#!/bin/bash

# Get the correct sub-directory for your backlight device
root_path="/sys/class/backlight/"
device="$(find "$root_path" | tail -n 1)"

max="$(cat "$device/max_brightness")"

# What percentage to increase/decrease by when no argument is given
default_step=10
# What percentage to set to when no argument is given
default_set=50

to_percent() {
  printf "%d" "$((100 * $1 / $max))"
}

to_value() {
  printf "%d" "$((max * $1 / 100))"
}

get_status() {
  cat "$device/brightness"
}

get_percent() {
  to_percent "$(get_status)"
}

# Add $1 to current brightness. Adjust if out of bounds (0-$max)
# $1 is converted to a value between 0-$max within this function
get_total() {
  value="$(to_value "$1")"
  printf "%d" "$(($(get_status) + $value))"
}

helpmsg="Usage: backlightctl -[FLAG] [PERCENTAGE]
  -i, --increase: Increase brightness by n (default 10%)
  -d, --decrease: Decrease brightness by n (default 10%)
  -s, --set: Set brightness to specific value (default 50%)
  -g  --get: Get current brightness
  -q, --quiet: Don't send any notification (for use in dwmblocks)
  -h, --help: Print this help message
"

case "$1" in

-i | --increase)
  [ -z "$2" ] && step="$default_step" || step="$2"
  get_total "$step" >"$device/brightness"
  ;;

-d | --decrease)
  [ -z "$2" ] && step="$default_step" || step="$2"
  get_total "-$step" >"$device/brightness"
  ;;

-s | --set)
  [ -z "$2" ] && set="$default_set" || set="$2"
  to_value "$set" >"$device/brightness"
  ;;

-g | --get)
  printf "󰃠 %s\n" "$(get_status)%"
  ;;

-h | --help)
  printf "%s" "$helpmsg"
  ;;
*)
  printf "\033[31mInvalid option: $1\033[0m\n%s" "$helpmsg" && exit 1
  ;;
esac

# Send notification
case "$@" in
*-q* | *--quiet*)
  exit 0
  ;;
*)
  notify-send.sh -t 1000 --replace-file /tmp/bl-notif -a "󰃠 Brightness:" "$(get_percent)%"
  ;;
esac