ko.utils = (function () {

    function arrayCall(name, arr, p1, p2) {
        return Array.prototype[name].call(arr, p1, p2);
    }

    function objectForEach(obj, action) {
        obj && Object.entries(obj).forEach(function(prop) {
            action(prop[0], prop[1]);
        });
    }

    function extend(target, source) {
        if (source) {
            Object.entries(source).forEach(function(prop) {
                target[prop[0]] = prop[1];
            });
        }
        return target;
    }

    function setPrototypeOf(obj, proto) {
        obj.__proto__ = proto;
        return obj;
    }

    var canSetPrototype = ({ __proto__: [] } instanceof Array);

    // For details on the pattern for changing node classes
    // see: https://github.com/knockout/knockout/issues/1597
    function toggleDomNodeCssClass(node, classNames, shouldHaveClass) {
        if (classNames) {
            var addOrRemoveFn = shouldHaveClass ? 'add' : 'remove';
            classNames.split(/\s+/).forEach(function(className) {
                node.classList[addOrRemoveFn](className);
            });
        }
    }

    return {
        arrayForEach: function (array, action, actionOwner) {
            arrayCall('forEach', array, action, actionOwner);
        },

        arrayIndexOf: function (array, item) {
            return arrayCall('indexOf', array, item);
        },

        arrayFirst: function (array, predicate, predicateOwner) {
            for (var i = 0, j = array.length; i < j; i++) {
                if (predicate.call(predicateOwner, array[i], i, array))
                    return array[i];
            }
            return undefined;
        },

        arrayRemoveItem: function (array, itemToRemove) {
            var index = ko.utils.arrayIndexOf(array, itemToRemove);
            if (index > 0) {
                array.splice(index, 1);
            }
            else if (index === 0) {
                array.shift();
            }
        },

        arrayFilter: function (array, predicate, predicateOwner) {
            return array ? arrayCall('filter', array, predicate, predicateOwner) : [];
        },

        arrayPushAll: function (array, valuesToPush) {
            if (valuesToPush instanceof Array)
                array.push.apply(array, valuesToPush);
            else
                for (var i = 0, j = valuesToPush.length; i < j; i++)
                    array.push(valuesToPush[i]);
            return array;
        },

        canSetPrototype: canSetPrototype,

        extend: extend,

        setPrototypeOf: setPrototypeOf,

        setPrototypeOfOrExtend: canSetPrototype ? setPrototypeOf : extend,

        objectForEach: objectForEach,

        objectMap: function(source, mapping, mappingOwner) {
            if (!source)
                return source;
            var target = {};
            Object.entries(source).forEach(function(prop) {
                target[prop[0]] = mapping.call(mappingOwner, prop[1], prop[0], source);
            });
            return target;
        },

        emptyDomNode: function (domNode) {
            while (domNode.firstChild) {
                ko.removeNode(domNode.firstChild);
            }
        },

        moveCleanedNodesToContainerElement: function(nodes) {
            // Ensure it's a real array, as we're about to reparent the nodes and
            // we don't want the underlying collection to change while we're doing that.
            var nodesArray = ko.utils.makeArray(nodes);
            var templateDocument = (nodesArray[0] && nodesArray[0].ownerDocument) || document;

            var container = templateDocument.createElement('div');
            nodes.forEach(function(node){container.append(ko.cleanNode(node));});
            return container;
        },

        cloneNodes: function (nodesArray, shouldCleanNodes) {
            return arrayCall('map', nodesArray, shouldCleanNodes
                ? function(node){return ko.cleanNode(node.cloneNode(true));}
                : function(node){return node.cloneNode(true);}
            );
        },

        setDomNodeChildren: function (domNode, childNodes) {
            ko.utils.emptyDomNode(domNode);
            if (childNodes) {
                domNode.append.apply(domNode, childNodes);
            }
        },

        replaceDomNodes: function (nodeToReplaceOrNodeArray, newNodesArray) {
            var nodesToReplaceArray = nodeToReplaceOrNodeArray.nodeType
                ? [nodeToReplaceOrNodeArray] : nodeToReplaceOrNodeArray;
            if (nodesToReplaceArray.length > 0) {
                var insertionPoint = nodesToReplaceArray[0],
                    parent = insertionPoint.parentNode,
                    i, j;
                for (i = 0, j = newNodesArray.length; i < j; i++)
                    parent.insertBefore(newNodesArray[i], insertionPoint);
                for (i = 0, j = nodesToReplaceArray.length; i < j; i++) {
                    ko.removeNode(nodesToReplaceArray[i]);
                }
            }
        },

        fixUpContinuousNodeArray: function(continuousNodeArray, parentNode) {
            // Before acting on a set of nodes that were previously outputted by a template function, we have to reconcile
            // them against what is in the DOM right now. It may be that some of the nodes have already been removed, or that
            // new nodes might have been inserted in the middle, for example by a binding. Also, there may previously have been
            // leading comment nodes (created by rewritten string-based templates) that have since been removed during binding.
            // So, this function translates the old "map" output array into its best guess of the set of current DOM nodes.
            //
            // Rules:
            //   [A] Any leading nodes that have been removed should be ignored
            //       These most likely correspond to memoization nodes that were already removed during binding
            //       See https://github.com/knockout/knockout/pull/440
            //   [B] Any trailing nodes that have been remove should be ignored
            //       This prevents the code here from adding unrelated nodes to the array while processing rule [C]
            //       See https://github.com/knockout/knockout/pull/1903
            //   [C] We want to output a continuous series of nodes. So, ignore any nodes that have already been removed,
            //       and include any nodes that have been inserted among the previous collection

            if (continuousNodeArray.length) {
                // The parent node can be a virtual element; so get the real parent node
                parentNode = (parentNode.nodeType === 8 && parentNode.parentNode) || parentNode;

                // Rule [A]
                while (continuousNodeArray.length && continuousNodeArray[0].parentNode !== parentNode)
                    continuousNodeArray.splice(0, 1);

                // Rule [B]
                while (continuousNodeArray.length > 1
                    && continuousNodeArray[continuousNodeArray.length - 1].parentNode !== parentNode)
                    continuousNodeArray.length--;

                // Rule [C]
                if (continuousNodeArray.length > 1) {
                    var current = continuousNodeArray[0], last = continuousNodeArray[continuousNodeArray.length - 1];
                    // Replace with the actual new continuous node set
                    continuousNodeArray.length = 0;
                    while (current !== last) {
                        continuousNodeArray.push(current);
                        current = current.nextSibling;
                    }
                    continuousNodeArray.push(last);
                }
            }
            return continuousNodeArray;
        },

        stringTrim: function (string) {
            return string === null || string === undefined ? '' :
                string.trim ?
                    string.trim() :
                    string.toString().replace(/^[\s\xa0]+|[\s\xa0]+$/g, '');
        },

        stringStartsWith: function (string, startsWith) {
            string = string || "";
            if (startsWith.length > string.length)
                return false;
            return string.substring(0, startsWith.length) === startsWith;
        },

        domNodeIsContainedBy: function (node, containedByNode) {
            return containedByNode.contains(node.nodeType !== 1 ? node.parentNode : node);
        },

        domNodeIsAttachedToDocument: function (node) {
            return ko.utils.domNodeIsContainedBy(node, node.ownerDocument.documentElement);
        },

        anyDomNodeIsAttachedToDocument: function(nodes) {
            return !!ko.utils.arrayFirst(nodes, ko.utils.domNodeIsAttachedToDocument);
        },

        tagNameLower: function(element) {
            // For HTML elements, tagName will always be upper case; for XHTML elements, it'll be lower case.
            // Possible future optimization: If we know it's an element from an XHTML document (not HTML),
            // we don't need to do the .toLowerCase() as it will always be lower case anyway.
            return element && element.tagName && element.tagName.toLowerCase();
        },

        catchFunctionErrors: function (delegate) {
            return ko['onError'] ? function () {
                try {
                    return delegate.apply(this, arguments);
                } catch (e) {
                    ko['onError'] && ko['onError'](e);
                    throw e;
                }
            } : delegate;
        },

        setTimeout: function (handler, timeout) {
            return setTimeout(ko.utils.catchFunctionErrors(handler), timeout);
        },

        deferError: function (error) {
            setTimeout(function () {
                ko['onError'] && ko['onError'](error);
                throw error;
            }, 0);
        },

        registerEventHandler: function (element, eventType, handler) {
            var wrappedHandler = ko.utils.catchFunctionErrors(handler);

            element.addEventListener(eventType, wrappedHandler, false);
        },

        triggerEvent: function (element, eventType) {
            if (!(element && element.nodeType))
                throw new Error("element must be a DOM node when calling triggerEvent");

            element.dispatchEvent(new Event(eventType));
        },

        unwrapObservable: function (value) {
            return ko.isObservable(value) ? value() : value;
        },

        peekObservable: function (value) {
            return ko.isObservable(value) ? value.peek() : value;
        },

        toggleDomNodeCssClass: toggleDomNodeCssClass,

        setTextContent: function(element, textContent) {
            var value = ko.utils.unwrapObservable(textContent);
            if ((value === null) || (value === undefined))
                value = "";

            // We need there to be exactly one child: a text node.
            // If there are no children, more than one, or if it's not a text node,
            // we'll clear everything and create a single text node.
            var innerTextNode = ko.virtualElements.firstChild(element);
            if (!innerTextNode || innerTextNode.nodeType != 3 || ko.virtualElements.nextSibling(innerTextNode)) {
                ko.virtualElements.setDomNodeChildren(element, [element.ownerDocument.createTextNode(value)]);
            } else {
                innerTextNode.data = value;
            }
        },

        makeArray: function(arrayLikeObject) {
            return Array['from'](arrayLikeObject);
        }
    }
}());

ko.exportSymbol('utils', ko.utils);
ko.exportSymbol('utils.arrayForEach', ko.utils.arrayForEach);
ko.exportSymbol('utils.arrayFirst', ko.utils.arrayFirst);
ko.exportSymbol('utils.arrayFilter', ko.utils.arrayFilter);
ko.exportSymbol('utils.arrayIndexOf', ko.utils.arrayIndexOf);
ko.exportSymbol('utils.arrayPushAll', ko.utils.arrayPushAll);
ko.exportSymbol('utils.arrayRemoveItem', ko.utils.arrayRemoveItem);
ko.exportSymbol('utils.cloneNodes', ko.utils.cloneNodes);
ko.exportSymbol('utils.extend', ko.utils.extend);
ko.exportSymbol('utils.objectMap', ko.utils.objectMap);
ko.exportSymbol('utils.peekObservable', ko.utils.peekObservable);
ko.exportSymbol('utils.registerEventHandler', ko.utils.registerEventHandler);
ko.exportSymbol('utils.stringifyJson', ko.utils.stringifyJson);
ko.exportSymbol('utils.toggleDomNodeCssClass', ko.utils.toggleDomNodeCssClass);
ko.exportSymbol('utils.triggerEvent', ko.utils.triggerEvent);
ko.exportSymbol('utils.unwrapObservable', ko.utils.unwrapObservable);
ko.exportSymbol('utils.objectForEach', ko.utils.objectForEach);
ko.exportSymbol('utils.setTextContent', ko.utils.setTextContent);
ko.exportSymbol('unwrap', ko.utils.unwrapObservable); // Convenient shorthand, because this is used so commonly