'''
This script outlines a conceptual Zero-Touch Provisioning (ZTP) workflow for a 5G Radio Node (gNB)
_in an O-RAN architecture. It simulates the process of a gNB automatically authenticating and
_connecting to a centralized cloud core upon power-on.

_**Disclaimer:** This is a simplified, conceptual model for illustrative purposes and does not contain
_production-ready code. It uses placeholders for actual network endpoints, credentials, and
_cryptographic functions.
'''

import requests
import json
import time
from cryptography.hazmat.primitives import serialization, hashes
from cryptography.hazmat.primitives.asymmetric import padding

# --- Configuration Placeholders ---
# In a real deployment, these would be securely managed and potentially discovered.

DHCP_SERVER_IP = "192.168.1.1"
PROVISIONING_SERVER_URL = "https://ztp.telecom-dubai.ae"
CLOUD_CORE_AMF_IP = "10.0.0.1"
GNB_SERIAL_NUMBER = "GNB-2024-TD-0001"

# --- Main ZTP Workflow ---

def initiate_ztp_workflow():
    """
    Main function to orchestrate the Zero-Touch Provisioning workflow.
    """
    print("--- Starting Zero-Touch Provisioning (ZTP) Workflow ---")

    # 1. Node Power-On & DHCP Discovery
    print("\n[1] gNB Powered On. Discovering DHCP server...")
    ip_address, provisioning_server_url = discover_dhcp(DHCP_SERVER_IP)
    if not ip_address:
        print("   - ZTP Failed: Could not obtain IP address from DHCP server.")
        return

    print(f"   - DHCP Discovery Successful. gNB IP: {ip_address}")
    print(f"   - Provisioning Server URL: {provisioning_server_url}")

    # 2. Authentication with Provisioning Server
    print("\n[2] Authenticating with Provisioning Server...")
    auth_token = authenticate_with_provisioning_server(provisioning_server_url)
    if not auth_token:
        print("   - ZTP Failed: Authentication with provisioning server failed.")
        return

    print("   - Authentication Successful. Received Auth Token.")

    # 3. Download Configuration
    print("\n[3] Downloading gNB Configuration...")
    gnb_config = download_configuration(provisioning_server_url, auth_token)
    if not gnb_config:
        print("   - ZTP Failed: Could not download configuration.")
        return

    print("   - Configuration Downloaded Successfully.")

    # 4. Connect to 5G Cloud Core
    print("\n[4] Connecting to 5G Cloud Core...")
    if connect_to_5g_core(gnb_config):
        print("   - ZTP Complete: gNB is now provisioned and connected to the 5G Core.")
    else:
        print("   - ZTP Failed: Could not connect to the 5G Core.")

# --- Helper Functions (Simulated) ---

def discover_dhcp(dhcp_server_ip):
    """
    Simulates the DHCP discovery process.
    In a real scenario, this would be a broadcast message (DHCPDISCOVER).
    """
    # Simulate a request to the DHCP server
    # In a real implementation, this would involve low-level networking
    time.sleep(1)
    return "192.168.1.100", PROVISIONING_SERVER_URL

def authenticate_with_provisioning_server(provisioning_server_url):
    """
    Simulates the authentication process with the provisioning server.
    This would typically involve mutual TLS (mTLS) with device certificates.
    """
    try:
        # In a real scenario, the gNB would present a client certificate signed by a trusted CA.
        # For this simulation, we'll use a simple token-based authentication.
        payload = {
            "serial_number": GNB_SERIAL_NUMBER,
            "authentication_type": "certificate_placeholder"
        }
        response = requests.post(f"{provisioning_server_url}/authenticate", json=payload)

        if response.status_code == 200:
            return response.json().get("auth_token")
        else:
            return None
    except requests.exceptions.RequestException as e:
        print(f"   - Error connecting to provisioning server: {e}")
        return None

def download_configuration(provisioning_server_url, auth_token):
    """
    Simulates downloading the gNB configuration from the provisioning server.
    """
    try:
        headers = {"Authorization": f"Bearer {auth_token}"}
        response = requests.get(f"{provisioning_server_url}/config/{GNB_SERIAL_NUMBER}", headers=headers)

        if response.status_code == 200:
            return response.json()
        else:
            return None
    except requests.exceptions.RequestException as e:
        print(f"   - Error downloading configuration: {e}")
        return None

def connect_to_5g_core(gnb_config):
    """
    Simulates the gNB connecting to the 5G Core (AMF).
    """
    amf_ip = gnb_config.get("amf_ip")
    plmn_id = gnb_config.get("plmn_id")

    if amf_ip and plmn_id:
        print(f"   - Establishing secure connection to AMF at {amf_ip} with PLMN ID {plmn_id}...")
        # Simulate a successful connection
        time.sleep(2)
        return True
    else:
        return False

if __name__ == "__main__":
    initiate_ztp_workflow()