"""Plugin: ASN lookup using MaxMind GeoLite2-ASN mmdb."""

from __future__ import annotations

import ipaddress
import logging
from pathlib import Path

from derp.plugin import command

log = logging.getLogger(__name__)

_DB_PATHS = [
    Path("data/GeoLite2-ASN.mmdb"),
    Path("/usr/share/GeoIP/GeoLite2-ASN.mmdb"),
    Path.home() / ".local" / "share" / "GeoIP" / "GeoLite2-ASN.mmdb",
]

_reader = None


def _get_reader():
    """Lazy-load the mmdb reader."""
    global _reader
    if _reader is not None:
        return _reader
    try:
        import maxminddb
    except ImportError:
        log.error("maxminddb package not installed")
        return None
    for path in _DB_PATHS:
        if path.is_file():
            _reader = maxminddb.open_database(str(path))
            log.info("asn: loaded %s", path)
            return _reader
    log.warning("asn: no GeoLite2-ASN.mmdb found")
    return None


@command("asn", help="ASN lookup: !asn <ip>")
async def cmd_asn(bot, message):
    """Look up the Autonomous System Number for an IP address.

    Usage:
        !asn 8.8.8.8
    """
    parts = message.text.split(None, 2)
    if len(parts) < 2:
        await bot.reply(message, "Usage: !asn <ip>")
        return

    addr = parts[1]
    try:
        ip = ipaddress.ip_address(addr)
    except ValueError:
        await bot.reply(message, f"Invalid IP address: {addr}")
        return

    if ip.is_private or ip.is_loopback:
        await bot.reply(message, f"{addr}: private/loopback address")
        return

    reader = _get_reader()
    if reader is None:
        await bot.reply(message, "ASN database not available (run update-data)")
        return

    try:
        rec = reader.get(str(ip))
    except Exception as exc:
        await bot.reply(message, f"Lookup error: {exc}")
        return

    if not rec:
        await bot.reply(message, f"{addr}: no ASN data")
        return

    asn = rec.get("autonomous_system_number", "")
    org = rec.get("autonomous_system_organization", "")

    if asn:
        await bot.reply(message, f"{addr}: AS{asn} ({org})" if org else f"{addr}: AS{asn}")
    else:
        await bot.reply(message, f"{addr}: no ASN data")