{
  lib,
  config,
  ...
}:
let
  inherit (lib) mkOption;
  inherit (lib.types)
    attrsOf
    attrTag
    deferredModuleWith
    mergeTypes
    nullOr
    submoduleWith
    submodule
    str
    ;
in
{
  options = {
    resources = mkOption {
      description = "Collection of deployment resources that can be configured by hosting providers and required by applications";
      type = attrsOf (
        submodule (
          { config, ... }:
          {
            _class = "fediversity-resource";
            options = {
              consumer = mkOption {
                description = "Configuration of the resource by an application, a description of how the resource is consumed";
                type = deferredModuleWith { staticModules = [ { _class = "fediversity-resource-consumer"; } ]; };
              };
              provider = mkOption {
                description = "Configuration of the resource by the hosting provider, a description of how the resource is made available";
                type = deferredModuleWith { staticModules = [ { _class = "fediversity-resource-provider"; } ]; };
              };
            };
          }
        )
      );
    };
    applications = mkOption {
      description = "Collection of Fediversity applications";
      type = attrsOf (
        submodule (application: {
          _class = "fediversity-application";
          options = {
            module = mkOption {
              description = "Operator-facing configuration options for the application";
              type = deferredModuleWith { staticModules = [ { _class = "fediversity-application-config"; } ]; };
            };
            config-mapping = mkOption {
              description = "Mapping of application configuration to deployment resources, a description of what an application needs to run";
              # TODO: type = (submodule application.config.module) -> (attrsOf (attrTag (lib.mapAttrs' (name: resource: { ${name} = mkOption { type = resource.consumer; }; }) config.resources))) /* something like that */
            };
          };
        })
      );
    };
    environments = mkOption {
      description = "Run-time environments for Fediversity applications to be deployed to";
      type = attrsOf (
        submodule (environment: {
          _class = "fediversity-environment";
          options = {
            resources = mkOption {
              description = "Resources made available by the hosting provider";
              type = attrsOf (
                attrTag (
                  lib.mapAttrs' (name: resource: {
                    ${name} = mkOption { type = resource.provider; };
                  }) config.resources
                )
              );
            };
            resource-mapping = mkOption {
              description = "Mapping of resources required by applications to available resources; the result can be deployed";
              # TODO: type = consumer-resources /* same as the output of application.config-mapping, should be in a `let` */ -> nixops4Deployment
            };
          };
        })
      );
    };
  };
}