#!/bin/sh

# Uncomment the following line to get debug info
#set -x

SELF="$(basename ${0})"
SYSTEM_BRIGHTNESS="/sys/class/backlight/backlight/brightness"
DEFAULT_BRIGHTNESS_VALUE=100
BRIGHTNESS_STEP=10
NOTIF_DURATION=2

usage() {
    >&2 echo "Usage: ${SELF} get"
    >&2 echo "       ${SELF} set  new_brightness_percentage"
    exit 1
}

increase_brightness() {

    # Get current value
    local current_brightness=$(get_brightness)

    # Compute new brightness value
    local new_brightness=0
    let new_brightness=${current_brightness}+${BRIGHTNESS_STEP}
    if [ ${new_brightness} -gt 100 ]; then
	new_brightness=100
    fi

    # Change brightness
    if [ ${new_brightness} -ne ${current_brightness} ]; then
	set_brightness ${new_brightness}
    fi

    # Notif
    notif set ${NOTIF_DURATION} "       BRIGHTNESS: ${new_brightness}%%"
}

decrease_brightness() {

    # Get current value
    local current_brightness=$(get_brightness)

    # Compute new brightness value
    local new_brightness=0
    if [ ${current_brightness} -gt ${BRIGHTNESS_STEP} ]; then
	let new_brightness=${current_brightness}-${BRIGHTNESS_STEP}
    fi

    # Change brightness
    if [ ${new_brightness} -ne ${current_brightness} ]; then
	set_brightness ${new_brightness}
    fi

    # Notif
    notif set ${NOTIF_DURATION} "       BRIGHTNESS: ${new_brightness}%%"
}

get_brightness() {
    local brightness=$(fw_printenv -n brightness 2>/dev/null)
    if ! [ ! "${brightness}" -ne "${brightness}" ] 2> /dev/null; then
	brightness=${DEFAULT_BRIGHTNESS_VALUE}
	fw_setenv brightness ${brightness}
    fi
    echo ${brightness}
}

set_brightness() {

    # Set the new brightness percentage in the kernel driver
    local brightness=${1}
    local kernel_brightness
    let kernel_brightness=${brightness}+10
    let kernel_brightness/=10
    echo ${kernel_brightness} > "${SYSTEM_BRIGHTNESS}"

    # Set the new brightness value in a bootloader variable
    if [ ${?} -eq 0 -a $(get_brightness) -ne ${brightness} ]; then
	fw_setenv brightness ${brightness}
    fi
}

# Check number of arguments
if [ ${#} -lt 1 -o ${#} -gt 2 ]; then
    usage
fi

case "${1}" in
    up)
	if [ ${#} -ne 1 ]; then
	    usage
	fi
	increase_brightness
	;;

    down)
	if [ ${#} -ne 1 ]; then
	    usage
	fi
	decrease_brightness
	;;

    get)
	if [ ${#} -ne 1 ]; then
	    usage
	fi
	get_brightness
    ;;

    set)
	if [ ${#} -ne 2 ]; then
	    usage
	fi

	# Make sure the argument is a positive number <= 100
	if [ -n "${2}" ] && [ "${2}" -eq "${2}" ] 2>/dev/null && \
	       [ "${2}" -ge 0 ] && [ "${2}" -le 100 ]; then
	    set_brightness "${2}"
	else
	    usage
	fi
    ;;

    *)
	usage
	;;
esac
exit 0