// 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.');

            } 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();

    });

  }

}