Musubi/App/Sources/IntercomController.swift

import AudioMatrix
import Foundation
import Intercom
import MusubiCore
import NDIKit
import Observation

/// App-side glue for the intercom (control only): server on the clinic interface,
/// PGM preview from an NDI proxy stream, talkback from the headset mic gated by the talk key.
@MainActor @Observable
final class IntercomController {
    let server = IntercomServer()

    /// NDI source shown on the phones (usually PGM).
    var previewSourceName: String {
        didSet {
            UserDefaults.standard.set(previewSourceName, forKey: "intercomPreviewSource")
            startPreview()
        }
    }

    /// Input device whose signal the phones hear while the talk key is down.
    var talkbackDeviceUID: String {
        didSet {
            UserDefaults.standard.set(talkbackDeviceUID, forKey: "talkbackDeviceUID")
            startTalkback()
        }
    }

    private let settings: AppSettings
    private let audio: AudioController
    private var preview: NDIReceiver?
    private var tap: (feed: AudioFeed, deviceUID: String)?
    private var pump: TalkbackPump?

    init(settings: AppSettings, audio: AudioController) {
        self.settings = settings
        self.audio = audio
        previewSourceName = UserDefaults.standard.string(forKey: "intercomPreviewSource") ?? ""
        talkbackDeviceUID = UserDefaults.standard.string(forKey: "talkbackDeviceUID") ?? ""
    }

    var isEnabled: Bool { settings.role == .control && !settings.clinicInterfaceName.isEmpty }

    /// Technical and clinic network on the same interface is fine at home, never on site.
    var sharesTechnicalInterface: Bool { settings.clinicInterfaceName == settings.interfaceName }

    /// (Re)starts or stops everything according to role and clinic interface; call after settings changes.
    func restart() async {
        stopAll()
        guard isEnabled else { return }
        await server.start(interfaceName: settings.clinicInterfaceName)
        startPreview()
        startTalkback()
    }

    func setTalkActive(_ active: Bool) {
        pump?.gateOpen = active
    }

    private func stopAll() {
        server.stop()
        preview?.stop()
        preview = nil
        stopTalkback()
    }

    private func startPreview() {
        preview?.stop()
        preview = nil
        guard isEnabled, !previewSourceName.isEmpty else { return }
        let input = server.input
        preview = NDIReceiver(source: Source(ndiName: previewSourceName), receiverName: "Musubi Intercom",
                              bandwidth: .lowest, onFrame: { input.pushVideo($0) })
        Log.intercom.info("Preview from \(self.previewSourceName, privacy: .public)")
    }

    private func startTalkback() {
        stopTalkback()
        guard isEnabled else { return }
        let uid = talkbackDeviceUID.isEmpty ? defaultTalkbackDevice() : talkbackDeviceUID
        guard let uid, audio.matrix.inputDevices.contains(where: { $0.uid == uid }) else { return }
        let feed = audio.matrix.addInputTap(deviceUID: uid)
        tap = (feed, uid)
        let pump = TalkbackPump(feed: feed, input: server.input)
        pump.gateOpen = audio.talkKey.isActive
        pump.start()
        self.pump = pump
    }

    private func stopTalkback() {
        pump?.stop()
        pump = nil
        if let tap { audio.matrix.removeInputTap(tap.feed, deviceUID: tap.deviceUID) }
        tap = nil
    }

    /// The mic already routed in the sound matrix, else the system's default input.
    func defaultTalkbackDevice() -> String? {
        for route in audio.matrix.routes {
            if case .input(let uid) = route.source { return uid }
        }
        return AudioDevices.defaultInput()?.uid ?? audio.matrix.inputDevices.first?.uid
    }

    /// Name of the device "Automatisch" currently resolves to.
    var automaticTalkbackName: String? {
        defaultTalkbackDevice().flatMap { uid in audio.matrix.inputDevices.first { $0.uid == uid }?.name }
    }
}

/// Moves mic audio from the tap to the Opus encoder every 10 ms on its own queue.
/// Sends silence while the talk key is up, so the phones' audio clock keeps running.
private final class TalkbackPump: @unchecked Sendable {
    private let feed: AudioFeed
    private let input: IntercomInput
    private let queue = DispatchQueue(label: "studio.zielke.musubi.intercom.talkback", qos: .userInitiated)
    private var timer: DispatchSourceTimer?
    private let lock = NSLock()
    private var open = false
    private var stereo = [Float](repeating: 0, count: 4096 * 2)
    private var mono = [Float](repeating: 0, count: 4096)

    init(feed: AudioFeed, input: IntercomInput) {
        self.feed = feed
        self.input = input
    }

    var gateOpen: Bool {
        get { lock.withLock { open } }
        set { lock.withLock { open = newValue } }
    }

    func start() {
        let timer = DispatchSource.makeTimerSource(queue: queue)
        timer.schedule(deadline: .now(), repeating: .milliseconds(10), leeway: .milliseconds(2))
        timer.setEventHandler { [weak self] in self?.drain() }
        timer.resume()
        self.timer = timer
    }

    func stop() {
        timer?.cancel()
        timer = nil
    }

    private func drain() {
        let rate = feed.currentSampleRate
        let frames = stereo.withUnsafeMutableBufferPointer { feed.read(into: $0.baseAddress!, frames: 4096) }
        guard frames > 0, rate > 0 else { return }
        let open = gateOpen
        for i in 0..<frames { mono[i] = open ? stereo[i * 2] : 0 }
        mono.withUnsafeBufferPointer { input.pushTalkback(UnsafeBufferPointer(rebasing: $0[0..<frames]), sampleRate: rate) }
    }
}