import Combine
import CoreData
import Foundation
import Swinject
import WatchConnectivity

protocol WatchManager {}

final class BaseWatchManager: NSObject, WatchManager, Injectable {
    private let session: WCSession
    private var state = WatchState()
    private let processQueue = DispatchQueue(label: "BaseWatchManager.processQueue")

    @Injected() private var broadcaster: Broadcaster!
    @Injected() private var settingsManager: SettingsManager!
    @Injected() private var apsManager: APSManager!
    @Injected() private var storage: FileStorage!
    @Injected() private var carbsStorage: CarbsStorage!
    @Injected() private var tempTargetsStorage: TempTargetsStorage!
    @Injected() private var garmin: GarminManager!
    @Injected() private var glucoseStorage: GlucoseStorage!

    private var glucoseFormatter: NumberFormatter {
        let formatter = NumberFormatter()
        formatter.numberStyle = .decimal
        formatter.maximumFractionDigits = 0
        if settingsManager.settings.units == .mmolL {
            formatter.minimumFractionDigits = 1
            formatter.maximumFractionDigits = 1
        }
        formatter.roundingMode = .halfUp
        return formatter
    }

    private var eventualFormatter: NumberFormatter {
        let formatter = NumberFormatter()
        formatter.numberStyle = .decimal
        formatter.maximumFractionDigits = 1
        return formatter
    }

    private var deltaFormatter: NumberFormatter {
        let formatter = NumberFormatter()
        formatter.numberStyle = .decimal
        formatter.maximumFractionDigits = settingsManager.settings.units == .mmolL ? 1 : 0
        formatter.positivePrefix = "+"
        formatter.negativePrefix = "-"
        return formatter
    }

    private var targetFormatter: NumberFormatter {
        let formatter = NumberFormatter()
        formatter.numberStyle = .decimal
        formatter.maximumFractionDigits = 1
        return formatter
    }

    let context = CoreDataStack.shared.newTaskContext()
    let viewContext = CoreDataStack.shared.persistentContainer.viewContext

    private var coreDataPublisher: AnyPublisher<Set<NSManagedObject>, Never>?
    private var subscriptions = Set<AnyCancellable>()

    private var lifetime = Lifetime()

    init(resolver: Resolver, session: WCSession = .default) {
        self.session = session
        super.init()
        injectServices(resolver)
        registerHandlers()
        registerSubscribers()

        coreDataPublisher =
            changedObjectsOnManagedObjectContextDidSavePublisher()
                .receive(on: DispatchQueue.global(qos: .background))
                .share()
                .eraseToAnyPublisher()

        Task {
            await configureState()
        }

        if WCSession.isSupported() {
            session.delegate = self
            session.activate()
        }

        broadcaster.register(SettingsObserver.self, observer: self)
        broadcaster.register(PumpHistoryObserver.self, observer: self)
        broadcaster.register(PumpSettingsObserver.self, observer: self)
        broadcaster.register(BasalProfileObserver.self, observer: self)
        broadcaster.register(TempTargetsObserver.self, observer: self)
        broadcaster.register(CarbsObserver.self, observer: self)
        broadcaster.register(PumpBatteryObserver.self, observer: self)
        broadcaster.register(PumpReservoirObserver.self, observer: self)
        garmin.stateRequet = { [weak self] () -> Data in
            guard let self = self, let data = try? JSONEncoder().encode(self.state) else {
                warning(.service, "Cannot encode watch state")
                return Data()
            }
            return data
        }
    }

    private func registerSubscribers() {
        glucoseStorage.updatePublisher
            .receive(on: DispatchQueue.global(qos: .background))
            .sink { [weak self] _ in
                guard let self = self else { return }
                Task {
                    await self.configureState()
                }
            }
            .store(in: &subscriptions)
    }

    private func registerHandlers() {
        coreDataPublisher?.filterByEntityName("OrefDetermination").sink { [weak self] _ in
            guard let self = self else { return }
            Task {
                await self.configureState()
            }
        }.store(in: &subscriptions)

        coreDataPublisher?.filterByEntityName("OverrideStored").sink { [weak self] _ in
            guard let self = self else { return }
            Task {
                await self.configureState()
            }
        }.store(in: &subscriptions)

        // Observes Deletion of Glucose Objects
        coreDataPublisher?.filterByEntityName("GlucoseStored").sink { [weak self] _ in
            guard let self = self else { return }
            Task {
                await self.configureState()
            }
        }.store(in: &subscriptions)
    }

    private func fetchlastDetermination() async -> [NSManagedObjectID] {
        let results = await CoreDataStack.shared.fetchEntitiesAsync(
            ofType: OrefDetermination.self,
            onContext: context,
            predicate: NSPredicate.enactedDetermination,
            key: "timestamp",
            ascending: false,
            fetchLimit: 1
        )

        return await context.perform {
            guard let fetchedResults = results as? [OrefDetermination] else { return [] }

            return fetchedResults.map(\.objectID)
        }
    }

    private func fetchLatestOverride() async -> NSManagedObjectID? {
        let results = await CoreDataStack.shared.fetchEntitiesAsync(
            ofType: OverrideStored.self,
            onContext: context,
            predicate: NSPredicate.predicateForOneDayAgo,
            key: "date",
            ascending: false,
            fetchLimit: 1,
            propertiesToFetch: ["enabled", "percentage", "objectID"]
        )

        return await context.perform {
            guard let fetchedResults = results as? [[String: Any]] else { return nil }

            return fetchedResults.compactMap { $0["objectID"] as? NSManagedObjectID }.first
        }
    }

    private func fetchGlucose() async -> [NSManagedObjectID] {
        let results = await CoreDataStack.shared.fetchEntitiesAsync(
            ofType: GlucoseStored.self,
            onContext: context,
            predicate: NSPredicate.predicateFor120MinAgo,
            key: "date",
            ascending: false,
            fetchLimit: 24,
            batchSize: 12
        )

        return await context.perform {
            guard let glucoseResults = results as? [GlucoseStored] else {
                return []
            }

            return glucoseResults.map(\.objectID)
        }
    }

    @MainActor private func configureState() async {
        let glucoseValuesIds = await fetchGlucose()
        async let getLatestDeterminationIds = fetchlastDetermination()
        async let getlatestOverrideId = fetchLatestOverride()

        let latestOverrideId = await getlatestOverrideId

        guard let lastDeterminationId = await getLatestDeterminationIds.first else {
            debugPrint("\(DebuggingIdentifiers.failed) \(#file) \(#function) Failed to get last Determination")
            return
        }

        do {
            let glucoseValues: [GlucoseStored] = await CoreDataStack.shared
                .getNSManagedObject(with: glucoseValuesIds, context: viewContext)
            let lastDetermination = try viewContext.existingObject(with: lastDeterminationId) as? OrefDetermination
            let recommendedInsulin = await newBolusCalc(
                glucoseIds: glucoseValuesIds,
                determinationId: lastDeterminationId
            )

            var latestOverride: OverrideStored?
            if let id = latestOverrideId {
                latestOverride = try viewContext.existingObject(with: id) as? OverrideStored
            }

            await MainActor.run { [weak self] in
                guard let self = self else { return }

                if let firstGlucoseValue = glucoseValues.first {
                    let value = self.settingsManager.settings.units == .mgdL
                        ? Decimal(firstGlucoseValue.glucose)
                        : Decimal(firstGlucoseValue.glucose).asMmolL

                    self.state.glucose = self.glucoseFormatter.string(from: value as NSNumber)
                    self.state.trend = firstGlucoseValue.directionEnum?.symbol

                    let delta = glucoseValues.count >= 2
                        ? Decimal(firstGlucoseValue.glucose) - Decimal(glucoseValues.dropFirst().first?.glucose ?? 0)
                        : 0
                    let deltaConverted = self.settingsManager.settings.units == .mgdL ? delta : delta.asMmolL
                    self.state.delta = self.deltaFormatter.string(from: deltaConverted as NSNumber)
                    self.state.trendRaw = firstGlucoseValue.direction
                    self.state.glucoseDate = firstGlucoseValue.date
                }

                self.state.lastLoopDate = lastDetermination?.timestamp
                self.state.lastLoopDateInterval = self.state.lastLoopDate.map {
                    guard $0.timeIntervalSince1970 > 0 else { return 0 }
                    return UInt64($0.timeIntervalSince1970)
                }
                self.state.bolusIncrement = self.settingsManager.preferences.bolusIncrement
                self.state.maxCOB = self.settingsManager.preferences.maxCOB
                self.state.maxBolus = self.settingsManager.pumpSettings.maxBolus
                self.state.carbsRequired = lastDetermination?.carbsRequired as? Decimal
                self.state.bolusRecommended = self.apsManager
                    .roundBolus(amount: max(recommendedInsulin, 0))
                self.state.displayOnWatch = self.settingsManager.settings.displayOnWatch
                self.state.displayFatAndProteinOnWatch = self.settingsManager.settings.displayFatAndProteinOnWatch
                self.state.confirmBolusFaster = self.settingsManager.settings.confirmBolusFaster

                self.state.iob = lastDetermination?.iob as? Decimal
                if let cobValue = lastDetermination?.cob {
                    self.state.cob = Decimal(cobValue)
                } else {
                    self.state.cob = 0
                }
                self.state.tempTargets = self.tempTargetsStorage.presets()
                    .map { target -> TempTargetWatchPreset in
                        let untilDate = self.tempTargetsStorage.current().flatMap { currentTarget -> Date? in
                            guard currentTarget.id == target.id else { return nil }
                            let date = currentTarget.createdAt.addingTimeInterval(TimeInterval(currentTarget.duration * 60))
                            return date > Date() ? date : nil
                        }
                        return TempTargetWatchPreset(
                            name: target.displayName,
                            id: target.id,
                            description: self.descriptionForTarget(target),
                            until: untilDate
                        )
                    }
                self.state.displayOnWatch = self.settingsManager.settings.displayOnWatch
                self.state.displayFatAndProteinOnWatch = self.settingsManager.settings.displayFatAndProteinOnWatch
                self.state.confirmBolusFaster = self.settingsManager.settings.confirmBolusFaster

                if let eventualBG = self.settingsManager.settings.units == .mgdL ? lastDetermination?
                    .eventualBG : lastDetermination?
                    .eventualBG?.decimalValue.asMmolL as NSDecimalNumber?
                {
                    let eventualBGAsString = self.eventualFormatter.string(from: eventualBG)
                    self.state.eventualBG = eventualBGAsString.map { "⇢ " + $0 }
                    self.state.eventualBGRaw = eventualBGAsString
                }

                self.state.isf = lastDetermination?.insulinSensitivity as? Decimal

                if let latestOverride = latestOverride {
                    if latestOverride.enabled {
                        let percentString = "\(latestOverride.percentage.formatted(.number)) %"
                        self.state.override = percentString
                    } else {
                        self.state.override = "100 %"
                    }
                }

                self.sendState()
            }

        } catch let error as NSError {
            debugPrint("\(DebuggingIdentifiers.failed) \(#file) \(#function) Failed to configure state with error: \(error)")
        }
    }

    private func sendState() {
        guard let data = try? JSONEncoder().encode(state) else {
            warning(.service, "Cannot encode watch state")
            return
        }

        garmin.sendState(data)

        guard session.isReachable else { return }
        session.sendMessageData(data, replyHandler: nil) { error in
            warning(.service, "Cannot send message to watch", error: error)
        }
    }

    private func descriptionForTarget(_ target: TempTarget) -> String {
        let units = settingsManager.settings.units

        var low = target.targetBottom
        var high = target.targetTop
        if units == .mmolL {
            low = low?.asMmolL
            high = high?.asMmolL
        }

        let description =
            "\(targetFormatter.string(from: (low ?? 0) as NSNumber)!) - \(targetFormatter.string(from: (high ?? 0) as NSNumber)!)" +
            " for \(targetFormatter.string(from: target.duration as NSNumber)!) min"

        return description
    }

    private func newBolusCalc(glucoseIds: [NSManagedObjectID], determinationId: NSManagedObjectID) async -> Decimal {
        await context.perform {
            let glucoseObjects = glucoseIds.compactMap { self.context.object(with: $0) as? GlucoseStored }
            guard let determination = self.context.object(with: determinationId) as? OrefDetermination else {
                print("Failed to fetch determination")
                return 0
            }

            guard let firstGlucose = glucoseObjects.first else {
                return 0 // If there's no glucose data, exit the block
            }
            let bg = firstGlucose.glucose // Make sure to provide a fallback value for glucose

            // Calculations related to glucose data
            var bgDelta: Int = 0
            if glucoseObjects.count >= 3 {
                bgDelta = Int(firstGlucose.glucose) - Int(glucoseObjects[2].glucose)
            }

            let conversion: Decimal = self.settingsManager.settings.units == .mmolL ? 0.0555 : 1
            let isf = self.state.isf ?? 0
            let target = determination.currentTarget as? Decimal ?? 100
            let carbratio = determination.carbRatio as? Decimal ?? 10
            let cob = self.state.cob ?? 0
            let iob = self.state.iob ?? 0
            let fattyMealFactor = self.settingsManager.settings.fattyMealFactor

            // Complete bolus calculation logic
            let targetDifference = Decimal(bg) - target
            let targetDifferenceInsulin = targetDifference * conversion / isf
            let fifteenMinInsulin = Decimal(bgDelta) * conversion / isf
            let wholeCobInsulin = cob / carbratio
            let iobInsulinReduction = -iob
            let wholeCalc = targetDifferenceInsulin + iobInsulinReduction + wholeCobInsulin + fifteenMinInsulin

            let result = wholeCalc * self.settingsManager.settings.overrideFactor
            var insulinCalculated: Decimal
            if self.settingsManager.settings.fattyMeals {
                insulinCalculated = result * fattyMealFactor
            } else {
                insulinCalculated = result
            }

            // Ensure the calculated insulin amount does not exceed the maximum bolus and is not below zero
            insulinCalculated = max(min(insulinCalculated, self.settingsManager.pumpSettings.maxBolus), 0)
            return insulinCalculated // Return the calculated insulin outside of the performAndWait block
        }
    }
}

extension BaseWatchManager: WCSessionDelegate {
    func sessionDidBecomeInactive(_: WCSession) {}

    func sessionDidDeactivate(_: WCSession) {}

    func session(_: WCSession, activationDidCompleteWith state: WCSessionActivationState, error _: Error?) {
        debug(.service, "WCSession is activated: \(state == .activated)")
    }

    func session(_: WCSession, didReceiveMessage message: [String: Any]) {
        debug(.service, "WCSession got message: \(message)")

        if let stateRequest = message["stateRequest"] as? Bool, stateRequest {
            processQueue.async {
                self.sendState()
            }
        }
    }

    func session(_: WCSession, didReceiveMessage message: [String: Any], replyHandler: @escaping ([String: Any]) -> Void) {
        debug(.service, "WCSession got message with reply handler: \(message)")

        if let carbs = message["carbs"] as? Double,
           let fat = message["fat"] as? Double,
           let protein = message["protein"] as? Double,
           carbs > 0 || fat > 0 || protein > 0
        {
            Task {
                await carbsStorage.storeCarbs(
                    [CarbsEntry(
                        id: UUID().uuidString,
                        createdAt: Date(),
                        actualDate: nil,
                        carbs: Decimal(carbs),
                        fat: Decimal(fat),
                        protein: Decimal(protein),
                        note: message["note"] as? String,
                        enteredBy: CarbsEntry.local,
                        isFPU: false,
                        fpuID: nil
                    )],
                    areFetchedFromRemote: false
                )

                _ = await apsManager.determineBasal()
                replyHandler(["confirmation": true])
            }
            return
        }

        if let tempTargetID = message["tempTarget"] as? String {
            Task {
                if var preset = tempTargetsStorage.presets().first(where: { $0.id == tempTargetID }) {
                    preset.createdAt = Date()
                    await tempTargetsStorage.storeTempTarget(tempTarget: preset)
                    replyHandler(["confirmation": true])
                } else if tempTargetID == "cancel" {
                    let entry = TempTarget(
                        name: TempTarget.cancel,
                        createdAt: Date(),
                        targetTop: 0,
                        targetBottom: 0,
                        duration: 0,
                        enteredBy: TempTarget.local,
                        reason: TempTarget.cancel,
                        isPreset: false,
                        enabled: false,
                        halfBasalTarget: 160
                    )
                    await tempTargetsStorage.storeTempTarget(tempTarget: entry)
                    replyHandler(["confirmation": true])
                } else {
                    replyHandler(["confirmation": false])
                }
            }
            return
        }

        if let bolus = message["bolus"] as? Double, bolus > 0 {
            Task {
                await apsManager.enactBolus(amount: bolus, isSMB: false)
                replyHandler(["confirmation": true])
            }
            return
        }

        replyHandler(["confirmation": false])
    }

    func session(_: WCSession, didReceiveMessageData _: Data) {}

    func sessionReachabilityDidChange(_ session: WCSession) {
        if session.isReachable {
            processQueue.async {
                self.sendState()
            }
        }
    }
}

extension BaseWatchManager:
    SettingsObserver,
    PumpHistoryObserver,
    PumpSettingsObserver,
    BasalProfileObserver,
    TempTargetsObserver,
    CarbsObserver,
    PumpBatteryObserver,
    PumpReservoirObserver
{
    func settingsDidChange(_: FreeAPSSettings) {
        Task {
            await configureState()
        }
    }

    func pumpHistoryDidUpdate(_: [PumpHistoryEvent]) {
        // TODO:
    }

    func pumpSettingsDidChange(_: PumpSettings) {
        Task {
            await configureState()
        }
    }

    func basalProfileDidChange(_: [BasalProfileEntry]) {
        // TODO:
    }

    func tempTargetsDidUpdate(_: [TempTarget]) {
        Task {
            await configureState()
        }
    }

    func carbsDidUpdate(_: [CarbsEntry]) {
        // TODO:
    }

    func pumpBatteryDidChange(_: Battery) {
        // TODO:
    }

    func pumpReservoirDidChange(_: Decimal) {
        // TODO:
    }
}