///////////////////////////////////////////////////////////////////////////////
//
// File: LinearHLLSolver.cpp
//
// For more information, please see: http://www.nektar.info
//
// The MIT License
//
// Copyright (c) 2006 Division of Applied Mathematics, Brown University (USA),
// Department of Aeronautics, Imperial College London (UK), and Scientific
// Computing and Imaging Institute, University of Utah (USA).
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
// THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//
// Description: HLL Riemann solver for the Linear Shallow Water Equations.
//              Only valid for constant depth
//
///////////////////////////////////////////////////////////////////////////////

#include <ShallowWaterSolver/RiemannSolvers/LinearHLLSolver.h>

namespace Nektar
{

std::string LinearHLLSolver::solverName =
    SolverUtils::GetRiemannSolverFactory().RegisterCreatorFunction(
        "LinearHLL", LinearHLLSolver::create, "Linear HLL Riemann solver");

LinearHLLSolver::LinearHLLSolver(
    const LibUtilities::SessionReaderSharedPtr &pSession)
    : LinearSWESolver(pSession)
{
}

/**
 * @brief HLL Riemann solver for the linear Shallow Water Equations
 *
 * @param etaL   Free surface elevation left state.
 * @param etaR   Free surface elevation right state.
 * @param uL     x-velocity  left state.
 * @param uR     x-velocity  right state.
 * @param vL     y-velocity  left state.
 * @param vR     y-velocity  right state.
 * @param dL     still water depth component left state.
 * @param dR     still water depth component right state.
 * @param etaf   Computed Riemann flux for continuity.
 * @param uf     Computed Riemann flux for x-momentum component
 * @param vf     Computed Riemann flux for y-momentum component
 */
void LinearHLLSolver::v_PointSolve(NekDouble etaL, NekDouble uL, NekDouble vL,
                                   NekDouble dL, NekDouble etaR, NekDouble uR,
                                   NekDouble vR, NekDouble dR, NekDouble &etaf,
                                   NekDouble &uf, NekDouble &vf)
{
    static NekDouble g = m_params["gravity"]();

    ASSERTL0(dL == dR, "not constant depth in LinearHLL");

    // Left and right wave speeds
    NekDouble cL = sqrt(g * dL);
    NekDouble cR = sqrt(g * dR);

    NekDouble SL = uL - cL;
    NekDouble SR = uR + cR;

    if (SL >= 0)
    {
        etaf = dL * uL;
        uf   = g * etaL;
        vf   = 0.0;
    }
    else if (SR <= 0)
    {
        etaf = dR * uR;
        uf   = g * etaR;
        vf   = 0.0;
    }
    else
    {
        etaf =
            (SR * dL * uL - SL * dR * uR + SL * SR * (etaR - etaL)) / (SR - SL);
        uf = (SR * g * etaL - SL * g * etaR + SL * SR * (uR - uL)) / (SR - SL);
        vf = (SL * SR * (vR - vL)) / (SR - SL);
    }
}

} // namespace Nektar
