<!doctype html>
<meta charset=utf-8>
<title></title>
<script src=/resources/testharness.js></script>
<script src=/resources/testharnessreport.js></script>
<script>

function parseBlob(blob) {
  return new Promise(resolve => {
    let xhr = new XMLHttpRequest();
    xhr.open("GET", URL.createObjectURL(blob));
    xhr.onload = () => {
      resolve(xhr.responseXML);
    }
    xhr.send();
  });
}

promise_test(async (t) => {
  // Most browser engines, including Gecko, use 5000 as the limit, so test a
  // range around that.
  const cutoff = 5000;

  let minDepth = cutoff - 100;
  let maxDepth = cutoff + 100;

  // Generate a string with elements nested maxDepth deep.
  const openTag = "<x>";
  const closeTag = "</x>";
  let xml = openTag.repeat(maxDepth) + closeTag.repeat(maxDepth);

  // Compute where we change from opening to closing tags.
  const middle = maxDepth * openTag.length;

  // Create a blob around the string.
  let blob = new Blob([xml], { type: "application/xml" });

  while (minDepth < maxDepth) {
    // Try to parse a number of nested tags between minDepth and maxDepth.
    let test = Math.ceil((minDepth + maxDepth) / 2);

    // We need the number of opening and closing tags to be equal to the number
    // that we calculated above.
    let slice = blob.slice(middle - (test * openTag.length),
                           middle + (test * closeTag.length));

    let responseXML = await parseBlob(slice);

    // Move either minDepth or maxDepth so that the actual limit is still in the
    // range of [minDepth-maxDepth].
    if (responseXML) {
      // Depth is ok.
      minDepth = test;
    } else {
      maxDepth = test - 1;
    }
  }
  assert_equals(minDepth, maxDepth);
  assert_equals(minDepth, cutoff);
},"Parsing XML fails when the nesting depth is 5000");

</script>
