"""Write an Atari .car cartridge image (CART header + ROM)."""

from __future__ import annotations

import struct

TYPE_STD_16K = 2                 # "Standard 16 KB cartridge"


def write_car(rom: bytes, path: str, cart_type: int = TYPE_STD_16K) -> str:
    """Wrap a cart `rom` in the .car container (16-byte CART header + ROM).
    The header holds the cartridge type and a checksum (sum of all ROM bytes)."""
    header = bytearray(16)
    header[0:4] = b"CART"
    struct.pack_into(">I", header, 4, cart_type)
    struct.pack_into(">I", header, 8, sum(rom) & 0xFFFFFFFF)
    with open(path, "wb") as f:
        f.write(header)
        f.write(rom)
    return path