auth.service.js

(function() {
  'use strict';
  angular.module('app').
  factory('authService', ['$http', '$q', '$window',
    function($http, $q, $window) {			
      const storage = $window.localStorage;
      let cacheToken = {};
      return {
        getAuthorizationHeader() {
          if (cacheToken.access_token && cacheToken.expires_on > moment(new Date().getTime()).unix()) {
            return $q.when({'Authorization': 'Bearer ' + cacheToken.access_token});        
          } else {
            cacheToken.access_token = storage.getItem('access_token');
            cacheToken.refresh_token = storage.getItem('refresh_token');
            cacheToken.expires_on = storage.getItem('expires_on');                         
            if (cacheToken.access_token && cacheToken.expires_on > moment(new Date().getTime()).unix()) {
              return $q.when({'Authorization': 'Bearer ' + cacheToken.access_token});        
            } else {
              return $http.post('/refreshToken', {'token': cacheToken.refresh_token}).then(
                response => {
                  const token = response.data;
                  cacheToken.access_token = token.access_token;
                  storage.setItem('access_token', cacheToken.access_token);
                  cacheToken.refresh_token = token.refresh_token;
                  storage.setItem('refresh_token', cacheToken.refresh_token);
                  cacheToken.expires_on = token.expires_on;
                  storage.setItem('expires_on', cacheToken.expires_on);                                                                                                                                                
                  return {'Authorization': 'Bearer ' + cacheToken.access_token};    
                }, 
                err => {
                  console.log('Error refreshing token ' + err)
                }
              );
            }
          }                     
        }                
      }
    }
  ])
})()