<script src="https://www.gstatic.com/firebasejs/4.0.0/firebase.js"></script>

<script type="text/javascript">
    /* global _config */

    {literal}
    firebase.initializeApp(_config['firebase_config']);

    // Retrieve Firebase Messaging object.
    const messaging = firebase.messaging();

    // Callback fired if Instance ID token is updated.
    messaging.onTokenRefresh(function () {
        messaging.getToken().then(function (refreshed_token) {
            console.log('[Firepush] token refreshed.');

            // Indicate that the new Instance ID token has not yet been sent to the app server.
            set_token_sent_to_server(false);

            // Send Instance ID token to app server.
            send_token_to_server(refreshed_token);

        }).catch(function (err) {
            console.log('[Firepush] unable to retrieve refreshed token ', err);
        });
    });

    if ('serviceWorker' in navigator) {
        navigator.serviceWorker.register(_config['worker_link']).then(function (registration) {
            messaging.useServiceWorker(registration);
            console.log('[Firepush] ServiceWorker registration successful with scope: ', registration.scope);
        }).catch(function (err) {
            console.log('[Firepush] ServiceWorker registration failed: ', err);
        });
    }
    {/literal}
</script>