#!/bin/sh

: << =cut

=head1 NAME

wireless_signal_ranges_ - Group and count all connected wifi peers by signal strength ranges


=head1 APPLICABLE SYSTEMS

Information is parsed from the output of the tool "iwinfo" (OpenWrt) or "iw" (most systems).

This plugin is suitable for wifi interfaces with a variable selection of peers (e.g. mobile
clients).


=head1 CONFIGURATION

Symlink this plugin with the name of the wifi interface added (e.g. "wlan0").

Root permissions are probably required for accessing "iw".

  [wireless_signal_ranges_*]
  user root


=head1 VERSION

  1.1


=head1 AUTHOR

Lars Kruse <devel@sumpfralle.de>


=head1 LICENSE

GPLv3 or above


=head1 MAGIC MARKERS

  #%# family=auto
  #%# capabilities=autoconf suggest

=cut

set -eu


SCRIPT_PREFIX="wireless_signal_ranges_"

# thresholds for signal quality ranges: ascending values
SIGNAL_THRESHOLDS="-88 -80 -60 0"


# prefer "iwinfo" for information retrieval, if it is available
if which iwinfo >/dev/null; then
	# "iwinfo" has a stable output format but is only available on openwrt
	get_wifi_interfaces() { iwinfo | grep "^[a-zA-Z]" | awk '{print $1}'; }
	# return MAC of peer and the signal strength
	get_wifi_peers() { iwinfo "$1" assoclist | grep "^[0-9a-fA-F]" | awk '{print $2}'; }
else
	# "iw" is available everywhere - but its output format is not recommended for non-humans
	get_wifi_interfaces() { iw dev | awk '{ if ($1 == "Interface") print $2; }'; }
	get_wifi_peers() { iw dev wlan0 station dump \
		| awk '{ if (($1 == "signal") && ($2 == "avg:")) print $3}'; }
fi


clean_fieldname() {
	echo "$1" | sed 's/^\([^A-Za-z_]\)/_\1/; s/[^A-Za-z0-9_]/_/g'
}


get_level_fieldname() {
	echo "range_${1#-}"
}


get_wifi_device_from_suffix() {
	local suffix
	local real_dev
	# pick the part after the basename of the real file
	suffix=$(basename "$0" | sed "s/^$SCRIPT_PREFIX//")
	for real_dev in $(get_wifi_interfaces); do
		[ "$suffix" != "$(clean_fieldname "$real_dev")" ] || echo "$real_dev"
	done | head -1
}


do_config() {
	local wifi
	local lower
	wifi=$(get_wifi_device_from_suffix)
	[ -z "$wifi" ] && echo >&2 "Missing wifi: $wifi" && return 1
	echo "graph_title Wireless signal quality ranges - $wifi"
	echo "graph_args --upper-limit 0"
	echo "graph_vlabel Signal ranges"
	echo "graph_category wireless"
	echo "graph_info This graph shows numbers of peers with defined wifi signal ranges"
	lower="noise"
	for level in $SIGNAL_THRESHOLDS; do
		fieldname=$(get_level_fieldname "$level")
		echo "${fieldname}.label $lower...$level"
		echo "${fieldname}.draw AREASTACK"
		lower="$level"
	done
}


do_fetch() {
	local wifi
	local peer_data
	local previous_count
	local current_count
	local fieldname
	wifi=$(get_wifi_device_from_suffix)
	[ -z "$wifi" ] && echo >&2 "Missing wifi: $wifi" && return 1
	peer_data=$(get_wifi_peers "$wifi")
	previous_count=0
	for level in $SIGNAL_THRESHOLDS; do
		current_count=$(echo "$peer_data" | awk '
			BEGIN { count=0; }
			{ if (($1 != "") && ($1 <= '"$level"')) count++; }
			END { print count; }')
		fieldname=$(get_level_fieldname "$level")
		echo "${fieldname}.value $((current_count - previous_count))"
		previous_count="$current_count"
	done
}


ACTION="${1:-}"

case "$ACTION" in
	config)
		do_config || exit 1
		if [ "${MUNIN_CAP_DIRTYCONFIG:-0}" = "1" ]; then do_fetch; fi
		;;
	autoconf)
		[ -z "$(get_wifi_interfaces)" ] && echo "no (no wifi interfaces found)" && exit 1
		echo "yes"
		;;
	suggest)
		get_wifi_interfaces | while read -r ifname; do
			clean_fieldname "$ifname"
		done
		;;
	"")
		do_fetch
		;;
	*)
		echo >&2 "Invalid action (valid: config / autoconf / suggest / <empty>)"
		echo >&2
		exit 2
		;;
esac