# emacs: -*- mode: python; py-indent-offset: 4; indent-tabs-mode: t -*-
# vi: set ft=python sts=4 ts=4 sw=4 noet :

# This file is part of Fail2Ban.
#
# Fail2Ban is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# Fail2Ban is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Fail2Ban; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.


__author__ = "Steven Hiscocks"
__copyright__ = "Copyright (c) 2013 Steven Hiscocks"
__license__ = "GPL"

import os
import time

from systemd import journal

from .failmanager import FailManagerEmpty
from .filter import JournalFilter, Filter
from .mytime import MyTime
from .utils import Utils
from ..helpers import getLogger, logging, splitwords, uni_decode

# Gets the instance of the logger.
logSys = getLogger(__name__)


##
# Journal reader class.
#
# This class reads from systemd journal and detects login failures or anything
# else that matches a given regular expression. This class is instantiated by
# a Jail object.

class FilterSystemd(JournalFilter): # pragma: systemd no cover
	##
	# Constructor.
	#
	# Initialize the filter object with default values.
	# @param jail the jail object

	def __init__(self, jail, **kwargs):
		jrnlargs = FilterSystemd._getJournalArgs(kwargs)
		JournalFilter.__init__(self, jail, **kwargs)
		self.__modified = 0
		# Initialise systemd-journal connection
		self.__journal = journal.Reader(**jrnlargs)
		self.__matches = []
		self.setDatePattern(None)
		logSys.debug("Created FilterSystemd")

	@staticmethod
	def _getJournalArgs(kwargs):
		args = {'converters':{'__CURSOR': lambda x: x}}
		try:
			args['path'] = kwargs.pop('journalpath')
		except KeyError:
			pass

		try:
			args['files'] = kwargs.pop('journalfiles')
		except KeyError:
			pass
		else:
			import glob
			p = args['files']
			if not isinstance(p, (list, set, tuple)):
				p = splitwords(p)
			files = []
			for p in p:
				files.extend(glob.glob(p))
			args['files'] = list(set(files))

		# Default flags is SYSTEM_ONLY(4). This would lead to ignore user session files,
		# so can prevent "Too many open files" errors on a lot of user sessions (see gh-2392):
		try:
			args['flags'] = int(kwargs.pop('journalflags'))
		except KeyError:
			# be sure all journal types will be opened if files/path specified (don't set flags):
			if ('files' not in args or not len(args['files'])) and ('path' not in args or not args['path']):
				args['flags'] = int(os.getenv("F2B_SYSTEMD_DEFAULT_FLAGS", 4))
				
		try:
			args['namespace'] = kwargs.pop('namespace')
		except KeyError:
			pass

		return args

	##
	# Add a journal match filters from list structure
	#
	# @param matches list structure with journal matches

	def _addJournalMatches(self, matches):
		if self.__matches:
			self.__journal.add_disjunction() # Add OR
		newMatches = []
		for match in matches:
			newMatches.append([])
			for match_element in match:
				self.__journal.add_match(match_element)
				newMatches[-1].append(match_element)
			self.__journal.add_disjunction()
		self.__matches.extend(newMatches)

	##
	# Add a journal match filter
	#
	# @param match journalctl syntax matches in list structure

	def addJournalMatch(self, match):
		newMatches = [[]]
		for match_element in match:
			if match_element == "+":
				newMatches.append([])
			else:
				newMatches[-1].append(match_element)
		try:
			self._addJournalMatches(newMatches)
		except ValueError:
			logSys.error(
				"Error adding journal match for: %r", " ".join(match))
			self.resetJournalMatches()
			raise
		else:
			logSys.info("[%s] Added journal match for: %r", self.jailName, 
				" ".join(match))
	##
	# Reset a journal match filter called on removal or failure
	#
	# @return None 

	def resetJournalMatches(self):
		self.__journal.flush_matches()
		logSys.debug("[%s] Flushed all journal matches", self.jailName)
		match_copy = self.__matches[:]
		self.__matches = []
		try:
			self._addJournalMatches(match_copy)
		except ValueError:
			logSys.error("Error restoring journal matches")
			raise
		else:
			logSys.debug("Journal matches restored")

	##
	# Delete a journal match filter
	#
	# @param match journalctl syntax matches

	def delJournalMatch(self, match=None):
		# clear all:
		if match is None:
			if not self.__matches:
				return
			del self.__matches[:]
		# delete by index:
		elif match in self.__matches:
			del self.__matches[self.__matches.index(match)]
		else:
			raise ValueError("Match %r not found" % match)
		self.resetJournalMatches()
		logSys.info("[%s] Removed journal match for: %r", self.jailName, 
			match if match else '*')

	##
	# Get current journal match filter
	#
	# @return journalctl syntax matches

	def getJournalMatch(self):
		return self.__matches

	##
	# Get journal reader
	#
	# @return journal reader

	def getJournalReader(self):
		return self.__journal

	def getJrnEntTime(self, logentry):
		""" Returns time of entry as tuple (ISO-str, Posix)."""
		date = logentry.get('_SOURCE_REALTIME_TIMESTAMP')
		if date is None:
				date = logentry.get('__REALTIME_TIMESTAMP')
		return (date.isoformat(), time.mktime(date.timetuple()) + date.microsecond/1.0E6)

	##
	# Format journal log entry into syslog style
	#
	# @param entry systemd journal entry dict
	# @return format log line

	def formatJournalEntry(self, logentry):
		# Be sure, all argument of line tuple should have the same type:
		enc = self.getLogEncoding()
		logelements = []
		v = logentry.get('_HOSTNAME')
		if v:
			logelements.append(uni_decode(v, enc))
		v = logentry.get('SYSLOG_IDENTIFIER')
		if not v:
			v = logentry.get('_COMM')
		if v:
			logelements.append(uni_decode(v, enc))
			v = logentry.get('SYSLOG_PID')
			if not v:
				v = logentry.get('_PID')
			if v:
				try: # [integer] (if already numeric):
					v = "[%i]" % v
				except TypeError:
					try: # as [integer] (try to convert to int):
						v = "[%i]" % int(v, 0)
					except (TypeError, ValueError): # fallback - [string] as it is
						v = "[%s]" % v
				logelements[-1] += v
			logelements[-1] += ":"
			if logelements[-1] == "kernel:":
				monotonic = logentry.get('_SOURCE_MONOTONIC_TIMESTAMP')
				if monotonic is None:
					monotonic = logentry.get('__MONOTONIC_TIMESTAMP')[0]
				logelements.append("[%12.6f]" % monotonic.total_seconds())
		msg = logentry.get('MESSAGE','')
		if isinstance(msg, list):
			logelements.append(" ".join(uni_decode(v, enc) for v in msg))
		else:
			logelements.append(uni_decode(msg, enc))

		logline = " ".join(logelements)

		date = self.getJrnEntTime(logentry)
		logSys.log(5, "[%s] Read systemd journal entry: %s %s", self.jailName,
			date[0], logline)
		## use the same type for 1st argument:
		return ((logline[:0], date[0] + ' ', logline.replace('\n', '\\n')), date[1])

	def seekToTime(self, date):
		if isinstance(date, int):
			date = float(date)
		self.__journal.seek_realtime(date)

	def inOperationMode(self):
		self.inOperation = True
		logSys.info("[%s] Jail is in operation now (process new journal entries)", self.jailName)

	##
	# Main loop.
	#
	# Peridocily check for new journal entries matching the filter and
	# handover to FailManager

	def run(self):

		if not self.getJournalMatch():
			logSys.notice(
				"[%s] Jail started without 'journalmatch' set. "
				"Jail regexs will be checked against all journal entries, "
				"which is not advised for performance reasons.", self.jailName)

		# Save current cursor position (to recognize in operation mode):
		logentry = None
		try:
			self.__journal.seek_tail()
			logentry = self.__journal.get_previous()
			if logentry:
				self.__journal.get_next()
		except OSError:
			logentry = None # Reading failure, so safe to ignore
		if logentry:
			# Try to obtain the last known time (position of journal)
			startTime = 0
			if self.jail.database is not None:
				startTime = self.jail.database.getJournalPos(self.jail, 'systemd-journal') or 0
			# Seek to max(last_known_time, now - findtime) in journal
			startTime = max( startTime, MyTime.time() - int(self.getFindTime()) )
			self.seekToTime(startTime)
			# Not in operation while we'll read old messages ...
			self.inOperation = False
			# Save current time in order to check time to switch "in operation" mode
			startTime = (1, MyTime.time(), logentry.get('__CURSOR'))
		else:
			# empty journal or no entries for current filter:
			self.inOperationMode()
			# seek_tail() seems to have a bug by no entries (could bypass some entries hereafter), so seek to now instead:
			startTime = MyTime.time()
			self.seekToTime(startTime)
			# for possible future switches of in-operation mode:
			startTime = (0, startTime)

		# Move back one entry to ensure do not end up in dead space
		# if start time beyond end of journal
		try:
			self.__journal.get_previous()
		except OSError:
			pass # Reading failure, so safe to ignore

		wcode = journal.NOP
		line = None
		while self.active:
			# wait for records (or for timeout in sleeptime seconds):
			try:
				## wait for entries using journal.wait:
				if wcode == journal.NOP and self.inOperation:
					## todo: find better method as wait_for to break (e.g. notify) journal.wait(self.sleeptime),
					## don't use `journal.close()` for it, because in some python/systemd implementation it may 
					## cause abnormal program termination (e. g. segfault)
					## 
					## wait for entries without sleep in intervals, because "sleeping" in journal.wait,
					## journal.NOP is 0, so we can wait for non zero (APPEND or INVALIDATE):
					wcode = Utils.wait_for(lambda: not self.active and journal.APPEND or \
						self.__journal.wait(Utils.DEFAULT_SLEEP_INTERVAL),
						self.sleeptime, 0.00001)
					## if invalidate (due to rotation, vacuuming or journal files added/removed etc):
					if self.active and wcode == journal.INVALIDATE:
						if self.ticks:
							logSys.log(logging.DEBUG, "[%s] Invalidate signaled, take a little break (rotation ends)", self.jailName)
							time.sleep(self.sleeptime * 0.25)
						Utils.wait_for(lambda: not self.active or \
							self.__journal.wait(Utils.DEFAULT_SLEEP_INTERVAL) != journal.INVALIDATE,
							self.sleeptime * 3, 0.00001)
						if self.ticks:
							# move back and forth to ensure do not end up in dead space by rotation or vacuuming,
							# if position beyond end of journal (gh-3396)
							try:
								if self.__journal.get_previous(): self.__journal.get_next()
							except OSError:
								pass
				if self.idle:
					# because journal.wait will returns immediately if we have records in journal,
					# just wait a little bit here for not idle, to prevent hi-load:
					if not Utils.wait_for(lambda: not self.active or not self.idle, 
						self.sleeptime * 10, self.sleeptime
					):
						self.ticks += 1
						continue
				self.__modified = 0
				while self.active:
					logentry = None
					try:
						logentry = self.__journal.get_next()
					except OSError as e:
						logSys.error("Error reading line from systemd journal: %s",
							e, exc_info=logSys.getEffectiveLevel() <= logging.DEBUG)
					self.ticks += 1
					if logentry:
						line, tm = self.formatJournalEntry(logentry)
						# switch "in operation" mode if we'll find start entry (+ some delta):
						if not self.inOperation:
							if tm >= MyTime.time() - 1: # reached now (approximated):
								self.inOperationMode()
							elif startTime[0] == 1:
								# if it reached start entry (or get read time larger than start time)
								if logentry.get('__CURSOR') == startTime[2] or tm > startTime[1]:
									# give the filter same time it needed to reach the start entry:
									startTime = (0, MyTime.time()*2 - startTime[1])
							elif tm > startTime[1]: # reached start time (approximated):
								self.inOperationMode()
						# process line
						self.processLineAndAdd(line, tm)
						self.__modified += 1
						if self.__modified >= 100: # todo: should be configurable
							wcode = journal.APPEND; # don't need wait - there are still unprocessed entries
							break
					else:
						# "in operation" mode since we don't have messages anymore (reached end of journal):
						if not self.inOperation:
							self.inOperationMode()
						wcode = journal.NOP; # enter wait - no more entries to process
						break
				self.__modified = 0
				if self.ticks % 10 == 0:
					self.performSvc()
				# update position in log (time and iso string):
				if self.jail.database:
					if line:
						self._pendDBUpdates['systemd-journal'] = (tm, line[1])
						line = None
					if self._pendDBUpdates and (
				    self.ticks % 100 == 0
				    or MyTime.time() >= self._nextUpdateTM
				    or not self.active
				  ):
						self._updateDBPending()
						self._nextUpdateTM = MyTime.time() + Utils.DEFAULT_SLEEP_TIME * 5
			except Exception as e: # pragma: no cover
				if not self.active: # if not active - error by stop...
					break
				wcode = journal.NOP
				logSys.error("Caught unhandled exception in main cycle: %r", e,
					exc_info=logSys.getEffectiveLevel()<=logging.DEBUG)
				# incr common error counter:
				self.commonError("unhandled", e)

		logSys.debug("[%s] filter terminated", self.jailName)

		# close journal:
		self.closeJournal()

		logSys.debug("[%s] filter exited (systemd)", self.jailName)
		return True

	def closeJournal(self):
		try:
			jnl, self.__journal = self.__journal, None
			if jnl:
				jnl.close()
		except Exception as e: # pragma: no cover
			logSys.error("Close journal failed: %r", e,
				exc_info=logSys.getEffectiveLevel()<=logging.DEBUG)


	def status(self, flavor="basic"):
		ret = super(FilterSystemd, self).status(flavor=flavor)
		if flavor == "stats":
			return ret
		ret.append(("Journal matches",
			[" + ".join(" ".join(match) for match in self.__matches)]))
		return ret

	def _updateDBPending(self):
		"""Apply pending updates (journal position) to database.
		"""
		db = self.jail.database
		while True:
			try:
				log, args = self._pendDBUpdates.popitem()
			except KeyError:
				break
			db.updateJournal(self.jail, log, *args)

	def onStop(self):
		"""Stop monitoring of journal. Invoked after run method.
		"""
		# close journal:
		self.closeJournal()
		# ensure positions of pending logs are up-to-date:
		if self._pendDBUpdates and self.jail.database:
			self._updateDBPending()