import os

from neutron_lib.utils import runtime
from oslo_config import cfg
from oslo_log import log as logging
from oslo_utils import timeutils

from neutron.conf.agent import common as config
from neutron.conf.agent.database import agents_db


if os.name == 'nt':
    from neutron.agent.windows import utils
else:
    from neutron.agent.linux import utils


LOG = logging.getLogger(__name__)
config.register_root_helper(cfg.CONF)
agents_db.register_db_agents_opts()

INTERFACE_NAMESPACE = 'neutron.interface_drivers'


create_process = utils.create_process
kill_process = utils.kill_process
execute = utils.execute
get_root_helper_child_pid = utils.get_root_helper_child_pid
pid_invoked_with_cmdline = utils.pid_invoked_with_cmdline


def load_interface_driver(conf):
    """Load interface driver for agents like DHCP or L3 agent.

    :param conf: driver configuration object
    :raises SystemExit of 1 if driver cannot be loaded
    """

    try:
        loaded_class = runtime.load_class_by_alias_or_classname(
                INTERFACE_NAMESPACE, conf.interface_driver)
        return loaded_class(conf)
    except ImportError:
        LOG.error("Error loading interface driver '%s'",
                  conf.interface_driver)
        raise SystemExit(1)


def is_agent_down(heart_beat_time):
    return timeutils.is_older_than(heart_beat_time,
                                   cfg.CONF.agent_down_time)
