/*---------------------------------------------------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     | Website:  https://openfoam.org
    \\  /    A nd           | Copyright (C) 2011-2026 OpenFOAM Foundation
     \\/     M anipulation  |
-------------------------------------------------------------------------------
License
    This file is part of OpenFOAM.

    OpenFOAM 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 3 of the License, or
    (at your option) any later version.

    OpenFOAM 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.

    You should have received a copy of the GNU General Public License
    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.

\*---------------------------------------------------------------------------*/

#include "linearUpwind.H"
#include "fvcGrad.H"

// * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * * //

template<class Type>
Foam::linearUpwind<Type>::linearUpwind
(
    const fvMesh& mesh,
    const surfaceScalarField& faceFlux
)
:
    upwind<Type>(mesh, faceFlux),
    gradSchemeName_("grad")
{}


template<class Type>
Foam::linearUpwind<Type>::linearUpwind
(
    const fvMesh& mesh,
    Istream& schemeData
)
:
    upwind<Type>(mesh, schemeData),
    gradSchemeName_(schemeData)
{}


template<class Type>
Foam::linearUpwind<Type>::linearUpwind
(
    const fvMesh& mesh,
    const surfaceScalarField& faceFlux,
    Istream& schemeData
)
:
    upwind<Type>(mesh, faceFlux, schemeData),
    gradSchemeName_(schemeData)
{}


// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //

template<class Type>
Foam::tmp<Foam::SurfaceField<Type>>
Foam::linearUpwind<Type>::correction
(
    const VolField<Type>& vf
) const
{
    const fvMesh& mesh = this->mesh();

    tmp<SurfaceField<Type>> tsfCorr
    (
        SurfaceField<Type>::New
        (
            word("linearUpwind::correction(", vf.name(), ')'),
            mesh,
            dimensioned<Type>(vf.name(), vf.dimensions(), Zero)
        )
    );

    SurfaceField<Type>& sfCorr = tsfCorr.ref();

    const surfaceScalarField& faceFlux = this->faceFlux_;

    const labelList& owner = mesh.owner();
    const labelList& neighbour = mesh.neighbour();

    const volVectorField& C = mesh.C();
    const surfaceVectorField& Cf = mesh.Cf();

    tmp<fv::gradScheme<scalar>> gradScheme_
    (
        fv::gradScheme<scalar>::New
        (
            mesh,
            mesh.schemes().grad(gradSchemeName_)
        )
    );

    for (direction cmpt = 0; cmpt < pTraits<Type>::nComponents; cmpt++)
    {
        tmp<volVectorField> tgradVf =
            gradScheme_().fvcGrad(vf.component(cmpt), gradSchemeName_);

        const volVectorField& gradVf = tgradVf();

        forAll(faceFlux, facei)
        {
            const label celli =
                (faceFlux[facei] > 0) ? owner[facei] : neighbour[facei];

            setComponent(sfCorr[facei], cmpt) =
                (Cf[facei] - C[celli]) & gradVf[celli];
        }

        typename SurfaceField<Type>::BoundaryField& bSfCorr =
            sfCorr.boundaryFieldRef();

        forAll(bSfCorr, patchi)
        {
            fvsPatchField<Type>& pSfCorr = bSfCorr[patchi];

            if (pSfCorr.coupled())
            {
                const labelUList& pOwner = mesh.boundary()[patchi].faceCells();
                const vectorField& pCf = Cf.boundaryField()[patchi];
                const scalarField& pFaceFlux = faceFlux.boundaryField()[patchi];

                const vectorField pGradVfNei
                (
                    gradVf.boundaryField()[patchi].patchNeighbourField()
                );

                // Build the d-vectors
                const vectorField pd
                (
                    Cf.boundaryField()[patchi].patch().delta()
                );

                forAll(pOwner, facei)
                {
                    const label own = pOwner[facei];

                    if (pFaceFlux[facei] > 0)
                    {
                        setComponent(pSfCorr[facei], cmpt) =
                            (pCf[facei] - C[own])
                          & gradVf[own];
                    }
                    else
                    {
                        setComponent(pSfCorr[facei], cmpt) =
                            (pCf[facei] - pd[facei] - C[own])
                          & pGradVfNei[facei];
                    }
                }
            }
        }
    }

    return tsfCorr;
}


// ************************************************************************* //