'use strict';

import { compareNodeNames, toElement, moveChildren, createElementNS, doc } from './util';
import specialElHandlers from './specialElHandlers';

var ELEMENT_NODE = 1;
var DOCUMENT_FRAGMENT_NODE = 11;
var TEXT_NODE = 3;
var COMMENT_NODE = 8;

function noop() {}

function defaultGetNodeKey(node) {
  if (node) {
    return (node.getAttribute && node.getAttribute('id')) || node.id;
  }
}

export default function morphdomFactory(morphAttrs) {

  return function morphdom(fromNode, toNode, options) {
    if (!options) {
      options = {};
    }

    if (typeof toNode === 'string') {
      if (fromNode.nodeName === '#document' || fromNode.nodeName === 'HTML' || fromNode.nodeName === 'BODY') {
        var toNodeHtml = toNode;
        toNode = doc.createElement('html');
        toNode.innerHTML = toNodeHtml;
      } else {
        toNode = toElement(toNode);
      }
    } else if (toNode.nodeType === DOCUMENT_FRAGMENT_NODE) {
      toNode = toNode.firstElementChild;
    }

    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 skipFromChildren = options.skipFromChildren || noop;
    var addChild = options.addChild || function(parent, child){ return parent.appendChild(child); };
    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 we find a duplicate #id node in cache, replace `el` with cache value
          // and morph it to the child node.
          if (unmatchedFromEl && compareNodeNames(curChild, unmatchedFromEl)) {
            curChild.parentNode.replaceChild(unmatchedFromEl, curChild);
            morphEl(unmatchedFromEl, curChild);
          } else {
            handleNodeAdded(curChild);
          }
        } else {
          // recursively call for curChild and it's children to see if we find something in
          // fromNodesLookup
          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
        var beforeUpdateResult = onBeforeElUpdated(fromEl, toEl);
        if (beforeUpdateResult === false) {
          return;
        } else if (beforeUpdateResult instanceof HTMLElement) {
          fromEl = beforeUpdateResult;
          // reindex the new fromEl in case it's not in the same
          // tree as the original fromEl
          // (Phoenix LiveView sometimes returns a cloned tree,
          //  but keyed lookups would still point to the original tree)
          indexTree(fromEl);
        }

        // 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 skipFrom = skipFromChildren(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 (!skipFrom && 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;
                      curFromNodeKey = getNodeKey(curFromNodeChild);
                    }
                  } 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)) {
          // MORPH
          if(!skipFrom){ addChild(fromEl, matchingFromEl); }
          morphEl(matchingFromEl, curToNodeChild);
        } else {
          var onBeforeNodeAddedResult = onBeforeNodeAdded(curToNodeChild);
          if (onBeforeNodeAddedResult !== false) {
            if (onBeforeNodeAddedResult) {
              curToNodeChild = onBeforeNodeAddedResult;
            }

            if (curToNodeChild.actualize) {
              curToNodeChild = curToNodeChild.actualize(fromEl.ownerDocument || doc);
            }
            addChild(fromEl, 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;
  };
}