import json
from functools import lru_cache
from pathlib import Path

from django.conf import settings


@lru_cache(maxsize=1)
def location_data():
    path = Path(settings.BASE_DIR) / "static" / "data" / "iran-locations.json"
    return json.loads(path.read_text(encoding="utf-8"))


@lru_cache(maxsize=1)
def provinces():
    return tuple(location_data())


@lru_cache(maxsize=1)
def cities_by_province():
    return {item["province"]: tuple(item["cities"]) for item in location_data()}


def validate_location(province, city):
    province = (province or "").strip()
    city = (city or "").strip()
    if not province and not city:
        return province, city, None
    if city and not province:
        return province, city, "برای انتخاب شهر، ابتدا استان را انتخاب کنید."
    cities = cities_by_province()
    if province not in cities:
        return province, city, "استان انتخاب‌شده معتبر نیست."
    if city and city not in cities[province]:
        return province, city, "شهر انتخاب‌شده متعلق به این استان نیست."
    return province, city, None