"""Network utility functions for interface detection."""

import ipaddress
import logging
import socket
import struct

logger = logging.getLogger(__name__)

# Interfaces to exclude from selection
EXCLUDED_INTERFACE_PREFIXES = ("lo", "docker", "br-", "veth", "virbr")


def get_network_interfaces() -> list[dict]:
    """Get all network interfaces with their IPs and subnets.

    Returns:
        List of dicts with name, ip, netmask, subnet, broadcast
    """
    interfaces = []

    try:
        import fcntl

        for iface in socket.if_nameindex():
            name = iface[1]

            # Skip excluded interfaces
            if any(name.startswith(prefix) for prefix in EXCLUDED_INTERFACE_PREFIXES):
                continue

            try:
                s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

                # Get IP address
                ip_bytes = fcntl.ioctl(
                    s.fileno(),
                    0x8915,  # SIOCGIFADDR
                    struct.pack("256s", name[:15].encode()),
                )[20:24]
                ip = socket.inet_ntoa(ip_bytes)

                # Get netmask
                netmask_bytes = fcntl.ioctl(
                    s.fileno(),
                    0x891B,  # SIOCGIFNETMASK
                    struct.pack("256s", name[:15].encode()),
                )[20:24]
                netmask = socket.inet_ntoa(netmask_bytes)

                # Calculate subnet
                network = ipaddress.IPv4Network(f"{ip}/{netmask}", strict=False)

                interfaces.append(
                    {
                        "name": name,
                        "ip": ip,
                        "netmask": netmask,
                        "subnet": str(network),
                    }
                )

                s.close()
            except OSError:
                # Interface doesn't have an IP or other error
                pass
            except Exception as e:
                logger.debug("Error getting info for interface %s: %s", name, e)

    except ImportError:
        # fcntl not available (Windows)
        logger.warning("fcntl not available, interface detection limited")
    except Exception as e:
        logger.error("Error enumerating interfaces: %s", e)

    return interfaces


def find_interface_for_ip(target_ip: str) -> dict | None:
    """Find which interface is on the same subnet as the target IP.

    Args:
        target_ip: IP address to find the matching interface for

    Returns:
        Interface dict or None if not found
    """
    try:
        target = ipaddress.IPv4Address(target_ip)
    except ValueError:
        logger.error("Invalid target IP: %s", target_ip)
        return None

    interfaces = get_network_interfaces()

    for iface in interfaces:
        try:
            network = ipaddress.IPv4Network(iface["subnet"], strict=False)
            if target in network:
                logger.debug("Found interface %s (%s) for target %s", iface["name"], iface["ip"], target_ip)
                return iface
        except ValueError:
            continue

    logger.warning("No interface found for target IP %s", target_ip)
    return None


def get_other_interfaces(exclude_ip: str) -> list[dict]:
    """Get all interfaces except the one with the given IP.

    Args:
        exclude_ip: IP address of interface to exclude

    Returns:
        List of interface dicts
    """
    interfaces = get_network_interfaces()
    return [iface for iface in interfaces if iface["ip"] != exclude_ip]