#!/bin/bash
#
# Slowly dim the display when idle, reverting brightness when resuming.

set -euo pipefail

if (( $# > 0 )); then
  if [[ $1 == 'kill' ]]; then
    pkill idle-dimmer || true
    exit
  fi

  exit 1
fi

declare -i initial_value
initial_value=$(brightnessctl get)

function revert() {
  echo revert
  brightnessctl set "${initial_value}"
}

trap revert EXIT

declare -i sleep_interval_ms=$(( (100 - initial_value) * 1000 / 30 ))
# shellcheck disable=SC2155
declare -r sleep_interval=$(bc <<< "scale=2; $sleep_interval_ms / 1000" )
declare -i value=$initial_value
while (( --value >= 0 )); do
  brightnessctl set "${value}"
  sleep "${sleep_interval}"
done