import SwiftUI
import Combine

enum SortOption: String, CaseIterable {
    case dateAdded = "Date Added"
    case valueHighLow = "Value (High-Low)"
    case nameAZ = "Name (A-Z)"
}

// MARK: - COLLECTION VIEW MODEL
// Owns all collection state: list management, filtering, sorting, pricing, persistence.
// Primary sync: SwiftData + CloudKit (via PersistenceController).
// Secondary backup: Firebase — user-triggered, metadata only, no images.
@MainActor
class CollectionViewModel: ObservableObject {
    @Published var scannedList: [SavedCard] = [] {
        didSet { recalcStats() }
    }
    @Published var collections: [String] = [AppConfig.Defaults.masterCollectionName]
    @Published var boxes: [String] = [AppConfig.Defaults.unsortedBoxName]

    @Published var currentCollection: String = AppConfig.Defaults.masterCollectionName {
        didSet { librarySearchText = ""; recalcStats() }
    }
    @Published var currentBox: String = AppConfig.Defaults.unsortedBoxName
    @Published var sortOption: SortOption = .dateAdded
    @Published var librarySearchText = "" {
        didSet { recalcStats() }
    }
    @Published var isConnected = true
    @Published var selectedCurrency: CurrencyCode = AppConfig.defaultCurrency

    @Published var filteredList: [SavedCard] = []
    @Published var totalValue: Double = 0.0

    // Dashboard Stats
    @Published var portfolioValue: Double = 0.0
    @Published var portfolioDailyChange: Double = 0.0
    @Published var topMovers: [SavedCard] = []

    @Published var isCollectionLoading = true
    @Published var isRefreshingPrices = false
    @Published var isBackingUpToFirebase = false

    private var cancellables = Set<AnyCancellable>()
    private var recalcTask: Task<Void, Never>?
    private var refreshTask: Task<Void, Never>?
    private var saveTask: Task<Void, Never>?

    init() {
        NetworkMonitor.shared.$isConnected
            .receive(on: RunLoop.main)
            .sink { [weak self] status in self?.isConnected = status }
            .store(in: &cancellables)

        Task { [weak self] in
            // One-time JSON → SwiftData migration, then load
            await PersistenceController.shared.backgroundActor.migrateFromJSONIfNeeded()
            let loaded = await PersistenceController.shared.backgroundActor.load()
            guard let self = self else { return }
            self.scannedList = loaded
            self.isCollectionLoading = false

            let loadedCollections = Set(loaded.map { $0.collectionName })
            let loadedBoxes = Set(loaded.map { $0.storageLocation })
            self.collections = Array(loadedCollections.union([AppConfig.Defaults.masterCollectionName])).sorted()
            self.boxes = Array(loadedBoxes.union([AppConfig.Defaults.unsortedBoxName])).sorted()

            Task.detached {
                let activeImages = Set(loaded.map { $0.imageFileName })
                ImageManager.cleanupOrphans(activeImages: activeImages)
            }
            self.refreshPrices(force: false)
        }
    }

    // MARK: - Stats & Filtering

    func recalcStats() {
        let currentColl = self.currentCollection
        let searchText = self.librarySearchText.lowercased()
        let sort = self.sortOption
        let sourceList = self.scannedList

        recalcTask?.cancel()
        recalcTask = Task.detached { [weak self] in
            let filtered = sourceList.filter { card in
                (searchText.isEmpty ||
                 card.name.localizedCaseInsensitiveContains(searchText) ||
                 card.setCode.localizedCaseInsensitiveContains(searchText) ||
                 card.collectorNumber.localizedCaseInsensitiveContains(searchText)) &&
                (currentColl == AppConfig.Defaults.masterCollectionName || card.collectionName == currentColl)
            }

            let sorted: [SavedCard]
            switch sort {
            case .dateAdded: sorted = filtered.sorted { $0.dateAdded > $1.dateAdded }
            case .valueHighLow: sorted = filtered.sorted { ($0.currentValuation ?? 0) > ($1.currentValuation ?? 0) }
            case .nameAZ: sorted = filtered.sorted { $0.name < $1.name }
            }

            let total = filtered.reduce(0) { $0 + ($1.currentValuation ?? 0) }

            let globalTotal = sourceList.reduce(0) { $0 + ($1.currentValuation ?? 0) }
            let globalPrev = sourceList.reduce(0) { $0 + ($1.previousValuation ?? $1.currentValuation ?? 0) }
            let dailyChange = globalTotal - globalPrev

            let movers = sourceList.filter { ($0.currentValuation ?? 0) != ($0.previousValuation ?? 0) }
                .sorted { abs(($0.currentValuation ?? 0) - ($0.previousValuation ?? 0)) > abs(($1.currentValuation ?? 0) - ($1.previousValuation ?? 0)) }
                .prefix(5)

            if Task.isCancelled { return }
            await MainActor.run { [weak self] in
                guard let self = self else { return }
                self.filteredList = sorted
                self.totalValue = total
                self.portfolioValue = globalTotal
                self.portfolioDailyChange = dailyChange
                self.topMovers = Array(movers)
            }
        }
    }

    // MARK: - Pricing

    func refreshPrices(force: Bool = false) {
        refreshTask?.cancel()
        self.isRefreshingPrices = true
        let cardsSnapshot = self.scannedList
        let currencySnapshot = self.selectedCurrency

        refreshTask = Task.detached { [weak self] in
            let (priceUpdates, metadataUpdates) = await ScryfallAPI.updateTrends(cards: cardsSnapshot, currency: currencySnapshot, force: force)
            await MainActor.run { [weak self] in
                guard let self = self else { return }
                self.isRefreshingPrices = false
                if priceUpdates.isEmpty && metadataUpdates.isEmpty { return }

                var listCopy = self.scannedList
                var changedIndices = Set<Int>()
                var hasChanges = false

                var indexMap = [UUID: Int]()
                for (index, card) in listCopy.enumerated() { indexMap[card.id] = index }

                for (id, newPrice) in priceUpdates {
                    if let index = indexMap[id] {
                        let oldCurrency = listCopy[index].currencyCode
                        let oldPrice = listCopy[index].currentValuation

                        if oldCurrency != currencySnapshot.rawValue {
                            listCopy[index].previousValuation = newPrice
                            listCopy[index].currentValuation = newPrice
                            listCopy[index].currencyCode = currencySnapshot.rawValue
                            changedIndices.insert(index)
                            hasChanges = true
                        } else if oldPrice != newPrice {
                            listCopy[index].previousValuation = oldPrice
                            listCopy[index].currentValuation = newPrice
                            changedIndices.insert(index)
                            hasChanges = true
                        }
                    }
                }

                for (id, meta) in metadataUpdates {
                    if let index = indexMap[id] {
                        if listCopy[index].rarity != meta.0 || listCopy[index].colorIdentity != meta.1 || (meta.2 && listCopy[index].isSerialized != true) {
                            listCopy[index].rarity = meta.0
                            listCopy[index].colorIdentity = meta.1
                            if meta.2 { listCopy[index].isSerialized = true }
                            changedIndices.insert(index)
                            hasChanges = true
                        }
                    }
                }

                if hasChanges {
                    self.scannedList = listCopy
                    self.saveCollectionAsync()
                }
            }
        }
    }

    // MARK: - Collection Mutations

    func addCard(_ entry: SavedCard, cgImage: CGImage, uiImage: UIImage, autoScan: Bool) {
        self.scannedList.insert(entry, at: 0)
        self.saveCollectionAsync()
        ReviewEngine.logScan()

        var taskID = UIBackgroundTaskIdentifier.invalid
        taskID = UIApplication.shared.beginBackgroundTask(withName: "SaveCard") {
            UIApplication.shared.endBackgroundTask(taskID)
            taskID = .invalid
        }

        Task.detached(priority: .userInitiated) { [weak self, taskID] in
            defer { UIApplication.shared.endBackgroundTask(taskID) }
            do {
                try ImageManager.save(uiImage, name: entry.imageFileName)
            } catch {
                print("Warning: Image Save Failed")
            }

            guard let self = self else { return }

            if entry.currentValuation == nil {
                let currency = await MainActor.run { self.selectedCurrency }
                let (prices, metadata) = await ScryfallAPI.updateTrends(cards: [entry], currency: currency, force: true, updateTimestamp: false)
                if let newPrice = prices[entry.id] {
                    await MainActor.run {
                        guard let self = self else { return }
                        if let idx = self.scannedList.firstIndex(where: { $0.id == entry.id }) {
                            self.scannedList[idx].currentValuation = newPrice
                            if let meta = metadata[entry.id] {
                                self.scannedList[idx].rarity = meta.0
                                self.scannedList[idx].colorIdentity = meta.1
                                if meta.2 { self.scannedList[idx].isSerialized = true }
                            }
                            self.saveCollectionAsync()
                        }
                    }
                }
            }
        }
    }

    func updateCardDetails(_ card: SavedCard) {
        if let idx = scannedList.firstIndex(where: { $0.id == card.id }) {
            scannedList[idx] = card

            if !collections.contains(card.collectionName) { collections.append(card.collectionName); collections.sort() }
            if !boxes.contains(card.storageLocation) { boxes.append(card.storageLocation); boxes.sort() }

            self.saveCollectionAsync()

            var taskID = UIBackgroundTaskIdentifier.invalid
            taskID = UIApplication.shared.beginBackgroundTask(withName: "UpdateCard") {
                UIApplication.shared.endBackgroundTask(taskID)
                taskID = .invalid
            }

            Task.detached(priority: .userInitiated) { [weak self, taskID] in
                defer { UIApplication.shared.endBackgroundTask(taskID) }
                guard let self = self else { return }
                let currency = await MainActor.run { self.selectedCurrency }
                let (prices, _) = await ScryfallAPI.updateTrends(cards: [card], currency: currency, force: true, updateTimestamp: false)
                if let newPrice = prices[card.id] {
                    await MainActor.run {
                        guard let self = self else { return }
                        if let i = self.scannedList.firstIndex(where: { $0.id == card.id }) {
                            self.scannedList[i].currentValuation = newPrice
                            self.saveCollectionAsync()
                        }
                    }
                }
            }
        }
    }

    func moveCard(_ card: SavedCard, toCollection: String, toBox: String) {
        if let idx = scannedList.firstIndex(of: card) {
            scannedList[idx].collectionName = toCollection
            scannedList[idx].storageLocation = toBox
            self.saveCollectionAsync()
        }
    }

    func deleteCard(_ card: SavedCard) {
        if let idx = scannedList.firstIndex(where: { $0.id == card.id }) {
            let fileName = scannedList[idx].imageFileName
            Task { await ImageManager.delete(name: fileName) }
            Task { await CloudEngine.delete(card: card) }
            scannedList.remove(at: idx)
            self.saveCollectionAsync()
        }
    }

    func saveManualCard(_ card: SavedCard) {
        self.scannedList.insert(card, at: 0)
        self.saveCollectionAsync()
        ReviewEngine.logScan()

        var taskID = UIBackgroundTaskIdentifier.invalid
        taskID = UIApplication.shared.beginBackgroundTask(withName: "SaveManual") {
            UIApplication.shared.endBackgroundTask(taskID)
            taskID = .invalid
        }

        Task.detached(priority: .userInitiated) { [weak self, taskID] in
            defer { UIApplication.shared.endBackgroundTask(taskID) }
            guard let self = self else { return }
            let currency = await MainActor.run { self.selectedCurrency }
            let (prices, metadata) = await ScryfallAPI.updateTrends(cards: [card], currency: currency, force: true, updateTimestamp: false)

            if let newPrice = prices[card.id] {
                await MainActor.run { [weak self] in
                    guard let self = self else { return }
                    if let idx = self.scannedList.firstIndex(where: { $0.id == card.id }) {
                        self.scannedList[idx].currentValuation = newPrice
                        if let meta = metadata[card.id] {
                            self.scannedList[idx].rarity = meta.0
                            self.scannedList[idx].colorIdentity = meta.1
                            if meta.2 { self.scannedList[idx].isSerialized = true }
                        }
                        self.saveCollectionAsync()
                    }
                }
            }
        }
    }

    // MARK: - Export

    func exportCollection(format: ExportFormat) async -> URL? {
        let list = self.scannedList
        return await Task.detached { ExportEngine.generate(cards: list, format: format) }.value
    }

    func copyToClipboard(format: ExportFormat) {
        let text = ExportEngine.generateString(cards: self.scannedList, format: format)
        UIPasteboard.general.string = text
    }

    func generateShareImage(for card: SavedCard) async -> UIImage? {
        let currencySymbol = self.selectedCurrency.symbol
        return await Task.detached {
            let renderer = UIGraphicsImageRenderer(size: CGSize(width: 1080, height: 1080))
            return renderer.image { ctx in
                UIColor.black.setFill()
                ctx.fill(CGRect(x: 0, y: 0, width: 1080, height: 1080))
                if let img = ImageManager.load(name: card.imageFileName) { img.draw(in: CGRect(x: 140, y: 180, width: 800, height: 800)) }
                if let watermark = UIImage(named: "share_watermark") { watermark.draw(in: CGRect(x: 340, y: 990, width: 400, height: 80)) }
                else { "Verified by IYmtg".draw(at: CGPoint(x: 100, y: 1000), withAttributes: [.font: UIFont.systemFont(ofSize: 40), .foregroundColor: UIColor.gray]) }
                let price = "\(currencySymbol)\(card.currentValuation ?? 0.0)" as NSString
                price.draw(at: CGPoint(x: 100, y: 40), withAttributes: [.font: UIFont.systemFont(ofSize: 120, weight: .bold), .foregroundColor: UIColor.green])
            }
        }.value
    }

    // MARK: - Firebase Backup (manual, metadata only)

    /// Pushes all card metadata to Firebase Firestore as a secondary disaster-recovery backup.
    /// Does NOT include card images (those remain in iCloud Drive).
    /// Primary sync is handled automatically by SwiftData + CloudKit.
    func backupAllToFirebase() {
        guard !isBackingUpToFirebase else { return }
        isBackingUpToFirebase = true
        let snapshot = self.scannedList

        Task { [weak self] in
            CloudEngine.signInSilently()
            for card in snapshot {
                await CloudEngine.save(card: card)
            }
            await MainActor.run { [weak self] in
                self?.isBackingUpToFirebase = false
            }
        }
    }

    // MARK: - Persistence

    func forceSave() {
        saveTask?.cancel()
        let listSnapshot = self.scannedList
        Task { await PersistenceController.shared.backgroundActor.save(listSnapshot) }
    }

    func saveCollectionAsync() {
        saveTask?.cancel()
        let listSnapshot = self.scannedList
        saveTask = Task {
            do {
                try await Task.sleep(nanoseconds: 500_000_000)
                if !Task.isCancelled {
                    await PersistenceController.shared.backgroundActor.save(listSnapshot)
                }
            } catch {}
        }
    }
}