from typing import List, Optional
import logging
import os

# ---- Logging ----------------------------------------------------------
logger = logging.getLogger("af_packet_sniffer")

# -------------------------
# Interface / bridge helpers
# -------------------------

def check_interface_exists(iface: str) -> bool:
    """
    Check for the presence of a network interface by testing sysfs.
    Returns True if /sys/class/net/<iface> exists.
    """
    return os.path.isdir(f"/sys/class/net/{iface}")


def check_interface_up(iface: str) -> bool:
    """
    Check whether the given interface is administratively/operationally up
    by reading /sys/class/net/<iface>/operstate.
    Returns False if the path does not exist.
    """
    try:
        with open(f"/sys/class/net/{iface}/operstate", "r") as f:
            return f.read().strip() == "up"
    except FileNotFoundError:
        return False


def _read_sysfs_text(path: str) -> Optional[str]:
    """Read one sysfs file and return stripped text, or `None` if unavailable."""
    try:
        with open(path, "r") as f:
            return f.read().strip()
    except FileNotFoundError:
        return None
    except Exception:
        logger.exception("Error reading sysfs path %s", path)
        return None


def read_interface_operstate(iface: str) -> Optional[str]:
    """Return the kernel operstate string for an interface."""
    return _read_sysfs_text(f"/sys/class/net/{iface}/operstate")


def read_interface_carrier(iface: str) -> Optional[bool]:
    """Return the carrier state for an interface if available."""
    value = _read_sysfs_text(f"/sys/class/net/{iface}/carrier")
    if value is None:
        return None

    try:
        return int(value, 10) == 1
    except ValueError:
        logger.warning("Unexpected carrier value for %s: %r", iface, value)
        return None


def read_interface_admin_up(iface: str) -> Optional[bool]:
    """Return whether the interface has the IFF_UP flag set."""
    value = _read_sysfs_text(f"/sys/class/net/{iface}/flags")
    if value is None:
        return None

    try:
        return bool(int(value, 0) & 0x1)
    except ValueError:
        logger.warning("Unexpected flags value for %s: %r", iface, value)
        return None


def _read_bridge_ports_from_sysfs(bridge: str) -> List[str]:
    """
    Read bridge member interfaces from sysfs. Internal helper that always reads.
    """
    base = f"/sys/class/net/{bridge}/brif/"
    if not os.path.isdir(base):
        return []

    try:
        ports = [p for p in os.listdir(base) if check_interface_exists(p)]
    except Exception:
        logger.exception("Error reading bridge ports for %s", bridge)
        ports = []
    return ports


def get_bridge_ports_once(bridge: str) -> List[str]:
    """
    Convenience: read bridge ports (no caching here) used when preparing the fixed snapshot.
    """
    return _read_bridge_ports_from_sysfs(bridge)