from __future__ import annotations

import numpy as np
from astropy import units as u
from pycraf import pathprof
from pyproj import Geod

from app.config import get_settings
from app.core.dem import elevations_along
from app.core.geo import GeoPoint, haversine, sample_path

_GEOD = Geod(ellps="WGS84")


def _clutter_zone(environment: str) -> pathprof.CLUTTER:
    mapping = {
        "urban": pathprof.CLUTTER.URBAN,
        "suburban": pathprof.CLUTTER.SUBURBAN,
        "rural": pathprof.CLUTTER.SPARSE,
    }
    return mapping.get(environment, pathprof.CLUTTER.SPARSE)


def _height_profile(
    tx: GeoPoint,
    rx: GeoPoint,
    *,
    dem_path: str | None = None,
    samples: int = 64,
) -> tuple[np.ndarray, np.ndarray, float, float]:
    points = sample_path(tx, rx, samples)
    try:
        heights = elevations_along(points, dem_path=dem_path or get_settings().dem_path)
    except Exception:
        heights = np.zeros(len(points), dtype=float)
    dists = np.array([point.distance_m for point in points], dtype=float) * u.m
    return dists, heights * u.m, points[0].lon, points[0].lat


def p452_path_loss(
    tx: GeoPoint,
    rx: GeoPoint,
    *,
    tx_height_agl: float,
    rx_height_agl: float,
    freq_mhz: float,
    environment: str = "rural",
    elevation_profile_m: list[float] | None = None,
    dem_path: str | None = None,
) -> float:
    distance_km = haversine(tx, rx) / 1000.0
    if elevation_profile_m is not None:
        count = len(elevation_profile_m)
        dists = np.linspace(0, distance_km * 1000, count) * u.m
        heights = np.array(elevation_profile_m, dtype=float) * u.m
        bearing, _, _ = _GEOD.inv(tx.lon, tx.lat, rx.lon, rx.lat)
        backbearing = (bearing + 180) % 360
    else:
        dists, heights, _, _ = _height_profile(tx, rx, dem_path=dem_path)
        bearing, _, _ = _GEOD.inv(tx.lon, tx.lat, rx.lon, rx.lat)
        backbearing = (bearing + 180) % 360

    pathprop = pathprof.PathProp(
        freq_mhz * u.MHz,
        293 * u.K,
        1013 * u.hPa,
        tx.lon * u.deg,
        tx.lat * u.deg,
        rx.lon * u.deg,
        rx.lat * u.deg,
        tx_height_agl * u.m,
        rx_height_agl * u.m,
        max(100.0, distance_km * 10) * u.m,
        50 * u.percent,
        zone_t=_clutter_zone(environment),
        zone_r=_clutter_zone(environment),
        hprof_dists=dists,
        hprof_heights=heights,
        hprof_bearing=bearing * u.deg,
        hprof_backbearing=backbearing * u.deg,
    )
    losses = pathprof.loss_complete(pathprop)
    total = losses[0]
    return float(total.value)