_SBOX = [
    0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
    0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
    0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
    0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
    0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
    0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
    0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
    0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
    0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
    0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
    0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
    0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
    0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
    0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
    0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
    0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16,
]


def s_box(byte: int) -> int:
    """
    Substitutes a single byte using the AES S-Box.
    Args:
        byte (int): An integer value (0-255) representing the byte to be substituted.
    Returns:
        int: The substituted byte value from the AES S-Box.
    Raises:
        IndexError: If the input byte is not in the range 0-255.
    """
    if not (0 <= byte < 256):
        raise IndexError("Byte must be in the range 0-255")

    return _SBOX[byte]

def shift_rows(state: bytes) -> bytes:
    """
    Performs the ShiftRows transformation on the state.
    Args:
        state (bytes): The state to be transformed, expected to be 16 bytes long.
    Returns:
        bytes: The transformed state after applying ShiftRows.
    Raises:
        ValueError: If the input state is not 16 bytes long.
    """
    return b''.join([
        rot_bytes(state[i:i+4], i//4) for i in range(0, 16, 4)
    ])


def rot_bytes(word: bytes, n_rots: int = 1) -> bytes:
    """
    Rotates a given bytes array by one byte to the left.
    """
    return word[n_rots:] + word[:n_rots]

def sub_bytes(word: bytes) -> bytes:
    """
    Applies the S-Box substitution to each byte successively.
    """
    return bytes(s_box(byte) for byte in word)

def xor_bytes(a: bytes, b: bytes) -> bytes:
    """
    XORs two byte arrays of the same length.
    Args:
        a (bytes): First byte array.
        b (bytes): Second byte array.
    Returns:
        bytes: Resulting byte array after XOR operation.
    Raises:
        ValueError: If the lengths of the two byte arrays are not equal.
    """
    if len(a) != len(b):
        raise ValueError("Byte arrays must be of the same length")
    
    return 

_polynomial = [0x02, 0x03, 0x01, 0x01]
_mix_cols_mat = [
    _polynomial,
    rot_bytes(_polynomial, 1),
    rot_bytes(_polynomial, 2),
    rot_bytes(_polynomial, 3),
]

def _get_col(a: bytes, i: int) -> bytes:   
    return bytes(a[i + j * 4] for j in range(4))

def _xor_dot_product(a: bytes, b: bytes) -> int:
    print(f"Multiplying {a.hex()} and {b.hex()}")
    prod = [a[i]*b[i] for i in range(len(a))]
    result = prod[0]
    for i in range(len(prod)-1):
        if prod[i+1] > 0xff:
            prod[i+1] ^= 0x11b
        result ^= prod[i+1]
    return result%256

def mix_columns(state: bytes) -> bytes:
    """
    Performs the MixColumns transformation on the state.
    Args:
        state (bytes): The state to be transformed, expected to be 16 bytes long.
    Returns:
        bytes: The transformed state after applying MixColumns.
    Raises:
        ValueError: If the input state is not 16 bytes long.
    """
    new_state = bytearray(16)
    for i in range(0, 4):
        for j in range(0,4):
            new_state[j*4+i] = _xor_dot_product(
                bytes(_mix_cols_mat[j]),
                bytes(_get_col(state, i))
            )

    return bytes(new_state)
              



def get_rcon(n_rounds: int) -> list:
    """
    Generates the round constants for AES key schedule.
    (is a constant, create here for fun!)
    Returns:
        list: A list of round constants as bytes.
    """
    rc = []
    for i in range(n_rounds):
        if (i == 0):
            rc.append(0x01)
        elif (i > 0 and rc[i-1] < 128):
            rc.append(2 * rc[i - 1])
        elif (i > 0 and rc[i-1] >= 128):
            rc.append(((2 * rc[i - 1]) ^ 0x11b)%256)

    return [bytes([r, 0, 0, 0]) for r in rc]