/*******************************************************************************
*
* McXtrace, X-ray tracing package
*         Copyright, All rights reserved
*         DTU Physics, Kgs. Lyngby, Denmark
*         Synchrotron SOLEIL, Saint-Aubin, France
*
* Component: SasView_multilayer_vesicle
*
* %Identification
* Written by: Jose Robledo
* Based on sasmodels from SasView
* Origin: FZJ / DTU / ESS DMSC
*
*
* SasView multilayer_vesicle model component as sample description.
*
* %Description
*
* SasView_multilayer_vesicle component, generated from multilayer_vesicle.c in sasmodels.
*
* Example: 
*  SasView_multilayer_vesicle(volfraction, radius, thick_shell, thick_solvent, sld_solvent, sld, n_shells, 
*     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=0.0, pd_thick_shell=0.0, pd_thick_solvent=0.0)
*
* %Parameters
* INPUT PARAMETERS:
* volfraction: [] ([0.0, 1]) volume fraction of vesicles.
* radius: [Ang] ([0.0, inf]) radius of solvent filled core.
* thick_shell: [Ang] ([0.0, inf]) thickness of one shell.
* thick_solvent: [Ang] ([0.0, inf]) solvent thickness between shells.
* sld_solvent: [1e-6/Ang^2] ([-inf, inf]) solvent scattering length density.
* sld: [1e-6/Ang^2] ([-inf, inf]) Shell scattering length density.
* n_shells: [] ([1.0, inf]) Number of shell plus solvent layer pairs (must be integer).
* 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: [] (0,inf) defined as (dx/x), where x is de mean value and dx the standard devition of the variable.
* pd_thick_shell: [] (0,inf) defined as (dx/x), where x is de mean value and dx the standard devition of the variable.
* pd_thick_solvent: [] (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_multilayer_vesicle

SETTING PARAMETERS (
        volfraction=0.05,
        radius=60.0,
        thick_shell=10.0,
        thick_solvent=10.0,
        sld_solvent=6.4,
        sld=0.4,
        n_shells=2.0,
        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=0.0,
        pd_thick_shell=0.0,
        pd_thick_solvent=0.0)


SHARE %{
%include "sas_kernel_header.c"

/* BEGIN Required header for SASmodel multilayer_vesicle */
#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_multilayer_vesicle
#define SAS_HAVE_multilayer_vesicle

#line 1 "multilayer_vesicle"
static double
form_volume_multilayer_vesicle(double radius,
          double thick_shell,
          double thick_solvent,
          double fp_n_shells)
{
    int n_shells = (int)(fp_n_shells + 0.5);
    double R_N = radius + n_shells*(thick_shell+thick_solvent) - thick_solvent;
    return M_4PI_3*cube(R_N);
}

static double
multilayer_vesicle_kernel(double q,
          double radius,
          double thick_shell,
          double thick_solvent,
          double sld_solvent,
          double sld,
          int n_shells)
{
    //calculate with a loop, two shells at a time
    int ii = 0;
    double fval = 0.0;
    double voli = 0.0;
    const double sldi = sld_solvent-sld;

    do {
        double ri = radius + (double)ii*(thick_shell + thick_solvent);

        // layer 1
        voli = M_4PI_3*ri*ri*ri;
        fval += voli*sldi*sas_3j1x_x(ri*q);

        ri += thick_shell;

        // layer 2
        voli = M_4PI_3*ri*ri*ri;
        fval -= voli*sldi*sas_3j1x_x(ri*q);

        //do 2 layers at a time
        ii++;

    } while(ii <= n_shells-1);  //change to make 0 < n_shells < 2 correspond to
                               //unilamellar vesicles (C. Glinka, 11/24/03)

    return fval;  // Volume normalization happens in caller
}

static double
radius_effective_multilayer_vesicle(int mode, double radius, double thick_shell, double thick_solvent, double fp_n_shells)
{
    // case 1: outer radius
    return radius + fp_n_shells*thick_shell + (fp_n_shells - 1.0)*thick_solvent;
}

static void
Fq_multilayer_vesicle(double q,
          double *F1,
          double *F2,
          double volfraction,
          double radius,
          double thick_shell,
          double thick_solvent,
          double sld_solvent,
          double sld,
          double fp_n_shells)
{
    int n_shells = (int)(fp_n_shells + 0.5);
    const double fq = multilayer_vesicle_kernel(q,
           radius,
           thick_shell,
           thick_solvent,
           sld_solvent,
           sld,
           n_shells);
    // See comment in vesicle.c regarding volfraction normalization.
    *F1 = 1.0e-2 * sqrt(volfraction)*fq;
    *F2 = 1.0e-4 * volfraction*fq*fq;
}



#endif // SAS_HAVE_multilayer_vesicle



/* END Required header for SASmodel multilayer_vesicle */
%}
    DECLARE
%{
  double shape;
  double my_a_k;
%}

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;
  }

  /*TODO fix absorption*/
  my_a_k = model_abs; /* assume absorption is given in 1/m */
%}


TRACE
%{
  double l0, l1, k, l_full, l, dl, d_Phi;
  double aim_x = 0, aim_y = 0, aim_z = 1, axis_x, axis_y, axis_z;
  double f, solid_angle, kx_i, ky_i, kz_i, q, qx, qy, qz;
  char intersect = 0;

  /* Intersection photon trajectory / sample (sample surface) */
  if (shape == 0) {
    intersect = cylinder_intersect (&l0, &l1, x, y, z, kx, ky, kz, R, yheight);
  } else if (shape == 1) {
    intersect = box_intersect (&l0, &l1, x, y, z, kx, ky, kz, xwidth, yheight, zdepth);
  } else if (shape == 2) {
    intersect = sphere_intersect (&l0, &l1, x, y, z, kx, ky, kz, R);
  }
  if (intersect) {
    if (l0 < 0)
      ABSORB;

    /* Photon enters at l0. */
    k = sqrt (kx * kx + ky * ky + kz * kz);
    l_full = (l1 - l0);              /* Length of full path through sample */
    dl = rand01 () * (l1 - l0) + l0; /* Point of scattering */
    PROP_DL (dl);                    /* Point of scattering */
    l = (dl - l0);                   /* Penetration in sample */

    kx_i = kx;
    ky_i = ky;
    kz_i = kz;
    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 (&kx, &ky, &kz, &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 (&kx, &ky, &kz, &solid_angle, aim_x, aim_y, aim_z, focus_xw, focus_yh, ROT_A_CURRENT_COMP);
    } else {
      randvec_target_circle (&kx, &ky, &kz, &solid_angle, aim_x, aim_y, aim_z, focus_r);
    }
    NORM (kx, ky, kz);
    kx *= k;
    ky *= k;
    kz *= k;
    qx = (kx_i - kx);
    qy = (ky_i - ky);
    qz = (kz_i - kz);
    q = sqrt (qx * qx + qy * qy + qz * qz);

    double trace_radius = radius;
    double trace_thick_shell = thick_shell;
    double trace_thick_solvent = thick_solvent;
    if (pd_radius != 0.0 || pd_thick_shell != 0.0 || pd_thick_solvent != 0.0) {
      trace_radius = (randnorm () * pd_radius + 1.0) * radius;
      trace_thick_shell = (randnorm () * pd_thick_shell + 1.0) * thick_shell;
      trace_thick_solvent = (randnorm () * pd_thick_solvent + 1.0) * thick_solvent;
    }

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

    double F1 = 0.0, F2 = 0.0;
    Fq_multilayer_vesicle (q, &F1, &F2, volfraction, trace_radius, trace_thick_shell, trace_thick_solvent, sld_solvent, sld, n_shells);
    Iq_out = F2;

    float vol;
    vol = 1;

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

    p *= l_full * solid_angle / (4 * PI) * Iq_out * exp (-my_a_k * (l + l1));

    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

