#!/usr/bin/env python3
import sys
import requests
import json
import time
import warnings
from datetime import date

warnings.filterwarnings("ignore", category=DeprecationWarning)
import telnetlib

TELNET_PORT = 23

def pass_of_the_day():
    def gcd(a, b):
        return a if not b else gcd(b, a % b)

    curdate = date.today()
    month, day = curdate.month, curdate.day
    return f"{month:x}{month:02}-{day:02x}{gcd(month, day):02}"


def enable_telnet(nas_ip):
    url = f"http://{nas_ip}:5000/webman/start_telnet.cgi"

    try:
        res = requests.get(url)
        response = res.json()

        if res.status_code == 200:
            response = res.json()
            if "success" in response:
                return response["success"]
            else:
                print(f"WARNING: got unexpected response from NAS:\n"
                      f"{json.dumps(response, indent=4)}")
                return False
        else:
            print(f"ERROR: NAS returned http error {res.status_code}")
            return False
    except Exception as e:
        print(f"ERROR: got exception {e}")

    return False


def telnet_try_login(telnet, password):
    # Wait for login prompt
    telnet.read_until(b"login: ")
    telnet.write("root".encode("ascii") + b'\n')

    # Wait for password prompt
    telnet.read_until(b"Password: ")
    telnet.write(password.encode("ascii") + b'\n')

    login_succeeded = True

    for i in range(5):
        # skip the remote side wrong password delay and crap it sends
        line = telnet.read_until(b'\n', 1)
        if not line or line == b"\r\n":
            continue

        if b"Login incorrect" in line:
            login_succeeded = False
            break

        # consider NAS telnet prompt as successful login
        if len(line) > 30:
            break

    return login_succeeded


def exec_cmd_via_telnet(host, port, command):
    no_rtc_pass = "101-0101"

    try:
        telnet = telnetlib.Telnet(host, port, timeout=10)
        print(f"INFO: connected via telnet to {host}:{port}")

        rc = telnet_try_login(telnet, pass_of_the_day())
        if not rc:
            print("INFO: password of the day didn't work, retrying with "
                  "the 'no RTC' password")
            rc = telnet_try_login(telnet, no_rtc_pass)

        if rc:
            print("INFO: telnet login successful")
        else:
            print("ERROR: telnet login failed")
            return False

        # flush lengthy NAS telnet prompt
        telnet.read_until(b"built-in shell (ash)", 1)

        # Run the command
        telnet.write(command.encode("ascii") + b'\n')

        time.sleep(1)

        telnet.write(b"exit\n")  # Close the session

        # Read output (if any)
        #output = telnet.read_all().decode("ascii")
        print("INFO: command executed. Telnet session closed.")
        #print("DEBUG: output:\n", output)

    except Exception as e:
        print("Telnet error:", e)
        return False

    return True


def main():
    if len(sys.argv) != 2:
        print(f"Usage:\npython3 {sys.argv[0]} <NAS_IP>")
        return -1

    nas_ip = sys.argv[1]

    rc = enable_telnet(nas_ip)
    if rc:
        print("INFO: successfully enabled telnet on NAS")
    else:
        print("ERROR: failed to enable telnet, stopping")
        return -1

    rc = exec_cmd_via_telnet(nas_ip, TELNET_PORT,
                             "while true; do touch /tmp/installable_check_pass; sleep 1; done &")

    return 0 if rc else -1


if __name__ == "__main__":
    exit(main())