// periph.swift — Neuron's PERIPHERAL I/O organ (own-core, LOCAL, CONSENT-GATED).
//
// The interface made physical:
//   MIC    (hear)  = afferent  : device -> capture -> [ingest -> geometry]
//   CAMERA (see)   = afferent  : device -> capture -> [ingest -> scene-geometry]
//   SPEAKER(speak) = efferent  : [render WAV] -> PLAY ALOUD out the speaker
//
// Rails: own-core (AVFoundation / CoreAudio / afplay — all ship with macOS),
//        no cloud, no heavy deps, raw streams stay LOCAL and never egress,
//        every device access is CONSENT-GATED and DISCLOSED.
//
// Full-duplex CONVERSE mode implements native interruptibility: while the
// speaker plays the utterance (a persistent, segmented meaning-plan), the mic
// listens; on user speech it interrupts instantly, then DECIDES yield-or-hold
// grounded in the salience of what it is mid-saying, and can RESUME the thread.
//
// Build:  swiftc -O -o peripheral/bin/periph peripheral/src/periph.swift \
//               -framework AVFoundation -framework CoreMedia -framework Foundation

import Foundation
import AVFoundation
import CoreMedia
import CoreGraphics
import ImageIO
import CoreImage

// ----------------------------------------------------------------------------
// Disclosure — every peripheral touch is announced on stderr. Nothing is silent.
// ----------------------------------------------------------------------------
func disclose(_ msg: String) {
    FileHandle.standardError.write("  [peripheral] \(msg)\n".data(using: .utf8)!)
}
func emit(_ obj: [String: Any]) {  // machine-readable event on stdout (JSON line)
    if let d = try? JSONSerialization.data(withJSONObject: obj),
       let s = String(data: d, encoding: .utf8) {
        print(s)
    }
}
func die(_ msg: String) -> Never {
    disclose("ERROR: \(msg)")
    emit(["ok": false, "error": msg])
    exit(1)
}

// ----------------------------------------------------------------------------
// Consent store — Neuron's OWN gate, on top of the OS (TCC) gate. Two locks on
// the sensitive senses. Persisted locally next to the binary's organ dir.
// ----------------------------------------------------------------------------
struct Consent {
    static let path: String = {
        let dir = ProcessInfo.processInfo.environment["PERIPH_HOME"]
            ?? FileManager.default.currentDirectoryPath + "/peripheral"
        return dir + "/.consent.json"
    }()

    static func load() -> [String: Bool] {
        guard let d = FileManager.default.contents(atPath: path),
              let o = try? JSONSerialization.jsonObject(with: d) as? [String: Bool]
        else { return ["camera": false, "mic": false] }
        return o
    }
    static func save(_ g: [String: Bool]) {
        let d = try! JSONSerialization.data(withJSONObject: g, options: [.prettyPrinted])
        try? d.write(to: URL(fileURLWithPath: path))
    }
    // Neuron-level gate. Sensitive senses (camera/mic) require an explicit grant.
    static func require(_ device: String) {
        let g = load()
        if g[device] != true {
            die("CONSENT DENIED for '\(device)'. The user has not granted this sense. " +
                "Run:  periph grant \(device)   (raw streams stay local, never egress).")
        }
        disclose("consent OK (Neuron-level) for '\(device)' — local only, never egresses.")
    }
}

// ----------------------------------------------------------------------------
// OS (TCC) permission — the second lock. AVFoundation prompts the user the first
// time; if denied, we fail cleanly rather than hang.
// ----------------------------------------------------------------------------
func requireOSAccess(_ media: AVMediaType, _ label: String) {
    let status = AVCaptureDevice.authorizationStatus(for: media)
    switch status {
    case .authorized:
        disclose("consent OK (OS/TCC) for \(label).")
        return
    case .notDetermined:
        disclose("requesting OS permission for \(label) (first use) — user must grant...")
        let sem = DispatchSemaphore(value: 0)
        var ok = false
        AVCaptureDevice.requestAccess(for: media) { granted in ok = granted; sem.signal() }
        _ = sem.wait(timeout: .now() + 30)
        if !ok { die("OS permission for \(label) was not granted.") }
        disclose("consent OK (OS/TCC) for \(label).")
    case .denied, .restricted:
        die("OS permission for \(label) is DENIED in System Settings > Privacy. " +
            "Grant it to the controlling terminal/app, then retry.")
    @unknown default:
        die("unknown OS permission state for \(label).")
    }
}

// ----------------------------------------------------------------------------
// Own-core WAV writer (16-bit PCM). No library — proves we own the medium.
// ----------------------------------------------------------------------------
func writeWav(_ url: URL, samples: [Int16], sampleRate: Int, channels: Int = 1) {
    var data = Data()
    func u32(_ v: UInt32) { var x = v.littleEndian; data.append(Data(bytes: &x, count: 4)) }
    func u16(_ v: UInt16) { var x = v.littleEndian; data.append(Data(bytes: &x, count: 2)) }
    let bytesPerSample = 2
    let dataBytes = samples.count * bytesPerSample
    let byteRate = sampleRate * channels * bytesPerSample
    data.append("RIFF".data(using: .ascii)!); u32(UInt32(36 + dataBytes))
    data.append("WAVE".data(using: .ascii)!)
    data.append("fmt ".data(using: .ascii)!); u32(16); u16(1); u16(UInt16(channels))
    u32(UInt32(sampleRate)); u32(UInt32(byteRate))
    u16(UInt16(channels * bytesPerSample)); u16(16)
    data.append("data".data(using: .ascii)!); u32(UInt32(dataBytes))
    for s in samples { var x = s.littleEndian; data.append(Data(bytes: &x, count: 2)) }
    try? data.write(to: url)
}

// Read a WAV's basic geometry (own-core header parse). Walks chunks to find
// 'fmt ' and 'data' — robust to JUNK/FLLR padding chunks (AVAudioRecorder emits them).
func wavInfo(_ path: String) -> (sampleRate: Int, channels: Int, bits: Int, frames: Int)? {
    guard let d = FileManager.default.contents(atPath: path), d.count > 44 else { return nil }
    func rd16(_ o: Int) -> Int { Int(d[o]) | (Int(d[o+1]) << 8) }
    func rd32(_ o: Int) -> Int { Int(d[o]) | (Int(d[o+1])<<8) | (Int(d[o+2])<<16) | (Int(d[o+3])<<24) }
    var channels = 0, sampleRate = 0, bits = 0, dataSize = 0
    var o = 12
    while o + 8 <= d.count {
        let id = String(bytes: d[o..<o+4], encoding: .ascii) ?? ""
        let sz = rd32(o+4)
        if id == "fmt " && o + 24 <= d.count {
            channels = rd16(o+10); sampleRate = rd32(o+12); bits = rd16(o+22)
        } else if id == "data" {
            dataSize = min(sz, d.count - (o+8))
        }
        o += 8 + sz + (sz & 1)
    }
    let frames = (channels > 0 && bits > 0) ? dataSize / (channels * bits/8) : 0
    return (sampleRate, channels, bits, frames)
}

// ----------------------------------------------------------------------------
// SPEAKER (efferent) — play a WAV ALOUD. Own-core: afplay ships with macOS.
// ----------------------------------------------------------------------------
func speak(_ wavPath: String) {
    guard FileManager.default.fileExists(atPath: wavPath) else { die("no such file: \(wavPath)") }
    disclose("SPEAKER: playing '\(wavPath)' ALOUD out the local speaker (efferent).")
    let p = Process()
    p.executableURL = URL(fileURLWithPath: "/usr/bin/afplay")
    p.arguments = [wavPath]
    try? p.run(); p.waitUntilExit()
    let ok = p.terminationStatus == 0
    disclose(ok ? "SPEAKER: done — Neuron spoke aloud." : "SPEAKER: afplay failed.")
    if let i = wavInfo(wavPath) {
        emit(["ok": ok, "op": "speak", "file": wavPath, "played_aloud": ok,
              "sample_rate": i.sampleRate, "channels": i.channels,
              "seconds": Double(i.frames)/Double(max(i.sampleRate,1))])
    } else {
        emit(["ok": ok, "op": "speak", "file": wavPath, "played_aloud": ok])
    }
}

// ----------------------------------------------------------------------------
// MIC (afferent) — capture N seconds -> 16k mono 16-bit WAV (formant-ready).
// ----------------------------------------------------------------------------
func listen(seconds: Double, out: String) {
    Consent.require("mic")
    requireOSAccess(.audio, "microphone")
    disclose("MIC: capturing \(seconds)s -> '\(out)' (16 kHz mono, LOCAL, never egresses).")

    let url = URL(fileURLWithPath: out)
    let settings: [String: Any] = [
        AVFormatIDKey: kAudioFormatLinearPCM,
        AVSampleRateKey: 16000.0,
        AVNumberOfChannelsKey: 1,
        AVLinearPCMBitDepthKey: 16,
        AVLinearPCMIsFloatKey: false,
        AVLinearPCMIsBigEndianKey: false,
    ]
    guard let rec = try? AVAudioRecorder(url: url, settings: settings) else {
        die("could not open the microphone recorder.")
    }
    rec.record()
    Thread.sleep(forTimeInterval: seconds)
    rec.stop()
    // let the file flush
    Thread.sleep(forTimeInterval: 0.1)
    if let i = wavInfo(out) {
        disclose("MIC: captured \(i.frames) frames @ \(i.sampleRate)Hz — ready to hand to the ingest organ.")
        emit(["ok": true, "op": "listen", "file": out, "sample_rate": i.sampleRate,
              "channels": i.channels, "frames": i.frames,
              "seconds": Double(i.frames)/Double(max(i.sampleRate,1)),
              "next": "ingest -> phonetic/voice geometry"])
    } else {
        die("mic capture produced no readable WAV.")
    }
}

// ----------------------------------------------------------------------------
// CAMERA (afferent) — capture ONE frame -> JPEG on disk.
// ----------------------------------------------------------------------------
// Grab one video frame via AVCaptureVideoDataOutput (CLI-safe; no KVO/photo classes).
final class FrameGrabber: NSObject, AVCaptureVideoDataOutputSampleBufferDelegate {
    let sem = DispatchSemaphore(value: 0)
    var cgImage: CGImage?
    var seen = 0
    let cictx = CIContext(options: nil)
    func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer,
                       from connection: AVCaptureConnection) {
        seen += 1
        if cgImage != nil || seen < 5 { return }        // let exposure settle a few frames
        guard let pb = CMSampleBufferGetImageBuffer(sampleBuffer) else { return }
        let ci = CIImage(cvPixelBuffer: pb)
        cgImage = cictx.createCGImage(ci, from: ci.extent)
        sem.signal()
    }
}
func see(out: String) {
    Consent.require("camera")
    requireOSAccess(.video, "camera")
    disclose("CAMERA: capturing one frame -> '\(out)' (LOCAL, never egresses).")

    let session = AVCaptureSession()
    session.sessionPreset = .photo
    guard let device = AVCaptureDevice.default(for: .video),
          let input = try? AVCaptureDeviceInput(device: device),
          session.canAddInput(input) else { die("no camera device available.") }
    session.addInput(input)
    let output = AVCaptureVideoDataOutput()
    output.alwaysDiscardsLateVideoFrames = true
    let grabber = FrameGrabber()
    output.setSampleBufferDelegate(grabber, queue: DispatchQueue(label: "periph.cam"))
    guard session.canAddOutput(output) else { die("cannot add video output.") }
    session.addOutput(output)
    session.startRunning()

    if grabber.sem.wait(timeout: .now() + 10) == .timedOut { session.stopRunning(); die("camera capture timed out.") }
    session.stopRunning()

    guard let cg = grabber.cgImage,
          let dst = CGImageDestinationCreateWithURL(URL(fileURLWithPath: out) as CFURL,
                                                    "public.jpeg" as CFString, 1, nil)
    else { die("camera returned no frame.") }
    CGImageDestinationAddImage(dst, cg, nil)
    guard CGImageDestinationFinalize(dst) else { die("could not write JPEG.") }
    let bytes = ((try? FileManager.default.attributesOfItem(atPath: out))?[.size] as? Int) ?? 0
    disclose("CAMERA: wrote \(cg.width)x\(cg.height) frame (\(bytes) bytes) — ready for scene-geometry ingest.")
    emit(["ok": true, "op": "see", "file": out, "width": cg.width, "height": cg.height,
          "bytes": bytes, "next": "ingest -> scene-geometry"])
}

// ============================================================================
// FEAT — the afferent METABOLISM: a raw capture becomes a COMPACT descriptor
// (a few dozen numbers), the mirror of the efferent signature. This is what
// gets handed to the ingest organ as geometry — NOT the raw stream. Own-core.
// ============================================================================

// Read all 16-bit PCM samples from a WAV (own-core).
func readWavSamples(_ path: String) -> (samples: [Double], sr: Int, ch: Int)? {
    guard let d = FileManager.default.contents(atPath: path), d.count > 44 else { return nil }
    func rd16(_ o: Int) -> Int { Int(d[o]) | (Int(d[o+1]) << 8) }
    func rd32(_ o: Int) -> Int { Int(d[o]) | (Int(d[o+1])<<8) | (Int(d[o+2])<<16) | (Int(d[o+3])<<24) }
    var ch = 0, sr = 0, bits = 0
    var o = 12
    while o + 8 <= d.count {
        let id = String(bytes: d[o..<o+4], encoding: .ascii) ?? ""
        let sz = rd32(o+4)
        if id == "fmt " && o + 24 <= d.count { ch = rd16(o+10); sr = rd32(o+12); bits = rd16(o+22) }
        if id == "data" {
            guard bits == 16, ch > 0 else { return nil }
            var samples = [Double](); let start = o + 8
            let end = min(start + sz, d.count - 1)
            var i = start
            while i + 1 < end {
                var v = Int(rd16(i)); if v >= 32768 { v -= 65536 }
                samples.append(Double(v) / 32768.0)
                i += 2 * ch                       // take channel 0 if stereo
            }
            return (samples, sr, ch)
        }
        o += 8 + sz + (sz & 1)
    }
    return nil
}

// Audio descriptor = compact sound/voice signature (energy, ZCR, centroid, F0).
// The seed for phonetic geometry + the hear->imitate voice-signature.
func computeAudio(_ path: String) -> (content: String, vector: [Double], extra: [String: Any]) {
    guard let (s, sr, ch) = readWavSamples(path), !s.isEmpty else { die("cannot read PCM from \(path)") }
    let n = s.count
    let seconds = Double(n) / Double(sr)
    var sumsq = 0.0, peak = 0.0, zc = 0.0
    for i in 0..<n {
        sumsq += s[i]*s[i]; peak = max(peak, abs(s[i]))
        if i > 0 && (s[i-1] < 0) != (s[i] < 0) { zc += 1 }
    }
    let rms = (sumsq / Double(n)).squareRoot()
    let zcr = zc / Double(n) * Double(sr)          // ~2*dominant freq for tonal
    // Spectral centroid via a coarse DFT on a mid window (own-core).
    let W = min(2048, n); let off = max(0, (n - W)/2)
    var num = 0.0, den = 0.0
    let bins = 64
    for k in 1..<bins {
        let f = Double(k) * Double(sr) / Double(2*bins)
        var re = 0.0, im = 0.0
        for j in 0..<W {
            let ang = -2*Double.pi*Double(k)*Double(j)/Double(2*bins)
            re += s[off+j]*cos(ang); im += s[off+j]*sin(ang)
        }
        let mag = (re*re+im*im).squareRoot()
        num += f*mag; den += mag
    }
    let centroid = den > 0 ? num/den : 0
    // F0 via autocorrelation (voice pitch) over plausible speech range 70-400 Hz.
    var bestLag = 0; var bestCorr = 0.0
    let lagMin = sr/400, lagMax = min(sr/70, n-1)
    if lagMax > lagMin {
        for lag in lagMin...lagMax {
            var c = 0.0
            var i = 0; while i + lag < min(n, off+W) { c += s[off+i]*s[off+i+lag]; i += 1 }
            if c > bestCorr { bestCorr = c; bestLag = lag }
        }
    }
    let f0 = bestLag > 0 ? Double(sr)/Double(bestLag) : 0
    let vector: [Double] = [seconds, Double(sr), Double(ch), rms, peak, zcr, centroid, f0]
    let content = String(format:
        "Heard sound (afferent, mic): %.2fs at %dHz. RMS energy %.3f, peak %.3f, " +
        "zero-crossing rate %.0fHz, spectral centroid %.0fHz, estimated voice pitch F0 %.0fHz. " +
        "Compact voice/sound signature (%d numbers) — phonetic geometry + hear-to-imitate seed.",
        seconds, sr, rms, peak, zcr, centroid, f0, vector.count)
    disclose("FEAT(audio): \(vector.count)-number signature vs \(n) raw samples (~\(n/max(vector.count,1))x compression).")
    return (content, vector, ["f0_hz": f0, "centroid_hz": centroid, "zcr_hz": zcr,
                             "rms": rms, "seconds": seconds, "raw_samples": n])
}
func featAudio(_ path: String) {
    let r = computeAudio(path)
    var out: [String: Any] = ["ok": true, "op": "feat-audio", "file": path,
                              "vector": r.vector, "content": r.content,
                              "ingest": ["node_type": "Observation", "tier": "Episodic", "content": r.content]]
    r.extra.forEach { out[$0] = $1 }
    emit(out)
}

// Image descriptor = compact scene-geometry (dims, brightness, region grid).
func computeImage(_ path: String) -> (content: String, vector: [Double], extra: [String: Any]) {
    guard let src = CGImageSourceCreateWithURL(URL(fileURLWithPath: path) as CFURL, nil),
          let img = CGImageSourceCreateImageAtIndex(src, 0, nil) else { die("cannot decode image \(path)") }
    let w = img.width, h = img.height
    let cs = CGColorSpaceCreateDeviceRGB()
    let bpr = w * 4
    var buf = [UInt8](repeating: 0, count: h * bpr)
    guard let ctx = CGContext(data: &buf, width: w, height: h, bitsPerComponent: 8,
                              bytesPerRow: bpr, space: cs,
                              bitmapInfo: CGImageAlphaInfo.premultipliedLast.rawValue) else {
        die("cannot rasterize image")
    }
    ctx.draw(img, in: CGRect(x: 0, y: 0, width: w, height: h))
    // 3x3 region average luminance + overall average color.
    var rAvg = 0.0, gAvg = 0.0, bAvg = 0.0
    var grid = [Double](repeating: 0, count: 9); var gridN = [Int](repeating: 0, count: 9)
    let step = max(1, (w*h)/40000)             // subsample for speed
    var count = 0; var idx = 0
    while idx < w*h {
        let x = idx % w, y = idx / w
        let p = y*bpr + x*4
        let r = Double(buf[p]), g = Double(buf[p+1]), b = Double(buf[p+2])
        rAvg += r; gAvg += g; bAvg += b; count += 1
        let cell = (min(2, y*3/h))*3 + min(2, x*3/w)
        grid[cell] += 0.299*r + 0.587*g + 0.114*b; gridN[cell] += 1
        idx += step
    }
    if count == 0 { die("no pixels sampled") }
    rAvg /= Double(count); gAvg /= Double(count); bAvg /= Double(count)
    for i in 0..<9 { grid[i] = gridN[i] > 0 ? grid[i]/Double(gridN[i]) : 0 }
    let bright = (0.299*rAvg + 0.587*gAvg + 0.114*bAvg)/255.0
    let vector = [Double(w), Double(h), rAvg/255, gAvg/255, bAvg/255, bright] + grid.map { $0/255 }
    let content = String(format:
        "Saw scene (afferent, camera): %dx%d frame. Mean color rgb(%.0f,%.0f,%.0f), " +
        "brightness %.2f. 3x3 luminance grid [%.0f %.0f %.0f / %.0f %.0f %.0f / %.0f %.0f %.0f]. " +
        "Compact scene-geometry (%d numbers) vs %d pixel-channels.",
        w, h, rAvg, gAvg, bAvg, bright,
        grid[0],grid[1],grid[2],grid[3],grid[4],grid[5],grid[6],grid[7],grid[8],
        vector.count, w*h*3)
    disclose("FEAT(image): \(vector.count)-number scene-geometry vs \(w*h*3) pixel-channels (~\(w*h*3/max(vector.count,1))x).")
    return (content, vector, ["width": w, "height": h, "brightness": bright])
}
func featImage(_ path: String) {
    let r = computeImage(path)
    var out: [String: Any] = ["ok": true, "op": "feat-image", "file": path,
                              "vector": r.vector, "content": r.content,
                              "ingest": ["node_type": "Observation", "tier": "Episodic", "content": r.content]]
    r.extra.forEach { out[$0] = $1 }
    emit(out)
}

// The afferent WIRE — hand a capture's descriptor to the ingest organ (engram),
// where it becomes an embedded node = GEOMETRY. Own-core URLSession POST.
// LOCAL only: point at a local engram; raw stream never leaves the machine.
func postNode(engramURL: String, content: String, label: String, tags: [String]) -> String? {
    guard let url = URL(string: engramURL + "/api/nodes") else { return nil }
    let body: [String: Any] = ["content": content, "node_type": "Observation",
                               "label": label, "tier": "Episodic",
                               "salience": 0.7, "importance": 0.6, "confidence": 0.9,
                               "tags": tags]
    var req = URLRequest(url: url); req.httpMethod = "POST"
    req.setValue("application/json", forHTTPHeaderField: "Content-Type")
    req.httpBody = try? JSONSerialization.data(withJSONObject: body)
    let sem = DispatchSemaphore(value: 0); var out: String?
    URLSession.shared.dataTask(with: req) { data, _, _ in
        if let d = data { out = String(data: d, encoding: .utf8) }
        sem.signal()
    }.resume()
    _ = sem.wait(timeout: .now() + 15)
    return out
}
func ingest(_ path: String, kind: String, engramURL: String) {
    let r = kind == "audio" ? computeAudio(path) : computeImage(path)
    let label = kind == "audio" ? "heard:mic" : "saw:camera"
    disclose("INGEST: handing \(kind) descriptor to the ingest organ at \(engramURL) (LOCAL) -> geometry.")
    guard let resp = postNode(engramURL: engramURL, content: r.content, label: label,
                              tags: ["peripheral", kind == "audio" ? "afferent-mic" : "afferent-camera"]) else {
        die("ingest POST failed (no local engram at \(engramURL)?)")
    }
    // pull the node id out of the response (own-core, tolerant)
    var nodeId = ""
    if let d = resp.data(using: .utf8),
       let o = try? JSONSerialization.jsonObject(with: d) as? [String: Any] {
        nodeId = (o["id"] as? String) ?? (o["node_id"] as? String) ?? ""
    }
    disclose("INGEST: landed as node \(nodeId.isEmpty ? "(see response)" : nodeId) — the capture is now geometry in the engram.")
    emit(["ok": !nodeId.isEmpty, "op": "ingest-\(kind)", "file": path,
          "node_id": nodeId, "engram_response": resp, "content": r.content,
          "vector": r.vector])
}

// ============================================================================
// VOICE BY IMITATION — hear a voice, grab its compact SIGNATURE (pitch +
// formants F1-F5 via LPC), and speak back in that voice by source-filter
// resynthesis. Own-core DSP (physics), no training, no stolen voice. The
// afferent twin of the music instrument-signature: a voice = a few dozen
// numbers, not a corpus.
// ============================================================================

func hamming(_ x: [Double]) -> [Double] {
    let n = x.count; if n < 2 { return x }
    return (0..<n).map { x[$0] * (0.54 - 0.46*cos(2*Double.pi*Double($0)/Double(n-1))) }
}
func autocorr(_ x: [Double], _ p: Int) -> [Double] {
    var r = [Double](repeating: 0, count: p+1)
    for lag in 0...p { var s = 0.0; var i = lag; while i < x.count { s += x[i]*x[i-lag]; i += 1 }; r[lag] = s }
    return r
}
// Levinson-Durbin -> LPC coeffs a[0..p] (A(z)=1+sum a[k]z^-k) and residual energy.
func levinson(_ r: [Double], _ p: Int) -> (a: [Double], err: Double) {
    var a = [Double](repeating: 0, count: p+1); a[0] = 1
    var err = r[0]
    if err <= 0 { return (a, 0) }
    for i in 1...p {
        var acc = r[i]
        if i > 1 { for j in 1..<i { acc += a[j]*r[i-j] } }
        let k = -acc/err
        var na = a; na[i] = k
        if i > 1 { for j in 1..<i { na[j] = a[j] + k*a[i-j] } }
        a = na; err *= (1 - k*k)
        if err <= 0 { break }
    }
    return (a, err)
}
// Formant peaks from the LPC all-pole spectral envelope.
func formants(_ a: [Double], sr: Int) -> [(f: Double, bw: Double)] {
    let p = a.count - 1
    let steps = 512
    var mag = [Double](repeating: 0, count: steps)
    for s in 0..<steps {
        let w = Double.pi * Double(s) / Double(steps)      // 0..pi -> 0..sr/2
        var re = 0.0, im = 0.0
        for k in 0...p { re += a[k]*cos(w*Double(k)); im -= a[k]*sin(w*Double(k)) }
        mag[s] = 1.0 / max((re*re+im*im).squareRoot(), 1e-9)
    }
    var peaks: [(f: Double, bw: Double)] = []
    for s in 1..<(steps-1) where mag[s] > mag[s-1] && mag[s] >= mag[s+1] {
        let f = Double(s) * Double(sr) / 2 / Double(steps)
        if f > 150 && f < 5200 {
            // crude bandwidth: width where magnitude falls to peak/sqrt(2)
            let thr = mag[s]/1.4142
            var lo = s; while lo > 0 && mag[lo] > thr { lo -= 1 }
            var hi = s; while hi < steps-1 && mag[hi] > thr { hi += 1 }
            let bw = Double(hi-lo) * Double(sr) / 2 / Double(steps)
            peaks.append((f, bw))
        }
    }
    return Array(peaks.prefix(5))
}
func pitchOf(_ frame: [Double], sr: Int) -> Double {
    let n = frame.count
    let lagMin = sr/400, lagMax = min(sr/70, n-1)
    if lagMax <= lagMin { return 0 }
    var r0 = 0.0; for v in frame { r0 += v*v }
    if r0 < 1e-5 { return 0 }
    var bestLag = 0; var best = 0.0
    for lag in lagMin...lagMax { var c = 0.0; var i = lag; while i < n { c += frame[i]*frame[i-lag]; i += 1 }; if c > best { best = c; bestLag = lag } }
    return (best / r0 > 0.30 && bestLag > 0) ? Double(sr)/Double(bestLag) : 0   // voiced?
}

let LPC_ORDER = 16
let FRAME = 400          // 25ms @16k
let HOP = 160            // 10ms

// Extract Will's voice-signature: averaged F0 + formants over voiced frames.
func voiceprint(_ path: String) -> (f0: Double, f0lo: Double, f0hi: Double, formants: [(Double,Double)], content: String) {
    guard let (x, sr, _) = readWavSamples(path), x.count > FRAME else { die("cannot read speech from \(path)") }
    var f0s: [Double] = []
    var fbank: [[Double]] = [[],[],[],[],[]]
    var bbank: [[Double]] = [[],[],[],[],[]]
    var pos = 0
    while pos + FRAME <= x.count {
        let raw = Array(x[pos..<pos+FRAME])
        let f0 = pitchOf(raw, sr: sr)
        if f0 > 0 {                                   // voiced frame only
            f0s.append(f0)
            let r = autocorr(hamming(raw), LPC_ORDER)
            if r[0] > 1e-6 {
                let (a, _) = levinson(r, LPC_ORDER)
                let fs = formants(a, sr: sr)
                for (i, fm) in fs.enumerated() where i < 5 { fbank[i].append(fm.f); bbank[i].append(fm.bw) }
            }
        }
        pos += HOP
    }
    func med(_ v: [Double]) -> Double { v.isEmpty ? 0 : v.sorted()[v.count/2] }
    let f0med = med(f0s)
    let f0lo = f0s.isEmpty ? 0 : f0s.sorted().first!
    let f0hi = f0s.isEmpty ? 0 : f0s.sorted().last!
    var forms: [(Double,Double)] = []
    for i in 0..<5 where !fbank[i].isEmpty { forms.append((med(fbank[i]), med(bbank[i]))) }
    let fstr = forms.map { String(format:"%.0f", $0.0) }.joined(separator: "/")
    let content = String(format:
        "Voice-signature (afferent, heard a voice): pitch F0 %.0fHz (range %.0f-%.0fHz), " +
        "formants F1-F5 = %@ Hz. Compact voiceprint (%d numbers) — grabbed by ear for imitation, not trained.",
        f0med, f0lo, f0hi, fstr, 1 + forms.count*2)
    return (f0med, f0lo, f0hi, forms, content)
}

// IMITATE: LPC analysis-resynthesis. Reconstruct the heard voice from its
// per-frame filter model + pitch — the voice rebuilt from its signature.
func imitate(inPath: String, outPath: String) {
    guard let (x, sr, _) = readWavSamples(inPath), x.count > FRAME else { die("cannot read speech from \(inPath)") }
    var out = [Double](repeating: 0, count: x.count)
    var state = [Double](repeating: 0, count: LPC_ORDER)   // past outputs
    var phase = 0.0
    var lastF0 = 0.0
    var pos = 0
    while pos + FRAME <= x.count {
        let raw = Array(x[pos..<pos+FRAME])
        let r = autocorr(hamming(raw), LPC_ORDER)
        let f0 = pitchOf(raw, sr: sr)
        if r[0] < 1e-7 { pos += HOP; continue }
        let (a, err) = levinson(r, LPC_ORDER)
        let gain = max(err, 0).squareRoot()
        let useF0 = f0 > 0 ? f0 : (lastF0 > 0 ? lastF0 : 0)
        lastF0 = f0
        for i in 0..<HOP {
            let idx = pos + i; if idx >= x.count { break }
            var e = 0.0
            if useF0 > 0 {                              // voiced: glottal impulse train
                phase += useF0/Double(sr)
                if phase >= 1.0 { phase -= 1.0; e = sqrt(Double(sr)/useF0) }   // energy-normalized impulse
            } else {                                    // unvoiced: noise
                e = Double.random(in: -1...1)
            }
            var y = gain * e
            for k in 1...LPC_ORDER { y -= a[k]*state[k-1] }
            for k in stride(from: LPC_ORDER-1, through: 1, by: -1) { state[k] = state[k-1] }
            state[0] = y
            out[idx] = y
        }
        pos += HOP
    }
    // normalize to peak 0.9
    let peak = out.map { abs($0) }.max() ?? 1
    let scale = peak > 1e-9 ? 0.9/peak : 1
    let samples = out.map { Int16(max(-32767, min(32767, $0*scale*32767))) }
    writeWav(URL(fileURLWithPath: outPath), samples: samples, sampleRate: sr)
    let vp = voiceprint(inPath)
    disclose(String(format: "IMITATE: rebuilt the voice from its signature (F0 %.0fHz, formants %@) -> %@",
                    vp.f0, vp.formants.map{String(format:"%.0f",$0.0)}.joined(separator:"/"), outPath))
    emit(["ok": true, "op": "imitate", "in": inPath, "out": outPath,
          "f0_hz": vp.f0, "f0_range": [vp.f0lo, vp.f0hi],
          "formants_hz": vp.formants.map { $0.0 },
          "method": "LPC analysis-resynthesis (own-core, no training, no stolen voice)"])
}

// ============================================================================
// CONVERSE (full-duplex) — the interruptible conversational loop.
//   The utterance is a persistent, ordered meaning-plan of SEGMENTS, each with
//   a salience. The speaker plays them; the mic listens concurrently. On user
//   speech: pause INSTANTLY, classify (backchannel vs barge-in), then DECIDE
//   yield-or-hold from the salience of the current segment + the social read.
//   Yielded utterances persist their remaining plan so Neuron can RESUME.
// ============================================================================
struct Segment { let file: String; let salience: Double; let text: String }

enum Decision { case backchannelContinue, hold, yield }

// The yield-or-hold DECISION — grounded, contextual. Not a fixed rule.
func decide(currentSalience: Double, progress: Double,
            interrupterAuthority: Double, isBackchannel: Bool) -> Decision {
    if isBackchannel { return .backchannelContinue }          // "mm-hm" => keep going
    // Holding the floor is justified when what I'm saying matters AND I'm nearly
    // done (cheap to finish) AND the interrupter isn't high-priority.
    let holdScore = currentSalience * 0.6 + progress * 0.4
    if holdScore >= 0.6 && interrupterAuthority < 0.8 { return .hold }
    return .yield                                              // default: be polite, let them in
}

final class Conversation {
    let engine = AVAudioEngine()
    let player = AVAudioPlayerNode()
    var micLive = false
    // VAD state (shared with the audio tap thread)
    let lock = NSLock()
    var micRMS: Float = 0
    var speechFrames = 0          // consecutive above-threshold frames
    var onsetHandled = false

    let resumePath: String
    init(resumePath: String) { self.resumePath = resumePath }

    // Try to bring the mic up as a live VAD. Returns false if unavailable/denied.
    func startMic() -> Bool {
        let status = AVCaptureDevice.authorizationStatus(for: .audio)
        if Consent.load()["mic"] != true || status != .authorized {
            disclose("CONVERSE: live mic not available (consent/OS) — using injected barge events for the proof.")
            return false
        }
        let input = engine.inputNode
        // Acoustic echo cancellation: the OS voice-processing unit subtracts our
        // own speaker output from the mic so Neuron does NOT hear itself and
        // barge in on its own voice. This is what makes real-room barge-in work.
        do { try input.setVoiceProcessingEnabled(true); disclose("CONVERSE: AEC on (echo-cancelled mic — won't self-interrupt).") }
        catch { disclose("CONVERSE: AEC unavailable (\(error)); raising VAD floor instead.") }
        let fmt = input.inputFormat(forBus: 0)
        if fmt.sampleRate == 0 { return false }
        input.installTap(onBus: 0, bufferSize: 1024, format: fmt) { [weak self] buf, _ in
            guard let self = self, let ch = buf.floatChannelData?[0] else { return }
            let n = Int(buf.frameLength)
            var sum: Float = 0
            for i in 0..<n { let v = ch[i]; sum += v*v }
            let rms = n > 0 ? (sum / Float(n)).squareRoot() : 0
            self.lock.lock(); self.micRMS = rms; self.lock.unlock()
        }
        micLive = true
        disclose("CONVERSE: full-duplex — mic listening WHILE speaking (barge-in armed).")
        return true
    }

    func run(_ segs: [Segment], interrupterAuthority: Double,
             injectBargeAt: Double?, injectKind: String, startIndex: Int, liveMic: Bool) {
        engine.attach(player)
        let firstFmt = (try? AVAudioFile(forReading: URL(fileURLWithPath: segs[startIndex].file)))?.processingFormat
            ?? AVAudioFormat(standardFormatWithSampleRate: 16000, channels: 1)!
        engine.connect(player, to: engine.mainMixerNode, format: firstFmt)
        if liveMic { _ = startMic() }
        else { disclose("CONVERSE: deterministic mode (live mic off) — barge events \(injectBargeAt != nil ? "injected" : "none").") }
        do { try engine.start() } catch { die("audio engine failed to start: \(error)") }
        player.play()

        let injectDeadline = injectBargeAt.map { Date().addingTimeInterval($0) }
        var injectedFired = false
        var idx = startIndex

        segmentLoop: while idx < segs.count {
            let seg = segs[idx]
            guard let f = try? AVAudioFile(forReading: URL(fileURLWithPath: seg.file)) else {
                disclose("CONVERSE: missing segment '\(seg.file)', skipping."); idx += 1; continue
            }
            let dur = Double(f.length) / f.processingFormat.sampleRate
            disclose(String(format: "CONVERSE: speaking segment %d/%d (salience %.2f) — \"%@\"",
                            idx+1, segs.count, seg.salience, seg.text))
            emit(["op": "converse", "event": "speaking", "segment": idx,
                  "salience": seg.salience, "text": seg.text])

            let done = DispatchSemaphore(value: 0)
            // .dataPlayedBack: completion fires only after the audio has actually
            // played OUT the DAC (not merely been consumed) — so the tail is never
            // clipped and playback always runs the FULL file length.
            player.scheduleFile(f, at: nil, completionCallbackType: .dataPlayedBack) { _ in done.signal() }
            player.play()

            // Monitor this segment: poll VAD / injected event until it finishes.
            let segStart = Date()
            while done.wait(timeout: .now() + 0.02) == .timedOut {
                let elapsed = Date().timeIntervalSince(segStart)
                let progress = min(elapsed / max(dur, 0.001), 1.0)

                // --- detect an onset (live mic OR injected) ---
                var onset = false
                if micLive {
                    lock.lock(); let rms = micRMS; lock.unlock()
                    if rms > 0.02 { speechFrames += 1 } else { speechFrames = 0 }
                    if speechFrames >= 3 && !onsetHandled { onset = true }   // ~60ms of voice
                }
                if let dl = injectDeadline, !injectedFired, Date() >= dl, !onsetHandled { onset = true; injectedFired = true }

                if onset {
                    onsetHandled = true
                    // (1) BARGE-IN: pause INSTANTLY, on the spot.
                    player.pause()
                    let tBarge = Date().timeIntervalSince(segStart)
                    disclose(String(format: "CONVERSE: << user speech at %.2fs into segment %d — PAUSED instantly >>", tBarge, idx+1))
                    emit(["op": "converse", "event": "barge_in", "segment": idx,
                          "at_seconds": tBarge, "progress": progress])

                    // (2) classify backchannel vs real barge-in
                    let isBackchannel = classifyBackchannel(injected: injectDeadline != nil,
                                                            kind: injectKind)
                    let d = decide(currentSalience: seg.salience, progress: progress,
                                   interrupterAuthority: interrupterAuthority,
                                   isBackchannel: isBackchannel)
                    switch d {
                    case .backchannelContinue:
                        disclose("CONVERSE: read as BACKCHANNEL (\"mm-hm\") — keep going, resume seamlessly.")
                        emit(["op": "converse", "event": "backchannel_continue", "segment": idx])
                        onsetHandled = false; speechFrames = 0
                        player.play()                                   // seamless resume
                    case .hold:
                        disclose("CONVERSE: HOLD the floor — \"hang on, let me finish this thought.\" (high salience, nearly done)")
                        emit(["op": "converse", "event": "hold_floor", "segment": idx,
                              "salience": seg.salience, "progress": progress])
                        onsetHandled = false; speechFrames = 0
                        player.play()                                   // finish the segment, THEN yield
                        // after this segment completes we yield the remainder
                        _ = done.wait(timeout: .now() + dur + 1.0)
                        persistResume(segs: segs, from: idx + 1, reason: "held-then-yield")
                        finish(); return
                    case .yield:
                        disclose("CONVERSE: YIELD — stop, let them in. Remembering where I was (resumable).")
                        player.stop()
                        persistResume(segs: segs, from: idx, reason: "yield")
                        emit(["op": "converse", "event": "yield", "interrupted_segment": idx,
                              "resume_from": idx])
                        finish(); return
                    }
                }
            }
            emit(["op": "converse", "event": "segment_done", "segment": idx])
            idx += 1
        }
        // whole utterance completed uninterrupted
        clearResume()
        disclose("CONVERSE: utterance complete (uninterrupted).")
        emit(["ok": true, "op": "converse", "event": "complete", "segments": segs.count])
        finish()
    }

    // A backchannel is brief/low. Injected kind lets us prove both paths headlessly;
    // the live path would measure post-onset duration & energy.
    func classifyBackchannel(injected: Bool, kind: String) -> Bool {
        if injected { return kind == "backchannel" }
        // live: sample ~250ms after onset; if speech already died away, it was a backchannel
        Thread.sleep(forTimeInterval: 0.25)
        lock.lock(); let rms = micRMS; lock.unlock()
        return rms < 0.015
    }

    func persistResume(segs: [Segment], from: Int, reason: String) {
        let remaining = segs[from...].map { ["file": $0.file, "salience": $0.salience, "text": $0.text] as [String: Any] }
        let state: [String: Any] = ["resume_from": from, "reason": reason,
                                    "remaining": remaining, "ts": Date().timeIntervalSince1970]
        if let d = try? JSONSerialization.data(withJSONObject: state, options: [.prettyPrinted]) {
            try? d.write(to: URL(fileURLWithPath: resumePath))
        }
        disclose("CONVERSE: meaning-plan persisted (\(remaining.count) segments remain) — Neuron can resume the thread.")
    }
    func clearResume() { try? FileManager.default.removeItem(atPath: resumePath) }
    func finish() { player.stop(); if micLive { engine.inputNode.removeTap(onBus: 0) }; engine.stop() }
}

// ----------------------------------------------------------------------------
// CLI
// ----------------------------------------------------------------------------
func loadManifest(_ path: String) -> (segs: [Segment], utterance: String) {
    guard let d = FileManager.default.contents(atPath: path),
          let o = try? JSONSerialization.jsonObject(with: d) as? [String: Any],
          let arr = o["segments"] as? [[String: Any]] else { die("bad manifest: \(path)") }
    let segs = arr.map { Segment(file: $0["file"] as? String ?? "",
                                 salience: ($0["salience"] as? NSNumber)?.doubleValue ?? 0.5,
                                 text: $0["text"] as? String ?? "") }
    return (segs, o["utterance"] as? String ?? "")
}

let args = CommandLine.arguments
guard args.count >= 2 else {
    print("""
    periph — Neuron peripheral I/O (own-core, local, consent-gated)
      grant <camera|mic>            grant a sensitive sense (Neuron-level consent)
      revoke <camera|mic>           revoke it
      status                        show consent state
      speak <file.wav>              SPEAK ALOUD (efferent) via the speaker
      tone <out.wav> [hz] [sec]     own-core synth a test WAV (no deps)
      listen <sec> <out.wav>        MIC capture (afferent) 16k mono
      see <out.jpg>                 CAMERA one frame (afferent)
      feat-audio <file.wav>         extract compact voice/sound signature (for ingest)
      feat-image <file.jpg>         extract compact scene-geometry (for ingest)
      ingest-audio <file.wav> <engramURL>   capture -> descriptor -> engram node (geometry)
      ingest-image <file.jpg> <engramURL>   capture -> descriptor -> engram node (geometry)
      voiceprint <voice.wav>        extract voice-signature (F0 + formants F1-F5)
      imitate <voice.wav> <out.wav> speak back in that voice (LPC analysis-resynthesis)
      hear-imitate <sec> <out.wav>  MIC -> extract signature -> imitate -> SPEAK ALOUD
      wav-info <file.wav>           print WAV geometry
      converse <manifest.json> [--authority F] [--barge-at S[:backchannel|:bargein]] [--resume]
                                    full-duplex interruptible utterance
    """)
    exit(0)
}

switch args[1] {
case "grant":
    guard args.count >= 3 else { die("grant needs a device") }
    var g = Consent.load(); g[args[2]] = true; Consent.save(g)
    disclose("granted '\(args[2])' — the user consents; raw stream stays local, never egresses.")
    emit(["ok": true, "op": "grant", "device": args[2], "consent": g])
case "revoke":
    guard args.count >= 3 else { die("revoke needs a device") }
    var g = Consent.load(); g[args[2]] = false; Consent.save(g)
    emit(["ok": true, "op": "revoke", "device": args[2], "consent": g])
case "status":
    emit(["ok": true, "op": "status", "consent": Consent.load()])
case "speak":
    guard args.count >= 3 else { die("speak needs a wav") }
    speak(args[2])
case "tone":
    guard args.count >= 3 else { die("tone needs an out path") }
    let hz = args.count >= 4 ? Double(args[3]) ?? 220 : 220
    let sec = args.count >= 5 ? Double(args[4]) ?? 1.0 : 1.0
    let sr = 16000
    var s = [Int16](); s.reserveCapacity(Int(Double(sr)*sec))
    for i in 0..<Int(Double(sr)*sec) {
        let t = Double(i)/Double(sr)
        let env = min(1.0, min(t*20, (sec - t)*20))          // gentle attack/release
        s.append(Int16(env * 0.3 * 32767 * sin(2*Double.pi*hz*t)))
    }
    writeWav(URL(fileURLWithPath: args[2]), samples: s, sampleRate: sr)
    disclose("tone: wrote own-core \(sec)s @ \(hz)Hz WAV to \(args[2]).")
    emit(["ok": true, "op": "tone", "file": args[2], "hz": hz, "seconds": sec])
case "listen":
    guard args.count >= 4 else { die("listen needs <sec> <out.wav>") }
    listen(seconds: Double(args[2]) ?? 3.0, out: args[3])
case "see":
    guard args.count >= 3 else { die("see needs an out path") }
    see(out: args[2])
case "feat-audio":
    guard args.count >= 3 else { die("feat-audio needs a wav") }
    featAudio(args[2])
case "feat-image":
    guard args.count >= 3 else { die("feat-image needs an image") }
    featImage(args[2])
case "ingest-audio":
    guard args.count >= 4 else { die("ingest-audio needs <wav> <engramURL>") }
    ingest(args[2], kind: "audio", engramURL: args[3])
case "ingest-image":
    guard args.count >= 4 else { die("ingest-image needs <image> <engramURL>") }
    ingest(args[2], kind: "image", engramURL: args[3])
case "voiceprint":
    guard args.count >= 3 else { die("voiceprint needs a wav") }
    let vp = voiceprint(args[2])
    disclose("VOICEPRINT: \(vp.content)")
    emit(["ok": true, "op": "voiceprint", "file": args[2], "f0_hz": vp.f0,
          "f0_range": [vp.f0lo, vp.f0hi], "formants_hz": vp.formants.map { $0.0 },
          "bandwidths_hz": vp.formants.map { $0.1 }, "content": vp.content,
          "ingest": ["node_type": "Observation", "tier": "Episodic", "content": vp.content]])
case "imitate":
    guard args.count >= 4 else { die("imitate needs <voice.wav> <out.wav>") }
    imitate(inPath: args[2], outPath: args[3])
case "hear-imitate":
    guard args.count >= 4 else { die("hear-imitate needs <sec> <out.wav>") }
    let secs = Double(args[2]) ?? 4.0
    let outp = args[3]
    let capp = outp.replacingOccurrences(of: ".wav", with: "") + ".heard.wav"
    disclose("HEAR-IMITATE: open the ear, listen \(secs)s, grab the voice, speak it back.")
    listen(seconds: secs, out: capp)                 // afferent: hear the voice
    imitate(inPath: capp, outPath: outp)             // extract signature + resynthesize
    speak(outp)                                      // efferent: speak back ALOUD in that voice
case "wav-info":
    guard args.count >= 3, let i = wavInfo(args[2]) else { die("wav-info needs a readable wav") }
    disclose("WAV \(args[2]): \(i.sampleRate)Hz \(i.channels)ch \(i.bits)bit \(i.frames) frames")
    emit(["ok": true, "op": "wav-info", "sample_rate": i.sampleRate, "channels": i.channels,
          "bits": i.bits, "frames": i.frames,
          "seconds": Double(i.frames)/Double(max(i.sampleRate,1))])
case "converse":
    guard args.count >= 3 else { die("converse needs a manifest") }
    let (segs, utter) = loadManifest(args[2])
    var authority = 0.5
    var bargeAt: Double? = nil
    var bargeKind = "bargein"
    var resume = false
    var liveMic = false
    var i = 3
    while i < args.count {
        switch args[i] {
        case "--authority": if i+1 < args.count { authority = Double(args[i+1]) ?? 0.5; i += 1 }
        case "--barge-at":
            if i+1 < args.count {
                let parts = args[i+1].split(separator: ":")
                bargeAt = Double(parts[0]) ?? nil
                if parts.count > 1 { bargeKind = String(parts[1]) }
                i += 1
            }
        case "--resume": resume = true
        case "--live-mic": liveMic = true
        default: break
        }
        i += 1
    }
    let resumePath = (ProcessInfo.processInfo.environment["PERIPH_HOME"]
        ?? FileManager.default.currentDirectoryPath + "/peripheral") + "/.resume.json"
    var startIndex = 0
    var runSegs = segs
    if resume, let d = FileManager.default.contents(atPath: resumePath),
       let o = try? JSONSerialization.jsonObject(with: d) as? [String: Any],
       let rem = o["remaining"] as? [[String: Any]] {
        runSegs = rem.map { Segment(file: $0["file"] as? String ?? "",
                                    salience: ($0["salience"] as? NSNumber)?.doubleValue ?? 0.5,
                                    text: $0["text"] as? String ?? "") }
        startIndex = 0
        disclose("CONVERSE: resuming — \"as I was saying...\" (\(runSegs.count) segments left).")
        emit(["op": "converse", "event": "resume", "remaining": runSegs.count])
    }
    if runSegs.isEmpty { die("no segments to speak") }
    disclose("CONVERSE: utterance = \"\(utter)\" (\(runSegs.count) segments).")
    let convo = Conversation(resumePath: resumePath)
    convo.run(runSegs, interrupterAuthority: authority,
              injectBargeAt: bargeAt, injectKind: bargeKind, startIndex: startIndex, liveMic: liveMic)
default:
    die("unknown command: \(args[1])")
}