// LoopFollow
// BGData.swift

import Foundation
import UIKit

extension MainViewController {
    /// Number of days of BG history to request from the source. One extra day is
    /// added when the "Show Yesterday's BG" overlay is enabled (Nightscout only),
    /// so the overlay can display the same clock time from the day before.
    var bgFetchDays: Int {
        let extraDay = (Storage.shared.showYesterdayLine.value && IsNightscoutEnabled()) ? 1 : 0
        return Storage.shared.downloadDays.value + extraDay
    }

    // Dex Share Web Call
    func webLoadDexShare() {
        // Dexcom Share only returns 24 hrs of data as of now
        // Requesting more just for consistency with NS
        let graphHours = 24 * bgFetchDays
        let count = graphHours * 12
        dexShare?.fetchData(count) { err, result in
            if let error = err {
                LogManager.shared.log(category: .dexcom, message: "Error fetching Dexcom data: \(error.localizedDescription)", limitIdentifier: "Error fetching Dexcom data")
                self.webLoadNSBGData()
                return
            }

            guard let data = result, !data.isEmpty else {
                LogManager.shared.log(category: .dexcom, message: "Received empty data array from Dexcom", limitIdentifier: "Received empty data array from Dexcom")
                self.webLoadNSBGData()
                return
            }

            // If Dex data is old, load from NS instead
            let latestDate = data[0].date
            let now = dateTimeUtils.getNowTimeIntervalUTC()
            if (latestDate + 330) < now, IsNightscoutEnabled() {
                LogManager.shared.log(category: .dexcom, message: "Dexcom data is old, loading from NS instead", limitIdentifier: "Dexcom data is old, loading from NS instead")
                self.webLoadNSBGData()
                return
            }

            // Dexcom Share can return duplicate readings when multiple uploaders
            // write to the same Dexcom account. Dedup before any further use.
            let dedupedData = self.deduplicateBGReadings(data)

            // Supplement with NS if Dex data doesn't cover the full requested window.
            let dexCutoff = dateTimeUtils.getNowTimeIntervalUTC() - Double(graphHours) * 3600
            let dexCoversFull = dedupedData.last.map { $0.date <= dexCutoff } ?? false
            if !dexCoversFull, IsNightscoutEnabled() {
                self.webLoadNSBGData(dexData: dedupedData)
            } else {
                self.ProcessDexBGData(data: dedupedData, sourceName: "Dexcom")
            }
        }
    }

    // NS BG Data Web call
    func webLoadNSBGData(dexData: [ShareGlucoseData] = []) {
        // This kicks it out in the instance where dexcom fails but they aren't using NS &&
        if !IsNightscoutEnabled() {
            Storage.shared.lastBGChecked.value = Date()
            return
        }

        var parameters: [String: String] = [:]
        let date = Calendar.current.date(byAdding: .day, value: -1 * bgFetchDays, to: Date())!
        parameters["count"] = "\(bgFetchDays * globalVariables.maxExpectedUploaders * 24 * 60 / 5)"
        parameters["find[date][$gte]"] = "\(Int(date.timeIntervalSince1970 * 1000))"

        // Exclude 'cal' entries
        parameters["find[type][$ne]"] = "cal"

        NightscoutUtils.executeRequest(eventType: .sgv, parameters: parameters) { (result: Result<[ShareGlucoseData], Error>) in
            switch result {
            case let .success(entriesResponse):
                var nsData = entriesResponse
                DispatchQueue.main.async {
                    // transform NS data to look like Dex data
                    for i in 0 ..< nsData.count {
                        // convert the NS timestamp to seconds instead of milliseconds
                        nsData[i].date /= 1000
                        nsData[i].date.round(FloatingPointRoundingRule.toNearestOrEven)
                    }

                    var nsData2 = self.deduplicateBGReadings(nsData)

                    // merge NS and Dex data if needed; use recent Dex data and older NS data
                    var sourceName = "Nightscout"
                    if !dexData.isEmpty {
                        let oldestDexDate = dexData[dexData.count - 1].date
                        var itemsToRemove = 0
                        while itemsToRemove < nsData2.count, nsData2[itemsToRemove].date >= oldestDexDate {
                            itemsToRemove += 1
                        }
                        nsData2.removeFirst(itemsToRemove)
                        nsData2 = dexData + nsData2
                        sourceName = "Dexcom"
                    }
                    // trigger the processor for the data after downloading.
                    self.ProcessDexBGData(data: nsData2, sourceName: sourceName)
                }
            case let .failure(error):
                LogManager.shared.log(category: .nightscout, message: "Failed to fetch bg data: \(error)", limitIdentifier: "Failed to fetch bg data")
                DispatchQueue.main.async {
                    TaskScheduler.shared.rescheduleTask(
                        id: .fetchBG,
                        to: Date().addingTimeInterval(10)
                    )
                }
                // if we have Dex data, use it
                if !dexData.isEmpty {
                    self.ProcessDexBGData(data: dexData, sourceName: "Dexcom")
                } else {
                    Storage.shared.lastBGChecked.value = Date()
                }
                return
            }
        }
    }

    /// Removes consecutive duplicate readings (same SGV within 30 s). Expects newest-first input.
    func deduplicateBGReadings(_ readings: [ShareGlucoseData]) -> [ShareGlucoseData] {
        var result: [ShareGlucoseData] = []
        var lastTime = Double.infinity
        var lastSGV: Int?
        for reading in readings {
            if lastSGV == nil || lastSGV != reading.sgv || lastTime - reading.date >= 30 {
                result.append(reading)
                lastTime = reading.date
                lastSGV = reading.sgv
            }
        }
        return result
    }

    /// Processes incoming BG data.
    func ProcessDexBGData(data: [ShareGlucoseData], sourceName: String) {
        let graphHours = 24 * Storage.shared.downloadDays.value

        guard !data.isEmpty else {
            LogManager.shared.log(category: .nightscout, message: "No bg data received. Skipping processing.", limitIdentifier: "No bg data received. Skipping processing.")
            Storage.shared.lastBGChecked.value = Date()
            return
        }

        let latestReading = data[0]
        let sensorTimestamp = latestReading.date
        let now = dateTimeUtils.getNowTimeIntervalUTC()
        // secondsAgo is how old the newest reading is
        let secondsAgo = now - sensorTimestamp

        // Compute the current sensor schedule offset
        let currentOffset = CycleHelper.cycleOffset(for: sensorTimestamp, interval: 5 * 60)

        if Storage.shared.sensorScheduleOffset.value != currentOffset {
            Storage.shared.sensorScheduleOffset.value = currentOffset
            LogManager.shared.log(category: .nightscout,
                                  message: "Sensor schedule offset: \(currentOffset) seconds.",
                                  isDebug: true)
        }

        // Determine the next polling delay.
        var delayToSchedule: Double = 0

        DispatchQueue.main.async {
            // Fallback scheduling for older readings.
            if secondsAgo >= (20 * 60) {
                delayToSchedule = 5 * 60
                LogManager.shared.log(category: .nightscout,
                                      message: "Reading is very old (\(secondsAgo) sec). Scheduling next fetch in 5 minutes.",
                                      isDebug: true)
            } else if secondsAgo >= (10 * 60) {
                delayToSchedule = 60
                LogManager.shared.log(category: .nightscout,
                                      message: "Reading is moderately old (\(secondsAgo) sec). Scheduling next fetch in 60 seconds.",
                                      isDebug: true)
            } else if secondsAgo >= (7 * 60) {
                delayToSchedule = 30
                LogManager.shared.log(category: .nightscout,
                                      message: "Reading is a bit old (\(secondsAgo) sec). Scheduling next fetch in 30 seconds.",
                                      isDebug: true)
            } else if secondsAgo >= (5 * 60) {
                delayToSchedule = 5
                LogManager.shared.log(category: .nightscout,
                                      message: "Reading is close to 5 minutes old (\(secondsAgo) sec). Scheduling next fetch in 5 seconds.",
                                      isDebug: true)
            } else {
                delayToSchedule = 300 - secondsAgo + Double(Storage.shared.bgUpdateDelay.value)
                LogManager.shared.log(category: .nightscout,
                                      message: "Fresh reading. Scheduling next fetch in \(delayToSchedule) seconds.",
                                      isDebug: true)
                TaskScheduler.shared.rescheduleTask(id: .alarmCheck, to: Date().addingTimeInterval(3))
            }

            if NightscoutSocketManager.shared.connectionState == .authenticated {
                delayToSchedule = max(delayToSchedule * 3, 60)
            }

            TaskScheduler.shared.rescheduleTask(id: .fetchBG, to: Date().addingTimeInterval(delayToSchedule))

            // Evaluate speak conditions if there is a previous value.
            if data.count > 1 {
                self.evaluateSpeakConditions(currentValue: data[0].sgv, previousValue: data[1].sgv)
            }
        }

        // Process data for graph display.
        bgData.removeAll()
        for i in 0 ..< data.count {
            let readingTimestamp = data[data.count - 1 - i].date
            if readingTimestamp >= dateTimeUtils.getTimeIntervalNHoursAgo(N: graphHours) {
                let sgvValue = data[data.count - 1 - i].sgv

                // Skip outlier values (e.g. first reading of a new sensor might be abnormally high).
                if sgvValue > 600 {
                    LogManager.shared.log(category: .nightscout,
                                          message: "Skipping reading with sgv \(sgvValue) as it exceeds threshold.",
                                          isDebug: true)
                    continue
                }

                let reading = ShareGlucoseData(sgv: sgvValue, date: readingTimestamp, direction: data[data.count - 1 - i].direction)
                bgData.append(reading)
            }
        }

        LogManager.shared.log(category: .nightscout,
                              message: "Graph data updated with \(bgData.count) entries.",
                              isDebug: true)

        // Build the optional "yesterday" comparison overlay. Every fetched reading is
        // shifted +24h so it lines up with the same clock time today; the extra day of
        // history pulled by bgFetchDays provides the portion that falls inside the
        // visible window. The overlay is capped to "now + hours of prediction" so it
        // never extends further into the future than the prediction line.
        yesterdayBGData.removeAll()
        if Storage.shared.showYesterdayLine.value, IsNightscoutEnabled() {
            let cutoff = dateTimeUtils.getTimeIntervalNHoursAgo(N: 24 * bgFetchDays)
            let futureLimit = dateTimeUtils.getNowTimeIntervalUTC() + Storage.shared.predictionToLoad.value * 3600
            for i in 0 ..< data.count {
                let reading = data[data.count - 1 - i]
                guard reading.date >= cutoff, reading.sgv <= 600 else { continue }
                let shiftedDate = reading.date + 24 * 60 * 60
                guard shiftedDate <= futureLimit else { continue }
                yesterdayBGData.append(ShareGlucoseData(sgv: reading.sgv,
                                                        date: shiftedDate,
                                                        direction: reading.direction))
            }
        }

        viewUpdateNSBG(sourceName: sourceName)
    }

    func updateServerText(with serverText: String? = nil) {
        if Storage.shared.showDisplayName.value, let displayName = Bundle.main.object(forInfoDictionaryKey: "CFBundleDisplayName") as? String {
            Observable.shared.serverText.value = displayName
        } else if let serverText = serverText {
            Observable.shared.serverText.value = serverText
        }
    }

    // NS BG Data Front end updater
    func viewUpdateNSBG(sourceName: String) {
        DispatchQueue.main.async {
            TaskScheduler.shared.rescheduleTask(id: .minAgoUpdate, to: Date())

            let entries = self.bgData
            if entries.count < 2 { // Protect index out of bounds
                Storage.shared.lastBGChecked.value = Date()
                return
            }

            self.updateBGGraph()
            self.updateStats()

            let latestEntryIndex = entries.count - 1
            let latestBG = entries[latestEntryIndex].sgv
            let priorBG = entries[latestEntryIndex - 1].sgv
            let deltaBG = latestBG - priorBG
            let lastBGTime = entries[latestEntryIndex].date

            self.updateServerText(with: sourceName)

            // Set BGText with the latest BG value
            self.updateBGTextAppearance()

            if latestBG <= globalVariables.minDisplayGlucose {
                Observable.shared.bgText.value = "LOW"
            } else if latestBG >= globalVariables.maxDisplayGlucose {
                Observable.shared.bgText.value = "HIGH"
            } else {
                Observable.shared.bgText.value = Localizer.toDisplayUnits(String(latestBG))
            }
            Observable.shared.bg.value = latestBG

            // Direction handling
            if let directionBG = entries[latestEntryIndex].direction {
                Observable.shared.directionText.value = self.bgDirectionGraphic(directionBG)
            } else {
                Observable.shared.directionText.value = ""
            }

            // Delta handling
            if deltaBG < 0 {
                Observable.shared.deltaText.value = Localizer.toDisplayUnits(String(deltaBG))
            } else {
                Observable.shared.deltaText.value = "+" + Localizer.toDisplayUnits(String(deltaBG))
            }

            // Live Activity storage
            Storage.shared.lastBgReadingTimeSeconds.value = lastBGTime
            Storage.shared.lastDeltaMgdl.value = Double(deltaBG)
            Storage.shared.lastTrendCode.value = entries[latestEntryIndex].direction

            // Mark BG data as loaded for initial loading state
            self.markDataLoaded("bg")

            // Live Activity update
            #if !targetEnvironment(macCatalyst)
                LiveActivityManager.shared.refreshFromCurrentState(reason: "bg")
            #endif

            // Update contact
            if Storage.shared.contactEnabled.value {
                self.contactImageUpdater
                    .updateContactImage(
                        bgValue: Observable.shared.bgText.value,
                        trend: Observable.shared.directionText.value,
                        delta: Observable.shared.deltaText.value,
                        iob: Observable.shared.iobText.value,
                        stale: Observable.shared.bgStale.value
                    )
            }
            Storage.shared.lastBGChecked.value = Date()
        }
    }
}