import os
import random
import argparse
from datetime import datetime
from Crypto.PublicKey import RSA
from consts import PRIVATE_KEY_NAME, CERT_NAME, SPLIT_CHAR, DEFAULT_MAC


parser = argparse.ArgumentParser(description='encrypt expire date & mac address with private key')
parser.add_argument('-d', '--date', help='expire date. eg: 2020-06-06', required=True)
parser.add_argument('-m', '--mac', default=DEFAULT_MAC, help='mac address')
args = parser.parse_args()


def get_exponent_and_modulus(private_key_path):
    with open(private_key_path, 'r') as private_fp:
        private_key = RSA.import_key(private_fp.read())
    return private_key.d, private_key.n


def get_encrypt_int(mac, expire_date):
    encrypt_bytes = "{0}{3}{1}{3}{2}".format(mac, str(random.random()), expire_date, SPLIT_CHAR).encode('utf-8')
    return int.from_bytes(encrypt_bytes, byteorder='big')


def main():
    try:
        expire_date = datetime.strptime(args.date, '%Y-%m-%d')
    except Exception as e:
        print('expire date format error. eg: 2020-06-06')
        return

    if datetime.today() >= expire_date:
        print('expire date must later than today')
        return

    base_dir = os.path.dirname(os.path.abspath(__file__))
    private_key_path = os.path.join(base_dir, PRIVATE_KEY_NAME)
    output_path = os.path.join(base_dir, CERT_NAME)

    encrypt_int = get_encrypt_int(args.mac, args.date)
    d, n = get_exponent_and_modulus(private_key_path)
    signature = pow(encrypt_int, d, n)

    with open(output_path, 'wb') as fp:
        fp.write(str(signature).encode("utf-8"))


if __name__ == '__main__':
    main()