.files/nix/nixosModules/common/xscreensaver.nix

#
# This module provides a service react to xscreensaver events
#
{
  config,
  lib,
  ...
}: let
  cfg = config.services.xscreensaver;
in {
  options = {
    services.xscreensaver.hooks = lib.mkOption {
      type = with lib.types; attrsOf str;
      description = "An attrset of events mapped a block of shell command to be run";
      default = {};
    };
  };

  config = lib.mkIf cfg.enable {
    systemd.user.services = {
      "xscreensaver-hooks" = {
        description = "Run commands on xscreensaver events";
        after = ["graphical-session.target" "xscreensaver.service"];
        partOf = ["graphical-session.target"];
        wantedBy = ["graphical-session.target"];
        script = let
          handlers =
            lib.concatMapAttrsStringSep "\n" (event: action: ''
              "${event}")
                      ( ${action}
                      )
                      ;;
            '')
            cfg.hooks;
        in ''
          xscreensaver-command -watch | while read event rest; do
            case $event in
              ${handlers}
            esac
          done
        '';
        path = [
          cfg.package # contains xscreensaver-command
        ];
      };
    };
  };
}