"""Author RAG Chatbot SaaS — GeoIP Lookup.

IP → country/region/city mapping.

Resolution order (first success wins):
  1. MaxMind GeoLite2-City.mmdb  (offline, fast, requires downloaded DB file)
  2. ip-api.com free tier         (HTTP, 45 req/min, no API key, results cached 24h in Redis)

IP address is NEVER stored — only geo fields derived from it.
Redis cache key is a SHA-256 hash of the IP (not the raw IP).
"""

import hashlib
import structlog

logger = structlog.get_logger(__name__)

_GEO_CACHE_TTL = 86_400        # 24 hours
_GEO_CACHE_PREFIX = "geo:ip:"  # key = geo:ip:<sha256[:16]>

_geoip_reader = None


def _get_reader():
    """Lazily load and cache the MaxMind GeoLite2 reader."""
    global _geoip_reader
    if _geoip_reader is None:
        try:
            import maxminddb
            from app.config import get_settings
            cfg = get_settings()
            _geoip_reader = maxminddb.open_database(cfg.GEO_DB_PATH)
            logger.info("MaxMind GeoIP DB loaded", path=cfg.GEO_DB_PATH)
        except Exception as e:
            logger.warning("MaxMind GeoIP DB not available — will use ip-api.com fallback", error=str(e))
    return _geoip_reader


def _ip_cache_key(ip: str) -> str:
    """Return a Redis key for a given IP — uses a hash, never the raw IP."""
    hashed = hashlib.sha256(ip.encode()).hexdigest()[:16]
    return f"{_GEO_CACHE_PREFIX}{hashed}"


async def _lookup_maxmind(ip: str) -> dict | None:
    """Try MaxMind GeoLite2-City.mmdb lookup. Returns None if DB unavailable."""
    reader = _get_reader()
    if reader is None:
        return None
    try:
        record = reader.get(ip)
        if not record:
            return None
        country = record.get("country", {})
        city = record.get("city", {})
        subdivisions = record.get("subdivisions", [])
        region = ""
        if subdivisions:
            region = (subdivisions[0].get("names") or {}).get("en", "")
        return {
            "country_code": country.get("iso_code", "")[:2],
            "country_name": (country.get("names") or {}).get("en", ""),
            "region": region,
            "city": (city.get("names") or {}).get("en", ""),
        }
    except Exception as e:
        logger.debug("MaxMind lookup failed", error=str(e))
        return None


async def _lookup_ipapi(ip: str) -> dict:
    """Fallback: query ip-api.com free endpoint (no API key, 45 req/min).

    Returns empty dict on any error so caller always gets a safe result.
    Fields requested: country code, country name, region, city only.
    """
    try:
        import httpx
        url = f"http://ip-api.com/json/{ip}?fields=status,country,countryCode,regionName,city"
        async with httpx.AsyncClient(timeout=3.0) as client:
            resp = await client.get(url)
            if resp.status_code != 200:
                return {}
            data = resp.json()
            if data.get("status") != "success":
                return {}
            return {
                "country_code": (data.get("countryCode") or "")[:2],
                "country_name": data.get("country") or "",
                "region": data.get("regionName") or "",
                "city": data.get("city") or "",
            }
    except Exception as e:
        logger.debug("ip-api.com fallback failed", error=str(e))
        return {}


async def get_geo_info(request, redis=None) -> dict:
    """Derive country, region, and city from the request IP.

    Resolution order:
      1. Redis cache (24h TTL, keyed by hashed IP)
      2. MaxMind GeoLite2 (if DB file present)
      3. ip-api.com free API (fallback)

    Args:
        request: FastAPI request.
        redis: Optional Redis client for caching ip-api results.

    Returns:
        Dict with country_code, country_name, region, city.
        Returns empty dict if all lookups fail.
    """
    ip = get_real_ip(request)
    if not ip or ip in ("127.0.0.1", "::1", "unknown"):
        return {}

    cache_key = _ip_cache_key(ip)

    # ── 1. Check Redis cache ──────────────────────────────────────────────────
    if redis is not None:
        try:
            import json
            cached = await redis.get(cache_key)
            if cached:
                return json.loads(cached)
        except Exception:
            pass  # Cache miss — proceed to lookup

    # ── 2. MaxMind (fast, offline) ────────────────────────────────────────────
    result = await _lookup_maxmind(ip)

    # ── 3. ip-api.com fallback (free, no API key) ─────────────────────────────
    if result is None:
        result = await _lookup_ipapi(ip)

    if not result:
        return {}

    # ── Cache the result to avoid repeated HTTP calls ─────────────────────────
    if redis is not None:
        try:
            import json
            await redis.setex(cache_key, _GEO_CACHE_TTL, json.dumps(result))
        except Exception:
            pass

    return result


def get_real_ip(request) -> str:
    """Extract real client IP from request, respecting proxy headers.

    Checks X-Forwarded-For first (set by nginx/load balancers), then
    X-Real-IP, then falls back to the direct connection host.

    Args:
        request: FastAPI request.

    Returns:
        IP string, or 'unknown' if none can be determined.
    """
    # X-Forwarded-For: client, proxy1, proxy2 — leftmost is the real client
    forwarded = request.headers.get("X-Forwarded-For", "")
    if forwarded:
        return forwarded.split(",")[0].strip()
    # X-Real-IP: set by some nginx configs as a single IP
    real_ip = request.headers.get("X-Real-IP", "")
    if real_ip:
        return real_ip.strip()
    return request.client.host if request.client else "unknown"


# Backward-compatible alias
_get_real_ip = get_real_ip