{
  pkgs,
  config,
  lib,
  ...
}:
let
  cfg = config.xyno.desktop.wpaperd;
  # wpaperdConf = pkgs.writeText "wpaperd.conf" ''
  #   [default]
  #   path = "/home/${config.xyno.system.user.name}/Pictures/backgrounds"
  #   duration = "10m"
  #   sorting = "random"
  #   mode = "center"
  # '';
in
{
  options.xyno.desktop.wpaperd.enable = lib.mkEnableOption "enable wpaperd wallpaper daemon";
  options.xyno.desktop.wpaperd.wantedBy = lib.mkOption {
    type = lib.types.str;
    default = "niri.service";
  };
  options.xyno.desktop.wpaperd.package = lib.mkOption {
    type = lib.types.package;
    default = pkgs.swww;
  };
  config = lib.mkIf cfg.enable {
    environment.systemPackages = [ cfg.package ];
    xyno.desktop.niri.extraConfig = ''
      // Put swww inside the overview backdrop.
      layer-rule {
          match namespace="^swww.*$"
          place-within-backdrop true
      }
        
      '';
        
    systemd.user.services.swww-daemon = {
      unitConfig.PartOf = "graphical-session.target";
      unitConfig.After = "graphical-session.target";
      unitConfig.Requisite = "graphical-session.target";
      serviceConfig.Restart = "on-failure";
      wantedBy = [ cfg.wantedBy ];
      script = ''
        exec ${cfg.package}/bin/swww-daemon'';
    };
    systemd.user.services.swww-randomize = {
      unitConfig.PartOf = "graphical-session.target";
      unitConfig.After = "graphical-session.target";
      unitConfig.Requisite = "graphical-session.target";
      serviceConfig.Restart = "on-failure";
      wantedBy = [ "swww-daemon.service" ];
      script = ''
        set -eox
        export DEFAULT_INTERVAL=300 # In seconds
        export DIR=''$HOME/Pictures/backgrounds

        # See swww-img(1)
        RESIZE_TYPE="crop"
        export SWWW_TRANSITION_FPS="120"
        export SWWW_TRANSITION="fade"
        export SWWW_TRANSITION_DURATION="1"
        # export SWWW_TRANSITION_STEP="90"

        while true; do
        	find "''$DIR" -type f \
        	| while read -r img; do
        		echo "''$(</dev/urandom tr -dc a-zA-Z0-9 | head -c 8):''$img"
        	done \
        	| sort -n | cut -d':' -f2- \
        	| while read -r img; do
        		for d in ''$(${cfg.package}/bin/swww query | grep -Po "^[^:]+"); do # see ${cfg.package}/bin/swww-query(1)
        			# Get next random image for this display, or re-shuffle images
        			# and pick again if no more unused images are remaining
        			[ -z "''$img" ] && if read -r img; then true; else break 2; fi
        			${cfg.package}/bin/swww img --resize "''$RESIZE_TYPE" --outputs "''$d" "''$img"
        			unset -v img # Each image should only be used once per loop
        		done
        		sleep "''${DEFAULT_INTERVAL}"
        	done
        done
      '';
      # restartTriggers = [wpaperdConf];
    };
  };
}