// create-reducer.ts
import { Action } from 'redux';

type Handlers<State, Types extends string, Actions extends Action<Types>> = {
  readonly [Type in Types]: (state: State, action: Actions) => State
}

export const createReducer = (
  initialState,
  handlers,
) => (state = initialState, action) => (handlers.hasOwnProperty(action.type)
  ? handlers[action.type](state, action)
  : state);