firebase-auth-controller.js

// import the firebase config into the auth controller
import firebase from '../../firebase';

const firebaseAuth = async (req, res) => {
  try {
    // req.body the payload coming from the client to authenticate the user
    // uid is the firebase uid generated when a user is authenticated on the firebase client
    const userRequest = await firebase.database().ref(`users/${req.body.uid}`).once('value');
    const userPayload = userRequest.val();
    
    if (userPayload) {
      // create tokenClaims if you wish to add extra data to the generated user token
      const tokenClaims = {
        roleId: userPayload.roleId
      }

      // use firebase admin auth to set token claimsm which will be decoded for additional authentication
      await firebase.auth().setCustomUserClaims(user.uid, tokenClaims);
      
      return res.status(200).json({data: tokenClaims});
    } else {
      return res.status(404).json({error: {message: 'No user found'}});
    }
  } catch (error) {
    return res.status(500).json({
      error: { message: 'could not complete auth request'}
    });
  }
}

export default {
  firebaseAuth
}