import socket
from typing import Optional
from functools import lru_cache

@lru_cache(maxsize=1024)
def get_hostname(ip: str) -> Optional[str]:
    try:
        # Python's equivalent to Resolv.getname(ip)
        # returns (hostname, aliaslist, ipaddrlist)
        return socket.gethostbyaddr(ip)[0]
    except socket.error:
        return None

@lru_cache(maxsize=1024)
def get_ip(hostname: str) -> Optional[str]:
    try:
        return socket.gethostbyname(hostname)
    except socket.error:
        return None

def is_valid_hostname(hostname: str) -> bool:
    """
    Checks if a hostname resolves to an IP.
    """
    if not hostname:
        return False
    return get_ip(hostname) is not None

def to_mgt_ip(name_or_ip: str) -> Optional[str]:
    """
    Mimics the Ruby script's to_mgt_ip logic:
    1. Reverse lookup IP to get FQDN.
    2. Construct management FQDN ({host}.ds.gc.ca or .pre-ds.gc.ca).
    3. Resolve that management FQDN to an IP.
    4. Return the Management FQDN if successful.
    """
    
    # In Ruby script, input 'name' is often an IP address from the WIF source column.
    
    # Step 1: Reverse Lookup
    fqdn = get_hostname(name_or_ip)
    if not fqdn:
        # If input is already a name, use it? Ruby script assumes it gets a name from Resolv.getname(ip)
        # If name_or_ip is NOT an IP, gethostbyaddr might fail or behave differently.
        # But if it's already a name, we can try using it.
        fqdn = name_or_ip

    short_name = fqdn.split('.')[0]
    
    # Step 2 & 3: Try suffixes
    suffixes = ['.ds.gc.ca', '.pre-ds.gc.ca']
    
    for suffix in suffixes:
        mgt_dns = short_name + suffix
        resolved_ip = get_ip(mgt_dns)
        if resolved_ip:
            # Ruby: return mgt_dns if mgt_ip.to_s.length > 4
            return mgt_dns
            
    # print(f"Warning: {name_or_ip} could not be resolved to a management address.")
    return None