/**
 * Returns the parent of a node.
 * Breaks through shadow roots.
 * Returns null if node has no parent.
 * @param {Node} node
 */
function getParent(node) {
  let parent = node.parentNode
  if (!parent) return null
  return parent.host ? parent.host : parent
}

/**
 * Returns an Iterator that walks the DOM tree upwards.
 * @param {Node} node
 */
export function createParentsIterator(node) {
  let curNode = node
  return {
    next: function() {
      curNode = getParent(curNode)
      return curNode ? { value: curNode } : { done: true }
    },
    [Symbol.iterator]: function() {
      return this
    }
  }
}