text: 'use strict';
  
  var range; // Create a range object for efficently rendering strings to elements.
  var NS_XHTML = 'http://www.w3.org/1999/xhtml';
  
  var doc = typeof document === 'undefined' ? undefined : document;
  var HAS_TEMPLATE_SUPPORT = !!doc && 'content' in doc.createElement('template');
  var HAS_RANGE_SUPPORT = !!doc && doc.createRange && 'createContextualFragment' in doc.createRange();
  
  function createFragmentFromTemplate(str) {
      var template = doc.createElement('template');
      template.innerHTML = str;
      return template.content.childNodes[0];
  }
  
  function createFragmentFromRange(str) {
      if (!range) {
          range = doc.createRange();
          range.selectNode(doc.body);
      }
  
      var fragment = range.createContextualFragment(str);
      return fragment.childNodes[0];
  }
  
  function createFragmentFromWrap(str) {
      var fragment = doc.createElement('body');
      fragment.innerHTML = str;
      return fragment.childNodes[0];
  }
  
  /**
   * This is about the same
   * var html = new DOMParser().parseFromString(str, 'text/html');
   * return html.body.firstChild;
   *
   * @method toElement
   * @param {String} str
   */
  function toElement(str) {
      str = str.trim();
      if (HAS_TEMPLATE_SUPPORT) {
        // avoid restrictions on content for things like `<tr><th>Hi</th></tr>` which
        // createContextualFragment doesn't support
        // <template> support not available in IE
        return createFragmentFromTemplate(str);
      } else if (HAS_RANGE_SUPPORT) {
        return createFragmentFromRange(str);
      }
  
      return createFragmentFromWrap(str);
  }
  
  /**
   * Returns true if two node's names are the same.
   *
   * NOTE: We don't bother checking `namespaceURI` because you will never find two HTML elements with the same
   *       nodeName and different namespace URIs.
   *
   * @param {Element} a
   * @param {Element} b The target element
   * @return {boolean}
   */
  function compareNodeNames(fromEl, toEl) {
      var fromNodeName = fromEl.nodeName;
      var toNodeName = toEl.nodeName;
  
      if (fromNodeName === toNodeName) {
          return true;
      }
  
      if (toEl.actualize &&
          fromNodeName.charCodeAt(0) < 91 && /* from tag name is upper case */
          toNodeName.charCodeAt(0) > 90 /* target tag name is lower case */) {
          // If the target element is a virtual DOM node then we may need to normalize the tag name
          // before comparing. Normal HTML elements that are in the "http://www.w3.org/1999/xhtml"
          // are converted to upper case
          return fromNodeName === toNodeName.toUpperCase();
      } else {
          return false;
      }
  }
  
  /**
   * Create an element, optionally with a known namespace URI.
   *
   * @param {string} name the element name, e.g. 'div' or 'svg'
   * @param {string} [namespaceURI] the element's namespace URI, i.e. the value of
   * its `xmlns` attribute or its inferred namespace.
   *
   * @return {Element}
   */
  function createElementNS(name, namespaceURI) {
      return !namespaceURI || namespaceURI === NS_XHTML ?
          doc.createElement(name) :
          doc.createElementNS(namespaceURI, name);
  }
  
  /**
   * Copies the children of one DOM element to another DOM element
   */
  function moveChildren(fromEl, toEl) {
      var curChild = fromEl.firstChild;
      while (curChild) {
          var nextChild = curChild.nextSibling;
          toEl.appendChild(curChild);
          curChild = nextChild;
      }
      return toEl;
  }
  
  function syncBooleanAttrProp(fromEl, toEl, name) {
      if (fromEl[name] !== toEl[name]) {
          fromEl[name] = toEl[name];
          if (fromEl[name]) {
              fromEl.setAttribute(name, '');
          } else {
              fromEl.removeAttribute(name);
          }
      }
  }
  
  var specialElHandlers = {
      OPTION: function(fromEl, toEl) {
          var parentNode = fromEl.parentNode;
          if (parentNode) {
              var parentName = parentNode.nodeName.toUpperCase();
              if (parentName === 'OPTGROUP') {
                  parentNode = parentNode.parentNode;
                  parentName = parentNode && parentNode.nodeName.toUpperCase();
              }
              if (parentName === 'SELECT' && !parentNode.hasAttribute('multiple')) {
                  if (fromEl.hasAttribute('selected') && !toEl.selected) {
                      // Workaround for MS Edge bug where the 'selected' attribute can only be
                      // removed if set to a non-empty value:
                      // https://developer.microsoft.com/en-us/microsoft-edge/platform/issues/12087679/
                      fromEl.setAttribute('selected', 'selected');
                      fromEl.removeAttribute('selected');
                  }
                  // We have to reset select element's selectedIndex to -1, otherwise setting
                  // fromEl.selected using the syncBooleanAttrProp below has no effect.
                  // The correct selectedIndex will be set in the SELECT special handler below.
                  parentNode.selectedIndex = -1;
              }
          }
          syncBooleanAttrProp(fromEl, toEl, 'selected');
      },
      /**
       * The "value" attribute is special for the <input> element since it sets
       * the initial value. Changing the "value" attribute without changing the
       * "value" property will have no effect since it is only used to the set the
       * initial value.  Similar for the "checked" attribute, and "disabled".
       */
      INPUT: function(fromEl, toEl) {
          syncBooleanAttrProp(fromEl, toEl, 'checked');
          syncBooleanAttrProp(fromEl, toEl, 'disabled');
  
          if (fromEl.value !== toEl.value) {
              fromEl.value = toEl.value;
          }
  
          if (!toEl.hasAttribute('value')) {
              fromEl.removeAttribute('value');
          }
      },
  
      TEXTAREA: function(fromEl, toEl) {
          var newValue = toEl.value;
          if (fromEl.value !== newValue) {
              fromEl.value = newValue;
          }
  
          var firstChild = fromEl.firstChild;
          if (firstChild) {
              // Needed for IE. Apparently IE sets the placeholder as the
              // node value and vise versa. This ignores an empty update.
              var oldValue = firstChild.nodeValue;
  
              if (oldValue == newValue || (!newValue && oldValue == fromEl.placeholder)) {
                  return;
              }
  
              firstChild.nodeValue = newValue;
          }
      },
      SELECT: function(fromEl, toEl) {
          if (!toEl.hasAttribute('multiple')) {
              var selectedIndex = -1;
              var i = 0;
              // We have to loop through children of fromEl, not toEl since nodes can be moved
              // from toEl to fromEl directly when morphing.
              // At the time this special handler is invoked, all children have already been morphed
              // and appended to / removed from fromEl, so using fromEl here is safe and correct.
              var curChild = fromEl.firstChild;
              var optgroup;
              var nodeName;
              while(curChild) {
                  nodeName = curChild.nodeName && curChild.nodeName.toUpperCase();
                  if (nodeName === 'OPTGROUP') {
                      optgroup = curChild;
                      curChild = optgroup.firstChild;
                  } else {
                      if (nodeName === 'OPTION') {
                          if (curChild.hasAttribute('selected')) {
                              selectedIndex = i;
                              break;
                          }
                          i++;
                      }
                      curChild = curChild.nextSibling;
                      if (!curChild && optgroup) {
                          curChild = optgroup.nextSibling;
                          optgroup = null;
                      }
                  }
              }
  
              fromEl.selectedIndex = selectedIndex;
          }
      }
  };
  
  var ELEMENT_NODE = 1;
  var DOCUMENT_FRAGMENT_NODE = 11;
  var TEXT_NODE = 3;
  var COMMENT_NODE = 8;
  
  function noop() {}
  
  function defaultGetNodeKey(node) {
      return node.id;
  }
  
  function morphdomFactory(morphAttrs) {
  
      return function morphdom(fromNode, toNode, options) {
          if (!options) {
              options = {};
          }
  
          if (typeof toNode === 'string') {
              if (fromNode.nodeName === '#document' || fromNode.nodeName === 'HTML') {
                  var toNodeHtml = toNode;
                  toNode = doc.createElement('html');
                  toNode.innerHTML = toNodeHtml;
              } else {
                  toNode = toElement(toNode);
              }
          }
  
          var getNodeKey = options.getNodeKey || defaultGetNodeKey;
          var onBeforeNodeAdded = options.onBeforeNodeAdded || noop;
          var onNodeAdded = options.onNodeAdded || noop;
          var onBeforeElUpdated = options.onBeforeElUpdated || noop;
          var onElUpdated = options.onElUpdated || noop;
          var onBeforeNodeDiscarded = options.onBeforeNodeDiscarded || noop;
          var onNodeDiscarded = options.onNodeDiscarded || noop;
          var onBeforeElChildrenUpdated = options.onBeforeElChildrenUpdated || noop;
          var childrenOnly = options.childrenOnly === true;
  
          // This object is used as a lookup to quickly find all keyed elements in the original DOM tree.
          var fromNodesLookup = Object.create(null);
          var keyedRemovalList = [];
  
          function addKeyedRemoval(key) {
              keyedRemovalList.push(key);
          }
  
          function walkDiscardedChildNodes(node, skipKeyedNodes) {
              if (node.nodeType === ELEMENT_NODE) {
                  var curChild = node.firstChild;
                  while (curChild) {
  
                      var key = undefined;
  
                      if (skipKeyedNodes && (key = getNodeKey(curChild))) {
                          // If we are skipping keyed nodes then we add the key
                          // to a list so that it can be handled at the very end.
                          addKeyedRemoval(key);
                      } else {
                          // Only report the node as discarded if it is not keyed. We do this because
                          // at the end we loop through all keyed elements that were unmatched
                          // and then discard them in one final pass.
                          onNodeDiscarded(curChild);
                          if (curChild.firstChild) {
                              walkDiscardedChildNodes(curChild, skipKeyedNodes);
                          }
                      }
  
                      curChild = curChild.nextSibling;
                  }
              }
          }
  
          /**
           * Removes a DOM node out of the original DOM
           *
           * @param  {Node} node The node to remove
           * @param  {Node} parentNode The nodes parent
           * @param  {Boolean} skipKeyedNodes If true then elements with keys will be skipped and not discarded.
           * @return {undefined}
           */
          function removeNode(node, parentNode, skipKeyedNodes) {
              if (onBeforeNodeDiscarded(node) === false) {
                  return;
              }
  
              if (parentNode) {
                  parentNode.removeChild(node);
              }
  
              onNodeDiscarded(node);
              walkDiscardedChildNodes(node, skipKeyedNodes);
          }
  
          // // TreeWalker implementation is no faster, but keeping this around in case this changes in the future
          // function indexTree(root) {
          //     var treeWalker = document.createTreeWalker(
          //         root,
          //         NodeFilter.SHOW_ELEMENT);
          //
          //     var el;
          //     while((el = treeWalker.nextNode())) {
          //         var key = getNodeKey(el);
          //         if (key) {
          //             fromNodesLookup[key] = el;
          //         }
          //     }
          // }
  
          // // NodeIterator implementation is no faster, but keeping this around in case this changes in the future
          //
          // function indexTree(node) {
          //     var nodeIterator = document.createNodeIterator(node, NodeFilter.SHOW_ELEMENT);
          //     var el;
          //     while((el = nodeIterator.nextNode())) {
          //         var key = getNodeKey(el);
          //         if (key) {
          //             fromNodesLookup[key] = el;
          //         }
          //     }
          // }
  
          function indexTree(node) {
              if (node.nodeType === ELEMENT_NODE || node.nodeType === DOCUMENT_FRAGMENT_NODE) {
                  var curChild = node.firstChild;
                  while (curChild) {
                      var key = getNodeKey(curChild);
                      if (key) {
                          fromNodesLookup[key] = curChild;
                      }
  
                      // Walk recursively
                      indexTree(curChild);
  
                      curChild = curChild.nextSibling;
                  }
              }
          }
  
          indexTree(fromNode);
  
          function handleNodeAdded(el) {
              onNodeAdded(el);
  
              var curChild = el.firstChild;
              while (curChild) {
                  var nextSibling = curChild.nextSibling;
  
                  var key = getNodeKey(curChild);
                  if (key) {
                      var unmatchedFromEl = fromNodesLookup[key];
                      if (unmatchedFromEl && compareNodeNames(curChild, unmatchedFromEl)) {
                          curChild.parentNode.replaceChild(unmatchedFromEl, curChild);
                          morphEl(unmatchedFromEl, curChild);
                      }
                  }
  
                  handleNodeAdded(curChild);
                  curChild = nextSibling;
              }
          }
  
          function cleanupFromEl(fromEl, curFromNodeChild, curFromNodeKey) {
              // We have processed all of the "to nodes". If curFromNodeChild is
              // non-null then we still have some from nodes left over that need
              // to be removed
              while (curFromNodeChild) {
                  var fromNextSibling = curFromNodeChild.nextSibling;
                  if ((curFromNodeKey = getNodeKey(curFromNodeChild))) {
                      // Since the node is keyed it might be matched up later so we defer
                      // the actual removal to later
                      addKeyedRemoval(curFromNodeKey);
                  } else {
                      // NOTE: we skip nested keyed nodes from being removed since there is
                      //       still a chance they will be matched up later
                      removeNode(curFromNodeChild, fromEl, true /* skip keyed nodes */);
                  }
                  curFromNodeChild = fromNextSibling;
              }
          }
  
          function morphEl(fromEl, toEl, childrenOnly) {
              var toElKey = getNodeKey(toEl);
  
              if (toElKey) {
                  // If an element with an ID is being morphed then it will be in the final
                  // DOM so clear it out of the saved elements collection
                  delete fromNodesLookup[toElKey];
              }
  
              if (!childrenOnly) {
                  // optional
                  if (onBeforeElUpdated(fromEl, toEl) === false) {
                      return;
                  }
  
                  // update attributes on original DOM element first
                  morphAttrs(fromEl, toEl);
                  // optional
                  onElUpdated(fromEl);
  
                  if (onBeforeElChildrenUpdated(fromEl, toEl) === false) {
                      return;
                  }
              }
  
              if (fromEl.nodeName !== 'TEXTAREA') {
                morphChildren(fromEl, toEl);
              } else {
                specialElHandlers.TEXTAREA(fromEl, toEl);
              }
          }
  
          function morphChildren(fromEl, toEl) {
              var curToNodeChild = toEl.firstChild;
              var curFromNodeChild = fromEl.firstChild;
              var curToNodeKey;
              var curFromNodeKey;
  
              var fromNextSibling;
              var toNextSibling;
              var matchingFromEl;
  
              // walk the children
              outer: while (curToNodeChild) {
                  toNextSibling = curToNodeChild.nextSibling;
                  curToNodeKey = getNodeKey(curToNodeChild);
  
                  // walk the fromNode children all the way through
                  while (curFromNodeChild) {
                      fromNextSibling = curFromNodeChild.nextSibling;
  
                      if (curToNodeChild.isSameNode && curToNodeChild.isSameNode(curFromNodeChild)) {
                          curToNodeChild = toNextSibling;
                          curFromNodeChild = fromNextSibling;
                          continue outer;
                      }
  
                      curFromNodeKey = getNodeKey(curFromNodeChild);
  
                      var curFromNodeType = curFromNodeChild.nodeType;
  
                      // this means if the curFromNodeChild doesnt have a match with the curToNodeChild
                      var isCompatible = undefined;
  
                      if (curFromNodeType === curToNodeChild.nodeType) {
                          if (curFromNodeType === ELEMENT_NODE) {
                              // Both nodes being compared are Element nodes
  
                              if (curToNodeKey) {
                                  // The target node has a key so we want to match it up with the correct element
                                  // in the original DOM tree
                                  if (curToNodeKey !== curFromNodeKey) {
                                      // The current element in the original DOM tree does not have a matching key so
                                      // let's check our lookup to see if there is a matching element in the original
                                      // DOM tree
                                      if ((matchingFromEl = fromNodesLookup[curToNodeKey])) {
                                          if (fromNextSibling === matchingFromEl) {
                                              // Special case for single element removals. To avoid removing the original
                                              // DOM node out of the tree (since that can break CSS transitions, etc.),
                                              // we will instead discard the current node and wait until the next
                                              // iteration to properly match up the keyed target element with its matching
                                              // element in the original tree
                                              isCompatible = false;
                                          } else {
                                              // We found a matching keyed element somewhere in the original DOM tree.
                                              // Let's move the original DOM node into the current position and morph
                                              // it.
  
                                              // NOTE: We use insertBefore instead of replaceChild because we want to go through
                                              // the `removeNode()` function for the node that is being discarded so that
                                              // all lifecycle hooks are correctly invoked
                                              fromEl.insertBefore(matchingFromEl, curFromNodeChild);
  
                                              // fromNextSibling = curFromNodeChild.nextSibling;
  
                                              if (curFromNodeKey) {
                                                  // Since the node is keyed it might be matched up later so we defer
                                                  // the actual removal to later
                                                  addKeyedRemoval(curFromNodeKey);
                                              } else {
                                                  // NOTE: we skip nested keyed nodes from being removed since there is
                                                  //       still a chance they will be matched up later
                                                  removeNode(curFromNodeChild, fromEl, true /* skip keyed nodes */);
                                              }
  
                                              curFromNodeChild = matchingFromEl;
                                          }
                                      } else {
                                          // The nodes are not compatible since the "to" node has a key and there
                                          // is no matching keyed node in the source tree
                                          isCompatible = false;
                                      }
                                  }
                              } else if (curFromNodeKey) {
                                  // The original has a key
                                  isCompatible = false;
                              }
  
                              isCompatible = isCompatible !== false && compareNodeNames(curFromNodeChild, curToNodeChild);
                              if (isCompatible) {
                                  // We found compatible DOM elements so transform
                                  // the current "from" node to match the current
                                  // target DOM node.
                                  // MORPH
                                  morphEl(curFromNodeChild, curToNodeChild);
                              }
  
                          } else if (curFromNodeType === TEXT_NODE || curFromNodeType == COMMENT_NODE) {
                              // Both nodes being compared are Text or Comment nodes
                              isCompatible = true;
                              // Simply update nodeValue on the original node to
                              // change the text value
                              if (curFromNodeChild.nodeValue !== curToNodeChild.nodeValue) {
                                  curFromNodeChild.nodeValue = curToNodeChild.nodeValue;
                              }
  
                          }
                      }
  
                      if (isCompatible) {
                          // Advance both the "to" child and the "from" child since we found a match
                          // Nothing else to do as we already recursively called morphChildren above
                          curToNodeChild = toNextSibling;
                          curFromNodeChild = fromNextSibling;
                          continue outer;
                      }
  
                      // No compatible match so remove the old node from the DOM and continue trying to find a
                      // match in the original DOM. However, we only do this if the from node is not keyed
                      // since it is possible that a keyed node might match up with a node somewhere else in the
                      // target tree and we don't want to discard it just yet since it still might find a
                      // home in the final DOM tree. After everything is done we will remove any keyed nodes
                      // that didn't find a home
                      if (curFromNodeKey) {
                          // Since the node is keyed it might be matched up later so we defer
                          // the actual removal to later
                          addKeyedRemoval(curFromNodeKey);
                      } else {
                          // NOTE: we skip nested keyed nodes from being removed since there is
                          //       still a chance they will be matched up later
                          removeNode(curFromNodeChild, fromEl, true /* skip keyed nodes */);
                      }
  
                      curFromNodeChild = fromNextSibling;
                  } // END: while(curFromNodeChild) {}
  
                  // If we got this far then we did not find a candidate match for
                  // our "to node" and we exhausted all of the children "from"
                  // nodes. Therefore, we will just append the current "to" node
                  // to the end
                  if (curToNodeKey && (matchingFromEl = fromNodesLookup[curToNodeKey]) && compareNodeNames(matchingFromEl, curToNodeChild)) {
                      fromEl.appendChild(matchingFromEl);
                      // MORPH
                      morphEl(matchingFromEl, curToNodeChild);
                  } else {
                      var onBeforeNodeAddedResult = onBeforeNodeAdded(curToNodeChild);
                      if (onBeforeNodeAddedResult !== false) {
                          if (onBeforeNodeAddedResult) {
                              curToNodeChild = onBeforeNodeAddedResult;
                          }
  
                          if (curToNodeChild.actualize) {
                              curToNodeChild = curToNodeChild.actualize(fromEl.ownerDocument || doc);
                          }
                          fromEl.appendChild(curToNodeChild);
                          handleNodeAdded(curToNodeChild);
                      }
                  }
  
                  curToNodeChild = toNextSibling;
                  curFromNodeChild = fromNextSibling;
              }
  
              cleanupFromEl(fromEl, curFromNodeChild, curFromNodeKey);
  
              var specialElHandler = specialElHandlers[fromEl.nodeName];
              if (specialElHandler) {
                  specialElHandler(fromEl, toEl);
              }
          } // END: morphChildren(...)
  
          var morphedNode = fromNode;
          var morphedNodeType = morphedNode.nodeType;
          var toNodeType = toNode.nodeType;
  
          if (!childrenOnly) {
              // Handle the case where we are given two DOM nodes that are not
              // compatible (e.g. <div> --> <span> or <div> --> TEXT)
              if (morphedNodeType === ELEMENT_NODE) {
                  if (toNodeType === ELEMENT_NODE) {
                      if (!compareNodeNames(fromNode, toNode)) {
                          onNodeDiscarded(fromNode);
                          morphedNode = moveChildren(fromNode, createElementNS(toNode.nodeName, toNode.namespaceURI));
                      }
                  } else {
                      // Going from an element node to a text node
                      morphedNode = toNode;
                  }
              } else if (morphedNodeType === TEXT_NODE || morphedNodeType === COMMENT_NODE) { // Text or comment node
                  if (toNodeType === morphedNodeType) {
                      if (morphedNode.nodeValue !== toNode.nodeValue) {
                          morphedNode.nodeValue = toNode.nodeValue;
                      }
  
                      return morphedNode;
                  } else {
                      // Text node to something else
                      morphedNode = toNode;
                  }
              }
          }
  
          if (morphedNode === toNode) {
              // The "to node" was not compatible with the "from node" so we had to
              // toss out the "from node" and use the "to node"
              onNodeDiscarded(fromNode);
          } else {
              if (toNode.isSameNode && toNode.isSameNode(morphedNode)) {
                  return;
              }
  
              morphEl(morphedNode, toNode, childrenOnly);
  
              // We now need to loop over any keyed nodes that might need to be
              // removed. We only do the removal if we know that the keyed node
              // never found a match. When a keyed node is matched up we remove
              // it out of fromNodesLookup and we use fromNodesLookup to determine
              // if a keyed node has been matched up or not
              if (keyedRemovalList) {
                  for (var i=0, len=keyedRemovalList.length; i<len; i++) {
                      var elToRemove = fromNodesLookup[keyedRemovalList[i]];
                      if (elToRemove) {
                          removeNode(elToRemove, elToRemove.parentNode, false);
                      }
                  }
              }
          }
  
          if (!childrenOnly && morphedNode !== fromNode && fromNode.parentNode) {
              if (morphedNode.actualize) {
                  morphedNode = morphedNode.actualize(fromNode.ownerDocument || doc);
              }
              // If we had to swap out the from node with a new node because the old
              // node was not compatible with the target node then we need to
              // replace the old DOM node in the original DOM tree. This is only
              // possible if the original DOM node was part of a DOM tree which
              // we know is the case if it has a parent node.
              fromNode.parentNode.replaceChild(morphedNode, fromNode);
          }
  
          return morphedNode;
      };
  }
  
  module.exports = morphdomFactory;
  