use crate::vm::{anp, c2s, rxp, s2c};

use super::{IauAstrom, ab, ldsun};

///  Quick astrometric ICRS −> CIRS

///

///  Quick ICRS to CIRS transformation, given precomputed star-

///  independent astrometry parameters, and assuming zero parallax and

///  proper motion.

///

///  Use of this function is appropriate when efficiency is important and

///  where many star positions are to be transformed for one date.  The

///  star-independent parameters can be obtained by calling one of the

///  functions iauApci[13], iauApcg[13], iauApco[13] or iauApcs[13].

///

///  The corresponding function for the case of non-zero parallax and

///  proper motion is iauAtciq.

///

///  This function is part of the International Astronomical Union's

///  SOFA (Standards of Fundamental Astronomy) software collection.

///

///  Status:  support function.

///

///  Given:

///  ```

///     rc,dc  double     ICRS astrometric RA,Dec (radians)

///     astrom iauASTROM* 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       longitude + s' (radians)

///      xpl    double       polar motion xp wrt local meridian (radians)

///      ypl    double       polar motion yp wrt local meridian (radians)

///      sphi   double       sine of geodetic latitude

///      cphi   double       cosine of geodetic latitude

///      diurab double       magnitude of diurnal aberration vector

///      eral   double       "local" Earth rotation angle (radians)

///      refa   double       refraction constant A (radians)

///      refb   double       refraction constant B (radians)

///  ```

///  Returned:

///  ```

///     ri,di  double     CIRS RA,Dec (radians)

///  ```

///  Note:

///

///     All the vectors are with respect to BCRS axes.

///

///  References:

///

///     Urban, S. & Seidelmann, P. K. (eds), Explanatory Supplement to

///     the Astronomical Almanac, 3rd ed., University Science Books

///     (2013).

///

///     Klioner, Sergei A., "A practical relativistic model for micro-

///     arcsecond astrometry in space", Astr. J. 125, 1580-1597 (2003).

///

///  Called:

///  ```

///     iauS2c       spherical coordinates to unit vector

///     iauLdsun     light deflection due to Sun

///     iauAb        stellar aberration

///     iauRxp       product of r-matrix and p-vector

///     iauC2s       p-vector to spherical

///     iauAnp       normalize angle into range +/- pi

///  ```

pub fn atciqz(rc: f64, dc: f64, astrom: &mut IauAstrom) -> (f64, f64) {

    /* BCRS coordinate direction (unit vector). */

    let pco = s2c(rc, dc);

    /* Light deflection by the Sun, giving BCRS natural direction. */

    let pnat = ldsun(pco, astrom.eh, astrom.em);

    /* Aberration, giving GCRS proper direction. */

    let ppr = ab(&pnat, &astrom.v, astrom.em, astrom.bm1);

    /* Bias-precession-nutation, giving CIRS proper direction. */

    let mut pi = [0.0; 3];

    rxp(&astrom.bpn, &ppr, &mut pi);

    /* CIRS RA,Dec. */

    let (w, di) = c2s(&pi);

    let ri = anp(w);

    (ri, di)

}