#include <string.h>
#include <math.h>

#include "astro.h"

/* convert the given apparent RA/Dec to astrometric precessed to Mjd IN PLACE.
 * we have no un-abberation etc so to find the correction: assume
 * *rap and *decp are astrometric@EOD, convert to apparent and back out
 * the difference; then precess to Mjd.
 */
void
ap_as (Now *np, double Mjd, double *rap, double *decp)
{
	double r0 = *rap, d0 = *decp;
	Obj o;
	Now n;

	/* as -> ap */
	zero_mem ((void *)&o, sizeof(o));
	o.o_type = FIXED;
	o.f_RA = *rap;
	o.f_dec = *decp;
	o.f_epoch = mjd;
	memcpy ((void *)&n, (void *)np, sizeof(Now));
	n.n_epoch = EOD;
	obj_cir (&n, &o);
	*rap -= o.s_ra - *rap;
	*decp -= o.s_dec - *decp;

	/* then back to start for second order correction */
	o.o_type = FIXED;
	o.f_RA = *rap;
	o.f_dec = *decp;
	o.f_epoch = mjd;
	memcpy ((void *)&n, (void *)np, sizeof(Now));
	n.n_epoch = EOD;
	obj_cir (&n, &o);
	*rap -= o.s_ra - r0;
	*decp -= o.s_dec - d0;

	radecrange (rap, decp);
	precess (mjd, Mjd, rap, decp);
	radecrange (rap, decp);
}

/* convert the given astrometric RA/Dec which are precessed to Mjd into
 * apparent @ EOD IN PLACE.
 */
void
as_ap (Now *np, double Mjd, double *rap, double *decp)
{
	Obj o;
	Now n;

	zero_mem ((void *)&o, sizeof(o));
	o.o_type = FIXED;
	o.f_RA = *rap;
	o.f_dec = *decp;
	o.f_epoch = Mjd;
	memcpy ((void *)&n, (void *)np, sizeof(Now));
	n.n_epoch = EOD;
	obj_cir (&n, &o);
	*rap = o.s_ra;
	*decp = o.s_dec;
}