/*
 * moon_funcs.c -- Planetary moon observation
 *
 * SQL functions for observing moons of Jupiter, Saturn, Uranus, and Mars.
 * Each moon's position is computed in the VSOP87 ecliptic J2000 frame
 * relative to its parent planet, then combined with the parent's
 * heliocentric position to get geocentric az/el.
 *
 * Pipeline for each moon:
 *   1. Parent planet heliocentric position (VSOP87)
 *   2. Moon position relative to parent (L12/TASS17/GUST86/MARSSAT)
 *   3. Moon heliocentric = parent + moon_relative
 *   4. Moon geocentric = moon_heliocentric - Earth_heliocentric
 *   5. Ecliptic -> equatorial -> precess -> az/el
 */

#include "postgres.h"
#include "fmgr.h"
#include "funcapi.h"
#include "utils/timestamp.h"
#include "types.h"
#include "astro_math.h"
#include "vsop87.h"
#include "l12.h"
#include "tass17.h"
#include "gust86.h"
#include "marssat.h"
#include <math.h>

PG_FUNCTION_INFO_V1(galilean_observe);
PG_FUNCTION_INFO_V1(saturn_moon_observe);
PG_FUNCTION_INFO_V1(uranus_moon_observe);
PG_FUNCTION_INFO_V1(mars_moon_observe);


/*
 * observe_from_geocentric() is now in astro_math.h as a static inline,
 * shared by planet_funcs.c, moon_funcs.c, and de_funcs.c.
 */


/* ================================================================
 * Internal: common pattern for all planetary moons
 *
 * Given: moon position relative to parent (VSOP87 ecliptic J2000, AU)
 *        parent's VSOP87 body index (0-based)
 *        observer, JD
 *
 * Computes geocentric position and returns topocentric az/el.
 * ================================================================
 */
static void
observe_planetary_moon(const double moon_rel[3], int vsop_parent,
                       double jd, const pg_observer *obs,
                       pg_topocentric *result)
{
    double parent_xyz[6];
    double earth_xyz[6];
    double geo_ecl[3];

    /* Parent planet heliocentric */
    GetVsop87Coor(jd, vsop_parent, parent_xyz);

    /* Earth heliocentric */
    GetVsop87Coor(jd, 2, earth_xyz);  /* VSOP87 body 2 = Earth */

    /* Moon geocentric = (parent + moon_relative) - Earth */
    geo_ecl[0] = (parent_xyz[0] + moon_rel[0]) - earth_xyz[0];
    geo_ecl[1] = (parent_xyz[1] + moon_rel[1]) - earth_xyz[1];
    geo_ecl[2] = (parent_xyz[2] + moon_rel[2]) - earth_xyz[2];

    observe_from_geocentric(geo_ecl, jd, obs, result);
}


/* ================================================================
 * galilean_observe(body_id int, observer, timestamptz) -> topocentric
 *
 * Observe a Galilean moon of Jupiter.
 * Body IDs: 0=Io, 1=Europa, 2=Ganymede, 3=Callisto
 *
 * Uses L1.2 theory (Lainey, Duriez & Vienne) for moon positions
 * and VSOP87 for Jupiter and Earth.
 * ================================================================
 */
Datum
galilean_observe(PG_FUNCTION_ARGS)
{
    int32           body_id = PG_GETARG_INT32(0);
    pg_observer    *obs     = (pg_observer *) PG_GETARG_POINTER(1);
    int64           ts      = PG_GETARG_INT64(2);
    double          jd;
    double          moon_xyz[3];
    pg_topocentric *result;

    if (body_id < L12_IO || body_id > L12_CALLISTO)
        ereport(ERROR,
                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                 errmsg("galilean_observe: body_id %d must be 0-3 (Io, Europa, Ganymede, Callisto)",
                        body_id)));

    jd = timestamptz_to_jd(ts);

    /* Moon position relative to Jupiter, VSOP87 ecliptic J2000, AU */
    GetL12Coor(jd, body_id, moon_xyz, NULL);

    result = (pg_topocentric *) palloc(sizeof(pg_topocentric));
    observe_planetary_moon(moon_xyz, 4, jd, obs, result);  /* VSOP87 body 4 = Jupiter */

    PG_RETURN_POINTER(result);
}


/* ================================================================
 * saturn_moon_observe(body_id int, observer, timestamptz) -> topocentric
 *
 * Observe a moon of Saturn.
 * Body IDs: 0=Mimas, 1=Enceladus, 2=Tethys, 3=Dione,
 *           4=Rhea, 5=Titan, 6=Iapetus, 7=Hyperion
 *
 * Uses TASS 1.7 theory (Vienne & Duriez).
 * ================================================================
 */
Datum
saturn_moon_observe(PG_FUNCTION_ARGS)
{
    int32           body_id = PG_GETARG_INT32(0);
    pg_observer    *obs     = (pg_observer *) PG_GETARG_POINTER(1);
    int64           ts      = PG_GETARG_INT64(2);
    double          jd;
    double          moon_xyz[3];
    pg_topocentric *result;

    if (body_id < TASS17_MIMAS || body_id > TASS17_HYPERION)
        ereport(ERROR,
                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                 errmsg("saturn_moon_observe: body_id %d must be 0-7 (Mimas-Hyperion)",
                        body_id)));

    jd = timestamptz_to_jd(ts);

    GetTass17Coor(jd, body_id, moon_xyz, NULL);

    result = (pg_topocentric *) palloc(sizeof(pg_topocentric));
    observe_planetary_moon(moon_xyz, 5, jd, obs, result);  /* VSOP87 body 5 = Saturn */

    PG_RETURN_POINTER(result);
}


/* ================================================================
 * uranus_moon_observe(body_id int, observer, timestamptz) -> topocentric
 *
 * Observe a moon of Uranus.
 * Body IDs: 0=Miranda, 1=Ariel, 2=Umbriel, 3=Titania, 4=Oberon
 *
 * Uses GUST86 theory (Laskar & Jacobson).
 * ================================================================
 */
Datum
uranus_moon_observe(PG_FUNCTION_ARGS)
{
    int32           body_id = PG_GETARG_INT32(0);
    pg_observer    *obs     = (pg_observer *) PG_GETARG_POINTER(1);
    int64           ts      = PG_GETARG_INT64(2);
    double          jd;
    double          moon_xyz[3];
    pg_topocentric *result;

    if (body_id < GUST86_MIRANDA || body_id > GUST86_OBERON)
        ereport(ERROR,
                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                 errmsg("uranus_moon_observe: body_id %d must be 0-4 (Miranda-Oberon)",
                        body_id)));

    jd = timestamptz_to_jd(ts);

    GetGust86Coor(jd, body_id, moon_xyz, NULL);

    result = (pg_topocentric *) palloc(sizeof(pg_topocentric));
    observe_planetary_moon(moon_xyz, 6, jd, obs, result);  /* VSOP87 body 6 = Uranus */

    PG_RETURN_POINTER(result);
}


/* ================================================================
 * mars_moon_observe(body_id int, observer, timestamptz) -> topocentric
 *
 * Observe a moon of Mars.
 * Body IDs: 0=Phobos, 1=Deimos
 *
 * Uses MarsSat theory (Lainey, 2007).
 * ================================================================
 */
Datum
mars_moon_observe(PG_FUNCTION_ARGS)
{
    int32           body_id = PG_GETARG_INT32(0);
    pg_observer    *obs     = (pg_observer *) PG_GETARG_POINTER(1);
    int64           ts      = PG_GETARG_INT64(2);
    double          jd;
    double          moon_xyz[3];
    pg_topocentric *result;

    if (body_id < MARS_SAT_PHOBOS || body_id > MARS_SAT_DEIMOS)
        ereport(ERROR,
                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                 errmsg("mars_moon_observe: body_id %d must be 0-1 (Phobos, Deimos)",
                        body_id)));

    jd = timestamptz_to_jd(ts);

    GetMarsSatCoor(jd, body_id, moon_xyz, NULL);

    result = (pg_topocentric *) palloc(sizeof(pg_topocentric));
    observe_planetary_moon(moon_xyz, 3, jd, obs, result);  /* VSOP87 body 3 = Mars */

    PG_RETURN_POINTER(result);
}