package sansmodels;

public class SquareWell extends SANSModel{
 
    private double radius, volumeFraction, depth, width, background;

    //Default constructor
    public SquareWell() {
        radius = 50.0;
        volumeFraction = 0.04;
        depth = 1.5;
        width = 1.2;
        setNumberOfParameters(4);
        String[] parameters = {"Radius (A)", "Vol Fraction (0-1)",
            "Well Depth (kT)","Well Width (diams)"};
        setParametersText(parameters);
    }

    public SquareWell(double inRadius, double inVolFrac, double inDepth,
                  double inWidth, double inBackground) {
        radius = inRadius;
        volumeFraction = inVolFrac;
        depth = inDepth;
        width = inWidth;
        background = inBackground;
        setNumberOfParameters(4);
        String[] parameters = {"Radius (A)", "Vol Fraction (0-1)",
            "Well Depth (kT)","Well Width (diams)"};
        setParametersText(parameters);
    }

    public double getFormFactor(double inX) {
        double sigma,eta,eta2,eta3,eta4,etam1,etam14,alpha,beta,gamma;
        double qvs,sk,sk2,sk3,sk4,t1,t2,t3,t4,ck;

        sigma = radius*2.;
        eta = volumeFraction;
        eta2 = eta*eta;
        eta3 = eta*eta2;
        eta4 = eta2*eta2;
        etam1 = 1.0 - eta;
        etam14 = etam1*etam1*etam1*etam1;
        alpha = (((1.0 + 2.0*eta)*(1.0 + 2.0*eta)) + eta3*(eta - 4.0))/etam14;
        beta = -1.0*(eta/3.0)*(18.0 + 20.0*eta - 12.0*eta2 +eta4)/etam14;
        gamma = alpha*0.5*eta;
        qvs = inX;
        sk = inX*sigma;
        sk2 = sk*sk;
        sk3 = sk*sk2;
        sk4 = sk2*sk2;
        t1 = alpha*sk3*(Math.sin(sk) - sk*Math.cos(sk));
        t2 = beta*sk2*(2.0*sk*Math.sin(sk) - (sk2-2.)*Math.cos(sk) - 2.0);
        t3 = (4.0* sk3 - 24.0*sk)*Math.sin(sk);
        t3 = t3 - (sk4 - (12.0*sk2) + 24.0)*Math.cos(sk) + 24.0;
        t3 = gamma*t3;
        t4 = -1.0*depth*sk3*(Math.sin(width*sk) - width*sk*Math.cos(width*sk)
             +sk*Math.cos(sk) - Math.sin(sk));
        ck = -24.0*eta*( t1 + t2 + t3 + t4 )/sk3/sk3;

        return 1.0/(1.0 - ck);
    }

    public void setParameters(double[] inParameters) {
        radius = inParameters[0];
        volumeFraction = inParameters[1];
        depth = inParameters[2];
        width = inParameters[3];
    }
 
    public double[] getParameters() {
        double[] outParameters = new double[4];
        outParameters[0] = radius;
        outParameters[1] = volumeFraction;
        outParameters[2] = depth;
        outParameters[3] = width;
        return outParameters;
    }
}