.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}")
                      ( ${action}
                      )
                      ;;
            '') cfg.hooks;
          in
          ''
            xscreensaver-command -watch | while read event rest; do
              echo "The handler script got \"$event\""
              case $event in
                ${handlers}
              esac
            done
          '';
        path = [
          cfg.package # contains xscreensaver-command
        ];
      };
    };
  };
}