saga.js

import { take, put, call } from 'redux-saga/effects';
import { eventChannel } from 'redux-saga';
import { push } from 'react-router-redux';
import actions from 'api/actions';
import reducer from 'api/reducers/crud';
import { loginMutation as mutation } from 'api/graphql/mutations';

function createSocketChannel(firebase) {
  return eventChannel((emit) => {
    return firebase.auth()
                   .onAuthStateChanged(user => emit(user || {}));
  });
}

function* watchLogged(firebase, graphqlClient) {
  const socketChannel = yield call(createSocketChannel, firebase);
  while (true) {
    const payload = yield take(socketChannel);
    if (payload.email) {
      const token = yield payload.getIdToken();
      const query = mutation({ token });
      yield call(graphqlClient.mutate, query);
      yield put({
        type: actions.FETCH_ENTITY_SUCCESSFUL,
        meta: {
          entity: 'user',
          reducer,
        },
        payload,
      });
    } else {
      yield put(push('/login'));
    }
  }
}

export default watchLogged;