use super::{fw2m, nut06a, pfw06};

///  Classical NPB matrix, IAU 2006/2000A

///

///  Form the matrix of precession-nutation for a given date (including

///  frame bias), equinox based, IAU 2006 precession and IAU 2000A

///  nutation models.

///

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

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

///

///  Status:  support function.

///

///  Given:

///  ```

///     date1,date2 double       TT as a 2-part Julian Date (Note 1)

///  ```

///  Returned:

///  ```

///     rbpn        double[3][3] bias-precession-nutation matrix (Note 2)

///  ```

///  Notes:

///

///  1) The TT date date1+date2 is a Julian Date, apportioned in any

///     convenient way between the two arguments.  For example,

///     JD(TT)=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.

///

///  2) The matrix operates in the sense V(date) = rbpn * V(GCRS), where

///     the p-vector V(date) is with respect to the true equatorial triad

///     of date date1+date2 and the p-vector V(GCRS) is with respect to

///     the Geocentric Celestial Reference System (IAU, 2000).

///

///  Called:

///     iauPfw06     bias-precession F-W angles, IAU 2006

///     iauNut06a    nutation, IAU 2006/2000A

///     iauFw2m      F-W angles to r-matrix

///

///  Reference:

///

///     Capitaine, N. & Wallace, P.T., 2006, Astron.Astrophys. 450, 855.

pub fn pnm06a(date1: f64, date2: f64) -> [[f64; 3]; 3] {

    /* Fukushima-Williams angles for frame bias and precession. */

    let (gamb, phib, psib, epsa) = pfw06(date1, date2);

    /* Nutation components. */

    let (dp, de) = nut06a(date1, date2);

    /* Equinox based nutation x precession x bias matrix. */

    fw2m(gamb, phib, psib + dp, epsa + de)

}