#!/bin/bash

if ! command -v slx-brightness &> /dev/null; then
	echo "Error: Required tool slx-brightness not in path"
	exit 1
fi

# How many steps we want from min to max
declare -rg steps=15

# Look for brightness config file
#
max_file="/sys/class/backlight/intel_backlight/max_brightness"
cur_file="/sys/class/backlight/intel_backlight/brightness"

if ! [ -e "$max_file" ] || ! [ -e "$cur_file" ]; then
	for max_file in /sys/class/backlight/*/max_brightness; do
		cur_file="${max_file%/*}/brightness"
		[ -e "$max_file" ] && [ -e "$cur_file" ] && break
	done
fi

if ! [ -e "$max_file" ] || ! [ -e "$cur_file" ]; then
	echo "No brightness controls found, exiting"
	exit 0
fi

# Calc sane limits
#
max=$( cat "$max_file" )
if ! (( max > 0 )); then
	echo "Max brightness is '$max', doing nothing"
	exit 0
fi

min=$(( max / ( steps + 1 ) ))

# Start our daemon
#
slx-brightness "$cur_file" "$min" "$max" "$steps" &
pid=$!

# Give it time to start
sleep 3

if ! kill -0 "$pid"; then
	# slx-brightness exits if it doesn't find a known input device for brightness control
	echo "slx-brightness didn't find a suitable device :-("
	t="$( mktemp )"
	if [ -n "$t" ]; then
		slx-brightness -l &> "$t"
		slxlog --delete --sync "screen-brightness" \
			"Device seems to have controllable backlight, but cannot find suitable input device" "$t"
	fi
	exit 0
fi

# Disable handling of keys by xfce-power-manager
#
pmfile="/etc/xdg/xfce4/xfconf/xfce-perchannel-xml/xfce4-power-manager.xml"
if ! [ -s "$pmfile" ]; then
	mkdir -p "${pmfile%/*}"
	cat > "$pmfile" <<-EOF
		<?xml version="1.0" encoding="UTF-8"?>

		<channel name="xfce4-power-manager" version="1.0" locked="*" unlocked="root">
			<property name="xfce4-power-manager" type="empty">
				<property name="handle-brightness-keys" type="bool" value="false"/>
			</property>
		</channel>
EOF
else
	xmlstarlet ed -u '/channel/property/property[@name="handle-brightness-keys"]/@value' \
			-v "false" "$pmfile" > "$pmfile.tmp" \
		&& mv -f "$pmfile.tmp" "$pmfile"
fi

exit 0