import CoreData
import CloudKit
import Combine
import WidgetKit

extension Notification.Name {
    static let cloudKitForceReload = Notification.Name("cloudKitForceReload")
}

class CoreDataStack: ObservableObject {
    static let shared = CoreDataStack()

    static let appGroupIdentifier = "group.com.alexandrevazquez.portfoliojournal"
    static let cloudKitContainerIdentifier = "iCloud.com.alexandrevazquez.portfoliojournal"

    private static var cloudKitEnabled: Bool {
        UserDefaults.standard.bool(forKey: "cloudSyncEnabled")
    }

    private static var appGroupEnabled: Bool {
        true
    }

    private static func migrateStoreIfNeeded(from sourceURL: URL, to destinationURL: URL) {
        let fileManager = FileManager.default
        guard fileManager.fileExists(atPath: sourceURL.path) else {
            return
        }

        let sourceHasData = storeHasData(at: sourceURL)
        let destinationHasData = storeHasData(at: destinationURL)
        guard sourceHasData, !destinationHasData else { return }

        removeStoreFilesIfNeeded(at: destinationURL)

        let relatedSuffixes = ["", "-wal", "-shm"]
        for suffix in relatedSuffixes {
            let source = URL(fileURLWithPath: sourceURL.path + suffix)
            let destination = URL(fileURLWithPath: destinationURL.path + suffix)
            guard fileManager.fileExists(atPath: source.path),
                  !fileManager.fileExists(atPath: destination.path) else {
                continue
            }

            do {
                try fileManager.copyItem(at: source, to: destination)
            } catch {
                print("Core Data store migration failed for \(source.lastPathComponent): \(error)")
            }
        }
    }

    private static func removeStoreFilesIfNeeded(at url: URL) {
        let fileManager = FileManager.default
        let relatedSuffixes = ["", "-wal", "-shm"]
        for suffix in relatedSuffixes {
            let fileURL = URL(fileURLWithPath: url.path + suffix)
            guard fileManager.fileExists(atPath: fileURL.path) else { continue }
            do {
                try fileManager.removeItem(at: fileURL)
            } catch {
                print("Failed to remove existing store file \(fileURL.lastPathComponent): \(error)")
            }
        }
    }

    private static func storeHasData(at url: URL) -> Bool {
        let fileManager = FileManager.default
        guard fileManager.fileExists(atPath: url.path),
              let model = NSManagedObjectModel.mergedModel(from: [Bundle.main]) else {
            return false
        }

        let coordinator = NSPersistentStoreCoordinator(managedObjectModel: model)
        do {
            try coordinator.addPersistentStore(
                ofType: NSSQLiteStoreType,
                configurationName: nil,
                at: url,
                options: [NSReadOnlyPersistentStoreOption: true]
            )
        } catch {
            print("Failed to open store for data check: \(error)")
            return false
        }

        let context = NSManagedObjectContext(concurrencyType: .privateQueueConcurrencyType)
        context.persistentStoreCoordinator = coordinator

        let snapshotRequest = NSFetchRequest<NSManagedObject>(entityName: "Snapshot")
        snapshotRequest.resultType = .countResultType
        let snapshotCount = (try? context.count(for: snapshotRequest)) ?? 0
        if snapshotCount > 0 {
            return true
        }

        let sourceRequest = NSFetchRequest<NSManagedObject>(entityName: "InvestmentSource")
        sourceRequest.resultType = .countResultType
        let sourceCount = (try? context.count(for: sourceRequest)) ?? 0
        return sourceCount > 0
    }

    private static func resolveStoreURL() -> URL {
        let defaultURL = NSPersistentContainer.defaultDirectoryURL()
            .appendingPathComponent("PortfolioJournal.sqlite")

        guard appGroupEnabled,
              let appGroupURL = FileManager.default
                .containerURL(forSecurityApplicationGroupIdentifier: appGroupIdentifier)?
                .appendingPathComponent("PortfolioJournal.sqlite") else {
            if appGroupEnabled {
                print("App Group unavailable; using default store URL: \(defaultURL)")
            }
            return defaultURL
        }

        migrateStoreIfNeeded(from: defaultURL, to: appGroupURL)
        return appGroupURL
    }

    @Published private(set) var isLoaded = false
    @Published private(set) var lastImportDate: Date?
    @Published private(set) var lastExportDate: Date?
    @Published private(set) var isSyncing = false
    @Published private(set) var lastSyncError: String?
    /// Full recursive dump of the last sync error tree (leaf CKError codes, record
    /// types, retry-after, raw userInfo keys). Surfaced in the copyable diagnostics
    /// so we can see WHICH record CloudKit rejects, not just the opaque code 2.
    @Published private(set) var lastSyncErrorDetail: String?
    /// Human-readable, actionable explanation of the last sync error (nil if none).
    @Published private(set) var lastSyncErrorHint: String?
    /// True only when sync is genuinely broken (never synced + total failure).
    /// Partial failures after a working sync are informational, not alarming.
    @Published private(set) var syncErrorIsCritical = false

    var lastSyncDate: Date? { lastImportDate }

    var localSourceCount: Int {
        let request = NSFetchRequest<NSManagedObject>(entityName: "InvestmentSource")
        return (try? viewContext.count(for: request)) ?? 0
    }

    var localSnapshotCount: Int {
        let request = NSFetchRequest<NSManagedObject>(entityName: "Snapshot")
        return (try? viewContext.count(for: request)) ?? 0
    }

    private init() {
        // Register CloudKit event observer BEFORE the container is created so we
        // never miss an import/export event that fires during store loading.
        if Self.cloudKitEnabled {
            NotificationCenter.default.addObserver(
                self,
                selector: #selector(cloudKitEventChanged(_:)),
                name: NSPersistentCloudKitContainer.eventChangedNotification,
                object: nil
            )
        }
    }

    lazy var persistentContainer: NSPersistentContainer = {
        let container: NSPersistentContainer
        if Self.cloudKitEnabled {
            container = NSPersistentCloudKitContainer(name: "PortfolioJournal")
        } else {
            container = NSPersistentContainer(name: "PortfolioJournal")
        }

        // App Group store URL for sharing with widgets. Fall back if not entitled.
        let storeURL = Self.resolveStoreURL()

        let description = NSPersistentStoreDescription(url: storeURL)
        description.shouldMigrateStoreAutomatically = true
        description.shouldInferMappingModelAutomatically = true

        // Always enable history tracking so data created before CloudKit was enabled
        // is visible to NSPersistentCloudKitContainer when sync is later turned on.
        description.setOption(true as NSNumber, forKey: NSPersistentHistoryTrackingKey)
        description.setOption(true as NSNumber, forKey: NSPersistentStoreRemoteChangeNotificationPostOptionKey)

        if Self.cloudKitEnabled {
            description.cloudKitContainerOptions = NSPersistentCloudKitContainerOptions(
                containerIdentifier: Self.cloudKitContainerIdentifier
            )
        }

        container.persistentStoreDescriptions = [description]

        container.loadPersistentStores { [weak self] description, error in
            if let error = error as NSError? {
                // In production, handle this error appropriately
                print("Core Data failed to load: \(error), \(error.userInfo)")
            } else {
                print("Core Data loaded successfully at: \(description.url?.path ?? "unknown")")
                #if DEBUG
                // Dev-only, opt-in: push the FULL model schema to the Development CloudKit
                // environment so optional fields that were never exported by a Debug run
                // (e.g. monthlyContribution on InvestmentSource, allocationTarget on Category)
                // get materialised — otherwise they can't be deployed to Production and every
                // Production export rejects those records (bare CKErrorPartialFailure).
                // Run ONCE from Xcode with launch arg -InitializeCloudKitSchema, watch for the
                // ✅ log, then deploy to Production in the CloudKit Console and remove the arg.
                if ProcessInfo.processInfo.arguments.contains("-InitializeCloudKitSchema"),
                   let ckContainer = container as? NSPersistentCloudKitContainer {
                    do {
                        try ckContainer.initializeCloudKitSchema(options: [])
                        print("✅ CloudKit schema initialized in Development. Now open the CloudKit Console → Deploy Schema Changes → Production.")
                    } catch {
                        print("❌ initializeCloudKitSchema failed: \(error)")
                    }
                }
                #endif
            }
            DispatchQueue.main.async {
                self?.isLoaded = true
                // Merge the pre-stable-UUID default duplicates. Safe now: the merge
                // reassigns children then deletes losers, and the relevant relationships
                // use the Nullify delete rule so a propagated parent-delete can never
                // cascade-wipe children (unlike the build-68 Cascade disaster).
                self?.mergeDefaultDuplicates()
                MonthlyCheckInStore.migrateIfNeeded()
                // Migrate device-local UserDefaults data into Core Data so it syncs via iCloud.
                MonthlyContributionStore.migrateIfNeeded(context: container.viewContext)
                AllocationTargetStore.migrateIfNeeded(context: container.viewContext)
                // Seed demo data when running in screenshot capture mode.
                ScreenshotMode.seedIfNeeded()
                // Apply share-extension captures and publish the source mirror.
                Task { @MainActor in
                    SharedQuickUpdateSync.ingestPending()
                    SharedQuickUpdateSync.refreshMirror()
                }
            }
        }

        // Merge policy - remote changes win
        container.viewContext.automaticallyMergesChangesFromParent = true
        container.viewContext.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy

        // Performance optimizations
        container.viewContext.undoManager = nil
        container.viewContext.shouldDeleteInaccessibleFaults = true

        if Self.cloudKitEnabled {
            NotificationCenter.default.addObserver(
                self,
                selector: #selector(processRemoteChanges),
                name: .NSPersistentStoreRemoteChange,
                object: container.persistentStoreCoordinator
            )
        }

        return container
    }()

    var viewContext: NSManagedObjectContext {
        return persistentContainer.viewContext
    }

    // MARK: - Cleanup Duplicates

    /// Removes duplicate objects that have the same UUID, keeping only the oldest one.
    /// This fixes data corruption from race conditions during object creation, and also
    /// handles the case where a CloudKit first-time sync imports records that already exist
    /// locally (because they were created before CloudKit was enabled).
    @discardableResult
    func cleanupDuplicateObjects() -> Int {
        var totalRemoved = 0
        let context = viewContext
        context.performAndWait {
            // Clean up Snapshots first — before cascade rules from InvestmentSource fire,
            // so we deduplicate by UUID and not rely solely on cascade.
            totalRemoved += cleanupDuplicates(entityName: "Snapshot", idKey: "id", context: context)
            totalRemoved += cleanupDuplicates(entityName: "Goal", idKey: "id", context: context)
            totalRemoved += cleanupDuplicates(entityName: "Account", idKey: "id", context: context)
            totalRemoved += cleanupDuplicates(entityName: "InvestmentSource", idKey: "id", context: context)
            totalRemoved += cleanupDuplicates(entityName: "Category", idKey: "id", context: context)

            if context.hasChanges {
                try? context.save()
            }
        }
        return totalRemoved
    }

    @discardableResult
    private func cleanupDuplicates(entityName: String, idKey: String, context: NSManagedObjectContext) -> Int {
        let request = NSFetchRequest<NSManagedObject>(entityName: entityName)
        request.sortDescriptors = [NSSortDescriptor(key: "createdAt", ascending: true)]

        guard let objects = try? context.fetch(request) else { return 0 }

        var seenIds = Set<UUID>()
        var objectsToDelete: [NSManagedObject] = []

        for object in objects {
            guard let objectId = object.value(forKey: idKey) as? UUID else { continue }
            if seenIds.contains(objectId) {
                objectsToDelete.append(object)
            } else {
                seenIds.insert(objectId)
            }
        }

        if !objectsToDelete.isEmpty {
            print("[Dedup] Removing \(objectsToDelete.count) duplicate \(entityName) objects")
            for object in objectsToDelete { context.delete(object) }
        }
        return objectsToDelete.count
    }

    // MARK: - Logical Duplicate Cleanup (cross-device / cross-environment)

    /// Removes *logical* duplicates: records that represent the same real-world
    /// entity but carry DIFFERENT UUIDs. These appear when the same data is
    /// created independently on two devices — or in the Development vs Production
    /// CloudKit environments — and then merged by CloudKit, which keys on the
    /// record name (our UUID) and therefore never recognises them as the same,
    /// keeping both. The classic trigger here: `createDefaultAccountIfNeeded` and
    /// `ensureDefaultCategoriesExist` seed defaults on every device at launch
    /// *before* the first import arrives, so each device contributes its own
    /// "Default" account + 8 categories → they pile up (8 accounts, 23 categories).
    ///
    /// The UUID-based `cleanupDuplicateObjects()` cannot catch these because the
    /// UUIDs differ. Here we group by a stable *business key* and keep a single
    /// deterministic winner (earliest `createdAt`, tie-broken by lowest UUID —
    /// both synced fields, so every device independently picks the SAME survivor
    /// and the deletes converge instead of racing each other into data loss),
    /// reassigning children onto the survivor before deleting the losers.
    @discardableResult
    func cleanupLogicalDuplicates() -> Int {
        var removed = 0
        let context = viewContext
        context.performAndWait {
            // Parents first: re-point children onto the surviving parent so the
            // child keys (which embed the parent's id) stay stable for later passes.
            removed += mergeLogicalDuplicates(
                entityName: "Account",
                childRelationships: ["sources", "goals"],
                context: context,
                key: { obj in
                    let name = (obj.value(forKey: "name") as? String ?? "")
                        .trimmingCharacters(in: .whitespacesAndNewlines).lowercased()
                    return name.isEmpty ? "" : "account|\(name)"
                })

            removed += mergeLogicalDuplicates(
                entityName: "Category",
                childRelationships: ["sources"],
                context: context,
                key: { obj in
                    let name = (obj.value(forKey: "name") as? String ?? "")
                        .trimmingCharacters(in: .whitespacesAndNewlines).lowercased()
                    return name.isEmpty ? "" : "category|\(name)"
                })

            removed += mergeLogicalDuplicates(
                entityName: "InvestmentSource",
                childRelationships: ["snapshots", "transactions"],
                context: context,
                key: { obj in
                    let name = (obj.value(forKey: "name") as? String ?? "")
                        .trimmingCharacters(in: .whitespacesAndNewlines).lowercased()
                    guard !name.isEmpty else { return "" }
                    let acc = (obj.value(forKey: "account") as? NSManagedObject)?
                        .value(forKey: "id") as? UUID
                    return "source|\(acc?.uuidString ?? "none")|\(name)"
                })

            removed += mergeLogicalDuplicates(
                entityName: "Snapshot",
                childRelationships: [],
                context: context,
                key: { obj in
                    // Only dedup snapshots that share the same source, same day AND
                    // same value — a true copy. Orphans (nil source) are left alone.
                    guard let src = (obj.value(forKey: "source") as? NSManagedObject)?
                            .value(forKey: "id") as? UUID,
                          let date = obj.value(forKey: "date") as? Date else { return "" }
                    let day = (date.timeIntervalSinceReferenceDate / 86_400).rounded(.down)
                    let value = (obj.value(forKey: "value") as? NSDecimalNumber)?
                        .stringValue ?? "nil"
                    return "snapshot|\(src.uuidString)|\(day)|\(value)"
                })

            removed += mergeLogicalDuplicates(
                entityName: "Goal",
                childRelationships: [],
                context: context,
                key: { obj in
                    let name = (obj.value(forKey: "name") as? String ?? "")
                        .trimmingCharacters(in: .whitespacesAndNewlines).lowercased()
                    guard !name.isEmpty else { return "" }
                    let target = (obj.value(forKey: "targetAmount") as? NSDecimalNumber)?
                        .stringValue ?? "nil"
                    return "goal|\(name)|\(target)"
                })

            removed += mergeLogicalDuplicates(
                entityName: "JournalEntry",
                childRelationships: [],
                context: context,
                key: { obj in
                    let monthKey = (obj.value(forKey: "monthKey") as? String ?? "")
                        .trimmingCharacters(in: .whitespacesAndNewlines).lowercased()
                    return monthKey.isEmpty ? "" : "journal|\(monthKey)"
                })

            if context.hasChanges {
                try? context.save()
            }
        }
        return removed
    }

    /// Groups objects of `entityName` by `key`, keeps one deterministic winner
    /// per group, moves every child in `childRelationships` from the losers onto
    /// the winner, then deletes the losers. An empty key means "never dedup this
    /// object" (degenerate identity — e.g. no name, orphan snapshot).
    @discardableResult
    private func mergeLogicalDuplicates(
        entityName: String,
        childRelationships: [String],
        context: NSManagedObjectContext,
        key: (NSManagedObject) -> String
    ) -> Int {
        let request = NSFetchRequest<NSManagedObject>(entityName: entityName)
        guard let objects = try? context.fetch(request), !objects.isEmpty else { return 0 }

        var groups: [String: [NSManagedObject]] = [:]
        for obj in objects {
            let k = key(obj)
            guard !k.isEmpty else { continue }
            groups[k, default: []].append(obj)
        }

        var removed = 0
        for (_, group) in groups where group.count > 1 {
            // Deterministic ordering → same winner on every device.
            let sorted = group.sorted { a, b in
                let ca = (a.value(forKey: "createdAt") as? Date) ?? .distantPast
                let cb = (b.value(forKey: "createdAt") as? Date) ?? .distantPast
                if ca != cb { return ca < cb }
                let ia = (a.value(forKey: "id") as? UUID)?.uuidString ?? ""
                let ib = (b.value(forKey: "id") as? UUID)?.uuidString ?? ""
                return ia < ib
            }
            let winner = sorted[0]
            for loser in sorted.dropFirst() {
                for rel in childRelationships {
                    let children = loser.mutableSetValue(forKey: rel)
                    guard children.count > 0 else { continue }
                    let winnerChildren = winner.mutableSetValue(forKey: rel)
                    // Snapshot children first so the winner is a superset before delete.
                    for child in children.allObjects {
                        winnerChildren.add(child)  // reassigns the modeled inverse
                    }
                }
                context.delete(loser)
                removed += 1
            }
        }
        if removed > 0 {
            print("[LogicalDedup] \(entityName): removed \(removed) duplicate(s)")
        }
        return removed
    }

    // MARK: - Merge Default Duplicates (CloudKit-safe)

    /// Merges the duplicate default Accounts and Categories that piled up before
    /// the stable-UUID fix (per-device "Default" accounts + default categories with
    /// random UUIDs). CloudKit-safe now because Account.sources/goals and
    /// Category.sources use the Nullify delete rule — so a merged-away parent's
    /// delete can never cascade-wipe children on any device (the build-68 disaster
    /// was Cascade + cross-device import ordering). Children are reassigned to a
    /// DETERMINISTIC winner (the stable-UUID record if present, else earliest
    /// createdAt / lowest UUID) so every device converges on the same survivor.
    @discardableResult
    func mergeDefaultDuplicates() -> Int {
        var merged = 0
        let context = viewContext
        context.performAndWait {
            merged += mergeDefaultAccounts(in: context)
            merged += mergeDuplicateCategories(in: context)
            if context.hasChanges { try? context.save() }
        }
        return merged
    }

    private func deterministicWinner(_ objects: [NSManagedObject], stableID: UUID?) -> NSManagedObject? {
        if let stableID, let canonical = objects.first(where: { ($0.value(forKey: "id") as? UUID) == stableID }) {
            return canonical
        }
        return objects.sorted {
            let a = ($0.value(forKey: "createdAt") as? Date) ?? .distantPast
            let b = ($1.value(forKey: "createdAt") as? Date) ?? .distantPast
            if a != b { return a < b }
            let ida = ($0.value(forKey: "id") as? UUID)?.uuidString ?? ""
            let idb = ($1.value(forKey: "id") as? UUID)?.uuidString ?? ""
            return ida < idb
        }.first
    }

    private func reassign(_ children: Any?, key: String, to winner: NSManagedObject) {
        guard let set = children as? Set<NSManagedObject> else { return }
        for child in Array(set) { child.setValue(winner, forKey: key) }
    }

    private func mergeDefaultAccounts(in context: NSManagedObjectContext) -> Int {
        let request = NSFetchRequest<NSManagedObject>(entityName: "Account")
        request.predicate = NSPredicate(format: "name == %@", Account.defaultAccountName)
        guard let accounts = try? context.fetch(request), accounts.count > 1,
              let winner = deterministicWinner(accounts, stableID: Account.defaultAccountStableID) else { return 0 }
        var removed = 0
        for loser in accounts where loser !== winner {
            reassign(loser.value(forKey: "sources"), key: "account", to: winner)
            reassign(loser.value(forKey: "goals"), key: "account", to: winner)
            context.delete(loser)
            removed += 1
        }
        if removed > 0 { print("[MergeDefaults] accounts: removed \(removed)") }
        return removed
    }

    private func mergeDuplicateCategories(in context: NSManagedObjectContext) -> Int {
        let request = NSFetchRequest<NSManagedObject>(entityName: "Category")
        guard let categories = try? context.fetch(request), !categories.isEmpty else { return 0 }
        var byName: [String: [NSManagedObject]] = [:]
        for c in categories {
            let name = (c.value(forKey: "name") as? String ?? "").trimmingCharacters(in: .whitespacesAndNewlines).lowercased()
            guard !name.isEmpty else { continue }
            byName[name, default: []].append(c)
        }
        var removed = 0
        for (name, group) in byName where group.count > 1 {
            let stable = Category.stableID(for: name)
            guard let winner = deterministicWinner(group, stableID: stable) else { continue }
            for loser in group where loser !== winner {
                reassign(loser.value(forKey: "sources"), key: "category", to: winner)
                context.delete(loser)
                removed += 1
            }
        }
        if removed > 0 { print("[MergeDefaults] categories: removed \(removed)") }
        return removed
    }

    // MARK: - Save Context

    func save() {
        let context = viewContext
        guard context.hasChanges else { return }

        do {
            try context.save()
        } catch {
            let nsError = error as NSError
            print("Core Data save error: \(nsError), \(nsError.userInfo)")
        }
    }

    // MARK: - Background Context

    func newBackgroundContext() -> NSManagedObjectContext {
        let context = persistentContainer.newBackgroundContext()
        context.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy
        context.undoManager = nil
        return context
    }

    func performBackgroundTask(_ block: @escaping (NSManagedObjectContext) -> Void) {
        persistentContainer.performBackgroundTask(block)
    }

    // MARK: - Remote Change Handling

    @objc private func processRemoteChanges(_ notification: Notification) {
        DispatchQueue.main.async { [weak self] in
            guard let self else { return }
            // Force viewContext to re-read all objects from the persistent store.
            self.viewContext.refreshAllObjects()
            // Remove any duplicates that CloudKit import may have introduced.
            // This handles the first-time sync case where records existed locally before
            // CloudKit was enabled: the initial export+import creates duplicate objects.
            let removed = self.cleanupDuplicateObjects()
            if removed > 0 {
                print("[RemoteChanges] Removed \(removed) duplicate objects after CloudKit import")
            }
            // Merge default duplicates after each import (CloudKit-safe via Nullify
            // rules + deterministic winner → devices converge, no cascade wipes).
            let mergedDefaults = self.mergeDefaultDuplicates()
            if mergedDefaults > 0 {
                print("[RemoteChanges] Merged \(mergedDefaults) default duplicates after CloudKit import")
            }
            // Notify repositories to re-fetch unconditionally.
            NotificationCenter.default.post(name: .cloudKitForceReload, object: nil)
            self.objectWillChange.send()
            self.save()
            self.refreshWidgetData()
        }
    }

    @objc private func cloudKitEventChanged(_ notification: Notification) {
        guard let event = notification.userInfo?[NSPersistentCloudKitContainer.eventNotificationUserInfoKey]
                as? NSPersistentCloudKitContainer.Event else { return }
        DispatchQueue.main.async { [weak self] in
            guard let self else { return }
            let isActive = event.endDate == nil
            self.isSyncing = isActive
            if !isActive {
                if event.succeeded, let endDate = event.endDate {
                    self.lastSyncError = nil
                    switch event.type {
                    case .import: self.lastImportDate = endDate
                    case .export: self.lastExportDate = endDate
                    default: break
                    }
                } else if let error = event.error {
                    let typeLabel = event.type == .import ? "import" : event.type == .export ? "export" : "setup"
                    self.lastSyncError = "\(typeLabel): \(Self.describeError(error))"
                    self.lastSyncErrorDetail = "\(typeLabel)\n\(Self.deepErrorReport(error))"
                    self.lastSyncErrorHint = Self.hint(for: error)
                    // Severity: a partial failure AFTER sync has worked at least
                    // once is background noise (a subset of records CloudKit
                    // retries), NOT a broken-sync alarm. Only a total failure with
                    // no data ever synced is critical.
                    let hasSyncedBefore = self.lastImportDate != nil || self.lastExportDate != nil
                    let isPartial = (error as NSError).code == 2  // CKErrorPartialFailure
                    self.syncErrorIsCritical = !(hasSyncedBefore || isPartial)
                    print("CloudKit \(typeLabel) full error:\n\(error)\nuserInfo: \((error as NSError).userInfo)")
                }
            }
        }
    }

    private static func describeError(_ error: Error, depth: Int = 0) -> String {
        guard depth < 3 else { return "…" }
        let ns = error as NSError
        var parts: [String] = ["\(ns.domain)(\(ns.code))"]
        // At depth 0, always include the localised description so the user sees
        // a human-readable message even when userInfo has no other keys.
        if depth == 0, let msg = ns.userInfo[NSLocalizedDescriptionKey] as? String {
            parts.append(msg)
        }
        for (key, value) in ns.userInfo {
            let k = "\(key)"
            if k == NSLocalizedDescriptionKey || k == "NSLocalizedDescription" { continue }
            if let nestedError = value as? Error {
                parts.append("\(k):\(describeError(nestedError, depth: depth + 1))")
            } else if let dict = value as? [AnyHashable: Any], !dict.isEmpty {
                let pairs = dict.prefix(3).map { kk, vv -> String in
                    if let e = vv as? Error { return "\(kk)→\(describeError(e, depth: depth + 1))" }
                    return "\(kk)=\(vv)"
                }
                parts.append("\(k){\(pairs.joined(separator: ", "))}")
            } else if !(value is [AnyHashable: Any]) {
                parts.append("\(k)=\(value)")
            }
        }
        return parts.joined(separator: "\n")
    }

    /// Turns an opaque CloudKit error into a human-readable, actionable hint by
    /// digging into CKPartialErrorsByItemIDKey — the per-record failures hidden
    /// inside a CKErrorPartialFailure (code 2). The dominant underlying code
    /// tells us the real problem: schema not deployed (unknownItem/invalidArguments)
    /// vs. quota vs. transient network.
    static func hint(for error: Error) -> String? {
        let ns = error as NSError
        // Collect all leaf CKError codes across a possible partial-failure tree.
        var codes: [Int] = []
        func collect(_ e: NSError) {
            if e.domain == "CKErrorDomain", e.code != 2 { codes.append(e.code) }
            if let partial = e.userInfo["CKPartialErrorsByItemIDKey"] as? [AnyHashable: Any] {
                for case let sub as NSError in partial.values { collect(sub) }
            }
            for value in e.userInfo.values {
                if let sub = value as? NSError, sub !== e { collect(sub) }
            }
        }
        collect(ns)

        // CKError codes: 14 = unknownItem, 12 = invalidArguments, 6 = partialFailure,
        // 25 = quotaExceeded, 4 = networkFailure/unavailable, 3 = networkUnavailable,
        // 15 = serverRejectedRequest, 26 = operationCancelled.
        if codes.contains(14) || codes.contains(12) || codes.contains(15) {
            return String(localized: "icloud_hint_schema")
        }
        if codes.contains(25) {
            return String(localized: "icloud_hint_quota")
        }
        if codes.contains(3) || codes.contains(4) {
            return String(localized: "icloud_hint_network")
        }
        if ns.code == 2 {
            return String(localized: "icloud_hint_partial_generic")
        }
        return nil
    }

    /// Full recursive walk of a CloudKit/Core Data error tree. Unlike `describeError`
    /// (a compact one-liner), this follows NSUnderlyingError chains and
    /// CKPartialErrorsByItemIDKey, and pulls the failing record TYPE out of any
    /// embedded CKRecord — which is what tells us WHICH entity CloudKit rejects.
    static func deepErrorReport(_ error: Error) -> String {
        var lines: [String] = []
        var leafCodes = Set<Int>()
        var recordTypes = Set<String>()
        var visited = 0

        func walk(_ err: Error, indent: Int) {
            guard visited < 300 else { return }
            visited += 1
            let ns = err as NSError
            let pad = String(repeating: "  ", count: indent)
            lines.append("\(pad)\(ns.domain)(\(ns.code))")
            if ns.domain == "CKErrorDomain", ns.code != 2 { leafCodes.insert(ns.code) }

            let info = ns.userInfo
            if let reason = info[NSLocalizedFailureReasonErrorKey] as? String {
                lines.append("\(pad)  reason: \(reason)")
            }
            if let desc = info[NSLocalizedDescriptionKey] as? String {
                lines.append("\(pad)  desc: \(desc)")
            }
            if let retry = info["CKErrorRetryAfterKey"] {
                lines.append("\(pad)  retryAfter: \(retry)")
            }
            for key in ["CKRecordChangedErrorServerRecordKey",
                        "CKRecordChangedErrorClientRecordKey",
                        "CKRecordChangedErrorAncestorRecordKey"] {
                if let rec = info[key] as? CKRecord {
                    recordTypes.insert(rec.recordType)
                    lines.append("\(pad)  record: \(rec.recordType) [\(rec.recordID.recordName)]")
                }
            }
            if let partial = info["CKPartialErrorsByItemIDKey"] as? [AnyHashable: Any] {
                lines.append("\(pad)  partialErrors: \(partial.count)")
                for (rid, value) in partial.prefix(25) {
                    if let name = (rid as? CKRecord.ID)?.recordName {
                        lines.append("\(pad)    item: \(name)")
                    }
                    if let sub = value as? Error { walk(sub, indent: indent + 3) }
                }
            }
            if let underlying = info[NSUnderlyingErrorKey] as? Error {
                lines.append("\(pad)  underlying:")
                walk(underlying, indent: indent + 2)
            }
            for (k, v) in info {
                let ks = "\(k)"
                if ks == NSUnderlyingErrorKey || ks == "CKPartialErrorsByItemIDKey" { continue }
                if let sub = v as? Error, (sub as NSError) !== ns {
                    lines.append("\(pad)  [\(ks)]:")
                    walk(sub, indent: indent + 2)
                }
            }
            let keys = info.keys.map { "\($0)" }.sorted()
            if !keys.isEmpty { lines.append("\(pad)  keys: \(keys.joined(separator: ", "))") }
        }

        walk(error, indent: 0)

        var summary = ""
        if !leafCodes.isEmpty {
            summary += "leafCKCodes: [\(leafCodes.sorted().map(String.init).joined(separator: ", "))]\n"
        }
        if !recordTypes.isEmpty {
            summary += "recordTypes: [\(recordTypes.sorted().joined(separator: ", "))]\n"
        }
        return summary + lines.joined(separator: "\n")
    }

    /// Local Core Data integrity probe: per-entity counts + records with nil id /
    /// nil createdAt / orphan relationships that can silently block a CloudKit export.
    func integrityReport() -> String {
        let ctx = viewContext
        var lines: [String] = []
        let entities = ["Account", "Category", "InvestmentSource", "Snapshot", "Goal", "JournalEntry"]
        for name in entities {
            let count = (try? ctx.count(for: NSFetchRequest<NSManagedObject>(entityName: name))) ?? -1
            lines.append("\(name): \(count)")
        }
        func flag(_ label: String, _ n: Int) { if n > 0 { lines.append("⚠︎ \(label): \(n)") } }
        func fetch(_ name: String) -> [NSManagedObject] {
            (try? ctx.fetch(NSFetchRequest<NSManagedObject>(entityName: name))) ?? []
        }
        let sources = fetch("InvestmentSource")
        flag("sources nil id", sources.filter { $0.value(forKey: "id") == nil }.count)
        flag("sources nil createdAt", sources.filter { $0.value(forKey: "createdAt") == nil }.count)
        let snaps = fetch("Snapshot")
        flag("snapshots nil id", snaps.filter { $0.value(forKey: "id") == nil }.count)
        flag("snapshots nil createdAt", snaps.filter { $0.value(forKey: "createdAt") == nil }.count)
        flag("orphan snapshots (nil source)", snaps.filter { $0.value(forKey: "source") == nil }.count)
        let goals = fetch("Goal")
        flag("goals nil id", goals.filter { $0.value(forKey: "id") == nil }.count)
        flag("goals nil createdAt", goals.filter { $0.value(forKey: "createdAt") == nil }.count)
        return lines.joined(separator: "\n")
    }

    func forceReload() {
        viewContext.perform { [weak self] in
            self?.viewContext.refreshAllObjects()
            DispatchQueue.main.async {
                NotificationCenter.default.post(name: .cloudKitForceReload, object: nil)
            }
        }
    }

    /// Forces NSPersistentCloudKitContainer to export all local data to iCloud.
    ///
    /// Strategy: advance `createdAt` by 1 ms for every record.  This guarantees
    /// a *real* value change that the SQLite persistent store will write as a
    /// persistent-history transaction — which is what NSPersistentCloudKitContainer
    /// needs to discover records and enqueue them for CloudKit export.
    ///
    /// Setting a property to the *same* value may be silently discarded by the
    /// SQLite layer (no SQL UPDATE issued → no history entry → nothing to export).
    func forceExportToiCloud(completion: @escaping (Int) -> Void) {
        guard Self.cloudKitEnabled else { completion(0); return }
        let entities = ["Account", "Category", "InvestmentSource", "Snapshot", "Goal"]
        let context = newBackgroundContext()
        context.perform {
            var totalTouched = 0
            for entityName in entities {
                let request = NSFetchRequest<NSManagedObject>(entityName: entityName)
                request.fetchBatchSize = 50
                guard let objects = try? context.fetch(request) else { continue }
                for object in objects {
                    // Advance createdAt by 1 ms → always a genuine value change.
                    let t = (object.value(forKey: "createdAt") as? Date) ?? Date()
                    object.setValue(t.addingTimeInterval(0.001), forKey: "createdAt")
                    totalTouched += 1
                }
            }
            if context.hasChanges {
                try? context.save()
            }
            DispatchQueue.main.async {
                completion(totalTouched)
            }
        }
    }

    /// Forces an immediate re-read of all Core Data objects from the persistent store.
    /// Call this when the app returns to the foreground so any iCloud changes made on
    /// other devices (while this device was inactive) are picked up right away.
    func refreshFromCloudKit() {
        guard Self.cloudKitEnabled else { return }
        viewContext.perform { [weak self] in
            self?.viewContext.refreshAllObjects()
        }
    }

    // MARK: - Widget Data Refresh

    /// When true, `refreshWidgetData()` becomes a no-op. Set during batch operations
    /// (e.g. CSV import of hundreds of snapshots) so we don't run a synchronous WAL
    /// checkpoint + widget reload per row — that hammered the main thread into an ANR.
    /// Call `refreshWidgetData()` once when the batch finishes.
    var suppressWidgetRefresh = false

    func refreshWidgetData() {
        if suppressWidgetRefresh { return }
        if #available(iOS 14.0, *) {
            if Self.appGroupEnabled {
                checkpointWAL()
                WidgetCenter.shared.reloadAllTimelines()
            }
        }
        // The paired watch reads the same data changes; every repository that
        // refreshes the widget wants the watch refreshed too.
        Task { @MainActor in
            WatchSyncService.shared.scheduleSync()
        }
    }

    /// Forces SQLite to checkpoint the WAL file, ensuring all changes are written to the main database file.
    /// This is necessary for the widget to see changes, as it opens the database read-only.
    private func checkpointWAL() {
        viewContext.performAndWait {
            if viewContext.hasChanges {
                try? viewContext.save()
            }
            viewContext.refreshAllObjects()
        }
    }

}

// MARK: - Shared Container for Widgets

extension CoreDataStack {
    static var sharedStoreURL: URL? {
        guard appGroupEnabled else {
            let fallbackURL = NSPersistentContainer.defaultDirectoryURL()
                .appendingPathComponent("PortfolioJournal.sqlite")
            return fallbackURL
        }

        if let appGroupURL = FileManager.default
            .containerURL(forSecurityApplicationGroupIdentifier: appGroupIdentifier)?
            .appendingPathComponent("PortfolioJournal.sqlite") {
            return appGroupURL
        }

        let fallbackURL = NSPersistentContainer.defaultDirectoryURL()
            .appendingPathComponent("PortfolioJournal.sqlite")
        print("App Group unavailable for widgets; using default store URL: \(fallbackURL)")
        return fallbackURL
    }

    /// Creates a lightweight Core Data stack for widgets (read-only)
    static func createWidgetContainer() -> NSPersistentContainer {
        let container = NSPersistentContainer(name: "PortfolioJournal")

        guard let storeURL = sharedStoreURL else {
            fatalError("Unable to get shared store URL")
        }

        let description = NSPersistentStoreDescription(url: storeURL)
        description.isReadOnly = true
        description.shouldMigrateStoreAutomatically = true
        description.shouldInferMappingModelAutomatically = true

        container.persistentStoreDescriptions = [description]

        container.loadPersistentStores { _, error in
            if let error = error {
                print("Widget Core Data failed: \(error)")
            }
        }

        return container
    }
}