{lib, ...}: let
  folderType = lib.types.submodule ({name, ...}: {
    options = {
      id = lib.mkOption {
        type = lib.types.str;
      };
      label = lib.mkOption {
        type = lib.types.str;
        default = name;
      };
    };
  });
in {
  folders = lib.mkOption {
    type = lib.types.attrsOf folderType;
    default = {};
  };
  devices = lib.mkOption {
    type = lib.types.attrsOf (lib.types.submodule ({name, ...}: {
      options = {
        name = lib.mkOption {
          type = lib.types.str;
          default = name;
        };
        id = lib.mkOption {
          type = lib.types.str;
        };
        folders = lib.mkOption {
          type = lib.types.attrsOf (lib.types.submodule (
            {config, ...}: {
              options = {
                folder = lib.mkOption {
                  type = folderType;
                };
                path = lib.mkOption {
                  type = lib.types.str;
                };
                type = lib.mkOption {
                  type = lib.types.enum ["sendreceive" "sendonly" "receiveonly" "receiveencrypted"];
                  default = "sendreceive";
                };
                versioning = {
                  simple = {
                    enable = lib.mkEnableOption "should this folder use simple versioning";
                    keep = lib.mkOption {
                      type = lib.types.str;
                      default = "10";
                    };
                  };
                  trashcan = {
                    enable = lib.mkEnableOption "should this folder use trashcan versioning";
                    cleanoutDays = lib.mkOption {
                      type = lib.types.str;
                      default = "1000";
                    };
                  };
                  staggered = {
                    enable = lib.mkEnableOption "should this folder use staggard versioning";
                    cleanInterval = lib.mkOption {
                      type = lib.types.str;
                      default = "3600";
                    };
                    maxAge = lib.mkOption {
                      type = lib.types.str;
                      default = "31536000";
                    };
                  };
                  external = {
                    enable = lib.mkEnableOption "should this folder use external versioning";
                  };
                };
              };
              # TODO: figure out how to make assertions for submodules
              # config = {
              #   assertions =
              #     (lib.lists.optionals config.versioning.simple.enable [
              #       {
              #         assertion = !config.versioning.trashcan.enable;
              #         message = "Can not use both simple and trashcan versioning at the same time.";
              #       }
              #       {
              #         assertion = !config.versioning.staggered.enable;
              #         message = "Can not use both simple and staggered versioning at the same time.";
              #       }
              #       {
              #         assertion = !config.versioning.external.enable;
              #         message = "Can not use both simple and external versioning at the same time.";
              #       }
              #     ])
              #     ++ (lib.lists.optionals config.versioning.trashcan.enable [
              #       {
              #         assertion = !config.versioning.staggered.enable;
              #         message = "Can not use both trashcan and staggered versioning at the same time.";
              #       }
              #       {
              #         assertion = !config.versioning.external.enable;
              #         message = "Can not use both trashcan and external versioning at the same time.";
              #       }
              #     ])
              #     ++ (lib.lists.optionals config.versioning.staggered.enable [
              #       {
              #         assertion = !config.versioning.external.enable;
              #         message = "Can not use both staggered and external versioning at the same time.";
              #       }
              #     ])
              #     ++ [
              #       {
              #         assertion = !config.versioning.external.enable;
              #         message = "External versioning currently not implemented.";
              #       }
              #     ];
              # };
            }
          ));
        };
      };
    }));
    default = {};
  };
}