"use strict"

module.exports = function() {
	function appendChild(child) {
		var ancestor = this
		while (ancestor !== child && ancestor !== null) ancestor = ancestor.parentNode
		if (ancestor === child) throw new Error("Node cannot be inserted at the specified point in the hierarchy")
		
		if (child.nodeType == null) throw new Error("Argument is not a DOM element")
		
		var index = this.childNodes.indexOf(child)
		if (index > -1) this.childNodes.splice(index, 1)
		if (child.nodeType === 11) {
			while (child.firstChild != null) this.appendChild(child.firstChild)
			child.childNodes = []
		}
		else {
			this.childNodes.push(child)
			if (child.parentNode != null && child.parentNode !== this) child.parentNode.removeChild(child)
			child.parentNode = this
		}
	}
	function removeChild(child) {
		var index = this.childNodes.indexOf(child)
		if (index > -1) {
			this.childNodes.splice(index, 1)
			child.parentNode = null
		}
		else throw new TypeError("Failed to execute 'removeChild'")
	}
	function insertBefore(child, reference) {
		var ancestor = this
		while (ancestor !== child && ancestor !== null) ancestor = ancestor.parentNode
		if (ancestor === child) throw new Error("Node cannot be inserted at the specified point in the hierarchy")
		
		if (child.nodeType == null) throw new Error("Argument is not a DOM element")
		
		var refIndex = this.childNodes.indexOf(reference)
		var index = this.childNodes.indexOf(child)
		if (reference !== null && refIndex < 0) throw new TypeError("Invalid argument")
		if (index > -1) this.childNodes.splice(index, 1)
		if (reference === null) this.appendChild(child)
		else {
			if (child.nodeType === 11) {
				this.childNodes.splice.apply(this.childNodes, [refIndex, 0].concat(child.childNodes))
				while (child.firstChild) {
					var subchild = child.firstChild
					child.removeChild(subchild)
					subchild.parentNode = this
				}
				child.childNodes = []
			}
			else {
				this.childNodes.splice(refIndex, 0, child)
				if (child.parentNode != null && child.parentNode !== this) child.parentNode.removeChild(child)
				child.parentNode = this
			}
		}
	}
	function setAttribute(name, value) {
		var nodeValue = String(value)
		this.attributes[name] = {
			namespaceURI: null,
			get nodeValue() {return nodeValue},
			set nodeValue(value) {nodeValue = String(value)},
		}
	}
	function setAttributeNS(ns, name, value) {
		this.setAttribute(name, value)
		this.attributes[name].namespaceURI = ns
	}
	function removeAttribute(name) {
		delete this.attributes[name]
	}
	var activeElement
	var $window = {
		document: {
			createElement: function(tag, is) {
				var style = {}
				var element = {
					nodeType: 1,
					nodeName: tag.toUpperCase(),
					namespaceURI: "http://www.w3.org/1999/xhtml",
					appendChild: appendChild,
					removeChild: removeChild,
					insertBefore: insertBefore,
					setAttribute: setAttribute,
					setAttributeNS: setAttributeNS,
					removeAttribute: removeAttribute,
					parentNode: null,
					childNodes: [],
					attributes: {},
					get firstChild() {
						return this.childNodes[0] || null
					},
					get nextSibling() {
						if (this.parentNode == null) return null
						var index = this.parentNode.childNodes.indexOf(this)
						if (index < 0) throw new TypeError("Parent's childNodes is out of sync")
						return this.parentNode.childNodes[index + 1] || null
					},
					set textContent(value) {
						this.childNodes = []
						if (value !== "") this.appendChild($window.document.createTextNode(value))
					},
					set innerHTML(value) {
						while (this.firstChild) this.removeChild(this.firstChild)
						
						var stack = [this], depth = 0, voidElements = ["area", "base", "br", "col", "command", "embed", "hr", "img", "input", "keygen", "link", "meta", "param", "source", "track", "wbr"]
						value.replace(/<([a-z0-9\-]+?)((?:\s+?[^=]+?=(?:"[^"]*?"|'[^']*?'|[^\s>]*))*?)(\s*\/)?>|<\/([a-z0-9\-]+?)>|([^<]+)/g, function(match, startTag, attrs, selfClosed, endTag, text) {
							if (startTag) {
								var element = $window.document.createElement(startTag)
								attrs.replace(/\s+?([^=]+?)=(?:"([^"]*?)"|'([^']*?)'|([^\s>]*))/g, function(match, key, doubleQuoted, singleQuoted, unquoted) {
									var keyParts = key.split(":")
									var name = keyParts.pop()
									var ns = keyParts[0]
									var value = doubleQuoted || singleQuoted || unquoted || ""
									if (ns != null) element.setAttributeNS(ns, name, value)
									else element.setAttribute(name, value)
								})
								stack[depth].appendChild(element)
								if (!selfClosed && voidElements.indexOf(startTag.toLowerCase()) < 0) stack[++depth] = element
							}
							else if (endTag) {
								depth--
							}
							else if (text) {
								stack[depth].appendChild($window.document.createTextNode(text)) // FIXME handle html entities
							}
						})
					},
					get style() {
						return style
					},
					set style(value) {
						if (typeof value === "string") {
							for (var key in style) style[key] = ""
							var rules = value.split(";")
							for (var i = 0; i < rules.length; i++) {
								var rule = rules[i]
								var colonIndex = rule.indexOf(":")
								if (colonIndex > -1) {
									var key = rule.slice(0, colonIndex).trim().replace(/-\D/g, function(match) {return match[1].toUpperCase()})
									var value = rule.slice(colonIndex + 1).trim()
									style[key] = value
								}
							}
						}
					},
					focus: function() {activeElement = this},
					dispatchEvent: function(e) {
						e.target = this
						if (typeof this["on" + e.type] === "function") this["on" + e.type](e)
					},
				}
				if (element.nodeName === "A") {
					var href
					Object.defineProperty(element, "href", {
						get: function() {return this.attributes["href"] === undefined ? "" : "[FIXME implement]"},
						set: function(value) {this.setAttribute("href", value)},
						enumerable: true,
					})
				}
				if (element.nodeName === "INPUT") {
					var checked
					Object.defineProperty(element, "checked", {
						get: function() {return checked === undefined ? this.attributes["checked"] !== undefined : checked},
						set: function(value) {checked = Boolean(value)},
						enumerable: true,
					})
				}
				return element
			},
			createElementNS: function(ns, tag, is) {
				var element = this.createElement(tag, is)
				element.nodeName = tag
				element.namespaceURI = ns
				return element
			},
			createTextNode: function(text) {
				var nodeValue = String(text)
				return {
					nodeType: 3,
					nodeName: "#text",
					parentNode: null,
					get nodeValue() {return nodeValue},
					set nodeValue(value) {nodeValue = String(value)},
				}
			},
			createDocumentFragment: function() {
				return {
					nodeType: 11,
					nodeName: "#document-fragment",
					appendChild: appendChild,
					insertBefore: insertBefore,
					removeChild: removeChild,
					parentNode: null,
					childNodes: [],
					get firstChild() {
						return this.childNodes[0] || null
					},
				}
			},
			createEvent: function() {
				return {
					initEvent: function(type) {this.type = type},
				}
			},
			get activeElement() {return activeElement},
		},
	}
	$window.document.documentElement = $window.document.createElement("html")
	$window.document.documentElement.appendChild($window.document.createElement("head"))
	$window.document.body = $window.document.createElement("body")
	$window.document.documentElement.appendChild($window.document.body)
	activeElement = $window.document.body
	
	return $window
}