#!/usr/bin/env bash
# rice-screensaver - classic xscreensaver hacks, full screen.
#
#   rice-screensaver start [hack]   random hack from the list (rice-idle runs this)
#   rice-screensaver stop
#   rice-screensaver now [hack]     start by hand; press q or Escape in it to stop
#   rice-screensaver list           hacks available on this machine
#
# Pick your own set by listing hack names, one per line, in
# ~/.config/rice/screensavers.
set -uo pipefail

hackdir=/usr/lib/xscreensaver
run="${XDG_RUNTIME_DIR:-/tmp}/rice"
pidfile="$run/screensaver.pid"
mkdir -p "$run"

defaults="glmatrix flurry pipes fireworkx galaxy atlantis lament gears starfish xmatrix boxfit"
user_list="${XDG_CONFIG_HOME:-$HOME/.config}/rice/screensavers"

available() {
  local names h
  if [[ -f $user_list ]]; then names=$(grep -v '^\s*#' "$user_list"); else names=$defaults; fi
  for h in $names; do [[ -x $hackdir/$h ]] && echo "$h"; done
}

stop() {
  [[ -f $pidfile ]] && kill "$(cat "$pidfile")" 2>/dev/null
  rm -f "$pidfile"
}

start() {
  local hack="${1:-}" pid wid
  stop
  if [[ -z $hack ]]; then hack=$(available | shuf -n1); fi
  [[ -n $hack && -x $hackdir/$hack ]] || { echo "rice-screensaver: no hack available (install xscreensaver)" >&2; exit 1; }
  [[ $hack =~ ^[a-z0-9_-]+$ ]] || exit 2

  "$hackdir/$hack" >/dev/null 2>&1 &
  pid=$!
  echo "$pid" > "$pidfile"
  # Hacks open an ordinary window; hand it to bspwm as a fullscreen node.
  wid=$(xdotool search --sync --onlyvisible --pid "$pid" 2>/dev/null | head -n1)
  [[ -n $wid ]] && bspc node "$wid" -t fullscreen -f 2>/dev/null
}

case "${1:-}" in
  start) start "${2:-}" ;;
  now)   start "${2:-}" ;;
  stop)  stop ;;
  list)  available ;;
  *) sed -n '2,11p' "$0" | sed 's/^# \{0,1\}//'; exit 2 ;;
esac