Merge branch 'master' into project-map-link

Reviewed-on: trent_larson/kick-starter-for-time-pwa#60

.gitignore

@@ -1,13 +1,16 @@
 .DS_Store
 node_modules
 /dist
+signature.bin
+*.pem
+verified.txt
 
 *~
 # local env files
 .env.local
 .env.*.local
 
-# Log files
+# Log filesopenssl dgst -sha256 -verify public.pem -signature <(echo -n "$signature") "$signing_input"
 npm-debug.log*
 yarn-debug.log*
 yarn-error.log*

openssl_signing_console.rst

@@ -1,3 +1,7 @@
+Prerequisites:
+
+jq 
+
 You can create a JWT using a library or by encoding the header and payload base64Url and signing it with a secret using a ES256K algorithm. Here is an example of how you can create a JWT using the jq and openssl command line utilities:
 
 Here is an example of how you can use openssl to sign a JWT with the ES256K algorithm:

openssl_signing_console.sh

@@ -0,0 +1,25 @@
+#!/bin/bash
+
+openssl ecparam -name secp256k1 -genkey -noout -out private.pem
+openssl ec -in private.pem -pubout -out public.pem
+
+header='{"alg":"ES256K", "issuer": "", "typ":"JWT"}'
+
+payload='{"@context": "http://schema.org", "@type": "PlanAction", "identifier": "did:ethr:0xb86913f83A867b5Ef04902419614A6FF67466c12", "name": "Test", "description": "Me"}'
+
+header_b64=$(echo -n "$header" | jq -c -M . | tr -d '\n')
+payload_b64=$(echo -n "$payload" | jq -c -M . | tr -d '\n')
+
+signing_input="$header_b64.$payload_b64"
+
+echo -n "$signing_input" | openssl dgst -sha256 -sign private.pem -out signature.bin
+
+# Read binary signature from file and encode it to Base64 URL-Safe format
+signature_b64=$(base64 -w 0 < signature.bin | tr -d '=' | tr '+' '-' | tr '/' '_')
+
+# Construct the JWT
+jwt="$signing_input.$signature_b64"
+
+openssl dgst -sha256 -verify public.pem -signature signature.bin -out verified.txt <(echo -n "$signing_input")
+
+

package-lock.json

@@ -61,6 +61,7 @@
         "@types/three": "^0.152.1",
         "@typescript-eslint/eslint-plugin": "^5.61.0",
         "@typescript-eslint/parser": "^5.61.0",
+        "@vue-leaflet/vue-leaflet": "^0.10.1",
         "@vue/cli-plugin-babel": "~5.0.8",
         "@vue/cli-plugin-eslint": "~5.0.8",
         "@vue/cli-plugin-pwa": "~5.0.8",
@@ -74,6 +75,7 @@
         "eslint-config-prettier": "^8.8.0",
         "eslint-plugin-prettier": "^5.0.0-alpha.1",
         "eslint-plugin-vue": "^9.15.1",
+        "leaflet": "^1.9.4",
         "postcss": "^8.4.24",
         "prettier": "^3.0.0",
         "tailwindcss": "^3.3.2",
@@ -9639,6 +9641,24 @@
         "uint8arrays": "^3.0.0"
       }
     },
+    "node_modules/@vue-leaflet/vue-leaflet": {
+      "version": "0.10.1",
+      "resolved": "https://registry.npmjs.org/@vue-leaflet/vue-leaflet/-/vue-leaflet-0.10.1.tgz",
+      "integrity": "sha512-RNEDk8TbnwrJl8ujdbKgZRFygLCxd0aBcWLQ05q/pGv4+d0jamE3KXQgQBqGAteE1mbQsk3xoNcqqUgaIGfWVg==",
+      "dev": true,
+      "dependencies": {
+        "vue": "^3.2.25"
+      },
+      "peerDependencies": {
+        "@types/leaflet": "^1.5.7",
+        "leaflet": "^1.6.0"
+      },
+      "peerDependenciesMeta": {
+        "@types/leaflet": {
+          "optional": true
+        }
+      }
+    },
     "node_modules/@vue/babel-helper-vue-jsx-merge-props": {
       "version": "1.4.0",
       "resolved": "https://registry.npmmirror.com/@vue/babel-helper-vue-jsx-merge-props/-/babel-helper-vue-jsx-merge-props-1.4.0.tgz",
@@ -19067,6 +19087,12 @@
         "launch-editor": "^2.6.0"
       }
     },
+    "node_modules/leaflet": {
+      "version": "1.9.4",
+      "resolved": "https://registry.npmjs.org/leaflet/-/leaflet-1.9.4.tgz",
+      "integrity": "sha512-nxS1ynzJOmOlHp+iL3FyWqK89GtNL8U8rvlMOsQdTTssxZwCXh8N2NB3GDQOL+YR3XnWyZAxwQixURb+FA74PA==",
+      "dev": true
+    },
     "node_modules/leven": {
       "version": "3.1.0",
       "resolved": "https://registry.npmmirror.com/leven/-/leven-3.1.0.tgz",

package.json

@@ -61,6 +61,7 @@
     "@types/three": "^0.152.1",
     "@typescript-eslint/eslint-plugin": "^5.61.0",
     "@typescript-eslint/parser": "^5.61.0",
+    "@vue-leaflet/vue-leaflet": "^0.10.1",
     "@vue/cli-plugin-babel": "~5.0.8",
     "@vue/cli-plugin-eslint": "~5.0.8",
     "@vue/cli-plugin-pwa": "~5.0.8",
@@ -74,6 +75,7 @@
     "eslint-config-prettier": "^8.8.0",
     "eslint-plugin-prettier": "^5.0.0-alpha.1",
     "eslint-plugin-vue": "^9.15.1",
+    "leaflet": "^1.9.4",
     "postcss": "^8.4.24",
     "prettier": "^3.0.0",
     "tailwindcss": "^3.3.2",

project.task.yaml

@@ -2,24 +2,20 @@
 tasks:
 - test alerts on all pages -- or refactor to new "notify" (since AlertMessage refactoring may require a change, et. ContactQRScanShowView)
 - .2 bug - on contacts view, click on "to" & "from" and nothing happens
-- 01 add a location for a project via map pin :
-  - add with a "location" field containing this: { "geo":{ "@type":"GeoCoordinates", "latitude":40.883944, "longitude":-111.884787 } }
 - 40 notifications :
   - push, where we trigger a ServiceWorker(?) in the app to reach out and check for new data assignee:matthew
 
-- 01 add a location for a project via map pin
+- 01 add my bounding box(es) of interest for searches on Nearby part of Discovery page
-- 04 search by a bounding box for local projects (see API by clicking on "Nearby")
+- .5 search by a bounding box(s) of interest for local projects (see API by clicking on "Nearby")
 - 01 Replace Gifted/Give in ContactsView with GiftedDialog assignee:matthew
-- 02 Fix images on projectview - allow choice of image from a pallete of images or a url image (discovery page display also)
-  - SEE: https://github.com/dmester/jdenticon assignee:jose
 
 - 08 Scan QR code to import into contacts assignee:matthew
   - SEE: https://github.com/gruhn/vue-qrcode-reader
 
-- 01 Show pop-up or some message confirming that settings & contacts download has been initiated/finished assignee:matthew
+- 01 Show pop-up or some message confirming that settings & contacts download has been initiated/finished assignee:matthew assignee-group:ui
 
-- 01 Ensure each action sent to the server has a confirmation - eg registration (ie a toast something that dismisses after 5-10s)
+- 01 Ensure each action sent to the server has a confirmation - eg registration (ie a toast something that dismisses after 5-10s) assignee-group:ui
-  - SEE: https://github.com/emmanuelsw/notiwind assignee:jose
+  - SEE: https://github.com/emmanuelsw/notiwind assignee:jose assignee-group:ui
 
 - Home Feed & Quick Give screen :
   - 01 save the feed-viewed status in settings storage ("afterQuery")
@@ -33,10 +29,10 @@ tasks:
 - .5 add project ID to the URL, to make a project publicly-accessible
 - .5 remove edit from project page for projects owned by others
 - .5 fix where user 0 sees no txns from user 1 on contacts page but sees them on list page
-- .2 on ProjectViewView, show different messages for "to" and "from" sections if none exist
+- .2 on ProjectViewView, show different messages for "to" and "from" sections if none exist assignee-group:ui
-- .2 fix static icon to the right on project page (Matthew - I've made "Rotary" into issuer?) assignee:jose
+- .2 fix static icon to the right on project page (Matthew - I've made "Rotary" into issuer?) assignee:jose assignee-group:ui
 - .2 fix rate limit verbiage (with the new one-per-day allowance) assignee:trent
-- .2 move 'switch identity' to the advanced section
+- .2 move 'switch identity' to the advanced section assignee-group:ui
 - .1 remove the logic to exclude beforeId in list of plans after server has commit 26b25af605e715600d4f12b6416ed9fd7142d164
 - .2 in SeedBackupView, don't load the mnemonic and keep it in memory; only load it when they click "show"
 
@@ -45,10 +41,12 @@ tasks:
 - 04 allow user to download claims, mine + ones I can see about me from others
 - .5 change the derivation path, and regenerate test IDs
 - 02 allow user to create new DIDs from the same seed phrase (ie. increment derivation path)
-- .5 on ProjectView page, show immediate feedback when a gift is given (on list?) -- and consider the same for Home & Contacts pages
+- .5 on ProjectView page, show immediate feedback when a gift is given (on list?) -- and consider the same for Home & Contacts pages assignee-group:ui
-- .5 customize favicon
+- .5 customize favicon assignee-group:ui
 - .5 Do we want to combine first name & last name?
-- .2 Show a warning if both giver and recipient are the same (but still allow?)
+- .2 Show a warning if both giver and recipient are the same (but still allow?) assignee-group:ui
+- 01 Would it look better to shrink the buttons on many pages so they don't expand to the width of the screen? assignee-group:ui
+- .5 Display a more appealing confirmation on the map when erasing the marker assignee-group:ui
 
 - contacts v+ :
   - 01 Import all the non-sensitive data (ie. contacts & settings).
@@ -66,7 +64,6 @@ tasks:
   - 08 thorough testing for errors & edge cases
   - Turn off stats-world or ensure it's usable (eg. cannot zoom out too far and lose world, cannot screenshot).
   - Add disclaimers.
-  - Rename DB to TimeSafari.
   - Switch default server to the public server.
   - Deploy to a server.
   - Ensure public server has limits that work for group adoption.

src/constants/app.ts

@@ -5,7 +5,7 @@ export enum AppString {
   APP_NAME = "Kick-Start with Time",
 
   PROD_ENDORSER_API_SERVER = "https://api.endorser.ch",
-  TEST_ENDORSER_API_SERVER = "https://test.endorser.ch:8000",
+  TEST_ENDORSER_API_SERVER = "https://test-api.endorser.ch",
   LOCAL_ENDORSER_API_SERVER = "http://localhost:3000",
 
   DEFAULT_ENDORSER_API_SERVER = TEST_ENDORSER_API_SERVER,

src/main.ts

@@ -35,6 +35,7 @@ import {
   faGift,
   faHand,
   faHouseChimney,
+  faLocationDot,
   faLongArrowAltLeft,
   faLongArrowAltRight,
   faMagnifyingGlass,
@@ -80,6 +81,7 @@ library.add(
   faGift,
   faHand,
   faHouseChimney,
+  faLocationDot,
   faLongArrowAltLeft,
   faLongArrowAltRight,
   faMagnifyingGlass,

src/views/HomeView.vue

@@ -111,7 +111,7 @@
 
     <div class="mb-8">
       <h2 class="text-xl font-bold">Quick Action</h2>
-      <p class="mb-4">Show appreciation to a contact:</p>
+      <p class="mb-4">Record a gift from a contact:</p>
 
       <ul class="grid grid-cols-4 gap-x-3 gap-y-5 text-center mb-5">
         <li @click="openDialog()">

src/views/NewEditProjectView.vue

@@ -39,6 +39,40 @@
       {{ description.length }}/500 max. characters
     </div>
 
+    <div class="flex items-center mb-4">
+      <input
+        type="checkbox"
+        class="mr-2"
+        v-model="includeLocation"
+        @change="includeLocation = true"
+      />
+      <label for="includeLocation">Include Location</label>
+    </div>
+    <div v-if="includeLocation" style="height: 600px; width: 800px">
+      <l-map
+        ref="map"
+        v-model:zoom="zoom"
+        :center="[0, 0]"
+        @click="
+          (event) => {
+            latitude = event.latlng.lat;
+            longitude = event.latlng.lng;
+          }
+        "
+      >
+        <l-tile-layer
+          url="https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png"
+          layer-type="base"
+          name="OpenStreetMap"
+        />
+        <l-marker
+          v-if="latitude || longitude"
+          :lat-lng="[latitude, longitude]"
+          @click="maybeEraseLatLong()"
+        />
+      </l-map>
+    </div>
+
     <div class="mt-8">
       <button
         :disabled="isHiddenSave"
@@ -71,9 +105,11 @@
 </template>
 
 <script lang="ts">
+import "leaflet/dist/leaflet.css";
 import { AxiosError } from "axios";
 import * as didJwt from "did-jwt";
 import { Component, Vue } from "vue-facing-decorator";
+import { LMap, LMarker, LTileLayer } from "@vue-leaflet/vue-leaflet";
 
 import { accountsDB, db } from "@/db";
 import { MASTER_SETTINGS_KEY } from "@/db/tables/settings";
@@ -83,17 +119,21 @@ import { IIdentifier } from "@veramo/core";
 import AlertMessage from "@/components/AlertMessage";
 
 @Component({
-  components: { AlertMessage },
+  components: { AlertMessage, LMap, LMarker, LTileLayer },
 })
 export default class NewEditProjectView extends Vue {
   activeDid = "";
-  apiServer = "";
-  projectName = "";
-  description = "";
-  errorMessage = "";
-  numAccounts = 0;
   alertTitle = "";
   alertMessage = "";
+  apiServer = "";
+  description = "";
+  errorMessage = "";
+  includeLocation = false;
+  latitude = 0;
+  longitude = 0;
+  numAccounts = 0;
+  projectName = "";
+  zoom = 2;
 
   async beforeCreate() {
     await accountsDB.open();
@@ -185,6 +225,15 @@ export default class NewEditProjectView extends Vue {
     if (this.projectId) {
       vcClaim.identifier = this.projectId;
     }
+    if (this.includeLocation) {
+      vcClaim.location = {
+        geo: {
+          "@type": "GeoCoordinates",
+          latitude: this.latitude,
+          longitude: this.longitude,
+        },
+      };
+    }
     // Make a payload for the claim
     const vcPayload = {
       vc: {
@@ -299,6 +348,14 @@ export default class NewEditProjectView extends Vue {
     }
   }
 
+  public maybeEraseLatLong() {
+    if (window.confirm("Are you sure you don't want to mark a location?")) {
+      this.latitude = 0;
+      this.longitude = 0;
+      this.includeLocation = false;
+    }
+  }
+
   public onCancelClick() {
     this.$router.back();
   }

src/views/ProjectViewView.vue

@@ -39,6 +39,16 @@
                 <fa icon="calendar" class="fa-fw text-slate-400"></fa>
                 {{ timeSince }}
               </div>
+              <div v-if="latitude || longitude">
+                <fa icon="location-dot" class="fa-fw text-slate-400"></fa>
+                <a
+                  :href="getOpenStreetMapUrl()"
+                  target="_blank"
+                  class="underline"
+                >
+                  Map View
+                </a>
+              </div>
             </div>
           </div>
         </div>
@@ -231,6 +241,8 @@ export default class ProjectViewView extends Vue {
   expanded = false;
   givesToThis: Array<GiveServerRecord> = [];
   givesByThis: Array<GiveServerRecord> = [];
+  latitude = 0;
+  longitude = 0;
   name = "";
   issuer = "";
   projectId = localStorage.getItem("projectId") || ""; // handle ID
@@ -326,6 +338,8 @@ export default class ProjectViewView extends Vue {
         this.name = resp.data.claim?.name || "(no name)";
         this.description = resp.data.claim?.description || "(no description)";
         this.truncatedDesc = this.description.slice(0, this.truncateLength);
+        this.latitude = resp.data.claim?.location?.geo?.latitude || 0;
+        this.longitude = resp.data.claim?.location?.geo?.longitude || 0;
       } else if (resp.status === 404) {
         // actually, axios throws an error so we never get here
         this.$notify(
@@ -441,6 +455,20 @@ export default class ProjectViewView extends Vue {
     this.$refs.customDialog.open(contact);
   }
 
+  getOpenStreetMapUrl() {
+    // Google URL is https://maps.google.com/?q=LAT,LONG
+    return (
+      "https://www.openstreetmap.org/?mlat=" +
+      this.latitude +
+      "&mlon=" +
+      this.longitude +
+      "#map=15/" +
+      this.latitude +
+      "/" +
+      this.longitude
+    );
+  }
+
   handleDialogResult(result) {
     if (result.action === "confirm") {
       return new Promise((resolve) => {

web-push.md

@@ -0,0 +1,316 @@
+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.
+
+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. FCM also may fit in this category if the SERVICE
+has an API key from FCM.]
+
+The workflow works like this:
+
+BROWSER visits a website which hosts a SERVICE.
+
+The SERVICE asks BROWSER for its permission to subscribe to messages coming
+from the SERVICE.
+
+The SERVICE will provide context and obtain explicit permission before prompting
+for notification permission:
+
+In order 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) {
+      resolve(result);
+    });
+
+    if (permissionResult) {
+      permissionResult.then(resolve, reject);
+    }
+  }).then(function(permissionResult) {
+    if (permissionResult !== 'granted') {
+      throw new Error("We weren't granted permission.");
+    }
+    return permissionResult;
+  });
+}
+```
+
+The Notification.permission property indicates the permission level for the
+current session and returns one of the following string values:
+
+    'granted': The user has granted permission for notifications.
+    'denied': The user has denied permission for notifications.
+    'default': The user has not made a choice yet.
+
+Once the user has granted 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.
+
+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 of execution 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 file.
+
+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 more than one server workers each needs 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);
+
+  const title = 'Push message';
+  const body = 'The message body';
+  const icon = '/images/icon-192x192.png';
+  const tag = 'simple-push-demo-notification-tag';
+
+  event.waitUntil(
+    self.registration.showNotification(title, {
+      body: body,
+      icon: icon,
+      tag: tag
+    })
+  );
+});
+```
+
+
+vue.config.js
+```
+module.exports = {
+  pwa: {
+    workboxOptions: {
+      importScripts: ['sw-dev.ts']
+    }
+  }
+}
+```
+
+Once we have the service worker registered and the ServiceWorkerRegistration is
+returned, we then have access to a `pushManager` property object.  This property
+allows us to continue with the web push work flow.
+
+In the next step, BROWSER requests a data structure from SERVICE called a VAPID
+(Voluntary Application Server Identification) which is the public key from a
+key-pair.
+
+The VAPID is a specification used to identify the application server (i.e. the
+SERVICE server) that is sending push messages through a push PROVIDER. It's an
+authentication mechanism that allows the server to demonstrate its identity to
+the push PROVIDER, by use of a public and private key pair. These keys are used
+by the SERVICE in encrypting messages being sent to the BROWSER, as well as
+being used by the BROWSER in decrypting the messages coming from the SERVICE.
+
+The VAPID (Voluntary Application Server Identification) key provides more
+security and authenticity for web push notifications in the following ways:
+
+Identifying the Application Server:
+    
+        The VAPID key is used to identify the application server that is sending
+	the push notifications. This ensures that the push notifications are
+	authentic and not sent by a malicious third party.
+	
+Encrypting the Messages:
+    
+        The VAPID key is used to sign the push notifications sent by the
+	application server, ensuring that they are not tampered with during
+	transmission. This provides an additional layer of security and
+	authenticity for the push notifications.
+
+Adding Contact Information:
+
+    The VAPID key allows a web application to add contact information to
+    the push messages sent to the browser push service. This enables the
+    push service to contact the application server in case of need or
+    provide additional debug information about the push messages.
+
+Improving Delivery Rates:
+
+    Using the VAPID key can help improve the overall performance of web push
+    notifications, specifically improving delivery rates. By streamlining the
+    delivery process, the chance of delivery errors along the way is lessened.
+
+If the BROWSER accepts and grants permission to subscribe to receiving from the
+SERVICE Web Push messages, then the BROWSER makes a subscription request to
+PROVIDER which creates and stores a special URL for that BROWSER.
+
+Here's a bit of code describing the above process:
+
+```
+// b64 is the VAPID
+b64 = 'BEl62iUYgUivxIkv69yViEuiBIa-Ib9-SkvMeAtA3LFgDzkrxZJjSgSnfckjBJuBkr3qBUYIHBQFLXYp5Nksh8U';
+const applicationServerKey = urlBase64ToUint8Array(b64);
+const options: PushSubscriptionOptions = {
+  userVisibleOnly: true,
+  applicationServerKey: applicationServerKey
+};
+
+registration.pushManager.subscribe(options)
+  .then(function(subscription) {
+    console.log('Push subscription successful:', subscription);
+  })
+  .catch(function(error) {
+    console.error('Push subscription failed:', error);
+  });
+```
+
+In this example, the `applicationServerKey` variable contains the VAPID public
+key, which is converted to a `Uint8Array` using a function such as this:
+
+```
+export function toUint8Array(base64String: string, atobFn: typeof atob): Uint8Array {
+	const padding = "=".repeat((4 - (base64String.length % 4)) % 4);
+	const base64 = (base64String + padding).replace(/-/g, "+").replace(/_/g, "/");
+
+	const rawData = atobFn(base64);
+	const outputArray = new Uint8Array(rawData.length);
+
+	for (let i = 0; i < rawData.length; ++i) {
+		outputArray[i] = rawData.charCodeAt(i);
+	}
+	return outputArray;
+}
+```
+
+The options object is of type `PushSubscriptionOptions`, which includes the
+`userVisibleOnly` and `applicationServerKey` (ie VAPID public key) properties.
+
+    options: An object that contains the options used for creating the
+    subscription. This object itself has the following sub-properties:
+    
+      applicationServerKey: A public key your push service uses for application
+      server identification. This is normally a Uint8Array.
+    
+      userVisibleOnly: A boolean value indicating that the push messages that
+      are sent should be made visible to the user through a notification.
+      This is often set to true.
+
+The subscribe() method returns a `Promise` that resolves to a `PushSubscription`
+object containing details of the subscription, such as the endpoint URL and the
+public key.  The returned data would have a form like this:
+
+    {
+      "endpoint": "https://some.pushservice.com/some/unique/identifier",
+      "expirationTime": null,
+      "keys": {
+        "p256dh": "some_base64_encoded_string",
+        "auth": "some_other_base64_encoded_string"
+      }
+    }
+
+    endpoint: A string representing the endpoint URL for the push service. This
+    URL is essentially the push service address to which the push message would
+    be sent for this particular subscription.
+
+    expirationTime: A DOMHighResTimeStamp (which is basically a number or null)
+    representing the subscription's expiration time in milliseconds since
+    01 January, 1970 UTC. This can be null if the subscription never expires.
+
+The BROWSER will, internally, then use that URL to check for incoming messages
+by way of the service worker we described earlier. The BROWSER also sends this
+URL back to SERVICE which will use that URL to send messages to the BROWSER via
+the PROVIDER.
+
+Ultimately, the actual internal process of receiving messages varies from BROWSER
+to BROWSER. Approaches vary from long-polling HTTP connections to WebSockets. A
+lot of handwaving and voodoo magic. The bottom line is that the BROWSER itself
+manages the connection to the PROVIDER whilst the SERVICE must send messages
+via the PROVIDER so that they reach the BROWSER service worker.
+
+Just to remind us that in our service worker our code for receiving messages
+will look something like this:
+
+```
+self.addEventListener('push', function(event: PushEvent) {
+  console.log('Received a push message', event);
+
+  const title = 'Push message';
+  const body = 'The message body';
+  const icon = '/images/icon-192x192.png';
+  const tag = 'simple-push-demo-notification-tag';
+
+  event.waitUntil(
+    self.registration.showNotification(title, {
+      body: body,
+      icon: icon,
+      tag: tag
+    })
+  );
+});
+```
+
+
+Now to address the issue of receiving notification messages on mobile devices.
+It should be noted that Web Push messages are only received when BROWSER is
+open, except in the cases of Chrome and Firefox mobile BROWSERS. In iOS, the
+mobile application (in our case a PWA) must be added to the Home Screen and
+permissions must be explicitly granted that allow the application to receive
+push notifications. Further, with an iOS device the user must enable wake on
+notification to have their device light-up when it receives a notification
+(https://support.apple.com/enus/HT208081).
+
+So what about #4? - The INTERMEDIARY. Well, It is possible under very special
+circumstances to create your own Web Push PROVIDER. The only case I've found so
+far relates to making an Android Custom ROM. (An Android Custom ROM is a
+customized version of the Android Operating System.) There are open source
+IMTERMEDIARY products such as UnifiedPush (https://unifiedpush.org/) which can
+fulfill this role. If you are using iOS you are not permitted to make or use
+your own custom Web Push PROVIDER. Apple will never allow anyone to do that.
+Apple has none of its own.
+
+It is, however, possible to have a sort of proxy working between your SERVICE
+and FCM (or iOS). Services that mash up various Push notification services (like
+OneSignal) can perform in the role of such proxies.
+
+#4 -The INTERMEDIARY- doesn't appear to be anything we should be spending our
+time on.