from __future__ import annotations

from datetime import date

import holidays


GERMAN_STATE_OPTIONS: list[dict[str, str]] = [
    {"code": "BW", "label": "Baden-Württemberg"},
    {"code": "BY", "label": "Bayern"},
    {"code": "BE", "label": "Berlin"},
    {"code": "BB", "label": "Brandenburg"},
    {"code": "HB", "label": "Bremen"},
    {"code": "HH", "label": "Hamburg"},
    {"code": "HE", "label": "Hessen"},
    {"code": "MV", "label": "Mecklenburg-Vorpommern"},
    {"code": "NI", "label": "Niedersachsen"},
    {"code": "NW", "label": "Nordrhein-Westfalen"},
    {"code": "RP", "label": "Rheinland-Pfalz"},
    {"code": "SL", "label": "Saarland"},
    {"code": "SN", "label": "Sachsen"},
    {"code": "ST", "label": "Sachsen-Anhalt"},
    {"code": "SH", "label": "Schleswig-Holstein"},
    {"code": "TH", "label": "Thüringen"},
]
GERMAN_STATE_CODES = {item["code"] for item in GERMAN_STATE_OPTIONS}


def normalize_german_state_code(value: str | None) -> str | None:
    if value is None:
        return None
    normalized = value.strip().upper()
    if not normalized:
        return None
    if normalized not in GERMAN_STATE_CODES:
        return None
    return normalized


def list_public_holiday_dates(
    *,
    federal_state: str,
    from_date: date,
    to_date: date,
) -> set[date]:
    if to_date < from_date:
        return set()
    years = list(range(from_date.year, to_date.year + 1))
    holiday_map = holidays.country_holidays("DE", subdiv=federal_state, years=years)
    result: set[date] = set()
    for holiday_date in holiday_map.keys():
        if from_date <= holiday_date <= to_date:
            result.add(holiday_date)
    return result