/* Copyright 2021 Modern Electron
 *
 * This file is part of WarpX.
 *
 * License: BSD-3-Clause-LBNL
 */
#ifndef ELECTROSTATICSOLVER_H_
#define ELECTROSTATICSOLVER_H_

#include <AMReX_Array.H>
#include <AMReX_Geometry.H>
#include <AMReX_MultiFab.H>
#include <AMReX_MLMG.H>
#include <AMReX_REAL.H>
#include <AMReX_Parser.H>

#include <array>
#include <string>
#include <utility>


namespace ElectrostaticSolver {

    struct PhiCalculatorEB {

        amrex::Real t;
        amrex::ParserExecutor<4> potential_eb;

        AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
        amrex::Real operator()(const amrex::Real x, const amrex::Real z) const noexcept {
            using namespace amrex::literals;
            return potential_eb(x, 0.0_rt, z, t);
        }

        AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
        amrex::Real operator()(const amrex::Real x, const amrex::Real y, const amrex::Real z) const noexcept {
            return potential_eb(x, y, z, t);
        }
    };

    class PoissonBoundaryHandler {
    public:

        amrex::Array<amrex::LinOpBCType, AMREX_SPACEDIM> lobc, hibc;
        bool bcs_set = false;
        std::array<bool, AMREX_SPACEDIM * 2> dirichlet_flag;
        bool has_non_periodic = false;
        bool phi_EB_only_t = true;

        void definePhiBCs (const amrex::Geometry& geom);

        void buildParsers ();
        void buildParsersEB ();

        /* \brief Sets the EB potential string and updates the parsers
         *
         * \param [in] potential The string value of the potential
         */
        void setPotentialEB (std::string potential) {
            potential_eb_str = potential;
            buildParsersEB();
        }

        PhiCalculatorEB getPhiEB(amrex::Real t) const noexcept {
            return PhiCalculatorEB{t, potential_eb};
        }

        // set default potentials to zero in order for current tests to pass
        // but forcing the user to specify a potential might be better
        std::string potential_xlo_str = "0";
        std::string potential_xhi_str = "0";
        std::string potential_ylo_str = "0";
        std::string potential_yhi_str = "0";
        std::string potential_zlo_str = "0";
        std::string potential_zhi_str = "0";
        std::string potential_eb_str = "0";

        amrex::ParserExecutor<1> potential_xlo;
        amrex::ParserExecutor<1> potential_xhi;
        amrex::ParserExecutor<1> potential_ylo;
        amrex::ParserExecutor<1> potential_yhi;
        amrex::ParserExecutor<1> potential_zlo;
        amrex::ParserExecutor<1> potential_zhi;
        amrex::ParserExecutor<1> potential_eb_t;
        amrex::ParserExecutor<4> potential_eb;

    private:

        amrex::Parser potential_xlo_parser;
        amrex::Parser potential_xhi_parser;
        amrex::Parser potential_ylo_parser;
        amrex::Parser potential_yhi_parser;
        amrex::Parser potential_zlo_parser;
        amrex::Parser potential_zhi_parser;
        amrex::Parser potential_eb_parser;
    };

    /** use amrex to directly calculate the electric field since with EB's the
     *
     * simple finite difference scheme in WarpX::computeE sometimes fails
     */
    class EBCalcEfromPhiPerLevel {
      private:
        amrex::Vector<
            amrex::Array<amrex::MultiFab *, AMREX_SPACEDIM>
        > m_e_field;

      public:
        EBCalcEfromPhiPerLevel(amrex::Vector<amrex::Array<amrex::MultiFab *, AMREX_SPACEDIM> > e_field)
                : m_e_field(std::move(e_field)) {}

        void operator()(amrex::MLMG & mlmg, int const lev) {
            using namespace amrex::literals;

            mlmg.getGradSolution({m_e_field[lev]});
            for (auto &field: m_e_field[lev]) {
                field->mult(-1._rt);
            }
        }
    };
} // namespace ElectrostaticSolver

#endif // ELECTROSTATICSOLVER_H_