const {

  createStore,

  combineReducers,

  compose,

  bindActionCreators,

  applyMiddleware

} = Redux;

​

​

const initialState = { result: 0 };

​

const addAction = {

  type: 'ADD',

  value: 4

};

​

const calculatorReducer = (

  state = initialState,

  action

) => {

  if (action.type === 'ADD') {

    return {

      ...state,

      result: state.result + action.value

    }

  }

  return state;  

}

​

const subscriber = () => {

  console.log('SUBSCRIPTION!!!!', store.getState())

};

​

const logger = ({ getState }) => {

  return next => action => {

    console.log(

      'MIDDLEWARE',

      getState(),

      action

    );

    const value = next(action);

    console.log({value});

    return value;

  }

}

​

const initialError = { message: '' };

​

let errorMessageReducer = (

  state = initialError,

  action

) => {

  if (action.type === 'SET_ERROR_MESSAGE')

    return { message: action.message };

  if (action.type === 'CLEAR_ERROR_MESSAGE')

    return { message: '' };

  return state;

};

​

const store = createStore(combineReducers({

  calculator: calculatorReducer,

  error: errorMessageReducer

}), {}, applyMiddleware(logger));

​

const unsubscribe = store.subscribe(subscriber);

​

const add = value => ({ type: 'ADD', value });

​

const setError = (message) => (

  { type: 'SET_ERROR_MESSAGE', message}

);

​

const clearError = () => (

  { type: 'CLEAR_ERROR_MESSAGE' }

);

​

const bindActionCreator =

      (action, dispatch) => 

        (...args) => dispatch(action(...args));

​

const addValue = bindActionCreator(add, store.dispatch);

​

const bindActionCreatorz = (actions, dispatch) => {

  return Object.keys(actions).reduce((boundActions, key) => {

    boundActions[key] = bindActionCreator(actions[key], dispatch);

    return boundActions;

  }, {});

}

​

const errors = bindActionCreatorz({ 

  set: setError,

  clear: clearError

}, store.dispatch);

​

​

​