import requests

_geo_cache = {}

def city_to_coordinates(city):
    """Convert a city name to (lat, lon) using Open-Meteo's geocoding API."""
    if city in _geo_cache:
        return _geo_cache[city]

    url = "https://geocoding-api.open-meteo.com/v1/search"
    params = {
        "name": city.strip(),
        "count": 1,
        "format": "json"
    }

    try:
        response = requests.get(url, params=params, timeout=10)
        response.raise_for_status()
        data = response.json()
        results = data.get("results")
        if not results:
            return None
        coords = (results[0]["latitude"], results[0]["longitude"])
        _geo_cache[city] = coords
        return coords
    except (requests.RequestException, ValueError) as e:
        print(f"city_to_coordinates failed for '{city}': {e}")
        return None