
/*!
From REFPROP:
temperature                     K
pressure, fugacity              kPa
density                         mol/L
composition                     mole fraction
quality                         mole basis (moles vapor/total moles)
enthalpy, internal energy       J/mol
Gibbs, Helmholtz free energy    J/mol
entropy, heat capacity          J/(mol.K)
speed of sound                  m/s
Joule-Thomson coefficient       K/kPa
d(p)/d(rho)                     kPa.L/mol
d2(p)/d(rho)2                   kPa.(L/mol)^2
viscosity                       microPa.s (10^-6 Pa.s)
thermal conductivity            W/(m.K)
dipole moment                   debye
surface tension                 N/m
*/

#define REFPROP_IMPLEMENTATION
#define REFPROP_CSTYLE_REFERENCES
#include "externals/REFPROP-headers/REFPROP_lib.h"
#undef REFPROP_IMPLEMENTATION
#undef REFPROP_CSTYLE_REFERENCES

#include "CoolPropTools.h"
#include "REFPROPMixtureBackend.h"
#include "REFPROPBackend.h"
#include "Exceptions.h"
#include "Configuration.h"
#include "CPfilepaths.h"
#include "CoolProp.h"
#include "Solvers.h"
#include "IdealCurves.h"
#include "DataStructures.h"
#include "AbstractState.h"

#include <stdlib.h>
#include <string>
#include <stdio.h>
#include <iostream>
#include <cassert>
#include "crossplatform_shared_ptr.h"
#include <stdlib.h>

#if defined(_MSC_VER)
#define _CRTDBG_MAP_ALLOC
#ifndef _CRT_SECURE_NO_WARNINGS
#define _CRT_SECURE_NO_WARNINGS
#endif
#include <crtdbg.h>
#include <sys/stat.h>
#else
#include <sys/stat.h>
#endif

std::string LoadedREFPROPRef;

static bool dbg_refprop = false;
static const unsigned int number_of_endings = 5;
std::string endings[number_of_endings] = {"", ".FLD", ".fld", ".PPF", ".ppf"};

static char default_reference_state[] = "DEF";

// Default location, can be over-ridden by configuration variable
#if defined(__powerpc__) || defined(__ISLINUX__) || defined(__ISAPPLE__)
    char refpropPath[] = "/opt/refprop";
#elif defined(__ISWINDOWS__)
    char refpropPath[] = "";
#else
    #pragma error
#endif

std::string get_REFPROP_fluid_path_prefix()
{
    std::string rpPath = refpropPath;
    // Allow the user to specify an alternative REFPROP path by configuration value
    std::string alt_refprop_path = CoolProp::get_config_string(ALTERNATIVE_REFPROP_PATH);
    std::string separator = get_separator();
    if (!alt_refprop_path.empty()){
        //if (!endswith(alt_refprop_path, separator)){
        //    throw CoolProp::ValueError(format("ALTERNATIVE_REFPROP_PATH [%s] must end with a path sparator, typically a slash character", alt_refprop_path.c_str()));
        //}
        if (!path_exists(alt_refprop_path)) {
            throw CoolProp::ValueError(format("ALTERNATIVE_REFPROP_PATH [%s] could not be found", alt_refprop_path.c_str()));
        }
        // The alternative path has been set, so we give all fluid paths as relative to this directory
        return join_path(alt_refprop_path,"fluids");
    }
    #if defined(__ISWINDOWS__)
        return rpPath;
    #elif defined(__ISLINUX__) || defined(__ISAPPLE__)
        return join_path(rpPath,"fluids");
    #else
        throw CoolProp::NotImplementedError("This function should not be called.");
        return rpPath;
    #endif
}
std::string get_REFPROP_mixtures_path_prefix()
{
    std::string rpPath = refpropPath;
    // Allow the user to specify an alternative REFPROP path by configuration value
    std::string alt_refprop_path = CoolProp::get_config_string(ALTERNATIVE_REFPROP_PATH);
    std::string separator = get_separator();
    if (!alt_refprop_path.empty()){
        //if (!endswith(alt_refprop_path, separator)) {
        //    throw CoolProp::ValueError(format("ALTERNATIVE_REFPROP_PATH [%s] must end with a path sparator, typically a slash character", alt_refprop_path.c_str()));
        //}
        if (!path_exists(alt_refprop_path)) {
            throw CoolProp::ValueError(format("ALTERNATIVE_REFPROP_PATH [%s] could not be found", alt_refprop_path.c_str()));
        }
        // The alternative path has been set
        return join_path(alt_refprop_path, "mixtures");
    }
    #if defined(__ISWINDOWS__)
        return rpPath;
    #elif defined(__ISLINUX__) || defined(__ISAPPLE__)
        return join_path(rpPath,"mixtures");
    #else
        throw CoolProp::NotImplementedError("This function should not be called.");
        return rpPath;
    #endif
}

/// Construct the path to the HMX.BNC file
std::string get_REFPROP_HMX_BNC_path()
{
    std::string alt_hmx_bnc_path = CoolProp::get_config_string(ALTERNATIVE_REFPROP_HMX_BNC_PATH);
    // Use the alternative HMX.BNC path if provided - replace all the path to HMX.BNC with provided path
    if (!alt_hmx_bnc_path.empty()){
        return alt_hmx_bnc_path;
    }
    else{
        // Otherwise fall back to default paths; get_REFPROP_fluid_path_prefix will query ALTERNATIVE_REFPROP_PATH
        return join_path(get_REFPROP_fluid_path_prefix(), "HMX.BNC");
    }
}


namespace CoolProp {

class REFPROPGenerator : public AbstractStateGenerator{
public:
    AbstractState * get_AbstractState(const std::vector<std::string> &fluid_names){
        REFPROPMixtureBackend::REFPROP_supported ();
        if (fluid_names.size() == 1){
            return new REFPROPBackend(fluid_names[0]);
        }
        else{
            return new REFPROPMixtureBackend(fluid_names);
        }
    };
};
// This static initialization will cause the generator to register
static GeneratorInitializer<REFPROPGenerator> refprop_gen(REFPROP_BACKEND_FAMILY);

void REFPROPMixtureBackend::construct(const std::vector<std::string>& fluid_names) {
    // Do the REFPROP instantiation for this fluid
    _mole_fractions_set = false;

    // Force loading of REFPROP
    REFPROP_supported();

    // Try to add this fluid to REFPROP - might want to think about making array of
    // components and setting mole fractions if they change a lot.
    this->set_REFPROP_fluids(fluid_names);

    // Bump the number of REFPROP backends that are in existence;
    REFPROPMixtureBackend::instance_counter++;

    // Set the imposed phase index to default value
    imposed_phase_index = iphase_not_imposed;
}

REFPROPMixtureBackend::~REFPROPMixtureBackend() {
    // Decrement the counter for the number of instances
    REFPROPMixtureBackend::instance_counter--;
    // Unload the shared library when the last instance is about to be destroyed
    if (REFPROPMixtureBackend::instance_counter == 0){
        force_unload_REFPROP();
    }
}
void REFPROPMixtureBackend::check_loaded_fluid()
{
    this->set_REFPROP_fluids(this->fluid_names);
}

std::size_t REFPROPMixtureBackend::instance_counter = 0; // initialise with 0
bool REFPROPMixtureBackend::_REFPROP_supported = true; // initialise with true
bool REFPROPMixtureBackend::REFPROP_supported () {
    /*
     * Here we build the bridge from macro definitions
     * into the actual code. This is also going to be
     * the central place to handle error messages on
     * unsupported platforms.
     */

    // Abort check if Refprop has been loaded.
    if (RefpropdllInstance!=NULL) return true;


    // Store result of previous check.
    if (_REFPROP_supported) {
        // Either Refprop is supported or it is the first check.
        std::string rpv(STRINGIFY(RPVersion));
        if (rpv.compare("NOTAVAILABLE")!=0) {
            // Function names were defined in "REFPROP_lib.h",
            // This platform theoretically supports Refprop.
            std::string err;
            const std::string alt_rp_path = get_config_string(ALTERNATIVE_REFPROP_PATH);
            const std::string alt_rp_name = get_config_string(ALTERNATIVE_REFPROP_LIBRARY_PATH);
            bool loaded_REFPROP = false;
            if (!alt_rp_name.empty()) {
                loaded_REFPROP = ::load_REFPROP(err, "", alt_rp_name);
            } else {
                if (alt_rp_path.empty()){
                    loaded_REFPROP = ::load_REFPROP(err, refpropPath, "");
                }
                else{
                    loaded_REFPROP = ::load_REFPROP(err, alt_rp_path, "");
                }
            }

            if (loaded_REFPROP) {
                return true;
            }
            else {
                printf("Good news: It is possible to use REFPROP on your system! However, the library \n");
                printf("could not be loaded. Please make sure that REFPROP is available on your system.\n\n");
                printf("Neither found in current location nor found in system PATH.\n");
                printf("If you already obtained a copy of REFPROP from http://www.nist.gov/srd/, \n");
                printf("add location of REFPROP to the PATH environment variable or your library path.\n\n");
                printf("In case you do not use Windows, have a look at https://github.com/jowr/librefprop.so \n");
                printf("to find instructions on how to compile your own version of the REFPROP library.\n\n");
                printf("ALTERNATIVE_REFPROP_PATH: %s\n", alt_rp_path.c_str());
                printf("ERROR: %s\n", err.c_str());
                _REFPROP_supported = false;
                return false;
            }
        } else {
            // No definition of function names, we do not expect
            // the Refprop library to be available.
            _REFPROP_supported = false;
            return false;
        }
    } else {
        return false;
    }
    return false;
}
std::string REFPROPMixtureBackend::version(){
    int N = -1;
    int ierr = 0;
    char fluids[10000] = "", hmx[] = "HMX.BNC", default_reference_state[] = "DEF", herr[255] = "";
    if (!REFPROP_supported()) {
      return "n/a";
    };
    // Pad the version string with NULL characters
    for (int i = 0; i < 255; ++i){
        herr[i] = '\0';
    }
    SETUPdll(&N, fluids, hmx, default_reference_state,
                &ierr, herr,
                10000, // Length of component_string (see PASS_FTN.for from REFPROP)
                refpropcharlength, // Length of path_HMX_BNC
                lengthofreference, // Length of reference
                errormessagelength // Length of error message
                );
    if (strlen(herr) == 0){
        return format("%g", ((double)ierr)/10000.0);
    }
    else{
        std::string s(herr, herr+254);
        return strstrip(s);
    }
}

void REFPROPMixtureBackend::set_REFPROP_fluids(const std::vector<std::string> &fluid_names)
{
    // If the name of the refrigerant doesn't match
    // that of the currently loaded refrigerant, fluids must be loaded
    if (!cached_component_string.empty() && LoadedREFPROPRef == cached_component_string)
    {
        if (CoolProp::get_debug_level() > 5){ std::cout << format("%s:%d: The current fluid can be reused; %s and %s match \n",__FILE__,__LINE__,cached_component_string.c_str(),LoadedREFPROPRef.c_str()); }
        if (dbg_refprop) std::cout << format("%s:%d: The current fluid can be reused; %s and %s match \n",__FILE__,__LINE__,cached_component_string.c_str(),LoadedREFPROPRef.c_str());
        int N = static_cast<int>(this->fluid_names.size());
        if (N > ncmax){
            throw ValueError(format("Size of fluid vector [%d] is larger than the maximum defined by REFPROP [%d]", fluid_names.size(), ncmax));
        }
        // this->Ncomp = N; ( this should not get set because it is already set and is always 1 for predefined mixtures )
        mole_fractions.resize(ncmax);
        mole_fractions_liq.resize(ncmax);
        mole_fractions_vap.resize(ncmax);
        return;
    }
    else
    {
        int ierr=0;
        this->fluid_names = fluid_names;
        char component_string[10000], herr[errormessagelength];
        std::string components_joined = strjoin(fluid_names,"|");
        std::string components_joined_raw = strjoin(fluid_names,"|");
        std::string fdPath = get_REFPROP_fluid_path_prefix();
        int N = static_cast<int>(fluid_names.size());

        // Get path to HMX.BNC file
        char hmx_bnc[255];
        const std::string HMX_path = get_REFPROP_HMX_BNC_path();
        const char * _HMX_path = HMX_path.c_str();
        if (strlen(_HMX_path) > refpropcharlength){
            throw ValueError(format("Full HMX path (%s) is too long; max length is 255 characters", _HMX_path));
        }
        strcpy(hmx_bnc, _HMX_path);

        if (get_config_bool(REFPROP_USE_GERG)) {
            int iflag = 1, // Tell REFPROP to use GERG04; 0 unsets GERG usage
                 ierr = 0;
            char herr[255];
            GERG04dll(&N, &iflag, &ierr, herr, 255);
        }

        // Check platform support
        if(!REFPROP_supported()){ throw NotImplementedError("You cannot use the REFPROPMixtureBackend."); }

        if (N == 1 && upper(components_joined_raw).find(".MIX") != std::string::npos){
            // It's a predefined mixture
            ierr = 0;
            std::vector<double> x(ncmax);
            char mix[255], reference_state[4] = "DEF";

            std::string path_to_MIX_file = join_path(get_REFPROP_mixtures_path_prefix(), components_joined_raw);
            const char * _components_joined_raw  = path_to_MIX_file.c_str();
            if (strlen(_components_joined_raw) > 255){ throw ValueError(format("components (%s) is too long", components_joined_raw.c_str())); }
            strcpy(mix, _components_joined_raw);

            SETMIXdll(mix,
                      hmx_bnc,
                      reference_state,
                      &N,
                      component_string,
                      &(x[0]),
                      &ierr,
                      herr,
                      255,
                      255,
                      3,
                      10000,
                      255);
            if (static_cast<int>(ierr) <= 0){
                this->Ncomp = N;
                mole_fractions.resize(ncmax);
                mole_fractions_liq.resize(ncmax);
                mole_fractions_vap.resize(ncmax);
                LoadedREFPROPRef = mix;
                cached_component_string = mix;
                this->fluid_names.clear();
                this->fluid_names.push_back(components_joined_raw);
                if (CoolProp::get_debug_level() > 5){ std::cout << format("%s:%d: Successfully loaded REFPROP fluid: %s\n",__FILE__,__LINE__, components_joined.c_str()); }
                if (dbg_refprop) std::cout << format("%s:%d: Successfully loaded REFPROP fluid: %s\n",__FILE__,__LINE__, components_joined.c_str());
                if (get_config_bool(REFPROP_DONT_ESTIMATE_INTERACTION_PARAMETERS) && ierr == -117){
                    throw ValueError(format("Interaction parameter estimation has been disabled: %s", herr));
                }
                set_mole_fractions(std::vector<CoolPropDbl>(x.begin(), x.begin()+N));
                if (get_config_bool(REFPROP_USE_PENGROBINSON)) {
                    int iflag = 2; // Tell REFPROP to use Peng-Robinson;
                    PREOSdll(&iflag);
                }
                else{
                    int iflag = 0; // Tell REFPROP to use normal Helmholtz models
                    PREOSdll(&iflag);
                }
                return;
            }
            else{
                throw ValueError(format("Unable to load mixture: %s",components_joined_raw.c_str()));
            }
        }

        // Loop over the file names - first we try with nothing, then .fld, then .FLD, then .ppf - means you can't mix and match
        for (unsigned int k = 0; k < number_of_endings; k++)
        {
            // Build the mixture string
            for (unsigned int j = 0; j < (unsigned int)N; j++)
            {
                if (j == 0){
                    components_joined = join_path(fdPath, upper(fluid_names[j]) + endings[k]);
                }
                else{
                    components_joined += "|" + join_path(fdPath, upper(fluid_names[j]) + endings[k]);
                }
            }

            if (dbg_refprop) std::cout << format("%s:%d: The fluid %s has not been loaded before, current value is %s \n",__FILE__,__LINE__,components_joined_raw.c_str(),LoadedREFPROPRef.c_str());

            // Copy over the list of components
            const char * _components_joined = components_joined.c_str();
            if (strlen(_components_joined) > 10000) { throw ValueError(format("components_joined (%s) is too long", _components_joined)); }
            strcpy(component_string, _components_joined);
            // Pad the fluid string all the way to 10k characters with spaces to deal with string parsing bug in REFPROP in SETUPdll
            for (int i = static_cast<int>(components_joined.size()); i < 10000; ++i){
                component_string[i] = ' ';
            }

            ierr = 0;
            //...Call SETUP to initialize the program
            SETUPdll(&N, component_string, hmx_bnc, default_reference_state,
                     &ierr, herr,
                     10000, // Length of component_string (see PASS_FTN.for from REFPROP)
                     refpropcharlength, // Length of path_HMX_BNC
                     lengthofreference, // Length of reference
                     errormessagelength // Length of error message
                     );
            if (get_config_bool(REFPROP_DONT_ESTIMATE_INTERACTION_PARAMETERS) && ierr == -117){
                throw ValueError(format("Interaction parameter estimation has been disabled: %s", herr));
            }
            if (get_config_bool(REFPROP_IGNORE_ERROR_ESTIMATED_INTERACTION_PARAMETERS) && ierr == 117) {
                ierr = 0;
            }
            if (static_cast<int>(ierr) <= 0) // Success (or a warning, which is silently squelched for now)
            {
                this->Ncomp = N;
                mole_fractions.resize(ncmax);
                mole_fractions_liq.resize(ncmax);
                mole_fractions_vap.resize(ncmax);
                LoadedREFPROPRef = _components_joined;
                cached_component_string = _components_joined;
                if (CoolProp::get_debug_level() > 5){ std::cout << format("%s:%d: Successfully loaded REFPROP fluid: %s\n",__FILE__,__LINE__, components_joined.c_str()); }
                if (dbg_refprop) std::cout << format("%s:%d: Successfully loaded REFPROP fluid: %s\n",__FILE__,__LINE__, components_joined.c_str());

                if (get_config_bool(REFPROP_USE_PENGROBINSON)) {
                    int iflag = 2; // Tell REFPROP to use Peng-Robinson;
                    PREOSdll(&iflag);
                }
                else{
                    int iflag = 0; // Tell REFPROP to use normal Helmholtz models
                    PREOSdll(&iflag);
                }
                return;
            }
            else if (k < number_of_endings-1){ // Keep going
                if (CoolProp::get_debug_level() > 5){std::cout << format("REFPROP error/warning [ierr: %d]: %s",ierr, herr) << std::endl;}
                continue;
            }
            else
            {
                if (CoolProp::get_debug_level() > 5){std::cout << format("k: %d #endings: %d", k, number_of_endings) << std::endl;}
                throw ValueError(format("Could not load these fluids: %s", components_joined_raw.c_str()));
            }
        }
    }
}
std::string REFPROPMixtureBackend::fluid_param_string(const std::string &ParamName){
    if (ParamName == "CAS"){
//        subroutine NAME (icomp,hnam,hn80,hcasn)
//        c
//        c  provides name information for specified component
//            c
//            c  input:
//            c    icomp--component number in mixture; 1 for pure fluid
//                c  outputs:
//                c     hnam--component name [character*12]
//                c     hn80--component name--long form [character*80]
//                c    hcasn--CAS (Chemical Abstracts Service) number [character*12]
        std::vector<std::string> CASvec;
        for (int icomp = 1L; icomp <= static_cast<int>(fluid_names.size()); ++icomp){
            char hnam[13], hn80[81], hcasn[13];
            NAMEdll(&icomp, hnam, hn80, hcasn, 12, 80, 12);
            hcasn[12]='\0';
            std::string casn = hcasn;
            strstrip(casn);
            CASvec.push_back(casn);
        }
        return strjoin(CASvec, "&");
    }
    else if (ParamName == "name"){
        int icomp = 1L;
        char hnam[13], hn80[81], hcasn[13];
        NAMEdll(&icomp, hnam, hn80, hcasn, 12, 80, 12);
        hnam[12] = '\0';
        std::string name = hnam;
        strstrip(name);
        return name;
    }
    else if (ParamName == "long_name"){
        int icomp = 1L;
        char hnam[13], hn80[81], hcasn[13];
        NAMEdll(&icomp, hnam, hn80, hcasn, 12, 80, 12);
        hn80[80] = '\0';
        std::string n80 = hn80;
        strstrip(n80);
        return n80;
    }
    else{
        throw ValueError(format("parameter to fluid_param_string is invalid: %s", ParamName.c_str()));
    }
};
int REFPROPMixtureBackend::match_CAS(const std::string &CAS){
    for (int icomp = 1L; icomp <= static_cast<int>(fluid_names.size()); ++icomp){
        char hnam[13], hn80[81], hcasn[13];
        NAMEdll(&icomp, hnam, hn80, hcasn, 12, 80, 12);
        hcasn[12] = '\0';
        std::string casn = hcasn;
        strstrip(casn);
        if (casn == CAS){
            return icomp;
        }
    }
    throw ValueError(format("Unable to match CAS number [%s]", CAS.c_str()));
}
/// Set binary mixture floating point parameter
void REFPROPMixtureBackend::set_binary_interaction_double(const std::string &CAS1, const std::string &CAS2, const std::string &parameter, const double value){
    std::size_t i = match_CAS(CAS1)-1, j = match_CAS(CAS2)-1;
    return set_binary_interaction_double(i, j, parameter, value);
};
/// Get binary mixture double value
double REFPROPMixtureBackend::get_binary_interaction_double(const std::string &CAS1, const std::string &CAS2, const std::string &parameter){
    std::size_t i = match_CAS(CAS1)-1, j = match_CAS(CAS2)-1;
    return get_binary_interaction_double(i, j, parameter);
}
/// Get binary mixture string value
std::string REFPROPMixtureBackend::get_binary_interaction_string(const std::string &CAS1, const std::string &CAS2, const std::string &parameter){

    int icomp, jcomp;
    char hmodij[4], hfmix[255], hbinp[255], hfij[255], hmxrul[255];
    double fij[6];

    icomp = match_CAS(CAS1);
    jcomp = match_CAS(CAS2);

    // Get the current state
    GETKTVdll(&icomp, &jcomp, hmodij, fij, hfmix, hfij, hbinp, hmxrul, 3, 255, 255, 255, 255);

    std::string shmodij(hmodij);
    if (shmodij.find("KW")==0 || shmodij.find("GE")==0)// Starts with KW or GE
    {
        if (parameter == "model"){
            return shmodij;
        }
        else {
            throw ValueError(format(" I don't know what to do with your parameter [%s]", parameter.c_str()));
            return "";
        }
    }
    else {
        //throw ValueError(format("For now, model [%s] must start with KW or GE", hmodij));
        return "";
    }
}
/// Set binary mixture string value
void REFPROPMixtureBackend::set_binary_interaction_string(const std::size_t i, const std::size_t j, const std::string &parameter, const std::string &value) {

    int icomp = static_cast<int>(i) + 1, jcomp = static_cast<int>(j) + 1, ierr = 0L;
    char hmodij[4], hfmix[255], hbinp[255], hfij[255], hmxrul[255];
    double fij[6];
    char herr[255];

    // Get the current state
    GETKTVdll(&icomp, &jcomp, hmodij, fij, hfmix, hfij, hbinp, hmxrul, 3, 255, 255, 255, 255);

    if (parameter == "model") {
        if (value.length()>4) {
            throw ValueError(format("Model parameter (%s) is longer than 4 characters.", value));
        } else {
            strcpy(hmodij, value.c_str());
        }
    }
    else {
        throw ValueError(format("I don't know what to do with your parameter [%s]", parameter.c_str()));
    }
    SETKTVdll(&icomp, &jcomp, hmodij, fij, hfmix, &ierr, herr, 3, 255, 255);
    if (ierr > 0L){
        throw ValueError(format("Unable to set parameter[%s] to value[%s]: %s",parameter.c_str(),value.c_str(),herr));
    }
}
/// Set binary mixture string parameter (EXPERT USE ONLY!!!)
void REFPROPMixtureBackend::set_binary_interaction_double(const std::size_t i, const std::size_t j, const std::string &parameter, const double value){
    int icomp = static_cast<int>(i)+1, jcomp = static_cast<int>(j)+1, ierr = 0L;
    char hmodij[4], hfmix[255], hbinp[255], hfij[255], hmxrul[255];
    double fij[6];
    char herr[255];

    // Get the prior state
    GETKTVdll(&icomp, &jcomp, hmodij, fij, hfmix, hfij, hbinp, hmxrul, 3, 255, 255, 255, 255);

    std::string shmodij(hmodij);
    if (shmodij.find("KW")==0 || shmodij.find("GE")==0)// Starts with KW or GE
    {
        if (parameter == "betaT"){ fij[0] = value;}
        else if (parameter == "gammaT"){ fij[1] = value; }
        else if (parameter == "betaV"){ fij[2] = value; }
        else if (parameter == "gammaV"){ fij[3] = value; }
        else if (parameter == "Fij"){ fij[4] = value; }
        else{
            throw ValueError(format("I don't know what to do with your parameter [%s]", parameter.c_str()));
        }
        SETKTVdll(&icomp, &jcomp, hmodij, fij, hfmix, &ierr, herr, 3, 255, 255);
        if (ierr > 0L){
            throw ValueError(format("Unable to set parameter[%s] to value[%g]: %s",parameter.c_str(),value,herr));
        }
    }
    else{
        throw ValueError(format("For now, model [%s] must start with KW or GE", hmodij));
    }
}

/// Get binary mixture double value (EXPERT USE ONLY!!!)
double REFPROPMixtureBackend::get_binary_interaction_double(const std::size_t i, const std::size_t j, const std::string &parameter){
    int icomp = static_cast<int>(i)+1, jcomp = static_cast<int>(j)+1;
    char hmodij[4], hfmix[255], hbinp[255], hfij[255], hmxrul[255];
    double fij[6];

    // Get the current state
    GETKTVdll(&icomp, &jcomp, hmodij, fij, hfmix, hfij, hbinp, hmxrul, 3, 255, 255, 255, 255);

    std::string shmodij(hmodij);
    if (shmodij.find("KW")==0 || shmodij.find("GE")==0)// Starts with KW or GE
    {
        double val;
        if (parameter == "betaT"){ val = fij[0];}
        else if (parameter == "gammaT"){ val = fij[1]; }
        else if (parameter == "betaV"){ val = fij[2]; }
        else if (parameter == "gammaV"){ val = fij[3]; }
        else if (parameter == "Fij"){ val = fij[4]; }
        else{
            throw ValueError(format(" I don't know what to do with your parameter [%s]", parameter.c_str()));
            return _HUGE;
        }
        return val;
    }
    else{
        //throw ValueError(format("For now, model [%s] must start with KW or GE", hmodij));
        return _HUGE;
    }
}
void REFPROPMixtureBackend::set_mole_fractions(const std::vector<CoolPropDbl> &mole_fractions)
{
    if (mole_fractions.size() != this->Ncomp)
    {
        throw ValueError(format("Size of mole fraction vector [%d] does not equal that of component vector [%d]", mole_fractions.size(), this->Ncomp));
    }
    this->mole_fractions = std::vector<CoolPropDbl>(ncmax, 0.0);
    for (std::size_t i = 0; i < mole_fractions.size(); ++i){
        this->mole_fractions[i] = static_cast<double>(mole_fractions[i]);
    }
    this->mole_fractions_long_double = mole_fractions; // same size as Ncomp
    _mole_fractions_set = true;
    clear_comp_change();
}
void REFPROPMixtureBackend::set_mass_fractions(const std::vector<CoolPropDbl> &mass_fractions)
{
    if (mass_fractions.size() != this->Ncomp)
    {
        throw ValueError(format("size of mass fraction vector [%d] does not equal that of component vector [%d]",mass_fractions.size(), this->Ncomp));
    }
    std::vector<double> moles(this->Ncomp);
    double sum_moles = 0.0;
    double wmm, ttrp, tnbpt, tc, pc, Dc, Zc, acf, dip, Rgas;
    for (int i = 1L; i <= static_cast<int>(this->Ncomp); ++i){
        INFOdll(&i, &wmm, &ttrp, &tnbpt, &tc, &pc, &Dc, &Zc, &acf, &dip, &Rgas);
        moles[i-1] = static_cast<double>(mass_fractions[i-1])/(wmm/1000.0);
		sum_moles += moles[i-1];
    }
    for (std::size_t i = 0; i < this->Ncomp; ++i){
        moles[i] = moles[i] / sum_moles;
    }
    this->set_mole_fractions(moles);
};
void REFPROPMixtureBackend::check_status(void)
{
    if (!_mole_fractions_set){ throw ValueError("Mole fractions not yet set");}
}

void REFPROPMixtureBackend::limits(double &Tmin, double &Tmax, double &rhomolarmax, double &pmax)
{
    /*
     *
          subroutine LIMITS (htyp,x,tmin,tmax,Dmax,pmax)
    c
    c  returns limits of a property model as a function of composition
    c
    c  Pure fluid limits are read in from the .fld files; for mixtures, a
    c  simple mole fraction weighting in reduced variables is used.
    c
    c  inputs:
    c     htyp--flag indicating which models are to be checked [character*3]
    c           'EOS':  equation of state for thermodynamic properties
    c           'ETA':  viscosity
    c           'TCX':  thermal conductivity
    c           'STN':  surface tension
    c        x--composition array [mol frac]
    c  outputs:
    c     tmin--minimum temperature for model specified by htyp [K]
    c     tmax--maximum temperature [K]
    c     Dmax--maximum density [mol/L]
    c     pmax--maximum pressure [kPa]
     *
     */
    this->check_loaded_fluid();
    double Dmax_mol_L,pmax_kPa;
    char htyp[] = "EOS";
    LIMITSdll(htyp, &(mole_fractions[0]), &Tmin, &Tmax, &Dmax_mol_L, &pmax_kPa, 3);
    pmax = pmax_kPa*1000;
    rhomolarmax = Dmax_mol_L*1000;
}
CoolPropDbl REFPROPMixtureBackend::calc_pmax(void){
    double Tmin, Tmax, rhomolarmax, pmax;
    limits(Tmin, Tmax, rhomolarmax, pmax);
    return static_cast<CoolPropDbl>(pmax);
};
CoolPropDbl REFPROPMixtureBackend::calc_Tmax(void){
    double Tmin, Tmax, rhomolarmax, pmax;
    limits(Tmin, Tmax, rhomolarmax, pmax);
    return static_cast<CoolPropDbl>(Tmax);
};
CoolPropDbl REFPROPMixtureBackend::calc_Tmin(void){
  double Tmin, Tmax, rhomolarmax, pmax;
  limits(Tmin, Tmax, rhomolarmax, pmax);
  return static_cast<CoolPropDbl>(Tmin);
};
CoolPropDbl REFPROPMixtureBackend::calc_T_critical(){
    this->check_loaded_fluid();
    int ierr = 0;
    char herr[255];
    double Tcrit, pcrit_kPa, dcrit_mol_L;
    CRITPdll(&(mole_fractions[0]),&Tcrit,&pcrit_kPa,&dcrit_mol_L,&ierr,herr,255);
    if (static_cast<int>(ierr) > 0) { throw ValueError(format("%s",herr).c_str()); } //else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
    return static_cast<CoolPropDbl>(Tcrit);
};
CoolPropDbl REFPROPMixtureBackend::calc_p_critical(){
    this->check_loaded_fluid();
    int ierr = 0;
    char herr[255];
    double Tcrit, pcrit_kPa, dcrit_mol_L;
    CRITPdll(&(mole_fractions[0]),&Tcrit,&pcrit_kPa,&dcrit_mol_L,&ierr,herr,255); if (static_cast<int>(ierr) > 0) { throw ValueError(format("%s",herr).c_str()); } //else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
    return static_cast<CoolPropDbl>(pcrit_kPa*1000);
};
CoolPropDbl REFPROPMixtureBackend::calc_rhomolar_critical(){
    int ierr = 0;
    char herr[255];
    double Tcrit, pcrit_kPa, dcrit_mol_L;
    CRITPdll(&(mole_fractions[0]),&Tcrit,&pcrit_kPa,&dcrit_mol_L,&ierr,herr,255); if (static_cast<int>(ierr) > 0) { throw ValueError(format("%s",herr).c_str()); } //else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
    return static_cast<CoolPropDbl>(dcrit_mol_L*1000);
};
void REFPROPMixtureBackend::calc_reducing_state(){
    this->check_loaded_fluid();
    double rhored_mol_L = 0, Tr = 0;
    REDXdll(&(mole_fractions[0]), &Tr, &rhored_mol_L);
    _reducing.T = Tr;
    _reducing.rhomolar = rhored_mol_L*1000;
}
CoolPropDbl REFPROPMixtureBackend::calc_T_reducing(){
    this->check_loaded_fluid();
    double rhored_mol_L = 0, Tr = 0;
    REDXdll(&(mole_fractions[0]), &Tr, &rhored_mol_L);
    return static_cast<CoolPropDbl>(Tr);
};
CoolPropDbl REFPROPMixtureBackend::calc_rhomolar_reducing(){
    this->check_loaded_fluid();
    double rhored_mol_L = 0, Tr = 0;
    REDXdll(&(mole_fractions[0]), &Tr, &rhored_mol_L);
    return static_cast<CoolPropDbl>(rhored_mol_L*1000);
};
CoolPropDbl REFPROPMixtureBackend::calc_acentric_factor(){
    //     subroutine INFO (icomp,wmm,ttrp,tnbpt,tc,pc,Dc,Zc,acf,dip,Rgas) (see calc_Ttriple())
    this->check_loaded_fluid();
    double wmm,ttrp,tnbpt,tc,pc,Dc,Zc,acf,dip,Rgas;
    int icomp = 1L;
    // Check if more than one
    if (Ncomp == 1){
        // Get value for first component
        INFOdll(&icomp,&wmm,&ttrp,&tnbpt,&tc,&pc,&Dc,&Zc,&acf,&dip,&Rgas);
        return static_cast<CoolPropDbl>(acf);
    }
    else{
        throw CoolProp::ValueError("acentric factor only available for pure components in REFPROP backend");
    }
};
CoolPropDbl REFPROPMixtureBackend::calc_Ttriple(){
//     subroutine INFO (icomp,wmm,ttrp,tnbpt,tc,pc,Dc,Zc,acf,dip,Rgas)
//     c
//     c  provides fluid constants for specified component
//     c
//     c  input:
//     c    icomp--component number in mixture; 1 for pure fluid
//     c  outputs:
//     c      wmm--molecular weight [g/mol]
//     c     ttrp--triple point temperature [K]
//     c    tnbpt--normal boiling point temperature [K]
//     c       tc--critical temperature [K]
//     c       pc--critical pressure [kPa]
//     c       Dc--critical density [mol/L]
//     c       Zc--compressibility at critical point [pc/(Rgas*Tc*Dc)]
//     c      acf--acentric factor [-]
//     c      dip--dipole moment [debye]
//     c     Rgas--gas constant [J/mol-K]
    this->check_loaded_fluid();
    double wmm,ttrp,tnbpt,tc,pc,Dc,Zc,acf,dip,Rgas;
    int icomp = 1L;
    // Check if more than one
    if (Ncomp == 1){
        // Get value for first component
        INFOdll(&icomp,&wmm,&ttrp,&tnbpt,&tc,&pc,&Dc,&Zc,&acf,&dip,&Rgas);
        return static_cast<CoolPropDbl>(ttrp);
    }
    else{
        double Tmin, Tmax, rhomolarmax, pmax;
        limits(Tmin, Tmax, rhomolarmax, pmax);
        return static_cast<CoolPropDbl>(Tmin);
    }
};
CoolPropDbl REFPROPMixtureBackend::calc_p_triple(){
    this->check_loaded_fluid();
    double p_kPa = _HUGE;
    double rho_mol_L=_HUGE, rhoLmol_L=_HUGE, rhoVmol_L=_HUGE,
    hmol=_HUGE,emol=_HUGE,smol=_HUGE,cvmol=_HUGE,cpmol=_HUGE,
    w=_HUGE;
    int ierr = 0;
    char herr[errormessagelength+1];
    int kq = 1;
    double __T = Ttriple(), __Q = 0;
    TQFLSHdll(&__T,&__Q,&(mole_fractions[0]),&kq,&p_kPa,&rho_mol_L,
                &rhoLmol_L,&rhoVmol_L,&(mole_fractions_liq[0]),&(mole_fractions_vap[0]), // Saturation terms
                &emol,&hmol,&smol,&cvmol,&cpmol,&w, // Other thermodynamic terms
                &ierr,herr,errormessagelength); // Error terms
    if (static_cast<int>(ierr) > 0) { throw ValueError(format("%s",herr).c_str()); }
    return p_kPa*1000;
};
CoolPropDbl REFPROPMixtureBackend::calc_dipole_moment(){
    //     subroutine INFO (icomp,wmm,ttrp,tnbpt,tc,pc,Dc,Zc,acf,dip,Rgas)
    //     c
    //     c  provides fluid constants for specified component
    //     c
    //     c  input:
    //     c    icomp--component number in mixture; 1 for pure fluid
    //     c  outputs:
    //     c      wmm--molecular weight [g/mol]
    //     c     ttrp--triple point temperature [K]
    //     c    tnbpt--normal boiling point temperature [K]
    //     c       tc--critical temperature [K]
    //     c       pc--critical pressure [kPa]
    //     c       Dc--critical density [mol/L]
    //     c       Zc--compressibility at critical point [pc/(Rgas*Tc*Dc)]
    //     c      acf--acentric factor [-]
    //     c      dip--dipole moment [debye]
    //     c     Rgas--gas constant [J/mol-K]
    this->check_loaded_fluid();
    double wmm,ttrp,tnbpt,tc,pc,Dc,Zc,acf,dip,Rgas;
    int icomp = 1L;
    // Check if more than one
    if (Ncomp == 1){
        // Get value for first component
        INFOdll(&icomp,&wmm,&ttrp,&tnbpt,&tc,&pc,&Dc,&Zc,&acf,&dip,&Rgas);
        return static_cast<CoolPropDbl>(dip*3.33564e-30);
    }
    else{
        throw ValueError(format("dipole moment is only available for pure fluids"));
    }
};
CoolPropDbl REFPROPMixtureBackend::calc_gas_constant(){
    this->check_loaded_fluid();
    double Rmix = 0;
    RMIX2dll(&(mole_fractions[0]), &Rmix);
    return static_cast<CoolPropDbl>(Rmix);
};
CoolPropDbl REFPROPMixtureBackend::calc_molar_mass(void)
{
    this->check_loaded_fluid();
    double wmm_kg_kmol;
    WMOLdll(&(mole_fractions[0]), &wmm_kg_kmol); // returns mole mass in kg/kmol
    _molar_mass = wmm_kg_kmol/1000; // kg/mol
    return static_cast<CoolPropDbl>(_molar_mass.pt());
};
CoolPropDbl REFPROPMixtureBackend::calc_Bvirial(void)
{
    double b;
    VIRBdll(&_T, &(mole_fractions[0]), &b);
    return b*0.001; // 0.001 to convert from l/mol to m^3/mol
}
CoolPropDbl REFPROPMixtureBackend::calc_Cvirial(void)
{
    double c;
    VIRCdll(&_T, &(mole_fractions[0]), &c);
    return c*1e-6; // 1e-6 to convert from (l/mol)^2 to (m^3/mol)^2
}
double REFPROPMixtureBackend::calc_melt_Tmax()
{
    this->check_loaded_fluid();
    int ierr = 0;
    char herr[255];
    double tmin,tmax,Dmax_mol_L,pmax_kPa, Tmax_melt;
    char htyp[] = "EOS";
    LIMITSdll(htyp, &(mole_fractions[0]), &tmin, &tmax, &Dmax_mol_L, &pmax_kPa, 3);
    // Get the maximum temperature for the melting curve by using the maximum pressure
    MELTPdll(&pmax_kPa, &(mole_fractions[0]),
             &Tmax_melt,
             &ierr,herr,errormessagelength);      // Error message
    if (static_cast<int>(ierr) > 0) { throw ValueError(format("%s",herr).c_str()); }
    //else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
    return Tmax_melt;
}
CoolPropDbl REFPROPMixtureBackend::calc_melting_line(int param, int given, CoolPropDbl value)
{
    this->check_loaded_fluid();
    int ierr = 0;
    char herr[255];

    if (param == iP && given == iT){
        double _T = static_cast<double>(value), p_kPa;
        MELTTdll(&_T, &(mole_fractions[0]),
             &p_kPa,
             &ierr,herr,errormessagelength);      // Error message
        if (static_cast<int>(ierr) > 0) { throw ValueError(format("%s",herr).c_str()); } //else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
        return p_kPa*1000;
    }
    else if (param == iT && given == iP){
        double p_kPa = static_cast<double>(value)/1000.0, _T;
        MELTPdll(&p_kPa, &(mole_fractions[0]),
             &_T,
             &ierr,herr,errormessagelength);      // Error message
        if (static_cast<int>(ierr) > 0) { throw ValueError(format("%s",herr).c_str()); } //else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
        return _T;
    }
    else{
        throw ValueError(format("calc_melting_line(%s,%s,%Lg) is an invalid set of inputs ",
                                get_parameter_information(param,"short").c_str(),
                                get_parameter_information(given,"short").c_str(),
                                value
                                )
                        );
    }
}
bool REFPROPMixtureBackend::has_melting_line(){
    this->check_loaded_fluid();

    int ierr = 0;
    char herr[255];
    double _T = 300, p_kPa;
    MELTTdll(&_T, &(mole_fractions[0]),
             &p_kPa,
             &ierr,herr,errormessagelength);      // Error message
    if (static_cast<int>(ierr) == 1) { return false; }
    else{ return true; }
}

const std::vector<CoolPropDbl> REFPROPMixtureBackend::calc_mass_fractions()
{
    // mass fraction is mass_i/total_mass;
    // REFPROP yields mm in kg/kmol, CP uses base SI units of kg/mol;
    CoolPropDbl mm = molar_mass();
    std::vector<CoolPropDbl> mass_fractions(mole_fractions_long_double.size());
    double wmm, ttrp, tnbpt, tc, pc, Dc, Zc, acf, dip, Rgas;
    // FORTRAN is 1-based indexing!
    for (int i = 1L; i <= static_cast<int>(mole_fractions_long_double.size()); ++i){
        // Get value for first component
        INFOdll(&i, &wmm, &ttrp, &tnbpt, &tc, &pc, &Dc, &Zc, &acf, &dip, &Rgas);
        mass_fractions[i - 1] = (wmm / 1000.0)*mole_fractions_long_double[i - 1] / mm;
    }
    return mass_fractions;
}

CoolPropDbl REFPROPMixtureBackend::calc_PIP(void)
{
    // Calculate the PIP factor of Venkatharathnam and Oellrich, "Identification of the phase of a fluid using
    // partial derivatives of pressure, volume,and temperature without reference to saturation properties:
    // Applications in phase equilibria calculations"
    double t = _T, rho = _rhomolar/1000.0, // mol/dm^3
        p = 0,e = 0,h = 0,s = 0,cv = 0,cp = 0,w = 0,Z = 0,hjt = 0,A = 0,G = 0,
        xkappa = 0,beta = 0,dPdrho = 0,d2PdD2 = 0,dPT = 0,drhodT = 0,drhodP = 0,
        d2PT2 = 0,d2PdTD = 0,spare3 = 0,spare4 = 0;
    //subroutine THERM2 (t,rho,x,p,e,h,s,cv,cp,w,Z,hjt,A,G,
    // &                   xkappa,beta,dPdrho,d2PdD2,dPT,drhodT,drhodP,
    // &                   d2PT2,d2PdTD,spare3,spare4);
    THERM2dll(&t,&rho,&(mole_fractions[0]),&p,&e,&h,&s,&cv,&cp,&w,&Z,&hjt,&A,&G, &xkappa,&beta,&dPdrho,&d2PdD2,&dPT,&drhodT,&drhodP,&d2PT2,&d2PdTD,&spare3,&spare4);
    return 2-rho*(d2PdTD/dPT- d2PdD2/dPdrho);
};

CoolPropDbl REFPROPMixtureBackend::calc_viscosity(void)
{
    this->check_loaded_fluid();
    double eta, tcx, rhomol_L = 0.001*_rhomolar;
    int ierr = 0;
    char herr[255];
    TRNPRPdll(&_T,&rhomol_L,&(mole_fractions[0]),  // Inputs
              &eta,&tcx,                           // Outputs
              &ierr,herr,errormessagelength);      // Error message
    if (static_cast<int>(ierr) > 0) { throw ValueError(format("%s",herr).c_str()); }
    //else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
    _viscosity = 1e-6*eta;
    _conductivity = tcx;
    return static_cast<double>(_viscosity);
}
CoolPropDbl REFPROPMixtureBackend::calc_conductivity(void)
{
    // Calling viscosity also caches conductivity, use that to save calls
    calc_viscosity();
    return static_cast<double>(_conductivity);
}
CoolPropDbl REFPROPMixtureBackend::calc_surface_tension(void)
{
    this->check_loaded_fluid();
    double sigma, rho_mol_L = 0.001*_rhomolar;
    int ierr = 0;
    char herr[255];
    SURFTdll(&_T, &rho_mol_L, &(mole_fractions[0]),  // Inputs
             &sigma,                                 // Outputs
             &ierr, herr, errormessagelength);       // Error message
    if (static_cast<int>(ierr) > 0) { throw ValueError(format("%s",herr).c_str()); }
    //else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
    _surface_tension = sigma;
    return static_cast<double>(_surface_tension);
}
CoolPropDbl REFPROPMixtureBackend::calc_fugacity_coefficient(std::size_t i)
{
    this->check_loaded_fluid();
    double rho_mol_L = 0.001*_rhomolar;
    int ierr = 0;
    std::vector<double> fug_cof;
    fug_cof.resize(mole_fractions.size());
    char herr[255];
    FUGCOFdll(&_T, &rho_mol_L, &(mole_fractions[0]),  // Inputs
             &(fug_cof[0]),                           // Outputs
             &ierr, herr, errormessagelength);        // Error message
    if (static_cast<int>(ierr) > 0) { throw ValueError(format("%s",herr).c_str()); }
    //else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
    return static_cast<CoolPropDbl>(fug_cof[i]);
}
CoolPropDbl REFPROPMixtureBackend::calc_fugacity(std::size_t i)
{
    this->check_loaded_fluid();
    double rho_mol_L = 0.001*_rhomolar;
    int ierr = 0;
    std::vector<double> f(mole_fractions.size());
    char herr[255];
    FGCTY2dll(&_T, &rho_mol_L, &(mole_fractions[0]),  // Inputs
              &(f[0]),                                // Outputs
        &ierr, herr, errormessagelength);             // Error message
    if (static_cast<int>(ierr) > 0) { throw ValueError(format("%s", herr).c_str()); }
    //else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
    return static_cast<CoolPropDbl>(f[i]*1000);
}
CoolPropDbl REFPROPMixtureBackend::calc_chemical_potential(std::size_t i)
{
    this->check_loaded_fluid();
    double rho_mol_L = 0.001*_rhomolar;
    int ierr = 0;
    std::vector<double> chem_pot(mole_fractions.size());
    char herr[255];
    CHEMPOTdll(&_T, &rho_mol_L, &(mole_fractions[0]),  // Inputs
        &(chem_pot[0]),                           // Outputs
        &ierr, herr, errormessagelength);        // Error message
    if (static_cast<int>(ierr) > 0) { throw ValueError(format("%s", herr).c_str()); }
    //else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
    return static_cast<CoolPropDbl>(chem_pot[i]);
}

void REFPROPMixtureBackend::calc_phase_envelope(const std::string &type)
{
    this->check_loaded_fluid();
    double rhoymin, rhoymax, c = 0;
    int ierr = 0;
    char herr[255];
    SATSPLNdll(&(mole_fractions[0]),  // Inputs
               &ierr, herr, errormessagelength);       // Error message
    if (static_cast<int>(ierr) > 0) { throw ValueError(format("%s",herr).c_str()); }

    // Clear the phase envelope data
    PhaseEnvelope = PhaseEnvelopeData();
    /*
    subroutine SPLNVAL (isp,iderv,a,f,ierr,herr)
    c
    c  calculates the function value of a spline
    c
    c  inputs:
    c      isp--indicator for which spline to use (1-nc: composition,
    c           nc+1: temperature, nc+2: pressure, nc+3: density,
    c           nc+4: enthalpy, nc+5: entropy)
    c    iderv--values of -1 and -2 return lower and upper root values,
    c           value of 0 returns spline function, value of 1 returns
    c           derivative of spline function with respect to density
    c        a--root value
    c  outputs:
    c        f--value of spline function at input root
    c     ierr--error flag:   0 = successful
    c     herr--error string (character*255)
    */
    int N = 500;
    int isp = 0, iderv = -1;
    if (SPLNVALdll==NULL){
        std::string rpv = get_global_param_string("REFPROP_version");
        throw ValueError(format("Your version of REFFPROP(%s) does not have the SPLNVALdll function; cannot extract phase envelope values",rpv.c_str()));
    };
    SPLNVALdll(&isp, &iderv, &c, &rhoymin, &ierr, herr, errormessagelength);
    iderv = -2;
    SPLNVALdll(&isp, &iderv, &c, &rhoymax, &ierr, herr, errormessagelength);
    int nc = this->Ncomp;
    double ratio = pow(rhoymax/rhoymin,1/double(N));
    for (double rho_molL = rhoymin; rho_molL < rhoymax; rho_molL *= ratio)
    {
        double y; iderv = 0;

        PhaseEnvelope.x.resize(nc);
        PhaseEnvelope.y.resize(nc);
        for (isp = 1; isp <= nc; ++isp){
            SPLNVALdll(&isp, &iderv, &rho_molL, &y, &ierr, herr, errormessagelength);
            PhaseEnvelope.x[isp-1].push_back(y);
            PhaseEnvelope.y[isp-1].push_back(get_mole_fractions()[isp-1]);
        }

        PhaseEnvelope.rhomolar_vap.push_back(rho_molL*1000);
        PhaseEnvelope.lnrhomolar_vap.push_back(log(rho_molL*1000));
        isp = nc + 1;
        SPLNVALdll(&isp, &iderv, &rho_molL, &y, &ierr, herr, errormessagelength);
        double T = y;
        PhaseEnvelope.T.push_back(y);
        PhaseEnvelope.lnT.push_back(log(y));
        isp = nc + 2;
        SPLNVALdll(&isp, &iderv, &rho_molL, &y, &ierr, herr, errormessagelength);
        PhaseEnvelope.p.push_back(y*1000);
        PhaseEnvelope.lnp.push_back(log(y*1000));
        isp = nc + 3;
        SPLNVALdll(&isp, &iderv, &rho_molL, &y, &ierr, herr, errormessagelength);
        PhaseEnvelope.rhomolar_liq.push_back(y*1000);
        PhaseEnvelope.lnrhomolar_liq.push_back(log(y*1000));
        PhaseEnvelope.Q.push_back(static_cast<double>(y > rho_molL));
        isp = nc + 4;
        SPLNVALdll(&isp, &iderv, &rho_molL, &y, &ierr, herr, errormessagelength);
        PhaseEnvelope.hmolar_vap.push_back(y);
        isp = nc + 5;
        SPLNVALdll(&isp, &iderv, &rho_molL, &y, &ierr, herr, errormessagelength);
        PhaseEnvelope.smolar_vap.push_back(y);

        // Other outputs that could be useful
        int ierr = 0;
        char herr[255];
        double p_kPa, emol, hmol, smol, cvmol, cpmol, w, hjt, eta, tcx;
        // "Vapor"
        THERMdll(&T, &rho_molL, &(mole_fractions[0]), &p_kPa, &emol, &hmol, &smol, &cvmol, &cpmol, &w, &hjt);
        PhaseEnvelope.cpmolar_vap.push_back(cpmol);
        PhaseEnvelope.cvmolar_vap.push_back(cvmol);
        PhaseEnvelope.speed_sound_vap.push_back(w);
        TRNPRPdll(&T, &rho_molL, &(mole_fractions[0]),   // Inputs
            &eta, &tcx,                                  // Outputs
            &ierr, herr, errormessagelength);            // Error message
        PhaseEnvelope.viscosity_vap.push_back(eta/1e6);
        PhaseEnvelope.conductivity_vap.push_back(tcx);
    }
}
CoolPropDbl REFPROPMixtureBackend::calc_cpmolar_idealgas(void)
{
    this->check_loaded_fluid();
    double rho_mol_L = 0.001*_rhomolar;
    double p0, e0, h0, s0, cv0, cp0, w0, A0, G0;
    THERM0dll(&_T,&rho_mol_L,&(mole_fractions[0]),&p0,&e0,&h0,&s0,&cv0,&cp0,&w0,&A0,&G0);
    return static_cast<CoolPropDbl>(cp0);
}

phases REFPROPMixtureBackend::GetRPphase()
{
    phases RPphase = iphase_unknown;
    if (ValidNumber(_Q))
    {
        if ((_Q >= 0.00) && (_Q <= 1.00)) {      // CoolProp includes Q = 1 or 0 in the two phase region,
            RPphase = iphase_twophase;            // whereas RefProp designates saturated liquid and saturated vapor.
        }
        else if (_Q > 1.00) {                    // Above saturation curve
            RPphase = iphase_gas;
            if (_T >= calc_T_critical()) {       //     ....AND T >= Tcrit
                RPphase = iphase_supercritical_gas;
            }
        }
        else if (_Q < 0.00) {                    // Below saturation curve
            RPphase = iphase_liquid;
            if (_p >= calc_p_critical()) {       //     ....AND P >= Pcrit
                RPphase = iphase_supercritical_liquid;
            }
        }
        else {                                   // RefProp might return Q = 920 for Metastable
            RPphase = iphase_unknown;             // but CoolProp doesn't have an enumerator for this state,
        }                                        // so it's unknown as well.

        if ((_Q == 999) || (_Q == -997)) {       // One last check for _Q == 999||-997 (Supercritical)
            RPphase = iphase_supercritical;       // T >= Tcrit AND P >= Pcrit
            if ((std::abs(_T - calc_T_critical()) < 10 * DBL_EPSILON) &&   // IF (T == Tcrit) AND
                (std::abs(_p - calc_p_critical()) < 10 * DBL_EPSILON)) {   //    (P == Pcrit) THEN
                RPphase = iphase_critical_point;                            //    at critical point. 
            };
        }
    }
    else {
            RPphase = iphase_unknown;
    }
    return RPphase;
}

void REFPROPMixtureBackend::update(CoolProp::input_pairs input_pair, double value1, double value2)
{
    this->check_loaded_fluid();
    double rho_mol_L=_HUGE, rhoLmol_L=_HUGE, rhoVmol_L=_HUGE,
        hmol=_HUGE,emol=_HUGE,smol=_HUGE,cvmol=_HUGE,cpmol=_HUGE,
        w=_HUGE,q=_HUGE, mm=_HUGE, p_kPa = _HUGE, hjt = _HUGE;
    int ierr = 0;
    char herr[errormessagelength+1] = " ";

    clear();

    // Check that mole fractions have been set, etc.
    check_status();

    // Get the molar mass of the fluid for the given composition
    WMOLdll(&(mole_fractions[0]), &mm); // returns mole mass in kg/kmol
    _molar_mass = 0.001*mm; // [kg/mol]

    switch(input_pair)
    {
        case PT_INPUTS:
        {
            // Unit conversion for REFPROP
            p_kPa = 0.001*value1; _T = value2; // Want p in [kPa] in REFPROP

            if (imposed_phase_index == iphase_not_imposed){
                // Use flash routine to find properties
                TPFLSHdll(&_T,&p_kPa,&(mole_fractions[0]),&rho_mol_L,
                          &rhoLmol_L,&rhoVmol_L,&(mole_fractions_liq[0]),&(mole_fractions_vap[0]), // Saturation terms
                          &q,&emol,&hmol,&smol,&cvmol,&cpmol,&w,
                          &ierr,herr,errormessagelength); //
                if (static_cast<int>(ierr) > 0) {
                    throw ValueError(format("PT: %s",herr).c_str());
                }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
            }
            else{
                //c  inputs:
                //c        t--temperature [K]
                //c        p--pressure [kPa]
                //c        x--composition [array of mol frac]
                //c      kph--phase flag:  1 = liquid
                //c                        2 = vapor
                //c                 N.B.:  0 = stable phase--NOT ALLOWED (use TPFLSH)
                //c                            (unless an initial guess is supplied for rho)
                //c                       -1 = force the search in the liquid phase (for metastable points)
                //c                       -2 = force the search in the vapor phase (for metastable points)
                //c   kguess--input flag:  1 = first guess for rho provided
                //c                        0 = no first guess provided
                //c      rho--first guess for molar density [mol/L], only if kguess = 1
                //c
                //c  outputs:
                //c      rho--molar density [mol/L]
                //c     ierr--error flag:  0 = successful
                //c                      200 = CRITP did not converge
                //c                      201 = illegal input (kph <= 0)
                //c                      202 = liquid-phase iteration did not converge
                //c                      203 = vapor-phase iteration did not converge
                //c     herr--error string (character*255 variable if ierr<>0)
                int kph = -10, kguess = 0;
                if (imposed_phase_index == iphase_liquid || imposed_phase_index == iphase_supercritical_liquid){
                    kph = 1;
                }
                else if (imposed_phase_index == iphase_gas || imposed_phase_index == iphase_supercritical_gas){
                    kph = 2;
                }
                else{
                    throw ValueError(format("PT: cannot use this imposed phase for PT inputs"));
                }
                // Calculate rho from TP
                TPRHOdll(&_T,&p_kPa,&(mole_fractions[0]),&kph,&kguess,
                         &rho_mol_L,
                         &ierr,herr,errormessagelength);

                // Calculate everything else
                THERMdll(&_T, &rho_mol_L, &(mole_fractions[0]), &p_kPa, &emol, &hmol, &smol, &cvmol, &cpmol, &w, &hjt);

            }

            // Set all cache values that can be set with unit conversion to SI
            _p = value1;
            _rhomolar = rho_mol_L*1000;  // 1000 for conversion from mol/L to mol/m3
            _rhoLmolar = rhoLmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            _rhoVmolar = rhoVmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            break;
        }
        case DmolarT_INPUTS:
        {
            // Unit conversion for REFPROP
            _rhomolar = value1; rho_mol_L = 0.001*value1; _T = value2; // Want rho in [mol/L] in REFPROP

            if (imposed_phase_index == iphase_not_imposed || imposed_phase_index == iphase_twophase) {
                // Use flash routine to find properties
                TDFLSHdll(&_T,&rho_mol_L,&(mole_fractions[0]),&p_kPa,
                          &rhoLmol_L,&rhoVmol_L,&(mole_fractions_liq[0]),&(mole_fractions_vap[0]), // Saturation terms
                          &q,&emol,&hmol,&smol,&cvmol,&cpmol,&w,
                          &ierr,herr,errormessagelength);
                if (static_cast<int>(ierr) > 0) { throw ValueError(format("DmolarT: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
            }
            else{
                // phase is imposed
                // Calculate everything else
                THERMdll(&_T, &rho_mol_L, &(mole_fractions[0]), &p_kPa, &emol, &hmol, &smol, &cvmol, &cpmol, &w, &hjt);
            }

            // Set all cache values that can be set with unit conversion to SI
            _p = p_kPa * 1000;
            _rhoLmolar = rhoLmol_L * 1000; // 1000 for conversion from mol/L to mol/m3
            _rhoVmolar = rhoVmol_L * 1000; // 1000 for conversion from mol/L to mol/m3
            break;
        }
        case DmassT_INPUTS:
        {
            // Call again, but this time with molar units
            // D: [kg/m^3] / [kg/mol] -> [mol/m^3]
            update(DmolarT_INPUTS, value1 / (double)_molar_mass, value2);
            return;
        }
        case DmolarP_INPUTS:
        {
            // Unit conversion for REFPROP
            rho_mol_L = 0.001*value1; p_kPa = 0.001*value2; // Want p in [kPa] in REFPROP

            // Use flash routine to find properties
            // from REFPROP: subroutine PDFLSH (p,D,z,t,Dl,Dv,x,y,q,e,h,s,cv,cp,w,ierr,herr)
            PDFLSHdll(&p_kPa,&rho_mol_L,&(mole_fractions[0]),&_T,
                &rhoLmol_L,&rhoVmol_L,&(mole_fractions_liq[0]),&(mole_fractions_vap[0]), // Saturation terms
                &q,&emol,&hmol,&smol,&cvmol,&cpmol,&w, // Other thermodynamic terms
                &ierr,herr,errormessagelength);  // Error terms
            if (static_cast<int>(ierr) > 0) { throw ValueError(format("DmolarP: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}

            // Set all cache values that can be set with unit conversion to SI
            _rhomolar = value1;
            _p = value2;
            _rhoLmolar = rhoLmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            _rhoVmolar = rhoVmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            break;
        }
        case DmassP_INPUTS:
        {
            // Call again, but this time with molar units
            // D: [kg/m^3] / [kg/mol] -> [mol/m^3]
            update(DmolarP_INPUTS, value1 / (double)_molar_mass, value2);
            return;
        }
        case DmolarHmolar_INPUTS:
        {
            // Unit conversion for REFPROP
            _rhomolar = value1; rho_mol_L = 0.001*value1; hmol = value2; // Want rho in [mol/L] in REFPROP

            // Use flash routine to find properties
            // from REFPROP: subroutine DHFLSH (D,h,z,t,p,Dl,Dv,x,y,q,e,s,cv,cp,w,ierr,herr)
            DHFLSHdll(&rho_mol_L,&hmol,&(mole_fractions[0]),&_T,&p_kPa,
                      &rhoLmol_L,&rhoVmol_L,&(mole_fractions_liq[0]),&(mole_fractions_vap[0]), // Saturation terms
                      &q,&emol,&smol,&cvmol,&cpmol,&w,
                      &ierr,herr,errormessagelength);
            if (static_cast<int>(ierr) > 0) { throw ValueError(format("DmolarHmolar: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}

            // Set all cache values that can be set with unit conversion to SI
            _p = p_kPa*1000;
            _rhoLmolar = rhoLmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            _rhoVmolar = rhoVmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            break;
        }
        case DmassHmass_INPUTS:
        {
            // Call again, but this time with molar units
            // D: [kg/m^3] / [kg/mol] -> [mol/m^3]
            // H: [J/kg] * [kg/mol] -> [J/mol]
            update(DmolarHmolar_INPUTS, value1 / (double)_molar_mass, value2 * (double)_molar_mass);
            return;
        }
        case DmolarSmolar_INPUTS:
        {
            // Unit conversion for REFPROP
            _rhomolar = value1; rho_mol_L = 0.001*value1; smol = value2; // Want rho in [mol/L] in REFPROP

            // Use flash routine to find properties
            // from REFPROP: subroutine DSFLSH (D,s,z,t,p,Dl,Dv,x,y,q,e,h,cv,cp,w,ierr,herr)
            DSFLSHdll(&rho_mol_L,&smol,&(mole_fractions[0]),&_T,&p_kPa,
                      &rhoLmol_L,&rhoVmol_L,&(mole_fractions_liq[0]),&(mole_fractions_vap[0]), // Saturation terms
                      &q,&emol,&hmol,&cvmol,&cpmol,&w,
                      &ierr,herr,errormessagelength);
            if (static_cast<int>(ierr) > 0) { throw ValueError(format("DmolarSmolar: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}

            // Set all cache values that can be set with unit conversion to SI
            _p = p_kPa*1000;
            _rhoLmolar = rhoLmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            _rhoVmolar = rhoVmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            break;
        }
        case DmassSmass_INPUTS:
        {
            // Call again, but this time with molar units
            // D: [kg/m^3] / [kg/mol] -> [mol/m^3]
            // S: [J/kg/K] * [kg/mol] -> [J/mol/K]
            update(DmolarSmolar_INPUTS, value1 / (double)_molar_mass, value2 * (double)_molar_mass );
            return;
        }
        case DmolarUmolar_INPUTS:
        {
            // Unit conversion for REFPROP
            _rhomolar = value1; rho_mol_L = 0.001*value1; emol = value2; // Want rho in [mol/L] in REFPROP

            // Use flash routine to find properties
            // from REFPROP: subroutine DEFLSH (D,e,z,t,p,Dl,Dv,x,y,q,h,s,cv,cp,w,ierr,herr)
            DEFLSHdll(&rho_mol_L,&emol,&(mole_fractions[0]),&_T,&p_kPa,
                      &rhoLmol_L,&rhoVmol_L,&(mole_fractions_liq[0]),&(mole_fractions_vap[0]), // Saturation terms
                      &q,&hmol,&hmol,&cvmol,&cpmol,&w,
                      &ierr,herr,errormessagelength);
            if (static_cast<int>(ierr) > 0) { throw ValueError(format("DmolarUmolar: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}

            // Set all cache values that can be set with unit conversion to SI
            _p = p_kPa*1000;
            if (0)
            _rhoLmolar = rhoLmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            _rhoVmolar = rhoVmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            break;
        }
        case DmassUmass_INPUTS:
        {
            // Call again, but this time with molar units
            // D: [kg/m^3] / [kg/mol] -> [mol/m^3]
            // U: [J/mol] * [kg/mol] -> [J/mol]
            update(DmolarUmolar_INPUTS, value1 / (double)_molar_mass, value2 * (double)_molar_mass);
            return;
        }
        case HmolarP_INPUTS:
        {
            // Unit conversion for REFPROP
            hmol = value1; p_kPa = 0.001*value2; // Want p in [kPa] in REFPROP

            // Use flash routine to find properties
            PHFLSHdll(&p_kPa,&hmol,&(mole_fractions[0]),&_T,&rho_mol_L,
                &rhoLmol_L,&rhoVmol_L,&(mole_fractions_liq[0]),&(mole_fractions_vap[0]), // Saturation terms
                &q,&emol,&smol,&cvmol,&cpmol,&w, // Other thermodynamic terms
                &ierr,herr,errormessagelength); // Error terms
            if (static_cast<int>(ierr) > 0) { throw ValueError(format("HmolarPmolar: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}

            // Set all cache values that can be set with unit conversion to SI
            _p = value2;
            _rhomolar = rho_mol_L*1000; // 1000 for conversion from mol/L to mol/m3
            _rhoLmolar = rhoLmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            _rhoVmolar = rhoVmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            break;
        }
        case HmassP_INPUTS:
        {
            // Call again, but this time with molar units
            // H: [J/kg] * [kg/mol] -> [J/mol]
            update(HmolarP_INPUTS, value1 * (double)_molar_mass, value2);
            return;
        }
        case PSmolar_INPUTS:
        {
            // Unit conversion for REFPROP
            p_kPa = 0.001*value1; smol = value2; // Want p in [kPa] in REFPROP

            // Use flash routine to find properties
            PSFLSHdll(&p_kPa,&smol,&(mole_fractions[0]),&_T,&rho_mol_L,
                &rhoLmol_L,&rhoVmol_L,&(mole_fractions_liq[0]),&(mole_fractions_vap[0]), // Saturation terms
                &q,&emol,&hmol,&cvmol,&cpmol,&w, // Other thermodynamic terms
                &ierr,herr,errormessagelength); // Error terms

            if (static_cast<int>(ierr) > 0) { throw ValueError(format("PSmolar: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}

            // Set all cache values that can be set with unit conversion to SI
            _p = value1;
            _rhomolar = rho_mol_L*1000; // 1000 for conversion from mol/L to mol/m3
            _rhoLmolar = rhoLmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            _rhoVmolar = rhoVmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            break;
        }
        case PSmass_INPUTS:
        {
            // Call again, but this time with molar units
            // S: [J/kg/K] * [kg/mol] -> [J/mol/K]
            update(PSmolar_INPUTS, value1, value2*(double)_molar_mass);
            return;
        }
        case PUmolar_INPUTS:
        {
            // Unit conversion for REFPROP
            p_kPa = 0.001*value1; emol = value2; // Want p in [kPa] in REFPROP

            // Use flash routine to find properties
            // from REFPROP: subroutine PEFLSH (p,e,z,t,D,Dl,Dv,x,y,q,h,s,cv,cp,w,ierr,herr)
            PEFLSHdll(&p_kPa,&emol,&(mole_fractions[0]),&_T,&rho_mol_L,
                &rhoLmol_L,&rhoVmol_L,&(mole_fractions_liq[0]),&(mole_fractions_vap[0]), // Saturation terms
                &q,&hmol,&smol,&cvmol,&cpmol,&w, // Other thermodynamic terms
                &ierr,herr,errormessagelength); // Error terms

            if (static_cast<int>(ierr) > 0) { throw ValueError(format("PUmolar: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}

            // Set all cache values that can be set with unit conversion to SI
            _p = value1;
            _rhomolar = rho_mol_L*1000; // 1000 for conversion from mol/L to mol/m3
            _rhoLmolar = rhoLmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            _rhoVmolar = rhoVmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            break;
        }
        case PUmass_INPUTS:
        {
            // Call again, but this time with molar units
            // U: [J/kg] * [kg/mol] -> [J/mol]
            update(PUmolar_INPUTS, value1, value2*(double)_molar_mass);
            return;
        }
        case HmolarSmolar_INPUTS:
        {
            // Unit conversion for REFPROP
            hmol = value1; smol = value2;

            HSFLSHdll(&hmol,&smol,&(mole_fractions[0]),&_T,&p_kPa,&rho_mol_L,
                &rhoLmol_L,&rhoVmol_L,&(mole_fractions_liq[0]),&(mole_fractions_vap[0]), // Saturation terms
                &q,&emol,&cvmol,&cpmol,&w, // Other thermodynamic terms
                &ierr,herr,errormessagelength); // Error terms

            if (static_cast<int>(ierr) > 0) { throw ValueError(format("HmolarSmolar: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}

            // Set all cache values that can be set with unit conversion to SI
            _p = p_kPa*1000; // 1000 for conversion from kPa to Pa
            _rhomolar = rho_mol_L*1000; // 1000 for conversion from mol/L to mol/m3
            _rhoLmolar = rhoLmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            _rhoVmolar = rhoVmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            break;
        }
        case HmassSmass_INPUTS:
        {
            // Call again, but this time with molar units
            // H: [J/kg] * [kg/mol] -> [J/mol/K]
            // S: [J/kg/K] * [kg/mol] -> [J/mol/K]
            update(HmolarSmolar_INPUTS, value1 * (double)_molar_mass, value2 * (double)_molar_mass);
            return;
        }
        case SmolarUmolar_INPUTS:
        {
            // Unit conversion for REFPROP
            smol = value1; emol = value2;

            // from REFPROP: subroutine ESFLSH (e,s,z,t,p,D,Dl,Dv,x,y,q,h,cv,cp,w,ierr,herr)
            ESFLSHdll(&emol,&smol,&(mole_fractions[0]),&_T,&p_kPa,&rho_mol_L,
                &rhoLmol_L,&rhoVmol_L,&(mole_fractions_liq[0]),&(mole_fractions_vap[0]), // Saturation terms
                &q,&smol,&cvmol,&cpmol,&w, // Other thermodynamic terms
                &ierr,herr,errormessagelength); // Error terms

            if (static_cast<int>(ierr) > 0) { throw ValueError(format("SmolarUmolar: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}

            // Set all cache values that can be set with unit conversion to SI
            _p = p_kPa*1000; // 1000 for conversion from kPa to Pa
            _rhomolar = rho_mol_L*1000; // 1000 for conversion from mol/L to mol/m3
            _rhoLmolar = rhoLmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            _rhoVmolar = rhoVmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            break;
        }
        case SmassUmass_INPUTS:
        {
            // Call again, but this time with molar units
            // S: [J/kg/K] * [kg/mol] -> [J/mol/K],
            // U: [J/kg] * [kg/mol] -> [J/mol]
            update(SmolarUmolar_INPUTS, value1 * (double)_molar_mass, value2 * (double)_molar_mass);
            return;
        }
        case SmolarT_INPUTS:
        {
            // Unit conversion for REFPROP
            smol = value1; _T = value2;

            /*
            c  additional input--only for THFLSH, TSFLSH, and TEFLSH
            c       kr--flag specifying desired root for multi-valued inputs:
            c           1 = return lower density root
            c           2 = return higher density root
            */
            int kr = 1;

            // from REFPROP: subroutine TSFLSH (t,s,z,kr,p,D,Dl,Dv,x,y,q,e,h,cv,cp,w,ierr,herr)
            TSFLSHdll(&_T,&smol,&(mole_fractions[0]),&kr,&p_kPa,&rho_mol_L,
                &rhoLmol_L,&rhoVmol_L,&(mole_fractions_liq[0]),&(mole_fractions_vap[0]), // Saturation terms
                &q,&emol,&hmol,&cvmol,&cpmol,&w, // Other thermodynamic terms
                &ierr,herr,errormessagelength); // Error terms

            if (static_cast<int>(ierr) > 0) { throw ValueError(format("SmolarT: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}

            // Set all cache values that can be set with unit conversion to SI
            _p = p_kPa*1000; // 1000 for conversion from kPa to Pa
            _rhomolar = rho_mol_L*1000; // 1000 for conversion from mol/L to mol/m3
            _rhoLmolar = rhoLmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            _rhoVmolar = rhoVmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            break;
        }
        case SmassT_INPUTS:
        {
            // Call again, but this time with molar units
            // S: [J/kg/K] * [kg/mol] -> [J/mol/K]
            update(SmolarT_INPUTS, value1 * (double)_molar_mass, value2 );
            return;
        }
        case HmolarT_INPUTS:
        {
            // Unit conversion for REFPROP
            hmol = value1; _T = value2;

            /*
            c  additional input--only for THFLSH, TSFLSH, and TEFLSH
            c       kr--flag specifying desired root for multi-valued inputs:
            c           1 = return lower density root
            c           2 = return higher density root
            */
            int kr = 1;

            // from REFPROP: subroutine THFLSH (t,h,z,kr,p,D,Dl,Dv,x,y,q,e,s,cv,cp,w,ierr,herr)
            THFLSHdll(&_T,&hmol,&(mole_fractions[0]),&kr,&p_kPa,&rho_mol_L,
                &rhoLmol_L,&rhoVmol_L,&(mole_fractions_liq[0]),&(mole_fractions_vap[0]), // Saturation terms
                &q,&emol,&smol,&cvmol,&cpmol,&w, // Other thermodynamic terms
                &ierr,herr,errormessagelength); // Error terms

            if (static_cast<int>(ierr) > 0) { throw ValueError(format("HmolarT: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}

            // Set all cache values that can be set with unit conversion to SI
            _p = p_kPa*1000; // 1000 for conversion from kPa to Pa
            _rhomolar = rho_mol_L*1000; // 1000 for conversion from mol/L to mol/m3
            _rhoLmolar = rhoLmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            _rhoVmolar = rhoVmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            break;
        }
        case HmassT_INPUTS:
        {
            // Call again, but this time with molar units
            // H: [J/kg] * [kg/mol] -> [J/mol]
            update(HmolarT_INPUTS, value1 * (double)_molar_mass, value2 );
            return;
        }
        case TUmolar_INPUTS:
        {
            // Unit conversion for REFPROP
            _T = value1; emol = value2;

            /*
            c  additional input--only for THFLSH, TSFLSH, and TEFLSH
            c       kr--flag specifying desired root for multi-valued inputs:
            c           1 = return lower density root
            c           2 = return higher density root
            */
            int kr = 1;

            // from REFPROP: subroutine TEFLSH (t,e,z,kr,p,D,Dl,Dv,x,y,q,h,s,cv,cp,w,ierr,herr)
            TEFLSHdll(&_T,&emol,&(mole_fractions[0]),&kr,&p_kPa,&rho_mol_L,
                &rhoLmol_L,&rhoVmol_L,&(mole_fractions_liq[0]),&(mole_fractions_vap[0]), // Saturation terms
                &q,&hmol,&smol,&cvmol,&cpmol,&w, // Other thermodynamic terms
                &ierr,herr,errormessagelength); // Error terms

            if (static_cast<int>(ierr) > 0) { throw ValueError(format("TUmolar: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}

            // Set all cache values that can be set with unit conversion to SI
            _p = p_kPa*1000; // 1000 for conversion from kPa to Pa
            _rhomolar = rho_mol_L*1000; // 1000 for conversion from mol/L to mol/m3
            if (0)
            _rhoLmolar = rhoLmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            _rhoVmolar = rhoVmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            break;
        }
        case TUmass_INPUTS:
        {
            // Call again, but this time with molar units
            // U: [J/kg] * [kg/mol] -> [J/mol]
            update(TUmolar_INPUTS, value1, value2 * (double)_molar_mass);
            return;
        }
        case PQ_INPUTS:
        {

            // c  Estimate temperature, pressure, and compositions to be used
            // c  as initial guesses to SATTP
            // c
            // c  inputs:
            // c   iFlsh--Phase flag:    0 - Flash calculation (T and P known)
            // c                         1 - T and xliq known, P and xvap returned
            // c                         2 - T and xvap known, P and xliq returned
            // c                         3 - P and xliq known, T and xvap returned
            // c                         4 - P and xvap known, T and xliq returned
            // c                         if this value is negative, the retrograde point will be returned
            // c        t--temperature [K] (input or output)
            // c        p--pressure [MPa] (input or output)
            // c        x--composition [array of mol frac]
            // c   iGuess--if set to 1, all inputs are used as initial guesses for the calculation
            // c  outputs:
            // c        d--overall molar density [mol/L]
            // c       Dl--molar density [mol/L] of saturated liquid
            // c       Dv--molar density [mol/L] of saturated vapor
            // c     xliq--liquid phase composition [array of mol frac]
            // c     xvap--vapor phase composition [array of mol frac]
            // c        q--quality
            // c     ierr--error flag:   0 = successful
            // c                         1 = unsuccessful
            // c     herr--error string (character*255 variable if ierr<>0)

            // Unit conversion for REFPROP
            p_kPa = 0.001*value1; q = value2; // Want p in [kPa] in REFPROP

            int iFlsh = 0, iGuess = 0, ierr = 0;
            if (std::abs(q) < 1e-10){
                iFlsh = 3; // bubble point
            }
            else if (std::abs(q-1) < 1e-10){
                iFlsh = 4; // dew point
            }
            if (iFlsh != 0){
                // SATTP (t,p,x,iFlsh,iGuess,d,Dl,Dv,xliq,xvap,q,ierr,herr)
                SATTPdll(&_T, &p_kPa, &(mole_fractions[0]), &iFlsh, &iGuess,
                      &rho_mol_L, &rhoLmol_L,&rhoVmol_L,
                      &(mole_fractions_liq[0]),&(mole_fractions_vap[0]), &q,
                      &ierr,herr,errormessagelength);
                if (ierr > 0L) {
                    ierr = 0;
                    // SATPdll(p, z, kph, T, Dl, Dv, x, y, ierr, herr)
                    //
                    //kph--Phase flag : 1 - Input x is liquid composition(bubble point)
                    //                - 1 - Force calculation in the liquid phase even if T<Ttrp
                    //                  2 - Input x is vapor composition(dew point)
                    //                - 2 - Force calculation in the vapor phase even if T<Ttrp
                    //                  3 - Input x is liquid composition along the freezing line(melting line)
                    //                  4 - Input x is vapor composition along the sublimation line
                    SATPdll(&_p, &(mole_fractions[0]), &iFlsh,
                        &_T, &rhoLmol_L, &rhoVmol_L, &(mole_fractions_liq[0]), &(mole_fractions_vap[0]),
                        &ierr, herr, errormessagelength);
                    rho_mol_L = (iFlsh == 1) ? rhoLmol_L : rhoVmol_L;
                }
                if (ierr <= 0L){
                    // Calculate everything else
                    THERMdll(&_T, &rho_mol_L, &(mole_fractions[0]), &p_kPa, &emol, &hmol, &smol, &cvmol, &cpmol, &w, &hjt);
                }
            }
            if (static_cast<int>(ierr) > 0 || iFlsh == 0){
                // From REFPROP:
                //additional input--only for TQFLSH and PQFLSH
                //     kq--flag specifying units for input quality
                //         kq = 1 quality on MOLAR basis [moles vapor/total moles]
                //         kq = 2 quality on MASS basis [mass vapor/total mass]
                int kq = 1;
                ierr = 0;
                // Use flash routine to find properties
                PQFLSHdll(&p_kPa,&q,&(mole_fractions[0]),&kq,&_T,&rho_mol_L,
                    &rhoLmol_L,&rhoVmol_L,&(mole_fractions_liq[0]),&(mole_fractions_vap[0]), // Saturation terms
                    &emol,&hmol,&smol,&cvmol,&cpmol,&w, // Other thermodynamic terms
                    &ierr,herr,errormessagelength); // Error terms
            }

            if (static_cast<int>(ierr) > 0) { throw ValueError(format("PQ: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}

            // Set all cache values that can be set with unit conversion to SI
            _p = value1;
            _rhomolar = rho_mol_L*1000; // 1000 for conversion from mol/L to mol/m3
            _rhoLmolar = rhoLmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            _rhoVmolar = rhoVmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            break;
        }
        case QT_INPUTS:
        {
            // Unit conversion for REFPROP
            q = value1; _T = value2;

            // Use flash routine to find properties
            int iFlsh = 0, iGuess = 0;
            if (std::abs(q) < 1e-10){
                iFlsh = 1; // bubble point with T given
            }
            else if (std::abs(q-1) < 1e-10){
                iFlsh = 2; // dew point with T given
            }
            if (iFlsh != 0){
                // SATTP (t,p,x,iFlsh,iGuess,d,Dl,Dv,xliq,xvap,q,ierr,herr)
                SATTPdll(&_T, &p_kPa, &(mole_fractions[0]), &iFlsh, &iGuess,
                      &rho_mol_L, &rhoLmol_L,&rhoVmol_L,
                      &(mole_fractions_liq[0]),&(mole_fractions_vap[0]), &q,
                      &ierr,herr,errormessagelength);

                if (ierr > 0L){
                    ierr = 0;
                    // SATTdll(T, z, kph, P, Dl, Dv, x, y, ierr, herr)
                    //
                    //kph--Phase flag : 1 - Input x is liquid composition(bubble point)
                    //                - 1 - Force calculation in the liquid phase even if T<Ttrp
                    //                  2 - Input x is vapor composition(dew point)
                    //                - 2 - Force calculation in the vapor phase even if T<Ttrp
                    //                  3 - Input x is liquid composition along the freezing line(melting line)
                    //                  4 - Input x is vapor composition along the sublimation line
                    SATTdll(&_T, &(mole_fractions[0]), &iFlsh,
                        &p_kPa, &rhoLmol_L, &rhoVmol_L,&(mole_fractions_liq[0]), &(mole_fractions_vap[0]),
                        &ierr, herr, errormessagelength);
                    rho_mol_L = (iFlsh == 1) ? rhoLmol_L : rhoVmol_L;
                }
                if (ierr <= 0L){
                    // Calculate everything else since we were able to carry out a flash call
                    THERMdll(&_T, &rho_mol_L, &(mole_fractions[0]), &p_kPa, &emol, &hmol, &smol, &cvmol, &cpmol, &w, &hjt);
                }
            }
            if (static_cast<int>(ierr) > 0 || iFlsh == 0){
                ierr = 0;
                /* From REFPROP:
                additional input--only for TQFLSH and PQFLSH
                kq--flag specifying units for input quality
                kq = 1 quality on MOLAR basis [moles vapor/total moles]
                kq = 2 quality on MASS basis [mass vapor/total mass]
                */
                int kq = 1;
                TQFLSHdll(&_T,&q,&(mole_fractions[0]),&kq,&p_kPa,&rho_mol_L,
                     &rhoLmol_L,&rhoVmol_L,&(mole_fractions_liq[0]),&(mole_fractions_vap[0]), // Saturation terms
                    &emol,&hmol,&smol,&cvmol,&cpmol,&w, // Other thermodynamic terms
                    &ierr,herr,errormessagelength); // Error terms
            }

            if (static_cast<int>(ierr) > 0) {
                throw ValueError(format("TQ(%s): %s",LoadedREFPROPRef.c_str(), herr).c_str());
                }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());

            // Set all cache values that can be set with unit conversion to SI
            _p = p_kPa*1000; // 1000 for conversion from kPa to Pa
            _rhomolar = rho_mol_L*1000; // 1000 for conversion from mol/L to mol/m3
            _rhoLmolar = rhoLmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            _rhoVmolar = rhoVmol_L*1000; // 1000 for conversion from mol/L to mol/m3
            break;
        }
        default:
        {
            throw ValueError(format("This pair of inputs [%s] is not yet supported", get_input_pair_short_desc(input_pair).c_str()));
        }

    };
    // Set these common variables that are used in every flash calculation
    _hmolar = hmol;
    _smolar = smol;
    _umolar = emol;
    _cvmolar = cvmol;
    _cpmolar = cpmol;
    _speed_sound = w;
    _tau = calc_T_reducing()/_T;
    _delta = _rhomolar/calc_rhomolar_reducing();
    _gibbsmolar = hmol-_T*smol;
    _Q = q;
    if (imposed_phase_index == iphase_not_imposed) {  // If phase is imposed, _phase will already be set.
        if (Ncomp == 1) {          // Only set _phase for pure fluids
            _phase = GetRPphase(); // Set the CoolProp _phase variable based on RefProp's quality value (q)
        }
    }
}

void REFPROPMixtureBackend::update_with_guesses(CoolProp::input_pairs input_pair,
                         double value1,
                         double value2,
                         const GuessesStructure &guesses)
{
    this->check_loaded_fluid();
    double rho_mol_L=_HUGE,
        hmol=_HUGE,emol=_HUGE,smol=_HUGE,cvmol=_HUGE,cpmol=_HUGE,
        w=_HUGE,q=_HUGE, p_kPa = _HUGE, hjt = _HUGE;
    int ierr = 0;
    char herr[errormessagelength+1];

    clear();

    // Check that mole fractions have been set, etc.
    check_status();

    switch(input_pair)
    {
        case PT_INPUTS:{
            // Unit conversion for REFPROP
            p_kPa = 0.001*value1; _T = value2; // Want p in [kPa] in REFPROP

            //THERMdll(&_T, &rho_mol_L, &(mole_fractions[0]), &p_kPa, &emol, &hmol, &smol, &cvmol, &cpmol, &w, &hjt);
            int kguess = 1; // guess provided
            if (!ValidNumber(guesses.rhomolar)){ throw ValueError(format("rhomolar must be provided in guesses")); }

            int kph = (guesses.rhomolar > calc_rhomolar_critical()) ? 1 : 2; // liquid  if density > rhoc, vapor otherwise - though we are passing the guess density
            rho_mol_L = guesses.rhomolar/1000.0;
            TPRHOdll(&_T, &p_kPa, &(mole_fractions[0]), &kph, &kguess, &rho_mol_L, &ierr, herr, errormessagelength);
            if (static_cast<int>(ierr) > 0) { throw ValueError(format("PT: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}

            // Set all cache values that can be set with unit conversion to SI
            _p = value1;
            _rhomolar = rho_mol_L*1000; // 1000 for conversion from mol/L to mol/m3
            break;
        }
        case PQ_INPUTS:{
            // Unit conversion for REFPROP
            p_kPa = 0.001*value1; q = value2; // Want p in [kPa] in REFPROP
            double rhoLmol_L = -1, rhoVmol_L = -1;
            int iFlsh = 0,
                 iGuess = 1, // Use guesses
                 ierr = 0;

            if (std::abs(value2) < 1e-10){
                iFlsh = 3; // bubble point
                if (!guesses.x.empty()){
                    mole_fractions = guesses.x;
                    while(mole_fractions.size() < ncmax){ mole_fractions.push_back(0.0); }
                }
                else{
                    throw ValueError(format("x must be provided in guesses"));
                }
            }
            else if (std::abs(value2-1) < 1e-10){
                iFlsh = 4; // dew point
                if (!guesses.y.empty()){
                    mole_fractions = guesses.y;
                    while (mole_fractions.size() < ncmax) { mole_fractions.push_back(0.0); }
                }
                else{
                    throw ValueError(format("y must be provided in guesses"));
                }
            }
            else{
                throw ValueError(format("For PQ w/ guesses, Q must be either 0 or 1"));
            }
            if (get_debug_level() > 9){ std::cout << format("guesses.T: %g\n",guesses.T); }
            if (!ValidNumber(guesses.T)){
                throw ValueError(format("T must be provided in guesses"));
            }
            else{
                _T = guesses.T;
            }

            // SATTP (t,p,x,iFlsh,iGuess,d,Dl,Dv,xliq,xvap,q,ierr,herr)
            SATTPdll(&_T, &p_kPa, &(mole_fractions[0]), &iFlsh, &iGuess,
                     &rho_mol_L, &rhoLmol_L, &rhoVmol_L,
                     &(mole_fractions_liq[0]),&(mole_fractions_vap[0]), &q,
                     &ierr,herr,errormessagelength);

            if (static_cast<int>(ierr) > 0) { throw ValueError(format("PQ: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}

            // Set all cache values that can be set with unit conversion to SI
            _p = value1;
            _rhomolar = rho_mol_L*1000; // 1000 for conversion from mol/L to mol/m3
            break;
        }
        default:
        {
            throw CoolProp::ValueError(format("Unable to match given input_pair in update_with_guesses"));
        }
    }

    // Calculate everything else
    THERMdll(&_T, &rho_mol_L, &(mole_fractions[0]), &p_kPa, &emol, &hmol, &smol, &cvmol, &cpmol, &w, &hjt);

    // Set these common variables that are used in every flash calculation
    _hmolar = hmol;
    _smolar = smol;
    _umolar = emol;
    _cvmolar = cvmol;
    _cpmolar = cpmol;
    _speed_sound = w;
    _tau = calc_T_reducing()/_T;
    _delta = _rhomolar/calc_rhomolar_reducing();
    _Q = q;

}
CoolPropDbl REFPROPMixtureBackend::call_phixdll(int itau, int idel)
{
    this->check_loaded_fluid();
    double val = 0, tau = _tau, delta = _delta;
    if (PHIXdll == NULL){throw ValueError("PHIXdll function is not available in your version of REFPROP. Please upgrade");}
    PHIXdll(&itau, &idel, &tau, &delta, &(mole_fractions[0]), &val);
    return static_cast<CoolPropDbl>(val)/pow(static_cast<CoolPropDbl>(_delta),idel)/pow(static_cast<CoolPropDbl>(_tau),itau);
}
CoolPropDbl REFPROPMixtureBackend::call_phi0dll(int itau, int idel)
{
    this->check_loaded_fluid();
    double val = 0, tau = _tau, __T = T(), __rho = rhomolar()/1000;
    if (PHI0dll == NULL){throw ValueError("PHI0dll function is not available in your version of REFPROP. Please upgrade");}
    PHI0dll(&itau, &idel, &__T, &__rho, &(mole_fractions[0]), &val);
    return static_cast<CoolPropDbl>(val)/pow(tau,itau); // Not multiplied by delta^idel
}
/// Calculate excess properties
void REFPROPMixtureBackend::calc_excess_properties(){
    this->check_loaded_fluid();
    int ierr = 0;
    char herr[255];
    double T_K = _T, p_kPa = _p/1000.0, rho=1, vE = -1, eE = -1, hE = -1, sE = -1, aE = -1, gE = -1;
    int kph = 1;

    //    subroutine EXCESS(t, p, x, kph, rho, vE, eE, hE, sE, aE, gE, ierr, herr)
    //    c
    //    c  compute excess properties as a function of temperature, pressure,
    //    c  and composition.
    //    c
    //    c  inputs :
    //c        t--temperature[K]
    //    c        p--pressure[kPa]
    //    c        x--composition[array of mol frac]
    //    c      kph--phase flag : 1 = liquid
    //    c                        2 = vapor
    //    c                        0 = stable phase
    //    c  outputs :
    //c       rho--molar density[mol / L](if input less than 0, used as initial guess)
    //    c        vE--excess volume[L / mol]
    //    c        eE--excess energy[J / mol]
    //    c        hE--excess enthalpy[J / mol]
    //    c        sE--excess entropy[J / mol - K]
    //    c        aE--excess Helmholtz energy[J / mol]
    //    c        gE--excess Gibbs energy[J / mol]
    //    c      ierr--error flag : 0 = successful
    //    c                        55 = T, p inputs in different phase for the pure fluids
    //    c      herr--error string(character * 255 variable if ierr<>0)
    EXCESSdll(&T_K, &p_kPa, &(mole_fractions[0]), &kph,
        &rho, &vE, &eE, &hE, &sE, &aE, &gE,
        &ierr, herr, errormessagelength);      // Error message
    if (static_cast<int>(ierr) > 0) { throw ValueError(format("EXCESSdll: %s", herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
    _volumemolar_excess = vE;
    _umolar_excess = eE;
    _hmolar_excess = hE;
    _smolar_excess = sE;
    _helmholtzmolar_excess = aE;
    _gibbsmolar_excess = gE;
}

void REFPROPMixtureBackend::calc_true_critical_point(double &T, double &rho)
{

    class wrapper : public FuncWrapperND
    {
    public:
        const std::vector<double> z;
        wrapper(const std::vector<double> &z) : z(z) {};
        std::vector<double> call(const std::vector<double>& x){
            std::vector<double> r(2);
            double dpdrho__constT = _HUGE, d2pdrho2__constT = _HUGE;
            DPDDdll(const_cast<double *>(&(x[0])), const_cast<double *>(&(x[1])), const_cast<double *>(&(z[0])), &dpdrho__constT);
            DPDD2dll(const_cast<double *>(&(x[0])), const_cast<double *>(&(x[1])), const_cast<double *>(&(z[0])), &d2pdrho2__constT);
            r[0] = dpdrho__constT;
            r[1] = d2pdrho2__constT;
            return r;
        };
    };
    wrapper resid(mole_fractions);

    T = calc_T_critical();
    double rho_moldm3 = calc_rhomolar_critical()/1000.0;
    std::vector<double> x(2,T); x[1] = rho_moldm3;
    std::vector<double> xfinal = NDNewtonRaphson_Jacobian(&resid, x, 1e-9, 30);
    T = xfinal[0]; rho = xfinal[1]*1000.0;
}

CoolPropDbl REFPROPMixtureBackend::calc_saturated_liquid_keyed_output(parameters key) {
    if (_rhoLmolar) {
        if (key == iDmolar) {
            return _rhoLmolar;
        }
        else if (key == iDmass) {
            return static_cast<double>(_rhoLmolar)*calc_saturated_liquid_keyed_output(imolar_mass);
        }
        else if (key == imolar_mass){
            double wmm_kg_kmol = 0;
            WMOLdll(&(mole_fractions_liq[0]), &wmm_kg_kmol); // returns mole mass in kg/kmol
            return wmm_kg_kmol/1000; // kg/mol
        }
        else {
            throw ValueError("Invalid parameter. Only mass and molar density are available with RefProp");
            return _HUGE;
        }
    }
    throw ValueError("The saturated liquid state has not been set.");
    return _HUGE;
}
CoolPropDbl REFPROPMixtureBackend::calc_saturated_vapor_keyed_output(parameters key) {
    if (_rhoVmolar) {
        if (key == iDmolar) {
            return _rhoVmolar;
        }
        else if (key == iDmass) {
            return static_cast<double>(_rhoVmolar)*calc_saturated_vapor_keyed_output(imolar_mass);
        }
        else if (key == imolar_mass){
            double wmm_kg_kmol = 0;
            WMOLdll(&(mole_fractions_vap[0]), &wmm_kg_kmol); // returns mole mass in kg/kmol
            return wmm_kg_kmol/1000; // kg/mol
        }
        else {
            throw ValueError("Invalid key.");
            return _HUGE;
        }
    }
    throw ValueError("The saturated vapor state has not been set.");
    return _HUGE;
}

void REFPROPMixtureBackend::calc_ideal_curve(const std::string &type, std::vector<double> &T, std::vector<double> &p){
    if (type == "Joule-Thomson"){
        JouleThomsonCurveTracer JTCT(this, 1e5, 800);
        JTCT.trace(T, p);
    }
    else if (type == "Joule-Inversion"){
        JouleInversionCurveTracer JICT(this, 1e5, 800);
        JICT.trace(T, p);
    }
    else if (type == "Ideal"){
        IdealCurveTracer ICT(this, 1e5, 800);
        ICT.trace(T, p);
    }
    else if (type == "Boyle"){
        BoyleCurveTracer BCT(this, 1e5, 800);
        BCT.trace(T, p);
    }
    else{
        throw ValueError(format("Invalid ideal curve type: %s", type.c_str()));
    }
};

bool force_load_REFPROP() {
    std::string err;
    if (!load_REFPROP(err)) {
        if (CoolProp::get_debug_level() > 5) { std::cout << format("Error while loading REFPROP: %s", err) << std::endl; }
        LoadedREFPROPRef = "";
        return false;
    } else {
        LoadedREFPROPRef = "";
        return true;
    }
}
bool force_unload_REFPROP() {
    std::string err;
    if (!unload_REFPROP(err)) {
        if (CoolProp::get_debug_level() > 5) { std::cout << format("Error while unloading REFPROP: %s", err) << std::endl; }
        LoadedREFPROPRef = "";
        return false;
    } else {
        LoadedREFPROPRef = "";
        return true;
    }
}

void REFPROP_SETREF(char hrf[3], int ixflag, double x0[1], double &h0, double &s0, double &T0, double &p0, int &ierr, char herr[255], int l1, int l2) {
    std::string err;
    bool loaded_REFPROP = ::load_REFPROP(err);
    if (!loaded_REFPROP) {
        throw ValueError(format("Not able to load REFPROP; err is: %s", err.c_str()));
    }
    SETREFdll(hrf, &ixflag, x0, &h0, &s0, &T0, &p0, &ierr, herr, l1, l2);
}

} /* namespace CoolProp */


#ifdef ENABLE_CATCH
#include "CoolProp.h"
#include "catch.hpp"

TEST_CASE("Check REFPROP and CoolProp values agree","[REFPROP]")
{
    SECTION("Saturation densities agree within 0.5% at T/Tc = 0.9")
    {
        std::vector<std::string> ss = strsplit(CoolProp::get_global_param_string("FluidsList"),',');

        for (std::vector<std::string>::iterator it = ss.begin(); it != ss.end(); ++it)
        {
            std::string Name = (*it);
            std::string RPName = CoolProp::get_fluid_param_string((*it),"REFPROP_name");

            // Skip fluids not in REFPROP
            if (RPName.find("N/A") == 0){continue;}

            shared_ptr<CoolProp::AbstractState> S1(CoolProp::AbstractState::factory("HEOS", (*it)));
            double Tr = S1->T_critical();
            CHECK_NOTHROW(S1->update(CoolProp::QT_INPUTS, 0, Tr*0.9));
            double rho_CP = S1->rhomolar();

            shared_ptr<CoolProp::AbstractState> S2(CoolProp::AbstractState::factory("REFPROP", RPName));
            CHECK_NOTHROW(S2->update(CoolProp::QT_INPUTS, 0, Tr*0.9));
            double rho_RP = S2->rhomolar();

            CAPTURE(Name);
            CAPTURE(RPName);
            CAPTURE(rho_CP);
            CAPTURE(rho_RP);

            double DH = (rho_RP-rho_CP)/rho_RP;
            CHECK(std::abs(DH) < 0.05);
        }
    }
    SECTION("Saturation specific heats agree within 0.5% at T/Tc = 0.9")
    {
        std::vector<std::string> ss = strsplit(CoolProp::get_global_param_string("FluidsList"),',');

        for (std::vector<std::string>::iterator it = ss.begin(); it != ss.end(); ++it)
        {
            std::string Name = (*it);
            std::string RPName = CoolProp::get_fluid_param_string((*it),"REFPROP_name");

            // Skip fluids not in REFPROP
            if (RPName.find("N/A") == 0){continue;}

            shared_ptr<CoolProp::AbstractState> S1(CoolProp::AbstractState::factory("HEOS", (*it)));
            double Tr = S1->T_critical();
            S1->update(CoolProp::QT_INPUTS, 0, Tr*0.9);
            double cp_CP = S1->cpmolar();

            shared_ptr<CoolProp::AbstractState> S2(CoolProp::AbstractState::factory("REFPROP", RPName));
            S2->update(CoolProp::QT_INPUTS, 0, Tr*0.9);
            double cp_RP = S2->cpmolar();

            CAPTURE(Name);
            CAPTURE(RPName);
            CAPTURE(cp_CP);
            CAPTURE(cp_RP);
            CAPTURE(0.9*Tr);

            double Dcp = (cp_RP-cp_CP)/cp_RP;
            CHECK(std::abs(Dcp) < 0.05);
        }
    }
    SECTION("Enthalpy and entropy reference state")
    {
        std::vector<std::string> ss = strsplit(CoolProp::get_global_param_string("FluidsList"),',');

        for (std::vector<std::string>::iterator it = ss.begin(); it != ss.end(); ++it)
        {
            std::string Name = (*it);
            std::string RPName = CoolProp::get_fluid_param_string((*it),"REFPROP_name");

            // Skip fluids not in REFPROP
            if (RPName.find("N/A") == 0){continue;}

            shared_ptr<CoolProp::AbstractState> S1(CoolProp::AbstractState::factory("HEOS", (*it)));
            double Tr = S1->T_critical();
            CHECK_NOTHROW(S1->update(CoolProp::QT_INPUTS, 0, 0.9*Tr));
            double h_CP = S1->hmass();
            double s_CP = S1->smass();

            shared_ptr<CoolProp::AbstractState> S2(CoolProp::AbstractState::factory("REFPROP", RPName));
            CHECK_NOTHROW(S2->update(CoolProp::QT_INPUTS, 0, 0.9*Tr));
            double h_RP = S2->hmass();
            double s_RP = S2->smass();

            double delta_a1 = (s_CP-s_RP)/(S1->gas_constant()/S1->molar_mass());
            double delta_a2 = -(h_CP - h_RP)/(S1->gas_constant()/S1->molar_mass()*S1->get_reducing_state().T);
            CAPTURE(format("%0.16f",delta_a1));
            CAPTURE(format("%0.16f",delta_a2));

            CAPTURE(Name);
            CAPTURE(RPName);
            CAPTURE(h_CP);
            CAPTURE(h_RP);
            CAPTURE(s_CP);
            CAPTURE(s_RP);
            double DH = (S1->hmass()-S2->hmass());
            double DS = (S1->smass()-S2->smass());

            CHECK(std::abs(DH/h_RP) < 0.01);
            CHECK(std::abs(DS/s_RP) < 0.01);
        }
    }
}

TEST_CASE("Check trivial inputs for REFPROP work", "[REFPROP_trivial]")
{
    const int num_inputs = 6;
    std::string inputs[num_inputs] = {"T_triple", "T_critical", "p_critical", "molar_mass", "rhomolar_critical", "rhomass_critical"};
    for (int i = 0; i < num_inputs; ++i){
        std::ostringstream ss;
        ss << "Check " << inputs[i];
        SECTION(ss.str(),"")
        {
            double cp_val = CoolProp::PropsSI(inputs[i],"P",0,"T",0,"HEOS::Water");
            double rp_val = CoolProp::PropsSI(inputs[i],"P",0,"T",0,"REFPROP::Water");

            std::string errstr = CoolProp::get_global_param_string("errstring");
            CAPTURE(errstr);
            double err = (cp_val - rp_val)/cp_val;
            CHECK(err < 1e-3);
        }
    }
}

#endif
