import os
import errno
from . import base
from .decorators import *
import tuned.logs
from tuned.plugins import exceptions
from tuned.utils.commands import commands

log = tuned.logs.get()

class SelinuxPlugin(base.Plugin):
	"""
	Plug-in for tuning SELinux options.

	SELinux decisions, such as allowing or denying access, are
	cached. This cache is known as the Access Vector Cache (AVC). When
	using these cached decisions, SELinux policy rules need to be checked
	less, which increases performance. The [option]`avc_cache_threshold`
	option allows adjusting the maximum number of AVC entries.

	NOTE: Prior to changing the default value, evaluate the system
	performance with care. Increasing the value could potentially
	decrease the performance by making AVC slow.

	.Increase the AVC cache threshold for hosts with containers.
	====
	----
	[selinux]
	avc_cache_threshold=8192
	----
	====
	"""

	@classmethod
	def _get_selinux_path(self):
		path = "/sys/fs/selinux"
		if not os.path.exists(path):
			path = "/selinux"
			if not os.path.exists(path):
				path = None
		return path

	def __init__(self, *args, **kwargs):
		self._cmd = commands()
		self._selinux_path = self._get_selinux_path()
		if self._selinux_path is None:
			raise exceptions.NotSupportedPluginException("SELinux is not enabled on your system or incompatible version is used.")
		self._cache_threshold_path = os.path.join(self._selinux_path, "avc", "cache_threshold")
		super(SelinuxPlugin, self).__init__(*args, **kwargs)

	@classmethod
	def _get_config_options(self):
		return {
			"avc_cache_threshold" : None,
		}

	def _instance_init(self, instance):
		instance._has_static_tuning = True
		instance._has_dynamic_tuning = False

	def _instance_cleanup(self, instance):
		pass

	@command_set("avc_cache_threshold")
	def _set_avc_cache_threshold(self, value, instance, sim, remove):
		if value is None:
			return None
		threshold = int(value)
		if threshold >= 0:
			if not sim:
				self._cmd.write_to_file(self._cache_threshold_path, threshold, \
					no_error = [errno.ENOENT] if remove else False)
			return threshold
		else:
			return None

	@command_get("avc_cache_threshold")
	def _get_avc_cache_threshold(self, instance):
		value = self._cmd.read_file(self._cache_threshold_path)
		if len(value) > 0:
			return int(value)
		return None
