import Foundation
import HealthKit
import os

private let workoutLog = Logger(subsystem: "ch.hypnotruck.coach.watchkitapp", category: "workout")

/// Pilote la séance via HKLiveWorkoutBuilder et pousse les metrics vers l'iPhone.
/// `@MainActor` (donc Sendable) : l'état observable vit sur le main ; les callbacks
/// HealthKit, livrés hors-main, sont `nonisolated` et hoppent vers le main.
@MainActor
final class WorkoutManager: NSObject, ObservableObject {
    static let shared = WorkoutManager()

    @Published private(set) var heartRate = 0.0
    @Published private(set) var activeEnergyKcal = 0.0
    @Published private(set) var distanceMeters = 0.0
    @Published private(set) var elapsedSec = 0.0
    @Published private(set) var isRunning = false
    @Published private(set) var statusMessage: String?

    private let healthStore = HKHealthStore()
    private var session: HKWorkoutSession?
    private var builder: HKLiveWorkoutBuilder?

    private var lastSentAt = Date.distantPast
    private let sendInterval: TimeInterval = 2
    private var simTask: Task<Void, Never>?

    private override init() { super.init() }

    func startWorkout(activityType: HKWorkoutActivityType,
                      locationType: HKWorkoutSessionLocationType) async {
        guard !isRunning, session == nil else { return }
        guard HKHealthStore.isHealthDataAvailable() else {
            statusMessage = "HealthKit indisponible sur cet appareil"
            return
        }
        let distanceType = Self.distanceType(for: activityType)
        let hr = HKQuantityType(.heartRate)
        let energy = HKQuantityType(.activeEnergyBurned)
        let read: Set<HKObjectType> = [hr, energy, distanceType]
        let share: Set<HKSampleType> = [HKQuantityType.workoutType(), hr, energy, distanceType]

        do {
            try await healthStore.requestAuthorization(toShare: share, read: read)
            let woStatus = healthStore.authorizationStatus(for: HKQuantityType.workoutType())
            workoutLog.info("requestAuthorization OK; workoutType share status=\(woStatus.rawValue)")
            if woStatus == .sharingDenied {
                statusMessage = "Accès Santé refusé. Active Coach dans Réglages → Santé → Accès aux données, puis relance."
                return
            }
        } catch {
            workoutLog.error("requestAuthorization threw: \(error.localizedDescription)")
            statusMessage = "Autorisation Santé refusée : \(error.localizedDescription)"
            return
        }

        let config = HKWorkoutConfiguration()
        config.activityType = activityType
        config.locationType = locationType

        do {
            let session = try HKWorkoutSession(healthStore: healthStore, configuration: config)
            let builder = session.associatedWorkoutBuilder()
            builder.dataSource = HKLiveWorkoutDataSource(healthStore: healthStore,
                                                         workoutConfiguration: config)
            session.delegate = self
            builder.delegate = self
            self.session = session
            self.builder = builder

            let start = Date()
            session.startActivity(with: start)
            workoutLog.info("startActivity called, beginning collection…")
            try await builder.beginCollection(at: start)
            isRunning = true
            statusMessage = nil
            workoutLog.info("beginCollection OK, isRunning=true")
        } catch {
            self.session = nil
            self.builder = nil
            let ns = error as NSError
            workoutLog.error("start failed domain=\(ns.domain) code=\(ns.code): \(error.localizedDescription)")
            statusMessage = "Démarrage séance impossible : \(error.localizedDescription)"
        }
    }

    func pause() { session?.pause() }
    func resume() { session?.resume() }

    func end() {
        if let simTask {
            simTask.cancel()
            self.simTask = nil
            isRunning = false
            statusMessage = nil
        } else {
            session?.end()
        }
    }

    /// Mode test : FC simulée, sans HealthKit, pour valider le flux watch -> iPhone -> /live.
    func startSimulation() {
        guard !isRunning else { return }
        isRunning = true
        statusMessage = "Mode test — FC simulée"
        let startedAt = Date()
        simTask = Task { [weak self] in
            while !Task.isCancelled {
                guard let self else { return }
                let elapsed = Date().timeIntervalSince(startedAt)
                let hr = 110 + 40 * abs(sin(elapsed / 30))
                let kcal = elapsed / 6
                let dist = elapsed * 2.6
                self.heartRate = hr
                self.activeEnergyKcal = kcal
                self.distanceMeters = dist
                self.elapsedSec = elapsed
                ConnectivityManager.shared.sendSample([
                    "heartRate": hr,
                    "activeEnergyKcal": kcal,
                    "distanceMeters": dist,
                    "elapsedSec": elapsed,
                    "ts": Date().timeIntervalSince1970,
                    "sim": true
                ])
                try? await Task.sleep(nanoseconds: 2_000_000_000)
            }
        }
    }

    /// Appelé sur le main depuis le callback de collecte (hors-main).
    private func ingest(hr: Double?, kcal: Double?, dist: Double?, elapsed: TimeInterval) {
        if let hr { heartRate = hr }
        if let kcal { activeEnergyKcal = kcal }
        if let dist { distanceMeters = dist }
        elapsedSec = elapsed

        let now = Date()
        guard now.timeIntervalSince(lastSentAt) >= sendInterval else { return }
        lastSentAt = now
        ConnectivityManager.shared.sendSample([
            "heartRate": heartRate,
            "activeEnergyKcal": activeEnergyKcal,
            "distanceMeters": distanceMeters,
            "elapsedSec": elapsed,
            "ts": now.timeIntervalSince1970
        ])
    }

    private static func distanceType(for activity: HKWorkoutActivityType) -> HKQuantityType {
        activity == .cycling
            ? HKQuantityType(.distanceCycling)
            : HKQuantityType(.distanceWalkingRunning)
    }
}

extension WorkoutManager: HKLiveWorkoutBuilderDelegate {
    nonisolated func workoutBuilder(_ workoutBuilder: HKLiveWorkoutBuilder,
                                    didCollectDataOf collectedTypes: Set<HKSampleType>) {
        let hrType = HKQuantityType(.heartRate)
        let energyType = HKQuantityType(.activeEnergyBurned)
        let walkRun = HKQuantityType(.distanceWalkingRunning)
        let cycling = HKQuantityType(.distanceCycling)

        var hr: Double?
        var kcal: Double?
        var dist: Double?

        for type in collectedTypes {
            guard let qType = type as? HKQuantityType,
                  let stats = workoutBuilder.statistics(for: qType) else { continue }
            if qType == hrType {
                let bpm = HKUnit.count().unitDivided(by: .minute())
                hr = stats.mostRecentQuantity()?.doubleValue(for: bpm)
            } else if qType == energyType {
                kcal = stats.sumQuantity()?.doubleValue(for: .kilocalorie())
            } else if qType == walkRun || qType == cycling {
                dist = stats.sumQuantity()?.doubleValue(for: .meter())
            }
        }
        let elapsed = workoutBuilder.elapsedTime
        Task { @MainActor in
            self.ingest(hr: hr, kcal: kcal, dist: dist, elapsed: elapsed)
        }
    }

    nonisolated func workoutBuilderDidCollectEvent(_ workoutBuilder: HKLiveWorkoutBuilder) {}
}

extension WorkoutManager: HKWorkoutSessionDelegate {
    nonisolated func workoutSession(_ workoutSession: HKWorkoutSession,
                                    didChangeTo toState: HKWorkoutSessionState,
                                    from fromState: HKWorkoutSessionState,
                                    date: Date) {
        workoutLog.info("session didChangeTo state=\(toState.rawValue) from=\(fromState.rawValue)")
        guard toState == .ended else { return }
        let builder = workoutSession.associatedWorkoutBuilder()
        Task {
            try? await builder.endCollection(at: date)
            _ = try? await builder.finishWorkout()
        }
        Task { @MainActor in
            self.isRunning = false
            self.session = nil
            self.builder = nil
        }
    }

    nonisolated func workoutSession(_ workoutSession: HKWorkoutSession,
                                    didFailWithError error: Error) {
        let message = error.localizedDescription
        let ns = error as NSError
        workoutLog.error("session didFailWithError domain=\(ns.domain) code=\(ns.code): \(message)")
        Task { @MainActor in
            self.statusMessage = "Erreur séance : \(message)"
            self.isRunning = false
            self.session = nil
            self.builder = nil
        }
    }
}