registerServiceWorker.js

import React from 'react';
import ReactDOM from 'react-dom';

function NewContentNotification() {
	return (
		<div
			style={{
				position: 'fixed',
				bottom: 0,
				cursor: 'pointer',
				width: '100%'
			}}
			className="notification is-info"
			onClick={() => {
				window.location.reload();
			}}
		>
			A new version of Checkins is available. Tap here to refresh.
		</div>
	);
}

// In production, we register a service worker to serve assets from local cache.

// This lets the app load faster on subsequent visits in production, and gives
// it offline capabilities. However, it also means that developers (and users)
// will only see deployed updates on the "N+1" visit to a page, since previously
// cached resources are updated in the background.

// To learn more about the benefits of this model, read https://goo.gl/KwvDNy.
// This link also includes instructions on opting out of this behavior.

const isLocalhost = Boolean(
	window.location.hostname === 'localhost' ||
		// [::1] is the IPv6 localhost address.
		window.location.hostname === '[::1]' ||
		// 127.0.0.1/8 is considered localhost for IPv4.
		window.location.hostname.match(
			/^127(?:\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}$/
		)
);

export default function register() {
	if (process.env.NODE_ENV === 'production' && 'serviceWorker' in navigator) {
		// The URL constructor is available in all browsers that support SW.
		const publicUrl = new URL(process.env.PUBLIC_URL, window.location);
		if (publicUrl.origin !== window.location.origin) {
			// Our service worker won't work if PUBLIC_URL is on a different origin
			// from what our page is served on. This might happen if a CDN is used to
			// serve assets; see https://github.com/facebookincubator/create-react-app/issues/2374
			return;
		}

		window.addEventListener('load', () => {
			const swUrl = `${process.env.PUBLIC_URL}/service-worker.js`;

			if (isLocalhost) {
				// This is running on localhost. Lets check if a service worker still exists or not.
				checkValidServiceWorker(swUrl);

				// Add some additional logging to localhost, pointing developers to the
				// service worker/PWA documentation.
				navigator.serviceWorker.ready.then(() => {
					console.log(
						'This web app is being served cache-first by a service ' +
							'worker. To learn more, visit https://goo.gl/SC7cgQ'
					);
				});
			} else {
				// Is not local host. Just register service worker
				registerValidSW(swUrl);
			}
		});
	}
}

function registerValidSW(swUrl) {
	navigator.serviceWorker
		.register(swUrl)
		.then(registration => {
			registration.onupdatefound = () => {
				const installingWorker = registration.installing;
				installingWorker.onstatechange = () => {
					if (installingWorker.state === 'installed') {
						if (navigator.serviceWorker.controller) {
							// At this point, the old content will have been purged and
							// the fresh content will have been added to the cache.
							// It's the perfect time to display a "New content is
							// available; please refresh." message in your web app.
							console.log('New content is available; please refresh.');
							ReactDOM.render(
								<NewContentNotification />,
								document.getElementById('service-worker')
							);
						} else {
							// At this point, everything has been precached.
							// It's the perfect time to display a
							// "Content is cached for offline use." message.
							console.log('Content is cached for offline use.');
						}
					}
				};
			};
		})
		.catch(error => {
			console.error('Error during service worker registration:', error);
		});
}

function checkValidServiceWorker(swUrl) {
	// Check if the service worker can be found. If it can't reload the page.
	fetch(swUrl)
		.then(response => {
			// Ensure service worker exists, and that we really are getting a JS file.
			if (
				response.status === 404 ||
				response.headers.get('content-type').indexOf('javascript') === -1
			) {
				// No service worker found. Probably a different app. Reload the page.
				navigator.serviceWorker.ready.then(registration => {
					registration.unregister().then(() => {
						window.location.reload();
					});
				});
			} else {
				// Service worker found. Proceed as normal.
				registerValidSW(swUrl);
			}
		})
		.catch(() => {
			console.log(
				'No internet connection found. App is running in offline mode.'
			);
		});
}

export function unregister() {
	if ('serviceWorker' in navigator) {
		navigator.serviceWorker.ready.then(registration => {
			registration.unregister();
		});
	}
}