//
// WorkoutHealthWriter.swift
// Workouts
//
// Copyright 2025 Rouslan Zenetl. All Rights Reserved.
//

import Foundation
import HealthKit
import SwiftData

/// Writes an *estimated* `HKWorkout` from the phone when a workout completes without
/// a watch session having recorded it — so phone-only workouts still feed the Move
/// ring. Mirrors what Apple's own "Add Workout" does: energy ≈ MET × bodyweight ×
/// duration, with bodyweight read from Health.
///
/// Dedupe is the whole game: a workout must be written to Health by the watch OR the
/// phone, never both. The signals are `WorkoutMetrics.source`/`healthKitWorkoutUUID`
/// (already present → skip) plus a debounce that a late watch update cancels.
@MainActor
final class WorkoutHealthWriter {
    private let container: ModelContainer
    private let healthStore = HKHealthStore()
    private weak var syncEngine: SyncEngine?

    /// Scheduled estimate tasks keyed by workout id — for debounce + cancellation.
    private var pending: [String: Task<Void, Never>] = [:]

    /// Grace window before writing, so a watch session that finishes a beat later can
    /// cancel us (its metrics arrive over WatchConnectivity and call `watchMetricsArrived`).
    private let debounce: Duration = .seconds(10)

    /// Default bodyweight when Health has none, in kg (~154 lb).
    private let fallbackBodyMassKg = 70.0

    init(container: ModelContainer, syncEngine: SyncEngine) {
        self.container = container
        self.syncEngine = syncEngine
    }

    private var context: ModelContext { container.mainContext }

    private var isScreenshotRun: Bool {
        #if DEBUG
        return ScreenshotSeed.isActive
        #else
        return false
        #endif
    }

    /// Request the scopes the estimate needs: share workouts + active energy, read
    /// body measurements (to size the estimate) and heart rate (to show watch data).
    func authorizeIfNeeded() {
        guard HKHealthStore.isHealthDataAvailable(), !isScreenshotRun else { return }
        healthStore.requestAuthorization(
            toShare: WorkoutHealthAuthorization.phoneShare,
            read: WorkoutHealthAuthorization.phoneRead
        ) { _, _ in }
    }

    /// A workout was persisted as completed. If nothing has written it to Health yet,
    /// schedule an estimated write after the debounce.
    func workoutCompleted(_ doc: WorkoutDocument) {
        guard HKHealthStore.isHealthDataAvailable(), !isScreenshotRun else { return }
        guard doc.status == WorkoutStatus.completed.rawValue, doc.end != nil else { return }
        // Already recorded (watch session, or a prior estimate) → nothing to do.
        guard doc.metrics?.healthKitWorkoutUUID == nil, doc.metrics?.source != .watch else { return }
        guard pending[doc.id] == nil else { return }

        let id = doc.id
        pending[id] = Task { [weak self] in
            try? await Task.sleep(for: self?.debounce ?? .seconds(10))
            guard let self, !Task.isCancelled else { return }
            self.pending[id] = nil
            await self.writeEstimate(workoutID: id)
        }
    }

    /// The watch recorded this workout — cancel any pending phone estimate so we don't
    /// double-write.
    func watchMetricsArrived(workoutID id: String) {
        pending[id]?.cancel()
        pending[id] = nil
    }

    /// Best-effort removal of a workout's Health record, on the user's request when
    /// deleting the workout in the app. HealthKit only allows deleting samples this
    /// app authored, so phone estimates delete cleanly while watch-recorded workouts
    /// (authored by the watch app's separate HealthKit source) may be refused — that
    /// refusal is swallowed; the record then stays in Health until removed there.
    func deleteFromHealth(uuidString: String) {
        guard HKHealthStore.isHealthDataAvailable(), let uuid = UUID(uuidString: uuidString) else { return }
        let healthStore = self.healthStore
        let query = HKSampleQuery(
            sampleType: .workoutType(),
            predicate: HKQuery.predicateForObject(with: uuid),
            limit: 1, sortDescriptors: nil
        ) { _, samples, _ in
            guard let workout = samples?.first else { return }
            healthStore.delete([workout]) { _, _ in }
        }
        healthStore.execute(query)
    }

    /// Launch safety sweep: catch workouts that completed but never got a Health record
    /// (e.g., the app was killed during the debounce). Bounded to the last day so we
    /// don't retroactively flood Health with historical workouts; idempotent via the
    /// per-workout UUID guard.
    func sweepRecentlyCompleted() {
        guard HKHealthStore.isHealthDataAvailable(), !isScreenshotRun else { return }
        let cutoff = Date().addingTimeInterval(-24 * 60 * 60)
        let completedRaw = WorkoutStatus.completed.rawValue
        let all = (try? context.fetch(FetchDescriptor<Workout>())) ?? []
        for w in all where w.statusRaw == completedRaw && w.metricHealthKitWorkoutUUID == nil {
            guard let end = w.end, end >= cutoff else { continue }
            workoutCompleted(WorkoutDocument(from: w))
        }
    }

    // MARK: - Estimate write

    private func writeEstimate(workoutID id: String) async {
        guard healthStore.authorizationStatus(for: .workoutType()) == .sharingAuthorized else { return }
        // Re-read the freshest doc — watch metrics may have landed during the debounce.
        guard let workout = CacheMapper.fetchWorkout(id: id, in: context),
              workout.status == .completed, let end = workout.end else { return }
        if let m = workout.metrics, m.healthKitWorkoutUUID != nil || m.source == .watch { return }

        let doc = WorkoutDocument(from: workout)
        let activity = activityType(for: doc)
        let bodyKg = await bodyMassKg()
        let hours = max(0, end.timeIntervalSince(doc.start)) / 3600
        let kcal = activity.met * bodyKg * hours

        let config = HKWorkoutConfiguration()
        config.activityType = activity.hkActivityType
        config.locationType = .indoor
        let builder = HKWorkoutBuilder(healthStore: healthStore, configuration: config, device: .local())

        do {
            try await builder.beginCollection(at: doc.start)
            if kcal > 0 {
                let sample = HKQuantitySample(
                    type: HKQuantityType(.activeEnergyBurned),
                    quantity: HKQuantity(unit: .kilocalorie(), doubleValue: kcal),
                    start: doc.start, end: end
                )
                try await withCheckedThrowingContinuation { (cont: CheckedContinuation<Void, Error>) in
                    builder.add([sample]) { _, error in
                        if let error { cont.resume(throwing: error) } else { cont.resume() }
                    }
                }
            }
            try await builder.endCollection(at: end)
            let saved = try await builder.finishWorkout()

            // Persist the estimate's metrics so it's never written twice.
            var updated = doc
            updated.metrics = WorkoutMetrics(
                activeEnergyKcal: kcal > 0 ? kcal : nil,
                avgHeartRate: nil, maxHeartRate: nil, minHeartRate: nil,
                totalVolume: WorkoutVolume.total(doc.logs),
                hrZoneSeconds: nil,
                healthKitWorkoutUUID: saved?.uuid.uuidString,
                source: .phoneEstimate,
                recordedAt: end
            )
            updated.updatedAt = Date()
            await syncEngine?.save(workout: updated)
        } catch {
            // Leave it unmarked; the next launch sweep retries within the window.
        }
    }

    /// The split's configured activity type, following the seed clone-on-edit
    /// redirect (the estimate can run seconds to hours after the workout, so the
    /// split may have forked in between). Generic strength when the split is gone.
    private func activityType(for doc: WorkoutDocument) -> WorkoutActivityType {
        if let splitID = doc.splitID {
            let resolved = syncEngine?.currentSplitID(for: splitID) ?? splitID
            if let split = CacheMapper.fetchSplit(id: resolved, in: context) {
                return split.activityTypeEnum
            }
        }
        return .traditionalStrength
    }

    /// Most recent body mass from Health, in kg, falling back to a default when none.
    private func bodyMassKg() async -> Double {
        let fallback = fallbackBodyMassKg
        return await withCheckedContinuation { continuation in
            let sort = NSSortDescriptor(key: HKSampleSortIdentifierEndDate, ascending: false)
            let query = HKSampleQuery(
                sampleType: HKQuantityType(.bodyMass), predicate: nil, limit: 1, sortDescriptors: [sort]
            ) { _, samples, _ in
                let kg = (samples?.first as? HKQuantitySample)?
                    .quantity.doubleValue(for: .gramUnit(with: .kilo))
                continuation.resume(returning: kg ?? fallback)
            }
            healthStore.execute(query)
        }
    }
}