from __future__ import annotations

from itur.models import itu676

from app.core.geo import GeoPoint, haversine


def p676_gas_attenuation(freq_hz: float, distance_km: float) -> float:
    if freq_hz <= 0:
        raise ValueError("freq_hz must be positive")
    if distance_km < 0:
        raise ValueError("distance_km must be non-negative")
    if distance_km == 0:
        return 0.0

    freq_ghz = freq_hz / 1_000_000_000
    attenuation = itu676.gaseous_attenuation_terrestrial_path(
        distance_km,
        freq_ghz,
        0,
        7.5,
        1013,
        288,
        "exact",
    )
    return float(attenuation.value)


def atmospheric_loss_between(tx: GeoPoint, rx: GeoPoint, freq_hz: float) -> float:
    distance_km = haversine(tx, rx) / 1000.0
    return p676_gas_attenuation(freq_hz, distance_km)