use crate::astro::{pvstar, starpv};

use crate::star::fk5hip;

use crate::vm::{pmp, pxp, rxp, trxp};

/// Transform Hipparcos star data into the FK5 (J2000.0) system.

///

/// Status:  support function.

///

/// Given (all Hipparcos, epoch J2000.0):

///    rh      f64    RA (radians)

///    dh      f64    Dec (radians)

///    drh     f64    proper motion in RA (dRA/dt, rad/Jyear)

///    ddh     f64    proper motion in Dec (dDec/dt, rad/Jyear)

///    pxh     f64    parallax (arcsec)

///    rvh     f64    radial velocity (km/s, positive = receding)

///

/// Returned (all FK5, equinox J2000.0, epoch J2000.0):

///    r5      f64    RA (radians)

///    d5      f64    Dec (radians)

///    dr5     f64    proper motion in RA (dRA/dt, rad/Jyear)

///    dd5     f64    proper motion in Dec (dDec/dt, rad/Jyear)

///    px5     f64    parallax (arcsec)

///    rv5     f64    radial velocity (km/s, positive = receding)

///

/// Notes:

///

/// 1) This function transforms Hipparcos star positions and proper

///    motions into FK5 J2000.0.

///

/// 2) The proper motions in RA are dRA/dt rather than

///    cos(Dec)*dRA/dt, and are per year rather than per century.

///

/// 3) The FK5 to Hipparcos transformation is modeled as a pure

///    rotation and spin;  zonal errors in the FK5 catalog are not

///    taken into account.

///

/// 4) See also fk52h, fk5hz, hfk5z.

///

/// Called:

///    starpv    star catalog data to space motion pv-vector

///    fk5hip    FK5 to Hipparcos rotation and spin

///    rv2m      r-vector to r-matrix

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

///    trxp      product of transpose of r-matrix and p-vector

///    pxp       vector product of two p-vectors

///    pmp       p-vector minus p-vector

///    pvstar    space motion pv-vector to star catalog data

///

/// Reference:

///    F.Mignard & M.Froeschle, Astron.Astrophys., 354, 732-739 (2000).

pub fn h2fk5(

    rh: f64,

    dh: f64,

    drh: f64,

    ddh: f64,

    pxh: f64,

    rvh: f64,

) -> (f64, f64, f64, f64, f64, f64) {

    let mut pv5 = [[0.0; 3]; 2];

    let mut sh = [0.0; 3];

    /* Hipparcos barycentric position/velocity pv-vector (normalized). */

    let (pvh, _) = starpv(rh, dh, drh, ddh, pxh, rvh);

    /* FK5 to Hipparcos orientation matrix and spin vector. */

    let (r5h, mut s5h) = fk5hip();

    /* Make spin units per day instead of per year. */

    for val in s5h.iter_mut() {

        *val /= 365.25;

    }

    /* Orient the spin into the Hipparcos system. */

    rxp(&r5h, &s5h, &mut sh);

    /* De-orient the Hipparcos position into the FK5 system. */

    trxp(&r5h, &pvh[0], &mut pv5[0]);

    /* Apply spin to the position giving an extra space motion component. */

    let wxp = pxp(&pvh[0], &sh);

    /* Subtract this component from the Hipparcos space motion. */

    let vv = pmp(&pvh[1], &wxp);

    /* De-orient the Hipparcos space motion into the FK5 system. */

    trxp(&r5h, &vv, &mut pv5[1]);

    /* FK5 pv-vector to spherical. */

    let res = pvstar(&pv5).unwrap();

    let r5 = res[0];

    let d5 = res[1];

    let dr5 = res[2];

    let dd5 = res[3];

    let px5 = res[4];

    let rv5 = res[5];

    (r5, d5, dr5, dd5, px5, rv5)

}