package sansmodels;

public class TwoHomopolymerRPA extends SANSModel{
 
    private double na, nb, phi, va, vb, deltaRho, aa, ab;
    private double interaction, background;

    //Default constructor
    public TwoHomopolymerRPA() {
        na = 1000.0;
        nb = 1000.0;
        phi = 0.2;
        va = 100.0;
        vb = 100.0;
        deltaRho = 2.0e-6;
        aa = 6.0;
        ab = 7.0;
        interaction = 0.0;
        background = 0.0;
        setNumberOfParameters(10);
        String[] parameters = {"Polymerization A","Polymerization B",
            "Vol. Frac A", "Seg. Vol. A(cm^3/mol)", 
            "Seg. Vol. B(cm^3/mol)", "deltaRho A-B (A-2)", 
            "Seg. Length A (A)", "Seg. Length B (A)", 
            "Interaction AB","Background (cm-1)"};
        setParametersText(parameters);
    }

    public TwoHomopolymerRPA(double inNa, double inNb,
                  double inPhi, 
                  double inVa, double inVb, 
                  double inDeltaRho,
                  double inAa, double inAb,
                  double inInt, double inBackground) {
        na  = inNa;
        nb  = inNb;
        phi  = inPhi;
        if(phi >= 1.0) phi = 0.999999;
        va  = inVa;
        vb  = inVb;
        deltaRho  = inDeltaRho;
        aa  = inAa;
        ab  = inAb;
        interaction  = inInt;
        background = inBackground;
        setNumberOfParameters(10);
        String[] parameters = {"Polymerization A","Polymerization B",
            "Vol. Frac A wrt B", "Seg. Vol. A(cm^3/mol)", 
            "Seg. Vol. B(cm^3/mol)", "deltaRho A-B (A-2)", 
            "Seg. Length A (A)", "Seg. Length B (A)", 
            "Interaction AB","Background (cm-1)"};
        setParametersText(parameters);
    }

    public double getFormFactor(double inX) {
        double term1, term2, term3, term4, sq, rg, debye, x;
        
        rg = Math.sqrt(na*aa*aa/6.0);
        x = inX*inX*rg*rg;
        debye = 2.0*(Math.exp(-1.0*x) + x - 1.0)/(x*x);
        term1 = 1.0/(na*va*phi*debye);

        rg = Math.sqrt(nb*ab*ab/6.0);
        x = inX*inX*rg*rg;
        debye = 2.0*(Math.exp(-1.0*x) + x - 1.0)/(x*x);
        term2 = 1.0/(nb*vb*(1.0-phi)*debye);

        term3 = 2.0*interaction/Math.sqrt(va*vb);

        term4=deltaRho*deltaRho*1.6606e8;        
 
        sq = term4/(term1 + term2 - term3);

        return sq*getStructureFactor().calculate(inX) + background;
    }

    public void setParameters(double[] inParameters) {
        na = inParameters[0];
        nb = inParameters[1];
        phi = inParameters[2];
        if(phi >= 1.0) phi = 0.999999;
        va = inParameters[3];
        vb = inParameters[4];
        deltaRho = inParameters[5];
        aa = inParameters[6];
        ab = inParameters[7];
        interaction = inParameters[8];
        background = inParameters[9];
    }
 
    public double[] getParameters() {
        double[] outParameters = new double[10];
        outParameters[0] = na;
        outParameters[1] = nb;
        outParameters[2] = phi;
        outParameters[3] = va;
        outParameters[4] = vb;
        outParameters[5] = deltaRho;
        outParameters[6] = aa;
        outParameters[7] = ab;
        outParameters[8] = interaction;
        outParameters[9] = background;
        return outParameters;
    }
}