"""IATA <-> ICAO lookups for airports and airlines, loaded once from the
trimmed CSVs in data/ (see scripts/build_reference_data.py). No network
access at runtime.
"""

import csv
from pathlib import Path

DATA_DIR = Path(__file__).resolve().parent / "data"

# Known-correct overrides, checked before the bundled CSV. The CSV (OpenFlights)
# can lag real-world rebrands - e.g. it still maps VA to the ICAO code of the
# defunct "V Australia Airlines" (VAU) rather than the current Virgin
# Australia code (VOZ). These are the examples called out in the brief.
CARRIER_ICAO_OVERRIDES = {
    "QF": "QFA",
    "VA": "VOZ",
    "JQ": "JST",
    "EK": "UAE",
}


def _load_csv(path: Path) -> dict[str, tuple[str, str]]:
    """Returns iata -> (icao, name)."""
    result = {}
    if not path.exists():
        return result
    with path.open(newline="", encoding="utf-8") as f:
        for row in csv.DictReader(f):
            iata = (row.get("iata") or "").strip().upper()
            icao = (row.get("icao") or "").strip().upper()
            name = (row.get("name") or "").strip()
            if iata and icao:
                result[iata] = (icao, name)
    return result


_AIRPORTS = _load_csv(DATA_DIR / "airports.csv")
_AIRLINES = _load_csv(DATA_DIR / "airlines.csv")


def iata_to_icao_airport(iata_code: str) -> str | None:
    if not iata_code:
        return None
    entry = _AIRPORTS.get(iata_code.strip().upper())
    return entry[0] if entry else None


def airport_name(iata_code: str) -> str | None:
    if not iata_code:
        return None
    entry = _AIRPORTS.get(iata_code.strip().upper())
    return entry[1] if entry else None


def iata_to_icao_airline(iata_code: str) -> str | None:
    if not iata_code:
        return None
    code = iata_code.strip().upper()
    if code in CARRIER_ICAO_OVERRIDES:
        return CARRIER_ICAO_OVERRIDES[code]
    entry = _AIRLINES.get(code)
    return entry[0] if entry else None


def airline_name(iata_code: str) -> str | None:
    if not iata_code:
        return None
    entry = _AIRLINES.get(iata_code.strip().upper())
    return entry[1] if entry else None