// Copyright (c) Microsoft Open Technologies, Inc.  All rights reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
// JavaScript Dynamic Content shim for Windows Store apps
(function () {

    if (window.MSApp && MSApp.execUnsafeLocalFunction) {

        // Some nodes will have an "attributes" property which shadows the Node.prototype.attributes property
        //  and means we don't actually see the attributes of the Node (interestingly the VS debug console
        //  appears to suffer from the same issue).
        //
        var Element_setAttribute = Object.getOwnPropertyDescriptor(Element.prototype, "setAttribute").value;
        var Element_removeAttribute = Object.getOwnPropertyDescriptor(Element.prototype, "removeAttribute").value;
        var HTMLElement_insertAdjacentHTMLPropertyDescriptor = Object.getOwnPropertyDescriptor(HTMLElement.prototype, "insertAdjacentHTML");
        var Node_get_attributes = Object.getOwnPropertyDescriptor(Node.prototype, "attributes").get;
        var Node_get_childNodes = Object.getOwnPropertyDescriptor(Node.prototype, "childNodes").get;
        var detectionDiv = document.createElement("div");

        function getAttributes(element) {
            return Node_get_attributes.call(element);
        }

        function setAttribute(element, attribute, value) {
            try {
                Element_setAttribute.call(element, attribute, value);
            } catch (e) {
                // ignore
            }
        }

        function removeAttribute(element, attribute) {
            Element_removeAttribute.call(element, attribute);
        }

        function childNodes(element) {
            return Node_get_childNodes.call(element);
        }

        function empty(element) {
            while (element.childNodes.length) {
                element.removeChild(element.lastChild);
            }
        }

        function insertAdjacentHTML(element, position, html) {
            HTMLElement_insertAdjacentHTMLPropertyDescriptor.value.call(element, position, html);
        }
        
        function inUnsafeMode() {
            var isUnsafe = true;
            try {
                detectionDiv.innerHTML = "<test/>";
            }
            catch (ex) {
                isUnsafe = false;
            }
            
            return isUnsafe;
        }

        function cleanse(html, targetElement) {
            var cleaner = document.implementation.createHTMLDocument("cleaner");
            empty(cleaner.documentElement);
            MSApp.execUnsafeLocalFunction(function () {
                insertAdjacentHTML(cleaner.documentElement, "afterbegin", html);
            });

            var scripts = cleaner.documentElement.querySelectorAll("script");
            Array.prototype.forEach.call(scripts, function (script) {
                switch (script.type.toLowerCase()) {
                    case "":
                        script.type = "text/inert";
                        break;
                    case "text/javascript":
                    case "text/ecmascript":
                    case "text/x-javascript":
                    case "text/jscript":
                    case "text/livescript":
                    case "text/javascript1.1":
                    case "text/javascript1.2":
                    case "text/javascript1.3":
                        script.type = "text/inert-" + script.type.slice("text/".length);
                        break;
                    case "application/javascript":
                    case "application/ecmascript":
                    case "application/x-javascript":
                        script.type = "application/inert-" + script.type.slice("application/".length);
                        break;

                    default:
                        break;
                }
            });

            function cleanseAttributes(element) {
                var attributes = getAttributes(element);
                if (attributes && attributes.length) {
                    // because the attributes collection is live it is simpler to queue up the renames
                    var events;
                    for (var i = 0, len = attributes.length; i < len; i++) {
                        var attribute = attributes[i];
                        var name = attribute.name;
                        if ((name[0] === "o" || name[0] === "O") &&
                            (name[1] === "n" || name[1] === "N")) {
                            events = events || [];
                            events.push({ name: attribute.name, value: attribute.value });
                        }
                    }
                    if (events) {
                        for (var i = 0, len = events.length; i < len; i++) {
                            var attribute = events[i];
                            removeAttribute(element, attribute.name);
                            setAttribute(element, "x-" + attribute.name, attribute.value);
                        }
                    }
                }
                var children = childNodes(element);
                for (var i = 0, len = children.length; i < len; i++) {
                    cleanseAttributes(children[i]);
                }
            }
            cleanseAttributes(cleaner.documentElement);

            var cleanedNodes = [];

            if (targetElement.tagName === 'HTML') {
                cleanedNodes = Array.prototype.slice.call(document.adoptNode(cleaner.documentElement).childNodes);
            } else {
                if (cleaner.head) {
                    cleanedNodes = cleanedNodes.concat(Array.prototype.slice.call(document.adoptNode(cleaner.head).childNodes));
                }
                if (cleaner.body) {
                    cleanedNodes = cleanedNodes.concat(Array.prototype.slice.call(document.adoptNode(cleaner.body).childNodes));
                }  
            }

            return cleanedNodes;
        }

        function cleansePropertySetter(property, setter) {
            var propertyDescriptor = Object.getOwnPropertyDescriptor(HTMLElement.prototype, property);
            var originalSetter = propertyDescriptor.set;
            Object.defineProperty(HTMLElement.prototype, property, {
                get: propertyDescriptor.get,
                set: function (value) {
                    if(window.WinJS && window.WinJS._execUnsafe && inUnsafeMode()) {
                        originalSetter.call(this, value);
                    } else {
                        var that = this;
                        var nodes = cleanse(value, that);
                        MSApp.execUnsafeLocalFunction(function () {
                            setter(propertyDescriptor, that, nodes);
                        });
                    }
                },
                enumerable: propertyDescriptor.enumerable,
                configurable: propertyDescriptor.configurable,
            });
        }
        cleansePropertySetter("innerHTML", function (propertyDescriptor, target, elements) {
            empty(target);
            for (var i = 0, len = elements.length; i < len; i++) {
                target.appendChild(elements[i]);
            }
        });
        cleansePropertySetter("outerHTML", function (propertyDescriptor, target, elements) {
            for (var i = 0, len = elements.length; i < len; i++) {
                target.insertAdjacentElement("afterend", elements[i]);
            }
            target.parentNode.removeChild(target);
        });

    }

}());