#!/bin/sh

# Parse arguments
# ------------------------------------------------------------------------------------
BRIGHTNESS_DIR="/sys/class/backlight/*"
SEND_NOTIFICATION=0
URGENCY="normal"
INCREASE=0
DECREASE=0
SET=0
BRIGHTNESS=0

PARSED=$(getopt \
	--options=hnu:i:d:s:p:N \
	--longoptions=help,notification,urgency:,increase:,decrease:,set:,path:,no-notification \
	--name "$0" \
	-- \
	"$@")

if [ $? != 0 ]; then
	exit 2
fi

eval set -- "$PARSED"

while [ "$1" ]; do
	case "$1" in
	-h | --help)
		cat <<EOF
brightness is a cli tool that for displaying or modifying screen brightness.

Options:
-h | --help: Display this message
-n | --notification: Produce a desktop notification with brightness info
-N | --no-notification: Don't produce a desktop notification with brightness info
-u | --urgency [URGENCY]: Pass over notify-send urgency attribute (default: normal)
-i | --increase [BRIGHTNESS]: Increase the brightness by given amount
-d | --decrease [BRIGHTNESS]: Decrease the brightness by given amount
-s | --set [BRIGHTNESS]: Set new brightness level
-p | --path [DIR_PATH]: Path to brightness directory (default: /sys/class/backlight/*)

Valid values:
    URGENCY: low, normal, critical
    DIR_PATH: Valid path to a directory
    BRIGHTNESS:
        specific value - Example: 10
        percentage value - Example: 10%
EOF
		exit 0
		;;
	-n | --notification)
		SEND_NOTIFICATION=1
		;;
	-N | --no-notification)
		SEND_NOTIFICATION=0
		;;
	-u | --urgency)
		URGENCY="$2"
		shift
		;;
	-i | --increase)
		INCREASE=1
		BRIGHTNESS="$2"
		shift
		;;
	-d | --decrease)
		DECREASE=1
		BRIGHTNESS="$2"
		shift
		;;
	-s | --set)
		SET=1
		BRIGHTNESS="$2"
		shift
		;;
	-p | --path)
		BRIGHTNESS_DIR="$2"
		shift
		;;
	--)
		shift
		break
		;;
	*)
		echo "Unknown argument '$1', use -h or --help for help"
		exit 1
		;;
	esac
	shift
done

# Define constants based on parsed arguments
# ------------------------------------------------------------------------------------
BRIGHTNESS_FILE="$BRIGHTNESS_DIR/brightness"
BRIGHTNESS_MAX="$(cat $BRIGHTNESS_DIR/max_brightness)"

# Helper functins
# ------------------------------------------------------------------------------------

# Send brightness level desktop notification, showing the given brightness level
# as progress bar, along with given message.
# $1 - brightness level (number 0-100)
# $2 - message (notification body)
send_brightness_notify() {
	percent_brightness="$1"
	msg="$2"

	notify-send \
		--app-name=brightness \
		--urgency="$URGENCY" \
		-h int:value:$percent_brightness \
		-h string:synchronous:brightness \
		"brightness" "$msg"
}

# Set brightness to given absolute value
# $1 - brightness absolute value
set_brightness() {
	# there should be sudo config allowing this command without password
	echo "$1" | sudo tee $BRIGHTNESS_FILE >/dev/null
}

# Main Logic
# ------------------------------------------------------------------------------------

# Determine the absolute new brightness level
if [ $INCREASE -eq 1 ] || [ $DECREASE -eq 1 ] || [ $SET -eq 1 ]; then
	# If we're dealing with percentages, change to absolutes
	if echo "$BRIGHTNESS" | grep -qE '%$'; then
		numeric=$(echo "$BRIGHTNESS" | sed 's/.$//')
		absolute=$(echo "($BRIGHTNESS_MAX / 100) * $numeric" | bc -l)
		BRIGHTNESS=$(printf "%.0f" $absolute)
	fi

	# Get the new requested absolute brightness
	if [ $SET -eq 1 ]; then
		new_brightness=$BRIGHTNESS
	elif [ $DECREASE -eq 1 ]; then
		cur_brightness=$(cat $BRIGHTNESS_FILE)
		new_brightness=$(($cur_brightness - $BRIGHTNESS))
	else
		cur_brightness=$(cat $BRIGHTNESS_FILE)
		new_brightness=$(($cur_brightness + $BRIGHTNESS))
	fi

	# Ensure we respect max/min boundaries
	if [ $new_brightness -lt 0 ]; then
		new_brightness=0
	elif [ $new_brightness -gt $BRIGHTNESS_MAX ]; then
		new_brightness=$BRIGHTNESS_MAX
	fi

	# Update the brightness
	set_brightness $new_brightness
fi

cur_brightness=$(cat $BRIGHTNESS_FILE)
percent_brightness=$(echo "($cur_brightness / $BRIGHTNESS_MAX) * 100" | bc -l)
percent_brightness_2f=$(printf "%.2f" $percent_brightness)
percent_brightness_rounded=$(printf "%.0f" $percent_brightness)

if [ $SEND_NOTIFICATION -eq 1 ]; then
	send_brightness_notify "$percent_brightness_rounded" "Level: $percent_brightness_rounded"
fi

echo "Brightness: ${percent_brightness_2f}% (absolute: $cur_brightness)"