/* This file is part of the Palabos library.
 *
 * The Palabos softare is developed since 2011 by FlowKit-Numeca Group Sarl
 * (Switzerland) and the University of Geneva (Switzerland), which jointly
 * own the IP rights for most of the code base. Since October 2019, the
 * Palabos project is maintained by the University of Geneva and accepts
 * source code contributions from the community.
 * 
 * Contact:
 * Jonas Latt
 * Computer Science Department
 * University of Geneva
 * 7 Route de Drize
 * 1227 Carouge, Switzerland
 * jonas.latt@unige.ch
 *
 * The most recent release of Palabos can be downloaded at 
 * <https://palabos.unige.ch/>
 *
 * The library Palabos is free software: you can redistribute it and/or
 * modify it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * The library 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

/** \file
 * Helper functions for the implementation of multi-phase models. This file is all
 * about efficiency. The generic template code is specialized for commonly
 * used Lattices, so that a maximum performance can be taken out of each
 * case.
 */
#ifndef MULTI_PHASE_TEMPLATES_2D_H
#define MULTI_PHASE_TEMPLATES_2D_H

#include "core/globalDefs.h"
#include "core/cell.h"
#include "multiPhysics/shanChenLattices2D.h"

namespace plb {

/// Helper functions with full-lattice access
template<typename T, template<typename U> class Descriptor>
struct multiPhaseTemplates2D {

static void shanChenInteraction( BlockLattice2D<T,Descriptor>& lattice,
                                 Array<T,Descriptor<T>::d>& rhoContribution,
                                 plint iX, plint iY )
{
    enum {
        densityOffset  = Descriptor<T>::ExternalField::densityBeginsAt
    };
                     
    rhoContribution.resetToZero();
    for (plint iPop = 0; iPop < Descriptor<T>::q; ++iPop) {
        plint nextX = iX + Descriptor<T>::c[iPop][0];
        plint nextY = iY + Descriptor<T>::c[iPop][1];
        Cell<T,Descriptor> const& cell = lattice.get(nextX,nextY);
        T rho = *cell.getExternal(densityOffset);
        for (int iD = 0; iD < Descriptor<T>::d; ++iD) {
           rhoContribution[iD] += Descriptor<T>::t[iPop] * rho * Descriptor<T>::c[iPop][iD];
        }
    }
}

};

template<typename T, template<typename U> class Descriptor>
struct multiPhaseHelpers2D {
typedef Descriptor<T> D;

static void computeRhoAndJ(BlockLattice2D<T,Descriptor>& lattice,
                           plint iX, plint iY)
{
    enum {
        densityOffset  = D::ExternalField::densityBeginsAt,
        momentumOffset = D::ExternalField::momentumBeginsAt
    };

    Cell<T,Descriptor>& cell = lattice.get(iX,iY);
    Array<T,Descriptor<T>::d> j;
    T rhoBar;
    cell.getDynamics().computeRhoBarJ(cell,rhoBar,j);
    momentTemplates<T,Descriptor>::get_j(cell,j);
    *cell.getExternal(densityOffset) = Descriptor<T>::fullRho(rhoBar);
    j.to_cArray(cell.getExternal(momentumOffset));
}

static void computeUstar(std::vector<BlockLattice2D<T,Descriptor>*> lattices,
                         plint iX, plint iY,
                         Array<T,Descriptor<T>::d>& uStar)
{
    enum {
        densityOffset  = D::ExternalField::densityBeginsAt,
        momentumOffset = D::ExternalField::momentumBeginsAt
    };

    plint numSpecies = (plint) lattices.size();
    std::vector<T> omega(numSpecies);
    T rhoStar = T();
    for (plint iSpecies=0; iSpecies<numSpecies; ++iSpecies) {
        Cell<T,Descriptor> const& cell = lattices[iSpecies]->get(iX,iY);
        omega[iSpecies] = cell.getDynamics().getOmega();
        rhoStar += omega[iSpecies] * (*cell.getExternal(densityOffset));
    }
    // Computation of the common velocity, shared among all populations.
    for (int iD = 0; iD < Descriptor<T>::d; ++iD) {
        uStar[iD] = T();
        for (plint iSpecies=0; iSpecies<numSpecies; ++iSpecies) {
            T *momentum = lattices[iSpecies]->get(iX,iY).getExternal(momentumOffset);
            uStar[iD] += momentum[iD] * omega[iSpecies];
        }
        uStar[iD] /= rhoStar;
    }
}

static void computeUphys(std::vector<BlockLattice2D<T,Descriptor>*> lattices,
                         plint iX, plint iY,
                         Array<T,Descriptor<T>::d>& uPhys)
{
    enum {      
        densityOffset  = D::ExternalField::densityBeginsAt,
        momentumOffset = D::ExternalField::momentumBeginsAt,
        gOffset        = D::ExternalField::GbeginsAt,
        interfOffset   = D::ExternalField::interactionFbeginsAt
    };       
    plint numSpecies = (plint) lattices.size();
    T rhoPhys = T();
    for (plint iSpecies=0; iSpecies<numSpecies; ++iSpecies) {
        Cell<T,Descriptor> const& cell = lattices[iSpecies]->get(iX,iY);
        rhoPhys += *cell.getExternal(densityOffset);
    }
    // Computation of the common velocity, shared among all populations.
    for (int iD = 0; iD < Descriptor<T>::d; ++iD) {
        uPhys[iD] = T();
        for (plint iSpecies=0; iSpecies<numSpecies; ++iSpecies) {
            Cell<T,Descriptor> const& cell = lattices[iSpecies]->get(iX,iY);
            T const *momentum = cell.getExternal(momentumOffset);
            T const *interf = cell.getExternal(interfOffset);
            T rho = *cell.getExternal(densityOffset);
            uPhys[iD] += momentum[iD] + 0.5*rho*interf[iD];
        }
        uPhys[iD] /= rhoPhys;
        T *externalf = lattices[0]->get(iX,iY).getExternal(gOffset);
        uPhys[iD] += 0.5*externalf[iD];
    }
}

};

template<typename T>
struct multiPhaseTemplates2D<T, descriptors::ForcedShanChenD2Q9Descriptor> {
    typedef descriptors::ForcedShanChenD2Q9Descriptor<T> D;

static void shanChenInteraction (
        BlockLattice2D<T,descriptors::ForcedShanChenD2Q9Descriptor>& lattice,
        Array<T,D::d>& rhoContribution,
        plint iX, plint iY )
{

    enum {
        densityOffset  = D::ExternalField::densityBeginsAt
    };

    T rho;
    rho = *lattice.get(iX-1,iY+1).getExternal(densityOffset);
    rhoContribution[0] = -D::t[1] * rho;
    rhoContribution[1] =  D::t[1] * rho;
    rho = *lattice.get(iX-1,iY  ).getExternal(densityOffset);
    rhoContribution[0] -= D::t[2] * rho;
    rho = *lattice.get(iX-1,iY-1).getExternal(densityOffset);
    rhoContribution[0] -= D::t[3] * rho;
    rhoContribution[1] -= D::t[3] * rho;
    rho = *lattice.get(iX  ,iY-1).getExternal(densityOffset);
    rhoContribution[1] -= D::t[4] * rho;
    rho = *lattice.get(iX+1,iY-1).getExternal(densityOffset);
    rhoContribution[0] += D::t[5] * rho;
    rhoContribution[1] -= D::t[5] * rho;
    rho = *lattice.get(iX+1,iY  ).getExternal(densityOffset);
    rhoContribution[0] += D::t[6] * rho;
    rho = *lattice.get(iX+1,iY+1).getExternal(densityOffset);
    rhoContribution[0] += D::t[7] * rho;
    rhoContribution[1] += D::t[7] * rho;
    rho = *lattice.get(iX  ,iY+1).getExternal(densityOffset);
    rhoContribution[1] += D::t[8] * rho;
}

};

}  // namespace plb

#endif  // MULTI_PHASE_TEMPLATES_2D_H
