// Convert Float32Array (Web Audio API) to PCM Int16 (Gemini API requirement)
export function floatTo16BitPCM(float32Array: Float32Array): ArrayBuffer {
  const buffer = new ArrayBuffer(float32Array.length * 2);
  const view = new DataView(buffer);
  let offset = 0;
  for (let i = 0; i < float32Array.length; i++) {
    let s = Math.max(-1, Math.min(1, float32Array[i]));
    s = s < 0 ? s * 0x8000 : s * 0x7FFF;
    view.setInt16(offset, s, true); // Little Endian
    offset += 2;
  }
  return buffer;
}

// Manual encoding helper as per guidelines
export function encodeBase64(bytes: Uint8Array): string {
  let binary = '';
  const len = bytes.byteLength;
  for (let i = 0; i < len; i++) {
    binary += String.fromCharCode(bytes[i]);
  }
  return btoa(binary);
}

// Manual decoding helper as per guidelines
export function decodeBase64(base64: string): Uint8Array {
  const binaryString = atob(base64);
  const len = binaryString.length;
  const bytes = new Uint8Array(len);
  for (let i = 0; i < len; i++) {
    bytes[i] = binaryString.charCodeAt(i);
  }
  return bytes;
}

// Decode raw PCM data from Gemini to AudioBuffer
export async function decodeAudioData(
  data: Uint8Array,
  ctx: AudioContext,
  sampleRate: number = 24000,
  numChannels: number = 1,
): Promise<AudioBuffer> {
  // Ensure the byte length is even for Int16Array
  if (data.byteLength % 2 !== 0) {
      data = data.subarray(0, data.byteLength - 1);
  }

  const dataInt16 = new Int16Array(data.buffer, data.byteOffset, data.byteLength / 2);
  const buffer = ctx.createBuffer(numChannels, dataInt16.length / numChannels, sampleRate);

  for (let channel = 0; channel < numChannels; channel++) {
    const channelData = buffer.getChannelData(channel);
    for (let i = 0; i < dataInt16.length; i++) {
      channelData[i] = dataInt16[i] / 32768.0;
    }
  }
  return buffer;
}