/**
  Modular function type
*/
{ lib, ... }:
let
  inherit (lib) mkOption types;
  inherit (types)
    submodule
    functionTo
    optionType
    ;
in
submodule (function: {
  options = {
    input-type = mkOption {
      type = optionType;
    };
    output-type = mkOption {
      type = optionType;
    };
    function-type = mkOption {
      type = optionType;
      # readOnly = true;
      default = functionTo (submodule {
        options = {
          input = mkOption {
            type = function.config.input-type;
          };
          output = mkOption {
            type = function.config.output-type;
          };
        };
      });
    };
  };
})