/* eslint-disable no-console */
// 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.
		/^127(?:\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}$/.exec(window.location.hostname)
);

async function registerValidServiceWorker(swUrl: string) {
	await navigator.serviceWorker
		.register(swUrl)
		.then(registration => {
			registration.onupdatefound = () => {
				const installingWorker = registration.installing;
				if (installingWorker) {
					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.');
							} 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);
		});
}

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

export default async function registerServiceWorker() {
	await new Promise<void>((resolve, reject) => {
		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.toString());
			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', async () => {
				const swUrl = `${process.env.PUBLIC_URL!}/service-worker.js`;

				try {
					if (isLocalhost) {
						// This is running on localhost. Lets check if a service worker still exists or not.
						await checkValidServiceWorker(swUrl);
					} else {
						// Is not local host. Just register service worker
						await registerValidServiceWorker(swUrl);
					}
					resolve();
				} catch (e) {
					reject(e);
				}
			});
		}
	});
}

export async function unregister() {
	if ('serviceWorker' in navigator) {
		const registration = await navigator.serviceWorker.ready;
		return await registration.unregister();
	}
	return false;
}