diff;
}


colvarvalue colvar::dihedral::dist2_rgrad(colvarvalue const &x1,
                                          colvarvalue const &x2) const
{
  cvm::real diff = x1.real_value - x2.real_value;
  diff = (diff < -180.0 ? diff + 360.0 : (diff > 180.0 ? diff - 360.0 : diff));
  return (-2.0) * diff;
}


void colvar::dihedral::wrap(colvarvalue &x) const
{
  if ((x.real_value - wrap_center) >= 180.0) {
    x.real_value -= 360.0;
    return;
  }

  if ((x.real_value - wrap_center) < -180.0) {
    x.real_value += 360.0;
    return;
  }

  return;
}
