package sansmodels;

public class Ellipsoid extends SANSModel{
 
    private double scale, axisA, axisB, deltaRho, background;

    //Default constructor
    public Ellipsoid() {
        scale = 1.0;
        axisA = 20.0;
        axisB = 400.0;
        deltaRho = 3.e-6;
        background = 0.0;
        setNumberOfParameters(5);
        String[] parameters = {"Scale", "Axis A (A)",
            "Axis B (A)", "Contrast (A-2)", "Background (cm-1)"};
        setParametersText(parameters);
    }

    public Ellipsoid(double inScale, 
                     double inAxisA,
                     double inAxisB,
                     double inContrast,
                     double inBackground) {
        scale = inScale; 
        axisA = inAxisA;
        axisB = inAxisB;
        deltaRho = inContrast;
        background = inBackground;
        setNumberOfParameters(5);
        String[] parameters = {"Scale", "Axis A (A)",
            "Axis B (A)", "Contrast (A-2)", "Background (cm-1)"};
        setParametersText(parameters);
    }

    private double ellipsoidFunc(double inQ, double inX) {
        double arg, t1, nu;
        
        nu = axisA/axisB;
        arg = inQ*axisA*Math.sqrt(1.0+inX*inX*(nu*nu - 1.0));

        return 9.0*Math.pow((Math.sin(arg) 
                            - arg*Math.cos(arg))/arg/arg/arg,2.0);
    }
 
    public double getFormFactor(double inX) {

        int nord = 76;
        double va, vb, summ, zi, answer, yyy;
        double vol;
        va = 0.0;
        vb = 1.0;

        summ = 0.0;
        
        for(int i=0;i<nord;i++) {
            zi = (Gaussian.z76[i]*(vb-va) + vb + va)/2.0;
            yyy = Gaussian.w76[i]*ellipsoidFunc(inX,zi);
            summ += yyy;
        }
         
        answer = (vb-va)/2.0*summ;

        answer *= deltaRho*deltaRho;
        
        vol = 4.0*Math.PI/3.0*axisA*axisB*axisB;
        return answer*vol*1.0e8*scale*getStructureFactor().calculate(inX)
            + background;
    }

    public void setParameters(double[] inParameters) {
        scale = inParameters[0];
        axisA = inParameters[1];
        axisB = inParameters[2];
        deltaRho = inParameters[3];
        background = inParameters[4];
    }
 
    public double[] getParameters() {
        double[] outParameters = new double[5];
        outParameters[0] = scale;
        outParameters[1] = axisA;
        outParameters[2] = axisB;
        outParameters[3] = deltaRho;
        outParameters[4] = background;
        return outParameters;
    }
}