from __future__ import annotations
from typing import Optional, Dict
import os
import requests
from functools import lru_cache

# Nominatimの利用規約に従ってUAと連絡先を付与
def _ua() -> Dict[str, str]:
    email = os.getenv("GEOCODING_EMAIL") or os.getenv("CONTACT_EMAIL") or "example@example.com"
    return {"User-Agent": f"HF-Space-Trip-Planner/1.0 (contact: {email})"}

@lru_cache(maxsize=512)
def geocode_city(city: str) -> Optional[Dict[str, object]]:
    """
    文字列の都市名から緯度経度を取得（Nominatim / OpenStreetMap）。
    成功時: {"lat": float, "lon": float, "display_name": str}
    失敗時: None
    """
    if not city or not str(city).strip():
        return None

    q = str(city).strip()
    url = "https://nominatim.openstreetmap.org/search"
    params = {
        "q": q,
        "format": "jsonv2",
        "addressdetails": 1,
        "limit": 1,
    }
    try:
        r = requests.get(url, params=params, headers=_ua(), timeout=20)
        r.raise_for_status()
        items = r.json()
        if not items:
            return None
        j = items[0]
        lat = float(j["lat"])
        lon = float(j["lon"])
        name = j.get("display_name") or q
        return {"lat": lat, "lon": lon, "display_name": name}
    except Exception:
        return None