#!/usr/bin/env bash
#
# Recursively searches the specified directory (the first script argument),
# randomly selects one image, and set that image as the wallpaper.
#
# Usage:
#   random_wallpaper.sh /path/to/wallpapers
#
# Requirements (X11):
#   feh
#
# Requirements (Wayland):
#   swaybg
#

x11_set() {
  local wallpaper="${1}"

  # Check for feh
  type -p feh 2>/dev/null 1>/dev/null
  if [ $? -eq 1 ]; then
    echo "Required program 'feh' not found. Please install and run again."
    return 1
  fi

  # Set the wallpaper
  feh --bg-fill "${wallpaper}"
}

wayland_set() {
  local wallpaper="${1}"
  local pidfile=/dev/shm/swaybg-$(whoami).pid
  printf 'Setting wallpaper to %s\n' "${wallpaper}"

  swaybg -o '*' -i "${wallpaper}" -m fill 2>/dev/null 1>/dev/null &
  echo $! > "${pidfile}.new"
  sleep .5

  if [ -f "${pidfile}" ] && [ -d /proc/$(cat ${pidfile}) ]; then
    kill $(cat "${pidfile}")
  fi
  mv "${pidfile}.new" "${pidfile}"
}

# Make sure a wallpaper path was specified
if [ -z ${1} ]; then
  echo "Please specify a wallpaper path."
  exit 1
fi

search_path=${@}
randpic=$(find ${search_path} -type f \
            -iname '*.jpg' \
            -o -iname '*.png' \
            | sort -R | head -n 1)

if [ -n "${WAYLAND_DISPLAY:-}" ]; then
  wayland_set "${randpic}"
elif [ -n "${DISPLAY:-}" ]; then
  x11_set "${randpic}"
else
  printf 'ERROR: Could not detect display manager\n'
  exit 1
fi