From 0b3ba49c779a1d131ac7413a7967bf435dab6efa Mon Sep 17 00:00:00 2001
From: Rafael Araujo Lehmkuhl <rafael.lehmkuhl93@gmail.com>
Date: Fri, 22 Nov 2024 13:26:42 -0300
Subject: [PATCH] event-tracking: Cache events captured while offline in a
 IndexedDB that persists between sessions

This way, if the user uses the application while offline and close it, without ever being online in that session, we still preserve the events and send them when possible in a following online usage.
---
 src/libs/external-telemetry/event-tracking.ts | 94 ++++++++++++++++---
 1 file changed, 82 insertions(+), 12 deletions(-)

diff --git a/src/libs/external-telemetry/event-tracking.ts b/src/libs/external-telemetry/event-tracking.ts
index bb8ac811f..9ef30ecd8 100644
--- a/src/libs/external-telemetry/event-tracking.ts
+++ b/src/libs/external-telemetry/event-tracking.ts
@@ -1,35 +1,105 @@
+import ky from 'ky'
+import localforage from 'localforage'
 import posthog from 'posthog-js'
 
+type EventPayload = {
+  /**
+   * The name of the event
+   */
+  eventName: string
+  /**
+   * The moment the event was captured (in milliseconds since epoch)
+   */
+  timestamp: number
+  /**
+   * Arbitrary properties to be recorded with the event
+   */
+  properties?: Record<string, unknown>
+}
+
 /**
- * PostHog client
+ *
  */
-class PostHog {
+class EventTracker {
+  static postHogApiUrl = 'https://us.i.posthog.com'
+  static postHogApiKey = 'phc_SfqVeZcpYHmhUn9NRizThxFxiI9fKqvjRjmBDB8ToRs'
   static posthog: ReturnType<typeof posthog.init> | undefined = undefined
+  eventTrackingQueue: LocalForage
 
   /**
-   * Initialize the PostHog client if not already initialized
+   * Initialize the event tracking system
    */
   constructor() {
-    if (!PostHog.posthog) {
-      PostHog.posthog = posthog.init('phc_SfqVeZcpYHmhUn9NRizThxFxiI9fKqvjRjmBDB8ToRs', {
-        api_host: 'https://us.i.posthog.com',
+    if (!EventTracker.posthog) {
+      EventTracker.posthog = posthog.init(EventTracker.postHogApiKey, {
+        api_host: EventTracker.postHogApiUrl,
         person_profiles: 'always', // Create profiles for anonymous users as well
       })
     }
+
+    if (!this.eventTrackingQueue) {
+      this.eventTrackingQueue = localforage.createInstance({
+        driver: localforage.INDEXEDDB,
+        name: 'Cockpit - Event-tracking Queue',
+        storeName: 'cockpit-event-tracking-queue',
+        version: 1.0,
+        description: 'Queue of events to be sent to the event tracking system.',
+      })
+    }
+
+    this.sendEvents()
   }
 
   /**
    * Capture an event
    * @param {string} eventName - The name of the event
-   * @param {Record<string, unknown>} properties - The properties of the event
+   * @param {Record<string, unknown>} eventProperties - The properties of the event
+   */
+  async capture(eventName: string, eventProperties?: Record<string, unknown>): Promise<void> {
+    const eventId = `${eventName}-${Date.now()}`
+    const eventPayload: EventPayload = {
+      eventName,
+      timestamp: Date.now(),
+      properties: eventProperties,
+    }
+    await this.eventTrackingQueue.setItem(eventId, eventPayload)
+    await this.sendEvents()
+  }
+
+  /**
+   * Send all events in the queue to the event tracking system
    */
-  capture(eventName: string, properties?: Record<string, unknown>): void {
-    if (!PostHog.posthog) {
-      throw new Error('PostHog client not initialized.')
+  async sendEvents(): Promise<void> {
+    const queuedEventsKeys = await this.eventTrackingQueue.keys()
+    const successfullySentEventsKeys: string[] = []
+
+    for (const eventId of queuedEventsKeys) {
+      const eventPayload = await this.eventTrackingQueue.getItem<EventPayload>(eventId)
+      if (!eventPayload) continue
+
+      try {
+        const body = {
+          api_key: EventTracker.postHogApiKey,
+          event: eventPayload.eventName,
+          properties: eventPayload.properties,
+          timestamp: eventPayload.timestamp,
+          distinct_id: EventTracker.posthog?.get_distinct_id(),
+        }
+
+        await ky.post(`${EventTracker.postHogApiUrl}/capture/`, { json: body, mode: 'no-cors', throwHttpErrors: false })
+        successfullySentEventsKeys.push(eventId)
+        console.log('Event sent successfully:', eventId)
+      } catch (error) {
+        console.error('Error sending event to PostHog:', error)
+        break
+      }
+    }
+
+    for (const eventId of successfullySentEventsKeys) {
+      await this.eventTrackingQueue.removeItem(eventId)
     }
-    PostHog.posthog.capture(eventName, properties)
   }
 }
 
-const eventTracker = new PostHog()
+const eventTracker = new EventTracker()
 export default eventTracker