rfa 0.5.9

use crate::UrsaASTROM;
use crate::prec_nut::s06::s06;
use crate::ephemerides::epv00::epv00;
use crate::prec_nut::pnm06a::pnm06a;
use crate::prec_nut::bpn2xy::bpn2xy;
use super::apci::apci;
use crate::prec_nut::eors::eors;
/*
**  - - - - - - - - - -
**   e r a A p c i 1 3
**  - - - - - - - - - -
**
**  For a terrestrial observer, prepare star-independent astrometry
**  parameters for transformations between ICRS and geocentric CIRS
**  coordinates.  The caller supplies the date, and ERFA models are used
**  to predict the Earth ephemeris and CIP/CIO.
**
**  The parameters produced by this function are required in the
**  parallax, light deflection, aberration, and bias-precession-nutation
**  parts of the astrometric transformation chain.
**
**  Given:
**     date1  double      TDB as a 2-part...
**     date2  double      ...Julian Date (Note 1)
**
**  Returned:
**     astrom eraASTROM*  star-independent astrometry parameters:
**      pmt    double       PM time interval (SSB, Julian years)
**      eb     double[3]    SSB to observer (vector, au)
**      eh     double[3]    Sun to observer (unit vector)
**      em     double       distance from Sun to observer (au)
**      v      double[3]    barycentric observer velocity (vector, c)
**      bm1    double       sqrt(1-|v|^2): reciprocal of Lorenz factor
**      bpn    double[3][3] bias-precession-nutation matrix
**      along  double       unchanged
**      xpl    double       unchanged
**      ypl    double       unchanged
**      sphi   double       unchanged
**      cphi   double       unchanged
**      diurab double       unchanged
**      eral   double       unchanged
**      refa   double       unchanged
**      refb   double       unchanged
**     eo     double*     equation of the origins (ERA-GST)
**
**  Notes:
**
**  1) The TDB date date1+date2 is a Julian Date, apportioned in any
**     convenient way between the two arguments.  For example,
**     JD(TDB)=2450123.7 could be expressed in any of these ways, among
**     others:
**
**            date1          date2
**
**         2450123.7           0.0       (JD method)
**         2451545.0       -1421.3       (J2000 method)
**         2400000.5       50123.2       (MJD method)
**         2450123.5           0.2       (date & time method)
**
**     The JD method is the most natural and convenient to use in cases
**     where the loss of several decimal digits of resolution is
**     acceptable.  The J2000 method is best matched to the way the
**     argument is handled internally and will deliver the optimum
**     resolution.  The MJD method and the date & time methods are both
**     good compromises between resolution and convenience.  For most
**     applications of this function the choice will not be at all
**     critical.
**
**     TT can be used instead of TDB without any significant impact on
**     accuracy.
**
**  2) All the vectors are with respect to BCRS axes.
**
**  3) In cases where the caller wishes to supply his own Earth
**     ephemeris and CIP/CIO, the function eraApci can be used instead
**     of the present function.
**
**  4) This is one of several functions that inserts into the astrom
**     structure star-independent parameters needed for the chain of
**     astrometric transformations ICRS <-> GCRS <-> CIRS <-> observed.
**
**     The various functions support different classes of observer and
**     portions of the transformation chain:
**
**          functions         observer        transformation
**
**       eraApcg eraApcg13    geocentric      ICRS <-> GCRS
**       eraApci eraApci13    terrestrial     ICRS <-> CIRS
**       eraApco eraApco13    terrestrial     ICRS <-> observed
**       eraApcs eraApcs13    space           ICRS <-> GCRS
**       eraAper eraAper13    terrestrial     update Earth rotation
**       eraApio eraApio13    terrestrial     CIRS <-> observed
**
**     Those with names ending in "13" use contemporary ERFA models to
**     compute the various ephemerides.  The others accept ephemerides
**     supplied by the caller.
**
**     The transformation from ICRS to GCRS covers space motion,
**     parallax, light deflection, and aberration.  From GCRS to CIRS
**     comprises frame bias and precession-nutation.  From CIRS to
**     observed takes account of Earth rotation, polar motion, diurnal
**     aberration and parallax (unless subsumed into the ICRS <-> GCRS
**     transformation), and atmospheric refraction.
**
**  5) The context structure astrom produced by this function is used by
**     eraAtciq* and eraAticq*.
**
**  Called:
**     eraEpv00     Earth position and velocity
**     eraPnm06a    classical NPB matrix, IAU 2006/2000A
**     eraBpn2xy    extract CIP X,Y coordinates from NPB matrix
**     eraS06       the CIO locator s, given X,Y, IAU 2006
**     eraApci      astrometry parameters, ICRS-CIRS
**     eraEors      equation of the origins, given NPB matrix and s
**
**  This revision:   2013 October 9
**
**  Copyright (C) 2013-2021, NumFOCUS Foundation.
**  Derived, with permission, from the SOFA library.  See notes at end of file.
*/
pub fn apci13(date1:f64, date2:f64,
    astrom: &mut UrsaASTROM, eo: &mut f64)
{

   let mut x = 0.0;
   let mut y = 0.0;
   let mut ehpv  = [[0.0; 3]; 2];
   let mut ebpv = [[0.0; 3]; 2];
   let mut r = [[0.0; 3]; 3];

/* Earth barycentric & heliocentric position/velocity (au, au/d). */
   epv00(date1, date2, &mut ehpv, &mut ebpv);

/* Form the equinox based BPN matrix, IAU 2006/2000A. */
   pnm06a(date1, date2, &mut r);

/* Extract CIP X,Y. */
   bpn2xy(&r, &mut x, &mut y);

/* Obtain CIO locator s. */
   let s = s06(date1, date2, x, y);

/* Compute the star-independent astrometry parameters. */
   apci(date1, date2, &ebpv, &ehpv[0], x, y, s, astrom);

/* Equation of the origins. */
   *eo = eors(&r, s);

/* Finished. */

}