def setup_sniff_tcpdump_parser(parser_sniff):
    # arguments which will be passed to tcpdump
    parser_sniff_tcpdump = parser_sniff.add_argument_group('tcpdump arguments')
    # TODO: tcpdump_parser.add_argument('-c', '--count', re)
    parser_sniff_tcpdump.add_argument('-a', '--ip-address=', help='IP address of the device to sniff', dest='device_ip')
    parser_sniff_tcpdump.add_argument('-i', '--interface=', help='Interface of the capture device.', dest='capture_interface',default='')
    parser_sniff_tcpdump.add_argument('-I', '--monitor-mode', help='Put interface into monitor mode',
                                      action='store_true')
    parser_sniff_tcpdump.add_argument('-n', help='Deactivate name resolution. Option is set by default.',
                                      action='store_true')
    parser_sniff_tcpdump.add_argument('-#', '--number',
                                      help='Print packet number at beginning of line. Set by default.',
                                      action='store_true')
    parser_sniff_tcpdump.add_argument('-e', help='Print link layer headers. Option is set by default.',
                                      action='store_true')
    parser_sniff_tcpdump.add_argument('-t', action='count', default=0,
                                      help='Please see tcpdump manual for details. Unused by default.')


def setup_sniff_parser(subparsers):
    # create parser for 'sniff' command
    parser_sniff = subparsers.add_parser('sniff', help='Start tcpdump capture.')
    setup_sniff_tcpdump_parser(parser_sniff)
    setup_pcap_filter_parser(parser_sniff)
    cap_size_group = parser_sniff.add_mutually_exclusive_group(required=True)
    cap_size_group.add_argument('-c', '--count', type=int, help='Number of packets to capture.', default=0)
    cap_size_group.add_argument('--mins', type=int, help='Time in minutes to capture.', default=60)


def setup_pcap_filter_parser(parser_sniff):
    parser_pcap_filter = parser_sniff.add_argument_parser('pcap-filter expression')
    pass

def check_iottb_env():
    # This makes the option '--root-dir' obsolescent # TODO How to streamline this?\
    try:
        iottb_home = environ['IOTTB_HOME']  # TODO WARN implicit declaration of env var name!
    except KeyError:
        logger.error(f"Environment variable 'IOTTB_HOME' is not set."
                     f"Setting environment variable 'IOTTB_HOME' to '~/{IOTTB_HOME_ABS}'")
        environ['IOTTB_HOME'] = IOTTB_HOME_ABS
    finally:
        if not Path(IOTTB_HOME_ABS).exists():
            print(f'"{IOTTB_HOME_ABS}" does not exist.')
            response = input('Do you want to create it now? [y/N]')
            logger.debug(f'response: {response}')
            if response.lower() != 'y':
                logger.debug(f'Not setting "IOTTB_HOME"')
                print('TODO')
                print("Aborting execution...")
                return ReturnCodes.ABORTED
            else:
                print(f'Setting environment variable IOTTB_HOME""')
                Path(IOTTB_HOME_ABS).mkdir(parents=True,
                                           exist_ok=False)  # Should always work since in 'not exist' code path
                return ReturnCodes.SUCCESS
        logger.info(f'"{IOTTB_HOME_ABS}" exists.')
        # TODO: Check that it is a valid iottb dir or can we say it is valid by definition if?
        return ReturnCodes.SUCCESS