/**
 * @file   interface_particles.cpp
 * @author Julian Iseringhausen <isering@ins.uni-bonn.de>
 * @date   Mon Apr 18 12:56:48 2011
 *
 * @brief  VMG::InterfaceParticles
 *
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#ifdef HAVE_MPI
#include <mpi.h>
#endif

#include <cmath>
#include <cstring>

#include "base/helper.hpp"
#include "base/index.hpp"
#include "base/linked_cell_list.hpp"
#include "base/vector.hpp"
#include "comm/comm.hpp"
#include "grid/grid.hpp"
#include "grid/multigrid.hpp"
#include "grid/tempgrid.hpp"
#include "interface/interface_particles.hpp"
#include "mg.hpp"

using namespace VMG;

void InterfaceParticles::ImportRightHandSide(Multigrid& multigrid)
{
  Index index_global, index_local, index;
  Vector pos_rel, pos_abs, grid_val;

  Factory& factory = MG::GetFactory();
  Comm& comm = *MG::GetComm();

  const int& near_field_cells = factory.GetObjectStorageVal<int>("PARTICLE_NEAR_FIELD_CELLS");

  Grid& grid = multigrid(multigrid.GlobalMaxLevel());
  Grid& particle_grid = comm.GetParticleGrid();

  particle_grid.Clear();

  /*
   * Distribute particles to their processes
   */
  particles.clear();
  comm.CommParticles(grid, particles);

  /*
   * Charge assignment on the grid
   */
  std::list<Particle::Particle>::iterator iter;

#ifdef DEBUG_OUTPUT
  vmg_float particle_charges = 0.0;
  for (iter=particles.begin(); iter!=particles.end(); ++iter)
    particle_charges += iter->Charge();
  particle_charges = MG::GetComm()->GlobalSumRoot(particle_charges);
  comm.PrintStringOnce("Particle list charge sum: %e", particle_charges);
#endif

  for (iter=particles.begin(); iter!=particles.end(); ++iter)
    spl.SetSpline(particle_grid, *iter, near_field_cells);

  // Communicate charges over halo
  comm.CommFromGhosts(particle_grid);

  // Assign charge values to the right hand side
  for (index.X()=0; index.X()<grid.Local().Size().X(); ++index.X())
    for (index.Y()=0; index.Y()<grid.Local().Size().Y(); ++index.Y())
      for (index.Z()=0; index.Z()<grid.Local().Size().Z(); ++index.Z())
        grid(index + grid.Local().Begin()) = particle_grid.GetVal(index + particle_grid.Local().Begin());

#ifdef DEBUG_OUTPUT
  Grid::iterator grid_iter;
  vmg_float charge_sum = 0.0;
  for (grid_iter=grid.Iterators().Local().Begin(); grid_iter!=grid.Iterators().Local().End(); ++grid_iter)
    charge_sum += grid.GetVal(*grid_iter);
  charge_sum = MG::GetComm()->GlobalSum(charge_sum);
  comm.PrintStringOnce("Grid charge sum: %e", charge_sum);
#endif
}

void InterfaceParticles::ExportSolution(Grid& grid)
{
  Index index;
  vmg_float length;
  Vector dist_vec;

#ifdef DEBUG_OUTPUT
  vmg_float e = 0.0;
  vmg_float e_long = 0.0;
  vmg_float e_self = 0.0;
#endif

  Factory& factory = MG::GetFactory();
  Comm& comm = *MG::GetComm();

  /*
   * Get parameters and arrays
   */
  const vmg_int& num_particles_local = factory.GetObjectStorageVal<vmg_int>("PARTICLE_NUM_LOCAL");
  const int& near_field_cells = factory.GetObjectStorageVal<int>("PARTICLE_NEAR_FIELD_CELLS");
  vmg_float* p = factory.GetObjectStorageArray<vmg_float>("PARTICLE_POTENTIAL_ARRAY");
  vmg_float* f = factory.GetObjectStorageArray<vmg_float>("PARTICLE_FORCE_ARRAY");

  const vmg_float r_cut = (near_field_cells+0.5) * grid.Extent().MeshWidth().Max();

  /*
   * Initialize potential
   */
  for (vmg_int i=0; i<num_particles_local; ++i) {
    p[i] = 0.0;
    for (vmg_int j=0;j<3;++j)
      f[3*i+j] = 0.;
  }

  /*
   * Copy potential values to a grid with sufficiently large halo size.
   * This may be optimized in future.
   * The parameters of this grid have been set in the import step.
   */
  Grid& particle_grid = comm.GetParticleGrid();

  for (index.X()=0; index.X()<grid.Local().Size().X(); ++index.X())
    for (index.Y()=0; index.Y()<grid.Local().Size().Y(); ++index.Y())
      for (index.Z()=0; index.Z()<grid.Local().Size().Z(); ++index.Z())
        particle_grid(index + particle_grid.Local().Begin()) = grid.GetVal(index + grid.Local().Begin());

  comm.CommToGhosts(particle_grid);

  /*
   * Do potential back-interpolation
   */
  std::list<Particle::Particle>::iterator p_iter;
  for (p_iter=particles.begin(); p_iter!=particles.end(); ++p_iter) {

    // Interpolate long range part of potential
    p_iter->Pot() = 0.5 * (Helper::InterpolateTrilinear(p_iter->Pos(), particle_grid) - p_iter->Charge() * spl.GetAntiDerivativeZero());

#ifdef DEBUG_OUTPUT
    e_long += 0.5 * p_iter->Charge() * Helper::InterpolateTrilinear(p_iter->Pos(), particle_grid);
    e_self += 0.5 * p_iter->Charge() * p_iter->Charge() * spl.GetAntiDerivativeZero();
#endif

  }

  comm.CommAddPotential(particles);

  /*
   * Compute near field correction
   */
  Particle::LinkedCellList lc(particles, near_field_cells, grid);
  Particle::LinkedCellList::iterator p1, p2;
  Grid::iterator iter;

  comm.CommLCListGhosts(grid, lc);

  for (iter=lc.Iterators().Local().Begin(); iter!=lc.Iterators().Local().End(); ++iter)
    for (p1=lc(*iter).begin(); p1!=lc(*iter).end(); ++p1)
      for (index.X()=-1*near_field_cells-1; index.X()<=near_field_cells+1; ++index.X())
  	for (index.Y()=-1*near_field_cells-1; index.Y()<=near_field_cells+1; ++index.Y())
  	  for (index.Z()=-1*near_field_cells-1; index.Z()<=near_field_cells+1; ++index.Z())
  	    for (p2=lc(*iter+index).begin(); p2!=lc(*iter+index).end(); ++p2)
  	      if (*p1 != *p2) {

  		length = (p2->Pos() - p1->Pos()).Length();

  		//TODO Rewrite this equation more efficiently
  		if (length < r_cut)
		  p1->Pot() += 0.5 * p2->Charge() / length * (0.25*M_1_PI + spl.EvaluatePotential(length));

  	      }

  comm.CommAddPotential(lc);

#ifdef DEBUG_OUTPUT
  vmg_float* q = factory.GetObjectStorageArray<vmg_float>("PARTICLE_CHARGE_ARRAY");

  for (int i=0; i<num_particles_local; ++i)
    e += p[i] * q[i];

  e = comm.GlobalSumRoot(e);
  e_long = comm.GlobalSumRoot(e_long);
  e_self = comm.GlobalSumRoot(e_self);

  comm.PrintStringOnce("E_long:  %e", e_long);
  comm.PrintStringOnce("E_short: %e", e - e_long + e_self);
  comm.PrintStringOnce("E_self:  %e", e_self);
  comm.PrintStringOnce("E_total: %e", e);

#endif /* DEBUG_OUTPUT */

}