from __future__ import annotations

import argparse


XFALCON_PREFIX = "HUDR_sFnX+n5uAUNVsMPNK3DOP5wnti1Lc8Axjy5z88T61A=="
TEMP_VAR_XOR = bytes.fromhex("22eb4780")
TEMP_TE_TEMPLATE = bytes.fromhex(
    "4b54cdabab77585a3a250077585a3a25000107020037df98acba"
    "00000000"
    "1eae285989015a563eda7b563efb00"
)


def xfalcon_te_raw_from_digest_hex(digest_hex: str) -> bytes:
    digest_hex = digest_hex.strip().lower()
    if len(digest_hex) != 64 or any(c not in "0123456789abcdef" for c in digest_hex):
        raise ValueError("digest_hex must be 64 lowercase/uppercase hex chars")

    temp = bytearray(TEMP_TE_TEMPLATE)
    digest_ascii4 = digest_hex[:4].encode("ascii")
    temp[26:30] = bytes(a ^ b for a, b in zip(digest_ascii4, TEMP_VAR_XOR))
    checksum = (-(0x9F + sum(temp[2:44]))) & 0xFF
    return bytes(b ^ checksum for b in temp)


def xfalcon_te_hex_from_digest_hex(digest_hex: str) -> str:
    return xfalcon_te_raw_from_digest_hex(digest_hex).hex()


def xfalcon_value_from_digest_hex(digest_hex: str) -> str:
    return f"{XFALCON_PREFIX}$TE_{xfalcon_te_hex_from_digest_hex(digest_hex)}"


def main() -> int:
    parser = argparse.ArgumentParser()
    parser.add_argument("digest_hex")
    parser.add_argument("--value", action="store_true", help="print full __NS_xfalcon value")
    args = parser.parse_args()

    if args.value:
        print(xfalcon_value_from_digest_hex(args.digest_hex))
    else:
        print(xfalcon_te_hex_from_digest_hex(args.digest_hex))
    return 0


if __name__ == "__main__":
    raise SystemExit(main())