middleware v1

middleware.v1.js

// const cachedAssetPath = ...
try {
  if (fs.existsSync(cachedAssetPath)) {
    const response = await fetch(res.locals.fetchUrl, { method: "HEAD" });

    res.locals.contentLength = response.headers.get("content-length");
    res.locals.contentType = response.headers.get("content-type");
    res.locals.buffer = fs.readFileSync(cachedAssetPath);
  } else {
    const blob = await (await fetch(res.locals.fetchUrl)).blob();
    res.locals.buffer = Buffer.from(await blob.arrayBuffer(), "binary");

    res.locals.contentType = blob.type;
    res.localscontentLength = blob.size;

    fs.writeFileSync(cachedAssetPath, res.locals.buffer);
  }

  next();
} catch (e) {
  // in case fs.writeFileSync writes partial data and fails
  if (fs.existsSync(cachedAssetPath)) {
    fs.unlinkSync(cachedAssetPath);
  }

  res.status(500).send(e.message);
}