import os
from subprocess import check_call

from charms.layer import snap
from charms.leadership import leader_get, leader_set
from charms.reactive import (
    clear_flag,
    data_changed,
    hook,
    set_flag,
    set_state,
    when,
    when_not,
)

from charmhelpers.core import hookenv
from charmhelpers.core.host import is_container
from charmhelpers.core.sysctl import create as create_sysctl
from charms.layer.kubernetes_common import arch


@hook("upgrade-charm")
def upgrade_charm():
    clear_flag("kubernetes.cni-plugins.installed")


@when_not("kubernetes.cni-plugins.installed")
def install_cni_plugins():
    """Unpack the cni-plugins resource"""
    hookenv.status_set("maintenance", "Installing CNI plugins")

    # Get the resource via resource_get
    try:
        resource_name = "cni-{}".format(arch())
        archive = hookenv.resource_get(resource_name)
    except Exception:
        message = "Error fetching the cni resource."
        hookenv.log(message)
        return

    if not archive:
        hookenv.log("Missing cni resource.")
        return

    # Handle null resource publication, we check if filesize < 1mb
    filesize = os.stat(archive).st_size
    if filesize < 1000000:
        hookenv.log("Incomplete cni resource.")
        return

    unpack_path = "/opt/cni/bin"
    os.makedirs(unpack_path, exist_ok=True)
    cmd = ["tar", "xfvz", archive, "-C", unpack_path]
    hookenv.log(cmd)
    check_call(cmd)

    set_flag("kubernetes.cni-plugins.installed")


@when("kubernetes-node.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("kubernetes-node.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,
        )


@when("config.changed.labels")
def handle_labels_changed():
    set_state("node.label-config-required")