import Ember from 'ember';
import hbs from 'htmlbars-inline-precompile';

const createStore = (reducer) => {
  var pointer = 0;
  var state = [];
  var listeners = [];
  var firstState = reducer();
  state.push(firstState);
  var store = {
    getState() {
      return state[pointer];
    },
    dispatch(action) {
      var nextState = reducer(state[pointer], action);
      pointer++;
      state.push(nextState);
      listeners.forEach((callback) => {
        callback();
      });
    },
    subscribe(callback) {
      listeners.push(callback);
    },
    goBack() {
      pointer--;
      listeners.forEach((callback) => {
        callback();
      });
    },
    goForward() {
      pointer++;
      listeners.forEach((callback) => {
        callback();
      });
    }
  }
  return store;
};

const reducer = (state = 0, action) => {
  if (action && action.type === 'ADD') {
    console.log('ADDING!');
    return state + 1;
  }
  return state;
};

const store = createStore(reducer);

export default Ember.Component.extend({
  init() {
    this._super(...arguments);
    store.subscribe(() => {
      this.notifyPropertyChange('number');
    });
  },
  number: Ember.computed(function() {
    return store.getState();
  }),
  actions: {
    add() {
      store.dispatch({type: 'ADD'});
    },
    back() {
      store.goBack();
    },
    forward() {
      store.goForward();
    }
  },
  layout: hbs`
    <h1>{{number}}</h1>
    <button onclick={{action "add"}}>ADD</button>
<button onclick={{action "back"}}>Back</button>
<button onclick={{action "forward"}}>Forward</button>
  `
});