Cloudflare worker which serves raw source code from googlesource.com

worker.js

/**
 * This worker makes sourcecode from googlesource.com accessible as
 * plain text, with permissive CORS headers.
 * This is a workaround for https://github.com/google/gitiles/issues/7 :
 * googlesource.com currently only serves base64-encoded sources, and is
 * not accessible by cross-site requests.
 * 
 * Request URL format: /<subdomain>/<path>
 * This gets the code from https://<subdomain>.googlesource.com/<path>?format=TEXT
 * and base64-decodes it.
 */

// All responses need to have permissive CORS headers.
function responseWithStatus(status, responseText) {
  return new Response(
    responseText,
    {
      status,
      headers: {
        "Content-Type": "text/plain; charset=utf-8",
        "Access-Control-Allow-Origin": "*",
        "X-Content-Type-Options": "nosniff",
      },
    }
  );
}

const routeRegExp = new RegExp("^/(?<subdomain>.*?)/(?<path>.*)$");

async function handleRequest(request) {
  // GET /<subdomain>/<path>
  const pathname = new URL(request.url).pathname;
  const match = routeRegExp.exec(pathname);
  if (match === null) {
    return responseWithStatus(
      404,
      "Format: /<subdomain>/<path>, fetches https://<subdomain>.googlesource.com/<path>?format=TEXT"
    );
  }

  const { subdomain, path } = match.groups;
  const url = `https://${subdomain}.googlesource.com/${path}?format=TEXT`;
  const response = await fetch(url);

  if (response.status !== 200) {
    return responseWithStatus(
      response.status,
      `${url} returned status ${response.status} (${response.statusText})`
    );
  }

  try {
    // Get the base64-encoded text and decode it.
    const encodedText = await response.text();
    const text = atob(encodedText);
      
    return responseWithStatus(200, text);
  } catch (e) {
    throw new Error(`Error parsing response from ${url}: ${e}`);
  }
}

addEventListener("fetch", (event) => {
  event.respondWith(
    handleRequest(event.request).catch(
      (err) => responseWithStatus(500, `${err.name}: ${err.message}\n${err.stack}`)
    )
  );
});