let isAlreadyFetchingAccessToken = false;
let subscribers = [];

function onAccessTokenFetched(accessToken) {
  subscribers = subscribers.filter(callback => callback(accessToken));
}

function addSubscriber(callback) {
  subscribers.push(callback);
}

$axios.interceptors.response.use(
  response => {
    return response;
  },
  error => {
    const {
      config,
      response: { status }
    } = error;
    const originalRequest = config;

    if (status === 401) {
      if (!isAlreadyFetchingAccessToken) {
        isAlreadyFetchingAccessToken = true;

        localforage.getItem('user').then(user => {
          const req = {
            accessToken: user.accessToken,
            refreshToken: user.refreshToken
          };

          $axios.post('tokens/refresh', req).then(response => {
            user.accessToken = response.data.accessToken;

            localforage.setItem('user', user).then(value => {
              store.commit('SET_ACCESS_TOKEN', value.accessToken);

              isAlreadyFetchingAccessToken = false;
              onAccessTokenFetched(user.accessToken);
            });
          });
        });
      }

      const retryOriginalRequest = new Promise(resolve => {
        addSubscriber(accessToken => {
          originalRequest.headers.Authorization = 'Bearer ' + accessToken;
          resolve($axios(originalRequest));
        });
      });
      return retryOriginalRequest;
    }
    return Promise.reject(error);
  }
);