Firebase.swift

import Firebase
import FirebaseFirestore
import FirebaseAuth
import FirebaseAuthUI
import FirebaseFacebookAuthUI
import FirebaseGoogleAuthUI
import FirebaseOAuthUI
import FirebasePhoneAuthUI
import FirebaseEmailAuthUI

//class ViewController: UIViewController, FUIAuthDelegate

//MARK: Manually Retrieve Data
///This method IS NOT listening for data changes on the server, and it only runs when explicitly called
let docRef = db.collection(userID).document("DOCNAME")
docRef.getDocument { (document, error) in
    if let document = document, document.exists {
        let dataDescription = document.data().map(String.init(describing:)) ?? "nil"
        print("Document data: \(dataDescription)")
        let data = document.data()!
        if data["VALUENAME"] != nil{
            //code goes here
        }
        if data["VALUENAME_2"] != nil{
            //code goes here
        }else{
            print("\n\n\nno value found\n\n\n")
            //code goes here
        }
        
    } else {
        print("Document does not exist")
    }
}

        
//MARK: Auto-Retrieve Data
///This method is constantly listening for data changes on the server, and will run automatically whenever new data is found
db.collection(userID).document("DOCNAME")
    .addSnapshotListener { documentSnapshot, error in
        guard let document = documentSnapshot else {
        print("Error fetching document: \(error!)")
        return
        }
        guard let data = document.data() else {
            print("Document data was empty.")
            //code goes here
        return
        }
        print("Current data: \(data)")
        //someLocalVariable = "\(data["VALUENAME"] ?? "name")"
        //code goes here
    }
    
    
    //MARK: -User Stuff (sign in/out)
    
    //MARK: viewDidAppear
    override func viewDidAppear(_ animated: Bool) {
        
        if didSignOut == true{
            signOutWithFirebase()
            didSignOut = false
        }
        
        if isUserSignedIn() {
            //userName = getData(documentName: "userInfo")
            performSegue(withIdentifier: "movePastSignIn", sender: nil)
        }
        
    }
    
    
     @IBAction func pressed(_ sender: Any) {
        print("\n\n\nPresenting AuthUI\n\n\n")
        
        let authUI = FUIAuth.defaultAuthUI()
        authUI!.delegate = self
        

        let providers: [FUIAuthProvider] = [
            FUIEmailAuth(),
//          FUIGoogleAuth(),
//          FUIFacebookAuth(),
//          FUITwitterAuth(),
//          FUIPhoneAuth(authUI:FUIAuth.defaultAuthUI()),
        ]
        authUI!.providers = providers
        
        let authViewController = authUI!.authViewController()
        
        present(authViewController, animated: true, completion: nil)
    }
    
    func authUI(_ authUI: FUIAuth, didSignInWith user: User?, error: Error?) {
        if error == nil{
            print("\n\n –– success –– \n\n")
            //userName = getData(documentName: "userInfo")
            guard let user = Auth.auth().currentUser else {return}
            userID = user.uid
            performSegue(withIdentifier: "movePastSignIn", sender: nil)
        }else{
            print("\n\n –– error –– \n\n")
        }
        
//        switch error{
//        case nil:
//            print("\n\n –– success –– \n\n")
//        default:
//            print("\n\n –– error –– \n\n")
//        }
    }
    
    
    func isUserSignedIn() -> Bool{
        if Auth.auth().currentUser != nil {
          // User is signed in.
            let user = Auth.auth().currentUser
            if let user = user {
              // The user's ID, unique to the Firebase project.
              // Do NOT use this value to authenticate with your backend server,
              // if you have one. Use getTokenWithCompletion:completion: instead.
              let uid = user.uid
              userID = uid
              let email = user.email
                updateUser(type: .email, value: user.email!)
              let photoURL = user.photoURL
              var multiFactorString = "MultiFactor: "
              for info in user.multiFactor.enrolledFactors {
                multiFactorString += info.displayName ?? "[DispayName]"
                multiFactorString += " "
              }
              // ...
            }
            
            //MARK: Auto-Retrieve Account Data
            db.collection(userID).document("userInfo")
                .addSnapshotListener { documentSnapshot, error in
                  guard let document = documentSnapshot else {
                    print("Error fetching document: \(error!)")
                    return
                  }
                  guard let data = document.data() else {
                    print("Document data was empty.")
                      userName = "false"
                    return
                  }
                  print("Current data: \(data)")
                  userName = "\(data)"
                }
            
          return true
        } else {
          // No user is signed in.
          return false
        }
    }
    
    
    
     //MARK: Sign-Out Button
    @IBAction func signOutPressed(_ sender: Any) {
        signOutWithFirebase()
        didSignOut = true
        //On the next line, replace "backToSignIn" with the segue identifier that leads back to the main sign-in page
        performSegue(withIdentifier: "backToSignIn", sender: self)
    }
    
    //MARK: Sign Out
    func signOutWithFirebase(){
        //Resetting AuthUI and its properties
        let authUI = FUIAuth.defaultAuthUI()
        authUI!.delegate = self
        let providers: [FUIAuthProvider] = [
            //3FUIGoogleAuth(),
            FUIEmailAuth(),
            /*FUIPhoneAuth(authUI:FUIAuth.defaultAuthUI()!),*/
        ]
        authUI!.providers = providers
        
        //Signing out of everything...
        let firebaseAuth = Auth.auth()
        do {
            try authUI!.signOut()
            try firebaseAuth.signOut()
            userID = ""
        } catch {
            print("Uh-Oh")
        }
    }