///////////////////////////////////////////////////////////////////////////////
//
// File: RoeSolver.h
//
// 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: Roe Riemann solver.
//
///////////////////////////////////////////////////////////////////////////////

#ifndef NEKTAR_SOLVERS_COMPRESSIBLEFLOWSOLVER_RIEMANNSOLVER_ROESOLVER
#define NEKTAR_SOLVERS_COMPRESSIBLEFLOWSOLVER_RIEMANNSOLVER_ROESOLVER

#include <CompressibleFlowSolver/RiemannSolvers/CompressibleSolver.h>

namespace Nektar
{
class RoeSolver : public CompressibleSolver
{
public:
    static RiemannSolverSharedPtr create(
        const LibUtilities::SessionReaderSharedPtr &pSession)
    {
        return RiemannSolverSharedPtr(new RoeSolver(pSession));
    }

    static std::string solverName;

    /// programmatic ctor
    RoeSolver();

protected:
    RoeSolver(const LibUtilities::SessionReaderSharedPtr &pSession);

    using ND = NekDouble;

    void v_PointSolve(ND rhoL, ND rhouL, ND rhovL, ND rhowL, ND EL, ND rhoR,
                      ND rhouR, ND rhovR, ND rhowR, ND ER, ND &rhof, ND &rhouf,
                      ND &rhovf, ND &rhowf, ND &Ef) final;

    void v_ArraySolve(const Array<OneD, const Array<OneD, ND>> &Fwd,
                      const Array<OneD, const Array<OneD, ND>> &Bwd,
                      Array<OneD, Array<OneD, ND>> &flux) final;
};

template <class T, typename = typename std::enable_if<
                       std::is_floating_point<T>::value ||
                       tinysimd::is_vector_floating_point<T>::value>::type>
inline void RoeKernel(T &rhoL, T &rhouL, T &rhovL, T &rhowL, T &EL, T &rhoR,
                      T &rhouR, T &rhovR, T &rhowR, T &ER, T &rhof, T &rhouf,
                      T &rhovf, T &rhowf, T &Ef, NekDouble gamma)
{
    // Left and right velocities
    T uL = rhouL / rhoL;
    T vL = rhovL / rhoL;
    T wL = rhowL / rhoL;
    T uR = rhouR / rhoR;
    T vR = rhovR / rhoR;
    T wR = rhowR / rhoR;

    // Left and right pressures
    T pL = (gamma - 1.0) * (EL - 0.5 * (rhouL * uL + rhovL * vL + rhowL * wL));
    T pR = (gamma - 1.0) * (ER - 0.5 * (rhouR * uR + rhovR * vR + rhowR * wR));

    // Left and right enthalpy
    T hL = (EL + pL) / rhoL;
    T hR = (ER + pR) / rhoR;

    // Square root of rhoL and rhoR.
    T srL  = sqrt(rhoL);
    T srR  = sqrt(rhoR);
    T srLR = srL + srR;

    // Velocity, enthalpy and sound speed Roe averages (equation 11.60).
    T uRoe = (srL * uL + srR * uR) / srLR;
    T vRoe = (srL * vL + srR * vR) / srLR;
    T wRoe = (srL * wL + srR * wR) / srLR;
    T hRoe = (srL * hL + srR * hR) / srLR;
    T URoe = (uRoe * uRoe + vRoe * vRoe + wRoe * wRoe);
    T cRoe = sqrt((gamma - 1.0) * (hRoe - 0.5 * URoe));

    // Compute eigenvectors (equation 11.59).
    T k[5][5] = {{1., uRoe - cRoe, vRoe, wRoe, hRoe - uRoe * cRoe},
                 {1., uRoe, vRoe, wRoe, 0.5 * URoe},
                 {0., 0., 1., 0., vRoe},
                 {0., 0., 0., 1., wRoe},
                 {1., uRoe + cRoe, vRoe, wRoe, hRoe + uRoe * cRoe}};

    // Calculate jumps \Delta u_i (defined preceding equation 11.67).
    T jump[5] = {rhoR - rhoL, rhouR - rhouL, rhovR - rhovL, rhowR - rhowL,
                 ER - EL};

    // Define \Delta u_5 (equation 11.70).
    T jumpbar = jump[4] - (jump[2] - vRoe * jump[0]) * vRoe -
                (jump[3] - wRoe * jump[0]) * wRoe;

    // Compute wave amplitudes (equations 11.68, 11.69).
    T alpha[5];
    alpha[1] = (gamma - 1.0) *
               (jump[0] * (hRoe - uRoe * uRoe) + uRoe * jump[1] - jumpbar) /
               (cRoe * cRoe);
    alpha[0] =
        (jump[0] * (uRoe + cRoe) - jump[1] - cRoe * alpha[1]) / (2.0 * cRoe);
    alpha[4] = jump[0] - (alpha[0] + alpha[1]);
    alpha[2] = jump[2] - vRoe * jump[0];
    alpha[3] = jump[3] - wRoe * jump[0];

    // Compute average of left and right fluxes needed for equation 11.29.
    rhof  = 0.5 * (rhoL * uL + rhoR * uR);
    rhouf = 0.5 * (pL + rhoL * uL * uL + pR + rhoR * uR * uR);
    rhovf = 0.5 * (rhoL * uL * vL + rhoR * uR * vR);
    rhowf = 0.5 * (rhoL * uL * wL + rhoR * uR * wR);
    Ef    = 0.5 * (uL * (EL + pL) + uR * (ER + pR));

    // Needed to get right overload resolution for std::abs
    using std::abs;

    // Compute eigenvalues \lambda_i (equation 11.58).
    T uRoeAbs   = abs(uRoe);
    T lambda[5] = {abs(uRoe - cRoe), uRoeAbs, uRoeAbs, uRoeAbs,
                   abs(uRoe + cRoe)};

    // Finally perform summation (11.29).
    for (size_t i = 0; i < 5; ++i)
    {
        uRoeAbs = 0.5 * alpha[i] * lambda[i];

        rhof -= uRoeAbs * k[i][0];
        rhouf -= uRoeAbs * k[i][1];
        rhovf -= uRoeAbs * k[i][2];
        rhowf -= uRoeAbs * k[i][3];
        Ef -= uRoeAbs * k[i][4];
    }
}

} // namespace Nektar

#endif
