import socket
import requests

def generate_node_nickname():
    """
    Generates a temporary unit registration ID in the format:
    "Node-{last octet of local IP}-{last octet of public IP}".

    This ID is intended for initial unit registration and will be replaced
    by a server-generated GUID upon assignment.

    Returns:
        str: The formatted registration ID.
    """
    local_ip_octet = "unknown"
    public_ip_octet = "unknown"

    # Get the last octet of the local IP address
    try:
        # Create a UDP socket
        s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
        # Connect to an external host (Google's DNS) to get the local IP
        # This doesn't send any data, just establishes a connection for getsockname()
        s.connect(("1.1.1.1", 80))
        local_ip = s.getsockname()[0]
        s.close()
        local_ip_octet = local_ip.split('.')[-1]
    except Exception as e:
        print(f"Warning: Could not determine local IP address. Error: {e}")

    # Get the last octet of the public IP address using an external service
    try:
        # Use ipify.org to get the public IP (a widely used, simple service)
        response = requests.get('https://api.ipify.org?format=json')
        response.raise_for_status()  # Raise an HTTPError for bad responses (4xx or 5xx)
        public_ip = response.json()['ip']
        public_ip_octet = public_ip.split('.')[-1]
    except requests.exceptions.RequestException as e:
        print(f"Warning: Could not determine public IP address. Error: {e}")
    except ValueError as e:
        print(f"Warning: Could not parse public IP response. Error: {e}")

    return f"Node-{local_ip_octet}-{public_ip_octet}"