from __future__ import annotations

from dataclasses import dataclass
from math import exp


@dataclass(frozen=True)
class AntennaPattern:
    pattern: str = "omni"
    azimuth_deg: float = 0.0
    tilt_deg: float = 0.0
    gain_dbi: float = 0.0
    beamwidth_h: float | None = None
    beamwidth_v: float | None = None
    front_to_back_db: float = 25.0
    sidelobe_floor_db: float = -30.0
    pattern_file: str | None = None


def _angular_delta(angle: float, center: float) -> float:
    return (angle - center + 180.0) % 360.0 - 180.0


def _gaussian_drop(delta: float, beamwidth: float) -> float:
    if beamwidth <= 0:
        raise ValueError("beamwidth must be positive")
    sigma = beamwidth / 2.355
    normalized = exp(-0.5 * (delta / sigma) ** 2)
    if normalized <= 0:
        return float("-inf")
    return 10.0 * (normalized - 1.0)


def gain(pattern: AntennaPattern, az_deg: float, el_deg: float) -> float:
    if pattern.pattern == "omni":
        return pattern.gain_dbi
    if pattern.pattern == "file":
        from app.core.antenna_pattern_file import gain_from_file

        return gain_from_file(pattern, az_deg, el_deg)
    if pattern.pattern != "sector":
        raise ValueError(f"Unknown antenna pattern: {pattern.pattern}")

    if pattern.beamwidth_h is None or pattern.beamwidth_v is None:
        raise ValueError("sector pattern requires horizontal and vertical beamwidths")

    az_delta = _angular_delta(az_deg, pattern.azimuth_deg)
    el_delta = el_deg - pattern.tilt_deg
    h_drop = _gaussian_drop(az_delta, pattern.beamwidth_h)
    v_drop = _gaussian_drop(el_delta, pattern.beamwidth_v)
    attenuation = max(pattern.sidelobe_floor_db, h_drop + v_drop)
    if abs(az_delta) > 90:
        attenuation = min(attenuation, -pattern.front_to_back_db)
    return pattern.gain_dbi + attenuation