#ifndef WARPX_FINITE_DIFFERENCE_ALGORITHM_YEE_H_
#define WARPX_FINITE_DIFFERENCE_ALGORITHM_YEE_H_

struct YeeAlgorithm {

    void InitializeStencilCoefficients( std::array<Real,3> cell_size,
        amrex::Gpu::ManagedVector<amrex::Real> stencil_coefs_x,
        amrex::Gpu::ManagedVector<amrex::Real> stencil_coefs_y,
        amrex::Gpu::ManagedVector<amrex::Real> stencil_coefs_z ) {

        // Store the inverse cell size along each direction in the coefficients
        stencil_coefs_x.resize(1);
        stencil_coefs_x[0] = 1./cell_size[0];
        stencil_coefs_y.resize(1);
        stencil_coefs_y[0] = 1./cell_size[1];
        stencil_coefs_z.resize(1);
        stencil_coefs_z[0] = 1./cell_size[2];
    }

    AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
    amrex::Real UpwardDx(
        Array4 const F, int const i, int const j, int const k,
        Real const* coefs_x, int const n_coefs_x ) {

        amrex::Real inv_dx = coefs_x[0];
        return inv_dx*( F(i+1,j,k) - F(i,j,k) );
    };

    AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
    amrex::Real DownwardDx(
        Array4 const F, int const i, int const j, int const k,
        Real const* coefs_x, int const n_coefs_x ) {

        amrex::Real inv_dx = coefs_x[0];
        return inv_dx*( F(i,j,k) - F(i-1,j,k) );
    };

    AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
    amrex::Real UpwardDy(
        Array4 const F, int const i, int const j, int const k,
        Real const* coefs_y, int const n_coefs_y ) {

        #if defined WARPX_DIM_3D
            amrex::Real inv_dy = coefs_y[0];
            return inv_dy*( F(i,j+1,k) - F(i,j,k) );
        #elif (defined WARPX_DIM_XZ)
            return 0; // 2D Cartesian: derivative along y is 0
        #endif
    };

    AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
    amrex::Real DownwardDy(
        Array4 const F, int const i, int const j, int const k,
        Real const* coefs_y, int const n_coefs_y ) {

        #if defined WARPX_DIM_3D
            amrex::Real inv_dy = coefs_y[0];
            return inv_dy*( F(i,j,k) - F(i,j-1,k) );
        #elif (defined WARPX_DIM_XZ)
            return 0; // 2D Cartesian: derivative along y is 0
        #endif
    };

    AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
    amrex::Real UpwardDz(
        Array4 const F, int const i, int const j, int const k,
        Real const* coefs_z, int const n_coefs_z ) {

        amrex::Real inv_dz = coefs_z[0];
        #if defined WARPX_DIM_3D
            return inv_dz*( F(i,j,k+1) - F(i,j,k) );
        #elif (defined WARPX_DIM_XZ)
            return inv_dz*( F(i,j+1,k) - F(i,j,k) );
        #endif
    };


}

#endif // WARPX_FINITE_DIFFERENCE_ALGORITHM_YEE_H_