"""
Constants defining the NBUS protocol layout and addressing rules.
These values are treated as immutable configuration parameters.
"""

from typing import Final

# --- General sizes ---
NBUS_RX_META_SIZE: Final = 4
NBUS_FMT_SIZE: Final = 4
NBUS_TS_SIZE: Final = 4
NBUS_CRC_SIZE: Final = 1
NBUS_MA_SIZE: Final = 1
NBUS_SA_SIZE: Final = 1

# --- Special addresses ---
NBUS_BROADCAST_ADDR: Final = 0x00
NBUS_BRIDGE_ADDR: Final = 0xFF

# --- Packet Index Positions ---
NBUS_MA_ADDR: Final = 0
NBUS_SA_ADDR: Final = 1
NBUS_FC_ADDR: Final = 2
NBUS_DATA0_ADDR: Final = 3
NBUS_CRC_ADDR: Final = -1

# --- Bridge header ---
NBUS_BRIDGE_DATA_HDR: Final = bytearray([0x00] + [0xFF] * 8 + [0x00])
NBUS_BRIDGE_DATA_HDR_SIZE: Final = len(NBUS_BRIDGE_DATA_HDR)