/**
 *  @file SingleSpeciesTP.h
 *  Header for the SingleSpeciesTP class, which is a filter class for ThermoPhase,
 *  that eases the construction of single species phases
 *  ( see @ref thermoprops and class @link Cantera::SingleSpeciesTP SingleSpeciesTP@endlink).
 */

// This file is part of Cantera. See License.txt in the top-level directory or
// at https://cantera.org/license.txt for license and copyright information.

#ifndef CT_SINGLESPECIESTP_H
#define CT_SINGLESPECIESTP_H

#include "ThermoPhase.h"

namespace Cantera
{

/**
 * @ingroup thermoprops
 *
 * The SingleSpeciesTP class is a filter class for ThermoPhase. What it does is
 * to simplify the construction of ThermoPhase objects by assuming that the
 * phase consists of one and only one type of species. In other words, it's a
 * stoichiometric phase. However, no assumptions are made concerning the
 * thermodynamic functions or the equation of state of the phase. Therefore it's
 * an incomplete description of the thermodynamics. The complete description
 * must be made in a derived class of SingleSpeciesTP.
 *
 * Several different groups of thermodynamic functions are resolved at this
 * level by this class. For example, All partial molar property routines call
 * their single species standard state equivalents. All molar solution
 * thermodynamic routines call the single species standard state equivalents.
 * Activities routines are resolved at this level, as there is only one species.
 *
 * It is assumed that the reference state thermodynamics may be obtained by a
 * pointer to a populated species thermodynamic property manager class (see
 * ThermoPhase::m_spthermo). How to relate pressure changes to the reference
 * state thermodynamics is again left open to implementation.
 *
 * Mole fraction and Mass fraction vectors are assumed to be equal to x[0] = 1
 * y[0] = 1, respectively. Simplifications to the interface of setState_TPY()
 * and setState_TPX() functions result and are made within the class.
 *
 * Note, this class can handle the thermodynamic description of one phase of one
 * species. It can not handle the description of phase equilibrium between two
 * phases of a stoichiometric compound (such as water liquid and water vapor, below
 * the critical point). However, it may be used to describe the thermodynamics
 * of one phase of such a compound even past the phase equilibrium point, up to
 * the point where the phase itself ceases to be a stable phase.
 *
 * This class doesn't do much at the initialization level. Its
 * SingleSpeciesTP::initThermo() member does check that one and only one species
 * has been defined to occupy the phase.
 */
class SingleSpeciesTP : public ThermoPhase
{
public:
    //! Base empty constructor.
    SingleSpeciesTP() = default;

    string type() const override {
        return "SingleSpecies";
    }

    bool isPure() const override {
        return true;
    }

    //! @name  Molar Thermodynamic Properties of the Solution
    //!
    //! These functions are resolved at this level, by reference to the partial
    //! molar functions and standard state functions for species 0. Derived
    //! classes don't need to supply entries for these functions.
    //! @{

    double enthalpy_mole() const override;
    double intEnergy_mole() const override;
    double entropy_mole() const override;
    double gibbs_mole() const override;
    double cp_mole() const override;
    double cv_mole() const override;

    //! @}
    //! @name Activities, Standard State, and Activity Concentrations
    //!
    //! The activity @f$ a_k @f$ of a species in solution is related to the
    //! chemical potential by @f[ \mu_k = \mu_k^0(T) + \hat R T \ln a_k. @f]
    //! The quantity @f$ \mu_k^0(T) @f$ is the chemical potential at unit activity,
    //! which depends only on temperature.
    //! @{

    /**
     * Get the array of non-dimensional activities at the current solution
     * temperature, pressure, and solution concentration.
     *
     * We redefine this function to just return 1.0 here.
     *
     * @param a   Output vector of activities. Length: 1.
     */
    void getActivities(double* a) const override {
        a[0] = 1.0;
    }

    void getActivityCoefficients(double* ac) const override {
        ac[0] = 1.0;
    }

    //! @}
    //! @name  Partial Molar Properties of the Solution
    //!
    //! These functions are resolved at this level, by reference to the partial
    //! molar functions and standard state functions for species 0. Derived
    //! classes don't need to supply entries for these functions.
    //! @{

    //! Get the array of chemical potentials
    /*!
     * These are the phase, partial molar, and the standard state chemical
     * potentials.
     *     @f$ \mu(T,P) = \mu^0_k(T,P) @f$.
     *
     * @param mu   On return, Contains the chemical potential of the single
     *             species and the phase. Units are J / kmol . Length = 1
     */
    void getChemPotentials(double* mu) const override;

    //! Get the species partial molar enthalpies. Units: J/kmol.
    /*!
     * These are the phase enthalpies.  @f$ h_k @f$.
     *
     * @param hbar    Output vector of species partial molar enthalpies.
     *                Length: 1. units are J/kmol.
     */
    void getPartialMolarEnthalpies(double* hbar) const override;

    //! Get the species partial molar internal energies. Units: J/kmol.
    /*!
     * These are the phase internal energies.  @f$ u_k @f$.
     *
     * @param ubar On return, Contains the internal energy of the single species
     *             and the phase. Units are J / kmol . Length = 1
     */
    void getPartialMolarIntEnergies(double* ubar) const override;

    //! Get the species partial molar entropy. Units: J/kmol K.
    /*!
     * This is the phase entropy.  @f$ s(T,P) = s_o(T,P) @f$.
     *
     * @param sbar On return, Contains the entropy of the single species and the
     *             phase. Units are J / kmol / K . Length = 1
     */
    void getPartialMolarEntropies(double* sbar) const override;

    //! Get the species partial molar Heat Capacities. Units: J/ kmol /K.
    /*!
     * This is the phase heat capacity.  @f$ Cp(T,P) = Cp_o(T,P) @f$.
     *
     * @param cpbar On return, Contains the heat capacity of the single species
     *              and the phase. Units are J / kmol / K . Length = 1
     */
    void getPartialMolarCp(double* cpbar) const override;

    //! Get the species partial molar volumes. Units: m^3/kmol.
    /*!
     * This is the phase molar volume.  @f$ V(T,P) = V_o(T,P) @f$.
     *
     * @param vbar On return, Contains the molar volume of the single species
     *             and the phase. Units are m^3 / kmol. Length = 1
     */
    void getPartialMolarVolumes(double* vbar) const override;

    //! @}
    //! @name  Properties of the Standard State of the Species in the Solution
    //!
    //! These functions are the primary way real properties are
    //! supplied to derived thermodynamics classes of SingleSpeciesTP.
    //! These functions must be supplied in derived classes. They
    //! are not resolved at the SingleSpeciesTP level.
    //! @{

    void getPureGibbs(double* gpure) const override;

    //! Get the molar volumes of each species in their standard states at the
    //! current *T* and *P* of the solution.
    /*!
     *   units = m^3 / kmol
     *
     * We resolve this function at this level, by assigning the molecular weight
     * divided by the phase density
     *
     * @param vbar On output this contains the standard volume of the species
     *             and phase (m^3/kmol). Vector of length 1
     */
    void getStandardVolumes(double* vbar) const override;

    //! @}
    //! @name Thermodynamic Values for the Species Reference State
    //!
    //! Almost all functions in this group are resolved by this class. The
    //! internal energy function is not given by this class, since it would
    //! involve a specification of the equation of state.
    //! @{

    void getEnthalpy_RT_ref(double* hrt) const override;
    void getGibbs_RT_ref(double* grt) const override;
    void getGibbs_ref(double* g) const override;
    void getEntropy_R_ref(double* er) const override;
    void getCp_R_ref(double* cprt) const override;

    //! @}
    //! @name Setting the State
    //!
    //! These methods set all or part of the thermodynamic state.
    //! @{

    //! Mass fractions are fixed, with Y[0] = 1.0.
    void setMassFractions(const double* const y) override {};

    //! Mole fractions are fixed, with x[0] = 1.0.
    void setMoleFractions(const double* const x) override {};

    //! @}

    bool addSpecies(shared_ptr<Species> spec) override;

protected:
    //! The current pressure of the solution (Pa). It gets initialized to 1 atm.
    double m_press = OneAtm;

    // Reference pressure (Pa). Must be the same for all species. Defaults to
    // 1 atm.
    double m_p0 = OneAtm;

    //! Dimensionless enthalpy at the (mtlast, m_p0)
    mutable double m_h0_RT;
    //! Dimensionless heat capacity at the (mtlast, m_p0)
    mutable double m_cp0_R;
    //! Dimensionless entropy at the (mtlast, m_p0)
    mutable double m_s0_R;

    //! This internal routine calculates new species Cp0, H0, and S0 whenever the
    //! temperature has changed.
    void _updateThermo() const;
};

}

#endif
