import { IReadAB, readAB } from './aba.js';

export async function sfbkstream(url: string) {
  const ab = await (
    await fetch(url, { headers: { Range: 'bytes=0-6400' } })
  ).arrayBuffer();
  const [preample, r] = skipToSDTA(ab);

  const sdtaSize = r.get32();
  const stdstart = r.offset + 8;
  const pdtastart = stdstart + sdtaSize + 4;
  const rangeHeader = {
    headers: {
      Range: 'bytes=' + stdstart + '-' + pdtastart,
    },
  };
  const pdtaHeader = {
    headers: { Range: 'bytes=' + pdtastart + '-' },
  };
  const { readable, writable } = new TransformStream();
  (await fetch(url, rangeHeader)).body!.pipeTo(writable);
  return {
    nsamples: (pdtastart - stdstart) / 2,
    sdtaStream: readable,
    infos: preample,
    pdtaBuffer: new Uint8Array(
      await (await fetch(url, pdtaHeader)).arrayBuffer()
    ),
  };
}

function skipToSDTA(ab: ArrayBuffer): [any, IReadAB] {
  const infosection = new Uint8Array(ab);

  const r = readAB(infosection);
  const [riff, filesize, sig, list] = [
    r.readNString(4),
    r.get32(),
    r.readNString(4),
    r.readNString(4),
  ];
  console.assert(riff == 'RIFF' && sig == 'sfbk');

  let infosize = r.get32();

  console.log(r.readNString(4), filesize, list, r.offset);
  console.log(infosize, r.offset);
  const infos: { section: string; text: string }[] = [];
  while (infosize >= 8) {
    const [section, size] = [r.readNString(4), r.get32()];
    infos.push({ section, text: r.readNString(size) });
    infosize = infosize - 8 - size;
  }
  console.assert(r.readNString(4) == 'LIST');
  return [infos, r];
}