SignInVC.swift

//
//  SignInVC.swift
//  Dog_Log
//
//  Created by Ron Marks on 1/6/17.
//  Copyright © 2017 Ron Marks. All rights reserved.
//

import UIKit
import Firebase
import GoogleSignIn
import CoreData
import FBSDKLoginKit

class LoginVC: UIViewController, GIDSignInUIDelegate, GIDSignInDelegate {
    
    var managedObjectContext: NSManagedObjectContext!
    
    @IBOutlet weak var googleButton: UIButton!
    @IBOutlet weak var fbButton: UIButton!
    
    var ref: FIRDatabaseReference!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        GIDSignIn.sharedInstance().uiDelegate = self
        GIDSignIn.sharedInstance().delegate = self
        ref = FIRDatabase.database().reference()
        
        FBSDKLoginManager().logOut()  // clear current token
    }
    
    
    // google sign in
    @IBAction func googleTouch(_ sender: UIButton) {
        disableGoogleButton()
        GIDSignIn.sharedInstance().signIn()
    }
    
    // fb sign in
    @IBAction func fbTouch(_ sender: Any) {
        disableFacebookButton()
        let login = FBSDKLoginManager()
        login.logIn(withReadPermissions: ["public_profile", "email"], from: self, handler: { (result, error) in
            if error == nil {
                if !(result?.isCancelled)! {
                    self.getFBUserData()
                } else {
                    self.enableFacebookButton()
                }
            } else {
                print(error?.localizedDescription)
                self.enableFacebookButton()
            }
        })
    }
    
    // attempt to sign in user with fb
    // cases:
    // 1) user's facebook does have email. This is common case
    //         - in this case, sign them into Firebase
    //               - could be that they previously didn't have email but now they do, so update Firebase user's email
    //         - could be that a firebase account with their email already exists, throw error
    //         - otherwise everything went fine, segue to home page
    // 2) user's facebook account could have no email associated (or disabled email permissions). This is a rare case
    //         - in this case, take user to manual email input page
    //         - or user could've already done above step, in which case just log them in normally
    func getFBUserData(){
        if((FBSDKAccessToken.current()) != nil){
            FBSDKGraphRequest(graphPath: "me", parameters: ["fields": "name, email"]).start(completionHandler: { (connection, result, error) -> Void in
                if error == nil, let res = result as? [String: String]{
                    let credential = FIRFacebookAuthProvider.credential(withAccessToken: FBSDKAccessToken.current().tokenString)
                    if res["email"] != nil {  // facebook account has email
                        // CASE 1
                        print("user has email")
                        FIRAuth.auth()?.signIn(with: credential, completion: { (user, error) in  // sign user into Firebase
                            if error == nil && user != nil {
                                if user!.email == nil {      // Firebase user has no email
                                    user!.updateEmail(res["email"]!, completion: { error in  // user has no email, set email
                                        if error != nil {
                                            if let errCode = FIRAuthErrorCode(rawValue: error!._code) {
                                                switch errCode {
                                                case .errorCodeEmailAlreadyInUse:  // email is already in use by another account
                                                    self.showEmailTakenAlert()
                                                default:
                                                    self.showRegistrationErrorAlert()
                                                }
                                            }
                                            self.enableFacebookButton()
                                        } else {  // user previously had no email but now does
                                            print("email set")
                                            self.setUserInfoAndSegue()
                                        }
                                    })
                                } else {  // user has email, everything went fine
                                    print("signed into Firebase with facebook successfully")
                                    self.setUserInfoAndSegue()
                                }
                            } else {  // some error happened
                                if let errCode = FIRAuthErrorCode(rawValue: error!._code) {
                                    switch errCode {
                                    case .errorCodeEmailAlreadyInUse:  // email is already in use by another account
                                        self.showEmailTakenAlert()
                                    default:
                                        self.showRegistrationErrorAlert()
                                    }
                                    self.enableFacebookButton()
                                }
                            }
                        })
                    } else {  // no email associated with facebook account
                        // CASE 2
                        print("user has no email")
                        FIRAuth.auth()?.signIn(with: credential, completion: { (user, error) in
                            if let user = user {
                                if user.email != nil {   // user has already typed in email manually
                                    self.setUserInfoAndSegue()
                                } else {                 // make user type in email manually
                                    print("user has no email")
                                    let storyboard = UIStoryboard(name: "Main", bundle: nil)
                                    let controller = storyboard.instantiateViewController(withIdentifier: "EmailTyper") as? EmailTyperVC
                                    controller?.managedObjectContext = self.managedObjectContext
                                    self.present(controller!, animated: true, completion: nil)
                                }
                            } else {
                                self.enableFacebookButton()
                            }
                        })
                    }
                } else {
                    self.enableFacebookButton()
                }
            })
        } else {
            self.enableFacebookButton()
        }
    }
    


    /// Handle Google Sign in
    ///
    func sign(_ signIn: GIDSignIn!, didSignInFor user: GIDGoogleUser!, withError error: Error!) {
        if error != nil {
            self.showRegistrationErrorAlert()
            self.enableGoogleButton()
            return
        }
        
        guard let idToken = user.authentication.idToken else {
            self.enableGoogleButton()
            return
        }
        guard let accessToken = user.authentication.accessToken else { return }
        let credentials = FIRGoogleAuthProvider.credential(withIDToken: idToken, accessToken: accessToken)
        
        // check if account with email already exists
        FIRAuth.auth()?.fetchProviders(forEmail: user.profile.email, completion: { result, error in
            if let error = error {
                self.showRegistrationErrorAlert()
                return
            }
            if let result = result {
                if result.count > 0 {
                    if result[0] == "facebook.com" {   // facebook account already exists with email
                        self.showEmailTakenAlert()
                        self.enableGoogleButton()
                        return
                    }
                }
            }
            FIRAuth.auth()?.signIn(with: credentials, completion: { (user, error) in
                if error != nil {
                    self.showRegistrationErrorAlert()
                    self.enableGoogleButton()
                    return
                }
                print("Successfully logged into firebase with google")
                self.setUserInfoAndSegue()
            })
        })
    }
    
    
    /// See if user is already in database, if not then set data. Then segue to home screen
    ///
    func setUserInfoAndSegue(){
        if let user = FIRAuth.auth()?.currentUser {
            UserDefaults.standard.setValue(user.uid, forKey: "CurrentUser")
            if let email = user.email, let name = user.displayName {
                // See if user is already in database
                let userRef = FIRDatabase.database().reference().child("users").child(user.uid)
                userRef.observeSingleEvent(of: .value, with: { snapshot in
                    // User not in db yet, add data then segue to home view
                    if !snapshot.exists() {
                        let nameRef = FIRDatabase.database().reference().child("allUsers").child(email.cleanString())
                        nameRef.setValue(["name": name.lowercased(), "uid": user.uid])
                        userRef.setValue(["name": name, "pets": false, "invites": false, "email": email]) { (error, ref) -> Void in
                            if (error != nil){
                                print(error!)
                            } else {
                                self.dismiss(animated: true, completion: nil)
                            }
                        }
                    } else {   // User is already in db, segue to home view
                        self.dismiss(animated: true, completion: nil)
                    }
                })
            }
        }
    }
    
    
    // account with email already exists alert
    func showEmailTakenAlert(){
        let alert = UIAlertController(title: "Registration Error", message: "Your email is already registered with another account", preferredStyle: UIAlertControllerStyle.alert)
        alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.default, handler: nil))
        self.present(alert, animated: true, completion: nil)
    }
    
    // some errror occurred alert
    func showRegistrationErrorAlert(){
        let alert = UIAlertController(title: "Registration Error", message: "Something went wrong, please try again later", preferredStyle: UIAlertControllerStyle.alert)
        alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.default, handler: nil))
        self.present(alert, animated: true, completion: nil)
    }
    
    // for when user presses facebook button
    func disableFacebookButton(){
        self.fbButton.isEnabled = false
        self.googleButton.isUserInteractionEnabled = false
    }
    func enableFacebookButton(){
        self.fbButton.isEnabled = true
        self.googleButton.isUserInteractionEnabled = true
    }
    
    // for when user pressed google button
    func disableGoogleButton(){
        self.googleButton.isEnabled = false
        self.fbButton.isUserInteractionEnabled = false
    }
    func enableGoogleButton(){
        self.googleButton.isEnabled = true
        self.fbButton.isUserInteractionEnabled = true
    }
}