/*
 * This is the base substance class from which all substances are derived
 * 
 * Kate Talmazan: SURF -- July, 1995
 *   original implementation of this class and all derived classes from 
 *   formulas given in TPSI. Implementation of P(Rho, T), cv0(T), ldens(T),
 *   and Psat(T) for all substances in TPSI.f
 *
 * Dave Goodwin: Fall, 1996
 *   functions for u, h, s, f, g; 
 *   functions to set state
 *   error handling
 *   documentation 
 *
 *   Sept., 2001: minor modifications to use with Cantera
 *
 */

#ifndef TPX_SUB_H
#define TPX_SUB_H

#include <iostream>
#include <string>
using namespace std;

namespace tpx {

    const double OneAtm = 1.01325e5;
    const double Liquid = 0.0;
    const double Vapor = 1.0;

    const int TV = 12, HP = 34, SP = 54, PV = 42, TP = 14, UV = 62, 
              ST = 51, SV = 52, UP = 64, VH = 23, TH = 13, SH = 53, 
              PX = 47, TX = 17;

    const int VT = -12, PH = -34, PS = -54, VP = -42, PT = -14, VU = -62,
              TS = -51, VS = -52, PU = -64, HV = -23, HT = -13, HS = -53,
              XP = -47, XT = -17;

    const int NoConverge = -900;
    const int GenError = -901;
    const int InvalidInput = -902;
    const int TempError = -800;
    const int PresError = -801;
    const int CKError = -802;


    const int Pgiven = 0, Tgiven = 1;

    const int EvalH = 3;  const int EvalS = 5;
    const int EvalU = 6;  const int EvalV = 2;  const int EvalP = 4;
    const int EvalT = 1;  const int EvalX = 7;  const int EvalF = 8;
    const int EvalG = 9; const int EvalC = 10;
    const int EvalM = 11; const int EvalN = 12; const int EvalMW = 13;
    const int EvalEA = 14;
    const int EvalCdot = 15; const int EvalDdot = 16; const int EvalWdot = 17;
    const int EvalTchem = 18; const int EvalRgas = 19;

    const double Undef = 999.1234;

    string errorMsg(int flag);

    class Substance { 
    public:
        Substance() { 
            T = Undef;
            Rho = Undef;
            Tslast = Undef; 
            Rhf = Undef; 
            Rhv = Undef; 
            Pst = Undef; 
            Err = 0;
            m_energy_offset = 0.0;
            m_entropy_offset = 0.0;
        }
	virtual ~Substance(){}

        void setStdState(double h0 = 0.0, double s0 = 0.0,
            double t0 = 298.15, double p0 = 1.01325e5) {
            Set(TP, t0, p0);
            double hoff = h0 - h();
            double soff = s0 - s();
            m_entropy_offset = soff;
            m_energy_offset = hoff;
        }

        // information about a substance:

        virtual double MolWt()=0;          // molecular weight, kg/kmol
        virtual double Tcrit()=0;          // critical temperature, K
        virtual double Pcrit()=0;          // critical pressure, Pa
        virtual double Vcrit()=0;          // critical specific vol, m^3/kg
        virtual double Tmin()=0;           // min. temp for which equations valid
        virtual double Tmax()=0;           // max. temp for which equations valid
        virtual char * name() = 0;         // name
        virtual char * formula() = 0;      // chemical formula
        
        // properties:
        
        double P();                        // pressure, Pa
        double Temp() {return T;}          // temperature, K
        double v()                         // specific vol, m^3/kg
            {return prop(EvalV);}
        double u()                         // int. energy, J/kg
            {return prop(EvalU);}
        double h()                         // enthalpy, J/kg
            {return prop(EvalH);}
        double s()                         // entropy, J/kg/K
            {return prop(EvalS);}
        double f()                         // Helmholz function, J/kg
            {return u() - T*s();}
        double g()                         // Gibbs function, J/kg
            {return h() - T*s();}

        virtual double cv() {
            double Tsave = T, dt = 1.e-4*T;
            set_T(Tsave - dt);
            double s1 = s();
            set_T(Tsave + dt);
            double s2 = s();
            set_T(Tsave);
            return T*(s2 - s1)/(2.0*dt);
        }

        virtual double cp() {
            double Tsave = T, dt = 1.e-4*T;
            double p0 = P();
            Set(TP, Tsave - dt, p0);
            double s1 = s();
            Set(TP, Tsave + dt, p0);
            double s2 = s();
            Set(TP, Tsave, p0);
            return T*(s2 - s1)/(2.0*dt);
        }

        virtual double thermExpCoeff() {
            double Tsave = T, dt = 1.e-4*T;
            double p0 = P();
            Set(TP, Tsave - dt, p0);
            double v1 = v();
            Set(TP, Tsave + dt, p0);
            double v2 = v();
            Set(TP, Tsave, p0);
            return (v2 - v1)/((v2 + v1)*dt);
        }


        // saturation properties

        double Ps();
        virtual double dPsdT();          // d(Psat)/dT, Pa/K
        double Tsat(double p);             // saturation temp at p
        double x();                        // vapor mass fraction
        int TwoPhase();                    // =1 if vapor/liquid, 0 otherwise
        virtual double Pp()=0;
        double hp() {return up() + Pp()/Rho;} 
        double gp() {return hp() - T*sp();}
        
        double prop(int ijob);
        void set_TPp(double t0, double p0);    // set T and P

        
        // functions to set or change state:

        void Set(int XY, double x0, double y0);
        void Set_meta(double phase, double pp);	 

        int Error() {
            return Err;
        } 


    protected:   

	double T, Rho;
	double Tslast, Rhf, Rhv;
	double Pst;
	int Err;
        double m_energy_offset;
        double m_entropy_offset;

        //	virtual double Xm(int k) { return 1.0;}
        //virtual int Species() { return 1;}

	virtual double ldens()=0;
	virtual double Psat()=0;           // saturation pressure, Pa
	virtual double up()=0;
	virtual double sp()=0;
	virtual int ideal(){return 0;}     // added 9/2/98; default is false
	double vp() {return 1.0/Rho;}
	int Lever(int itp, double sat, double val, int ifunc);
	void update_sat();

	void set_Err(int ErrFlag) {
		if (!Err) Err = ErrFlag;
	}
	void clear_Err() {Err = 0;}


private:
	  void set_Rho(double r0);
	  void set_T(double t0);
	  void set_v(double v0);
	  void BracketSlope(double p);
	  double lprop(int ijob);
	  double vprop(int ijob);
	  void set_xy(int if1, int if2, double X, double Y, 
		  double atx, double aty, double rtx, double rty);
    };

    void Error(char *message, int flag, double val=Undef);
    void Mess(char *message);

}


#endif