// @flow
import getWindow from './getWindow';
import getNodeName from './getNodeName';
import getComputedStyle from './getComputedStyle';
import { isHTMLElement } from './instanceOf';
import isTableElement from './isTableElement';
import getParentNode from './getParentNode';

function getTrueOffsetParent(element: Element): ?Element {
  if (
    !isHTMLElement(element) ||
    // https://github.com/popperjs/popper-core/issues/837
    getComputedStyle(element).position === 'fixed'
  ) {
    return null;
  }

  return element.offsetParent;
}

// `.offsetParent` reports `null` for fixed elements, while absolute elements
// return the containing block
function getContainingBlock(element: Element) {
  let currentNode = getParentNode(element);

  while (
    isHTMLElement(currentNode) &&
    ['html', 'body'].indexOf(getNodeName(currentNode)) < 0
  ) {
    const css = getComputedStyle(currentNode);

    // This is non-exhaustive but covers the most common CSS properties that
    // create a containing block.
    if (
      css.transform !== 'none' ||
      css.perspective !== 'none' ||
      (css.willChange && (css.willChange === 'transform' || css.willChange === 'perspective'))
    ) {
      return currentNode;
    } else {
      currentNode = currentNode.parentNode;
    }
  }

  return null;
}

// Gets the closest ancestor positioned element. Handles some edge cases,
// such as table ancestors and cross browser bugs.
export default function getOffsetParent(element: Element) {
  const window = getWindow(element);

  let offsetParent = getTrueOffsetParent(element);

  while (
    offsetParent &&
    isTableElement(offsetParent) &&
    getComputedStyle(offsetParent).position === 'static'
  ) {
    offsetParent = getTrueOffsetParent(offsetParent);
  }

  if (
    offsetParent &&
    (getNodeName(offsetParent) === 'html' ||
      (getNodeName(offsetParent) === 'body' &&
        getComputedStyle(offsetParent).position === 'static'))
  ) {
    return window;
  }

  return offsetParent || getContainingBlock(element) || window;
}

@@ -270,16 +270,90 @@
 Node';%0A%0A
+const isFirefox = navigator.userAgent.toLowerCase().includes('firefox');%0A%0A
 function
@@ -1090,109 +1090,305 @@
     
-if (%0A      css.transform !== 'none' %7C%7C%0A      css.perspective !== 'none' %7C%7C%0A      (css.willChange
+// https://developer.mozilla.org/en-US/docs/Web/CSS/Containing_block#identifying_the_containing_block%0A    if (%0A      css.transform !== 'none' %7C%7C%0A      css.perspective !== 'none' %7C%7C%0A      css.contain === 'paint' %7C%7C%0A      %5B'transform', 'perspective'%5D.includes(css.willChange) %7C%7C%0A      (isFirefox
  && 
-(
 css.
@@ -1407,56 +1407,76 @@
 == '
-transform' %7C%7C
+filter') %7C%7C%0A      (isFirefox &&
  css.
-willChange === 'perspectiv
+filter && css.filter !== 'non
 e')
-)
 %0A   

Update getOffsetParent.js