#!/bin/sh

: << =cut

=head1 NAME

wireless_channel_active - Show currently used channel of wifi enabled devices

=head1 APPLICABLE SYSTEMS

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


=head1 CONFIGURATION

Symlink this plugin with the name of the wifi device added (e.g. "phy0").

Root permissions are probably required for accessing "iw".

  [wireless_channel_active*]
  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

if which iwinfo >/dev/null; then
	# "iwinfo" has a stable output format but is only available on OpenWrt
	get_physical_interfaces() { iwinfo | sed -n 's/^.*PHY name: \+\(.*\)$/\1/p'; }
	get_physical_interface_current_channel() { iwinfo "$1" info \
		| grep Channel | sed 's/^.*Channel: \+\([0-9]\+\) .*$/\1/'; }
	get_physical_interfaces_channel_descriptions() {
		# return: CHANNEL CHANNEL_DESCRIPTION
		# e.g.: "104 5.520 GHz (Channel 104)"
		iwinfo "$1" freqlist | sed 's/^[^0-9]*//' \
			| sed 's/^.*Channel \+\([0-9]\+\).*$/\1 \0/'; }
else
	# "iw" is available everywhere - but its output format is not recommended for non-humans
	get_physical_interfaces() { iw list | awk '/^\w/ {print $2}'; }
	get_physical_interface_current_channel() { iw dev | awk '
		/^\w+#/ { phy_name=gensub("#", "", 1, $1); }
		/channel/ { if (phy_name == "phy0") print($2); }'; }
	get_physical_interfaces_channel_descriptions() {
		# example input: "* 5680 MHz [136]"
		# return: CHANNEL CHANNEL_DESCRIPTION
		# e.g.: "136 5680 MHz [136]"
		iw phy phy0 channels | awk '
			/\*/ { chan_num=gensub("^.*\\[", "", 1, gensub("\\].*$", "", 1, $0));
				print(chan_num, $2, $3, $4); }'; }
fi


get_selected_physical_interface() {
	# The physical interface name should be safe (phyX) and needs no cleanup.
	# pick the last segment after the final "_"
	echo "$0" | sed 's/.*_//'
}


do_config() {
	local phy
	phy=$(get_selected_physical_interface)
	[ -z "$phy" ] && echo >&2 "Missing wireless PHY" && return 1
	echo "graph_title Wireless channel usage - $phy"
	echo "graph_args --base 1000 -r --lower-limit 0 --upper-limit 100"
	echo "graph_vlabel Channel usage by time in percent"
	echo "graph_category wireless"
	echo "graph_info This graph shows the currently used channel of your WiFi device(s)"
	get_physical_interfaces_channel_descriptions "$phy" | while read -r channel description; do
		fieldname="channel_${channel}"
		echo "${fieldname}.label $description"
		echo "${fieldname}.draw AREASTACK"
		# percent scaling
		echo "${fieldname}.cdef 100,${fieldname},*"
	done
}


do_fetch() {
	local phy
	local current_channel
	phy=$(get_selected_physical_interface)
	[ -z "$phy" ] && echo >&2 "Missing wireless PHY" && return 1
	current_channel=$(get_physical_interface_current_channel "$phy")
	get_physical_interfaces_channel_descriptions "$phy" | while read -r channel description; do
		[ "$current_channel" = "$channel" ] && value=1 || value=0
		echo "channel_${channel}.value $value"
	done
}


ACTION="${1:-}"

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