discourse/app/assets/javascripts/service-worker.js.erb

'use strict';

importScripts("<%= ::UrlHelper.absolute("/javascripts/workbox/workbox-sw.js") %>");

workbox.setConfig({
  modulePathPrefix: "<%= ::UrlHelper.absolute("/javascripts/workbox") %>",
  debug: false
});

const cacheVersion = "1";

// Cache all GET requests, so Discourse can be used while offline
workbox.routing.registerRoute(
  new RegExp('.*?'), // Matches all, GET is implicit
  new workbox.strategies.NetworkFirst({ // This will only use the cache when a network request fails
    cacheName: "discourse-" + cacheVersion,
    plugins: [
      new workbox.expiration.Plugin({
        maxAgeSeconds: 7* 24 * 60 * 60, // 7 days
        maxEntries: 500,
        purgeOnQuotaError: true, // safe to automatically delete if exceeding the available storage
      }),
    ],
  })
);

const idleThresholdTime = 1000 * 10; // 10 seconds
var lastAction = -1;

function isIdle() {
  return lastAction + idleThresholdTime < Date.now();
}

function showNotification(title, body, icon, badge, tag, baseUrl, url) {
  var notificationOptions = {
    body: body,
    icon: icon,
    badge: badge,
    data: { url: url, baseUrl: baseUrl },
    tag: tag
  }

  return self.registration.showNotification(title, notificationOptions);
}

self.addEventListener('push', function(event) {
  var payload = event.data.json();
  if(!isIdle() && payload.hide_when_active) {
    return false;
  }

  event.waitUntil(
    self.registration.getNotifications({ tag: payload.tag }).then(function(notifications) {
      if (notifications && notifications.length > 0) {
        notifications.forEach(function(notification) {
          notification.close();
        });
      }

      return showNotification(payload.title, payload.body, payload.icon, payload.badge, payload.tag, payload.base_url, payload.url);
    })
  );
});

self.addEventListener('notificationclick', function(event) {
  // Android doesn't close the notification when you click on it
  // See: http://crbug.com/463146
  event.notification.close();
  var url = event.notification.data.url;
  var baseUrl = event.notification.data.baseUrl;

  // This looks to see if the current window is already open and
  // focuses if it is
  event.waitUntil(
    clients.matchAll({ type: "window" })
      .then(function(clientList) {
        var reusedClientWindow = clientList.some(function(client) {
          if (client.url === baseUrl + url && 'focus' in client) {
            client.focus();
            return true;
          }

          if ('postMessage' in client && 'focus' in client) {
            client.focus();
            client.postMessage({ url: url });
            return true;
          }
          return false;
        });

        if (!reusedClientWindow && clients.openWindow) return clients.openWindow(baseUrl + url);
      })
  );
});

self.addEventListener('message', function(event) {
  if('lastAction' in event.data){
    lastAction = event.data.lastAction;
  }});
<% DiscoursePluginRegistry.service_workers.each do |js| %>
<%=raw "#{File.read(js)}" %>
<% end %>