// This optional code is used to register a service worker.
// register() is not called by default.

// 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 subsequent visits to a page, after all the
// existing tabs open on the page have been closed, since previously cached
// resources are updated in the background.

// To learn more about the benefits of this model and instructions on how to
// opt-in, read https://bit.ly/CRA-PWA

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 function register(config) {
  if (process.env.NODE_ENV === "production" && "serviceWorker" in navigator) {
    const publicUrl = new URL(process.env.PUBLIC_URL, window.location.href);
    if (publicUrl.origin !== window.location.origin) {
      return;
    }

    if (!isLocalhost) {
      // We only use offline pages on localhost
      return;
    }

    window.addEventListener("load", () => {
      registerValidSW(config);
    });
  }
}

function injectOfflinePage() {
  if ("serviceWorker" in navigator) {
    navigator.serviceWorker.getRegistration().then((registration) => {
      if (registration && registration.active) {
        registration.active.postMessage({ type: "CACHE_OFFLINE_PAGE" });
      }
    });
  }
}

function registerValidSW(config) {
  navigator.serviceWorker
    .register(`${process.env.PUBLIC_URL}/service-worker.js`)
    .then((registration) => {
      // Inject offline page caching after registration
      injectOfflinePage();
      registration.onupdatefound = () => {
        const installingWorker = registration.installing;
        if (installingWorker == null) {
          return;
        }
        installingWorker.onstatechange = () => {
          if (installingWorker.state === "installed") {
            if (navigator.serviceWorker.controller) {
              // At this point, the updated precached content has been fetched,
              // but the previous service worker will still serve the older
              // content until all client tabs are closed.
              console.log(
                "New content is available and will be used when all " +
                  "tabs for this page are closed. See https://bit.ly/CRA-PWA.",
              );

              // Execute callback
              if (config && config.onUpdate) {
                config.onUpdate(registration);
              }
            } 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.");

              // Execute callback
              if (config && config.onSuccess) {
                config.onSuccess(registration);
              }
            }
          }
        };
      };
    })
    .catch((error) => {
      console.error("Error during service worker registration:", error);
    });
}

// Add a message event listener to handle offline page caching in the service worker
if ("serviceWorker" in navigator) {
  navigator.serviceWorker.addEventListener("message", (event) => {
    if (event.data && event.data.type === "CACHE_OFFLINE_PAGE") {
      // No-op in client, handled in service worker file
    }
  });
}

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