HealthKit Workout Zones

import SwiftUI
import HealthKit

struct WorkoutZoneSummaryView: View {
    @State private var zoneDurations: [HKWorkoutZoneDuration] = []
    @State private var statusMessage: String = "Tap to load zones"

    private let healthStore = HKHealthStore()

    var body: some View {
        NavigationStack {
            List {
                Section("Heart Rate Zone Durations") {
                    if zoneDurations.isEmpty {
                        Text(statusMessage)
                            .foregroundStyle(.secondary)
                    } else {
                        ForEach(zoneDurations, id: \.zone.index) { zoneDuration in
                            HStack {
                                VStack(alignment: .leading) {
                                    Text("Zone \(zoneDuration.zone.index + 1)")
                                        .font(.headline)
                                    let minBPM = zoneDuration.zone.minimumQuantity?.doubleValue(for: .count().unitDivided(by: .minute()))
                                    let maxBPM = zoneDuration.zone.maximumQuantity?.doubleValue(for: .count().unitDivided(by: .minute()))
                                    if let min = minBPM, let max = maxBPM {
                                        Text("\(Int(min))–\(Int(max)) bpm")
                                            .font(.caption)
                                            .foregroundStyle(.secondary)
                                    } else if let min = minBPM {
                                        Text("> \(Int(min)) bpm")
                                            .font(.caption)
                                            .foregroundStyle(.secondary)
                                    }
                                }
                                Spacer()
                                Text(formatDuration(zoneDuration.duration))
                                    .monospacedDigit()
                            }
                        }
                    }
                }
            }
            .navigationTitle("Zone Summary")
            .toolbar {
                Button("Load Latest") { Task { await loadLatestWorkoutZones() } }
            }
        }
    }

    private func formatDuration(_ interval: TimeInterval) -> String {
        let minutes = Int(interval) / 60
        let seconds = Int(interval) % 60
        return String(format: "%d:%02d", minutes, seconds)
    }

    private func loadLatestWorkoutZones() async {
        let typesToRead: Set<HKObjectType> = [
            HKObjectType.workoutType(),
            HKObjectType.quantityType(forIdentifier: .heartRate)!
        ]
        guard (try? await healthStore.requestAuthorization(toShare: [], read: typesToRead)) != nil else {
            statusMessage = "Authorization failed"
            return
        }

        let workoutType = HKObjectType.workoutType()
        let sort = NSSortDescriptor(key: HKSampleSortIdentifierEndDate, ascending: false)
        let query = HKSampleQuery(sampleType: workoutType, predicate: nil, limit: 1, sortDescriptors: [sort]) { _, samples, _ in
            guard let workout = samples?.first as? HKWorkout else {
                DispatchQueue.main.async { statusMessage = "No workouts found" }
                return
            }
            let hrType = HKQuantityType(.heartRate)
            if let zoneGroup = workout.zoneGroupsByType[hrType] {
                DispatchQueue.main.async {
                    self.zoneDurations = zoneGroup.zoneDurations
                    if zoneDurations.isEmpty { statusMessage = "No zone data in latest workout" }
                }
            } else {
                DispatchQueue.main.async { statusMessage = "No heart rate zones recorded" }
            }
        }
        healthStore.execute(query)
    }
}

#Preview {
    WorkoutZoneSummaryView()
}