use super::{gmst06, gst06a};

use crate::vm::anpm;

///  Equation of the equinoxes, IAU 2006/2000A

///

///  Equation of the equinoxes, compatible with IAU 2000 resolutions and

///  IAU 2006/2000A precession-nutation.

///

///  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 (function value):

///  ```

///                  double    equation of the equinoxes (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 result, which is in radians, operates in the following sense:

///

///        Greenwich apparent ST = GMST + equation of the equinoxes

///

///  Called:

///  ```

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

///     iauGst06a    Greenwich apparent sidereal time, IAU 2006/2000A

///     iauGmst06    Greenwich mean sidereal time, IAU 2006

///  ```

///  Reference:

///

///     McCarthy, D. D., Petit, G. (eds.), 2004, IERS Conventions (2003),

///     IERS Technical Note No. 32, BKG

pub fn ee06a(date1: f64, date2: f64) -> f64 {

    let _gst06a = gst06a(0.0, 0.0, date1, date2);

    let _gmst06 = gmst06(0.0, 0.0, date1, date2);

    // Equation of the equinoxes.

    let ee = anpm(_gst06a - _gmst06);

    ee

}