From 2b58e4f6ced4510507503258f7449bfb78a03f2f Mon Sep 17 00:00:00 2001
From: Satindar Dhillon <satindar@gmail.com>
Date: Wed, 15 Jun 2022 11:33:03 -0700
Subject: [PATCH] add event tracking to background tasks

---
 apple/OmnivoreKit/Sources/App/Services.swift  | 40 +++++++++++++++----
 .../FetchLinkedItemsBackgroundTask.swift      |  9 ++++-
 .../Utils/EventTracking/TrackableEvents.swift | 16 ++++++++
 3 files changed, 55 insertions(+), 10 deletions(-)

diff --git a/apple/OmnivoreKit/Sources/App/Services.swift b/apple/OmnivoreKit/Sources/App/Services.swift
index 1a8d6ad59..cc394380f 100644
--- a/apple/OmnivoreKit/Sources/App/Services.swift
+++ b/apple/OmnivoreKit/Sources/App/Services.swift
@@ -47,35 +47,59 @@ public final class Services {
     }
 
     static func performBackgroundFetch(task: BGAppRefreshTask) {
+      let startTime = Date()
       Services.logger.debug("starting background fetch")
       scheduleBackgroundFetch()
       let services = Services()
 
       task.expirationHandler = {
-        EventTracker.trackForDebugging("background fetch expiration handler called")
+        EventTracker.track(
+          .backgroundFetch(
+            jobStatus: .timeExpired,
+            itemCount: 0,
+            secondsElapsed: Int(startTime.timeIntervalSinceNow)
+          )
+        )
         logger.debug("handling background fetch expiration")
       }
 
       guard services.authenticator.hasValidAuthToken else {
-        EventTracker.trackForDebugging("background fetch failed: user does not have a valid auth token")
-        Services.logger.debug("background fetch failed: user does not habe a valid auth token")
+        EventTracker.track(
+          .backgroundFetch(
+            jobStatus: .authFailure,
+            itemCount: 0,
+            secondsElapsed: Int(startTime.timeIntervalSinceNow)
+          )
+        )
         task.setTaskCompleted(success: false)
         return
       }
 
       Task {
         do {
-          try await services.dataService.fetchLinkedItemsBackgroundTask()
-          logger.debug("fetch complete")
-          EventTracker.trackForDebugging("background fetch task completed successfully")
+          let fetchedItemCount = try await services.dataService.fetchLinkedItemsBackgroundTask()
+          EventTracker.track(
+            .backgroundFetch(
+              jobStatus: .success,
+              itemCount: fetchedItemCount,
+              secondsElapsed: Int(startTime.timeIntervalSinceNow)
+            )
+          )
           task.setTaskCompleted(success: true)
         } catch {
-          logger.debug("fetch failed")
-          EventTracker.trackForDebugging("background fetch task failed")
+          EventTracker.track(
+            .backgroundFetch(
+              jobStatus: .failed,
+              itemCount: 0,
+              secondsElapsed: Int(startTime.timeIntervalSinceNow)
+            )
+          )
           task.setTaskCompleted(success: false)
         }
       }
     }
   }
 #endif
+
+// Command to simulate BG Task
 // e -l objc -- (void)[[BGTaskScheduler sharedScheduler] _simulateLaunchForTaskWithIdentifier:@"app.omnivore.fetchLinkedItems"]
diff --git a/apple/OmnivoreKit/Sources/Services/DataService/FetchLinkedItemsBackgroundTask.swift b/apple/OmnivoreKit/Sources/Services/DataService/FetchLinkedItemsBackgroundTask.swift
index 939f3330e..c3b407682 100644
--- a/apple/OmnivoreKit/Sources/Services/DataService/FetchLinkedItemsBackgroundTask.swift
+++ b/apple/OmnivoreKit/Sources/Services/DataService/FetchLinkedItemsBackgroundTask.swift
@@ -4,11 +4,13 @@ import Models
 import SwiftGraphQL
 
 extension DataService {
-  public func fetchLinkedItemsBackgroundTask() async throws {
+  public func fetchLinkedItemsBackgroundTask() async throws -> Int {
+    var fetchedItemCount = 0
+
     // Query the server for item IDs and compare against CoreData
     // to see what we're missing
     let missingItemIds = try await fetchMissingItemIDs()
-    guard !missingItemIds.isEmpty else { return }
+    guard !missingItemIds.isEmpty else { return 0 }
 
     let username: String? = await backgroundContext.perform(schedule: .immediate) {
       let fetchRequest: NSFetchRequest<Models.Viewer> = Viewer.fetchRequest()
@@ -24,8 +26,11 @@ extension DataService {
     for itemID in missingItemIds { // TOOD: run these in parallel
       logger.debug("fetching item with ID: \(itemID)")
       _ = try await articleContent(username: username, itemID: itemID, useCache: false)
+      fetchedItemCount += 1
       logger.debug("done fetching item with ID: \(itemID)")
     }
+
+    return fetchedItemCount
   }
 
   func fetchMissingItemIDs(previouslyFetchedIDs: [String] = [], cursor: String? = nil) async throws -> [String] {
diff --git a/apple/OmnivoreKit/Sources/Utils/EventTracking/TrackableEvents.swift b/apple/OmnivoreKit/Sources/Utils/EventTracking/TrackableEvents.swift
index 3450f1fca..0c663f231 100644
--- a/apple/OmnivoreKit/Sources/Utils/EventTracking/TrackableEvents.swift
+++ b/apple/OmnivoreKit/Sources/Utils/EventTracking/TrackableEvents.swift
@@ -3,6 +3,14 @@ import Foundation
 public enum TrackableEvent {
   case linkRead(linkID: String, slug: String, originalArticleURL: String)
   case debugMessage(message: String)
+  case backgroundFetch(jobStatus: BackgroundFetchJobStatus, itemCount: Int, secondsElapsed: Int)
+}
+
+public enum BackgroundFetchJobStatus: String {
+  case success
+  case failed
+  case authFailure
+  case timeExpired
 }
 
 public extension TrackableEvent {
@@ -12,6 +20,8 @@ public extension TrackableEvent {
       return "link_read"
     case .debugMessage:
       return "debug_message"
+    case .backgroundFetch:
+      return "background_fetch"
     }
   }
 
@@ -25,6 +35,12 @@ public extension TrackableEvent {
       ]
     case let .debugMessage(message: message):
       return ["message": message]
+    case let .backgroundFetch(jobStatus: jobStatus, itemCount: itemCount, secondsElapsed: secondsElapsed):
+      return [
+        "status": jobStatus.rawValue,
+        "seconds_elapsed": String(secondsElapsed),
+        "fetched_item_count": String(itemCount)
+      ]
     }
   }
 }