multifluid.hpp

#pragma once

#include "nlohmann/json.hpp"

#include <Eigen/Dense>
#include <fstream>
#include <string>
#include <cmath>
#include <optional>
#include <variant>
#include <filesystem>

#include "teqp/derivs.hpp"
#include "teqp/types.hpp"
#include "teqp/constants.hpp"
#include "teqp/filesystem.hpp"

#include "MultiComplex/MultiComplex.hpp"

#include "multifluid_eosterms.hpp"
#include <boost/algorithm/string/join.hpp>

// See https://eigen.tuxfamily.org/dox/TopicCustomizing_CustomScalar.html
namespace Eigen {
    template<typename TN> struct NumTraits<mcx::MultiComplex<TN>> : NumTraits<double> // permits to get the epsilon, dummy_precision, lowest, highest functions
    {
        enum {
            IsComplex = 1,
            IsInteger = 0,
            IsSigned = 1,
            RequireInitialization = 1,
            ReadCost = 1,
            AddCost = 3,
            MulCost = 3
        };
    };
}

namespace teqp{

/// Load a JSON file from a specified file
inline nlohmann::json load_a_JSON_file(const std::string& path) {
    if (!std::filesystem::is_regular_file(path)) {
        throw std::invalid_argument("Path to be loaded does not exist: " + path);
    }
    auto stream = std::ifstream(path);
    if (!stream) {
        throw std::invalid_argument("File stream cannot be opened from: " + path);
    }
    try {
        return nlohmann::json::parse(stream);
    }
    catch (...) {
        throw std::invalid_argument("File at " + path + " is not valid JSON");
    }
}

template<typename EOSCollection>
class CorrespondingStatesContribution {

private:
    const EOSCollection EOSs;
public:
    CorrespondingStatesContribution(EOSCollection&& EOSs) : EOSs(EOSs) {};

    template<typename TauType, typename DeltaType, typename MoleFractions>
    auto alphar(const TauType& tau, const DeltaType& delta, const MoleFractions& molefracs) const {
        using resulttype = std::common_type_t<decltype(tau), decltype(molefracs[0]), decltype(delta)>; // Type promotion, without the const-ness
        resulttype alphar = 0.0;
        auto N = molefracs.size();
        for (auto i = 0; i < N; ++i) {
            alphar = alphar + molefracs[i] * EOSs[i].alphar(tau, delta);
        }
        return forceeval(alphar);
    }

    template<typename TauType, typename DeltaType>
    auto alphari(const TauType& tau, const DeltaType& delta, std::size_t i) const {
        using resulttype = std::common_type_t<decltype(tau), decltype(delta)>; // Type promotion, without the const-ness
        return EOSs[i].alphar(tau, delta);
    }

    auto get_EOS(std::size_t i) const{
        return EOSs[i];
    }
};

template<typename FCollection, typename DepartureFunctionCollection>
class DepartureContribution {

private:
    const FCollection F;
    const DepartureFunctionCollection funcs;
public:
    DepartureContribution(FCollection&& F, DepartureFunctionCollection&& funcs) : F(F), funcs(funcs) {};

    template<typename TauType, typename DeltaType, typename MoleFractions>
    auto alphar(const TauType& tau, const DeltaType& delta, const MoleFractions& molefracs) const {
        using resulttype = std::common_type_t<decltype(tau), decltype(molefracs[0]), decltype(delta)>; // Type promotion, without the const-ness
        resulttype alphar = 0.0;
        auto N = molefracs.size();
        for (auto i = 0; i < N; ++i) {
            for (auto j = i+1; j < N; ++j) {
                alphar = alphar + molefracs[i] * molefracs[j] * F(i, j) * funcs[i][j].alphar(tau, delta);
            }
        }
        return forceeval(alphar);
    }
};

template<typename ReducingFunction, typename CorrespondingTerm, typename DepartureTerm>
class MultiFluid {  

private:
    std::string meta = ""; ///< A string that can be used to store arbitrary metadata as needed
public:
    const ReducingFunction redfunc;
    const CorrespondingTerm corr;
    const DepartureTerm dep;

    template<class VecType>
    auto R(const VecType& molefrac) const {
        return get_R_gas<decltype(molefrac[0])>();
    }

    /// Store some sort of metadata in string form (perhaps a JSON representation of the model?)
    void set_meta(const std::string& m) { meta = m; }
    /// Get the metadata stored in string form
    auto get_meta() const { return meta; }

    MultiFluid(ReducingFunction&& redfunc, CorrespondingTerm&& corr, DepartureTerm&& dep) : redfunc(redfunc), corr(corr), dep(dep) {};

    template<typename TType, typename RhoType>
    auto alphar(TType T,
        const RhoType& rhovec,
        const std::optional<typename RhoType::value_type> rhotot = std::nullopt) const
    {
        typename RhoType::value_type rhotot_ = (rhotot.has_value()) ? rhotot.value() : std::accumulate(std::begin(rhovec), std::end(rhovec), (decltype(rhovec[0]))0.0);
        auto molefrac = rhovec / rhotot_;
        return alphar(T, rhotot_, molefrac);
    }

    template<typename TType, typename RhoType, typename MoleFracType>
    auto alphar(const TType &T,
        const RhoType &rho,
        const MoleFracType& molefrac) const
    {
        auto Tred = forceeval(redfunc.get_Tr(molefrac));
        auto rhored = forceeval(redfunc.get_rhor(molefrac));
        auto delta = forceeval(rho / rhored);
        auto tau = forceeval(Tred / T);
        auto val = corr.alphar(tau, delta, molefrac) + dep.alphar(tau, delta, molefrac);
        return forceeval(val);
    }
};


class MultiFluidReducingFunction {
private:
    Eigen::MatrixXd YT, Yv;

    template <typename Num>
    auto cube(Num x) const {
        return forceeval(x*x*x);
    }
    template <typename Num>
    auto square(Num x) const {
        return forceeval(x*x);
    }

public:
    const Eigen::MatrixXd betaT, gammaT, betaV, gammaV;
    const Eigen::ArrayXd Tc, vc;

    template<typename ArrayLike>
    MultiFluidReducingFunction(
        const Eigen::MatrixXd& betaT, const Eigen::MatrixXd& gammaT,
        const Eigen::MatrixXd& betaV, const Eigen::MatrixXd& gammaV,
        const ArrayLike& Tc, const ArrayLike& vc)
        : betaT(betaT), gammaT(gammaT), betaV(betaV), gammaV(gammaV), Tc(Tc), vc(vc) {

        auto N = Tc.size();

        YT.resize(N, N); YT.setZero();
        Yv.resize(N, N); Yv.setZero();
        for (auto i = 0; i < N; ++i) {
            for (auto j = i + 1; j < N; ++j) {
                YT(i, j) = betaT(i, j) * gammaT(i, j) * sqrt(Tc[i] * Tc[j]);
                YT(j, i) = betaT(j, i) * gammaT(j, i) * sqrt(Tc[i] * Tc[j]);
                Yv(i, j) = 1.0 / 8.0 * betaV(i, j) * gammaV(i, j) * cube(cbrt(vc[i]) + cbrt(vc[j]));
                Yv(j, i) = 1.0 / 8.0 * betaV(j, i) * gammaV(j, i) * cube(cbrt(vc[i]) + cbrt(vc[j]));
            }
        }
    }

    template <typename MoleFractions>
    auto Y(const MoleFractions& z, const Eigen::ArrayXd& Yc, const Eigen::MatrixXd& beta, const Eigen::MatrixXd& Yij) const {

        auto N = z.size();
        typename MoleFractions::value_type sum1 = 0.0;