// Mono PCM WAV encoding (16- or 24-bit).

export function encodeWav(y: Float32Array, sampleRate: number, bitDepth: 16 | 24): Blob {
  const bytesPerSample = bitDepth / 8;
  const dataSize = y.length * bytesPerSample;
  const buf = new ArrayBuffer(44 + dataSize);
  const dv = new DataView(buf);
  const writeStr = (off: number, s: string) => {
    for (let i = 0; i < s.length; i++) dv.setUint8(off + i, s.charCodeAt(i));
  };
  writeStr(0, 'RIFF');
  dv.setUint32(4, 36 + dataSize, true);
  writeStr(8, 'WAVE');
  writeStr(12, 'fmt ');
  dv.setUint32(16, 16, true);
  dv.setUint16(20, 1, true); // PCM
  dv.setUint16(22, 1, true); // mono
  dv.setUint32(24, sampleRate, true);
  dv.setUint32(28, sampleRate * bytesPerSample, true);
  dv.setUint16(32, bytesPerSample, true);
  dv.setUint16(34, bitDepth, true);
  writeStr(36, 'data');
  dv.setUint32(40, dataSize, true);

  let off = 44;
  for (let i = 0; i < y.length; i++) {
    const v = Math.max(-1, Math.min(1, y[i]));
    if (bitDepth === 16) {
      dv.setInt16(off, Math.round(v * 32767), true);
      off += 2;
    } else {
      const iv = Math.round(v * 8388607);
      dv.setUint8(off, iv & 0xff);
      dv.setUint8(off + 1, (iv >> 8) & 0xff);
      dv.setUint8(off + 2, (iv >> 16) & 0xff);
      off += 3;
    }
  }
  return new Blob([buf], { type: 'audio/wav' });
}