Flow redux-act typings for making redux stores, entirely typed by action's payloads

redux-act.js

declare module 'redux-act' {
  
  /**
   * Single "action" as it referenced from classic redux
   * @typedef {{ type: string, payload: P }} Act.<P>
   * @template P
   */
  declare export
  type Act</*::+*/P = mixed> = {
    /*::+*/type: string,
    /*::+*/payload: P,
    error?: boolean,
  }

  /**
   * Function "action-creator", as it referenced from classic redux
   *
   * For us action-creator is nonsense; it *is* an action
   *
   * You have to use this as action type itself
   * @typedef {{(data: P) => Act}} Action.<P>
   * @template P
   * @export
   */
  declare export
  class Action<P = mixed> {
    (data: P): Act<P>,
    getType(): string,
  }
               
  declare export
  class AsyncAction<P = mixed, D = void, E = mixed> extends Action<P> {
    done: Action<{ params: P, result: D }>,
    fail: Action<{ params: P, error: E }>,
  }
               
  declare export
  function createAction<P>(description: string): Action<P>

  /**
   * Reducer, which represents typed state value
   *
   * Generic type S could be inferred from your
   *  state reduce functions
   *
   * @class ReduxField
   * @template S
   * @export
   */
  declare export
  class ReduxField<S> {
    (state: S, action: any): S,
    on<P, A/*::: Action<P> | $ReadOnlyArray<Action<P>>*/>(
      actions: A,
      reducer: (state: S, payload: P) => S
    ): ReduxField<S>,
  }

  declare export
  function createReducer<S>(
    untypedHandlers: {},
    defaults: S
  ): ReduxField<S>
}