from charms.layer import snap
from charms.leadership import (
    leader_get,
    leader_set
)
from charms.reactive import (
    when,
    when_not,
    when_any,
    data_changed
)

from charmhelpers.core import hookenv
from charmhelpers.core.host import is_container
from charmhelpers.core.sysctl import create as create_sysctl


@when_any('kubernetes-master.snaps.installed',
          'kubernetes-worker.snaps.installed')
@when('snap.refresh.set')
@when('leadership.is_leader')
def process_snapd_timer():
    """
    Set the snapd refresh timer on the leader so all cluster members
    (present and future) will refresh near the same time.

    :return: None
    """
    # Get the current snapd refresh timer; we know layer-snap has set this
    # when the 'snap.refresh.set' flag is present.
    timer = snap.get(
        snapname='core', key='refresh.timer').decode('utf-8').strip()
    if not timer:
        # The core snap timer is empty. This likely means a subordinate timer
        # reset ours. Try to set it back to a previously leader-set value,
        # falling back to config if needed. Luckily, this should only happen
        # during subordinate install, so this should remain stable afterward.
        timer = leader_get('snapd_refresh') or hookenv.config('snapd_refresh')
        snap.set_refresh_timer(timer)

        # Ensure we have the timer known by snapd (it may differ from config).
        timer = snap.get(
            snapname='core', key='refresh.timer').decode('utf-8').strip()

    # The first time through, data_changed will be true. Subsequent calls
    # should only update leader data if something changed.
    if data_changed('snapd_refresh', timer):
        hookenv.log('setting leader snapd_refresh timer to: {}'.format(timer))
        leader_set({'snapd_refresh': timer})


@when_any('kubernetes-master.snaps.installed',
          'kubernetes-worker.snaps.installed')
@when('snap.refresh.set')
@when('leadership.changed.snapd_refresh')
@when_not('leadership.is_leader')
def set_snapd_timer():
    """
    Set the snapd refresh.timer on non-leader cluster members.

    :return: None
    """
    # NB: This method should only be run when 'snap.refresh.set' is present.
    # Layer-snap will always set a core refresh.timer, which may not be the
    # same as our leader. Gating with 'snap.refresh.set' ensures layer-snap
    # has finished and we are free to set our config to the leader's timer.
    timer = leader_get('snapd_refresh') or ''  # None will error
    hookenv.log('setting snapd_refresh timer to: {}'.format(timer))
    snap.set_refresh_timer(timer)


@when('config.changed.sysctl')
def write_sysctl():
    """
    :return: None
    """
    sysctl_settings = hookenv.config('sysctl')
    if sysctl_settings and not is_container():
        create_sysctl(
            sysctl_settings,
            '/etc/sysctl.d/50-kubernetes-charm.conf',
            # Some keys in the config may not exist in /proc/sys/net/.
            # For example, the conntrack module may not be loaded when
            # using lxd drivers insteam of kvm. In these cases, we
            # simply ignore the missing keys, rather than making time
            # consuming calls out to the filesystem to check for their
            # existence.
            ignore=True)