"""MAC OUI vendor lookup."""
import csv
import logging
import os
from pathlib import Path

log = logging.getLogger(__name__)

# OUI database path
OUI_DB_PATH = Path(os.environ.get('OUI_DB_PATH', '/var/lib/esp32-web/oui.csv'))
OUI_DB_URL = 'https://standards-oui.ieee.org/oui/oui.csv'

# In-memory cache
_oui_cache: dict[str, str] = {}
_loaded = False


def _normalize_mac(mac: str) -> str:
    """Extract OUI prefix (first 6 hex chars) from MAC."""
    clean = mac.upper().replace(':', '').replace('-', '').replace('.', '')
    return clean[:6] if len(clean) >= 6 else ''


def load_oui_db(path: Path | None = None) -> int:
    """Load OUI database from CSV file."""
    global _oui_cache, _loaded

    if path is None:
        path = OUI_DB_PATH

    if not path.exists():
        log.warning('OUI database not found: %s', path)
        return 0

    _oui_cache.clear()
    count = 0

    try:
        with open(path, 'r', encoding='utf-8') as f:
            reader = csv.DictReader(f)
            for row in reader:
                # IEEE CSV format: Registry,Assignment,Organization Name,...
                assignment = row.get('Assignment', '').strip().upper()
                org = row.get('Organization Name', '').strip()
                if assignment and org:
                    _oui_cache[assignment] = org
                    count += 1
    except Exception as e:
        log.exception('Error loading OUI database: %s', e)
        return 0

    _loaded = True
    log.info('Loaded %d OUI entries from %s', count, path)
    return count


def lookup_vendor(mac: str) -> str | None:
    """Lookup vendor by MAC address."""
    global _loaded

    if not _loaded:
        load_oui_db()

    oui = _normalize_mac(mac)
    if not oui:
        return None

    return _oui_cache.get(oui)


def download_oui_db(path: Path | None = None) -> bool:
    """Download OUI database from IEEE."""
    import urllib.request

    if path is None:
        path = OUI_DB_PATH

    path.parent.mkdir(parents=True, exist_ok=True)

    try:
        log.info('Downloading OUI database from %s', OUI_DB_URL)
        urllib.request.urlretrieve(OUI_DB_URL, path)
        log.info('OUI database saved to %s', path)
        return True
    except Exception as e:
        log.exception('Error downloading OUI database: %s', e)
        return False