/*---------------------------------------------------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     |
    \\  /    A nd           | Copyright held by original author
     \\/     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 2 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, write to the Free Software Foundation,
    Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA

Application
    blockCoupledScalarTransportFoam

Description
    Solves two coupled transport equations in a block-coupled manner

        1) transport equation for a passive scalar
        2) diffusion only

    This resembles heat exchanging flow through a porous medium

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

#include "fvCFD.H"
#include "fieldTypes.H"
#include "Time.H"
#include "fvMesh.H"

#include "blockLduSolvers.H"
#include "VectorNFieldTypes.H"
#include "volVectorNFields.H"
#include "blockVectorNMatrices.H"

#include "blockMatrixTools.H"

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

int main(int argc, char *argv[])
{

#   include "setRootCase.H"
#   include "createTime.H"
#   include "createMesh.H"
#   include "createFields.H"

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

    Info<< "\nCalculating scalar transport\n" << endl;

#   include "CourantNo.H"

    for (runTime++; !runTime.end(); runTime++)
    {
        Info<< "Time = " << runTime.timeName() << nl << endl;

#       include "readSIMPLEControls.H"

        for (int nonOrth=0; nonOrth<=nNonOrthCorr; nonOrth++)
        {
            fvScalarMatrix TEqn
            (
                fvm::div(phi, T)
              - fvm::laplacian(DT, T)
             ==
                 alpha*Ts
              - fvm::Sp(alpha, T)
            );

            TEqn.relax();

            fvScalarMatrix TsEqn
            (
              - fvm::laplacian(DTs, Ts)
             ==
                 alpha*T
              - fvm::Sp(alpha, Ts)
            );

            TsEqn.relax();

            // Prepare block system
            BlockLduMatrix<vector2> blockM(mesh);

            // Grab block diagonal and set it to zero
            Field<tensor2>& d = blockM.diag().asSquare();
            d = tensor2::zero;

            // Grab linear off-diagonal and set it to zero
            Field<vector2>& u = blockM.upper().asLinear();
            Field<vector2>& l = blockM.lower().asLinear();
            u = vector2::zero;
            l = vector2::zero;

            vector2Field& blockX = blockT.internalField();
            // vector2Field blockX(mesh.nCells(), vector2::zero);
            vector2Field blockB(mesh.nCells(), vector2::zero);

            //- Inset equations into block Matrix
            blockMatrixTools::insertEquation(0, TEqn, blockM, blockX, blockB);
            blockMatrixTools::insertEquation(1, TsEqn, blockM, blockX, blockB);

            //- Add off-diagonal terms and remove from Block source
            forAll(d, i)
            {
                d[i](0,1) = -alpha.value()*mesh.V()[i];
                d[i](1,0) = -alpha.value()*mesh.V()[i];

                blockB[i][0] -= alpha.value()*blockX[i][1]*mesh.V()[i];
                blockB[i][1] -= alpha.value()*blockX[i][0]*mesh.V()[i];
            }

            //- Transfer the coupled interface list for processor/cyclic/etc.
            // boundaries
            blockM.interfaces() = blockT.boundaryField().blockInterfaces();

            //- Transfer the coupled interface coefficients
            forAll(mesh.boundaryMesh(), patchI)
            {
                if (blockM.interfaces().set(patchI))
                {
                    Field<vector2>& coupledLower =
                        blockM.coupleLower()[patchI].asLinear();

                    Field<vector2>& coupledUpper =
                        blockM.coupleUpper()[patchI].asLinear();

                    const scalarField& TLower = TEqn.internalCoeffs()[patchI];
                    const scalarField& TUpper = TEqn.boundaryCoeffs()[patchI];

                    const scalarField& TsLower =
                        TsEqn.internalCoeffs()[patchI];

                    const scalarField& TsUpper =
                        TsEqn.boundaryCoeffs()[patchI];

                    blockMatrixTools::blockInsert(0, TLower, coupledLower);
                    blockMatrixTools::blockInsert(1, TsLower, coupledLower);
                    blockMatrixTools::blockInsert(0, TUpper, coupledUpper);
                    blockMatrixTools::blockInsert(1, TsUpper, coupledUpper);
                }
            }

            //- Block coupled solver call
            BlockSolverPerformance<vector2> solverPerf =
                BlockLduSolver<vector2>::New
                (
                    word("blockVar"),
                    blockM,
                    mesh.solutionDict().solver("blockVar")
                )->solve(blockX, blockB);

            solverPerf.print();

            // Retrieve solution
            blockMatrixTools::blockRetrieve(0, T.internalField(), blockX);
            blockMatrixTools::blockRetrieve(1, Ts.internalField(), blockX);

            T.correctBoundaryConditions();
            Ts.correctBoundaryConditions();
        }

        runTime.write();
    }

    Info<< "End\n" << endl;

    return(0);
}


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