Improve performance and fix fitness calculation bug

Author: liamcharger

.DS_Store

@@ -178,7 +178,7 @@ class DeviceManager: ObservableObject {
 
     func removeDevice(_ device: Device) {
         let objectID = device.objectID
-        let context = persistenceController.container.newBackgroundContext()
+        let context = persistenceController.container.viewContext
 
         context.perform {
             do {

InfiniLink/BLE/DeviceManager.swift

@@ -173,7 +173,7 @@ struct StepChartView: View {
                     let stepsRemaining = stepCountManager.stepGoal - steps
                     let distanceRemaining = fitnessCalculator.calculateDistance(steps: stepsRemaining)
                     let caloriesRemaining = fitnessCalculator.calculateCaloriesBurned(steps: stepsRemaining)
-                    let timeRemaining = fitnessCalculator.secondsFormatted(seconds: Int(fitnessCalculator.secondsForDistance(distance: distanceRemaining)), full: true)
+                    let timeRemaining = fitnessCalculator.secondsFormatted(seconds: fitnessCalculator.secondsForDistance(distance: distanceRemaining), full: true)
 
                     if stepsRemaining <= 1000 {
                         Text("You're almost there! A quick \(String(format: "%.1f", distanceRemaining)) \(personalizationController.units == .imperial ? "mile" : "km") walk should get you to your goal. It should only take you about \(timeRemaining).")

InfiniLink/Core/Components/Charts/Steps/StepChartView.swift

@@ -126,7 +126,7 @@ class FitnessCalculator {
     }
 
     func secondsForDistance(distance: Double, pace: Pace = .avgWalk) -> Int {
-        let speed: Double = personalizationController.units == .imperial ? pace.milesPerHour : (pace.milesPerHour * 1.60934)
+        let speed: Double = personalizationController.units == .imperial ? pace.milesPerHour : (pace.kmPerHour * 1.60934)
 
         return Int(ceil((distance / speed) * 60 * 60))
     }

InfiniLink/Utils/FitnessCalculator.swift

@@ -24,15 +24,19 @@ struct PersistenceController {
         }
         container.viewContext.automaticallyMergesChangesFromParent = true
     }
-    
+}
+
+extension PersistenceController {
     func save() {
-        Task {
+        guard container.viewContext.hasChanges else { return }
+        
+        container.viewContext.perform {
             do {
-                try await container.viewContext.perform {
-                    try container.viewContext.save()
-                }
+                try self.container.viewContext.save()
             } catch {
-                log("Unresolved error saving context: \(error.localizedDescription)", caller: "PersistenceController")
+                // Handle the error appropriately. However, it's useful to use
+                // `fatalError(_:file:line:)` during development.
+                log("Failed to save view context: \(error.localizedDescription)", caller: "PersistenceController")
             }
         }
     }