Decryptor for the Fortnite Chapter 4, Season 1 / 2 encrypted Cipher Quests

fortnite-decrypt.py

#!/usr/bin/env python3

#
# Decryptor for the Fortnite Chapter 4, Season 1 / 2 encrypted Cipher Quests.
#
# The scheme for the encryption has been described here:
#   https://twitter.com/realNumberSets/status/1630581327018831883
#
# Example:
#
# % ./fortnite-decrypt.py 19.19.19.1.27. 1.22. 22.16.15.10.20.21. 2.17.26.12
# SPRAY AT SPLITS BOWL
#

import sys

inputStrings = " ".join(sys.argv[1:]).split(" ")
keyNumberStrings = "0.3.1.0.2.0.2.3".split(".")

# Encryption starts with letter A, at position 1
base = ord('A') - 1

result = ""
keyIndex = 0
for inputString in inputStrings:
    numberStrings = inputString.split(".")
    for numberString in numberStrings:
        if numberString.strip() == "":
            continue
        keyNumberString = keyNumberStrings[keyIndex % len(keyNumberStrings)]
        keyIndex += 1
        result += chr(base + int(numberString) - int(keyNumberString))
    result += " "

print(result)