[COASTAL-969] System time offset detected (#516)

* report when system time offset is detected

* removed SystemTimeOffsetDetector protocol

* provide a time interval instead of an indicator

Author: nhamming

Loop/Managers/DeviceDataManager.swift

@@ -211,6 +211,8 @@ final class DeviceDataManager {
 
     private(set) var pumpManagerHUDProvider: HUDProvider?
 
+    private var trustedTimeChecker: TrustedTimeChecker
+
     // MARK: - WatchKit
 
     private var watchManager: WatchDataManager!
@@ -231,7 +233,8 @@ final class DeviceDataManager {
          closedLoopStatus: ClosedLoopStatus,
          cacheStore: PersistenceController,
          localCacheDuration: TimeInterval,
-         overrideHistory: TemporaryScheduleOverrideHistory)
+         overrideHistory: TemporaryScheduleOverrideHistory,
+         trustedTimeChecker: TrustedTimeChecker)
     {
 
         let fileManager = FileManager.default
@@ -310,6 +313,8 @@ final class DeviceDataManager {
         // HealthStorePreferredGlucoseUnitDidChange will be notified once the user completes the health access form. Set to .milligramsPerDeciliter until then
         displayGlucoseUnitObservable = DisplayGlucoseUnitObservable(displayGlucoseUnit: glucoseStore.preferredUnit ?? .milligramsPerDeciliter)
 
+        self.trustedTimeChecker = trustedTimeChecker
+
         if let pumpManagerRawValue = rawPumpManager ?? UserDefaults.appGroup?.legacyPumpManagerRawValue {
             pumpManager = pumpManagerFromRawValue(pumpManagerRawValue)
             // Update lastPumpEventsReconciliation on DoseStore
@@ -1682,3 +1687,7 @@ extension DeviceDataManager {
 }
 
 extension DeviceDataManager: DeviceStatusProvider {}
+
+extension DeviceDataManager {
+    var detectedSystemTimeOffset: TimeInterval { trustedTimeChecker.detectedSystemTimeOffset }
+}

Loop/Managers/LoopAppManager.swift

@@ -175,7 +175,8 @@ class LoopAppManager: NSObject {
                                                    closedLoopStatus: closedLoopStatus,
                                                    cacheStore: cacheStore,
                                                    localCacheDuration: localCacheDuration,
-                                                   overrideHistory: overrideHistory
+                                                   overrideHistory: overrideHistory,
+                                                   trustedTimeChecker: trustedTimeChecker
         )
         settingsManager.deviceStatusProvider = deviceDataManager
 

Loop/Managers/TrustedTimeChecker.swift

@@ -13,6 +13,7 @@ import UIKit
 fileprivate extension UserDefaults {
     private enum Key: String {
         case lastSignificantTimeChangeAlert = "com.loopkit.Loop.LastSignificantTimeChangeAlert"
+        case detectedSystemTimeOffset = "com.loopkit.Loop.DetectedSystemTimeOffset"
     }
 
     var lastSignificantTimeChangeAlert: Date? {
@@ -23,6 +24,15 @@ fileprivate extension UserDefaults {
             set(newValue, forKey: Key.lastSignificantTimeChangeAlert.rawValue)
         }
     }
+
+    var detectedSystemTimeOffset: TimeInterval? {
+        get {
+            return object(forKey: Key.detectedSystemTimeOffset.rawValue) as? TimeInterval
+        }
+        set {
+            set(newValue, forKey: Key.detectedSystemTimeOffset.rawValue)
+        }
+    }
 }
 
 class TrustedTimeChecker {
@@ -34,6 +44,12 @@ class TrustedTimeChecker {
     private weak var alertManager: AlertManager?
     private lazy var log = DiagnosticLog(category: "TrustedTimeChecker")
 
+    var detectedSystemTimeOffset: TimeInterval {
+        didSet {
+            UserDefaults.standard.detectedSystemTimeOffset = detectedSystemTimeOffset
+        }
+    }
+
     init(alertManager: AlertManager) {
         ntpClient = TrueTimeClient.sharedInstance
         #if DEBUG
@@ -43,6 +59,7 @@ class TrustedTimeChecker {
         #endif
         ntpClient.start()
         self.alertManager = alertManager
+        self.detectedSystemTimeOffset = UserDefaults.standard.detectedSystemTimeOffset ?? 0
         NotificationCenter.default.addObserver(forName: UIApplication.significantTimeChangeNotification,
                                                object: nil, queue: nil) { [weak self] _ in self?.checkTrustedTime() }
         NotificationCenter.default.addObserver(forName: .LoopRunning,
@@ -56,12 +73,16 @@ class TrustedTimeChecker {
             case let .success(referenceTime):
                 let deviceNow = Date()
                 let ntpNow = referenceTime.now()
-                let timeDelta = abs(ntpNow.timeIntervalSince(deviceNow))
+                let timeDelta = ntpNow.timeIntervalSince(deviceNow)
                 let timeSinceLastAlert = abs(ntpNow.timeIntervalSince(UserDefaults.standard.lastSignificantTimeChangeAlert ?? Date.distantPast))
-                if timeDelta > self.acceptableTimeDelta, timeSinceLastAlert > self.minimumAlertFrequency {
+
+                if abs(timeDelta) > self.acceptableTimeDelta, timeSinceLastAlert > self.minimumAlertFrequency {
                     self.log.info("applicationSignificantTimeChange: ntpNow = %@, deviceNow = %@", ntpNow.debugDescription, deviceNow.debugDescription)
                     self.issueTimeChangedAlert()
+                    self.detectedSystemTimeOffset = timeDelta
                     UserDefaults.standard.lastSignificantTimeChangeAlert = ntpNow
+                } else {
+                    self.detectedSystemTimeOffset = 0
                 }
             case let .failure(error):
                 self.log.error("applicationSignificantTimeChange: Error getting NTP time: %@", error.localizedDescription)