"""
Maidenhead locator helpers.

latlon_to_subsquare(lat, lon) -> str       e.g. "JO78ai"
subsquare_bounds(sq)          -> dict      {lat_min, lon_min, lat_max, lon_max}
"""


def latlon_to_subsquare(lat: float, lon: float) -> str:
    """Convert WGS84 coordinates to 6-character Maidenhead subsquare."""
    lon_n = lon + 180.0
    lat_n = lat + 90.0

    field_lon = int(lon_n / 20)
    field_lat = int(lat_n / 10)
    lon_n = lon_n % 20
    lat_n = lat_n % 10

    sq_lon = int(lon_n / 2)
    sq_lat = int(lat_n / 1)
    lon_n = (lon_n % 2) * 12
    lat_n = (lat_n % 1) * 24

    sub_lon = int(lon_n)
    sub_lat = int(lat_n)

    return (
        chr(ord("A") + field_lon)
        + chr(ord("A") + field_lat)
        + str(sq_lon)
        + str(sq_lat)
        + chr(ord("a") + sub_lon)
        + chr(ord("a") + sub_lat)
    )


def subsquare_bounds(sq: str) -> dict:
    """
    Return bounding box for a 6-character Maidenhead subsquare.
    Each subsquare is 5' longitude ?? 2.5' latitude (~10 ?? 4.6 km in Sweden).
    """
    lon = (ord(sq[0]) - ord("A")) * 20.0
    lat = (ord(sq[1]) - ord("A")) * 10.0
    lon += int(sq[2]) * 2.0
    lat += int(sq[3]) * 1.0
    lon += (ord(sq[4]) - ord("a")) * (1.0 / 12.0)
    lat += (ord(sq[5]) - ord("a")) * (1.0 / 24.0)
    lon -= 180.0
    lat -= 90.0
    return {
        "lat_min": lat,
        "lon_min": lon,
        "lat_max": lat + (1.0 / 24.0),
        "lon_max": lon + (2.0 / 12.0),
    }