use crate::{

    consts::{DAU, DAYSEC, DC, DJY, DR2AS},

    vm::{pdp, pm, pmp, pn, ppp, s2pv, sxp, zp},

};

///  Convert star catalog coordinates to position+velocity vector.

///

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

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

///

///  Status:  support function.

///

///  Given (Note 1):

///     ra     double        right ascension (radians)

///     dec    double        declination (radians)

///     pmr    double        RA proper motion (radians/year)

///     pmd    double        Dec proper motion (radians/year)

///     px     double        parallax (arcseconds)

///     rv     double        radial velocity (km/s, positive = receding)

///

///  Returned (Note 2):

///     pv     double[2][3]  pv-vector (au, au/day)

///

///  Returned (function value):

///            int           status:

///                              0 = no warnings

///                              1 = distance overridden (Note 6)

///                              2 = excessive speed (Note 7)

///                              4 = solution didn't converge (Note 8)

///                           else = binary logical OR of the above

///

///  Notes:

///

///  1) The star data accepted by this function are "observables" for an

///     imaginary observer at the solar-system barycenter.  Proper motion

///     and radial velocity are, strictly, in terms of barycentric

///     coordinate time, TCB.  For most practical applications, it is

///     permissible to neglect the distinction between TCB and ordinary

///     "proper" time on Earth (TT/TAI).  The result will, as a rule, be

///     limited by the intrinsic accuracy of the proper-motion and

///     radial-velocity data;  moreover, the pv-vector is likely to be

///     merely an intermediate result, so that a change of time unit

///     would cancel out overall.

///

///     In accordance with normal star-catalog conventions, the object's

///     right ascension and declination are freed from the effects of

///     secular aberration.  The frame, which is aligned to the catalog

///     equator and equinox, is Lorentzian and centered on the SSB.

///

///  2) The resulting position and velocity pv-vector is with respect to

///     the same frame and, like the catalog coordinates, is freed from

///     the effects of secular aberration.  Should the "coordinate

///     direction", where the object was located at the catalog epoch, be

///     required, it may be obtained by calculating the magnitude of the

///     position vector pv[0][0-2] dividing by the speed of light in

///     au/day to give the light-time, and then multiplying the space

///     velocity pv[1][0-2] by this light-time and adding the result to

///     pv[0][0-2].

///

///     Summarizing, the pv-vector returned is for most stars almost

///     identical to the result of applying the standard geometrical

///     "space motion" transformation.  The differences, which are the

///     subject of the Stumpff paper referenced below, are:

///

///     (i) In stars with significant radial velocity and proper motion,

///     the constantly changing light-time distorts the apparent proper

///     motion.  Note that this is a classical, not a relativistic,

///     effect.

///

///     (ii) The transformation complies with special relativity.

///

///  3) Care is needed with units.  The star coordinates are in radians

///     and the proper motions in radians per Julian year, but the

///     parallax is in arcseconds; the radial velocity is in km/s, but

///     the pv-vector result is in au and au/day.

///

///  4) The RA proper motion is in terms of coordinate angle, not true

///     angle.  If the catalog uses arcseconds for both RA and Dec proper

///     motions, the RA proper motion will need to be divided by cos(Dec)

///     before use.

///

///  5) Straight-line motion at constant speed, in the inertial frame,

///     is assumed.

///

///  6) An extremely small (or zero or negative) parallax is interpreted

///     to mean that the object is on the "celestial sphere", the radius

///     of which is an arbitrary (large) value (see the constant PXMIN).

///     When the distance is overridden in this way, the status,

///     initially zero, has 1 added to it.

///

///  7) If the space velocity is a significant fraction of c (see the

///     constant VMAX), it is arbitrarily set to zero.  When this action

///     occurs, 2 is added to the status.

///

///  8) The relativistic adjustment involves an iterative calculation.

///     If the process fails to converge within a set number (IMAX) of

///     iterations, 4 is added to the status.

///

///  9) The inverse transformation is performed by the function

///     iauPvstar.

///

///  Called:

///     iauS2pv      spherical coordinates to pv-vector

///     iauPm        modulus of p-vector

///     iauZp        zero p-vector

///     iauPn        decompose p-vector into modulus and direction

///     iauPdp       scalar product of two p-vectors

///     iauSxp       multiply p-vector by scalar

///     iauPmp       p-vector minus p-vector

///     iauPpp       p-vector plus p-vector

///

///  Reference:

///

///     Stumpff, P., 1985, Astron.Astrophys. 144, 232-240.

///

///  This revision:  2023 May 4

///

///  SOFA release 2023-10-11

///

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

///

pub fn starpv(

    ra: f64,

    dec: f64,

    pmr: f64,

    pmd: f64,

    px: f64,

    rv: f64,

) -> ([[f64; 3]; 2], i32) {

    /* Smallest allowed parallax */

    const PXMIN: f64 = 1e-7;

    /* Largest allowed speed (fraction of c) */

    const VMAX: f64 = 0.5;

    /* Maximum number of iterations for relativistic solution */

    const IMAX: i32 = 100;

    let mut i: i32 = 0;

    let mut iwarn: i32;

    let mut w: f64;

    let (r, rd, rad, decd, v, vsr, vst): (f64, f64, f64, f64, f64, f64, f64);

    let (betst, betsr, mut bett, mut betr, mut dd, mut ddel): (f64, f64, f64, f64, f64, f64);

    let (mut d, mut del, mut odd, mut oddel, mut od, mut odel) = (0.0, 0.0, 0.0, 0.0, 0.0, 0.0);

    // Distance (au).

    if px >= PXMIN {

        w = px;

        iwarn = 0;

    } else {

        w = PXMIN;

        iwarn = 1;

    }

    r = DR2AS / w;

    // Radial speed (au/day).

    rd = DAYSEC * rv * 1e3 / DAU;

    // Proper motion (radian/day).

    rad = pmr / DJY;

    decd = pmd / DJY;

    // To pv-vector (au, au/day).

    let mut pv = s2pv(ra, dec, r, rad, decd, rd);

    // If excessive velocity, arbitrarily set it to zero.

    v = pm(pv[1]);

    if v / DC > VMAX {

        zp(&mut pv[1]);

        iwarn += 2;

    }

    // Isolate the radial component of the velocity (au/day).

    let (_, pu) = pn(&pv[0]);

    vsr = pdp(&pu, &pv[1]);

    let usr = sxp(vsr, &pu);

    // Isolate the transverse component of the velocity (au/day).

    let ust = pmp(&pv[1], &usr);

    vst = pm(ust);

    // Special-relativity dimensionless parameters.

    betsr = vsr / DC;

    betst = vst / DC;

    // Determine the observed-to-inertial correction terms.

    bett = betst;

    betr = betsr;

    while i < IMAX {

        d = 1.0 + betr;

        w = betr * betr + bett * bett;

        del = -w / ((1.0 - w).sqrt() + 1.0);

        betr = d * betsr + del;

        bett = d * betst;

        if i > 0 {

            dd = (d - od).abs();

            ddel = (del - odel).abs();

            if i > 1 && dd >= odd && ddel >= oddel {

                break;

            }

            odd = dd;

            oddel = ddel;

        }

        od = d;

        odel = del;

        i += 1;

    }

    if i >= IMAX {

        iwarn += 4;

    }

    // Scale observed tangential velocity vector into inertial (au/d).

    let ut = sxp(d, &ust);

    // Compute inertial radial velocity vector (au/d).

    let ur = sxp(DC * (d * betsr + del), &pu);

    // Combine the two to obtain the inertial space velocity vector.

    pv[1] = ppp(&ur, &ut);

    (pv, iwarn)

}