saga.js

import { eventChannel } from 'redux-saga'
import { take, spawn, put, takeLatest, takeEvery, call } from 'redux-saga/effects'
import { isEmpty } from 'ramda'

import * as actions from './auth_actions'

const provider = new firebase.auth.GoogleAuthProvider()

const authStateChannel = eventChannel((emit) => {
  firebase.auth().onAuthStateChanged((user) => {
    if (user) {
      emit({
        id: user.uid,
        email: user.email,
        name: user.displayName,
        photoUrl: user.photoURL,
      })
    } else {
      emit({})
    }
  })
  return () => {}
})

function* subscribeOnStateChannel() {
  while (true) {
    const user = yield take(authStateChannel)
    yield put(actions.setCurrentUser(isEmpty(user) ? null : user))
  }
}

function* requestLogin() {
  const auth = firebase.auth()
  try {
    yield call(auth.signInWithPopup.bind(auth), provider)
  } catch (e) {
    console.error(e)
  }
}

function* requestLogout() {
  const auth = firebase.auth()
  try {
    yield call(auth.signOut.bind(auth))
  } catch (e) {
    console.error(e)
  }
}

export default function* watch() {
  yield spawn(subscribeOnStateChannel)

  yield takeLatest(actions.requestLogin, requestLogin)
  yield takeEvery(actions.requestLogout, requestLogout)
}

thunk.js

const provider = new firebase.auth.GoogleAuthProvider()

export const setCurrentUser = user => ({ type: 'AUTH/SET_CURRENT_USER', payload: user })
setCurrentUser.toString = () => 'AUTH/SET_CURRENT_USER'

export const subscribeOnCurrentUserState = () => (dispatch) => {
  console.log('SUBSCRIBE')
  firebase.auth().onAuthStateChanged((user) => {
    if (user) dispatch(setCurrentUser({
        id: user.uid,
        email: user.email,
        name: user.displayName,
        photoUrl: user.photoURL,
      }))
    else dispatch(setCurrentUser(null))
  })
}

export const requestLogin = () => async (dispatch) => {
  const auth = firebase.auth()
  try {
    await auth.signInWithPopup(provider)
  } catch (e) { console.log(e) }
}

export const requestLogout = () => async (dispatch) => {
  const auth = firebase.auth()
  try {
    await auth.signOut()
  } catch (e) { console.error(e) }
}