!7

cmodule ListenOnNoise > DynPrintLogAndEnabled {
  switchable double threshold = 50;  // volume percentage
  switchable double minDurationAfterNoise = 1.5; // seconds
  switchable double maxDuration = 10.0; // seconds

  transient float lastVolume;
  transient long lastNoise; // in sysNow time
  
  start {
    dm_addAudioListener(voidfunc(short[] data) {
      if (!enabled) ret;
      
      // Quickly calculate the volume
      float vol = shortSamplesToPercentVolume(data);
      
      short[] clonedBuf = vol >= threshold && lastVolume < threshold
        ? cloneShortArray(data) : null;

      q.add(r {
        S recorder = dm_requireQuickAudioRecord();
        long recordingSince = cast dm_call(recorder, 'recordingSince);
        bool noise = vol >= threshold;
        bool isRecording = recordingSince != 0;
        if (noise) lastNoise = sysNow();
        if (isRecording) {
          // stop if max duration reached or no recent noise
          if (elapsedSeconds(recordingSince) >= maxDuration
            || elapsedSeconds(lastNoise) > minDurationAfterNoise)
          dm_call(recorder, 'stopRecording);
        } else {
          // start recording
          if (noise) {
            sleep(10); // avoid audio listener race condition
            dm_call(recorder, 'startRecording, clonedBuf); 
          }
        }
      });
    });
  }
}