nested.py - mozsearch

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def main(request, response):

    origin = request.GET.first(b"origin");

    value = request.GET.first(b"value");

    # This is used to solve the race condition we have for postMessages

    shouldSucceed = request.GET.first(b"loadShouldSucceed", b"false");

    return ([(b"Content-Type", b"text/html")],

            b"""<!DOCTYPE html>

<title>XFO.</title>

<body>

<script>

  var gotMessage = false;

  window.addEventListener("message", e => {

    gotMessage = true;

    window.parent.postMessage(e.data, "*");

});

  var i = document.createElement("iframe");

  i.src = "%s/x-frame-options/support/xfo.py?value=%s";

  i.onload = _ => {

    // Why 100ms timeout? Because that seems to be enough to stop the

    // load event from racing with the onmessage event, and it's at least

    // as long as the two renderAnimationFrame calls that used to be here.

    setTimeout(_ => {

      // The race condition problem we have is it is possible

      // that the sub iframe is loaded before the postMessage is

      // dispatched, as a result, the "Failed" message is sent

      // out. So the way we fixed is we simply let the timeout

      // to happen if we expect the "Loaded" postMessage to be

      // sent

      if (!gotMessage && %s != true) {

        window.parent.postMessage("Failed", "*");

    }, 100);

};

  document.body.appendChild(i);

</script>

            """ % (origin, value, shouldSucceed))