{ lib, systemdUtils, pkgs }:

let
  inherit (systemdUtils.lib)
    automountConfig
    makeUnit
    mountConfig
    stage1ServiceConfig
    stage2ServiceConfig
    unitConfig
    ;

  inherit (systemdUtils.unitOptions)
    concreteUnitOptions
    stage1AutomountOptions
    stage1CommonUnitOptions
    stage1MountOptions
    stage1PathOptions
    stage1ServiceOptions
    stage1SliceOptions
    stage1SocketOptions
    stage1TimerOptions
    stage2AutomountOptions
    stage2CommonUnitOptions
    stage2MountOptions
    stage2PathOptions
    stage2ServiceOptions
    stage2SliceOptions
    stage2SocketOptions
    stage2TimerOptions
    ;

  inherit (lib)
    mkDefault
    mkDerivedConfig
    mkEnableOption
    mkIf
    mkOption
    ;

  inherit (lib.types)
    attrsOf
    lines
    listOf
    nullOr
    path
    submodule
    ;
in

rec {
  units = attrsOf (submodule ({ name, config, ... }: {
    options = concreteUnitOptions;
    config = { unit = mkDefault (makeUnit name config); };
  }));

  services = attrsOf (submodule [ stage2ServiceOptions unitConfig stage2ServiceConfig ]);
  initrdServices = attrsOf (submodule [ stage1ServiceOptions unitConfig stage1ServiceConfig ]);

  targets = attrsOf (submodule [ stage2CommonUnitOptions unitConfig ]);
  initrdTargets = attrsOf (submodule [ stage1CommonUnitOptions unitConfig ]);

  sockets = attrsOf (submodule [ stage2SocketOptions unitConfig ]);
  initrdSockets = attrsOf (submodule [ stage1SocketOptions unitConfig ]);

  timers = attrsOf (submodule [ stage2TimerOptions unitConfig ]);
  initrdTimers = attrsOf (submodule [ stage1TimerOptions unitConfig ]);

  paths = attrsOf (submodule [ stage2PathOptions unitConfig ]);
  initrdPaths = attrsOf (submodule [ stage1PathOptions unitConfig ]);

  slices = attrsOf (submodule [ stage2SliceOptions unitConfig ]);
  initrdSlices = attrsOf (submodule [ stage1SliceOptions unitConfig ]);

  mounts = listOf (submodule [ stage2MountOptions unitConfig mountConfig ]);
  initrdMounts = listOf (submodule [ stage1MountOptions unitConfig mountConfig ]);

  automounts = listOf (submodule [ stage2AutomountOptions unitConfig automountConfig ]);
  initrdAutomounts = attrsOf (submodule [ stage1AutomountOptions unitConfig automountConfig ]);

  initrdContents = attrsOf (submodule ({ config, options, name, ... }: {
    options = {
      enable = (mkEnableOption "copying of this file and symlinking it") // { default = true; };

      target = mkOption {
        type = path;
        description = ''
          Path of the symlink.
        '';
        default = name;
      };

      text = mkOption {
        default = null;
        type = nullOr lines;
        description = "Text of the file.";
      };

      source = mkOption {
        type = path;
        description = "Path of the source file.";
      };
    };

    config = {
      source = mkIf (config.text != null) (
        let name' = "initrd-" + baseNameOf name;
        in mkDerivedConfig options.text (pkgs.writeText name')
      );
    };
  }));
}