moodlight (laptop display adjuster)

#!/bin/zsh
# author: milomouse
# NOTE: change brightness of certain laptop monitors,
#       storing values in plain text for adjustments.

output='sudo setpci -s 00:02.0 F4.B='
config=${XDG_CONFIG_DIR:-$HOME/.config}/.brightness
[[ -f $config ]] || print $output\FF > $config
current=${${$(<$config)[5]}[-2,-1]//=}
argument="5"

brightness_down() {
  if [ $current -le 5 &>/dev/null ]; then exit
  elif [ $current = FF ]; then NEW=95
  else NEW=$(($current - $argument)); fi
  print $output$NEW > $config && . $config
}

brightness_up() {
  if [ $current = FF ]; then exit
  elif [ $current -ge 95 &>/dev/null ]; then NEW=FF
  else NEW=$(($current + $argument)); fi
  print $output$NEW > $config && . $config
}

brightness_max() {
  NEW=FF
  print $output$NEW > $config && . $config
}

brightness_set() {
  NEW=$1
  if [ $NEW -lt 5 &>/dev/null ]; then NEW=5
  elif [ $NEW -ge 95 &>/dev/null ]; then NEW=FF
  elif [ $(($NEW % 5)) -gt 0 ]; then
    NEW=$(($(($NEW / 5)) * 5)); fi
  print $output$NEW > $config && . $config
}

reassert() { . $config }

help() {
<< EOF
usage: moodlight [OPTION]
OPTIONS:
   -i|--increase  Brighten the screen.
   -d|--decrease  Dim the screen.
   -m|--max       Set brightness to max.
   -s|--set n     Set brightness level to n.
   -r|--reassert  Execute last brightness level.
                  This is useful for startup.
   -h|--help      Show this help message.
EOF
}

case "$1" in
  '-i'|'--increase') brightness_up ;;
  '-d'|'--decrease') brightness_down ;;
  '-m'|'--max') brightness_max ;;
  '-s'|'--set') brightness_set ${${@:/$1}[1]} ;;
  '-r'|'--reassert') reassert ;;
  '-h'|'--help'|*) help ;;
esac