<!doctype html>
<title>Navigating to a text fragment anchor</title>
<script src="stash.js"></script>
<script>
function isInView(element) {
  let rect = element.getBoundingClientRect();
  return rect.top >= 0 && rect.top <= window.innerHeight
      && rect.left >= 0 && rect.left <= window.innerWidth;
}

function checkScroll() {
  let position = 'unknown';
  if (window.scrollY == 0)
    position = 'top';
  else if (isInView(document.getElementById('element')))
    position = 'element';
  else if (isInView(document.getElementById('text')))
    position = 'text';
  else if (isInView(document.getElementById('more-text')))
    position = 'more-text';
  else if (isInView(document.getElementById('cross-node-context')))
    position = 'cross-node-context';
  else if (isInView(document.getElementById('text-directive-parameters')))
    position = 'text-directive-parameters';
  else if (isInView(document.getElementById('shadow-parent')))
    position = 'shadow-parent';
  else if (isInView(document.getElementById('hidden')))
    position = 'hidden';
  else if (isInView(document.getElementById('horizontal-scroll')) && window.scrollX > 0)
    position = 'horizontal-scroll';

  let target = document.querySelector(":target");

  if (!target && position == 'shadow-parent') {
    let shadow = document.getElementById("shadow-parent").shadowRoot.firstElementChild;
    if (shadow.matches(":target")) {
      target = shadow;
      position = 'shadow';
    }
  }

  let results = {
    scrollPosition: position,
    href: window.location.href,
    target: target ? target.id : 'undefined'
  };

  let key = (new URL(document.location)).searchParams.get("key");
  stashResultsThenClose(key, results);
}

// Ensure two animation frames on load to test the fallback to element anchor,
// which gets queued for the next frame if the text fragment is not found.
window.onload = function() {
  window.requestAnimationFrame(function() {
    window.requestAnimationFrame(checkScroll);
  })
}
</script>
<style>
  .scroll-section {
    /* 1000px margin on top and bottom so only one section can be in view. */
    margin: 1000px 0px;
  }
  #hidden {
    visibility: hidden;
  }
  #horizontal-scroll {
    margin-left: 2000px;
  }
  #display-none {
    display: none;
  }
</style>
<body>
  <div id="element" class="scroll-section">Element</div>
  <p id="text" class="scroll-section">
    This is a test page !$'()*+./:;=?@_~ &,- &#x30cd;&#x30b3;
    <br>
    foo foo foo bar bar bar
  </p>
  <p id="more-text" class="scroll-section">More test page text</p>
  <div class="scroll-section">
    <div>
      <p>prefix</p>
      <p id="cross-node-context">test page</p>
    </div>
    <div><p>suffix</p></div>
  </div>
  <p id="text-directive-parameters" class="scroll-section">this,is,test,page</p>
  <div id="shadow-parent" class="scroll-section"></div>
  <script>
    let shadow = document.getElementById("shadow-parent").attachShadow({mode: 'open'});
    shadow.innerHTML = '<p id="shadow">shadow text</p>';
  </script>
  <p id="hidden" class="scroll-section">hidden text</p>
  <p id="horizontal-scroll" class="scroll-section">horizontally scrolled text</p>
  <p id="display-none" class="scroll-section">display none</p>
</body>