nixcfg/homeManagerModules/services/randomWallpaper/default.nix

{
  config,
  lib,
  pkgs,
  ...
}: let
  wallpaperD = pkgs.writers.writeRuby "randomWallpaperD" {} ''
    require 'fileutils'

    directory = "${config.xdg.dataHome}/backgrounds/"
    current_pids = {}
    known_monitors = {}
    last_update_time = {}

    update_interval = 900 # 15 minutes in seconds

    xdg_runtime_dir = ENV['XDG_RUNTIME_DIR']
    hyprland_instance_signature = ENV['HYPRLAND_INSTANCE_SIGNATURE']
    sway_sock = ENV['SWAYSOCK']

    hyprland_lock_path = nil

    unless hyprland_instance_signature.nil?
      hyprland_lock_path = File.join(xdg_runtime_dir, 'hypr', hyprland_instance_signature, 'hyprland.lock')
    end

    def wm_dead? (hyprland_lock_path, sway_sock)
      sway_running = system("pidof sway > /dev/null")
      hypr_running = system("pidof Hyprland > /dev/null")
      (hyprland_lock_path.nil? || !File.exist?(hyprland_lock_path) || !hypr_running) && (sway_sock.nil? || !File.exist?(sway_sock) || !sway_running)
    end

    def get_outputs
      hyprctl = IO.popen(["${lib.getExe' config.wayland.windowManager.hyprland.package "hyprctl"}", 'monitors']).read
      swaymsg = IO.popen(["${lib.getExe' config.wayland.windowManager.sway.package "swaymsg"}", '-t', 'get_outputs', '-p']).readlines

      hypr_outputs = hyprctl.each_line.map { |line| line.split[1] if line.include?('Monitor') }.compact
      sway_outputs = swaymsg.select { |line| line.include?('Output') }.map { |line| line.split[1] }

      return (sway_outputs | hypr_outputs)
    end

    sleep 1

    loop do
      active_monitors = get_outputs

      break if wm_dead? hyprland_lock_path, sway_sock
      next if active_monitors.empty?

      added_monitors = active_monitors - known_monitors.keys
      removed_monitors = known_monitors.keys - active_monitors

      # Handle newly added monitors
      added_monitors.each do |monitor|
        random_background = Dir.glob(File.join(directory, '*.{png,jpg}')).sample
        pid = spawn("${lib.getExe pkgs.swaybg}", '-o', monitor, '-i', random_background, '-m', 'fill')
        current_pids[monitor] = pid
        last_update_time[monitor] = Time.now
        known_monitors[monitor] = random_background
      end

      # Remove wallpapers from removed monitors
      removed_monitors.each do |monitor|
        Process.kill('TERM', current_pids[monitor]) if current_pids[monitor]
        current_pids.delete(monitor)
        last_update_time.delete(monitor)
        known_monitors.delete(monitor)
      end

      # Update wallpapers after the set interval
      active_monitors.each do |monitor|
        if Time.now - last_update_time[monitor] >= update_interval
          random_background = Dir.glob(File.join(directory, '*.{png,jpg}')).sample
          pid = spawn("${lib.getExe pkgs.swaybg}", '-o', monitor, '-i', random_background, '-m', 'fill')
          sleep 1
          Process.kill('TERM', current_pids[monitor]) if current_pids[monitor]
          current_pids[monitor] = pid
          last_update_time[monitor] = Time.now
          known_monitors[monitor] = random_background
        end
      end

      sleep 3
    end
  '';
in {
  config = lib.mkIf config.ar.home.services.randomWallpaper.enable {
    wayland.windowManager.sway.config.output."*" = lib.mkForce {}; # Dirty. TODO: make more elegant.

    systemd.user.services.randomWallpaper = {
      Unit = {
        After = "graphical-session.target";
        BindsTo = lib.optional (config.ar.home.desktop.hyprland.enable) "hyprland-session.target" ++ lib.optional (config.ar.home.desktop.sway.enable) "sway-session.target";
        Description = "Lightweight swaybg-based random wallpaper daemon.";
        PartOf = "graphical-session.target";
      };

      Service = {
        ExecStart = "${wallpaperD}";
        Restart = "no";
      };

      Install.WantedBy = lib.optional (config.ar.home.desktop.hyprland.enable) "hyprland-session.target" ++ lib.optional (config.ar.home.desktop.sway.enable) "sway-session.target";
    };
  };
}