type WhisperTranscribeInput = {
  samples: Float32Array;
  sampleRate: number;
  language?: string;
};

function getWhisperUrl() {
  return (process.env.WHISPER_URL ?? "http://whisper:9000").replace(/\/+$/, "");
}

function getWhisperLanguage() {
  const value = (process.env.CF_WHISPER_LANGUAGE ?? "ru").trim();
  return value || "ru";
}

function pcmToWav(samples: Float32Array, sampleRate: number): Buffer {
  const numChannels = 1;
  const bitsPerSample = 16;
  const byteRate = sampleRate * numChannels * (bitsPerSample / 8);
  const blockAlign = numChannels * (bitsPerSample / 8);
  const dataSize = samples.length * (bitsPerSample / 8);
  const headerSize = 44;
  const buffer = Buffer.alloc(headerSize + dataSize);

  // RIFF header
  buffer.write("RIFF", 0);
  buffer.writeUInt32LE(36 + dataSize, 4);
  buffer.write("WAVE", 8);

  // fmt chunk
  buffer.write("fmt ", 12);
  buffer.writeUInt32LE(16, 16);
  buffer.writeUInt16LE(1, 20); // PCM
  buffer.writeUInt16LE(numChannels, 22);
  buffer.writeUInt32LE(sampleRate, 24);
  buffer.writeUInt32LE(byteRate, 28);
  buffer.writeUInt16LE(blockAlign, 32);
  buffer.writeUInt16LE(bitsPerSample, 34);

  // data chunk
  buffer.write("data", 36);
  buffer.writeUInt32LE(dataSize, 40);

  for (let i = 0; i < samples.length; i += 1) {
    const s = Math.max(-1, Math.min(1, samples[i] ?? 0));
    const val = s < 0 ? s * 0x8000 : s * 0x7fff;
    buffer.writeInt16LE(Math.round(val), headerSize + i * 2);
  }

  return buffer;
}

export async function transcribeWithWhisper(input: WhisperTranscribeInput) {
  const wav = pcmToWav(input.samples, input.sampleRate);
  const language = (input.language ?? getWhisperLanguage()) || "ru";
  const url = `${getWhisperUrl()}/asr?task=transcribe&language=${language}&output=json`;

  const formData = new FormData();
  formData.append("audio_file", new Blob([wav], { type: "audio/wav" }), "audio.wav");

  const response = await fetch(url, { method: "POST", body: formData });
  if (!response.ok) {
    const detail = await response.text().catch(() => "");
    throw new Error(`Whisper service error ${response.status}: ${detail}`);
  }

  const result = (await response.json()) as { text?: string };
  return String(result?.text ?? "").trim();
}