package sansmodels;

public class Cylinder extends SANSModel{
 
    private double scale, radius, length, deltaRho, background;

    //Default constructor
    public Cylinder() {
        scale = 1.0;
        radius = 20.0;
        length = 400.0;
        deltaRho = 3.e-6;
        background = 0.0;
        setNumberOfParameters(5);
        String[] parameters = {"Scale", "Radius (A)",
            "Length (A)", "Contrast (A-2)", "Background (cm-1)"};
        setParametersText(parameters);                                          
    }

    public Cylinder(double inScale, 
                     double inRadius,
                     double inLength,
                     double inContrast,
                     double inBackground) {
        scale = inScale; 
        radius = inRadius;
        length = inLength;
        deltaRho = inContrast;
        background = inBackground;
        setNumberOfParameters(5);
        String[] parameters = {"Scale", "Radius (A)",
            "Length (A)", "Contrast (A-2)", "Background (cm-1)"};
        setParametersText(parameters);                                          
    }

    private double cylinderFunc(double inQ, double inZ) {
        double bessarg, bj, d1, t1, b1, t2, b2;
        
        bessarg = inQ * radius * Math.sin(inZ);
        bj = SpecialFunction.j1(bessarg);

        d1 = Math.sin(inQ * length/2.0 * Math.cos(inZ));
        t1 = d1 * d1;
        
        d1 = bj;
        t2 = d1 * d1 * 4.0 * Math.sin(inZ);
       
        d1 = inQ * length/2.0 * Math.cos(inZ);
        b1 = d1 *d1;
       
        d1 = inQ * radius * Math.sin(inZ);
        b2 = d1 * d1;
        
        return t1*t2/b1/b2;

    }
 
    public double getFormFactor(double inX) {

        int nord = 76;
        double va, vb, summ, zi, answer, yyy;
        double vol;
        va = 0.0;
        vb = Math.PI/2.0;
        

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

        answer *= deltaRho*deltaRho;
        
        vol = Math.PI*radius*radius*length;
        return answer*vol*1.0e8*scale*getStructureFactor().calculate(inX) 
            + background;
    }

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