"use strict"

module.exports = function() {
	function isModernEvent(type) {
		return type === "transitionstart" || type === "transitionend" || type === "animationstart" || type === "animationend"
	}
	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 getAttribute(name) {
		if (this.attributes[name] == null) return null
		return this.attributes[name].nodeValue
	}
	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 declListTokenizer = /;|"(?:\\.|[^"\n])*"|'(?:\\.|[^'\n])*'/g
	/**
	 * This will split a semicolon-separated CSS declaration list into an array of
	 * individual declarations, ignoring semicolons in strings.
	 *
	 * Comments are also stripped.
	 *
	 * @param {string} declList
	 * @return {string[]}
	 */
	function splitDeclList(declList) {
		var indices = [], res = [], match

		// remove comments, preserving comments in strings.
		declList = declList.replace(
			/("(?:\\.|[^"\n])*"|'(?:\\.|[^'\n])*')|\/\*[\s\S]*?\*\//g,
			function(m, str){
				return str || ''
			}
		)
		/*eslint-disable no-cond-assign*/
		while (match = declListTokenizer.exec(declList)) {
			if (match[0] === ";") indices.push(match.index)
		}
		/*eslint-enable no-cond-assign*/
		for (var i = indices.length; i--;){
			res.unshift(declList.slice(indices[i] + 1))
			declList = declList.slice(0, indices[i])
		}
		res.unshift(declList)
		return res
	}

	var activeElement
	var $window = {
		document: {
			createElement: function(tag, is) {
				var cssText = ""
				var style = {}
				Object.defineProperty(style, "cssText", {
					get: function() {return cssText},
					set: function (value) {
						var buf = []
						if (typeof value === "string") {
							for (var key in style) style[key] = ""
							var rules = splitDeclList(value)
							for (var i = 0; i < rules.length; i++) {
								var rule = rules[i]
								var colonIndex = rule.indexOf(":")
								if (colonIndex > -1) {
									var rawKey = rule.slice(0, colonIndex).trim()
									var key = rawKey.replace(/-\D/g, function(match) {return match[1].toUpperCase()})
									var value = rule.slice(colonIndex + 1).trim()
									if (key !== "cssText") {
										style[key] = value
										buf.push(rawKey + ": " + value + ";")
									}
								}
							}
							cssText = buf.join(" ")
						}
					}
				})
				var events = {}
				var element = {
					nodeType: 1,
					nodeName: tag.toUpperCase(),
					namespaceURI: "http://www.w3.org/1999/xhtml",
					appendChild: appendChild,
					removeChild: removeChild,
					insertBefore: insertBefore,
					getAttribute: getAttribute,
					setAttribute: setAttribute,
					setAttributeNS: setAttributeNS,
					removeAttribute: removeAttribute,
					parentNode: null,
					childNodes: [],
					attributes: {},
					get firstChild() {
						return this.childNodes[0] || null
					},
					get nextSibling() {
						if (this.parentNode == null) return null
						var index = this.parentNode.childNodes.indexOf(this)
						if (index < 0) throw new TypeError("Parent's childNodes is out of sync")
						return this.parentNode.childNodes[index + 1] || null
					},
					set textContent(value) {
						this.childNodes = []
						if (value !== "") this.appendChild($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(_){
						// https://developer.mozilla.org/en-US/docs/Web/API/HTMLElement/style#Setting_style
						throw new Error("setting element.style is not portable")
					},
					get className() {
						return this.attributes["class"] ? this.attributes["class"].nodeValue : ""
					},
					set className(value) {
						if (this.namespaceURI === "http://www.w3.org/2000/svg") throw new Error("Cannot set property className of SVGElement")
						else this.setAttribute("class", value)
					},
					focus: function() {activeElement = this},
					addEventListener: function(type, callback, useCapture) {
						if (events[type] == null) events[type] = [callback]
						else events[type].push(callback)
					},
					removeEventListener: function(type, callback, useCapture) {
						if (events[type] != null) {
							var index = events[type].indexOf(callback)
							if (index > -1) events[type].splice(index, 1)
						}
					},
					dispatchEvent: function(e) {
						if (this.nodeName === "INPUT" && this.attributes["type"] != null && this.attributes["type"].nodeValue === "checkbox" && e.type === "click") {
							this.checked = !this.checked
						}

						e.target = this
						if (events[e.type] != null) {
							for (var i = 0; i < events[e.type].length; i++) {
								events[e.type][i].call(this, e)
							}
						}
						e.preventDefault = function() {
							// TODO: should this do something?
						}
						if (typeof this["on" + e.type] === "function" && !isModernEvent(e.type)) this["on" + e.type](e)
					},
					onclick: null,
				}

				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,
					})

					element.value = ""
				}

				if (element.nodeName === "TEXTAREA") {
					var value
					Object.defineProperty(element, "value", {
						get: function() {
							return value != null ? value :
								this.firstChild ? this.firstChild.nodeValue : ""
						},
						set: function(v) {value = v},
						enumerable: true,
					})
				}
				
				if (element.nodeName === "CANVAS") {
					Object.defineProperty(element, "width", {
						get: function() {return this.attributes["width"] ? Math.floor(parseInt(this.attributes["width"].nodeValue) || 0) : 300},
						set: function(value) {this.setAttribute("width", Math.floor(Number(value) || 0).toString())},
					})
					Object.defineProperty(element, "height", {
						get: function() {return this.attributes["height"] ? Math.floor(parseInt(this.attributes["height"].nodeValue) || 0) : 300},
						set: function(value) {this.setAttribute("height", Math.floor(Number(value) || 0).toString())},
					})
				}

				function getOptions(element) {
					var options = []
					for (var i = 0; i < element.childNodes.length; i++) {
						if (element.childNodes[i].nodeName === "OPTION") options.push(element.childNodes[i])
						else if (element.childNodes[i].nodeName === "OPTGROUP") options = options.concat(getOptions(element.childNodes[i]))
					}
					return options
				}
				function getOptionValue(element) {
					return element.attributes["value"] != null ?
						element.attributes["value"].nodeValue :
						element.firstChild != null ? element.firstChild.nodeValue : ""
				}
				if (element.nodeName === "SELECT") {
					var selectedValue, selectedIndex = 0
					Object.defineProperty(element, "selectedIndex", {
						get: function() {return getOptions(this).length > 0 ? selectedIndex : -1},
						set: function(value) {
							var options = getOptions(this)
							if (value >= 0 && value < options.length) {
								selectedValue = getOptionValue(options[selectedIndex])
								selectedIndex = value
							}
							else {
								selectedValue = ""
								selectedIndex = -1
							}
						},
						enumerable: true,
					})
					Object.defineProperty(element, "value", {
						get: function() {
							if (this.selectedIndex > -1) return getOptionValue(getOptions(this)[this.selectedIndex])
							return ""
						},
						set: function(value) {
							var options = getOptions(this)
							var stringValue = String(value)
							for (var i = 0; i < options.length; i++) {
								if (getOptionValue(options[i]) === stringValue) {
									selectedValue = stringValue
									selectedIndex = i
									return
								}
							}
							selectedValue = stringValue
							selectedIndex = -1
						},
						enumerable: true,
					})
				}
				if (element.nodeName === "OPTION") {
					Object.defineProperty(element, "value", {
						get: function() {return getOptionValue(this)},
						set: function(value) {
							this.setAttribute("value", value)
						},
						enumerable: true,
					})
					Object.defineProperty(element, "selected", {
						get: function() {
							var options = getOptions(this.parentNode)
							var index = options.indexOf(this)
							return index === this.parentNode.selectedIndex
						},
						set: function(value) {
							if (value) {
								var options = getOptions(this.parentNode)
								var index = options.indexOf(this)
								if (index > -1) this.parentNode.selectedIndex = index
							}
							else this.parentNode.selectedIndex = 0
						},
						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
}