//! Bridge from orbital propagation to the standard's address space.
//!
//! A live satellite occupies the `F3` (feature / live-entity) tier. Its
//! ground-relative address is its **sub-point**: the geodetic position of the
//! propagated state, projected to an S2 cell at the requested level, with the
//! altitude band for its altitude and the time bucket for the instant. This puts
//! a satellite on the same 4D grid (SPEC §2) as every other tile, so an entity
//! feed and a basemap share one index.

use chrono::{DateTime, Utc};
use map_index::volume::TimeTier;
use map_schema::{CellKey, Lod};

use crate::{satellite_position, GeodeticPosition, OrbitalResult, Sgp4State};

/// The [`CellKey`] for a geodetic position at an instant: S2 cell at `level`,
/// the altitude band for `alt_km`, and the time bucket at `tier`.
pub fn geodetic_cell_key(
    geo: &GeodeticPosition,
    level: u8,
    time_secs: i64,
    tier: TimeTier,
    lod: Lod,
) -> CellKey {
    map_index::cell_key(
        geo.lat_deg,
        geo.lon_deg,
        level,
        map_index::alt_band(geo.alt_km * 1000.0),
        map_index::time_bucket(time_secs, tier),
        lod,
    )
}

/// Propagate `state` to `dt` and return the satellite sub-point's [`CellKey`].
pub fn subpoint_cell_key(
    state: &Sgp4State,
    dt: &DateTime<Utc>,
    level: u8,
    tier: TimeTier,
    lod: Lod,
) -> OrbitalResult<CellKey> {
    let geo = satellite_position(state, dt)?;
    Ok(geodetic_cell_key(&geo, level, dt.timestamp(), tier, lod))
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::tle::parse_tle;

    const ISS_NAME: &str = "ISS (ZARYA)";
    const ISS_L1: &str = "1 25544U 98067A   24001.50000000  .00016717  00000-0  10270-3 0  9009";
    const ISS_L2: &str = "2 25544  51.6416 247.4627 0006703  30.0000  10.0000 15.49560000000007";

    #[test]
    fn iss_subpoint_lands_in_leo_band() {
        let tle = parse_tle(ISS_NAME, ISS_L1, ISS_L2).unwrap();
        let state = Sgp4State::initialize(&tle).unwrap();
        // Realtime tier (1 s buckets) is right for a live satellite.
        let key = subpoint_cell_key(&state, &tle.epoch, 10, TimeTier::Realtime, Lod(0)).unwrap();
        // The ISS orbits at ~408 km → the LEO altitude band (schema index 4).
        assert_eq!(key.alt, map_schema::AltBand(4), "ISS should be in the LEO band");
        // Horizontal address is a valid S2 cell at the requested level.
        assert_eq!(key.s2.level(), Some(10));
        // Realtime bucket is 1 s wide.
        assert_eq!(key.time.width_ms, 1_000);
    }

    #[test]
    fn geodetic_cell_key_maps_surface_to_band_zero() {
        let geo = GeodeticPosition { lat_deg: 37.77, lon_deg: -122.42, alt_km: 0.0 };
        let key = geodetic_cell_key(&geo, 14, 0, TimeTier::Recent, Lod(0));
        assert_eq!(key.alt, map_schema::AltBand(0));
        assert_eq!(key.s2.level(), Some(14));
    }
}