package sansmodels;

public class PolyCoreShellRatio extends SANSModel{
 
    private double scale, coreRadius, thickness, background;
    private double rhoCore, rhoShell, rhoSolvent, polyDisp;

    //Default constructor
    public PolyCoreShellRatio() {
        scale = 1.0;
        coreRadius = 60.0;
        thickness = 10.0;
        polyDisp = 0.2;
        rhoCore = 1.e-6;
        rhoShell = 2.e-6;
        rhoSolvent = 3.e-6;
        background = 0.000;
        setNumberOfParameters(8);
        String[] parameters = {"Scale", "Core Radius (A)",
            "Shell Thickness (A)", "Polydispersity (0-1)",
            "Core SLD (A-2)", "Shell SLD (A-2)",
            "Solvent SLD (A-2)", "Background (cm-1)"};
        setParametersText(parameters);
    }

    public PolyCoreShellRatio(double inScale, 
                     double inCoreRadius,
                     double inThickness,
                     double inPolyDisp,
                     double inRhoCore,
                     double inRhoShell,
                     double inRhoSolvent,
                     double inBackground) {
        scale = inScale; 
        coreRadius = inCoreRadius;
        thickness = inThickness;
        polyDisp = inPolyDisp;
        rhoCore = inRhoCore;
        rhoShell = inRhoShell;
        rhoSolvent = inRhoSolvent;
        background = inBackground;
        setNumberOfParameters(8);
        String[] parameters = {"Scale", "Core Radius (A)",
            "Shell Thickness (A)", "Polydispersity (0-1)",
            "Core SLD (A-2)", "Shell SLD (A-2)",
            "Solvent SLD (A-2)", "Background (cm-1)"};
        setParametersText(parameters);
    }

    private double fnt2(double inY, double inZ) {
        double z1, z2, z3, uu, ww, term1, term2, term3;
        
        z1 = inZ+1.0;
        z2 = inZ+2.0;
        z3 = inZ+3.0;
        uu = inY/z1;
        ww=Math.atan(2.0*uu);
        term1 = Math.cos(z1*ww)/Math.pow((1.0+4.0*uu*uu),(z1/2.0));
        term2 = 2.0*inY*Math.sin(z2*ww)/Math.pow((1.0+4.0*uu*uu),(z2/2.0));
        term3 = 1.0 + Math.cos(z3*ww)/Math.pow((1.0+4.0*uu*uu),(z3/2.0));

        return (4.5/z1/Math.pow(inY,6.0))*(z1*(1.0-term1-term2)
                +inY*inY*z2*term3);
    }

    private double fnt3(double inY, double inP, double inZ) {
        double z1,z2,z3,yp,yn,up,un,vp,vn,term1;
        double term2,term3,term4,term5,term6, answer;

        z1 = inZ+1.0;
        z2 = inZ+2.0;
        z3 = inZ+3.0;
        yp = (1.0+inP)*inY;
        yn = (1.0-inP)*inY;
        up = yp/z1;
        un = yn/z1;
        vp = Math.atan(up);
        vn = Math.atan(un);
        term1 = Math.cos(z1*vn)/Math.pow((1.0+un*un),(z1/2.0));
        term2 = Math.cos(z1*vp)/Math.pow((1.0+up*up),(z1/2.0));
        term3 = Math.cos(z3*vn)/Math.pow((1.0+un*un),(z3/2.0));
        term4 = Math.cos(z3*vp)/Math.pow((1.0+up*up),(z3/2.0));
        term5 = yn*Math.sin(z2*vn)/Math.pow((1.0+un*un),(z2/2.0));
        term6 = yp*Math.sin(z2*vp)/Math.pow((1.0+up*up),(z2/2.0));
        answer = (4.50/z1/Math.pow(inY,6.0));
        answer = answer*(z1*(term1-term2)+inY*inY*inP*z2*(term3+term4)
                  +z1*(term5-term6));

        return answer;
    }

    public double getFormFactor(double inX) {
        double zz, drho1, drho2, pp, totalRadius;
        double pi43, c1, c2, form, vol, arg1, arg2;
        
        totalRadius = coreRadius + thickness;
        if (polyDisp <= 0.0) polyDisp = 0.0001;
        if (polyDisp >= 1.0) polyDisp = 1.0;
        zz = 1.0/polyDisp/polyDisp - 1.0;
        drho1 = rhoCore - rhoShell;
        drho2 = rhoShell - rhoSolvent;
        pi43 = 4.0/3.0*Math.PI;
        pp = coreRadius/totalRadius;
        vol = pi43*totalRadius*totalRadius*totalRadius;
        c1 = drho1*vol;
        c2 = drho2*vol;

        arg1 = inX*totalRadius*pp;
        arg2 = inX*totalRadius;
        form = Math.pow(pp,6.0)*c1*c1*fnt2(arg1,zz);
        form += c2*c2*fnt2(arg2,zz);
        form += 2.0*c1*c2*fnt3(arg2,pp,zz);
        
        return form/vol*1.0e8*scale*getStructureFactor().calculate(inX)
            +background;
    }

    public void setParameters(double[] inParameters) {
        scale = inParameters[0];
        coreRadius = inParameters[1];
        thickness = inParameters[2];
        polyDisp = inParameters[3];
        rhoCore = inParameters[4];
        rhoShell = inParameters[5];
        rhoSolvent = inParameters[6];
        background = inParameters[7];
    }
 
    public double[] getParameters() {
        double[] outParameters = new double[8];
        outParameters[0] = scale;
        outParameters[1] = coreRadius;
        outParameters[2] = thickness;
        outParameters[3] = polyDisp;
        outParameters[4] = rhoCore;
        outParameters[5] = rhoShell;
        outParameters[6] = rhoSolvent;
        outParameters[7] = background;
        return outParameters;
    }
}