'use strict';

const fs = require('fs').promises;
const path = require('path');
const { createWriteStream } = require('fs');
const { pipeline } = require('stream/promises');
const { Readable } = require('stream');

async function downloadBodyToFile(res, destPath) {
  if (!res.ok) {
    const errText = await res.text().catch(() => '');
    throw new Error(`HTTP ${res.status}: ${errText.slice(0, 500)}`);
  }
  if (!res.body) {
    throw new Error('download has no body');
  }
  await fs.mkdir(path.dirname(destPath), { recursive: true });
  const tmp = destPath + '.downloading';
  let body = res.body;
  if (body && typeof body.pipe !== 'function') {
    body = Readable.fromWeb(body);
  }
  await pipeline(body, createWriteStream(tmp));
  const st = await fs.stat(tmp);
  if (st.size === 0) {
    await fs.unlink(tmp).catch(() => {});
    throw new Error('empty download');
  }
  await fs.rename(tmp, destPath);
}

async function fetchToFile(url, headers, destPath) {
  const res = await fetch(url, {
    headers,
    redirect: 'follow',
  });
  await downloadBodyToFile(res, destPath);
}

module.exports = { fetchToFile, downloadBodyToFile };