******************** SDK set up and foreground message handling. ***************


<script>
        // Initialize Firebase
        var config = {
            apiKey: "AIzaSyCpxieXvbvbUuQy9vFQFX1ZxvVKyID2chY",
            authDomain: "detroitechcallcenterapp.firebaseapp.com",
            databaseURL: "https://detroitechcallcenterapp.firebaseio.com",
            projectId: "detroitechcallcenterapp",
            storageBucket: "detroitechcallcenterapp.appspot.com",
            messagingSenderId: "94883233124"
        };
        firebase.initializeApp(config);
        const messaging = firebase.messaging();
        messaging.requestPermission().then(function () {
            console.log("Permission given");
            return messaging.getToken();
        }, function () {
            console.log("Permission dennied")
        }).then(function (token) {
            console.log("my token", token);
        });
        messaging.onMessage(function (payload) {
            console.log('Message received :: online. ', payload);
            // ...
        });
    </script>


******************** firebase-messaging-sw.js file in the root directory to handle background notification***************
// Give the service worker access to Firebase Messaging.
// Note that you can only use Firebase Messaging here, other Firebase libraries
// are not available in the service worker.
importScripts('https://www.gstatic.com/firebasejs/4.8.1/firebase-app.js');
importScripts('https://www.gstatic.com/firebasejs/4.8.1/firebase-messaging.js');

// Initialize the Firebase app in the service worker by passing in the
// messagingSenderId.
firebase.initializeApp({
  'messagingSenderId': '94883233124'
});

// Retrieve an instance of Firebase Messaging so that it can handle background
// messages.
const messaging = firebase.messaging();


// Handle incoming messages. Called when:
// - a message is received while the app has focus
// - the user clicks on an app notification created by a service worker
//   `messaging.setBackgroundMessageHandler` handler.
messaging.setBackgroundMessageHandler(function(payload){
    const title = "Message from detroitech";
    const options = {
        body : payload.data.testMessage
    };
    return self.registration.showNotification(title,options);
});
messaging.setBackgroundMessageHandler(function (payload) {
    console.log('Handling background message ', payload);

    return self.registration.showNotification(payload.data.title, {
      body: payload.data.body,
      icon: payload.data.icon,
      tag: payload.data.tag,
      data: payload.data.link
    });
  });

  self.addEventListener('notificationclick', function(event) {
    event.notification.close();
    event.waitUntil(self.clients.openWindow(event.notification.data));
  });