<!DOCTYPE html>
<meta charset="utf-8">
<title>Worker Blob Fetcher</title>
<script>
  window.addEventListener("message", function (evt) {
    const { url } = evt.data;

    const workerScriptContent = `
      async function doFetch(url) {
        const response = await fetch(url);
        const body = await response.text();
        return {
          status: response.status,
          body,
        };
      }

      async function fetchAndPost(url) {
        try {
          const message = await doFetch(url);
          self.postMessage(message);
        } catch(e) {
          self.postMessage({ error: e.name });
        }
      }

      fetchAndPost("${url}");
    `;
    const blob =
        new Blob([workerScriptContent], {type: 'application/javascript'});
    const workerScriptUrl = URL.createObjectURL(blob);

    const worker = new Worker(workerScriptUrl);

    URL.revokeObjectURL(workerScriptUrl);

    worker.addEventListener("message", (evt) => {
      parent.postMessage(evt.data, "*");
    });

    worker.addEventListener("error", (evt) => {
      parent.postMessage({ error: evt.message || "unknown error" }, "*");
    });
  });
</script>
