/*******************************************************************************
*
* McStas, neutron ray-tracing package
*         Copyright (C) 1997-2008, All rights reserved
*         Risoe National Laboratory, Roskilde, Denmark
*         Institut Laue Langevin, Grenoble, France
*
* Component: SasView_ellipsoid
*
* %Identification
* Written by: Jose Robledo
* Based on sasmodels from SasView
* Origin: FZJ / DTU / ESS DMSC
*
*
* SasView ellipsoid model component as sample description.
*
* %Description
*
* SasView_ellipsoid component, generated from ellipsoid.c in sasmodels.
*
* Example: 
*  SasView_ellipsoid(sld, sld_solvent, radius_polar, radius_equatorial, 
*     model_scale=1.0, model_abs=0.0, xwidth=0.01, yheight=0.01, zdepth=0.005, R=0, 
*     int target_index=1, target_x=0, target_y=0, target_z=1,
*     focus_xw=0.5, focus_yh=0.5, focus_aw=0, focus_ah=0, focus_r=0, 
*     pd_radius_polar=0.0, pd_radius_equatorial=0.0)
*
* %Parameters
* INPUT PARAMETERS:
* sld: [1e-6/Ang^2] ([-inf, inf]) Ellipsoid scattering length density.
* sld_solvent: [1e-6/Ang^2] ([-inf, inf]) Solvent scattering length density.
* radius_polar: [Ang] ([0, inf]) Polar radius.
* radius_equatorial: [Ang] ([0, inf]) Equatorial radius.
* Optional parameters:
* model_abs: [ ] Absorption cross section density at 2200 m/s.
* model_scale: [ ] Global scale factor for scattering kernel. For systems without inter-particle interference, the form factors can be related to the scattering intensity by the particle volume fraction.
* xwidth: [m] ([-inf, inf]) Horiz. dimension of sample, as a width.
* yheight: [m] ([-inf, inf]) vert . dimension of sample, as a height for cylinder/box
* zdepth: [m] ([-inf, inf]) depth of sample
* R: [m] Outer radius of sample in (x,z) plane for cylinder/sphere.
* target_x: [m] relative focus target position.
* target_y: [m] relative focus target position.
* target_z: [m] relative focus target position.
* target_index: [ ] Relative index of component to focus at, e.g. next is +1.
* focus_xw: [m] horiz. dimension of a rectangular area.
* focus_yh: [m], vert. dimension of a rectangular area.
* focus_aw: [deg], horiz. angular dimension of a rectangular area.
* focus_ah: [deg], vert. angular dimension of a rectangular area.
* focus_r: [m] case of circular focusing, focusing radius.
* pd_radius_polar: [] (0,inf) defined as (dx/x), where x is de mean value and dx the standard devition of the variable.
* pd_radius_equatorial: [] (0,inf) defined as (dx/x), where x is de mean value and dx the standard devition of the variable
*
* %Link
* %End
*******************************************************************************/
DEFINE COMPONENT SasView_ellipsoid

SETTING PARAMETERS (
        sld=4,
        sld_solvent=1,
        radius_polar=20,
        radius_equatorial=400,
        model_scale=1.0,
        model_abs=0.0,
        xwidth=0.01,
        yheight=0.01,
        zdepth=0.005,
        R=0,
        target_x=0,
        target_y=0,
        target_z=1,
        int target_index=1,
        focus_xw=0.5,
        focus_yh=0.5,
        focus_aw=0,
        focus_ah=0,
        focus_r=0,
        pd_radius_polar=0.0,
        pd_radius_equatorial=0.0)


SHARE %{
%include "sas_kernel_header.c"

/* BEGIN Required header for SASmodel ellipsoid */
#define HAS_Iqac
#define HAS_FQ
#define FORM_VOL

#ifndef SAS_HAVE_sas_3j1x_x
#define SAS_HAVE_sas_3j1x_x

#line 1 "sas_3j1x_x"
/**
* Spherical Bessel function 3*j1(x)/x
*
* Used for low q to avoid cancellation error.
* Note that the values differ from sasview ~ 5e-12 rather than 5e-14, but
* in this case it is likely cancellation errors in the original expression
* using double precision that are the source.
*/
double sas_3j1x_x(double q);

// The choice of the number of terms in the series and the cutoff value for
// switching between series and direct calculation depends on the numeric
// precision.
//
// Point where direct calculation reaches machine precision:
//
//   single machine precision eps 3e-8 at qr=1.1 **
//   double machine precision eps 4e-16 at qr=1.1
//
// Point where Taylor series reaches machine precision (eps), where taylor
// series matches direct calculation (cross) and the error at that point:
//
//   prec   n eps  cross  error
//   single 3 0.28  0.4   6.2e-7
//   single 4 0.68  0.7   2.3e-7
//   single 5 1.18  1.2   7.5e-8
//   double 3 0.01  0.03  2.3e-13
//   double 4 0.06  0.1   3.1e-14
//   double 5 0.16  0.2   5.0e-15
//
// ** Note: relative error on single precision starts increase on the direct
// method at qr=1.1, rising from 3e-8 to 5e-5 by qr=1e3.  This should be
// safe for the sans range, with objects of 100 nm supported to a q of 0.1
// while maintaining 5 digits of precision.  For usans/sesans, the objects
// are larger but the q is smaller, so again it should be fine.
//
// See explore/sph_j1c.py for code to explore these ranges.

// Use 4th order series
#if FLOAT_SIZE>4
#define SPH_J1C_CUTOFF 0.1
#else
#define SPH_J1C_CUTOFF 0.7
#endif
#pragma acc routine seq
double sas_3j1x_x(double q)
{
    // 2017-05-18 PAK - support negative q
    if (fabs(q) < SPH_J1C_CUTOFF) {
        const double q2 = q*q;
        return (1.0 + q2*(-3./30. + q2*(3./840. + q2*(-3./45360.))));// + q2*(3./3991680.)))));
    } else {
        double sin_q, cos_q;
        SINCOS(q, sin_q, cos_q);
        return 3.0*(sin_q/q - cos_q)/(q*q);
    }
}


#endif // SAS_HAVE_sas_3j1x_x


#ifndef SAS_HAVE_gauss76
#define SAS_HAVE_gauss76

#line 1 "gauss76"
// Created by Andrew Jackson on 4/23/07

 #ifdef GAUSS_N
 # undef GAUSS_N
 # undef GAUSS_Z
 # undef GAUSS_W
 #endif
 #define GAUSS_N 76
 #define GAUSS_Z Gauss76Z
 #define GAUSS_W Gauss76Wt

// Gaussians
constant double Gauss76Wt[76] = {
	.00126779163408536,		//0
	.00294910295364247,
	.00462793522803742,
	.00629918049732845,
	.00795984747723973,
	.00960710541471375,
	.0112381685696677,
	.0128502838475101,
	.0144407317482767,
	.0160068299122486,
	.0175459372914742,		//10
	.0190554584671906,
	.020532847967908,
	.0219756145344162,
	.0233813253070112,
	.0247476099206597,
	.026072164497986,
	.0273527555318275,
	.028587223650054,
	.029773487255905,
	.0309095460374916,		//20
	.0319934843404216,
	.0330234743977917,
	.0339977794120564,
	.0349147564835508,
	.0357728593807139,
	.0365706411473296,
	.0373067565423816,
	.0379799643084053,
	.0385891292645067,
	.0391332242205184,		//30
	.0396113317090621,
	.0400226455325968,
	.040366472122844,
	.0406422317102947,
	.0408494593018285,
	.040987805464794,
	.0410570369162294,
	.0410570369162294,
	.040987805464794,
	.0408494593018285,		//40
	.0406422317102947,
	.040366472122844,
	.0400226455325968,
	.0396113317090621,
	.0391332242205184,
	.0385891292645067,
	.0379799643084053,
	.0373067565423816,
	.0365706411473296,
	.0357728593807139,		//50
	.0349147564835508,
	.0339977794120564,
	.0330234743977917,
	.0319934843404216,
	.0309095460374916,
	.029773487255905,
	.028587223650054,
	.0273527555318275,
	.026072164497986,
	.0247476099206597,		//60
	.0233813253070112,
	.0219756145344162,
	.020532847967908,
	.0190554584671906,
	.0175459372914742,
	.0160068299122486,
	.0144407317482767,
	.0128502838475101,
	.0112381685696677,
	.00960710541471375,		//70
	.00795984747723973,
	.00629918049732845,
	.00462793522803742,
	.00294910295364247,
	.00126779163408536		//75 (indexed from 0)
};

constant double Gauss76Z[76] = {
	-.999505948362153,		//0
	-.997397786355355,
	-.993608772723527,
	-.988144453359837,
	-.981013938975656,
	-.972229228520377,
	-.961805126758768,
	-.949759207710896,
	-.936111781934811,
	-.92088586125215,
	-.904107119545567,		//10
	-.885803849292083,
	-.866006913771982,
	-.844749694983342,
	-.822068037328975,
	-.7980001871612,
	-.77258672828181,
	-.74587051350361,
	-.717896592387704,
	-.688712135277641,
	-.658366353758143,		//20
	-.626910417672267,
	-.594397368836793,
	-.560882031601237,
	-.526420920401243,
	-.491072144462194,
	-.454895309813726,
	-.417951418780327,
	-.380302767117504,
	-.342012838966962,
	-.303146199807908,		//30
	-.263768387584994,
	-.223945802196474,
	-.183745593528914,
	-.143235548227268,
	-.102483975391227,
	-.0615595913906112,
	-.0205314039939986,
	.0205314039939986,
	.0615595913906112,
	.102483975391227,			//40
	.143235548227268,
	.183745593528914,
	.223945802196474,
	.263768387584994,
	.303146199807908,
	.342012838966962,
	.380302767117504,
	.417951418780327,
	.454895309813726,
	.491072144462194,		//50
	.526420920401243,
	.560882031601237,
	.594397368836793,
	.626910417672267,
	.658366353758143,
	.688712135277641,
	.717896592387704,
	.74587051350361,
	.77258672828181,
	.7980001871612,	//60
	.822068037328975,
	.844749694983342,
	.866006913771982,
	.885803849292083,
	.904107119545567,
	.92088586125215,
	.936111781934811,
	.949759207710896,
	.961805126758768,
	.972229228520377,		//70
	.981013938975656,
	.988144453359837,
	.993608772723527,
	.997397786355355,
	.999505948362153		//75
};


#pragma acc declare copyin(Gauss76Wt[0:76], Gauss76Z[0:76])

#endif // SAS_HAVE_gauss76


#ifndef SAS_HAVE_ellipsoid
#define SAS_HAVE_ellipsoid

#line 1 "ellipsoid"
static double
form_volume_ellipsoid(double radius_polar, double radius_equatorial)
{
    return M_4PI_3*radius_polar*radius_equatorial*radius_equatorial;
}

static double
radius_from_volume_ellipsoid(double radius_polar, double radius_equatorial)
{
    return cbrt(radius_polar*radius_equatorial*radius_equatorial);
}

static double
radius_from_curvature_ellipsoid(double radius_polar, double radius_equatorial)
{
    // Trivial cases
    if (radius_polar == radius_equatorial) return radius_polar;
    if (radius_polar * radius_equatorial == 0.)  return 0.;

    // see equation (26) in A.Isihara, J.Chem.Phys. 18(1950)1446-1449
    const double ratio = (radius_polar < radius_equatorial
                          ? radius_polar / radius_equatorial
                          : radius_equatorial / radius_polar);
    const double e1 = sqrt(1.0 - ratio*ratio);
    const double b1 = 1.0 + asin(e1) / (e1 * ratio);
    const double bL = (1.0 + e1) / (1.0 - e1);
    const double b2 = 1.0 + 0.5 * ratio * ratio / e1 * log(bL);
    const double delta = 0.75 * b1 * b2;
    const double ddd = 2.0 * (delta + 1.0) * radius_polar * radius_equatorial * radius_equatorial;
    return 0.5 * cbrt(ddd);
}

static double
radius_effective_ellipsoid(int mode, double radius_polar, double radius_equatorial)
{
    switch (mode) {
    default:
    case 1: // average curvature
        return radius_from_curvature_ellipsoid(radius_polar, radius_equatorial);
    case 2: // equivalent volume sphere
        return radius_from_volume_ellipsoid(radius_polar, radius_equatorial);
    case 3: // min radius
        return (radius_polar < radius_equatorial ? radius_polar : radius_equatorial);
    case 4: // max radius
        return (radius_polar > radius_equatorial ? radius_polar : radius_equatorial);
    }
}


static void
Fq_ellipsoid(double q,
    double *F1,
    double *F2,
    double sld,
    double sld_solvent,
    double radius_polar,
    double radius_equatorial)
{
    // Using ratio v = Rp/Re, we can implement the form given in Guinier (1955)
    //     i(h) = int_0^pi/2 Phi^2(h a sqrt(cos^2 + v^2 sin^2) cos dT
    //          = int_0^pi/2 Phi^2(h a sqrt((1-sin^2) + v^2 sin^2) cos dT
    //          = int_0^pi/2 Phi^2(h a sqrt(1 + sin^2(v^2-1)) cos dT
    // u-substitution of
    //     u = sin, du = cos dT
    //     i(h) = int_0^1 Phi^2(h a sqrt(1 + u^2(v^2-1)) du
    const double v_square_minus_one = square(radius_polar/radius_equatorial) - 1.0;
    // translate a point in [-1,1] to a point in [0, 1]
    // const double u = GAUSS_Z[i]*(upper-lower)/2 + (upper+lower)/2;
    const double zm = 0.5;
    const double zb = 0.5;
    double total_F2 = 0.0;
    double total_F1 = 0.0;
    for (int i=0;i<GAUSS_N;i++) {
        const double u = GAUSS_Z[i]*zm + zb;
        const double r = radius_equatorial*sqrt(1.0 + u*u*v_square_minus_one);
        const double f = sas_3j1x_x(q*r);
        total_F2 += GAUSS_W[i] * f * f;
        total_F1 += GAUSS_W[i] * f;
    }
    // translate dx in [-1,1] to dx in [lower,upper]
    total_F1 *= zm;
    total_F2 *= zm;
    const double s = (sld - sld_solvent) * form_volume_ellipsoid(radius_polar, radius_equatorial);
    *F1 = 1e-2 * s * total_F1;
    *F2 = 1e-4 * s * s * total_F2;
}

static double
Iqac_ellipsoid(double qab, double qc,
    double sld,
    double sld_solvent,
    double radius_polar,
    double radius_equatorial)
{
    const double qr = sqrt(square(radius_equatorial*qab) + square(radius_polar*qc));
    const double f = sas_3j1x_x(qr);
    const double s = (sld - sld_solvent) * form_volume_ellipsoid(radius_polar, radius_equatorial);

    return 1.0e-4 * square(f * s);
}


#endif // SAS_HAVE_ellipsoid



/* END Required header for SASmodel ellipsoid */
%}
    DECLARE
%{
  double shape;
  double my_a_v;
%}

INITIALIZE
%{
shape=-1;  /* -1:no shape, 0:cyl, 1:box, 2:sphere  */
if (xwidth && yheight && zdepth)
    shape=1;
  else if (R > 0 && yheight)
    shape=0;
  else if (R > 0 && !yheight)
    shape=2;
  if (shape < 0)
    exit(fprintf(stderr, "SasView_model: %s: sample has invalid dimensions.\n"
                         "ERROR     Please check parameter values.\n", NAME_CURRENT_COMP));

  /* now compute target coords if a component index is supplied */
  if (!target_index && !target_x && !target_y && !target_z) target_index=1;
  if (target_index)
  {
    Coords ToTarget;
    ToTarget = coords_sub(POS_A_COMP_INDEX(INDEX_CURRENT_COMP+target_index),POS_A_CURRENT_COMP);
    ToTarget = rot_apply(ROT_A_CURRENT_COMP, ToTarget);
    coords_get(ToTarget, &target_x, &target_y, &target_z);
  }

  if (!(target_x || target_y || target_z)) {
    printf("SasView_model: %s: The target is not defined. Using direct beam (Z-axis).\n",
      NAME_CURRENT_COMP);
    target_z=1;
  }

  my_a_v = model_abs*2200*100; /* Is not yet divided by v. 100: Convert barns -> fm^2 */

%}


TRACE
%{
  double t0, t1, v, l_full, l, l_1, dt, d_phi, my_s;
  double aim_x=0, aim_y=0, aim_z=1, axis_x, axis_y, axis_z;
  double arg, tmp_vx, tmp_vy, tmp_vz, vout_x, vout_y, vout_z;
  double f, solid_angle, vx_i, vy_i, vz_i, q, qx, qy, qz;
  char intersect=0;

  /* Intersection neutron trajectory / sample (sample surface) */
  if (shape == 0){
    intersect = cylinder_intersect(&t0, &t1, x, y, z, vx, vy, vz, R, yheight);}
  else if (shape == 1){
    intersect = box_intersect(&t0, &t1, x, y, z, vx, vy, vz, xwidth, yheight, zdepth);}
  else if (shape == 2){
    intersect = sphere_intersect(&t0, &t1, x, y, z, vx, vy, vz, R);}
  if(intersect)
  {
    if(t0 < 0)
      ABSORB;

    /* Neutron enters at t=t0. */
    v = sqrt(vx*vx + vy*vy + vz*vz);
    l_full = v * (t1 - t0);          /* Length of full path through sample */
    dt = rand01()*(t1 - t0) + t0;    /* Time of scattering */
    PROP_DT(dt);                     /* Point of scattering */
    l = v*(dt-t0);                   /* Penetration in sample */

    vx_i=vx;
    vy_i=vy;
    vz_i=vz;
    if ((target_x || target_y || target_z)) {
      aim_x = target_x-x;            /* Vector pointing at target (anal./det.) */
      aim_y = target_y-y;
      aim_z = target_z-z;
    }
    if(focus_aw && focus_ah) {
      randvec_target_rect_angular(&vx, &vy, &vz, &solid_angle,
        aim_x, aim_y, aim_z, focus_aw, focus_ah, ROT_A_CURRENT_COMP);
    } else if(focus_xw && focus_yh) {
      randvec_target_rect(&vx, &vy, &vz, &solid_angle,
        aim_x, aim_y, aim_z, focus_xw, focus_yh, ROT_A_CURRENT_COMP);
    } else {
      randvec_target_circle(&vx, &vy, &vz, &solid_angle, aim_x, aim_y, aim_z, focus_r);
    }
    NORM(vx, vy, vz);
    vx *= v;
    vy *= v;
    vz *= v;
    qx = V2K*(vx_i-vx);
    qy = V2K*(vy_i-vy);
    qz = V2K*(vz_i-vz);
    q = sqrt(qx*qx+qy*qy+qz*qz);
    
    double trace_radius_polar=radius_polar;
    double trace_radius_equatorial=radius_equatorial;
    if ( pd_radius_polar!=0.0 || pd_radius_equatorial!=0.0 ){
    trace_radius_polar = (randnorm()*pd_radius_polar+1.0)*radius_polar;
    trace_radius_equatorial = (randnorm()*pd_radius_equatorial+1.0)*radius_equatorial;
    }

        


    // Sample dependent. Retrieved from SasView./////////////////////
    float Iq_out;
    Iq_out = 1;

    double F1=0.0, F2=0.0;
    Fq_ellipsoid(q, &F1, &F2, sld, sld_solvent, trace_radius_polar, trace_radius_equatorial);
    Iq_out = F2;


    float vol;
    vol = 1;

    // Scale by 1.0E2 [SasView: 1/cm  ->   McStas: 1/m]
    Iq_out = model_scale*Iq_out / vol * 1.0E2;

    l_1 = v*t1;
    p *= l_full*solid_angle/(4*PI)*Iq_out*exp(-my_a_v*(l+l_1)/v);
    SCATTER;
  }
%}

MCDISPLAY
%{

  if (shape == 0) {	/* cylinder */
    circle("xz", 0,  yheight/2.0, 0, R);
    circle("xz", 0, -yheight/2.0, 0, R);
    line(-R, -yheight/2.0, 0, -R, +yheight/2.0, 0);
    line(+R, -yheight/2.0, 0, +R, +yheight/2.0, 0);
    line(0, -yheight/2.0, -R, 0, +yheight/2.0, -R);
    line(0, -yheight/2.0, +R, 0, +yheight/2.0, +R);
  }
  else if (shape == 1) { 	/* box */
    double xmin = -0.5*xwidth;
    double xmax =  0.5*xwidth;
    double ymin = -0.5*yheight;
    double ymax =  0.5*yheight;
    double zmin = -0.5*zdepth;
    double zmax =  0.5*zdepth;
    multiline(5, xmin, ymin, zmin,
                 xmax, ymin, zmin,
                 xmax, ymax, zmin,
                 xmin, ymax, zmin,
                 xmin, ymin, zmin);
    multiline(5, xmin, ymin, zmax,
                 xmax, ymin, zmax,
                 xmax, ymax, zmax,
                 xmin, ymax, zmax,
                 xmin, ymin, zmax);
    line(xmin, ymin, zmin, xmin, ymin, zmax);
    line(xmax, ymin, zmin, xmax, ymin, zmax);
    line(xmin, ymax, zmin, xmin, ymax, zmax);
    line(xmax, ymax, zmin, xmax, ymax, zmax);
  }
  else if (shape == 2) {	/* sphere */
    circle("xy", 0,  0.0, 0, R);
    circle("xz", 0,  0.0, 0, R);
    circle("yz", 0,  0.0, 0, R);
  }
%}
END