Option 2: OAuth on Swift

import SwiftUI
import SmartSpectra
import AVFoundation

struct ContentView: View {
    private enum TraceWindow {
        static let rate = 120
        static let arterialWaveform = 240
        static let breathingWaveform = 180
    }

    private let sdk = SmartSpectraSDK.shared

    @State private var didAutoStart = false
    @State private var pulseRateBuffer: [MeasurementWithConfidence] = []
    @State private var breathingRateBuffer: [MeasurementWithConfidence] = []
    @State private var arterialPressureBuffer: [MeasurementWithConfidence] = []
    @State private var chestBuffer: [SmartSpectra.Measurement] = []
    @State private var abdomenBuffer: [SmartSpectra.Measurement] = []
    @State private var latestHrv: Hrv?
    @State private var latestExpressionScores: [ExpressionScore] = []

    init() {
        sdk.config.cameraPosition = .front
        sdk.config.imageOutputEnabled = true
        sdk.config.requestedMetrics =
            SmartSpectraConfig.breathingMetrics +
            SmartSpectraConfig.cardioMetrics + [
                .expressions,
            ]
    }

    private enum WaveformProminence {
        case primary
        case secondary
    }

    private var metrics: Metrics? { sdk.metrics }

    private var metricsUpdateToken: Int64 {
        [
            metrics?.cardio.pulseRate.last?.timestamp,
            metrics?.breathing.rate.last?.timestamp,
            metrics?.cardio.arterialPressureTrace.last?.timestamp,
            metrics?.breathing.upperTrace.last?.timestamp,
            metrics?.breathing.lowerTrace.last?.timestamp,
            metrics?.cardio.hrv.last?.timestamp,
            metrics?.face.expression.last?.timestamp,
        ]
        .compactMap { $0 }
        .max() ?? 0
    }

    private var pulseRateText: String {
        formatMetric(pulseRateBuffer.last.map { Double($0.value) }, digits: 0, suffix: " bpm")
    }

    private var breathingRateText: String {
        formatMetric(breathingRateBuffer.last.map { Double($0.value) }, digits: 0, suffix: " bpm")
    }

    private var hrvText: String {
        guard let value = latestHrv?.rmssd, value > 0 else { return "--" }
        return formatMetric(value, digits: 1, suffix: " ms")
    }

    private var latestExpressionScore: ExpressionScore? {
        latestExpressionScores.max(by: { $0.confidence < $1.confidence })
    }

    private var latestExpressionLabel: String {
        guard let score = latestExpressionScore else { return "--" }
        let name = String(expressionName(score.type).prefix(8))
        let paddedName = name + String(repeating: " ", count: max(0, 8 - name.count))
        let percent = confidenceText(score.confidence)
        let paddedPercent = String(repeating: " ", count: max(0, 4 - percent.count)) + percent
        return "\(paddedName) \(paddedPercent)"
    }

    private var pulseConfidenceColor: Color {
        confidenceColor(pulseRateBuffer.last?.confidence)
    }

    private var breathingConfidenceColor: Color {
        confidenceColor(breathingRateBuffer.last?.confidence)
    }

    private var arterialPressureSamples: [Double] {
        arterialPressureBuffer.map { Double($0.value) }
    }

    private var chestSamples: [Double] {
        chestBuffer.map { Double($0.value) }
    }

    private var abdomenSamples: [Double] {
        abdomenBuffer.map { Double($0.value) }
    }

    private var statusText: String {
        switch sdk.processingStatus {
        case .idle: return "Idle"
        case .starting: return "Starting"
        case .running: return "Running"
        case .stopping: return "Stopping"
        case .error: return "Error"
        @unknown default: return "Unknown"
        }
    }

    private var validationTitle: String {
        guard let validationStatus = sdk.validationStatus else { return "Waiting" }
        return validationStatus.hint
    }

    private var statusColor: Color {
        switch sdk.processingStatus {
        case .running: return .green
        case .starting, .stopping: return .orange
        case .error: return .red
        case .idle: return .gray
        @unknown default: return .gray
        }
    }

    private var validationColor: Color {
        guard let validationStatus = sdk.validationStatus else { return .gray }
        switch validationStatus.code {
        case .ok: return .green
        case .cameraTuning: return .orange
        default: return .yellow
        }
    }

    var body: some View {
        GeometryReader { geometry in
            let compact = geometry.size.height < 820
            let horizontalPadding: CGFloat = compact ? 12 : 16
            let topSpacing: CGFloat = compact ? 8 : 12
            let previewHeight = min(max(geometry.size.height * 0.26, 190), 250)

            VStack(spacing: topSpacing) {
                statusBar(compact: compact)
                    .zIndex(1)

                previewCard
                    .frame(height: previewHeight)
                    .zIndex(0)

                HStack(spacing: topSpacing) {
                    metricCard(
                        title: "Pulse Rate",
                        value: pulseRateText,
                        valueColor: pulseConfidenceColor,
                        accent: .red,
                        compact: compact
                    )
                    metricCard(
                        title: "Breathing Rate",
                        value: breathingRateText,
                        valueColor: breathingConfidenceColor,
                        accent: .cyan,
                        compact: compact
                    )
                }
                .frame(maxHeight: compact ? 82 : 92)

                HStack(spacing: topSpacing) {
                    metricCard(
                        title: "HRV RMSSD",
                        value: hrvText,
                        valueColor: .white,
                        accent: .mint,
                        compact: compact
                    )
                    metricCard(
                        title: "Expression",
                        value: latestExpressionLabel,
                        valueColor: .white,
                        accent: .orange,
                        compact: compact,
                        monospacedValue: true
                    )
                }
                .frame(maxHeight: compact ? 82 : 92)

                waveformCard(
                    title: "Arterial Pressure",
                    samples: arterialPressureSamples,
                    accent: .purple,
                    compact: compact,
                    prominence: .primary
                )
                .frame(height: compact ? 154 : 182)

                HStack(spacing: topSpacing) {
                    waveformCard(
                        title: "Chest Waveform",
                        samples: chestSamples,
                        accent: .cyan,
                        compact: compact,
                        prominence: .secondary
                    )
                    waveformCard(
                        title: "Abdomen Waveform",
                        samples: abdomenSamples,
                        accent: .blue,
                        compact: compact,
                        prominence: .secondary
                    )
                }
                .frame(height: compact ? 130 : 146)

                guidanceText
            }
            .padding(.horizontal, horizontalPadding)
            .padding(.vertical, compact ? 10 : 14)
            .background(backgroundGradient.ignoresSafeArea())
        }
        .task {
            await startIfNeeded()
        }
        .task(id: metricsUpdateToken) {
            mergeCurrentMetrics()
        }
    }

    // The SDK's `hint` is written for end users — surface it as-is.
    private var guidanceText: some View {
        Text(sdk.validationStatus?.hint ?? "Getting ready\u{2026}")
            .font(.footnote)
            .foregroundStyle(.white.opacity(0.85))
            .multilineTextAlignment(.center)
            .frame(maxWidth: .infinity)
            .accessibilityLabel("Measurement guidance")
    }

    private var previewCard: some View {
        ZStack {
            if let image = sdk.imageOutput {
                Image(uiImage: image)
                    .resizable()
                    .aspectRatio(contentMode: .fill)
                    .frame(maxWidth: .infinity, maxHeight: .infinity)
                    .clipped()
            } else {
                LinearGradient(
                    colors: [Color(red: 0.16, green: 0.24, blue: 0.46), Color.black],
                    startPoint: .topLeading,
                    endPoint: .bottomTrailing
                )
                VStack(spacing: 10) {
                    Image(systemName: "camera.viewfinder")
                        .font(.system(size: 40, weight: .semibold))
                    Text("Camera preview will appear here")
                        .font(.headline)
                }
                .foregroundStyle(.white.opacity(0.92))
            }

            LinearGradient(
                colors: [.black.opacity(0.68), .black.opacity(0.12), .clear],
                startPoint: .bottom,
                endPoint: .top
            )
        }
        .frame(maxWidth: .infinity, maxHeight: .infinity)
        .clipShape(RoundedRectangle(cornerRadius: 26, style: .continuous))
        .overlay(
            RoundedRectangle(cornerRadius: 26, style: .continuous)
                .stroke(.white.opacity(0.12), lineWidth: 1)
        )
        .shadow(color: .black.opacity(0.35), radius: 18, x: 0, y: 10)
    }

    private func statusBar(compact: Bool) -> some View {
        HStack(spacing: compact ? 8 : 10) {
            badge(title: "Status", value: statusText, color: statusColor)
            badge(title: "Validation", value: validationTitle, color: validationColor)
            Spacer(minLength: 8)
            Button(action: toggleMeasurement) {
                Text(sdk.processingStatus == .running ? "Stop" : "Start")
                    .font(.caption.bold())
                    .padding(.horizontal, compact ? 14 : 18)
                    .padding(.vertical, 10)
                    .background(.white, in: Capsule())
                    .foregroundStyle(.black)
            }
        }
    }

    private func metricCard(
        title: String,
        value: String,
        valueColor: Color,
        accent: Color,
        compact: Bool,
        monospacedValue: Bool = false
    ) -> some View {
        VStack(alignment: .leading, spacing: compact ? 6 : 8) {
            HStack(spacing: 6) {
                Circle()
                    .fill(accent)
                    .frame(width: 8, height: 8)
                Text(title)
                    .font(.caption.weight(.semibold))
                    .foregroundStyle(.white)
            }

            Text(value)
                .font(.system(size: compact ? 21 : 24, weight: .bold, design: monospacedValue ? .monospaced : .rounded))
                .foregroundStyle(valueColor)
                .monospacedDigit()
                .lineLimit(1)
                .minimumScaleFactor(0.7)

        }
        .dashboardCard()
    }

    private func waveformCard(
        title: String,
        samples: [Double],
        accent: Color,
        compact: Bool,
        prominence: WaveformProminence
    ) -> some View {
        VStack(alignment: .leading, spacing: compact ? 6 : 8) {
            VStack(alignment: .leading, spacing: 2) {
                Text(title)
                    .font(.caption.weight(.semibold))
                    .foregroundStyle(.white)
            }

            ZStack {
                RoundedRectangle(cornerRadius: 14, style: .continuous)
                    .fill(accent.opacity(0.12))

                if samples.count > 1 {
                    WaveformView(
                        samples: samples,
                        strokeColor: accent,
                        verticalPaddingFraction: prominence == .primary ? 0.14 : 0.08
                    )
                    .padding(prominence == .primary ? 8 : 10)
                }
            }
            .frame(maxHeight: .infinity)
            .overlay(
                RoundedRectangle(cornerRadius: 14, style: .continuous)
                    .stroke(accent.opacity(0.3), lineWidth: 1)
            )
        }
        .dashboardCard()
    }

    private func badge(title: String, value: String, color: Color) -> some View {
        HStack(spacing: 6) {
            Circle()
                .fill(color)
                .frame(width: 8, height: 8)
            Text("\(title): \(value)")
                .font(.caption.weight(.semibold))
        }
        .padding(.horizontal, 10)
        .padding(.vertical, 8)
        .background(.white.opacity(0.12), in: Capsule())
        .foregroundStyle(.white)
    }

    private func mergeCurrentMetrics() {
        guard let metrics else { return }

        if !metrics.cardio.pulseRate.isEmpty {
            pulseRateBuffer.appendProtoArray(contentsOf: metrics.cardio.pulseRate)
            pulseRateBuffer = Array(pulseRateBuffer.suffix(TraceWindow.rate))
        }

        if !metrics.breathing.rate.isEmpty {
            breathingRateBuffer.appendProtoArray(contentsOf: metrics.breathing.rate)
            breathingRateBuffer = Array(breathingRateBuffer.suffix(TraceWindow.rate))
        }

        if !metrics.cardio.arterialPressureTrace.isEmpty {
            arterialPressureBuffer.appendProtoArray(contentsOf: metrics.cardio.arterialPressureTrace)
            arterialPressureBuffer = Array(arterialPressureBuffer.suffix(TraceWindow.arterialWaveform))
        }

        if !metrics.breathing.upperTrace.isEmpty {
            chestBuffer.appendProtoArray(contentsOf: metrics.breathing.upperTrace)
            chestBuffer = Array(chestBuffer.suffix(TraceWindow.breathingWaveform))
        }

        if !metrics.breathing.lowerTrace.isEmpty {
            abdomenBuffer.appendProtoArray(contentsOf: metrics.breathing.lowerTrace)
            abdomenBuffer = Array(abdomenBuffer.suffix(TraceWindow.breathingWaveform))
        }

        if let hrv = metrics.cardio.hrv.last {
            latestHrv = hrv
        }

        if let scores = metrics.face.expression.last?.scores, !scores.isEmpty {
            latestExpressionScores = scores
        }
    }

    private func resetBuffers() {
        pulseRateBuffer.removeAll(keepingCapacity: true)
        breathingRateBuffer.removeAll(keepingCapacity: true)
        arterialPressureBuffer.removeAll(keepingCapacity: true)
        chestBuffer.removeAll(keepingCapacity: true)
        abdomenBuffer.removeAll(keepingCapacity: true)
        latestHrv = nil
        latestExpressionScores.removeAll(keepingCapacity: true)
    }

    private func toggleMeasurement() {
        Task {
            if sdk.processingStatus == .running || sdk.processingStatus == .starting {
                try? await sdk.stop()
            } else {
                resetBuffers()
                try? await sdk.start()
            }
        }
    }

    private func startIfNeeded() async {
        guard !didAutoStart else { return }
        didAutoStart = true
        guard sdk.processingStatus == .idle else { return }
        resetBuffers()
        try? await sdk.start()
    }

    private func confidenceText(_ confidence: Float?) -> String {
        guard let confidence, confidence.isFinite else { return "--" }
        let percent = min(max(Double(confidence), 0), 100)
        return "\(Int(percent.rounded()))%"
    }

    private func confidenceColor(_ confidence: Float?) -> Color {
        guard let confidence, confidence.isFinite else { return .white.opacity(0.65) }
        let percent = min(max(Double(confidence), 0), 100)
        switch percent {
        case 85...:
            return .green
        case 60..<85:
            return .yellow
        default:
            return .red
        }
    }

    private func formatMetric(_ value: Double?, digits: Int = 0, suffix: String = "") -> String {
        guard let value else { return "--" }
        if digits == 0 {
            return "\(Int(value.rounded()))\(suffix)"
        }
        return String(format: "% .\(digits)f", value).replacingOccurrences(of: " ", with: "") + suffix
    }

    private func expressionName(_ type: ExpressionType) -> String {
        switch type {
        case .unspecified: return "Unspecified"
        case .angry: return "Angry"
        case .contempt: return "Contempt"
        case .disgust: return "Disgust"
        case .fear: return "Fear"
        case .happy: return "Happy"
        case .neutral: return "Neutral"
        case .sad: return "Sad"
        case .surprise: return "Surprise"
        case .UNRECOGNIZED(_): return "Unknown"
        @unknown default: return "Unknown"
        }
    }

    private var backgroundGradient: LinearGradient {
        LinearGradient(
            colors: [
                Color(red: 0.03, green: 0.05, blue: 0.12),
                Color(red: 0.07, green: 0.09, blue: 0.18),
                Color.black,
            ],
            startPoint: .topLeading,
            endPoint: .bottomTrailing
        )
    }
}

private struct WaveformView: View {
    let samples: [Double]
    let strokeColor: Color
    let verticalPaddingFraction: Double

    var body: some View {
        GeometryReader { geometry in
            Path { path in
                guard samples.count > 1 else { return }

                let minValue = samples.min() ?? 0
                let maxValue = samples.max() ?? 1
                let rawRange = max(maxValue - minValue, 0.0001)
                let padding = rawRange * verticalPaddingFraction
                let lowerBound = minValue - padding
                let upperBound = maxValue + padding
                let range = max(upperBound - lowerBound, 0.0001)

                for (index, sample) in samples.enumerated() {
                    let x = geometry.size.width * CGFloat(index) / CGFloat(samples.count - 1)
                    let normalized = (sample - lowerBound) / range
                    let y = geometry.size.height * (1 - normalized)

                    if index == 0 {
                        path.move(to: CGPoint(x: x, y: y))
                    } else {
                        path.addLine(to: CGPoint(x: x, y: y))
                    }
                }
            }
            .stroke(strokeColor, style: StrokeStyle(lineWidth: 2.2, lineCap: .round, lineJoin: .round))
        }
    }
}

private extension View {
    func dashboardCard() -> some View {
        self
            .padding(12)
            .background(
                RoundedRectangle(cornerRadius: 20, style: .continuous)
                    .fill(Color.white.opacity(0.08))
            )
            .overlay(
                RoundedRectangle(cornerRadius: 20, style: .continuous)
                    .stroke(Color.white.opacity(0.08), lineWidth: 1)
            )
    }
}