#!/bin/sh
#
# Show current signal strength and noise for all connected peers of wifi devices.
# This plugin is suitable for wifi interfaces with a stable selection of peers
# (e.g. infrastructure).
# Author: Lars Kruse, devel@sumpfralle.de
# License: GPL v3 or later
#
# Requirements:
#  * "iwinfo" tool (alternatively: fall back to "iw" - with incomplete data)
#  * root privileges (for "iw" and "iwinfo")
#
# Magic markers
#%# capabilities=autoconf suggest
#%# family=auto


set -eu


# 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 $1,$2}'; }
	# the noise should be the same for all peers
	get_wifi_noise() { iwinfo "$1" info | sed -n 's/^.* Noise: \([0-9-]\+\).*/\1/p'; }
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 == "Station") mac=$2; if (($1 == "signal") && ($2 == "avg:")) print mac,$3}'; }
	# TODO: there seems to be no way to retrieve the noise level via "iw"
	get_wifi_noise() { echo; }
fi


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


get_ip_for_mac() {
	local ip
	ip=$(arp -n | grep -iw "$1$" | awk '{print $1}' | sort | head -1)
	[ -n "$ip" ] && echo "$ip" && return 0
	# no IP found - return MAC instead
	echo "$1"
}


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


ACTION="${1:-}"

case "$ACTION" in
	config)
		wifi=$(get_wifi_device_from_suffix)
		echo "graph_title Wireless signal quality - $wifi"
		echo "graph_args --upper-limit 0"
		echo "graph_vlabel Signal and noise [dBm]"
		echo "graph_category network"
		echo "graph_info This graph shows the signal and noise for all wifi peers"
		echo "noise.label Noise floor"
		echo "noise.draw LINE"
		# sub graphs for all peers
		get_wifi_peers "$wifi" | while read mac signal; do
			fieldname=$(clean_fieldname "peer_${mac}")
			peer=$(get_ip_for_mac "$mac")
			echo "signal_${fieldname}.label $peer"
			echo "signal_${fieldname}.draw LINE"
		done
		;;
	autoconf)
		[ -z "$(get_wifi_interfaces)" ] && echo "no (no wifi interfaces found)" && exit 1
		echo "yes"
		;;
	suggest)
		get_wifi_interfaces | while read ifname; do
			clean_fieldname "$ifname"
		done
		;;
	"")
		wifi=$(get_wifi_device_from_suffix)
		peer_data=$(get_wifi_peers "$wifi")
		echo "$peer_data" | while read mac signal; do
			# ignore empty datasets
			[ -z "$signal" ] && continue
			fieldname=$(clean_fieldname "peer_${mac}")
			echo "signal_${fieldname}.value $signal"
		done
		echo "noise.value $(get_wifi_noise "$wifi")"
		;;
	*)
		echo >&2 "Invalid action (valid: config)"
		echo >&2
		;;
esac