import {
    createStore
  } from "redux";
  
  import rootReducer from './RootReducer'
  
  const LOCAL_STORAGE_NAME = "localData";
  
  class PersistedStore {
  
    // Singleton property
    static DefaultStore = null;
  
    // Accessor to the default instance of this class
    static getDefaultStore() {
      if (PersistedStore.DefaultStore === null) {
        PersistedStore.DefaultStore = new PersistedStore();
      }
  
      return PersistedStore.DefaultStore;
    }
  
    // Redux store
    _store = null;
  
    // When class instance is used, initialize the store
    constructor() {
      this.initStore()
    }
  
    // Initialization of Redux Store
    initStore() {
      this._store = createStore(rootReducer, PersistedStore.loadState());
      this._store.subscribe(() => {
        PersistedStore.saveState(this._store.getState());
      });
    }
  
    // Getter to access the Redux store
    get store() {
      return this._store;
    }
  
    // Loading persisted state from localStorage, no need to access
    // this method from the outside
    static loadState() {
      try {
        let serializedState = localStorage.getItem(LOCAL_STORAGE_NAME);
  
        if (serializedState === null) {
          return PersistedStore.initialState();
        }
  
        return JSON.parse(serializedState);
      } catch (err) {
        return PersistedStore.initialState();
      }
    }
  
    // Saving persisted state to localStorage every time something
    // changes in the Redux Store (This happens because of the subscribe() 
    // in the initStore-method). No need to access this method from the outside
    static saveState(state) {
      try {
        let serializedState = JSON.stringify(state);
        localStorage.setItem(LOCAL_STORAGE_NAME, serializedState);
      } catch (err) {}
    }
  
    // Return whatever you want your initial state to be
    static initialState() {
      return {};
    }
  }
  
  export default PersistedStore;