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 glucoseStorage: GlucoseStorage!
    @Injected() private var apsManager: APSManager!
    @Injected() private var storage: FileStorage!
    @Injected() private var carbsStorage: CarbsStorage!
    @Injected() private var tempTargetsStorage: TempTargetsStorage!

    private var lifetime = Lifetime()

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

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

        broadcaster.register(GlucoseObserver.self, observer: self)
        broadcaster.register(SuggestionObserver.self, observer: self)
        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(EnactedSuggestionObserver.self, observer: self)
        broadcaster.register(PumpBatteryObserver.self, observer: self)
        broadcaster.register(PumpReservoirObserver.self, observer: self)

        configureState()
    }

    private func configureState() {
        processQueue.async {
            let glucoseValues = self.glucoseText()
            self.state.glucose = glucoseValues.glucose
            self.state.trend = glucoseValues.trend
            self.state.delta = glucoseValues.delta
            self.state.glucoseDate = self.glucoseStorage.recent().last?.dateString
            self.state.lastLoopDate = self.enactedSuggestion?.recieved == true ? self.enactedSuggestion?.deliverAt : self
                .apsManager.lastLoopDate
            self.state.bolusIncrement = self.settingsManager.preferences.bolusIncrement
            self.state.maxCOB = self.settingsManager.preferences.maxCOB
            self.state.maxBolus = self.settingsManager.pumpSettings.maxBolus
            self.state.carbsRequired = self.suggestion?.carbsReq

            let inslinRequired = self.suggestion?.insulinReq ?? 0
            self.state.bolusRecommended = self.apsManager
                .roundBolus(amount: max(inslinRequired * self.settingsManager.settings.insulinReqFraction, 0))

            self.state.iob = self.suggestion?.iob
            self.state.cob = self.suggestion?.cob
            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.bolusAfterCarbs = !self.settingsManager.settings.skipBolusScreenAfterCarbs
            self.state.eventualBG = self.evetualBGStraing()

            self.sendState()
        }
    }

    private func sendState() {
        dispatchPrecondition(condition: .onQueue(processQueue))
        guard let data = try? JSONEncoder().encode(state) else {
            warning(.service, "Cannot encode watch state")
            return
        }
        guard session.isReachable else { return }
        session.sendMessageData(data, replyHandler: nil) { error in
            warning(.service, "Cannot send message to watch", error: error)
        }
    }

    private func glucoseText() -> (glucose: String, trend: String, delta: String) {
        let glucose = glucoseStorage.recent()

        guard let lastGlucose = glucose.last, let glucoseValue = lastGlucose.glucose else { return ("--", "--", "--") }

        let delta = glucose.count >= 2 ? glucoseValue - (glucose[glucose.count - 2].glucose ?? 0) : nil

        let units = settingsManager.settings.units
        let glucoseText = glucoseFormatter
            .string(from: Double(
                units == .mmolL ? glucoseValue
                    .asMmolL : Decimal(glucoseValue)
            ) as NSNumber)!
        let directionText = lastGlucose.direction?.symbol ?? "↔︎"
        let deltaText = delta
            .map {
                self.deltaFormatter
                    .string(from: Double(
                        units == .mmolL ? $0
                            .asMmolL : Decimal($0)
                    ) as NSNumber)!
            } ?? "--"

        return (glucoseText, directionText, deltaText)
    }

    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 evetualBGStraing() -> String? {
        guard let eventualBG = suggestion?.eventualBG else {
            return nil
        }
        let units = settingsManager.settings.units
        return "⇢ " + eventualFormatter.string(
            from: (units == .mmolL ? eventualBG.asMmolL : Decimal(eventualBG)) as NSNumber
        )!
    }

    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 = 2
        return formatter
    }

    private var deltaFormatter: NumberFormatter {
        let formatter = NumberFormatter()
        formatter.numberStyle = .decimal
        formatter.maximumFractionDigits = 2
        formatter.positivePrefix = "+"
        return formatter
    }

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

    private var suggestion: Suggestion? {
        storage.retrieve(OpenAPS.Enact.suggested, as: Suggestion.self)
    }

    private var enactedSuggestion: Suggestion? {
        storage.retrieve(OpenAPS.Enact.enacted, as: Suggestion.self)
    }
}

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, carbs > 0 {
            carbsStorage.storeCarbs([
                CarbsEntry(createdAt: Date(), carbs: Decimal(carbs), enteredBy: CarbsEntry.manual)
            ])

            if settingsManager.settings.skipBolusScreenAfterCarbs {
                apsManager.determineBasalSync()
                replyHandler(["confirmation": true])
                return
            } else {
                apsManager.determineBasal()
                    .sink { _ in
                        replyHandler(["confirmation": true])
                    }
                    .store(in: &lifetime)
                return
            }
        }

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

        if let bolus = message["bolus"] as? Double, bolus > 0 {
            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:
    GlucoseObserver,
    SuggestionObserver,
    SettingsObserver,
    PumpHistoryObserver,
    PumpSettingsObserver,
    BasalProfileObserver,
    TempTargetsObserver,
    CarbsObserver,
    EnactedSuggestionObserver,
    PumpBatteryObserver,
    PumpReservoirObserver
{
    func glucoseDidUpdate(_: [BloodGlucose]) {
        configureState()
    }

    func suggestionDidUpdate(_: Suggestion) {
        configureState()
    }

    func settingsDidChange(_: FreeAPSSettings) {
        configureState()
    }

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

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

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

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

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

    func enactedSuggestionDidUpdate(_: Suggestion) {
        configureState()
    }

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

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