import os
import re
import logging
from typing import Optional

import yaml

logger = logging.getLogger(__name__)

_MAC_RE = re.compile(r"^([0-9a-fA-F]{2}:){5}[0-9a-fA-F]{2}$")

_REQUIRED_CONFIG_KEYS = ["network", "server", "database", "rate_limiting", "profile"]


def validate_mac(mac: str) -> bool:
    """Return True if mac is a valid colon-separated MAC address."""
    return bool(mac and _MAC_RE.match(mac))


def normalize_mac(mac: str) -> str:
    """Return a lowercase, colon-separated MAC address.

    Accepts input with dashes, dots, or no separators.
    """
    clean = mac.lower().replace("-", ":").replace(".", ":")
    # Handle 12-char no-separator format
    if ":" not in clean and len(clean) == 12:
        clean = ":".join(clean[i : i + 2] for i in range(0, 12, 2))
    return clean


def validate_imsi(imsi: str) -> bool:
    """Return True if imsi is exactly 15 decimal digits."""
    return bool(imsi) and imsi.isdigit() and len(imsi) == 15


def validate_op_key(op_key: str) -> bool:
    """Return True if op_key is a 16-byte (32 hex digit) hex string."""
    if not isinstance(op_key, str) or len(op_key) != 32:
        return False
    try:
        bytes.fromhex(op_key)
    except ValueError:
        return False
    return True


def load_config(path: str) -> dict:
    """Load and minimally validate a YAML config file."""
    if not os.path.exists(path):
        raise FileNotFoundError(f"Config file not found: {path}")
    with open(path) as f:
        cfg = yaml.safe_load(f)
    if not isinstance(cfg, dict):
        raise ValueError(f"Config file is empty or not a mapping: {path}")
    for key in _REQUIRED_CONFIG_KEYS:
        if key not in cfg:
            raise ValueError(f"Missing required config section: '{key}'")
    op_key = cfg["network"].get("op_key")
    if not validate_op_key(op_key):
        raise ValueError(
            "network.op_key must be a 16-byte hex string (32 hex digits)"
        )
    return cfg


def ensure_parent_dir(path: str) -> None:
    """Create the parent directory of ``path`` if it has one.

    Guards against ``os.makedirs("")`` raising FileNotFoundError when ``path``
    is a bare filename with no directory component.
    """
    parent = os.path.dirname(path)
    if parent:
        os.makedirs(parent, exist_ok=True)


def hex_to_bytes(h: str) -> bytes:
    return bytes.fromhex(h)


def bytes_to_hex(b: bytes) -> str:
    return b.hex()


def get_client_ip(request) -> str:
    """Return the real client IP, respecting X-Forwarded-For from nginx."""
    forwarded = request.headers.get("X-Forwarded-For")
    if forwarded:
        return forwarded.split(",")[0].strip()
    return request.remote_addr or ""


def get_mac_from_arp(ip: str, arp_path: str = "/proc/net/arp") -> Optional[str]:
    """Attempt to resolve a MAC address from the ARP table for the given IP."""
    try:
        with open(arp_path) as f:
            for line in f:
                parts = line.split()
                if len(parts) >= 4 and parts[0] == ip:
                    mac = parts[3]
                    if validate_mac(mac):
                        return normalize_mac(mac)
    except Exception as exc:
        logger.debug(f"ARP lookup failed for {ip}: {exc}")
    return None