Updates to web push guide

web-push.md

@@ -1,19 +1,19 @@
 Web Push notifications is a web browser messaging protocol defined by the W3C.
 
-Discussions of this interesting technology are clouded because of a terminological
-morass.
+Discussions of this interesting technology are clouded because of a
+terminological morass.
 
 To understand how Web Push operates, we need to observe that are three (and
 potentially four) parties involved. These are:
 
 1) The user's web browser. Let's call that BROWSER
-2) The Web Push Service Provider which is operated by the organization controlling the
-web browser's source code. Here named PROVIDER. An example of a PROVIDER is
-FCM (Firebase Cloud Messaging) which is owned by Google.
-3) The Web Application that a user is visiting from their web browser. Let's call this the
-SERVICE (short for Web Push application service)
-[4) A Custom Web Push Intermediary Service, either third party or self-hosted. Called
-INTERMEDIARY here.]
+2) The Web Push Service Provider which is operated by the organization
+controlling the web browser's source code. Here named PROVIDER. An example of a
+PROVIDER is FCM (Firebase Cloud Messaging) which is owned by Google.
+3) The Web Application that a user is visiting from their web browser. Let's
+call this the SERVICE (short for Web Push application service)
+[4) A Custom Web Push Intermediary Service, either third party or self-hosted.
+Called INTERMEDIARY here.]
 
 The workflow works like this:
 
@@ -22,13 +22,18 @@ BROWSER visits a website which has a SERVICE.
 The SERVICE asks BROWSER for its permission to subscribe to messages coming
 from the SERVICE.
 
-Provide context and obtain explicit permission before prompting for notification permission:
-It is recommended to set up to a two-step opt-in process where the user is first presented
-with a pre-permission dialog box that explains what the notifications are for and why they
-are useful. This may help reduce the possibility of users clicking "don't allow.
+The SERVICE will provide context and obtain explicit permission before prompting
+for notification permission:
 
-In Typescript, we can activate a browser's permission dialogue in this manner:
+In orer to provide this context and explict permission a two-step opt-in process
+where the user is first presented with a pre-permission dialog box that explains
+what the notifications are for and why they are useful. This may help reduce the
+possibility of users clicking "don't allow.
 
+Now, to explain what happens in Typescript, we can activate a browser's
+permission dialogue in this manner:
+
+```
 function askPermission(): Promise<NotificationPermission> {
   return new Promise(function(resolve, reject) {
     const permissionResult = Notification.requestPermission(function(result) {
@@ -45,14 +50,54 @@ function askPermission(): Promise<NotificationPermission> {
     return permissionResult;
   });
 }
+```
+
+If the user grants permission, the client application registers a service worker
+using the `ServiceWorkerRegistration` API.
+
+The `ServiceWorkerRegistration` API is accessible via the browser's `navigator`
+object and the `navigator.serviceWorker` child object and ultimately directly
+accessible via the navigator.serviceWorker.register method which also creates
+the service worker or the navigator.serviceWorker.getRegistration method.
+
+Once you have a `ServiceWorkerRegistration` object, that object will provide a
+child object named `pushManager` through which subscription and management of
+subscriptions may be done.
 
-If the user grants permission, the client application registers a service worker using
-the ServiceWorkerRegistration API.
+Let's go through the `register` method first:
 
+```
+navigator.serviceWorker.register('sw.js', { scope: '/' })
+  .then(function(registration) {
+    console.log('Service worker registered successfully:', registration);
+  })
+  .catch(function(error) {
+    console.log('Service worker registration failed:', error);
+  });
+```
+
+The `sw.js` file contains the logic for what a service worker should do.
+It executes in a separate thread from the web page but provides a means
+of communicating between itself and the web page via messages.
+
+Note that there is a scope can specify what network requests it may
+intercept.
+
+The Vue project already has its own service worker but it is possible to
+create multiple service worker files by registering them on different scopes.
+
+It is useful architecturally to specify a separate server worker.
+
+In the case of web push, the path of the scope only has reference to the domain
+of the service worker and no relationship to the pathing for the web push
+server.  In order to specify different server workers they need to be on
+different scope paths!
 
 Here's a version which can be used for testing locally.  Note there can be
 caching issues in your browser!  Incognito is highly recommended.
 
+sw-dev.ts
+
 self.addEventListener('push', function(event: PushEvent) {
   console.log('Received a push message', event);