Add service worker and subscriptions controllers

app/javascript/controllers/notifications.js

@@ -0,0 +1,106 @@
+import { Controller } from "@hotwired/stimulus"
+import { post } from "@rails/request.js"
+import { pageIsTurboPreview } from "helpers/turbo_helpers"
+import { onNextEventLoopTick } from "helpers/timing_helpers"
+
+console.log("Notifications controller module loaded")
+
+export default class extends Controller {
+  static values = { subscriptionsUrl: String }
+
+  async connect() {
+    console.log("connected")
+    if (!pageIsTurboPreview()) {
+      if (window.notificationsPreviouslyReady) {
+        onNextEventLoopTick(() => this.dispatch("ready"))
+      } else {
+        const firstTimeReady = await this.isEnabled()
+
+        if (firstTimeReady) {
+          onNextEventLoopTick(() => this.dispatch("ready"))
+          window.notificationsPreviouslyReady = true
+        }
+      }
+    }
+  }
+
+  async attemptToSubscribe() {
+    console.log("attemptToSubscribe")
+    if (this.#allowed) {
+      const registration = await this.#serviceWorkerRegistration || await this.#registerServiceWorker()
+
+      switch(Notification.permission) {
+        case "denied":  { break }
+        case "granted": { this.#subscribe(registration); break }
+        case "default": { this.#requestPermissionAndSubscribe(registration) }
+      }
+    }
+  }
+
+  async isEnabled() {
+    if (this.#allowed) {
+      const registration = await this.#serviceWorkerRegistration
+      const existingSubscription = await registration?.pushManager?.getSubscription()
+
+      return Notification.permission == "granted" && registration && existingSubscription
+    } else {
+      return false
+    }
+  }
+
+  get #allowed() {
+    return navigator.serviceWorker && window.Notification
+  }
+
+  get #serviceWorkerRegistration() {
+    return navigator.serviceWorker.getRegistration(window.location.host)
+  }
+
+  #registerServiceWorker() {
+    return navigator.serviceWorker.register("/service-worker.js")
+  }
+
+  async #subscribe(registration) {
+    registration.pushManager
+      .subscribe({ userVisibleOnly: true, applicationServerKey: this.#vapidPublicKey })
+      .then(subscription => {
+        this.#syncPushSubscription(subscription)
+        this.dispatch("ready")
+      })
+  }
+
+  async #syncPushSubscription(subscription) {
+    const response = await post(this.subscriptionsUrlValue, { body: this.#extractJsonPayloadAsString(subscription), responseKind: "turbo-stream" })
+    if (!response.ok) subscription.unsubscribe()
+  }
+
+  async #requestPermissionAndSubscribe(registration) {
+    const permission = await Notification.requestPermission()
+    if (permission === "granted") this.#subscribe(registration)
+  }
+
+  get #vapidPublicKey() {
+    const encodedVapidPublicKey = document.querySelector('meta[name="vapid-public-key"]').content
+    return this.#urlBase64ToUint8Array(encodedVapidPublicKey)
+  }
+
+  #extractJsonPayloadAsString(subscription) {
+    const { endpoint, keys: { p256dh, auth } } = subscription.toJSON()
+    return JSON.stringify({ push_subscription: { endpoint, p256dh_key: p256dh, auth_key: auth } })
+  }
+
+  // VAPID public key comes encoded as base64 but service worker registration needs it as a Uint8Array
+  #urlBase64ToUint8Array(base64String) {
+    const padding = "=".repeat((4 - base64String.length % 4) % 4)
+    const base64 = (base64String + padding).replace(/-/g, "+").replace(/_/g, "/")
+
+    const rawData = window.atob(base64)
+    const outputArray = new Uint8Array(rawData.length)
+
+    for (let i = 0; i < rawData.length; ++i) {
+      outputArray[i] = rawData.charCodeAt(i)
+    }
+
+    return outputArray
+  }
+}