from __future__ import annotations

import math
from typing import Literal

from app.models.schemas import LinkBudget


def fspl_db(distance_m: float, freq_mhz: float) -> float:
  if distance_m <= 0:
    return 0.0
  return 20.0 * math.log10(distance_m / 1000.0) + 20.0 * math.log10(freq_mhz) + 27.55


def compute_link_budget(
  tx_power_dbm: float,
  rx_sensitivity_dbm: float,
  distance_m: float,
  freq_mhz: float,
) -> LinkBudget:
  loss = fspl_db(distance_m, freq_mhz)
  margin = tx_power_dbm - rx_sensitivity_dbm - loss
  status: Literal["good", "marginal", "poor"]
  if margin >= 20:
    status = "good"
  elif margin >= 10:
    status = "marginal"
  else:
    status = "poor"

  return LinkBudget(
    tx_power_dbm=tx_power_dbm,
    rx_sensitivity_dbm=rx_sensitivity_dbm,
    margin_db=round(margin, 1),
    status=status,
  )