salt_the_spire.py

#!/usr/bin/env python3

"""
Author: jessijzhao
Date: November 29, 2020

Decodes or encodes save files for Slay the Spire.
"""

import argparse
import base64
from itertools import cycle


def xor_key(bstring: bytes, key: bytes = b"key") -> bytes:
    """
    Args:
        bstring: bytestring to xor with cyclic key
        key: key phrase (actually just "key")

    Returns the XOR of the input text and the key phrase ("key").
    """
    return bytes(_a ^ _b for _a, _b in zip(bstring, cycle(key)))


def decode(inbytes: bytes) -> bytes:
    """
    Args:
        inbytes: bytes to decode

    Returns decoded bytes representing a human-readable JSON.
    """
    return xor_key(base64.b64decode(inbytes))


def encode(inbytes: bytes) -> bytes:
    """
    Args:
        inbytes: bytes to encode

    Returns encoded bytes in Slay the Spire save file format.
    """
    return base64.b64encode(xor_key(inbytes))


def main() -> None:

    parser = argparse.ArgumentParser()

    # whether to decode or encode save file
    group = parser.add_mutually_exclusive_group(required=True)
    group.add_argument("-d", "--decode", action="store_true", help="decode save file")
    group.add_argument("-e", "--encode", action="store_true", help="encode save file")

    # which files to read from / write to
    parser.add_argument(
        "input", type=argparse.FileType("rb"), help="save file to decode/encode"
    )
    parser.add_argument(
        "output",
        type=argparse.FileType("wb"),
        help="file to store decoded/encoded save file",
    )

    args = parser.parse_args()

    inbytes = args.input.read()
    args.input.close()

    if args.decode:
        outbytes = decode(inbytes)
    elif args.encode:
        outbytes = encode(inbytes)
    else:
        raise RuntimeError

    args.output.write(outbytes)
    args.output.close()


if __name__ == "__main__":
    main()