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

let
  inherit (lib)
    mkOption
    types
    optionalString
    ;

  cfg = config.services.swayosd;

in
{
  meta.maintainers = [ lib.hm.maintainers.pltanton ];

  imports = [
    (lib.mkRemovedOptionModule [
      "services"
      "swayosd"
      "display"
    ] "The --display flag is no longer available in swayosd-server.")
  ];

  options.services.swayosd = {
    enable = lib.mkEnableOption ''
      swayosd, a GTK based on screen display for keyboard shortcuts like
      caps-lock and volume'';

    package = lib.mkPackageOption pkgs "swayosd" { };

    topMargin = mkOption {
      type = types.nullOr (
        types.addCheck types.float (f: f >= 0.0 && f <= 1.0)
        // {
          description = "float between 0.0 and 1.0 (inclusive)";
        }
      );
      default = null;
      example = 1.0;
      description = "OSD margin from top edge (0.5 would be screen center).";
    };

    stylePath = mkOption {
      type = types.nullOr types.path;
      default = null;
      example = "/etc/xdg/swayosd/style.css";
      description = ''
        Use a custom Stylesheet file instead of looking for one.
      '';
    };
  };

  config = lib.mkIf cfg.enable {
    assertions = [
      (lib.hm.assertions.assertPlatform "services.swayosd" pkgs lib.platforms.linux)
    ];

    home.packages = [ cfg.package ];

    systemd.user = {
      services.swayosd = {
        Unit = {
          Description = "Volume/backlight OSD indicator";
          PartOf = [ config.wayland.systemd.target ];
          After = [ config.wayland.systemd.target ];
          ConditionEnvironment = "WAYLAND_DISPLAY";
          Documentation = "man:swayosd(1)";
          StartLimitBurst = 5;
          StartLimitIntervalSec = 10;
        };

        Service = {
          Type = "simple";
          ExecStart =
            "${cfg.package}/bin/swayosd-server"
            + (optionalString (cfg.stylePath != null) " --style ${lib.escapeShellArg cfg.stylePath}")
            + (optionalString (cfg.topMargin != null) " --top-margin ${toString cfg.topMargin}");
          Restart = "always";
          RestartSec = "2s";
        };

        Install = {
          WantedBy = [ config.wayland.systemd.target ];
        };
      };
    };
  };
}