import createStore from './createStore';
import combineReducers from './utils/combineReducers';
import bindActionCreators from './utils/bindActionCreators';
import applyMiddleware from './utils/applyMiddleware';
import compose from './utils/compose';

export {
  createStore,
  combineReducers,
  bindActionCreators,
  applyMiddleware,
  compose
};

import isPlainObject from './utils/isPlainObject';

/**
 * These are private action types reserved by Redux.
 * For any unknown actions, you must return the current state.
 * If the current state is undefined, you must return the initial state.
 * Do not reference these action types directly in your code.
 */
// 初始化的时候(redux.createStore(reducer, initialState)时),传的action.type 就是这货啦
export var ActionTypes = {
  INIT: '@@redux/INIT'
};

/**
 * Creates a Redux store that holds the state tree.
 * The only way to change the data in the store is to call `dispatch()` on it.
 *
 * There should only be a single store in your app. To specify how different
 * parts of the state tree respond to actions, you may combine several reducers
 * into a single reducer function by using `combineReducers`.
 *
 * @param {Function} reducer A function that returns the next state tree, given
 * the current state tree and the action to handle.
 *
 * @param {any} [initialState] The initial state. You may optionally specify it
 * to hydrate the state from the server in universal apps, or to restore a
 * previously serialized user session.
 * If you use `combineReducers` to produce the root reducer function, this must be
 * an object with the same shape as `combineReducers` keys.
 *
 * @returns {Store} A Redux store that lets you read the state, dispatch actions
 * and subscribe to changes.
 */
export default function createStore(reducer, initialState) {
  if (typeof reducer !== 'function') {
    throw new Error('Expected the reducer to be a function.');
  }

  var currentReducer = reducer;
  var currentState = initialState;
  var listeners = [];
  var isDispatching = false;

  /**
   * Reads the state tree managed by the store.
   *
   * @returns {an