Persist preferredTaskDate to avoid any issues with the app gets terminated and relaunched in the background

Author: staskus

WooCommerce/Classes/Tools/BackgroundTasks/BackgroundTaskRefreshDispatcher.swift

@@ -4,7 +4,7 @@ import BackgroundTasks
 import Network
 
 final class BackgroundTaskRefreshDispatcher {
-    enum BackgroundTaskType: CaseIterable {
+    enum BackgroundTaskType: Codable, CaseIterable {
         case ordersAndDashboardSync
         case posCatalogSync
     }

WooCommerce/Classes/Tools/BackgroundTasks/BackgroundTaskSchedule.swift

@@ -15,11 +15,17 @@ extension BackgroundTaskRefreshDispatcher.BackgroundTaskType {
 /// BackgroundTaskSchedule is a helper tool to determine the next BackgroundTask based on the preferred run period
 ///
 final class BackgroundTaskSchedule {
-    private var preferredTaskDate: [BackgroundTaskRefreshDispatcher.BackgroundTaskType: Date] = [:]
+    private var preferredTaskDate: [BackgroundTaskRefreshDispatcher.BackgroundTaskType: Date] = [:] {
+        didSet { setPersistedDates () }
+    }
     private let timeProvider: TimeProvider
+    private let userDefaults: UserDefaults
 
-    init(timeProvider: TimeProvider = DefaultTimeProvider()) {
+    init(timeProvider: TimeProvider = DefaultTimeProvider(),
+         userDefaults: UserDefaults = .standard) {
         self.timeProvider = timeProvider
+        self.userDefaults = userDefaults
+        loadPersistedDates()
     }
 
     // Set preferred task dates when going into background
@@ -54,3 +60,24 @@ final class BackgroundTaskSchedule {
         preferredTaskDate[task] = timeProvider.now().addingTimeInterval(task.period)
     }
 }
+
+// MARK: - Persistence
+
+private extension BackgroundTaskSchedule {
+    private var userDefaultsKey: String { "BackgroundTaskSchedule.preferredTaskDate" }
+
+    private func loadPersistedDates() {
+        guard let data = userDefaults.data(forKey: userDefaultsKey),
+              let decoded = try? JSONDecoder().decode([BackgroundTaskRefreshDispatcher.BackgroundTaskType: Date].self, from: data)
+        else {
+            return
+        }
+        preferredTaskDate = decoded
+    }
+
+    private func setPersistedDates() {
+        if let data = try? JSONEncoder().encode(preferredTaskDate) {
+            userDefaults.set(data, forKey: userDefaultsKey)
+        }
+    }
+}

WooCommerce/WooCommerceTests/Tools/BackgroundTaskScheduleTests.swift

@@ -8,8 +8,10 @@ struct BackgroundTaskScheduleTests {
     private let timeProvider: MockTimeProvider
 
     init() {
+        let userDefaults = UserDefaults(suiteName: #file)!
+        userDefaults.removePersistentDomain(forName: #file)
         timeProvider = MockTimeProvider()
-        sut = BackgroundTaskSchedule(timeProvider: timeProvider)
+        sut = BackgroundTaskSchedule(timeProvider: timeProvider, userDefaults: userDefaults)
     }
 
     @Test func initial_state_returns_task_with_shortest_period() {