"""The MyIni2CK container: magic, XOR scrambling, A2F compression.

Boxsim uses one container for project files (`.bpj`) and driver files (`.bch`).
"""

from __future__ import annotations

from . import a2f
from .krypt import unscramble

MAGIC = b"MyIni2CK"


class ContainerError(ValueError):
    pass


def is_container(raw: bytes) -> bool:
    return raw[: len(MAGIC)] == MAGIC


def decode(raw: bytes) -> bytes:
    """Decode a Boxsim container to its raw INI payload."""
    if not is_container(raw):
        raise ContainerError(
            f"not a MyIni2CK file (magic {raw[:8]!r}, expected {MAGIC!r})"
        )
    # The compressed layer reads its own 8 byte header back, so hand it the
    # magic followed by the descrambled body exactly as Boxsim does.
    return a2f.expand(MAGIC + unscramble(raw[len(MAGIC) :]))


def decode_text(raw: bytes) -> str:
    """Decode to text. Boxsim writes Windows-1252 with CRLF line ends."""
    return decode(raw).decode("cp1252")