{ config, lib, pkgs, ... }:

let
  inherit (lib) getExe getExe' mkOption types;
in

{
  options.custom.backgroundDir = mkOption {
    default = config.home.homeDirectory + "/Pictures/Backgrounds";
    type = with types; uniq str;
  };
  
  config = {
    services.swww.enable = true;
    systemd.user = {
      services.swww-randomize = {
        Unit = {
          Description = "randomly change the swww background image";
          Requires = "swww.service";
        };
        Service = {
          Type = "oneshot";
          ExecStart = "${getExe pkgs.bash} -c '${getExe pkgs.findutils} ${config.custom.backgroundDir} -type f | ${getExe' pkgs.coreutils "shuf"} -n 1 | ${getExe' pkgs.findutils "xargs"} ${getExe pkgs.swww} img --transition-step 16'";
        };
        Install.WantedBy = [ "default.target" ];
      };
      timers.swww-randomize = {
        Unit.Description = "randomly changes the swww background image";
        Timer = {
          Unit = "swww-random";
          OnCalendar = "*-*-* *:00,30:00";
        };
        Install.WantedBy = [ "timers.target" ];
      };
    };
  };
}