"""Reverse-Geocoding ueber Nominatim, Ergebnisse werden dauerhaft gecacht."""
import json
import urllib.parse
import urllib.request
from datetime import datetime, timezone

from . import config, db


def _label(address: dict) -> str:
    city = (
        address.get("city")
        or address.get("town")
        or address.get("village")
        or address.get("municipality")
        or address.get("county")
    )
    detail = address.get("suburb") or address.get("neighbourhood") or address.get("road")
    parts = [p for p in (city, detail) if p]
    if not parts:
        return address.get("state") or address.get("country") or ""
    return ", ".join(parts[:2])


def reverse(lat: float | None, lon: float | None) -> str | None:
    if lat is None or lon is None or not config.REVERSE_GEOCODE:
        return None

    # Auf ~100 m runden: benachbarte Scans teilen sich denselben Cache-Eintrag.
    key = f"{lat:.3f},{lon:.3f}"
    cached = db.query_one("SELECT place FROM geocache WHERE key = ?", (key,))
    if cached is not None:
        return cached["place"]

    url = config.NOMINATIM_URL + "?" + urllib.parse.urlencode(
        {"lat": lat, "lon": lon, "format": "jsonv2", "zoom": "16", "accept-language": "de"}
    )
    place = None
    try:
        request = urllib.request.Request(url, headers={"User-Agent": config.USER_AGENT})
        with urllib.request.urlopen(request, timeout=6) as response:
            data = json.loads(response.read().decode("utf-8"))
        place = _label(data.get("address") or {}) or data.get("display_name")
    except Exception:
        # Ohne Ortsnamen bleiben die Koordinaten - kein Grund, den Scan abzubrechen.
        return None

    db.execute(
        "INSERT OR REPLACE INTO geocache (key, place, fetched_at) VALUES (?, ?, ?)",
        (key, place, datetime.now(timezone.utc).isoformat()),
    )
    return place