#ifndef WARPX_FINITE_DIFFERENCE_ALGORITHM_YEE_H_
#define WARPX_FINITE_DIFFERENCE_ALGORITHM_YEE_H_

#include <AMReX_REAL.H>
#include <AMReX_Array4.H>
#include <AMReX_Gpu.H>

struct YeeAlgorithm {

    static void InitializeStencilCoefficients(
        std::array<amrex::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
    static amrex::Real UpwardDx(
        amrex::Array4<amrex::Real> const& F,
        amrex::Real const* coefs_x, int const n_coefs_x,
        int const i, int const j, int const k ) {

        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
    static amrex::Real DownwardDx(
        amrex::Array4<amrex::Real> const& F,
        amrex::Real const* coefs_x, int const n_coefs_x,
        int const i, int const j, int const k ) {

        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
    static amrex::Real UpwardDy(
        amrex::Array4<amrex::Real> const& F,
        amrex::Real const* coefs_y, int const n_coefs_y,
        int const i, int const j, int const k ) {

        #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
    static amrex::Real DownwardDy(
        amrex::Array4<amrex::Real> const& F,
        amrex::Real const* coefs_y, int const n_coefs_y,
        int const i, int const j, int const k ) {

        #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
    static amrex::Real UpwardDz(
        amrex::Array4<amrex::Real> const& F,
        amrex::Real const* coefs_z, int const n_coefs_z,
        int const i, int const j, int const k ) {

        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
    };

    AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
    static amrex::Real DownwardDz(
        amrex::Array4<amrex::Real> const& F,
        amrex::Real const* coefs_z, int const n_coefs_z,
        int const i, int const j, int const k ) {

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

};

#endif // WARPX_FINITE_DIFFERENCE_ALGORITHM_YEE_H_