#! /bin/sh

OS=$(uname)

# MIT License
#
# Copyright (c) 2016 Josef Friedrich <josef@friedrich.rocks>
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
# IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
# CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
# TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

########################################################################
# Date functions
########################################################################

# This date function must be placed on the top of this file because
# they are used in some global variables.

# to_year ###

##
# Get the four digit year integer from now.
#
# Return:
#   The current 4 digit year.
##
_now_to_year() {
	date +%Y
}

##
# Convert a date in the format YYYY-MM-DD to a four digit year integer.
#
# Parameters:
#   a date in the format YYYY-MM-DD
#
# Return:
#   four digit year integer
##
_date_to_year() {
	local OPTIONS
	if [ "$OS" = 'Linux' ]; then
		OPTIONS="--date $1"
	# FreeBSD, Darwin
	else
		OPTIONS="-j -f %Y-%m-%d $1"
	fi
	date $OPTIONS +%Y
}

# to_datetime ###

##
# Convert a UNIX timestamp to a datetime string.
#
# Parameters:
#   UNIX timestamp
#
# Return:
#   %Y-%m-%d.%H:%M:%S
##
_timestamp_to_datetime() {
	local OPTIONS
	if [ "$OS" = 'Linux' ]; then
		OPTIONS="--date @$1"
	# FreeBSD, Darwin
	else
		OPTIONS="-j -f %s $1"
	fi
	date $OPTIONS +%Y-%m-%d.%H:%M:%S
}

# to_timestamp ###

##
# Get the current UNIX timestamp.
#
# Return:
#   %current UNIX timestamp
##
_now_to_timestamp() {
	date +%s
}

PROJECT_PAGES='https://github.com/Josef-Friedrich/check_zfs_snapshot
https://exchange.icinga.com/joseffriedrich/check_zfs_snapshot
https://exchange.nagios.org/directory/Plugins/System-Metrics/File-System/check_zfs_snapshot/details'

VERSION=1.2
FIRST_RELEASE=2016-09-08
SHORT_DESCRIPTION="Monitoring plugin to check how long ago the last \
snapshot of a ZFS dataset was created."
USAGE="check_zfs_snapshot v$VERSION
Copyright (c) $(_date_to_year $FIRST_RELEASE)-$(_now_to_year) \
Josef Friedrich <josef@friedrich.rocks>

$SHORT_DESCRIPTION


Usage: check_zfs_snapshot <options>

Options:
 -c, --critical=OPT_CRITICAL
    Interval in seconds for critical state.
 -d, --dataset=OPT_DATASET
    The ZFS dataset to check.
 -h, --help
    Show this help.
 -s, --short-description
    Show a short description of the command.
 -v, --version
    Show the version number.
 -w, --warning=OPT_WARNING
    Interval in seconds for warning state. Must be lower than -c

Performance data:
 - last_ago
    Time interval in seconds for last snapshot.
 - warning
    Interval in seconds.
 - critical
    Interval in seconds.
 - snapshot_count
    How many snapshot exists in the given dataset and all child
    datasets exists.
"

# Exit codes
STATE_OK=0
STATE_WARNING=1
STATE_CRITICAL=2
STATE_UNKNOWN=3

_get_last_snapshot() {
	zfs get creation -Hpr -t snapshot "$1" | \
		awk 'BEGIN {max = 0} {if ($3>max) max=$3} END {print max}'
}

_getopts() {
	while getopts ':c:d:hsvw:-:' OPT ; do
		case $OPT in

			c)
				OPT_CRITICAL=$OPTARG
				;;

			d)
				OPT_DATASET="$OPTARG"
				;;

			h)
				echo "$USAGE"
				exit 0
				;;

			s)
				echo "$SHORT_DESCRIPTION"
				exit 0
				;;

			v)
				echo "$VERSION"
				exit 0
				;;

			w)
				OPT_WARNING=$OPTARG
				;;

			\?)
				echo "Invalid option “-$OPTARG”!" >&2
				exit 2
				;;

			:)
				echo "Option “-$OPTARG” requires an argument!" >&2
				exit 3
				;;

			-)
				LONG_OPTARG="${OPTARG#*=}"

				case $OPTARG in

					critical=?*)
						OPT_CRITICAL=$LONG_OPTARG
						;;

					dataset=?*)
						OPT_DATASET="$LONG_OPTARG"
						;;

					help)
						echo "$USAGE"
						exit 0
						;;

					short-description)
						echo "$SHORT_DESCRIPTION"
						exit 0
						;;

					version)
						echo "$VERSION"
						exit 0
						;;

					warning=?*)
						OPT_WARNING=$LONG_OPTARG
						;;

					critical*|dataset*|warning*)
						echo "Option “--$OPTARG” requires an argument!" >&2
						exit 3
						;;

					help*|short-description*|version*)
						echo "No argument allowed for the option “--$OPTARG”!" >&2
						exit 4
						;;

					'')	# "--" terminates argument processing
						break
						;;

					*)
						echo "Invalid option “--$OPTARG”!" >&2
						exit 2
						;;

				esac
				;;

		esac
	done
}

_snapshot_count() {
	# FreeBSD wc adds some whitespaces before the number!
	# cat $HOME/debug | wc -l
	#        7
	local COUNT
	COUNT="$(zfs list -t snapshot | grep "$1" | wc -l)"
	echo $COUNT
}

_performance_data() {
	echo "| \
last_ago=$DIFF \
warning=$OPT_WARNING \
critical=$OPT_CRITICAL \
snapshot_count=$(_snapshot_count "$OPT_DATASET")\
"
}

## This SEPARATOR is required for test purposes. Please don’t remove! ##

_getopts $@

if [ -z "$OPT_WARNING" ]; then
	# 1 day
	OPT_WARNING=86400
fi

if [ -z "$OPT_CRITICAL" ]; then
	# 3 day
	OPT_CRITICAL=259200
fi

if [ -z "$OPT_DATASET" ]; then
	echo "Dataset has to be set! Use option -d <dataset>" >&2
	echo "$USAGE" >&2
	exit $STATE_UNKNOWN
fi

if ! zfs list "$OPT_DATASET" > /dev/null 2>&1; then
	echo "'$OPT_DATASET' is no ZFS dataset!" >&2
	echo "$USAGE" >&2
	exit $STATE_UNKNOWN
fi

NOW=$(_now_to_timestamp)

CREATION_DATE=$(_get_last_snapshot "$OPT_DATASET")

DIFF=$((NOW - CREATION_DATE))

if [ "$OPT_WARNING" -gt "$OPT_CRITICAL" ]; then
	echo '-w OPT_WARNING must be smaller than -c OPT_CRITICAL'
	_usage >&2
	exit $STATE_UNKNOWN
fi

RETURN=STATE_UNKNOWN

if [ "$DIFF" -gt "$OPT_CRITICAL" ]; then
	RETURN=$STATE_CRITICAL
	MESSAGE="CRITICAL:"
elif [ "$DIFF" -gt "$OPT_WARNING" ]; then
	RETURN=$STATE_WARNING
	MESSAGE="WARNING:"
else
	RETURN=$STATE_OK
	MESSAGE="OK:"
fi

DATE="$(_timestamp_to_datetime "$CREATION_DATE")"

echo "$MESSAGE Last snapshot for dataset '$OPT_DATASET' was created on $DATE $(_performance_data)"

exit $RETURN