let isPushEnabled = false;
let registration;
let pushButton;
window.addEventListener('load', function() {
    pushButton = document.querySelector('.js-push-toggle');
    if(pushButton !== undefined){
        pushButton.addEventListener('change', function() {
            document.querySelector('.label-text').textContent = this.checked ? 'Disable Push Messages' : 'Enable Push Messages';
            if (isPushEnabled) {
                unsubscribe();
            } else {
                subscribe();
            }
        });
    }
    // Check that service workers are supported, if so, progressively
    // enhance and add push messaging support, otherwise continue without it.
    if ('serviceWorker' in navigator) {
        navigator.serviceWorker.register('/service-worker.js')
            .then(initialiseState);
    } else {
        console.warn('Service workers aren\'t supported in this browser.');
    }
});

function initialiseState() {
    // Are Notifications supported in the service worker?
    if (!('showNotification' in ServiceWorkerRegistration.prototype)) {
        console.warn('Notifications aren\'t supported.');
        return;
    }

    // Check the current Notification permission.
    // If its denied, it's a permanent block until the
    // user changes the permission
    if (Notification.permission === 'denied') {
        console.warn('The user has blocked notifications.');
        return;
    }

    // Check if push messaging is supported
    if (!('PushManager' in window)) {
        console.warn('Push messaging isn\'t supported.');
        return;
    }

    // We need the service worker registration to check for a subscription
    navigator.serviceWorker.ready.then(function(serviceWorkerRegistration) {
        // Do we already have a push message subscription?
        registration = serviceWorkerRegistration;
        serviceWorkerRegistration.pushManager.getSubscription()
            .then(function(subscription) {
                // Enable any UI which subscribes / unsubscribes from
                // push messages.
                //var pushButton = document.querySelector('.js-push-toggle');
                pushButton.disabled = false;

                if (!subscription) {
                    // We aren't subscribed to push, so set UI
                    // to allow the user to enable push
                    return;
                }

                // Keep your server in sync with the latest subscriptionId
                //sendSubscriptionToServer(subscription);

                // Set your UI to show they have subscribed for
                // push messages
                document.querySelector('.label-text').text = 'Disable Push Messages';
                isPushEnabled = true;
            })
            .catch(function(err) {
                console.warn('Error during getSubscription()', err);
            });
    });
}

function subscribe() {
    // Disable the button so it can't be changed while
    // we process the permission request
    var pushButton = document.querySelector('.js-push-toggle');
    pushButton.disabled = true;

    navigator.serviceWorker.ready.then(function(serviceWorkerRegistration) {
        serviceWorkerRegistration.pushManager.subscribe()
            .then(function(subscription) {
                // The subscription was successful
                isPushEnabled = true;
                pushButton.textContent = 'Disable Push Messages';
                pushButton.disabled = false;

                // TODO: Send the subscription.endpoint to your server
                // and save it to send a push message at a later date
                return sendSubscriptionToServer(subscription);
            })
            .catch(function(e) {
                if (Notification.permission === 'denied') {
                    // The user denied the notification permission which
                    // means we failed to subscribe and the user will need
                    // to manually change the notification permission to
                    // subscribe to push messages
                    console.warn('Permission for Notifications was denied');
                    //pushButton.disabled = true;
                } else {
                    // A problem occurred with the subscription; common reasons
                    // include network errors, and lacking gcm_sender_id and/or
                    // gcm_user_visible_only in the manifest.
                    console.error('Unable to subscribe to push.', e);
                    pushButton.disabled = false;
                    document.querySelector('.label-text').text = 'Enable Push Messages';
                }
            });
    });
}

function unsubscribe() {
    var pushButton = document.querySelector('.js-push-toggle');
    pushButton.disabled = true;

    navigator.serviceWorker.ready.then(function(serviceWorkerRegistration) {
        // To unsubscribe from push messaging, you need get the
        // subscription object, which you can call unsubscribe() on.
        serviceWorkerRegistration.pushManager.getSubscription().then(
            function(pushSubscription) {
                // Check we have a subscription to unsubscribe
                if (!pushSubscription) {
                    // No subscription object, so set the state
                    // to allow the user to subscribe to push
                    isPushEnabled = false;
                    pushButton.disabled = false;
                    document.querySelector('.label-text').text = 'Enable Push Messages';
                    return;
                }

                var subscriptionId = pushSubscription.subscriptionId;
                // TODO: Make a request to your server to remove
                // the subscriptionId from your data store so you
                // don't attempt to send them push messages anymore

                // We have a subscription, so call unsubscribe on it
                pushSubscription.unsubscribe().then(function(successful) {
                    pushButton.disabled = false;
                    document.querySelector('.label-text').text = 'Enable Push Messages';
                    isPushEnabled = false;
                }).catch(function(e) {
                    // We failed to unsubscribe, this can lead to
                    // an unusual state, so may be best to remove
                    // the users data from your data store and
                    // inform the user that you have done so

                    console.log('Unsubscription error: ', e);
                    pushButton.disabled = false;
                    document.querySelector('.label-text').text = 'Enable Push Messages';
                });
            }).catch(function(e) {
            console.error('Error thrown while unsubscribing from push messaging.', e);
        });
    });
}