def match_device()

in src/mount_efs/__init__.py [0:0]
50 lines of code
11 McCabe index (conditional complexity)

def match_device(config, device, options):
    """Return the EFS id, the remote path, and the az to mount"""

    try:
        remote, path = device.split(":", 1)
    except ValueError:
        remote = device
        path = "/"

    if FS_ID_RE.match(remote):
        return remote, path, None

    try:
        primary, secondaries, _ = socket.gethostbyname_ex(remote)
        hostnames = list(filter(lambda e: e is not None, [primary] + secondaries))
    except socket.gaierror:
        create_default_cloudwatchlog_agent_if_not_exist(config, options)
        fatal_error(
            'Failed to resolve "%s" - check that the specified DNS name is a CNAME record resolving to a valid EFS DNS '
            "name" % remote,
            'Failed to resolve "%s"' % remote,
        )

    if not hostnames:
        create_default_cloudwatchlog_agent_if_not_exist(config, options)
        fatal_error(
            'The specified domain name "%s" did not resolve to an EFS mount target'
            % remote
        )

    for hostname in hostnames:
        efs_fqdn_match = EFS_FQDN_RE.match(hostname)

        if efs_fqdn_match:
            az = efs_fqdn_match.group("az")
            fs_id = efs_fqdn_match.group("fs_id")

            if az and "az" in options and az != options["az"]:
                fatal_error(
                    'The hostname "%s" resolved by the specified domain name "%s" does not match the az provided in the '
                    "mount options, expected = %s, given = %s"
                    % (hostname, remote, options["az"], az)
                )

            expected_dns_name, _ = get_dns_name_and_fallback_mount_target_ip_address(
                config, fs_id, add_field_in_options(options, "az", az)
            )

            # check that the DNS name of the mount target matches exactly the DNS name the CNAME resolves to
            if hostname == expected_dns_name:
                return fs_id, path, az
    else:
        create_default_cloudwatchlog_agent_if_not_exist(config, options)
        fatal_error(
            'The specified CNAME "%s" did not resolve to a valid DNS name for an EFS mount target. '
            "Please refer to the EFS documentation for mounting with DNS names for examples: %s"
            % (
                remote,
                "https://docs.aws.amazon.com/efs/latest/ug/mounting-fs-mount-cmd-dns-name.html",
            )
        )