private const val tag = "TalkMode"

private const val realtimeSampleRateHz = 24_000

private const val realtimeAudioFrameMs = 100

private const val realtimeSpeechStartAverageAmplitude = 800

private const val realtimeSpeechContinueAverageAmplitude = 800

private const val realtimeSpeechStartFrameCount = 3

private const val realtimeSpeechHangoverMs = 700L

private const val listenWatchdogMs = 12_000L

private const val chatFinalWaitWithSubscribeMs = 45_000L

private const val chatFinalWaitWithoutSubscribeMs = 6_000L

private val realtimePlaybackLock = Any()

private var realtimeAudioTrack: AudioTrack? = null

private var realtimePlaybackIdleJob: Job? = null

private var realtimePlaybackEndsAtMs = 0L

@Volatile private var realtimePlaybackEndsAtMs = 0L

@Volatile private var realtimeSpeechActiveUntilMs = 0L

private var realtimeSpeechCandidateFrames = 0

@Volatile private var realtimeOutputSuppressed = false

realtimeSessionId = sessionId

realtimeOutputSuppressed = false

resetRealtimeSpeechGate()

_isListening.value = true

_statusText.value = "Listening"

startRealtimeCapture(sessionId)

scope.launch(Dispatchers.IO) {

for (frame in audioFrames) {

if (realtimeSessionId != sessionId) continue

if (isRealtimePlaybackActive()) continue

val audioBase64 = Base64.encodeToString(frame, Base64.NO_WRAP)

val params =

buildJsonObject {

while (coroutineContext.isActive && _isEnabled.value && realtimeSessionId == sessionId) {

val read = audioRecord.read(buffer, 0, buffer.size)

if (read <= 0) continue

if (!shouldAppendRealtimeCapturedFrame(buffer, read)) continue

audioFrames.trySend(buffer.copyOf(read))

}

} catch (err: Throwable) {

}

}

private fun shouldAppendRealtimeCapturedFrame(

frame: ByteArray,

length: Int = frame.size,

): Boolean {

if (isRealtimePlaybackActive()) {

resetRealtimeSpeechGate()

return false

}

val now = SystemClock.elapsedRealtime()

val average = pcm16AverageAmplitude(frame, length)

if (now < realtimeSpeechActiveUntilMs) {

if (average >= realtimeSpeechContinueAverageAmplitude) {

realtimeSpeechActiveUntilMs = now + realtimeSpeechHangoverMs

}

return true

}

if (average >= realtimeSpeechStartAverageAmplitude) {

realtimeSpeechCandidateFrames += 1

if (realtimeSpeechCandidateFrames >= realtimeSpeechStartFrameCount) {

realtimeSpeechActiveUntilMs = now + realtimeSpeechHangoverMs

return true

}

return false

}

realtimeSpeechCandidateFrames = 0

return false

}

private fun isRealtimePlaybackActive(): Boolean =

_isSpeaking.value || SystemClock.elapsedRealtime() < realtimePlaybackEndsAtMs

private fun resetRealtimeSpeechGate() {

realtimeSpeechActiveUntilMs = 0L

realtimeSpeechCandidateFrames = 0

}

private fun pcm16AverageAmplitude(

frame: ByteArray,

length: Int,

): Int {

var total = 0L

var count = 0

var index = 0

val limit = length - (length % 2)

while (index < limit) {

val sample =

(frame[index].toInt() and 0xff) or

(frame[index + 1].toInt() shl 8)

val amplitude = kotlin.math.abs(sample.toShort().toInt())

total += amplitude

count += 1

index += 2

}

return if (count == 0) 0 else (total / count).toInt()

}

private fun handleRealtimeTalkEvent(payloadJson: String?) {

if (payloadJson.isNullOrBlank()) return

val obj =