"""Local airport coordinate lookup (IATA/ICAO -> lat/lon).

The FlightRadar24 plan in use cannot return airport coordinates (the /full
endpoint is 403, /light has no lat/lon), so we resolve destinations from the
bundled OpenFlights table (airports.dat) instead. This makes the estimated-path
arcs target the real destination rather than dead-reckoning to a random point.
"""
from __future__ import annotations

import csv
import os
from functools import lru_cache

_DAT = os.path.join(os.path.dirname(os.path.abspath(__file__)), "airports.dat")


@lru_cache(maxsize=1)
def _index():
    """Build {CODE: (lat, lon)} for both IATA and ICAO codes."""
    idx = {}
    try:
        with open(_DAT, encoding="utf-8") as fh:
            for row in csv.reader(fh):
                if len(row) < 8:
                    continue
                iata, icao, lat, lon = row[4], row[5], row[6], row[7]
                try:
                    coords = (float(lat), float(lon))
                except (TypeError, ValueError):
                    continue
                if iata and iata not in ("", "\\N"):
                    idx[iata.upper()] = coords
                if icao and icao not in ("", "\\N"):
                    idx[icao.upper()] = coords
    except FileNotFoundError:
        return {}
    return idx


def coords(code: str):
    """Return (lat, lon) for an IATA or ICAO code, or None if unknown."""
    if not code:
        return None
    return _index().get(code.strip().upper())