//
//  ChargerStandbyPowerWizardView.swift
//  USB Meter
//
//  Created by Codex on 13/04/2026.
//

import SwiftUI

struct ChargerStandbyPowerWizardView: View {
    @EnvironmentObject private var appData: AppData

    @State private var chargerLibraryVisibility = false
    @State private var discardConfirmationVisibility = false
    @State private var selectedMeterMACAddress: String?
    @State private var selectedChargerID: UUID?

    let preferredMeterMACAddress: String?
    let preferredChargerID: UUID?
    let locksChargerSelection: Bool

    init(
        preferredMeterMACAddress: String? = nil,
        preferredChargerID: UUID? = nil,
        locksChargerSelection: Bool = false
    ) {
        self.preferredMeterMACAddress = preferredMeterMACAddress
        self.preferredChargerID = preferredChargerID
        self.locksChargerSelection = locksChargerSelection
        _selectedMeterMACAddress = State(initialValue: nil)
        _selectedChargerID = State(initialValue: preferredChargerID)
    }

    var body: some View {
        ScrollView {
            VStack(spacing: 18) {
                if let session = activeSession {
                    activeMeasurementCard(session)
                    liveSessionCard(session)
                } else {
                    newMeasurementWizardCard
                }
            }
            .padding()
        }
        .background(
            LinearGradient(
                colors: [.orange.opacity(0.16), Color.clear],
                startPoint: .topLeading,
                endPoint: .bottomTrailing
            )
            .ignoresSafeArea()
        )
        .navigationTitle(navigationTitleText)
        .sheet(isPresented: $chargerLibraryVisibility) {
            ChargedDeviceLibrarySheetView(
                visibility: $chargerLibraryVisibility,
                meterMACAddress: selectedMeterSummary?.macAddress ?? "",
                meterTint: selectedMeter?.color ?? .orange,
                mode: .charger
            )
            .environmentObject(appData)
        }
        .confirmationDialog(
            "Discard the current standby measurement?",
            isPresented: $discardConfirmationVisibility,
            titleVisibility: .visible
        ) {
            Button("Discard", role: .destructive) {
                if let activeSession {
                    _ = appData.finishChargerStandbyMeasurement(for: activeSession.meterMACAddress, save: false)
                }
            }
            Button("Cancel", role: .cancel) {}
        } message: {
            Text("The current sample set will be removed and nothing will be saved for this charger.")
        }
    }

    private var liveMeterSummaries: [AppData.MeterSummary] {
        appData.meterSummaries.filter { $0.meter != nil }
    }

    private var availableChargers: [ChargedDeviceSummary] {
        appData.chargerSummaries
    }

    private var preferredChargerMeterMACAddress: String? {
        preferredChargerID.flatMap { appData.chargedDeviceSummary(id: $0)?.lastAssociatedMeterMAC }
    }

    private var activeSession: ChargerStandbyPowerMonitorSession? {
        let candidateMACAddresses = [
            selectedMeterMACAddress ?? "",
            preferredMeterMACAddress ?? "",
            preferredChargerMeterMACAddress ?? ""
        ]
        .filter { $0.isEmpty == false }

        for macAddress in candidateMACAddresses {
            if let session = appData.chargerStandbyMeasurementSession(for: macAddress) {
                return session
            }
        }

        for meterSummary in liveMeterSummaries {
            if let session = appData.chargerStandbyMeasurementSession(for: meterSummary.macAddress) {
                return session
            }
        }

        return nil
    }

    private var suggestedMeterSummary: AppData.MeterSummary? {
        if let preferredMeterMACAddress {
            return liveMeterSummaries.first(where: { $0.macAddress == preferredMeterMACAddress })
        }

        if let preferredChargerMeterMACAddress {
            return liveMeterSummaries.first(where: { $0.macAddress == preferredChargerMeterMACAddress })
        }

        return liveMeterSummaries.count == 1 ? liveMeterSummaries.first : nil
    }

    private var selectedMeterSummary: AppData.MeterSummary? {
        if let activeSession {
            return liveMeterSummaries.first(where: { $0.macAddress == activeSession.meterMACAddress })
        }

        guard let selectedMeterMACAddress else {
            return nil
        }

        return liveMeterSummaries.first(where: { $0.macAddress == selectedMeterMACAddress })
    }

    private var selectedMeter: Meter? {
        selectedMeterSummary?.meter
    }

    private var isChargerSelectionLocked: Bool {
        locksChargerSelection || preferredChargerID != nil
    }

    private var meterSelectionBinding: Binding<String?> {
        Binding(
            get: { selectedMeterMACAddress },
            set: { selectedMeterMACAddress = $0 }
        )
    }

    private var selectedCharger: ChargedDeviceSummary? {
        if let activeSession {
            return appData.chargedDeviceSummary(id: activeSession.chargerID)
        }

        guard let selectedChargerID else {
            return nil
        }

        return appData.chargedDeviceSummary(id: selectedChargerID)
    }

    private var chargerSelectionBinding: Binding<UUID?> {
        Binding(
            get: { selectedChargerID },
            set: { selectedChargerID = $0 }
        )
    }

    private var preferredChargerSummary: ChargedDeviceSummary? {
        guard let preferredChargerID else {
            return nil
        }
        return appData.chargedDeviceSummary(id: preferredChargerID)
    }

    private var navigationTitleText: String {
        "New Standby Consumption Measurement"
    }

    private var wizardCardTitle: String {
        if let selectedMeterSummary {
            return selectedMeterSummary.displayName
        }

        if let suggestedMeterSummary {
            return suggestedMeterSummary.displayName
        }

        return "Use Meter"
    }

    private var newMeasurementWizardCard: some View {
        MeterInfoCardView(
            title: wizardCardTitle,
            tint: .orange
        ) {
            if liveMeterSummaries.isEmpty {
                Text("Connect a live meter first. Standby measurement uses a live feed, so meter selection happens here in the wizard.")
                    .font(.footnote)
                    .foregroundColor(.secondary)
                    .frame(maxWidth: .infinity, alignment: .leading)
            } else {
                VStack(alignment: .leading, spacing: 12) {
                    if isChargerSelectionLocked == false {
                        HStack(spacing: 8) {
                            Text("Charger")
                                .font(.subheadline.weight(.semibold))
                            ContextInfoButton(
                                title: "Charger",
                                message: "Choose the charger whose standby consumption you want to measure in this run."
                            )
                        }

                        if availableChargers.isEmpty {
                            Text("No charger available yet. Open the charger library to create one first.")
                                .font(.caption)
                                .foregroundColor(.secondary)
                        } else {
                            Picker("Charger", selection: chargerSelectionBinding) {
                                Text("Select Charger").tag(Optional<UUID>.none)
                                ForEach(availableChargers) { charger in
                                    Text(charger.name).tag(Optional(charger.id))
                                }
                            }
                            .pickerStyle(.menu)
                        }
                    }

                    HStack(spacing: 8) {
                        Text("Use Meter")
                            .font(.subheadline.weight(.semibold))
                        ContextInfoButton(
                            title: "Use Meter",
                            message: "Choose the live meter explicitly. Standby consumption can vary with the upstream source or when the charger is connected to a computer, so re-run after setup changes."
                        )
                    }

                    Picker("Use Meter", selection: meterSelectionBinding) {
                        Text("Select Meter").tag(Optional<String>.none)
                        ForEach(liveMeterSummaries) { meterSummary in
                            Text(meterSummary.displayName).tag(Optional(meterSummary.macAddress))
                        }
                    }
                    .pickerStyle(.menu)
                    .disabled(activeSession != nil)

                    if activeSession == nil, let suggestedMeterSummary, selectedMeterSummary == nil {
                        Text("Suggested from the current context: \(suggestedMeterSummary.displayName). Select it explicitly if this is the meter you want to use.")
                            .font(.caption)
                            .foregroundColor(.secondary)
                    }

                    HStack(spacing: 12) {
                        if isChargerSelectionLocked == false {
                            Button("Manage Charger Library") {
                                chargerLibraryVisibility = true
                            }
                            .disabled(selectedMeter == nil)
                        }

                        Button("Start Measurement") {
                            startMeasurement()
                        }
                        .disabled(selectedCharger == nil || selectedMeter == nil)
                    }
                    .buttonStyle(.borderedProminent)
                }
            }

            if selectedMeter == nil {
                Text("Choose the live meter explicitly before starting. The wizard no longer auto-confirms a suggested meter.")
                    .font(.caption)
                    .foregroundColor(.secondary)
            } else if activeSession == nil, selectedCharger == nil {
                Text("Select the charger you want to measure, then start the run.")
                    .font(.caption)
                    .foregroundColor(.secondary)
            } else if activeSession == nil, selectedMeter?.operationalState != .dataIsAvailable {
                Text("The wizard can start now, but samples will only be captured while live meter data is available.")
                    .font(.caption)
                    .foregroundColor(.secondary)
            } else if let activeSession {
                Text(
                    "\(activeSession.readinessDescription) • \(formattedDuration(Date().timeIntervalSince(activeSession.startedAt))) • \(activeSession.sampleCount) samples"
                )
                .font(.caption)
                .foregroundColor(.secondary)
            }
        }
    }

    private func activeMeasurementCard(_ session: ChargerStandbyPowerMonitorSession) -> some View {
        MeterInfoCardView(
            title: "Measurement Running",
            infoMessage: "The run keeps collecting samples while this meter stays live. Save when you are happy with the sample set, or discard to cancel it.",
            tint: .orange
        ) {
            MeterInfoRowView(label: "Meter", value: selectedMeterSummary?.displayName ?? session.meterMACAddress)
            MeterInfoRowView(label: "Charger", value: selectedCharger?.name ?? "Selected charger")
            MeterInfoRowView(label: "Status", value: session.readinessDescription)
            MeterInfoRowView(label: "Samples", value: "\(session.sampleCount)")

            HStack(spacing: 12) {
                Button("Save Result") {
                    _ = appData.finishChargerStandbyMeasurement(for: session.meterMACAddress, save: true)
                }
                .disabled(session.hasSamples == false)

                Button("Discard") {
                    discardConfirmationVisibility = true
                }
                .foregroundColor(.red)
            }
            .buttonStyle(.borderedProminent)
        }
    }

    private func liveSessionCard(_ session: ChargerStandbyPowerMonitorSession) -> some View {
        VStack(spacing: 18) {
            if let statistics = session.statistics {
                stabilityCard(
                    isStable: statistics.isStable,
                    averagePowerWatts: statistics.averagePowerWatts,
                    stabilityDeltaWatts: statistics.stabilityDeltaWatts,
                    stabilityToleranceWatts: statistics.stabilityToleranceWatts,
                    sampleCount: statistics.sampleCount
                )

                projectionCard(
                    averagePowerWatts: statistics.averagePowerWatts,
                    projectedDailyEnergyWh: statistics.projectedDailyEnergyWh,
                    projectedWeeklyEnergyWh: statistics.projectedWeeklyEnergyWh,
                    projectedMonthlyEnergyWh: statistics.projectedMonthlyEnergyWh,
                    projectedYearlyEnergyWh: statistics.projectedYearlyEnergyWh
                )

                distributionCard(
                    histogram: statistics.histogram,
                    averagePowerWatts: statistics.averagePowerWatts,
                    standardDeviationPowerWatts: statistics.standardDeviationPowerWatts,
                    tint: .orange
                )

                statisticsCard(
                    averagePowerWatts: statistics.averagePowerWatts,
                    medianPowerWatts: statistics.medianPowerWatts,
                    minimumPowerWatts: statistics.minimumPowerWatts,
                    maximumPowerWatts: statistics.maximumPowerWatts,
                    standardDeviationPowerWatts: statistics.standardDeviationPowerWatts,
                    coefficientOfVariation: statistics.coefficientOfVariation,
                    averageCurrentAmps: statistics.averageCurrentAmps,
                    averageVoltageVolts: statistics.averageVoltageVolts
                )
            } else {
                MeterInfoCardView(title: "Live Stats", tint: .orange) {
                    Text("Waiting for the first valid power samples from the meter.")
                        .font(.footnote)
                        .foregroundColor(.secondary)
                }
            }
        }
    }

    private func stabilityCard(
        isStable: Bool,
        averagePowerWatts: Double,
        stabilityDeltaWatts: Double,
        stabilityToleranceWatts: Double,
        sampleCount: Int,
        subtitle: String? = nil
    ) -> some View {
        VStack(alignment: .leading, spacing: 10) {
            HStack {
                VStack(alignment: .leading, spacing: 4) {
                    Text(isStable ? "Enough Samples" : "Still Settling")
                        .font(.headline)
                    Text(subtitle ?? (isStable ? "The running average has stabilised." : "The wizard is still watching the average drift."))
                        .font(.caption)
                        .foregroundColor(.secondary)
                }

                Spacer()

                Text(isStable ? "Ready" : "Live")
                    .font(.caption.weight(.semibold))
                    .padding(.horizontal, 10)
                    .padding(.vertical, 6)
                    .foregroundColor(isStable ? .green : .orange)
                    .meterCard(
                        tint: isStable ? .green : .orange,
                        fillOpacity: 0.10,
                        strokeOpacity: 0.16,
                        cornerRadius: 999
                    )
            }

            Text("\(averagePowerWatts.format(decimalDigits: 3)) W")
                .font(.system(.largeTitle, design: .rounded).weight(.bold))
                .monospacedDigit()

            Text(
                "Recent drift: \((stabilityDeltaWatts * 1000).format(decimalDigits: 2)) mW, tolerance \((stabilityToleranceWatts * 1000).format(decimalDigits: 2)) mW over \(sampleCount) samples."
            )
            .font(.footnote)
            .foregroundColor(.secondary)
        }
        .frame(maxWidth: .infinity, alignment: .leading)
        .padding(18)
        .meterCard(tint: isStable ? .green : .orange, fillOpacity: 0.18, strokeOpacity: 0.24)
    }

    private func projectionCard(
        averagePowerWatts: Double,
        projectedDailyEnergyWh: Double,
        projectedWeeklyEnergyWh: Double,
        projectedMonthlyEnergyWh: Double,
        projectedYearlyEnergyWh: Double
    ) -> some View {
        MeterInfoCardView(
            title: "Consumption Projection",
            infoMessage: "These projections extrapolate only from the measured standby average. They do not say anything about charger behaviour under load.",
            tint: .teal
        ) {
            MeterInfoRowView(label: "Average Power", value: "\(averagePowerWatts.format(decimalDigits: 3)) W")
            MeterInfoRowView(label: "24 Hours", value: standbyEnergyLabel(projectedDailyEnergyWh))
            MeterInfoRowView(label: "7 Days", value: standbyEnergyLabel(projectedWeeklyEnergyWh))
            MeterInfoRowView(label: "30 Days", value: standbyEnergyLabel(projectedMonthlyEnergyWh))
            MeterInfoRowView(label: "1 Year", value: standbyEnergyLabel(projectedYearlyEnergyWh))
        }
    }

    private func distributionCard(
        histogram: [ChargerStandbyPowerDistributionBin],
        averagePowerWatts: Double,
        standardDeviationPowerWatts: Double,
        tint: Color
    ) -> some View {
        MeterInfoCardView(
            title: "Distribution",
            infoMessage: "Bars show how often each power interval appeared. The curve overlays a normal approximation around the observed mean and deviation.",
            tint: tint
        ) {
            StandbyPowerHistogramView(
                histogram: histogram,
                averagePowerWatts: averagePowerWatts,
                standardDeviationPowerWatts: standardDeviationPowerWatts,
                tint: tint
            )
            .frame(height: 220)

            if let firstBin = histogram.first, let lastBin = histogram.last {
                HStack {
                    Text("\(firstBin.lowerBoundWatts.format(decimalDigits: 3)) W")
                    Spacer()
                    Text("\(lastBin.upperBoundWatts.format(decimalDigits: 3)) W")
                }
                .font(.caption)
                .foregroundColor(.secondary)
                .monospacedDigit()
            }
        }
    }

    private func statisticsCard(
        averagePowerWatts: Double,
        medianPowerWatts: Double,
        minimumPowerWatts: Double,
        maximumPowerWatts: Double,
        standardDeviationPowerWatts: Double,
        coefficientOfVariation: Double,
        averageCurrentAmps: Double,
        averageVoltageVolts: Double
    ) -> some View {
        MeterInfoCardView(title: "Interesting Stats", tint: .indigo) {
            MeterInfoRowView(label: "Median", value: "\(medianPowerWatts.format(decimalDigits: 3)) W")
            MeterInfoRowView(label: "Minimum", value: "\(minimumPowerWatts.format(decimalDigits: 3)) W")
            MeterInfoRowView(label: "Maximum", value: "\(maximumPowerWatts.format(decimalDigits: 3)) W")
            MeterInfoRowView(label: "Spread σ", value: "\(standardDeviationPowerWatts.format(decimalDigits: 4)) W")
            MeterInfoRowView(label: "Variation", value: "\(Int((coefficientOfVariation * 100).rounded()))%")
            MeterInfoRowView(label: "Mean Current", value: "\(averageCurrentAmps.format(decimalDigits: 3)) A")
            MeterInfoRowView(label: "Mean Voltage", value: "\(averageVoltageVolts.format(decimalDigits: 3)) V")
            MeterInfoRowView(label: "Power Density", value: "\(averagePowerWatts.format(decimalDigits: 3)) W steady")
        }
    }

    private func startMeasurement() {
        guard let selectedCharger, let selectedMeter else {
            return
        }

        _ = appData.startChargerStandbyMeasurement(for: selectedCharger.id, on: selectedMeter)
    }

    private func standbyEnergyLabel(_ wattHours: Double) -> String {
        if wattHours >= 1000 {
            return "\((wattHours / 1000).format(decimalDigits: 3)) kWh"
        }
        return "\(wattHours.format(decimalDigits: 2)) Wh"
    }

    private func formattedDuration(_ duration: TimeInterval) -> String {
        let formatter = DateComponentsFormatter()
        formatter.allowedUnits = duration >= 3600 ? [.hour, .minute, .second] : [.minute, .second]
        formatter.unitsStyle = .abbreviated
        formatter.zeroFormattingBehavior = .pad
        return formatter.string(from: max(duration, 0)) ?? "0s"
    }

}

private struct StandbyPowerHistogramView: View {
    let histogram: [ChargerStandbyPowerDistributionBin]
    let averagePowerWatts: Double
    let standardDeviationPowerWatts: Double
    let tint: Color

    var body: some View {
        GeometryReader { proxy in
            let maxCount = max(Double(histogram.map(\.count).max() ?? 1), 1)

            ZStack {
                HStack(alignment: .bottom, spacing: 6) {
                    ForEach(histogram) { bin in
                        RoundedRectangle(cornerRadius: 8, style: .continuous)
                            .fill(tint.opacity(0.24))
                            .overlay(
                                RoundedRectangle(cornerRadius: 8, style: .continuous)
                                    .stroke(tint.opacity(0.22), lineWidth: 1)
                            )
                            .frame(height: max(10, (Double(bin.count) / maxCount) * proxy.size.height))
                    }
                }
                .frame(maxWidth: .infinity, maxHeight: .infinity, alignment: .bottom)

                gaussianCurve(in: proxy.size)
                    .stroke(tint, style: StrokeStyle(lineWidth: 2.5, lineCap: .round, lineJoin: .round))

                meanMarker(in: proxy.size)
                    .stroke(tint.opacity(0.9), style: StrokeStyle(lineWidth: 1.5, dash: [6, 4]))
            }
        }
    }

    private func gaussianCurve(in size: CGSize) -> Path {
        guard histogram.count > 1,
              standardDeviationPowerWatts > 0,
              let firstBin = histogram.first,
              let lastBin = histogram.last else {
            return Path()
        }

        let minimum = firstBin.lowerBoundWatts
        let maximum = lastBin.upperBoundWatts
        let span = max(maximum - minimum, 0.000_001)
        let sampleCount = 48
        let peakDensity = 1 / (standardDeviationPowerWatts * sqrt(2 * .pi))

        return Path { path in
            for index in 0...sampleCount {
                let progress = Double(index) / Double(sampleCount)
                let value = minimum + (span * progress)
                let zScore = (value - averagePowerWatts) / standardDeviationPowerWatts
                let density = exp(-0.5 * zScore * zScore) / (standardDeviationPowerWatts * sqrt(2 * .pi))
                let normalizedHeight = density / peakDensity

                let x = progress * size.width
                let y = size.height - (normalizedHeight * (Double(size.height) * 0.92))
                let point = CGPoint(x: x, y: y)

                if index == 0 {
                    path.move(to: point)
                } else {
                    path.addLine(to: point)
                }
            }
        }
    }

    private func meanMarker(in size: CGSize) -> Path {
        guard let firstBin = histogram.first, let lastBin = histogram.last else {
            return Path()
        }

        let minimum = firstBin.lowerBoundWatts
        let maximum = lastBin.upperBoundWatts
        let span = max(maximum - minimum, 0.000_001)
        let normalizedX = min(max((averagePowerWatts - minimum) / span, 0), 1)
        let x = normalizedX * size.width

        return Path { path in
            path.move(to: CGPoint(x: x, y: 0))
            path.addLine(to: CGPoint(x: x, y: size.height))
        }
    }
}

struct ChargerStandbyPowerMeasurementsView: View {
    @EnvironmentObject private var appData: AppData

    let chargerID: UUID

    var body: some View {
        Group {
            if let charger = appData.chargedDeviceSummary(id: chargerID) {
                List {
                    if charger.standbyPowerMeasurements.isEmpty {
                        Text("No standby measurements saved yet.")
                            .foregroundColor(.secondary)
                    } else {
                        ForEach(charger.standbyPowerMeasurements) { measurement in
                            NavigationLink(
                                destination: ChargerStandbyPowerMeasurementDetailView(
                                    chargerID: charger.id,
                                    measurementID: measurement.id
                                )
                            ) {
                                VStack(alignment: .leading, spacing: 6) {
                                    HStack {
                                        Text(measurement.endedAt.format())
                                            .font(.subheadline.weight(.semibold))
                                        Spacer()
                                        Text("\(measurement.averagePowerWatts.format(decimalDigits: 3)) W")
                                            .font(.subheadline.weight(.bold))
                                            .monospacedDigit()
                                    }

                                    Text(
                                        "\(formattedDuration(measurement.duration)) • \(measurement.sampleCount) samples • \(standbyEnergyLabel(measurement.projectedYearlyEnergyWh)) / year"
                                    )
                                    .font(.caption)
                                    .foregroundColor(.secondary)
                                }
                                .frame(maxWidth: .infinity, alignment: .leading)
                            }
                        }
                    }
                }
                .navigationTitle("Saved Measurements")
            } else {
                Text("This charger is no longer available.")
                    .foregroundColor(.secondary)
                    .navigationTitle("Saved Measurements")
            }
        }
    }

    private func standbyEnergyLabel(_ wattHours: Double) -> String {
        if wattHours >= 1000 {
            return "\((wattHours / 1000).format(decimalDigits: 3)) kWh"
        }
        return "\(wattHours.format(decimalDigits: 2)) Wh"
    }

    private func formattedDuration(_ duration: TimeInterval) -> String {
        let formatter = DateComponentsFormatter()
        formatter.allowedUnits = duration >= 3600 ? [.hour, .minute, .second] : [.minute, .second]
        formatter.unitsStyle = .abbreviated
        formatter.zeroFormattingBehavior = .pad
        return formatter.string(from: max(duration, 0)) ?? "0s"
    }
}

struct ChargerStandbyPowerMeasurementDetailView: View {
    @EnvironmentObject private var appData: AppData

    let chargerID: UUID
    let measurementID: UUID

    var body: some View {
        Group {
            if let charger = appData.chargedDeviceSummary(id: chargerID),
               let measurement = charger.standbyPowerMeasurements.first(where: { $0.id == measurementID }) {
                ScrollView {
                    VStack(spacing: 18) {
                        MeterInfoCardView(title: charger.name, tint: .orange) {
                            MeterInfoRowView(label: "Saved", value: measurement.endedAt.format())
                            MeterInfoRowView(label: "Average", value: "\(measurement.averagePowerWatts.format(decimalDigits: 3)) W")
                            MeterInfoRowView(label: "Samples", value: "\(measurement.sampleCount)")
                            MeterInfoRowView(label: "Duration", value: formattedDuration(measurement.duration))
                        }

                        ChargerStandbyPowerMeasurementSnapshotView(measurement: measurement)
                    }
                    .padding()
                }
                .background(
                    LinearGradient(
                        colors: [.orange.opacity(0.16), Color.clear],
                        startPoint: .topLeading,
                        endPoint: .bottomTrailing
                    )
                    .ignoresSafeArea()
                )
                .navigationTitle("Measurement")
            } else {
                Text("This measurement is no longer available.")
                    .foregroundColor(.secondary)
                    .navigationTitle("Measurement")
            }
        }
    }

    private func formattedDuration(_ duration: TimeInterval) -> String {
        let formatter = DateComponentsFormatter()
        formatter.allowedUnits = duration >= 3600 ? [.hour, .minute, .second] : [.minute, .second]
        formatter.unitsStyle = .abbreviated
        formatter.zeroFormattingBehavior = .pad
        return formatter.string(from: max(duration, 0)) ?? "0s"
    }
}

private struct ChargerStandbyPowerMeasurementSnapshotView: View {
    let measurement: ChargerStandbyPowerMeasurementSummary

    var body: some View {
        VStack(spacing: 18) {
            stabilityCard
            projectionCard
            distributionCard
            statisticsCard
        }
    }

    private var stabilityCard: some View {
        VStack(alignment: .leading, spacing: 10) {
            HStack {
                VStack(alignment: .leading, spacing: 4) {
                    Text(measurement.isStable ? "Enough Samples" : "Still Settling")
                        .font(.headline)
                    Text("Saved \(measurement.endedAt.format())")
                        .font(.caption)
                        .foregroundColor(.secondary)
                }

                Spacer()

                Text(measurement.isStable ? "Ready" : "Live")
                    .font(.caption.weight(.semibold))
                    .padding(.horizontal, 10)
                    .padding(.vertical, 6)
                    .foregroundColor(measurement.isStable ? .green : .orange)
                    .meterCard(
                        tint: measurement.isStable ? .green : .orange,
                        fillOpacity: 0.10,
                        strokeOpacity: 0.16,
                        cornerRadius: 999
                    )
            }

            Text("\(measurement.averagePowerWatts.format(decimalDigits: 3)) W")
                .font(.system(.largeTitle, design: .rounded).weight(.bold))
                .monospacedDigit()

            Text(
                "Recent drift: \((measurement.stabilityDeltaWatts * 1000).format(decimalDigits: 2)) mW, tolerance \((measurement.stabilityToleranceWatts * 1000).format(decimalDigits: 2)) mW over \(measurement.sampleCount) samples."
            )
            .font(.footnote)
            .foregroundColor(.secondary)
        }
        .frame(maxWidth: .infinity, alignment: .leading)
        .padding(18)
        .meterCard(
            tint: measurement.isStable ? .green : .orange,
            fillOpacity: 0.18,
            strokeOpacity: 0.24
        )
    }

    private var projectionCard: some View {
        MeterInfoCardView(
            title: "Consumption Projection",
            infoMessage: "These projections extrapolate only from the measured standby average. They do not say anything about charger behaviour under load.",
            tint: .teal
        ) {
            MeterInfoRowView(label: "Average Power", value: "\(measurement.averagePowerWatts.format(decimalDigits: 3)) W")
            MeterInfoRowView(label: "24 Hours", value: standbyEnergyLabel(measurement.projectedDailyEnergyWh))
            MeterInfoRowView(label: "7 Days", value: standbyEnergyLabel(measurement.projectedWeeklyEnergyWh))
            MeterInfoRowView(label: "30 Days", value: standbyEnergyLabel(measurement.projectedMonthlyEnergyWh))
            MeterInfoRowView(label: "1 Year", value: standbyEnergyLabel(measurement.projectedYearlyEnergyWh))
        }
    }

    private var distributionCard: some View {
        MeterInfoCardView(
            title: "Distribution",
            infoMessage: "Bars show how often each power interval appeared. The curve overlays a normal approximation around the observed mean and deviation.",
            tint: .orange
        ) {
            StandbyPowerHistogramView(
                histogram: measurement.histogram,
                averagePowerWatts: measurement.averagePowerWatts,
                standardDeviationPowerWatts: measurement.standardDeviationPowerWatts,
                tint: .orange
            )
            .frame(height: 220)

            if let firstBin = measurement.histogram.first, let lastBin = measurement.histogram.last {
                HStack {
                    Text("\(firstBin.lowerBoundWatts.format(decimalDigits: 3)) W")
                    Spacer()
                    Text("\(lastBin.upperBoundWatts.format(decimalDigits: 3)) W")
                }
                .font(.caption)
                .foregroundColor(.secondary)
                .monospacedDigit()
            }
        }
    }

    private var statisticsCard: some View {
        MeterInfoCardView(title: "Interesting Stats", tint: .indigo) {
            MeterInfoRowView(label: "Median", value: "\(measurement.medianPowerWatts.format(decimalDigits: 3)) W")
            MeterInfoRowView(label: "Minimum", value: "\(measurement.minimumPowerWatts.format(decimalDigits: 3)) W")
            MeterInfoRowView(label: "Maximum", value: "\(measurement.maximumPowerWatts.format(decimalDigits: 3)) W")
            MeterInfoRowView(label: "Spread σ", value: "\(measurement.standardDeviationPowerWatts.format(decimalDigits: 4)) W")
            MeterInfoRowView(label: "Variation", value: "\(Int((measurement.coefficientOfVariation * 100).rounded()))%")
            MeterInfoRowView(label: "Mean Current", value: "\(measurement.averageCurrentAmps.format(decimalDigits: 3)) A")
            MeterInfoRowView(label: "Mean Voltage", value: "\(measurement.averageVoltageVolts.format(decimalDigits: 3)) V")
            MeterInfoRowView(label: "Power Density", value: "\(measurement.averagePowerWatts.format(decimalDigits: 3)) W steady")
        }
    }

    private func standbyEnergyLabel(_ wattHours: Double) -> String {
        if wattHours >= 1000 {
            return "\((wattHours / 1000).format(decimalDigits: 3)) kWh"
        }
        return "\(wattHours.format(decimalDigits: 2)) Wh"
    }
}