Bluetooth Channel Sounding for Accessory Finding

import SwiftUI
import CoreBluetooth

// MARK: - Channel Sounding Delegate Handler
class ChannelSoundingManager: NSObject, ObservableObject {
    @Published var distanceMeters: Double? = nil
    @Published var statusMessage: String = "Idle"

    private var centralManager: CBCentralManager!
    private var targetPeripheral: CBPeripheral?

    override init() {
        super.init()
        centralManager = CBCentralManager(delegate: nil, queue: .main)
    }

    func startSession(with peripheral: CBPeripheral) {
        guard CBCentralManager.supportsFeatures(.channelSounding) else {
            statusMessage = "Channel Sounding not supported on this device"
            return
        }
        targetPeripheral = peripheral
        peripheral.delegate = self
        peripheral.startChannelSoundingSession()
        statusMessage = "Channel Sounding session started"
    }

    func stopSession() {
        targetPeripheral?.cancelChannelSoundingSession()
        statusMessage = "Session cancelled"
    }
}

// MARK: - CBPeripheralDelegate
extension ChannelSoundingManager: CBPeripheralDelegate {
    func peripheral(_ peripheral: CBPeripheral,
                    didReceive results: CBChannelSoundingResult) {
        if let distance = results.distance {
            distanceMeters = distance
            statusMessage = String(format: "Distance: %.2f m", distance)
        } else {
            statusMessage = "Measurement returned nil distance"
        }
    }

    func peripheralDidCompleteChannelSoundingSession(_ peripheral: CBPeripheral) {
        statusMessage = "Session completed"
        distanceMeters = nil
    }
}

// MARK: - SwiftUI View
struct AccessoryDistanceView: View {
    @StateObject private var manager = ChannelSoundingManager()

    var body: some View {
        VStack(spacing: 24) {
            Text("Channel Sounding Demo")
                .font(.title2.bold())

            if let distance = manager.distanceMeters {
                Text(String(format: "📡 %.2f meters", distance))
                    .font(.largeTitle)
                    .monospacedDigit()
            } else {
                Text("—")
                    .font(.largeTitle)
                    .foregroundStyle(.secondary)
            }

            Text(manager.statusMessage)
                .font(.footnote)
                .foregroundStyle(.secondary)
                .multilineTextAlignment(.center)

            Button("Stop Session", role: .destructive) {
                manager.stopSession()
            }
            .buttonStyle(.borderedProminent)
        }
        .padding()
    }
}