Added node_modules for the updating to work properly.

4 files changed, 972 insertions, 0 deletions

diff --git a/node_modules/symbol-tree/lib/SymbolTree.js b/node_modules/symbol-tree/lib/SymbolTree.js
new file mode 100644
index 0000000..b2b8f2e
--- /dev/null
+++ b/node_modules/symbol-tree/lib/SymbolTree.js
@@ -0,0 +1,838 @@
+'use strict';
+
+/**
+ * @module symbol-tree
+ * @author Joris van der Wel <joris@jorisvanderwel.com>
+ */
+
+const SymbolTreeNode = require('./SymbolTreeNode');
+const TreePosition = require('./TreePosition');
+const TreeIterator = require('./TreeIterator');
+
+function returnTrue() {
+        return true;
+}
+
+function reverseArrayIndex(array, reverseIndex) {
+        return array[array.length - 1 - reverseIndex]; // no need to check `index >= 0`
+}
+
+class SymbolTree {
+
+        /**
+         * @constructor
+         * @alias module:symbol-tree
+         * @param {string} [description='SymbolTree data'] Description used for the Symbol
+         */
+        constructor(description) {
+                this.symbol = Symbol(description || 'SymbolTree data');
+        }
+
+        /**
+         * You can use this function to (optionally) initialize an object right after its creation,
+         * to take advantage of V8's fast properties. Also useful if you would like to
+         * freeze your object.
+         *
+         * `O(1)`
+         *
+         * @method
+         * @alias module:symbol-tree#initialize
+         * @param {Object} object
+         * @return {Object} object
+         */
+        initialize(object) {
+                this._node(object);
+
+                return object;
+        }
+
+        _node(object) {
+                if (!object) {
+                        return null;
+                }
+
+                const node = object[this.symbol];
+
+                if (node) {
+                        return node;
+                }
+
+                return (object[this.symbol] = new SymbolTreeNode());
+        }
+
+        /**
+         * Returns `true` if the object has any children. Otherwise it returns `false`.
+         *
+         * * `O(1)`
+         *
+         * @method hasChildren
+         * @memberOf module:symbol-tree#
+         * @param {Object} object
+         * @return {Boolean}
+         */
+        hasChildren(object) {
+                return this._node(object).hasChildren;
+        }
+
+        /**
+         * Returns the first child of the given object.
+         *
+         * * `O(1)`
+         *
+         * @method firstChild
+         * @memberOf module:symbol-tree#
+         * @param {Object} object
+         * @return {Object}
+         */
+        firstChild(object) {
+                return this._node(object).firstChild;
+        }
+
+        /**
+         * Returns the last child of the given object.
+         *
+         * * `O(1)`
+         *
+         * @method lastChild
+         * @memberOf module:symbol-tree#
+         * @param {Object} object
+         * @return {Object}
+         */
+        lastChild(object) {
+                return this._node(object).lastChild;
+        }
+
+        /**
+         * Returns the previous sibling of the given object.
+         *
+         * * `O(1)`
+         *
+         * @method previousSibling
+         * @memberOf module:symbol-tree#
+         * @param {Object} object
+         * @return {Object}
+         */
+        previousSibling(object) {
+                return this._node(object).previousSibling;
+        }
+
+        /**
+         * Returns the next sibling of the given object.
+         *
+         * * `O(1)`
+         *
+         * @method nextSibling
+         * @memberOf module:symbol-tree#
+         * @param {Object} object
+         * @return {Object}
+         */
+        nextSibling(object) {
+                return this._node(object).nextSibling;
+        }
+
+        /**
+         * Return the parent of the given object.
+         *
+         * * `O(1)`
+         *
+         * @method parent
+         * @memberOf module:symbol-tree#
+         * @param {Object} object
+         * @return {Object}
+         */
+        parent(object) {
+                return this._node(object).parent;
+        }
+
+        /**
+         * Find the inclusive descendant that is last in tree order of the given object.
+         *
+         * * `O(n)` (worst case) where `n` is the depth of the subtree of `object`
+         *
+         * @method lastInclusiveDescendant
+         * @memberOf module:symbol-tree#
+         * @param {Object} object
+         * @return {Object}
+         */
+        lastInclusiveDescendant(object) {
+                let lastChild;
+                let current = object;
+
+                while ((lastChild = this._node(current).lastChild)) {
+                        current = lastChild;
+                }
+
+                return current;
+        }
+
+        /**
+         * Find the preceding object (A) of the given object (B).
+         * An object A is preceding an object B if A and B are in the same tree
+         * and A comes before B in tree order.
+         *
+         * * `O(n)` (worst case)
+         * * `O(1)` (amortized when walking the entire tree)
+         *
+         * @method preceding
+         * @memberOf module:symbol-tree#
+         * @param {Object} object
+         * @param {Object} [options]
+         * @param {Object} [options.root] If set, `root` must be an inclusive ancestor
+         *        of the return value (or else null is returned). This check _assumes_
+         *        that `root` is also an inclusive ancestor of the given `object`
+         * @return {?Object}
+         */
+        preceding(object, options) {
+                const treeRoot = options && options.root;
+
+                if (object === treeRoot) {
+                        return null;
+                }
+
+                const previousSibling = this._node(object).previousSibling;
+
+                if (previousSibling) {
+                        return this.lastInclusiveDescendant(previousSibling);
+                }
+
+                // if there is no previous sibling return the parent (might be null)
+                return this._node(object).parent;
+        }
+
+        /**
+         * Find the following object (A) of the given object (B).
+         * An object A is following an object B if A and B are in the same tree
+         * and A comes after B in tree order.
+         *
+         * * `O(n)` (worst case) where `n` is the amount of objects in the entire tree
+         * * `O(1)` (amortized when walking the entire tree)
+         *
+         * @method following
+         * @memberOf module:symbol-tree#
+         * @param {!Object} object
+         * @param {Object} [options]
+         * @param {Object} [options.root] If set, `root` must be an inclusive ancestor
+         *        of the return value (or else null is returned). This check _assumes_
+         *        that `root` is also an inclusive ancestor of the given `object`
+         * @param {Boolean} [options.skipChildren=false] If set, ignore the children of `object`
+         * @return {?Object}
+         */
+        following(object, options) {
+                const treeRoot = options && options.root;
+                const skipChildren = options && options.skipChildren;
+
+                const firstChild = !skipChildren && this._node(object).firstChild;
+
+                if (firstChild) {
+                        return firstChild;
+                }
+
+                let current = object;
+
+                do {
+                        if (current === treeRoot) {
+                                return null;
+                        }
+
+                        const nextSibling = this._node(current).nextSibling;
+
+                        if (nextSibling) {
+                                return nextSibling;
+                        }
+
+                        current = this._node(current).parent;
+                } while (current);
+
+                return null;
+        }
+
+        /**
+         * Append all children of the given object to an array.
+         *
+         * * `O(n)` where `n` is the amount of children of the given `parent`
+         *
+         * @method childrenToArray
+         * @memberOf module:symbol-tree#
+         * @param {Object} parent
+         * @param {Object} [options]
+         * @param {Object[]} [options.array=[]]
+         * @param {Function} [options.filter] Function to test each object before it is added to the array.
+         *                            Invoked with arguments (object). Should return `true` if an object
+         *                            is to be included.
+         * @param {*} [options.thisArg] Value to use as `this` when executing `filter`.
+         * @return {Object[]}
+         */
+        childrenToArray(parent, options) {
+                const array   = (options && options.array) || [];
+                const filter  = (options && options.filter) || returnTrue;
+                const thisArg = (options && options.thisArg) || undefined;
+
+                const parentNode = this._node(parent);
+                let object = parentNode.firstChild;
+                let index = 0;
+
+                while (object) {
+                        const node = this._node(object);
+                        node.setCachedIndex(parentNode, index);
+
+                        if (filter.call(thisArg, object)) {
+                                array.push(object);
+                        }
+
+                        object = node.nextSibling;
+                        ++index;
+                }
+
+                return array;
+        }
+
+        /**
+         * Append all inclusive ancestors of the given object to an array.
+         *
+         * * `O(n)` where `n` is the amount of ancestors of the given `object`
+         *
+         * @method ancestorsToArray
+         * @memberOf module:symbol-tree#
+         * @param {Object} object
+         * @param {Object} [options]
+         * @param {Object[]} [options.array=[]]
+         * @param {Function} [options.filter] Function to test each object before it is added to the array.
+         *                            Invoked with arguments (object). Should return `true` if an object
+         *                            is to be included.
+         * @param {*} [options.thisArg] Value to use as `this` when executing `filter`.
+         * @return {Object[]}
+         */
+        ancestorsToArray(object, options) {
+                const array   = (options && options.array) || [];
+                const filter  = (options && options.filter) || returnTrue;
+                const thisArg = (options && options.thisArg) || undefined;
+
+                let ancestor = object;
+
+                while (ancestor) {
+                        if (filter.call(thisArg, ancestor)) {
+                                array.push(ancestor);
+                        }
+                        ancestor = this._node(ancestor).parent;
+                }
+
+                return array;
+        }
+
+        /**
+         * Append all descendants of the given object to an array (in tree order).
+         *
+         * * `O(n)` where `n` is the amount of objects in the sub-tree of the given `object`
+         *
+         * @method treeToArray
+         * @memberOf module:symbol-tree#
+         * @param {Object} root
+         * @param {Object} [options]
+         * @param {Object[]} [options.array=[]]
+         * @param {Function} [options.filter] Function to test each object before it is added to the array.
+         *                            Invoked with arguments (object). Should return `true` if an object
+         *                            is to be included.
+         * @param {*} [options.thisArg] Value to use as `this` when executing `filter`.
+         * @return {Object[]}
+         */
+        treeToArray(root, options) {
+                const array   = (options && options.array) || [];
+                const filter  = (options && options.filter) || returnTrue;
+                const thisArg = (options && options.thisArg) || undefined;
+
+                let object = root;
+
+                while (object) {
+                        if (filter.call(thisArg, object)) {
+                                array.push(object);
+                        }
+                        object = this.following(object, {root: root});
+                }
+
+                return array;
+        }
+
+        /**
+         * Iterate over all children of the given object
+         *
+         * * `O(1)` for a single iteration
+         *
+         * @method childrenIterator
+         * @memberOf module:symbol-tree#
+         * @param {Object} parent
+         * @param {Object} [options]
+         * @param {Boolean} [options.reverse=false]
+         * @return {Object} An iterable iterator (ES6)
+         */
+        childrenIterator(parent, options) {
+                const reverse = options && options.reverse;
+                const parentNode = this._node(parent);
+
+                return new TreeIterator(
+                        this,
+                        parent,
+                        reverse ? parentNode.lastChild : parentNode.firstChild,
+                        reverse ? TreeIterator.PREV : TreeIterator.NEXT
+                );
+        }
+
+        /**
+         * Iterate over all the previous siblings of the given object. (in reverse tree order)
+         *
+         * * `O(1)` for a single iteration
+         *
+         * @method previousSiblingsIterator
+         * @memberOf module:symbol-tree#
+         * @param {Object} object
+         * @return {Object} An iterable iterator (ES6)
+         */
+        previousSiblingsIterator(object) {
+                return new TreeIterator(
+                        this,
+                        object,
+                        this._node(object).previousSibling,
+                        TreeIterator.PREV
+                );
+        }
+
+        /**
+         * Iterate over all the next siblings of the given object. (in tree order)
+         *
+         * * `O(1)` for a single iteration
+         *
+         * @method nextSiblingsIterator
+         * @memberOf module:symbol-tree#
+         * @param {Object} object
+         * @return {Object} An iterable iterator (ES6)
+         */
+        nextSiblingsIterator(object) {
+                return new TreeIterator(
+                        this,
+                        object,
+                        this._node(object).nextSibling,
+                        TreeIterator.NEXT
+                );
+        }
+
+        /**
+         * Iterate over all inclusive ancestors of the given object
+         *
+         * * `O(1)` for a single iteration
+         *
+         * @method ancestorsIterator
+         * @memberOf module:symbol-tree#
+         * @param {Object} object
+         * @return {Object} An iterable iterator (ES6)
+         */
+        ancestorsIterator(object) {
+                return new TreeIterator(
+                        this,
+                        object,
+                        object,
+                        TreeIterator.PARENT
+                );
+        }
+
+        /**
+         * Iterate over all descendants of the given object (in tree order).
+         *
+         * Where `n` is the amount of objects in the sub-tree of the given `root`:
+         *
+         * * `O(n)` (worst case for a single iteration)
+         * * `O(n)` (amortized, when completing the iterator)
+         *
+         * @method treeIterator
+         * @memberOf module:symbol-tree#
+         * @param {Object} root
+         * @param {Object} options
+         * @param {Boolean} [options.reverse=false]
+         * @return {Object} An iterable iterator (ES6)
+         */
+        treeIterator(root, options) {
+                const reverse = options && options.reverse;
+
+                return new TreeIterator(
+                        this,
+                        root,
+                        reverse ? this.lastInclusiveDescendant(root) : root,
+                        reverse ? TreeIterator.PRECEDING : TreeIterator.FOLLOWING
+                );
+        }
+
+        /**
+         * Find the index of the given object (the number of preceding siblings).
+         *
+         * * `O(n)` where `n` is the amount of preceding siblings
+         * * `O(1)` (amortized, if the tree is not modified)
+         *
+         * @method index
+         * @memberOf module:symbol-tree#
+         * @param {Object} child
+         * @return {Number} The number of preceding siblings, or -1 if the object has no parent
+         */
+        index(child) {
+                const childNode = this._node(child);
+                const parentNode = this._node(childNode.parent);
+
+                if (!parentNode) {
+                        // In principal, you could also find out the number of preceding siblings
+                        // for objects that do not have a parent. This method limits itself only to
+                        // objects that have a parent because that lets us optimize more.
+                        return -1;
+                }
+
+                let currentIndex = childNode.getCachedIndex(parentNode);
+
+                if (currentIndex >= 0) {
+                        return currentIndex;
+                }
+
+                currentIndex = 0;
+                let object = parentNode.firstChild;
+
+                if (parentNode.childIndexCachedUpTo) {
+                        const cachedUpToNode = this._node(parentNode.childIndexCachedUpTo);
+                        object = cachedUpToNode.nextSibling;
+                        currentIndex = cachedUpToNode.getCachedIndex(parentNode) + 1;
+                }
+
+                while (object) {
+                        const node = this._node(object);
+                        node.setCachedIndex(parentNode, currentIndex);
+
+                        if (object === child) {
+                                break;
+                        }
+
+                        ++currentIndex;
+                        object = node.nextSibling;
+                }
+
+                parentNode.childIndexCachedUpTo = child;
+
+                return currentIndex;
+        }
+
+        /**
+         * Calculate the number of children.
+         *
+         * * `O(n)` where `n` is the amount of children
+         * * `O(1)` (amortized, if the tree is not modified)
+         *
+         * @method childrenCount
+         * @memberOf module:symbol-tree#
+         * @param {Object} parent
+         * @return {Number}
+         */
+        childrenCount(parent) {
+                const parentNode = this._node(parent);
+
+                if (!parentNode.lastChild) {
+                        return 0;
+                }
+
+                return this.index(parentNode.lastChild) + 1;
+        }
+
+        /**
+         * Compare the position of an object relative to another object. A bit set is returned:
+         *
+         * <ul>
+         *     <li>DISCONNECTED : 1</li>
+         *     <li>PRECEDING : 2</li>
+         *     <li>FOLLOWING : 4</li>
+         *     <li>CONTAINS : 8</li>
+         *     <li>CONTAINED_BY : 16</li>
+         * </ul>
+         *
+         * The semantics are the same as compareDocumentPosition in DOM, with the exception that
+         * DISCONNECTED never occurs with any other bit.
+         *
+         * where `n` and `m` are the amount of ancestors of `left` and `right`;
+         * where `o` is the amount of children of the lowest common ancestor of `left` and `right`:
+         *
+         * * `O(n + m + o)` (worst case)
+         * * `O(n + m)` (amortized, if the tree is not modified)
+         *
+         * @method compareTreePosition
+         * @memberOf module:symbol-tree#
+         * @param {Object} left
+         * @param {Object} right
+         * @return {Number}
+         */
+        compareTreePosition(left, right) {
+                // In DOM terms:
+                // left = reference / context object
+                // right = other
+
+                if (left === right) {
+                        return 0;
+                }
+
+                /* jshint -W016 */
+
+                const leftAncestors = []; { // inclusive
+                        let leftAncestor = left;
+
+                        while (leftAncestor) {
+                                if (leftAncestor === right) {
+                                        return TreePosition.CONTAINS | TreePosition.PRECEDING;
+                                        // other is ancestor of reference
+                                }
+
+                                leftAncestors.push(leftAncestor);
+                                leftAncestor = this.parent(leftAncestor);
+                        }
+                }
+
+
+                const rightAncestors = []; {
+                        let rightAncestor = right;
+
+                        while (rightAncestor) {
+                                if (rightAncestor === left) {
+                                        return TreePosition.CONTAINED_BY | TreePosition.FOLLOWING;
+                                }
+
+                                rightAncestors.push(rightAncestor);
+                                rightAncestor = this.parent(rightAncestor);
+                        }
+                }
+
+
+                const root = reverseArrayIndex(leftAncestors, 0);
+
+                if (!root || root !== reverseArrayIndex(rightAncestors, 0)) {
+                        // note: unlike DOM, preceding / following is not set here
+                        return TreePosition.DISCONNECTED;
+                }
+
+                // find the lowest common ancestor
+                let commonAncestorIndex = 0;
+                const ancestorsMinLength = Math.min(leftAncestors.length, rightAncestors.length);
+
+                for (let i = 0; i < ancestorsMinLength; ++i) {
+                        const leftAncestor  = reverseArrayIndex(leftAncestors, i);
+                        const rightAncestor = reverseArrayIndex(rightAncestors, i);
+
+                        if (leftAncestor !== rightAncestor) {
+                                break;
+                        }
+
+                        commonAncestorIndex = i;
+                }
+
+                // indexes within the common ancestor
+                const leftIndex  = this.index(reverseArrayIndex(leftAncestors, commonAncestorIndex + 1));
+                const rightIndex = this.index(reverseArrayIndex(rightAncestors, commonAncestorIndex + 1));
+
+                return rightIndex < leftIndex
+                        ? TreePosition.PRECEDING
+                        : TreePosition.FOLLOWING;
+        }
+
+        /**
+         * Remove the object from this tree.
+         * Has no effect if already removed.
+         *
+         * * `O(1)`
+         *
+         * @method remove
+         * @memberOf module:symbol-tree#
+         * @param {Object} removeObject
+         * @return {Object} removeObject
+         */
+        remove(removeObject) {
+                const removeNode = this._node(removeObject);
+                const parentNode = this._node(removeNode.parent);
+                const prevNode = this._node(removeNode.previousSibling);
+                const nextNode = this._node(removeNode.nextSibling);
+
+                if (parentNode) {
+                        if (parentNode.firstChild === removeObject) {
+                                parentNode.firstChild = removeNode.nextSibling;
+                        }
+
+                        if (parentNode.lastChild === removeObject) {
+                                parentNode.lastChild = removeNode.previousSibling;
+                        }
+                }
+
+                if (prevNode) {
+                        prevNode.nextSibling = removeNode.nextSibling;
+                }
+
+                if (nextNode) {
+                        nextNode.previousSibling = removeNode.previousSibling;
+                }
+
+                removeNode.parent = null;
+                removeNode.previousSibling = null;
+                removeNode.nextSibling = null;
+                removeNode.cachedIndex = -1;
+                removeNode.cachedIndexVersion = NaN;
+
+                if (parentNode) {
+                        parentNode.childrenChanged();
+                }
+
+                return removeObject;
+        }
+
+        /**
+         * Insert the given object before the reference object.
+         * `newObject` is now the previous sibling of `referenceObject`.
+         *
+         * * `O(1)`
+         *
+         * @method insertBefore
+         * @memberOf module:symbol-tree#
+         * @param {Object} referenceObject
+         * @param {Object} newObject
+         * @throws {Error} If the newObject is already present in this SymbolTree
+         * @return {Object} newObject
+         */
+        insertBefore(referenceObject, newObject) {
+                const referenceNode = this._node(referenceObject);
+                const prevNode = this._node(referenceNode.previousSibling);
+                const newNode = this._node(newObject);
+                const parentNode = this._node(referenceNode.parent);
+
+                if (newNode.isAttached) {
+                        throw Error('Given object is already present in this SymbolTree, remove it first');
+                }
+
+                newNode.parent = referenceNode.parent;
+                newNode.previousSibling = referenceNode.previousSibling;
+                newNode.nextSibling = referenceObject;
+                referenceNode.previousSibling = newObject;
+
+                if (prevNode) {
+                        prevNode.nextSibling = newObject;
+                }
+
+                if (parentNode && parentNode.firstChild === referenceObject) {
+                        parentNode.firstChild = newObject;
+                }
+
+                if (parentNode) {
+                        parentNode.childrenChanged();
+                }
+
+                return newObject;
+        }
+
+        /**
+         * Insert the given object after the reference object.
+         * `newObject` is now the next sibling of `referenceObject`.
+         *
+         * * `O(1)`
+         *
+         * @method insertAfter
+         * @memberOf module:symbol-tree#
+         * @param {Object} referenceObject
+         * @param {Object} newObject
+         * @throws {Error} If the newObject is already present in this SymbolTree
+         * @return {Object} newObject
+         */
+        insertAfter(referenceObject, newObject) {
+                const referenceNode = this._node(referenceObject);
+                const nextNode = this._node(referenceNode.nextSibling);
+                const newNode = this._node(newObject);
+                const parentNode = this._node(referenceNode.parent);
+
+                if (newNode.isAttached) {
+                        throw Error('Given object is already present in this SymbolTree, remove it first');
+                }
+
+                newNode.parent = referenceNode.parent;
+                newNode.previousSibling = referenceObject;
+                newNode.nextSibling = referenceNode.nextSibling;
+                referenceNode.nextSibling = newObject;
+
+                if (nextNode) {
+                        nextNode.previousSibling = newObject;
+                }
+
+                if (parentNode && parentNode.lastChild === referenceObject) {
+                        parentNode.lastChild = newObject;
+                }
+
+                if (parentNode) {
+                        parentNode.childrenChanged();
+                }
+
+                return newObject;
+        }
+
+        /**
+         * Insert the given object as the first child of the given reference object.
+         * `newObject` is now the first child of `referenceObject`.
+         *
+         * * `O(1)`
+         *
+         * @method prependChild
+         * @memberOf module:symbol-tree#
+         * @param {Object} referenceObject
+         * @param {Object} newObject
+         * @throws {Error} If the newObject is already present in this SymbolTree
+         * @return {Object} newObject
+         */
+        prependChild(referenceObject, newObject) {
+                const referenceNode = this._node(referenceObject);
+                const newNode = this._node(newObject);
+
+                if (newNode.isAttached) {
+                        throw Error('Given object is already present in this SymbolTree, remove it first');
+                }
+
+                if (referenceNode.hasChildren) {
+                        this.insertBefore(referenceNode.firstChild, newObject);
+                }
+                else {
+                        newNode.parent = referenceObject;
+                        referenceNode.firstChild = newObject;
+                        referenceNode.lastChild = newObject;
+                        referenceNode.childrenChanged();
+                }
+
+                return newObject;
+        }
+
+        /**
+         * Insert the given object as the last child of the given reference object.
+         * `newObject` is now the last child of `referenceObject`.
+         *
+         * * `O(1)`
+         *
+         * @method appendChild
+         * @memberOf module:symbol-tree#
+         * @param {Object} referenceObject
+         * @param {Object} newObject
+         * @throws {Error} If the newObject is already present in this SymbolTree
+         * @return {Object} newObject
+         */
+        appendChild(referenceObject, newObject) {
+                const referenceNode = this._node(referenceObject);
+                const newNode = this._node(newObject);
+
+                if (newNode.isAttached) {
+                        throw Error('Given object is already present in this SymbolTree, remove it first');
+                }
+
+                if (referenceNode.hasChildren) {
+                        this.insertAfter(referenceNode.lastChild, newObject);
+                }
+                else {
+                        newNode.parent = referenceObject;
+                        referenceNode.firstChild = newObject;
+                        referenceNode.lastChild = newObject;
+                        referenceNode.childrenChanged();
+                }
+
+                return newObject;
+        }
+}
+
+module.exports = SymbolTree;
+SymbolTree.TreePosition = TreePosition;
diff --git a/node_modules/symbol-tree/lib/SymbolTreeNode.js b/node_modules/symbol-tree/lib/SymbolTreeNode.js
new file mode 100644
index 0000000..cae7f9a
--- /dev/null
+++ b/node_modules/symbol-tree/lib/SymbolTreeNode.js
@@ -0,0 +1,54 @@
+'use strict';
+
+module.exports = class SymbolTreeNode {
+        constructor() {
+                this.parent = null;
+                this.previousSibling = null;
+                this.nextSibling = null;
+
+                this.firstChild = null;
+                this.lastChild = null;
+
+                /** This value is incremented anytime a children is added or removed */
+                this.childrenVersion = 0;
+                /** The last child object which has a cached index */
+                this.childIndexCachedUpTo = null;
+
+                /** This value represents the cached node index, as long as
+                 * cachedIndexVersion matches with the childrenVersion of the parent */
+                this.cachedIndex = -1;
+                this.cachedIndexVersion = NaN; // NaN is never equal to anything
+        }
+
+        get isAttached() {
+                return Boolean(this.parent || this.previousSibling || this.nextSibling);
+        }
+
+        get hasChildren() {
+                return Boolean(this.firstChild);
+        }
+
+        childrenChanged() {
+                /* jshint -W016 */
+                // integer wrap around
+                this.childrenVersion = (this.childrenVersion + 1) & 0xFFFFFFFF;
+                this.childIndexCachedUpTo = null;
+        }
+
+        getCachedIndex(parentNode) {
+                // (assumes parentNode is actually the parent)
+                if (this.cachedIndexVersion !== parentNode.childrenVersion) {
+                        this.cachedIndexVersion = NaN;
+                        // cachedIndex is no longer valid
+                        return -1;
+                }
+
+                return this.cachedIndex; // -1 if not cached
+        }
+
+        setCachedIndex(parentNode, index) {
+                // (assumes parentNode is actually the parent)
+                this.cachedIndexVersion = parentNode.childrenVersion;
+                this.cachedIndex = index;
+        }
+};
diff --git a/node_modules/symbol-tree/lib/TreeIterator.js b/node_modules/symbol-tree/lib/TreeIterator.js
new file mode 100644
index 0000000..f9d6217
--- /dev/null
+++ b/node_modules/symbol-tree/lib/TreeIterator.js
@@ -0,0 +1,69 @@
+'use strict';
+
+const TREE = Symbol();
+const ROOT = Symbol();
+const NEXT = Symbol();
+const ITERATE_FUNC = Symbol();
+
+class TreeIterator {
+        constructor(tree, root, firstResult, iterateFunction) {
+                this[TREE] = tree;
+                this[ROOT] = root;
+                this[NEXT] = firstResult;
+                this[ITERATE_FUNC] = iterateFunction;
+        }
+
+        next() {
+                const tree = this[TREE];
+                const iterateFunc = this[ITERATE_FUNC];
+                const root = this[ROOT];
+
+                if (!this[NEXT]) {
+                        return {
+                                done: true,
+                                value: root,
+                        };
+                }
+
+                const value = this[NEXT];
+
+                if (iterateFunc === 1) {
+                        this[NEXT] = tree._node(value).previousSibling;
+                }
+                else if (iterateFunc === 2) {
+                        this[NEXT] = tree._node(value).nextSibling;
+                }
+                else if (iterateFunc === 3) {
+                        this[NEXT] = tree._node(value).parent;
+                }
+                else if (iterateFunc === 4) {
+                        this[NEXT] = tree.preceding(value, {root: root});
+                }
+                else /* if (iterateFunc === 5)*/ {
+                        this[NEXT] = tree.following(value, {root: root});
+                }
+
+                return {
+                        done: false,
+                        value: value,
+                };
+        }
+}
+
+Object.defineProperty(TreeIterator.prototype, Symbol.iterator, {
+        value: function() {
+                return this;
+        },
+        writable: false,
+});
+
+TreeIterator.PREV = 1;
+TreeIterator.NEXT = 2;
+TreeIterator.PARENT = 3;
+TreeIterator.PRECEDING = 4;
+TreeIterator.FOLLOWING = 5;
+
+Object.freeze(TreeIterator);
+Object.freeze(TreeIterator.prototype);
+
+module.exports = TreeIterator;
diff --git a/node_modules/symbol-tree/lib/TreePosition.js b/node_modules/symbol-tree/lib/TreePosition.js
new file mode 100644
index 0000000..fd2b6ed
--- /dev/null
+++ b/node_modules/symbol-tree/lib/TreePosition.js
@@ -0,0 +1,11 @@
+'use strict';
+
+/* eslint-disable sort-keys */
+module.exports = Object.freeze({
+        // same as DOM DOCUMENT_POSITION_
+        DISCONNECTED: 1,
+        PRECEDING: 2,
+        FOLLOWING: 4,
+        CONTAINS: 8,
+        CONTAINED_BY: 16,
+});