from __future__ import annotations

from dataclasses import dataclass
from math import log10

from app.core.geo import GeoPoint, haversine


@dataclass(frozen=True)
class LinkBudget:
    distance_km: float
    fspl_db: float
    diffraction_db: float
    vegetation_db: float
    atmospheric_db: float
    total_loss_db: float
    rx_power_dbm: float
    fade_margin_db: float
    fresnel_clear: bool
    link_viable: bool


def fspl(freq_mhz: float, dist_km: float) -> float:
    if freq_mhz <= 0:
        raise ValueError("freq_mhz must be positive")
    if dist_km <= 0:
        raise ValueError("dist_km must be positive")
    return 32.44 + 20 * log10(freq_mhz) + 20 * log10(dist_km)


def itm_loss(*args: object, **kwargs: object) -> float:
    raise NotImplementedError("Longley-Rice ITM integration is implemented in a later stage")


def p1812_field(*args: object, **kwargs: object) -> float:
    raise NotImplementedError("ITU-R P.1812 integration is implemented in a later stage")


def manual_link_budget(
    tx: GeoPoint,
    rx: GeoPoint,
    tx_power_dbm: float,
    tx_gain_dbi: float,
    rx_gain_dbi: float,
    sensitivity_dbm: float,
    frequency_mhz: float,
    diffraction_db: float = 0.0,
    vegetation_db: float = 0.0,
    atmospheric_db: float = 0.0,
    misc_loss_db: float = 0.0,
    fresnel_clear: bool = True,
) -> LinkBudget:
    distance_km = haversine(tx, rx) / 1000.0
    free_space_loss = fspl(frequency_mhz, distance_km)
    total_loss = free_space_loss + diffraction_db + vegetation_db + atmospheric_db + misc_loss_db
    rx_power = tx_power_dbm + tx_gain_dbi + rx_gain_dbi - total_loss
    margin = rx_power - sensitivity_dbm
    return LinkBudget(
        distance_km=distance_km,
        fspl_db=free_space_loss,
        diffraction_db=diffraction_db,
        vegetation_db=vegetation_db,
        atmospheric_db=atmospheric_db,
        total_loss_db=total_loss,
        rx_power_dbm=rx_power,
        fade_margin_db=margin,
        fresnel_clear=fresnel_clear,
        link_viable=margin > 0,
    )