frontend/audio_features.js

window.WhistleCoach = window.WhistleCoach || {};

window.WhistleCoach.AudioFeatures = (() => {
  const clamp = (value, minimum = 0, maximum = 1) =>
    Math.min(maximum, Math.max(minimum, value));

  function toFeaturePayload(audio, stableDurationMs = 0) {
    return {
      rms_volume: Number(audio?.rms || 0),
      airflow_score: Number(audio?.airflow || 0),
      peak_frequency_hz: Number(audio?.peakFrequency || 0),
      pitch_stability_score: Number(audio?.tone || 0),
      stable_duration_ms: Math.round(stableDurationMs || 0),
    };
  }

  function classifyAudio(features) {
    if (features.airflow_score < 0.32) return "no_airflow";
    if (features.pitch_stability_score < 0.58) return "airflow_no_tone";
    if (features.stable_duration_ms >= 2000) return "stable_whistle";
    return "tone_starting";
  }

  function pitchToMidi(frequencyHz) {
    if (!frequencyHz || frequencyHz <= 0) return null;
    return Math.round(69 + 12 * Math.log2(frequencyHz / 440));
  }

  function midiToName(midi) {
    if (midi === null) return "";
    const names = ["C", "C#", "D", "D#", "E", "F", "F#", "G", "G#", "A", "A#", "B"];
    return `${names[((midi % 12) + 12) % 12]}${Math.floor(midi / 12) - 1}`;
  }

  return {
    toFeaturePayload,
    classifyAudio,
    pitchToMidi,
    midiToName,
  };
})();