"""
Line-of-sight checks using terrain profile data.
"""

import math
from typing import Optional, Dict, List

EARTH_RADIUS = 6371000
K_FACTOR = 4 / 3  # Standard atmospheric refraction


def check_los_terrain(
    profile: List[dict],
    tx_height: float,
    rx_height: float,
) -> dict:
    """
    Check line-of-sight from a terrain elevation profile.

    Args:
        profile: List of dicts with 'elevation' and 'distance' keys.
        tx_height: TX antenna height above ground (meters).
        rx_height: RX height above ground (meters).

    Returns:
        dict with has_los, clearance, blocked_at
    """
    if not profile:
        return {"has_los": True, "clearance": 0.0, "blocked_at": None}

    tx_ground = profile[0]["elevation"]
    rx_ground = profile[-1]["elevation"]
    tx_total = tx_ground + tx_height
    rx_total = rx_ground + rx_height
    total_distance = profile[-1]["distance"]

    min_clearance = float("inf")
    blocked_at = None

    for point in profile:
        d = point["distance"]
        terrain_elev = point["elevation"]

        if total_distance == 0:
            los_height = tx_total
        else:
            los_height = tx_total + (rx_total - tx_total) * (d / total_distance)

        # Earth curvature correction
        effective_radius = K_FACTOR * EARTH_RADIUS
        curvature = (d * (total_distance - d)) / (2 * effective_radius)
        los_height_corrected = los_height - curvature

        clearance = los_height_corrected - terrain_elev

        if clearance < min_clearance:
            min_clearance = clearance
            if clearance <= 0:
                blocked_at = d

    return {
        "has_los": min_clearance > 0,
        "clearance": min_clearance,
        "blocked_at": blocked_at,
    }


def fresnel_radius(
    d1_m: float, d2_m: float, wavelength_m: float, zone: int = 1
) -> float:
    """Calculate Fresnel zone radius at a point along the path.

    Args:
        d1_m: Distance from TX to point
        d2_m: Distance from point to RX
        wavelength_m: Signal wavelength
        zone: Fresnel zone number (default 1)

    Returns:
        Radius in meters
    """
    total = d1_m + d2_m
    if total <= 0:
        return 0.0
    return math.sqrt(zone * wavelength_m * d1_m * d2_m / total)