use crate::vm::{ir, rx, rz};

///  Form the matrix of nutation.

///

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

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

///

///  Status:  support function.

///

///  Given:

///     epsa        double         mean obliquity of date (Note 1)

///     dpsi,deps   double         nutation (Note 2)

///

///  Returned (function value):

///                 [[f64; 3]; 3]   nutation matrix (Note 3)

///

///  Notes:

///

///

///  1) The supplied mean obliquity epsa, must be consistent with the

///     precession-nutation models from which dpsi and deps were obtained.

///

///  2) The caller is responsible for providing the nutation components;

///     they are in longitude and obliquity, in radians and are with

///     respect to the equinox and ecliptic of date.

///

///  3) The matrix operates in the sense V(true) = rmatn * V(mean),

///     where the p-vector V(true) is with respect to the true

///     equatorial triad of date and the p-vector V(mean) is with

///     respect to the mean equatorial triad of date.

///

///  Called:

///     iauIr        initialize r-matrix to identity

///     iauRx        rotate around X-axis

///     iauRz        rotate around Z-axis

///

///  Reference:

///

///     Explanatory Supplement to the Astronomical Almanac,

///     P. Kenneth Seidelmann (ed), University Science Books (1992),

///     Section 3.222-3 (p114).

///

///  This revision:  2021 May 11

///

///  SOFA release 2023-10-11

///

///  Copyright (C) 2023 IAU SOFA Board.  See notes at end.

///

pub fn numat(epsa: f64, dpsi: f64, deps: f64) -> [[f64; 3]; 3] {

    let mut rmatn = [[0.0; 3]; 3];

    ir(&mut rmatn);

    rx(epsa, &mut rmatn);

    rz(-dpsi, &mut rmatn);

    rx(-(epsa + deps), &mut rmatn);

    rmatn

}