middleware v2

middleware.v2.js

function encodeAssetCacheName(contentType, contentLength) {
  return Buffer.from(`${contentType}:${contentLength}`).toString("base64");
}

function decodeAssetCacheName(encodedString) {
  const decodedFileName = Buffer.from(encodedString, "base64").toString(
    "ascii"
  );
  return decodedFileName.split(":");
}

// ...

if (fs.existsSync(assetCachePath)) {
  const firstFile = fs.readdirSync(assetCachePath)[0];

  const [contentType, contentLength] = middleWare.decodeAssetCacheName(
    firstFile
  );

  res.locals.contentLength = contentLength;
  res.locals.contentType = contentType;

  res.locals.buffer = fs.readFileSync(`${assetCachePath}/${firstFile}`);
} else {
  const blob = await (await fetch(res.locals.fetchUrl)).blob();

  const fileName = middleWare.encodeAssetCacheName(blob.type, blob.size);

  res.locals.buffer = Buffer.from(await blob.arrayBuffer(), "binary");

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

  fs.writeFileSync(`${assetCachePath}/${fileName}`, res.locals.buffer);
}

next();