#!/bin/bash
off_time=3
polling_time=.1
startup_time=20:00
end_time=08:00

on_value=10
off_value=0

# check for root user
if [[ $EUID -ne 0 ]]; then
  echo "This script must be run as root"
  exit 1
fi

# INIT VARIABLES

counter=1
light_status=off
# how many counter to wait for the correct(ish) off_time
off_time_counter=$(bc <<< "scale=0; (1 / $polling_time) * $off_time")
keyboard="/dev/input/event0"
# getting the backlight class (hopefully)
backlight=`find /sys/class | grep kbd_backlight`
backlight="${backlight}/brightness"

if [ ! -f "$backlight" ]; then
    echo "Sorry I couln't find a backlight switch"
    exit 1
fi


while true; do

    current_time=$(date +%H:%M)

    if [[ "$current_time" > "$startup_time" ]] || [[ "$current_time" < "$end_time" ]]; then
        # get input from keyboard
	POLL=`timeout $polling_time cat $keyboard | tr -d '\0'`
        # keyboard is active, switch lights on
        if [ "$POLL" != "" ]; then
            counter=1
            if [ "$light_status" == "off" ]; then
                echo $on_value > $backlight
                light_status="on"
            fi

        # keyboard is inactive... if it stays so for off_time, switch lights off
        else
            if [ "$counter" -lt "$off_time_counter" ]; then
                counter=$((counter + 1))
            elif [ "$counter" -eq "$off_time_counter" ]; then
                echo $off_value > $backlight
                light_status="off"
            fi
        fi
    else
        # outside active hours, wait a minute and check again
        sleep 60
    fi
done