// Phoenix binary WebSocket packet decoders. Keep this module dependency-free so
// protocol compatibility can be tested without a browser.

export function decodePhoenixSpectroBuffer(buffer) {
  if (!(buffer instanceof ArrayBuffer) || buffer.byteLength < 20) return null;
  const view = new DataView(buffer);
  if (view.getUint32(0, true) !== 0x50585350) return null;
  const seq = view.getUint32(4, true);
  const sampleRate = view.getUint32(8, true);
  const fftSize = view.getUint32(12, true);
  const count = view.getUint32(16, true);
  if (count < 1 || buffer.byteLength !== 20 + count * 4) return null;
  return {
    seq,
    sampleRate,
    fftSize,
    bins: new Float32Array(buffer, 20, count),
  };
}

export function decodePhoenixVisualsBuffer(buffer) {
  if (!(buffer instanceof ArrayBuffer) || buffer.byteLength < 32) return null;
  const view = new DataView(buffer);
  if (view.getUint32(0, true) !== 0x50585653 || view.getUint16(4, true) !== 1) return null;
  const flags = view.getUint16(6, true);
  const seq = view.getUint32(8, true);
  const xyCount = view.getUint32(12, true);
  const waveColumns = view.getUint32(16, true);
  const waveChannels = view.getUint16(20, true);
  const waveColumnSamples = view.getUint32(24, true);
  const waveSampleRate = view.getUint32(28, true);
  if (waveChannels > 2) return null;
  const xyBytes = xyCount * 8;
  const waveValues = waveColumns * waveChannels * 2;
  const expectedBytes = 32 + xyBytes + waveValues * 4;
  if (!Number.isSafeInteger(expectedBytes) || buffer.byteLength !== expectedBytes) return null;

  let offset = 32;
  let left = null;
  let right = null;
  if ((flags & 1) && xyCount > 0) {
    left = new Float32Array(xyCount);
    right = new Float32Array(xyCount);
    for (let index = 0; index < xyCount; index++) {
      left[index] = view.getFloat32(offset, true);
      right[index] = view.getFloat32(offset + 4, true);
      offset += 8;
    }
  } else {
    offset += xyBytes;
  }

  let wave = null;
  if ((flags & 2) && waveValues > 0 && (waveChannels === 1 || waveChannels === 2)) {
    const data = new Float32Array(waveValues);
    for (let index = 0; index < waveValues; index++) {
      data[index] = view.getFloat32(offset + index * 4, true);
    }
    wave = {
      data,
      columns: waveColumns,
      channels: waveChannels,
      columnSamples: waveColumnSamples,
      sampleRate: waveSampleRate,
    };
  }
  return { seq, left, right, wave };
}