Handling the # TODO: Handle failure in the _IRQ_ENCRYPTION_UPDATE event

Start by tracing _security_irq and DeviceConnection._connected, then compare the reported status values with bluetooth.h and the existing connection and pairing event handling. Determine the expected behavior for encryption failures, disconnections, missing connections, and pairing events; done means the application receives consistent, documented outcomes for each case.

I am using the btstack for the PICO_W. We have needed to do significant work to add pairing/encryption support from the BtStack but for the most part I think we have got the basics working. What I need to know is what to do with the aioble objects when errors occur. I have modified the code a little (slowly adding typing as I learn what things are) to look as follows:

pair_status: int = -1
def _security_irq(event: int, data: tuple[int, bool, bool, bool, int, int]):
    global _modified
    global pair_status

    if event == _IRQ_ENCRYPTION_UPDATE:
        pair_status = -1
        # Connection has updated (usually due to pairing).
        conn_handle, encrypted, authenticated, bonded, key_size, status = data
        pair_status = status
        logger.info("LNI: AIOBLE: encryption update") # type: ignore
        if connection := DeviceConnection._connected.get(conn_handle, None):
            logger.info(f'LNI: AIOBLE: Event triggered. Pairing status: {pair_status}') # type: ignore
            connection.encrypted = encrypted
            connection.authenticated = authenticated
            connection.bonded = bonded
            connection.key_size = key_size
            if pair_status == 19: #ERROR_CODE_REMOTE_USER_TERMINATED_CONNECTION (in Bt Stack code - not so in MP code)
                del DeviceConnection._connected[conn_handle]  # Signal as disconnected

            # TODO: Handle failure.
            #if encrypted and connection._pair_event:
            connection._pair_event.set()

I am assuming the status values are those defined in the btstack file bluetooth.h such that status value 0x13 is, for example, ERROR_CODE_REMOTE_USER_TERMINATED_CONNECTION

What I dont know is exactly what to do in each case. Is the del DeviceConnection._connected[conn_handle] sufficient for the ERROR_CODE_REMOTE_USER_TERMINATED_CONNECTION case? Should I always set the event if the connection is not None?

What should be done if if connection := DeviceConnection._connected.get(conn_handle, None) gives None?

Are there certain exceptions I should raise to inform the application or do I need to create one?