/**
 * Float32 [-1, 1] PCM → WAV blob (mono, 16-bit, заданная частота).
 * Используется браузером для отправки записанной фразы в STT.
 */

export function floatToWav(audio: Float32Array, sampleRate = 16000): Blob {
  const numSamples = audio.length
  const buffer = new ArrayBuffer(44 + numSamples * 2)
  const view = new DataView(buffer)

  writeStr(view, 0, 'RIFF')
  view.setUint32(4, 36 + numSamples * 2, true)
  writeStr(view, 8, 'WAVE')
  writeStr(view, 12, 'fmt ')
  view.setUint32(16, 16, true)              // fmt chunk size
  view.setUint16(20, 1, true)               // PCM
  view.setUint16(22, 1, true)               // channels
  view.setUint32(24, sampleRate, true)
  view.setUint32(28, sampleRate * 2, true)  // byte rate
  view.setUint16(32, 2, true)               // block align
  view.setUint16(34, 16, true)              // bits per sample
  writeStr(view, 36, 'data')
  view.setUint32(40, numSamples * 2, true)

  let offset = 44
  for (let i = 0; i < numSamples; i++, offset += 2) {
    const s = Math.max(-1, Math.min(1, audio[i]))
    view.setInt16(offset, s < 0 ? s * 0x8000 : s * 0x7fff, true)
  }
  return new Blob([buffer], { type: 'audio/wav' })
}

function writeStr(view: DataView, offset: number, s: string): void {
  for (let i = 0; i < s.length; i++) view.setUint8(offset + i, s.charCodeAt(i))
}