voice-cat/clients/apple/iOS/VoiceCatiOS/IOSAudioRouter.swift

import AVFoundation
import os
import VoiceCatCore

private let logger = Logger(subsystem: "cat.voice.VoiceCatiOS", category: "IOSAudioRouter")

/// iOS audio routing layer — drives all iOS audio route selection via `AVAudioSession`
/// *before* the core (miniaudio) opens its device. This class is the sole owner of the
/// session: miniaudio does NOT touch `AVAudioSession` on iOS, because the core opens its
/// devices through a `ma_context` configured with `sessionCategory = none` +
/// `noAudioSessionActivate/Deactivate` (see `AudioEngine::make_context_config` in
/// `core/src/audio/audio_engine.cpp`). Without that, miniaudio's default path resets the
/// category to `Record`/`Playback` with no options on every device open, wiping
/// `.allowBluetoothA2DP`/`.playAndRecord` and killing headphone/A2DP output — so that
/// config must stay in place. All iOS audio routing (input port selection, mic
/// orientation/polar patterns, HFP vs A2DP, measurement/raw mode, stereo capture) must be
/// driven from here.
///
/// The three user-facing choices:
///   1. **Input port** — which physical input (built-in mic, Bluetooth HFP, headset,
///      USB, AirPlay). For the built-in mic, a sub-selection of **data source**
///      (orientation: front/back/top/bottom) and **polar pattern**
///      (omni/cardioid/subcardioid/bidirectional).
///   2. **Bluetooth mode** — how Bluetooth headsets are handled:
///      - "BT HFP voice" (`.allowBluetoothHFP` + `.allowBluetoothA2DP`): both profiles
///        allowed, iOS picks HFP for two-way mic or A2DP for output-only. Mono, AEC on.
///      - "Built-in Mic + BT A2DP stereo" (`.allowBluetoothA2DP` only): stereo output,
///        built-in mic, no HFP processing.
///      - "Built-in Mic + Speaker" (neither): no Bluetooth at all.
///   3. **Mic processing mode** — Standard (`.voiceChat`: AEC/AGC/HPF on) or
///      Raw/Studio (`.measurement`: all processing off). Raw mode is allowed always
///      but shows a warning when the output route is the speaker (echo risk, no AEC).
///
/// Additionally, **stereo capture** (2-channel built-in mic) is enabled by switching the
/// built-in mic's data source to the `.stereo` polar pattern. The recipe is:
/// `setPreferredDataSource(.stereo source)` + `setPreferredPolarPattern(.stereo)` +
/// `setPreferredInput(built-in mic)` + `setInputDataSource(stereo source)`. The channel
/// count itself must NOT be requested via `setPreferredInputNumberOfChannels(2)` — that
/// session-level call collapses the A2DP output route. Instead the core is told to open the
/// device with 2 channels via `vc_set_capture_channels(streamId, 2)`, and the AVAudioSession
/// input anchor (`setPreferredInput` + `setInputDataSource`) keeps the route stable during
/// the HFP→A2DP and mono→stereo reconfigurations.
///
/// Voice Isolation / Wide Spectrum (iOS 17+/18+) are user-toggleable in Control Center
/// for `.voiceChat` apps — surfaced as a hint, not a programmatic toggle.
///
/// All choices are persisted in `UserDefaults` and re-applied on route changes.
@MainActor
final class IOSAudioRouter: ObservableObject {

    static let shared = IOSAudioRouter()

    // MARK: - Published state (drives SettingsView)

    @Published var inputPorts: [IOSAudioInputPort] = []
    @Published var outputRoutes: [IOSAudioOutputRoute] = []
    @Published var bluetoothMode: BluetoothMode = .btHfpVoice
    @Published var micMode: MicMode = .standard
    @Published var captureChannels: CaptureChannels = .mono
    @Published var selectedInputPortId: String?
    @Published var selectedDataSourceId: String?
    @Published var selectedPolarPattern: String?
    @Published var showsRawModeSpeakerWarning: Bool = false
    @Published var showsA2dpNoAecWarning: Bool = false
    @Published var hasBluetoothDevice: Bool = false
    @Published var hasWiredHeadset: Bool = false

    /// Audio presets — sensible combinations of settings for common scenarios.
    /// The app is about choice: users can pick a preset for a quick start, then
    /// fine-tune individual settings under "Advanced Audio".
    enum AudioPreset: String, CaseIterable, Identifiable {
        /// Standard iOS VoIP experience: AEC/AGC/HPF on, mono, system picks best route
        /// (BT HFP if connected, wired if connected, speaker if nothing). Always available.
        case voiceChat = "Voice Chat"
        /// Stereo built-in mic capture (front+back capsules). A2DP output if BT is connected,
        /// else built-in speaker / wired. Standard processing (no AEC — stereo needs a non-VPIO
        /// mode). Always available.
        case stereoMic = "Stereo Mic"
        /// Maximum fidelity: stereo mic, no AEC/AGC/HPF (raw mode). A2DP output if BT connected,
        /// else speaker/wired. Always available. Echo risk on speaker.
        case studio = "Studio (No Processing)"
        /// Bluetooth HFP: BT mic + BT output, AEC on, mono. Only when BT is connected.
        case bluetoothHeadset = "Bluetooth Headset (HFP)"
        /// A2DP stereo output + built-in mono mic, AEC off. Only when BT is connected. (For
        /// A2DP output + stereo mic, use the Stereo Mic preset while BT is connected.)
        case btHeadphonesMonoMic = "BT Headphones + Mono Mic"
        /// Wired headset/earpods: wired output + wired mic (or built-in), AEC on, mono.
        /// Only when a wired audio device is connected.
        case wiredHeadset = "Wired Headset"
        /// Settings don't match any preset — user has tweaked advanced controls.
        case custom = "Custom"

        var id: String { rawValue }

        var requiresBluetooth: Bool {
            switch self {
            case .bluetoothHeadset, .btHeadphonesMonoMic: return true
            default: return false
            }
        }

        var requiresWired: Bool {
            self == .wiredHeadset
        }

        var bluetoothMode: BluetoothMode {
            switch self {
            case .voiceChat, .bluetoothHeadset: return .btHfpVoice
            // A2DP output when BT is connected; falls back to speaker/wired when it isn't.
            case .stereoMic, .studio, .btHeadphonesMonoMic: return .builtInMicBtA2dp
            case .wiredHeadset: return .builtInMicSpeaker
            case .custom: return .builtInMicSpeaker  // placeholder
            }
        }

        var captureChannels: CaptureChannels {
            switch self {
            case .stereoMic, .studio: return .stereo
            default: return .mono
            }
        }

        var micMode: MicMode {
            switch self {
            case .studio: return .raw
            default: return .standard
            }
        }

        /// Whether this preset explicitly selects the built-in mic port.
        var usesBuiltInMic: Bool {
            switch self {
            case .stereoMic, .studio, .btHeadphonesMonoMic: return true
            default: return false
            }
        }
    }

    enum BluetoothMode: String, CaseIterable, Identifiable {
        case btHfpVoice = "BT HFP Voice"
        case builtInMicBtA2dp = "Built-in Mic + BT A2DP"
        case builtInMicSpeaker = "Built-in Mic + Speaker"
        var id: String { rawValue }
    }

    enum MicMode: String, CaseIterable, Identifiable {
        case standard = "Standard"
        case raw = "Raw / Studio"
        var id: String { rawValue }
    }

    enum CaptureChannels: String, CaseIterable, Identifiable {
        case mono = "Mono"
        case stereo = "Stereo"
        var id: String { rawValue }
        var channelCount: UInt32 { self == .stereo ? 2 : 1 }
    }

    // MARK: - UserDefaults keys

    private let kBluetoothMode = "cat.voice.audio.bluetoothMode"
    private let kMicMode = "cat.voice.audio.micMode"
    private let kCaptureChannels = "cat.voice.audio.captureChannels"
    private let kInputPortId = "cat.voice.audio.inputPortId"
    private let kDataSourceId = "cat.voice.audio.dataSourceId"
    private let kPolarPattern = "cat.voice.audio.polarPattern"
    private let kPreset = "cat.voice.audio.preset"

    /// Re-entrancy guard: setCategory/setPreferredInput/etc. trigger route-change
    /// notifications synchronously on the same thread. Without this guard,
    /// handleRouteChange → applyConfiguration → setCategory → route-change notification
    /// → handleRouteChange → applyConfiguration → ... creates an infinite loop that
    /// burns CPU and cycles the audio session on/off (the "glitching" bug).
    private var isApplyingConfiguration = false

    private init() {}

    // MARK: - Load / refresh from AVAudioSession

    /// Refresh the published input port list and output route list from the current
    /// AVAudioSession state. Call after any route change or when the settings view appears.
    func refreshRoutes() {
        let session = AVAudioSession.sharedInstance()
        let currentInput = session.preferredInput
        let currentDataSource = currentInput?.preferredDataSource?.dataSourceID ?? nil
        let currentPolarPattern = currentInput?.preferredDataSource?.preferredPolarPattern?.rawValue

        inputPorts = (session.availableInputs ?? []).map { port in
            let dataSources = port.dataSources?.map { ds in
                IOSAudioDataSource(
                    id: String(describing: ds.dataSourceID),
                    name: ds.dataSourceName,
                    polarPatterns: ds.supportedPolarPatterns?.map { $0.rawValue },
                    isSelected: currentDataSource == ds.dataSourceID,
                    selectedPolarPattern: currentPolarPattern
                )
            }
            return IOSAudioInputPort(
                id: port.uid,
                name: port.portName,
                portType: port.portType.rawValue,
                dataSources: dataSources,
                isSelected: currentInput?.uid == port.uid
            )
        }

        outputRoutes = session.currentRoute.outputs.map { port in
            IOSAudioOutputRoute(
                id: port.uid,
                name: port.portName,
                portType: port.portType.rawValue
            )
        }

        if selectedInputPortId == nil {
            selectedInputPortId = currentInput?.uid ?? inputPorts.first?.id
        }
        if selectedDataSourceId == nil {
            selectedDataSourceId = currentDataSource.map { String(describing: $0) }
        }
        if selectedPolarPattern == nil {
            selectedPolarPattern = currentPolarPattern
        }

        updateWarnings()
        detectAudioDevices()
    }

    /// Detect connected audio devices — Bluetooth (A2DP/HFP) and wired (headphones,
    /// headset mic, USB audio). Drives which presets are shown: BT presets only appear
    /// when a BT device is connected, wired presets only when a wired device is connected.
    /// This avoids confusing users with irrelevant options.
    private func detectAudioDevices() {
        let session = AVAudioSession.sharedInstance()
        let route = session.currentRoute
        let inputs = session.availableInputs ?? []

        // Bluetooth: check current route + available inputs
        let hasBTOutput = route.outputs.contains {
            $0.portType == .bluetoothA2DP || $0.portType == .bluetoothHFP
        }
        let hasBTInput = route.inputs.contains { $0.portType == .bluetoothHFP }
        let hasBTAvailable = inputs.contains {
            $0.portType == .bluetoothHFP || $0.portType == .bluetoothA2DP
        }
        let wasBT = hasBluetoothDevice
        hasBluetoothDevice = hasBTOutput || hasBTInput || hasBTAvailable
        if hasBluetoothDevice != wasBT {
            logger.info("bluetooth device \(self.hasBluetoothDevice ? "connected" : "disconnected")")
        }

        // Wired: headphones, headset mic, USB audio (earpods, Lightning/USB-C headsets)
        let hasWiredOutput = route.outputs.contains {
            $0.portType == .headphones || $0.portType == .usbAudio
        }
        let hasWiredInput = route.inputs.contains {
            $0.portType == .headsetMic || $0.portType == .usbAudio
        }
        let hasWiredAvailable = inputs.contains {
            $0.portType == .headphones || $0.portType == .headsetMic || $0.portType == .usbAudio
        }
        let wasWired = hasWiredHeadset
        hasWiredHeadset = hasWiredOutput || hasWiredInput || hasWiredAvailable
        if hasWiredHeadset != wasWired {
            logger.info("wired headset \(self.hasWiredHeadset ? "connected" : "disconnected")")
        }
    }

    /// The presets available given the current device connection state.
    /// Always includes Voice Chat, Stereo Mic, Studio, and Custom. BT presets only when
    /// a Bluetooth device is connected. Wired preset only when a wired device is connected.
    var availablePresets: [AudioPreset] {
        AudioPreset.allCases.filter { preset in
            if preset == .custom { return true }
            if preset.requiresBluetooth && !hasBluetoothDevice { return false }
            if preset.requiresWired && !hasWiredHeadset { return false }
            return true
        }
    }

    /// Which preset matches the current settings, or .custom if nothing matches.
    /// Checks device-specific presets first (BT, wired) so that e.g. when BT is connected
    /// and settings match "Bluetooth Headset", it returns that instead of the equivalent
    /// "Voice Chat" (which has the same bluetoothMode/micMode/channels but is more general).
    var activePreset: AudioPreset {
        // Check device-specific presets first (most specific → least specific)
        let order: [AudioPreset] = [
            .bluetoothHeadset, .btHeadphonesMonoMic,
            .wiredHeadset,
            .voiceChat, .stereoMic, .studio,
        ]
        for preset in order {
            if bluetoothMode == preset.bluetoothMode
               && captureChannels == preset.captureChannels
               && micMode == preset.micMode {
                // Don't match a BT preset if no BT is connected — fall through to Voice Chat
                if preset.requiresBluetooth && !hasBluetoothDevice { continue }
                if preset.requiresWired && !hasWiredHeadset { continue }
                return preset
            }
        }
        return .custom
    }

    // MARK: - Apply configuration

    /// Apply the full audio configuration to AVAudioSession. Call this before the core
    /// opens its capture device (i.e. before `startMicStream` → `activateForStreaming`).
    /// Re-entrant-safe: if a route-change notification fires synchronously during a
    /// `setCategory`/`setPreferredInput` call, the guard prevents re-entry.
    func applyConfiguration() {
        guard !isApplyingConfiguration else {
            logger.debug("applyConfiguration skipped — already applying (re-entrancy guard)")
            return
        }
        isApplyingConfiguration = true
        defer { isApplyingConfiguration = false }

        let session = AVAudioSession.sharedInstance()

        // 1. Build category options from bluetooth mode.
        //    .mixWithOthers is ALWAYS set — it keeps other audio (notably VoiceOver, which a
        //    blind user needs to operate the phone) audible while our session is active. Never
        //    drop it.
        //    .defaultToSpeaker is set ONLY for the speaker preset. It forces output to the
        //    built-in speaker instead of the receiver — but it also actively breaks A2DP
        //    routing in .playAndRecord, so it must NOT be set for the A2DP or HFP presets.
        //    .allowAirPlay is added to the Bluetooth presets so AirPlay output also works.
        var options: AVAudioSession.CategoryOptions = [.mixWithOthers]
        switch bluetoothMode {
        case .btHfpVoice:
            // Voice Chat: allow BOTH HFP and A2DP, let iOS pick the right profile for the
            // connected device. HFP and A2DP must NOT be made mutually exclusive (HFP-only)
            // — that blocks A2DP headphones from receiving audio. HFP is preferred (the system
            // uses it when a two-way mic path is needed); A2DP stays available for output-only.
            options.insert(.allowBluetoothHFP)
            options.insert(.allowBluetoothA2DP)
            options.insert(.allowAirPlay)
        case .builtInMicBtA2dp:
            // A2DP output only (no HFP). With HFP disabled the Bluetooth device can only be
            // an OUTPUT (A2DP), so the system routes the mic to the built-in mic — exactly
            // what we want for "built-in mic + A2DP output", in either mono OR stereo.
            options.insert(.allowBluetoothA2DP)
            options.insert(.allowAirPlay)
        case .builtInMicSpeaker:
            // Built-in mic + speaker/wired output only. Prefer speaker over the receiver.
            options.insert(.defaultToSpeaker)
        }

        // 2. Set category + mode, chosen per scenario:
        //    - Stereo capture: .default — .voiceChat (the AEC/VPIO path) forces MONO, so stereo
        //      is only possible in a non-VPIO mode. .default supports multi-capsule stereo AND
        //      keeps the A2DP output route alive.
        //    - Mono raw/studio: .measurement — all system processing off.
        //    - Mono + A2DP output: .videoRecording — keeps A2DP output without VPIO (no AEC).
        //    - Mono standard (HFP or speaker): .voiceChat — hardware AEC/AGC/HPF.
        let mode: AVAudioSession.Mode
        if captureChannels == .stereo {
            mode = .default
        } else if micMode == .raw {
            mode = .measurement
        } else if bluetoothMode == .builtInMicBtA2dp {
            mode = .videoRecording
        } else {
            mode = .voiceChat
        }

        do {
            try session.setCategory(.playAndRecord, mode: mode, options: options)
            logger.info("setCategory ok — mode=\(self.modeLabel(mode)), bt=\(self.bluetoothMode.rawValue), ch=\(self.captureChannels.rawValue), options=\(self.optionsLabel(options))")
        } catch {
            logger.error("setCategory failed: \(error.localizedDescription)")
        }

        // 3. Input & mic-capsule configuration.
        if captureChannels == .stereo {
            // Stereo: enable the built-in mic's .stereo polar pattern AND anchor the input
            // route explicitly via setPreferredInput + setInputDataSource. With HFP disabled
            // the system routes input to the built-in mic, but without the explicit
            // preferred-input anchor the route can collapse during the mode switch
            // (.voiceChat → .default) and the output dies. The channel count is requested by
            // miniaudio at the audio-unit level (vc_set_capture_channels), NOT via
            // setPreferredInputNumberOfChannels(2) — that call collapses the A2DP output route.
            configureStereoCapture(session: session)
        } else if let portId = selectedInputPortId, !portId.isEmpty,
                  let port = session.availableInputs?.first(where: { $0.uid == portId }) {
            // Mono with an explicit input-port selection (advanced settings).
            do {
                try session.setPreferredInput(port)
                logger.info("setPreferredInput ok — \(port.portName)")
            } catch {
                logger.error("setPreferredInput failed: \(error.localizedDescription)")
            }
            configureMonoCapture(session: session, port: port)
        } else {
            // Mono, system-default input. Still clear any leftover .stereo capsule from a
            // prior stereo session so we actually return to mono.
            clearStereoPolarPattern(session: session)
        }

        updateWarnings()
    }

    /// Enable 2-channel capture on the built-in mic. The recipe that achieves stereo mic +
    /// A2DP Bluetooth output simultaneously:
    ///   1. `setPreferredDataSource(stereoSource)` on the built-in mic port
    ///   2. `setPreferredPolarPattern(.stereo)` on that data source
    ///   3. `setPreferredInput(builtIn)` — anchor the input route explicitly. Without this
    ///      anchor the route can collapse during the mode switch (.voiceChat → .default).
    ///   4. `setInputDataSource(stereoSource)` — commit the data source at the session level
    /// The channel count itself is requested by miniaudio at the audio-unit level via
    /// `vc_set_capture_channels(2)`. We must NOT call `setPreferredInputNumberOfChannels(2)`
    /// — that session-level call collapses the A2DP output route.
    private func configureStereoCapture(session: AVAudioSession) {
        guard let builtIn = session.availableInputs?.first(where: { $0.portType == .builtInMic })
        else {
            logger.warning("stereo requested but no built-in mic available — staying mono")
            return
        }
        guard let stereoSource = builtIn.dataSources?.first(where: {
            $0.supportedPolarPatterns?.contains(.stereo) == true
        }) else {
            logger.warning("stereo requested but built-in mic has no .stereo data source — staying mono")
            return
        }
        do {
            try builtIn.setPreferredDataSource(stereoSource)
            try stereoSource.setPreferredPolarPattern(.stereo)
            // Anchor the input route explicitly; without it the route can collapse during
            // the mode switch (.voiceChat → .default) and the A2DP output dies.
            try session.setPreferredInput(builtIn)
            // Commit the data source at the session level. setPreferredDataSource alone only
            // sets the port-level preference; setInputDataSource makes it the active source.
            try session.setInputDataSource(stereoSource)
            logger.info("stereo capsule enabled — source=\(stereoSource.dataSourceName), pattern=.stereo, input anchored")
        } catch {
            logger.error("stereo capsule setup failed: \(error.localizedDescription)")
        }
    }

    /// Configure mono capture on an explicitly selected port: apply the user's chosen data source
    /// (orientation) and polar pattern, resetting any prior `.stereo` pattern back to default.
    private func configureMonoCapture(session: AVAudioSession, port: AVAudioSessionPortDescription) {
        guard let dataSourceId = selectedDataSourceId, !dataSourceId.isEmpty,
              let dataSource = port.dataSources?.first(where: {
                  String(describing: $0.dataSourceID) == dataSourceId
              }) else {
            // No explicit capsule choice — make sure we're not stuck on a prior .stereo pattern.
            clearStereoPolarPattern(session: session)
            return
        }
        do {
            try port.setPreferredDataSource(dataSource)
            logger.info("setPreferredDataSource ok — \(dataSource.dataSourceName)")
        } catch {
            logger.error("setPreferredDataSource failed: \(error.localizedDescription)")
        }

        if let polarPattern = selectedPolarPattern, !polarPattern.isEmpty {
            let pattern = AVAudioSession.PolarPattern(rawValue: polarPattern)
            try? dataSource.setPreferredPolarPattern(pattern)
            logger.info("setPreferredPolarPattern ok — \(polarPattern)")
        } else {
            // Clear any prior .stereo selection so mono capture returns to a mono capsule.
            try? dataSource.setPreferredPolarPattern(nil)
        }
    }

    /// Reset any built-in-mic data source that's currently on the `.stereo` polar pattern back to
    /// the default (mono) pattern. Used when switching from a stereo session back to mono with no
    /// explicit capsule selection, so the prior stereo capsule doesn't linger.
    private func clearStereoPolarPattern(session: AVAudioSession) {
        guard let builtIn = session.availableInputs?.first(where: { $0.portType == .builtInMic })
        else { return }
        for ds in builtIn.dataSources ?? [] where ds.selectedPolarPattern == .stereo {
            try? ds.setPreferredPolarPattern(nil)
        }
    }

    private func modeLabel(_ mode: AVAudioSession.Mode) -> String {
        switch mode {
        case .voiceChat: return "voiceChat"
        case .measurement: return "measurement"
        case .videoRecording: return "videoRecording"
        case .default: return "default"
        default: return "other"
        }
    }

    private func optionsLabel(_ opts: AVAudioSession.CategoryOptions) -> String {
        var parts: [String] = []
        if opts.contains(.defaultToSpeaker) { parts.append("defaultToSpeaker") }
        if opts.contains(.mixWithOthers) { parts.append("mixWithOthers") }
        if opts.contains(.allowBluetoothHFP) { parts.append("allowBluetoothHFP") }
        if opts.contains(.allowBluetoothA2DP) { parts.append("allowBluetoothA2DP") }
        return parts.joined(separator: ",")
    }

    /// Apply stored preferences from UserDefaults. Called at app launch (before any
    /// audio session activation).
    func loadStoredPreferences() {
        if let raw = UserDefaults.standard.string(forKey: kBluetoothMode),
           let mode = BluetoothMode(rawValue: raw) {
            bluetoothMode = mode
        }
        if let raw = UserDefaults.standard.string(forKey: kMicMode),
           let mode = MicMode(rawValue: raw) {
            micMode = mode
        }
        if let raw = UserDefaults.standard.string(forKey: kCaptureChannels),
           let ch = CaptureChannels(rawValue: raw) {
            captureChannels = ch
        }
        selectedInputPortId = UserDefaults.standard.string(forKey: kInputPortId)
        selectedDataSourceId = UserDefaults.standard.string(forKey: kDataSourceId)
        selectedPolarPattern = UserDefaults.standard.string(forKey: kPolarPattern)
    }
    /// Persist current selections to UserDefaults.
    func savePreferences() {
        UserDefaults.standard.set(bluetoothMode.rawValue, forKey: kBluetoothMode)
        UserDefaults.standard.set(micMode.rawValue, forKey: kMicMode)
        UserDefaults.standard.set(captureChannels.rawValue, forKey: kCaptureChannels)
        UserDefaults.standard.set(selectedInputPortId, forKey: kInputPortId)
        UserDefaults.standard.set(selectedDataSourceId, forKey: kDataSourceId)
        UserDefaults.standard.set(selectedPolarPattern, forKey: kPolarPattern)
    }

    // MARK: - Selection setters (called from SettingsView pickers)

    func selectInputPort(_ portId: String) {
        selectedInputPortId = portId
        selectedDataSourceId = nil
        selectedPolarPattern = nil
        savePreferences()
        applyConfiguration()
        refreshRoutes()
    }

    func selectDataSource(_ dataSourceId: String) {
        selectedDataSourceId = dataSourceId
        selectedPolarPattern = nil
        savePreferences()
        applyConfiguration()
        refreshRoutes()
    }

    func selectPolarPattern(_ pattern: String) {
        selectedPolarPattern = pattern
        savePreferences()
        applyConfiguration()
        refreshRoutes()
    }

    func selectBluetoothMode(_ mode: BluetoothMode) {
        bluetoothMode = mode
        savePreferences()
        applyConfiguration()
        refreshRoutes()
    }

    func selectMicMode(_ mode: MicMode) {
        micMode = mode
        savePreferences()
        applyConfiguration()
        updateWarnings()
    }

    func selectCaptureChannels(_ channels: CaptureChannels) {
        captureChannels = channels
        savePreferences()
        applyConfiguration()
        // Update the core's stored capture channel count (does not restart the engine).
        if let streamId = AudioSessionManager.shared.activeMicStreamId {
            _ = AudioSessionManager.shared.client?.setCaptureChannels(
                streamId: streamId, channels: channels.channelCount)
        }
        // Restart the engine AFTER AVAudioSession routing has settled and the channel
        // count is stored. The engine reopens playback first (committing the A2DP/output
        // route), then capture — avoiding the race where stereo capture activation drops
        // A2DP before the playback device has a chance to claim the route.
        _ = AudioSessionManager.shared.client?.audioRestart()
    }

    // MARK: - Presets

    /// Apply a preset — sets all individual audio settings to the preset's values, then
    /// applies the configuration. For presets that use the built-in mic (A2DP presets),
    /// finds the built-in mic port UID from availableInputs.
    func applyPreset(_ preset: AudioPreset) {
        guard preset != .custom else { return }  // can't "apply" custom — it's a display state

        bluetoothMode = preset.bluetoothMode
        micMode = preset.micMode
        captureChannels = preset.captureChannels

        if preset.usesBuiltInMic {
            // Find the built-in mic port from available inputs and select it.
            let session = AVAudioSession.sharedInstance()
            if let builtInMic = (session.availableInputs ?? []).first(where: {
                $0.portType == .builtInMic
            }) {
                selectedInputPortId = builtInMic.uid
            }
            // Don't set a specific data source — in stereo mode, iOS uses multiple mic
            // capsules automatically. In mono, the default orientation is fine.
            selectedDataSourceId = nil
            selectedPolarPattern = nil
        } else {
            // For Default and Bluetooth Headset presets, let the system pick the input.
            selectedInputPortId = nil
            selectedDataSourceId = nil
            selectedPolarPattern = nil
        }

        UserDefaults.standard.set(preset.rawValue, forKey: kPreset)
        savePreferences()
        applyConfiguration()
        // Update the core's stored capture channel count (does not restart the engine).
        if let streamId = AudioSessionManager.shared.activeMicStreamId {
            _ = AudioSessionManager.shared.client?.setCaptureChannels(
                streamId: streamId, channels: preset.captureChannels.channelCount)
        }
        // Restart the engine AFTER AVAudioSession routing has settled and the channel
        // count is stored. Playback opens first (commits A2DP route), then capture.
        _ = AudioSessionManager.shared.client?.audioRestart()
        refreshRoutes()
        logger.info("applyPreset — \(preset.rawValue)")
    }

    // MARK: - Helpers

    /// Update warning indicators for the Settings UI.
    private func updateWarnings() {
        let session = AVAudioSession.sharedInstance()
        let outputIsSpeaker = session.currentRoute.outputs.contains { $0.portType == .builtInSpeaker }
        // Raw/Studio mode + speaker = echo risk (no AEC in .measurement mode)
        showsRawModeSpeakerWarning = (micMode == .raw && outputIsSpeaker)
        // A2DP output runs without hardware AEC (the .voiceChat AEC path isn't available on an
        // A2DP route). Applies to both mono and stereo A2DP. Stereo also has no AEC (it can't
        // use .voiceChat at all), but the message is the same and the warning already shows when
        // the bluetooth mode is A2DP.
        showsA2dpNoAecWarning = (bluetoothMode == .builtInMicBtA2dp)
    }

    /// Whether the current configuration wants Bluetooth A2DP output. Used after session
    /// activation to clear any lingering speaker override that would pin output to the speaker.
    var wantsA2dpOutput: Bool { bluetoothMode == .builtInMicBtA2dp }

    /// The selected input port object, if any.
    var selectedPort: IOSAudioInputPort? {
        inputPorts.first(where: { $0.id == selectedInputPortId })
    }

    /// The data sources of the selected input port, if it's the built-in mic.
    var selectedPortDataSources: [IOSAudioDataSource]? {
        selectedPort?.dataSources
    }

    /// Whether the selected input port is the built-in mic (has data sources / orientation).
    var selectedPortIsBuiltInMic: Bool {
        selectedPort?.portType == AVAudioSession.Port.builtInMic.rawValue
    }
}