#!/usr/bin/python3
# -*- coding: utf-8 -*-

# Public Key Generator
# https://www.nostarch.com/crackingcodes/ (BSD Licensed)

import random, sys, os, primeNum, cryptomath
from typing import Tuple


def main() -> None:
    # Create a public/private keypair with 1024 bit keys:
    print("Making key files...")
    makeKeyFiles("al_sweigart", 1024)
    print("Key files made.")


def generateKey(keySize: int) -> Tuple[Tuple[int, int], Tuple[int, int]]:
    # Creates a public/private keys keySize bits in size.
    p = 0
    q = 0
    # Step 1: Create two prime numbers, p and q. Calculate n = p * q.
    print("Generating p & q primes...")
    while p == q:
        p = primeNum.generateLargePrime(keySize)
        q = primeNum.generateLargePrime(keySize)
    n = p * q

    # Step 2: Create a number e that is relatively prime to (p-1)*(q-1):
    print("Generating e that is relatively prime to (p-1)*(q-1)...")
    phiN = (p - 1) * (q - 1)
    while True:
        # Keep trying random numbers for e until one is valid:
        e = random.randrange(2 ** (keySize - 1), 2 ** (keySize))
        if cryptomath.gcd(e, phiN) == 1:
            break

    # Step 3: Calculate d, the mod inverse of e:
    print("Calculating d that is mod inverse of e...")
    d = cryptomath.findModInverse(e, phiN)

    publicKey = (n, e)
    privateKey = (n, d)

    print("Public key:", publicKey)
    print("Private key:", privateKey)

    return (publicKey, privateKey)


def makeKeyFiles(name: str, keySize: int) -> None:
    # Creates two files 'x_pubkey.txt' and 'x_privkey.txt' (where x
    # is the value in name) with the n,e and d,e integers written in
    # them, delimited by a comma.

    # Our safety check will prevent us from overwriting our old key files:
    if os.path.exists("%s_pubkey.txt" % (name)) or os.path.exists(
        "%s_privkey.txt" % (name)
    ):
        sys.exit(
            "Files %s_pubkey.txt or %s_privkey.txt already exists! Use a different name, or delete keys and re-run."
            % (name, name)
        )

    publicKey, privateKey = generateKey(keySize)

    print(
        "\nThe public key is a %s and a %s digit number."
        % (len(str(publicKey[0])), len(str(publicKey[1])))
    )
    print("Writing public key to file %s_pubkey.txt..." % (name))
    with open("%s_pubkey.txt" % (name), "w") as fo:
        fo.write("%s,%s,%s" % (keySize, publicKey[0], publicKey[1]))

    print(
        "\nThe private key is a %s and a %s digit number."
        % (len(str(publicKey[0])), len(str(publicKey[1])))
    )
    print("Writing private key to file %s_privkey.txt..." % (name))
    with open("%s_privkey.txt" % (name), "w") as fo:
        fo.write("%s,%s,%s" % (keySize, privateKey[0], privateKey[1]))


# If makePublicPrivateKeys.py is run (instead of imported as a module),
# call the main() function:
if __name__ == "__main__":
    main()