// Playback level: peak normalization, or loudness normalization with a soft clipper.

export type LevelMode = "peak" | "loudness";

/** Returns a copy of `samples` scaled for playback or export, in [-1, 1]. */
export function normalize(samples: Float32Array, fs: number, mode: LevelMode, peak = 0.95): Float32Array {
  const out = new Float32Array(samples.length);
  if (samples.length === 0) return out;
  if (mode === "peak") {
    let max = 0;
    for (let k = 0; k < samples.length; k++) max = Math.max(max, Math.abs(samples[k]));
    const g = max > 0 ? peak / max : 0;
    for (let k = 0; k < samples.length; k++) out[k] = samples[k] * g;
    return out;
  }
  // Loudness: scale the RMS of the sustained part (after the first 50 ms) to -16 dBFS,
  // then soft-clip so that transients cannot exceed the peak.
  const start = Math.min(samples.length - 1, Math.round(0.05 * fs));
  let sum = 0;
  for (let k = start; k < samples.length; k++) sum += samples[k] * samples[k];
  const rms = Math.sqrt(sum / Math.max(1, samples.length - start));
  const g = rms > 0 ? 10 ** (-16 / 20) / rms : 0;
  for (let k = 0; k < samples.length; k++) out[k] = peak * Math.tanh((samples[k] * g) / peak);
  return out;
}