<!DOCTYPE html>
<html>
<script>

const fetchURL = new URL('sample.txt', window.location).href;

const frameControllerText =
`<script>
  let t = null;
  try {
    if (navigator.serviceWorker.controller) {
      t = navigator.serviceWorker.controller.scriptURL;
    }
  } catch (e) {
    t = e.message;
  } finally {
    parent.postMessage({ data: t }, '*');
  }
</` + `script>`;

const frameFetchText =
`<script>
  fetch('${fetchURL}', { mode: 'no-cors' }).then(response => {
    return response.text();
  }).then(text => {
    parent.postMessage({ data: text }, '*');
  }).catch(e => {
    parent.postMessage({ data: e.message }, '*');
  });
</` + `script>`;

const workerControllerText =
`let t = navigator.serviceWorker.controller
       ? navigator.serviceWorker.controller.scriptURL
       : null;
self.postMessage(t);`;

const workerFetchText =
`fetch('${fetchURL}', { mode: 'no-cors' }).then(response => {
  return response.text();
}).then(text => {
  self.postMessage(text);
}).catch(e => {
  self.postMessage(e.message);
});`

function getChildText(opts) {
  if (opts.child === 'iframe') {
    if (opts.check === 'controller') {
      return frameControllerText;
    }

    if (opts.check === 'fetch') {
      return frameFetchText;
    }

    throw('unexpected feature to check: ' + opts.check);
  }

  if (opts.child === 'worker') {
    if (opts.check === 'controller') {
      return workerControllerText;
    }

    if (opts.check === 'fetch') {
      return workerFetchText;
    }

    throw('unexpected feature to check: ' + opts.check);
  }

  throw('unexpected child type ' + opts.child);
}

function makeURL(opts) {
  let mimetype = opts.child === 'iframe' ? 'text/html'
                                         : 'text/javascript';

  if (opts.scheme === 'blob') {
    let blob = new Blob([getChildText(opts)], { type: mimetype });
    return URL.createObjectURL(blob);
  }

  if (opts.scheme === 'data') {
    return `data:${mimetype},${getChildText(opts)}`;
  }

  throw(`unexpected URL scheme ${opts.scheme}`);
}

function testWorkerChild(url) {
  let w = new Worker(url);
  return new Promise((resolve, reject) => {
    w.onmessage = resolve;
    w.onerror = evt => {
      reject(evt.message);
    }
  });
}

function testIframeChild(url) {
  let frame = document.createElement('iframe');
  frame.src = url;
  document.body.appendChild(frame);

  return new Promise(resolve => {
    addEventListener('message', evt => {
      resolve(evt.data);
    }, { once: true });
  });
}

function testURL(opts, url) {
  if (opts.child === 'worker') {
    return testWorkerChild(url);
  }

  if (opts.child === 'iframe') {
    return testIframeChild(url);
  }

  throw(`unexpected child type ${opts.child}`);
}

function checkChildController(opts) {
  let url = makeURL(opts);
  return testURL(opts, url);
}
</script>
</html>
