actions.js

import { combineReducers } from 'redux'
import { createAction, reduceActions } from './playground';

export const addTodo = createAction('ADD_TODO', combineReducers({
  todos(state = [], text) {
    return [
      {
        id: state.reduce((maxId, todo) => Math.max(todo.id, maxId), -1) + 1,
        completed: false,
        text
      },
      ...state
    ];
  },
  history(state = {}, text) {
    return {
      ...state,
      lastEnteredText: text
    };
  }
}));

export const reducer = reduceActions([
  addTodo
], {});