#!/bin/bash

BRIGHTNESS_INCREMENT=.1
R_INCREMENT=0
G_INCREMENT=.1
B_INCREMENT=.2

xrandr_settings_of_display () {
	if [ "$#" -ne 1 ] ; then
		echo "Usage : xrandr_settings_of_display <display_name>" >&2
		exit 1
	fi

	out="$(xrandr --verbose | sed -e "1,/^$1/d" | sed '/^ /,$d')"

	if [ -z "$out" ] ; then
		echo "ERROR, empty output for command: xrandr_settings_of_display $@" >&2
		exit 1
	fi

	echo "$out"
}


brigthness_of_display () {
	if [ "$#" -ne 1 ] ; then
		echo "Usage : brigthness_of_display <display_name>" >&2
		exit 1
	fi

	xrandr_settings_of_display "$1" | grep -Po 'Brightness: \K.*'
}


raw_gamma_of_display () {
	if [ "$#" -ne 1 ] ; then
		echo "Usage : raw_gamma_of_display <display_name>" >&2
		exit 1
	fi

	xrandr_settings_of_display "$1" | grep -Po 'Gamma: \K.*' | tr ':' ' '
}

gamma_of_display () {
	if [ "$#" -ne 1 ] ; then
		echo "Usage : gamma_of_display <display_name>" >&2
		exit 1
	fi

	read r g b <<< "$(raw_gamma_of_display "$1")"
	echo "$r $g $b -> $(invert $r) $(invert $g) $(invert $b)" >&2
	echo "$(invert $r) $(invert $g) $(invert $b)"
}

invert () {
	if [ "$#" -ne 1 ] ; then
		echo "Usage : invert <float_number>" >&2
		exit 1
	fi

	echo "1/$1" | bc -l | grep -o '.*\...'
}


############### Args

if [ "$#" -ne 2 ] ; then
	echo "Usage : $0 <brightness|redness> +|-|=" >&2
	exit 1
fi

property="$1"
action="$2"

if [ ! "$action" = - ] && [ ! "$action" = + ] && [ ! "$action" = '=' ] ; then
	echo "Bad action '$action'. Expected + - or =."
	exit 1
fi


i=0
xrandr --listactivemonitors | tail -n +2 | cut -d ' ' -f 6  | while read monitor ; do
	args=''
	if [ "$i" -eq 0 ] ; then
		((i=i+1))
		case "$property" in
			brightness)
				if [ "$action" = '=' ] ; then
					args="--brightness 1"
				else
					b="$(brigthness_of_display "$monitor")"
					b="$( echo "$b $action $BRIGHTNESS_INCREMENT" | bc -l )"
					args="--brightness $b"
				fi
				;;
			redness)
				if [ "$action" = '=' ] ; then
					args="--gamma 1:1:1"
				else
					read r g b <<< "$(gamma_of_display "$monitor")"

					rnew="$( echo "$r $action $R_INCREMENT" | bc -l )"
					gnew="$( echo "$g $action $G_INCREMENT" | bc -l )"
					bnew="$( echo "$b $action $B_INCREMENT" | bc -l )"
					args="--gamma $rnew:$gnew:$bnew"
					#echo "from $r:$g:$b to $rnew:$gnew:$bnew"
				fi
				;;
			*)
				echo "Invalid property $property"
				exit 1
		esac
	else
		args="--same-as $monitor"
	fi
	xrandr --output "$monitor" $args
	echo xrandr --output "$monitor" $args
done