Login Firebase and CometChat user

LoginActivity.kt

var auth = FirebaseAuth.getInstance()
auth.signInWithEmailAndPassword(bi.txtEmail.text.toString(), bi.txtPassword.text.toString())
    .addOnCompleteListener { task ->
        if (task.isSuccessful) {
            var firebaseUser = auth.currentUser
            CometChat.login(firebaseUser!!.uid, getString(R.string.auth_key), object : CometChat.CallbackListener<User>() {
                override fun onSuccess(u: User?) {
                    if (u?.metadata?.has("isDoctor") == true && u.metadata?.getBoolean("isDoctor") == true) {
                        val i = Intent(applicationContext, DoctorMainActivity::class.java)
                        i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP)
                        i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK)
                        i.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK)
                        startActivity(i)
                        finish()
                    }
                    else {
                        val i = Intent(applicationContext, MainActivity::class.java)
                        i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP)
                        i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK)
                        i.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK)
                        startActivity(i)
                        finish()
                    }
                }

                override fun onError(ex: CometChatException?) {
                    Snackbar.make(bi.root, ex?.localizedMessage ?: "Couldn't login CometChat user", Snackbar.LENGTH_SHORT).show()
                }
            })

        } else {
            Snackbar.make(bi.root, "Couldn't login Firebase user", Snackbar.LENGTH_SHORT).show()
        }
    }