#!/usr/bin/env bash
set -euo pipefail

state_dir="${XDG_RUNTIME_DIR:-/tmp}"
if [ ! -w "$state_dir" ]; then
  state_dir="${XDG_CACHE_HOME:-$HOME/.cache}"
  mkdir -p "$state_dir"
fi
if [ ! -w "$state_dir" ]; then
  state_dir="/tmp"
fi
state_file="$state_dir/polybar-display-night.state"

export DISPLAY="${DISPLAY:-:0}"
if [ -z "${XAUTHORITY:-}" ] && [ -r "$HOME/.Xauthority" ]; then
  export XAUTHORITY="$HOME/.Xauthority"
fi

output="$(
  xrandr --query 2>/dev/null |
    awk '/ connected primary/ { print $1; exit } / connected/ && !out { out = $1 } END { if (out) print out }'
)"

[ -n "$output" ] || exit 0

notify() {
  if command -v dunstify >/dev/null 2>&1; then
    dunstify -a polybar -u low "Display" "$1"
  fi
}

if [ -f "$state_file" ]; then
  xrandr --output "$output" --gamma 1:1:1
  rm -f "$state_file"
  notify "day mode"
else
  xrandr --output "$output" --gamma 1:0.88:0.72
  : >"$state_file"
  notify "night mode"
fi