type csfStory = unit => React.element;
type decorator = csfStory => React.element;

type csfMetadata('params) = {
  title: string,
  component: Js.Nullable.t(unit => React.element),
  decorators: Js.Nullable.t(array(decorator)),
  parameters: Js.Nullable.t('params),
  includeStories: Js.Nullable.t(array(string)),
  excludeStories: Js.Nullable.t(array(string)),
};

type storyMetadata('params) = {
  name: Js.Nullable.t(string),
  decorators: Js.Nullable.t(array(decorator)),
  parameters: Js.Nullable.t('params),
};

/**
  * Bucklescript renames a variables called `default` to `$$default` and exports that as well.
  */
let bsExports = [|"$$default"|];

[@bs.set]
external story: (csfStory, storyMetadata('params)) => unit = "story";

let make =
    (
      ~title,
      ~component=?,
      ~decorators=?,
      ~parameters=?,
      ~includeStories=?,
      ~excludeStories=?,
      (),
    ) => {
  title,
  component: component->Js.Nullable.fromOption,
  decorators: decorators->Js.Nullable.fromOption,
  parameters: parameters->Js.Nullable.fromOption,
  includeStories: includeStories->Js.Nullable.fromOption,
  excludeStories:
    excludeStories
    ->Belt.Option.mapWithDefault(bsExports, es =>
        es->Js.Array2.concat(bsExports)
      )
    ->Js.Nullable.return,
};

let addMeta = (csfStory, ~name=?, ~decorators=?, ~parameters=?, ()) =>
  csfStory->story({
    name: name->Js.Nullable.fromOption,
    decorators: decorators->Js.Nullable.fromOption,
    parameters: parameters->Js.Nullable.fromOption,
  });