Add Ref class to follow reactive elements

* Renamed to Observable
* Updated skooma.js to match the API

domProxy.js

@@ -1,21 +1,5 @@
-class ChildObserver extends MutationObserver {
+export const domArray = (methods, extra) => {
-	constructor() {
+	if (extra) return domArray(extra)(methods)
-		super(mutations => {
-			for (const mutation of mutations) {
-				mutation.target.dispatchEvent(new CustomEvent("change", {detail: mutation}))
-			}
-		})
-	}
-
-	observe(element) {
-		MutationObserver.prototype.observe.call(this, element, { childList: true })
-	}
-}
-
-const childObserver = new ChildObserver()
-
-export const lense = (methods, extra) => {
-	if (extra) return lense(extra)(methods)
 
 	const traps = {
 		get(target, prop) {
@@ -24,12 +8,12 @@ export const lense = (methods, extra) => {
 			} else if (prop === Symbol.iterator) {
 				return function*() {
 					for (const child of target.children) {
-						yield methods.get(child)
+						yield methods.get.call(child)
 					}
 				}
 			} else if (prop.match?.call(prop, /^[0-9]+$/)) {
 				const child = target.children[prop]
-				if (child) return methods.get(child)
+				if (child) return methods.get.call(child)
 				return child
 			} else {
 				return Array.prototype[prop]
@@ -39,7 +23,7 @@ export const lense = (methods, extra) => {
 			if (prop.match?.call(prop, /^[0-9]+$/)) {
 				const child = target.children[prop]
 				if (child) {
-					methods.set(child, value)
+					methods.set.call(child, value)
 					return true
 				} else {
 					for (let i = target.children.length; i < Number(prop); i++) {
@@ -47,8 +31,8 @@ export const lense = (methods, extra) => {
 					}
 					const element = methods.new(value)
 					target.appendChild(element)
-					if (methods.get(element) !== value)
+					if (methods.get.call(element) !== value)
-						methods.set(element, value)
+						methods.set.call(element, value)
 					return true
 				}
 			} else if (prop == "length") {
@@ -71,15 +55,20 @@ export const lense = (methods, extra) => {
 	}
 
 	return element => {
-		const proxy = new Proxy(element, traps)
+		if (!(element instanceof Element)) throw(new Error("Creating domArray on non-element"))
-
+		return new Proxy(element, traps)
-		if (methods.event) childObserver.observe(element)
-		if (typeof methods.event === "function") element.addEventListener("change", event => {
-			methods.event(proxy, element, event.detail)
-		})
-
-		return proxy
 	}
 }
 
-export default lense
+export const meta = (element=document.head) => new Proxy(element, {
+	get: (target, name) => target.querySelector(`meta[name="${name}"]`)?.content,
+	set: (target, name, value) => {
+		let meta = target.querySelector(`meta[name="${name}"]`)
+		if (!meta) {
+			meta = document.createElement("meta")
+			meta.name = name
+			target.append(meta)
+		}
+		meta.content = value
+	}
+})

jsconfig.json

@@ -0,0 +1,6 @@
+{
+	"compilerOptions": {
+		"checkJs": true,
+		"target": "es2021"
+	}
+}

observable.js

@@ -0,0 +1,428 @@
+/** @type FinalizationRegistry<AbortController> */
+const abortRegistry = new FinalizationRegistry(controller => controller.abort())
+
+/** @param {String} string */
+const camelToKebab = string => string.replace(/([a-z])([A-Z])/g, (_, a, b) => `${a}-${b.toLowerCase()}`)
+/** @param {String} string */
+const kebabToCamel = string => string.replace(/([a-z])-([a-z])/g, (_, a, b) => a+b.toUpperCase())
+
+const identity = object=>object
+
+const target = Symbol("Proxy Target")
+
+/* Custom Event Classes */
+
+export class SynchronousChangeEvent extends Event {
+	constructor(change) {
+		super('synchronous', {cancelable: true})
+		this.change = change
+	}
+}
+
+export class MultiChangeEvent extends Event {
+	#final
+	#values
+
+	constructor(...changes) {
+		super('change')
+		this.changes = changes
+	}
+
+	get values() {
+		if (!this.#values) {
+			const values = new Map()
+			for (const {property, from, to} of this.changes) {
+				let list = values.get(property)
+				if (!list) {
+					list = [from]
+					values.set(property, list)
+				}
+				list.push(to)
+			}
+			this.#values = values
+		}
+		return this.#values
+	}
+
+	get final() {
+		if (!this.#final) {
+			this.#final = new Map()
+			for (const [property, list] of this.values) {
+				if (list[0] !== list[list.length-1]) {
+					this.#final.set(property, list[list.length-1])
+				}
+			}
+		}
+		return this.#final
+	}
+}
+
+export class ValueChangeEvent extends MultiChangeEvent {
+	get value() {
+		return this.final.value
+	}
+}
+
+/* Observable Classes */
+
+export class Observable extends EventTarget {
+	#synchronous
+	/** @type Array<{name:string, from, to}> */
+	#queue
+	#abortController = new AbortController
+
+	#ref = new WeakRef(this)
+	get ref() { return this.#ref }
+
+	observable = true
+
+	constructor({synchronous}={}) {
+		super()
+		if (this.constructor === Observable) {
+			throw new TypeError("Cannot instantiate abstract class")
+		}
+		this.#synchronous = !!synchronous
+		abortRegistry.register(this, this.#abortController)
+
+		this.proxy = new Proxy(this.constructor.prototype.proxy, {
+			get: (target, prop) => target.call(this, prop)
+		})
+	}
+
+	proxy(prop, {get, set, ...options}={}) {
+		const proxy = new ProxiedObservableValue(this, prop, options)
+		if (get) proxy.get = get
+		if (set) proxy.set = set
+		return proxy
+	}
+
+	subscribe(prop, callback) {
+		if (!callback) return this.subscribe("value", prop)
+
+		const controller = new AbortController()
+		this.addEventListener("change", ({final}) => {
+			if (final.has(prop)) return callback(final.get(prop))
+		}, {signal: controller.signal})
+		callback(this.value)
+		return () => controller.abort()
+	}
+
+	enqueue(property, from, to, mutation=false) {
+		const change = {property, from, to, mutation}
+		if (!this.dispatchEvent(new SynchronousChangeEvent(change))) return false
+		if (!this.synchronous) {
+			if (!this.#queue) {
+				this.#queue = []
+				queueMicrotask(() => {
+					this.emit(...this.#queue)
+					this.#queue = undefined
+				})
+			}
+			this.#queue.push(change)
+		} else {
+			this.emit(change)
+		}
+		return true
+	}
+
+	emit() {
+		throw new TypeError(`${this.constructor.name} did not define an 'emit' method`)
+	}
+
+	get signal() { return this.#abortController.signal }
+	get synchronous() { return this.#synchronous }
+}
+
+export class ObservableObject extends Observable {
+	#shallow
+
+	constructor(target={}, {shallow, ...options}={}) {
+		super(options)
+		this.#shallow = !!shallow
+		this[target] = target
+		this.values = new Proxy(target, {
+			set: (target, prop, value) => {
+				const old = target[prop]
+				if (old === value) {
+					return true
+				} else {
+					if (this.enqueue(prop, old, value)) {
+						if (!this.#shallow) {
+							if (old instanceof Observable) this.disown(prop, old)
+							if (value instanceof Observable) this.adopt(prop, value)
+						}
+						target[prop] = value
+						return true
+					} else {
+						return false
+					}
+				}
+			},
+			get: (target, prop) => target[prop],
+		})
+	}
+
+	proxy(prop, {get, set, ...options}={}) {
+		const proxy = new ProxiedObservableValue(this, prop, {values: this.values, ...options})
+		if (get) proxy.get = get
+		if (set) proxy.set = set
+		return proxy
+	}
+
+	emit(...changes) {
+		this.dispatchEvent(new MultiChangeEvent(...changes))
+	}
+
+	/** @type Map<Observable, Map<String, Function>> */
+	#nested = new Map()
+
+	adopt(prop, observable) {
+		let handlers = this.#nested.get(observable)
+		if (!handlers) {
+			// Actual adoption
+			handlers = new Map()
+			this.#nested.set(observable, handlers)
+		}
+		const ref = this.ref
+		const handler = () => ref.deref()?.emit(prop, observable, observable, {observable: true})
+
+		handlers.set(prop, handler)
+		observable.addEventListener("change", handler, {signal: this.signal})
+	}
+
+	disown(prop, observable) {
+		const handlers = this.#nested.get(observable)
+		const handler = handlers.get(prop)
+		observable.removeEventListener("change", handler)
+		handlers.delete(prop)
+		if (handlers.size == 0) {
+			this.#nested.delete(observable)
+		}
+	}
+}
+
+export class ObservableValue extends Observable {
+	#value
+
+	constructor(value, options) {
+		super(options)
+		this.#value = value
+	}
+
+	get value() { return this.#value }
+	set value(value) {
+		if (this.enqueue("value", this.#value, value)) {
+			this.#value = value
+		}
+	}
+
+	emit(...changes) {
+		this.dispatchEvent(new ValueChangeEvent(...changes))
+	}
+}
+
+class ProxiedObservableValue extends ObservableValue {
+	#backend
+	#values
+	#prop
+
+	constructor(backend, prop, {values=backend, ...options}={}) {
+		super(options)
+		this.#backend = backend
+		this.#values = values
+		this.#prop = prop
+
+		const ref = this.ref
+		backend.addEventListener("synchronous", event => {
+			const {property, from, to, ...rest} = event.change
+			if (property == this.#prop) {
+				ref.deref()?.enqueue({
+					property,
+					from: this.get(from),
+					to: this.get(to),
+					...rest
+				})
+			}
+		}, { signal: this.signal })
+	}
+
+	get = identity
+	set = identity
+
+	get value() { return this.get(this.#values[this.#prop]) }
+	set value(value) { this.#values[this.#prop] = this.set(value) }
+}
+
+const attributeObserver = new MutationObserver(mutations => {
+	for (const {type, target, attributeName: name} of mutations) {
+		if (type == "attributes") {
+			const next = target.getAttribute(name)
+			const camelName = kebabToCamel(name)
+			if (String(target.state.values[camelName]) !== next)
+				target.state.values[camelName] = next
+		}
+	}
+})
+
+export const component = (name, generator, methods) => {
+	if (typeof name === "function") {
+		methods = generator
+		generator = name
+		name = camelToKebab(generator.name)
+	}
+	const Element = class extends HTMLElement{
+		constructor() {
+			super()
+			const target = Object.fromEntries([...this.attributes].map(attribute => [kebabToCamel(attribute.name), attribute.value]))
+			this.state = new ObservableObject(target)
+			this.state.addEventListener("change", event => {
+				for (const {property, to: value} of event.changes) {
+					const kebabName = camelToKebab(property)
+					if (this.getAttribute(kebabName) !== String(value))
+						this.setAttribute(kebabName, value)
+				}
+			})
+			attributeObserver.observe(this, {attributes: true})
+			const content = generator.call(this, this.state)
+			if (content) this.replaceChildren(content)
+		}
+	}
+	if (methods) {
+		Object.defineProperties(Element.prototype, Object.getOwnPropertyDescriptors(methods))
+	}
+	customElements.define(name, Element)
+	return Element;
+}
+
+class ObservableComposition extends ObservableValue {
+	#func
+	#states
+
+	constructor(func, options, ...states) {
+		super(options)
+
+		this.#func = func
+		this.#states = states
+
+		const abortController = new AbortController()
+		abortRegistry.register(this, abortController)
+		const ref = new WeakRef(this)
+
+		states.forEach(state => {
+			state.addEventListener("change", () => {
+				ref.deref()?.scheduleUpdate()
+			}, {signal: abortController.signal})
+		})
+
+		this.update()
+	}
+
+	#microtaskQueued
+	scheduleUpdate() {
+		if (this.synchronous) {
+			this.update()
+		} else {
+			if (!this.#microtaskQueued) {
+				queueMicrotask(() => {
+					this.#microtaskQueued = false
+					this.update()
+				})
+				this.#microtaskQueued = true
+			}
+		}
+	}
+
+	update() {
+		const value = this.#func(...this.#states.map(state => state.value))
+		const change = {property: "value", from: this.value, to: value}
+		this.value = value
+		this.emit(change)
+	}
+}
+
+export const compose = func => (...states) => new ObservableComposition(func, {}, ...states)
+
+class MutationEvent extends Event {
+	constructor() {
+		super("mutation", {bubbles: true})
+	}
+}
+
+const mutationObserver = new MutationObserver(mutations => {
+	for (const mutation of mutations) {
+		mutation.target.dispatchEvent(new MutationEvent())
+	}
+})
+
+export class ObservableElement extends Observable {
+	#getValue
+	#equal
+
+	#value
+	#changedValue = false
+
+	constructor(target, {get, equal, ...options}={}) {
+		super(options)
+		this[target] = target
+
+		this.#getValue = get ?? (target => target.value)
+		this.#equal = equal ?? ((a, b) => a===b)
+
+		this.#value = this.#getValue(target)
+
+		const controller = new AbortController()
+		target.addEventListener("mutation", event => { this.update(event) }, {signal: controller.signal})
+
+		abortRegistry.register(this, controller)
+		mutationObserver.observe(target, {
+			attributes: true,
+			childList: true,
+			characterData: true,
+			subtree: true,
+		})
+	}
+
+	get value() { return this.#value }
+
+	update() {
+		const current = this.#getValue(this[target])
+
+		if (this.#equal(this.#value, current)) return
+
+		this.#value = current
+
+		if (this.synchronous) {
+			this.dispatchEvent(new MultiChangeEvent(["value", current]))
+		} else {
+			if (!this.#changedValue) {
+				queueMicrotask(() => {
+					this.#changedValue = false
+					this.dispatchEvent(new MultiChangeEvent(["value", this.#changedValue]))
+				})
+				this.#changedValue = current
+			}
+		}
+	}
+}
+
+export class MapStorage extends Storage {
+	#map = new Map()
+	key(index) {
+		return [...this.#map.keys()][index]
+	}
+	getItem(keyName) {
+		if (this.#map.has(keyName))
+			return this.#map.get(keyName)
+		else
+			return null
+	}
+	setItem(keyName, keyValue) {
+		this.#map.set(keyName, String(keyValue))
+	}
+	removeItem(keyName) {
+		this.#map.delete(keyName)
+	}
+	clear() {
+		this.#map.clear()
+	}
+}

skooma.js

@@ -1,37 +1,75 @@
-/*
-A functional HTML generation library.
-
-Example:
-	html.label(
-		html.span("Delete everything", {class: ["warning", "important"]}),
-		html.button("Click", {onClick: e => document.body.innerHTML=""}),
-	)
-or
-	html.ul([1, 2, 3, 4, 5].map(x => html.li(x)), {class: "numbers"})
-*/
-
 // Keep a referee alive until a referrer is collected
 const weakReferences = new WeakMap()
 const untilDeathDoThemPart = (referrer, reference) => {
-	if (!weakReferences.has(referrer)) {
+	if (!weakReferences.has(referrer)) weakReferences.set(referrer, new Set())
-		weakReferences.set(referrer, new Set())
-	}
 	weakReferences.get(referrer).add(reference)
 }
 
-export const empty = Symbol("Explicit empty argument for Skooma")
+// Like AbortController, but resets after each abort
-
+class MultiAbortController {
-const keyToPropName = key => key.replace(/^[A-Z]/, a => "-"+a).replace(/[A-Z]/g, a => '-'+a.toLowerCase())
+	#controller = new AbortController()
-
+	get signal() { return this.#controller.signal }
-const insertStyles = (rule, styles) => {
+	abort() { this.#controller.abort(); this.#controller = new AbortController() }
-	for (const [key, value] of Object.entries(styles))
-		if (typeof value == "undefined")
-			rule.removeProperty(keyToPropName(key))
-	else
-		rule.setProperty(keyToPropName(key), value.toString())
 }
 
-const parseAttribute = (attribute) => {
+/** A symbol representing nothing to be appended to an element */
+export const empty = Symbol("Explicit empty argument for Skooma")
+
+/** Converts a snake-case string to a CSS property name
+* @param {string} key
+* @return {string}
+*/
+const snakeToCSS = key => key.replace(/^[A-Z]/, a => "-"+a).replace(/[A-Z]/g, a => '-'+a.toLowerCase())
+
+/**
+* @param {CSSStyleDeclaration} style The style property of a node
+* @param {object} rules A map of snake case property names to css values
+*/
+const insertStyles = (style, rules) => {
+	for (const [key, value] of Object.entries(rules))
+		if (typeof value == "undefined")
+			style.removeProperty(snakeToCSS(key))
+	else
+		style.setProperty(snakeToCSS(key), value.toString())
+}
+
+/** @typedef SpecialAttributeDescriptor
+* @type {object}
+* @property {function(this:any):void} [get]
+* @property {function(this:any,any):void} [set]
+* @property {function(this:any,function():void):void} [hook]
+*/
+
+/**
+* @type {Object<string,SpecialAttributeDescriptor>}
+*/
+const specialAttributes = {
+	value: {
+		get() { return this.value },
+		set(value) {
+			this.setAttribute("value", value)
+			this.value = value
+		},
+		hook(callback) { this.addEventListener("input", callback) }
+	},
+	style: {
+		set(value) { insertStyles(this.style, value) }
+	},
+	dataset: {
+		set(value) {
+			for (const [attribute2, value2] of Object.entries(value)) {
+				this.dataset[attribute2] = processAttribute(value2)
+			}
+		}
+	},
+	shadowRoot: {
+		set(value) {
+			processArgs((this.shadowRoot || this.attachShadow({mode: "open"})), value)
+		}
+	}
+}
+
+const processAttribute = attribute => {
 	if (typeof attribute == "string" || typeof attribute == "number")
 		return attribute
 	else if (attribute && "join" in attribute)
@@ -40,7 +78,12 @@ const parseAttribute = (attribute) => {
 		return JSON.stringify(attribute)
 }
 
+/** Returns a fallback if value is defined */
 const defined = (value, fallback) => typeof value != "undefined" ? value : fallback
+
+/** Recursively finds the last 'is' attribute in a list nested array of objects
+* @param {Array} args
+*/
 const getCustom = args => args.reduce(
 	(current, argument) => Array.isArray(argument)
 		? defined(getCustom(argument), current)
@@ -50,120 +93,161 @@ const getCustom = args => args.reduce(
 	,undefined
 )
 
-const isElement = object => HTMLElement.prototype.isPrototypeOf(object)
+/**
+* @typedef Observable
+* @type {EventTarget|object}
+* @property {any} value
+*/
 
-const isReactive = object => object
+/** Returns whether an object is an observable according to skooma's contract
-	&& (typeof object == "object")
+* @param {any} object
-	&& ("addEventListener" in object)
+* @return {object is Observable}
-	&& ("value" in object)
+*/
+export const isObservable = object => object && object.observable
 
-const toChild = arg => {
+/** Turns an argument into something that can be inserted as a child into a DOM node
-	if (typeof arg == "string" || typeof arg == "number") {
+* @param {any} value
-		return document.createTextNode(arg)
+* @return {Element|Text}
-	} else if (isElement(arg)) {
+*/
-		return arg
+const toElement = value => {
-	} else if (isReactive(arg)) {
+	if (typeof value == "string" || typeof value == "number")
-		return reactiveChild(arg)
+		return document.createTextNode(value.toString())
+	else if (value instanceof Element)
+		return value
+	else if (isObservable(value))
+		return reactiveElement(value)
+}
+
+class ReplaceEvent extends Event {
+	/** @param {Element|Text} next */
+	constructor(next) {
+		super("replace", {bubbles: true, cancelable: true})
+		this.next = next
 	}
 }
 
-const reactiveChild = reactive => {
+class ReplacedEvent extends Event {
-	const ref = new WeakRef(toChild(reactive.value))
+	/** @param {Element|Text} next */
-	reactive.addEventListener("change", () => {
+	constructor(next) {
-		const value = ref.deref()
+		super("replaced")
-		if (value)
+		this.next = next
-			value.replaceWith(reactiveChild(reactive))
+	}
+}
+
+/**
+* @param {Observable} observable
+* @return {Element|Text}
+*/
+export const reactiveElement = observable => {
+	const element = toElement(observable.value)
+	untilDeathDoThemPart(element, observable)
+	const ref = new WeakRef(element)
+	observable.addEventListener("change", () => {
+		const next = reactiveElement(observable)
+		const element = ref.deref()
+		if (element.dispatchEvent(new ReplaceEvent(next)))
+			element.replaceWith(next)
+		element.dispatchEvent(new ReplacedEvent(next))
 	}, {once: true})
-	untilDeathDoThemPart(ref.deref(), reactive)
+	return element
-	return ref.deref()
 }
 
-const specialAttributes = {
+/** A reference to a reactive element that follows it around through changes */
-	value: {
+export class Ref {
-		get: element => element.value,
+	#current
-		set: (element, value) => {
+	/** @param {Element|Text} target A reactive element to follow */
-			element.setAttribute("value", value)
+	constructor(target) {
-			element.value = value
+		this.#current = target
-		},
+		this.follow(target)
-		hook: (element, callback) => { element.addEventListener("input", callback) }
-	},
-	style: {
-		set: (element, value) => { insertStyles(element.style, value) }
-	},
-	dataset: {
-		set: (element, value) => {
-			for (const [attribute2, value2] of Object.entries(value)) {
-				element.dataset[attribute2] = parseAttribute(value2)
-			}
-		}
-	},
-	shadowRoot: {
-		set: (element, value) => {
-			parseArgs((element.shadowRoot || element.attachShadow({mode: "open"})), null, value)
-		}
 	}
+
+	follow(target) {
+		target.addEventListener("replaced", ({next}) => {
+			this.#current = next
+			this.follow(next)
+		})
+	}
+
+	deref() { return this.#current }
 }
 
+/** Set an attribute on an element
+* @param {Element} element
+* @param {string} attribute
+* @param {any} value
+* @param {AbortSignal} [cleanupSignal]
+*/
 const setAttribute = (element, attribute, value, cleanupSignal) => {
 	const special = specialAttributes[attribute]
-	if (isReactive(value))
+	if (isObservable(value))
 		setReactiveAttribute(element, attribute, value)
 	else if (typeof value === "function")
-		element.addEventListener(attribute.replace(/^on[A-Z]/, x => x.charAt(x.length-1).toLowerCase()), value, {signal: cleanupSignal})
+		element.addEventListener(attribute, value, {signal: cleanupSignal})
-	else if (special) {
+	else if (special?.set)
-		special.set(element, value)
+		special.set.call(element, value)
-	}
 	else if (value === true)
 		{if (!element.hasAttribute(attribute)) element.setAttribute(attribute, '')}
 	else if (value === false)
 		element.removeAttribute(attribute)
 	else {
-		element.setAttribute(attribute, parseAttribute(value))
+		element.setAttribute(attribute, processAttribute(value))
 	}
 }
 
-const setReactiveAttribute = (element, attribute, reactive, abortController) => {
+/** Set up a binding between an attribute and an observable
-	untilDeathDoThemPart(element, reactive)
+* @param {Element} element
+* @param {string} attribute
+* @param {Observable} observable
+*/
+const setReactiveAttribute = (element, attribute, observable) => {
+	const multiAbort = new MultiAbortController()
 
-	if (abortController) abortController.abort()
+	observable.addEventListener("change", () => {
-	abortController = new AbortController()
+		multiAbort.abort()
-
+		setAttribute(element, attribute, observable.value, multiAbort.signal)
-	const ref = new WeakRef(element)
+	})
-	setAttribute(element, attribute, reactive.value, abortController.signal)
+	setAttribute(element, attribute, observable.value, multiAbort.signal)
-
-	reactive.addEventListener("change", () => {
-		const element = ref.deref()
-		if (element)
-			setReactiveAttribute(element, attribute, reactive, abortController)
-	}, {once: true})
 
 	const special = specialAttributes[attribute]
-	if (special?.hook) {
+	if (special.hook) {
-		special.hook(element, () => {
+		untilDeathDoThemPart(element, observable)
-			const value = special.get(element, attribute)
+		special.hook.call(element, () => {
-			if (value != reactive.value) reactive.value = value
+			const current = special.get.call(element, attribute)
+			if (current != observable.value) observable.value = current
 		})
 	}
 }
 
-const parseArgs = (element, before, ...args) => {
+/** Processes a list of arguments for an HTML Node
-	if (element.content) element = element.content
+* @param {Element} element
+* @param {Array} args
+*/
+const processArgs = (element, ...args) => {
 	for (const arg of args) if (arg !== empty) {
-		const child = toChild(arg)
+		if (Array.isArray(arg)) {
-		if (child)
+			processArgs(element, ...arg)
-			element.insertBefore(child, before)
+		} else {
-		else if (arg === undefined || arg == null)
+			const child = toElement(arg)
-			console.warn(`An argument of type ${typeof arg} has been ignored`, element)
+			if (child)
-		else if (typeof arg == "function")
+				element.append(child)
-			arg(element)
+			else if (arg === undefined || arg == null)
-		else if ("length" in arg)
+				console.warn(`An argument of type ${typeof arg} has been ignored`, element)
-			parseArgs(element, before, ...arg)
+			else if (typeof arg == "function" && arg.length == 0)
-		else
+				processArgs(element, arg())
-			for (const key in arg)
+			else if (typeof arg == "function")
-				setAttribute(element, key, arg[key])
+				arg(element)
+			else
+				for (const key in arg)
+					setAttribute(element, key, arg[key])
+		}
 	}
 }
 
+/** Creates a new node
+* @param {String} name
+* @param {Array} args
+* @param {Object} options
+*/
 const node = (name, args, options) => {
 	let element
 	const custom = getCustom(args)
@@ -174,11 +258,12 @@ const node = (name, args, options) => {
 		element = document.createElementNS(options.xmlns, name, opts)
 	else
 		element = document.createElement(name, opts)
-	parseArgs(element, null, args)
+	processArgs(element, args)
 	return element
 }
 
 const nameSpacedProxy = (options={}) => new Proxy(Window, {
+	/** @param {string} prop */
 	get: (_target, prop, _receiver) => { return (...args) => node(prop, args, options) },
 	has: (_target, _prop) => true,
 })
@@ -189,31 +274,44 @@ export default html
 
 // Other utility exports
 
-// Wraps an event handler in a function that calls preventDefault on the event
+/** Wraps an event handler in a function that calls preventDefault on the event
+* @param {function(event) : event} fn
+* @return {function(event)}
+*/
 export const handle = fn => event => { event.preventDefault(); return fn(event) }
 
-// Wraps a list of elements in a document fragment
+/** Wraps a list of elements in a document fragment
+* @param {Array<Element|String>} elements
+*/
 export const fragment = (...elements) => {
 	const fragment = new DocumentFragment()
 	for (const element of elements)
-		fragment.append(element)
+		fragment.append(toElement(element))
 	return fragment
 }
 
-// Turns a template literal into document fragment.
+/** Turns a template literal into document fragment.
-// Strings are returned as text nodes.
+* Strings are returned as text nodes.
-// Elements are inserted in between.
+* Elements are inserted in between.
+* @param {Array<String>} literals
+* @param {Array<any>} items
+* @return {DocumentFragment}
+*/
 const textFromTemplate = (literals, items) => {
 	const fragment = new DocumentFragment()
 	for (const key in items) {
 		fragment.append(document.createTextNode(literals[key]))
-		fragment.append(items[key])
+		fragment.append(toElement(items[key]))
 	}
-	fragment.append(document.createTextNode(literals.at(-1)))
+	fragment.append(document.createTextNode(literals[literals.length-1]))
 	return fragment
 }
 
+/**
+* @param {String|Array<String>} data
+* @param {Array<String|Element>} items
+*/
 export const text = (data="", ...items) =>
-	typeof data == "object" && "at" in data
+	Array.isArray(data)
 		? textFromTemplate(data, items)
 		: document.createTextNode(data)

state.js

@@ -1,413 +0,0 @@
-const abortRegistry = new FinalizationRegistry(controller => controller.abort())
-
-const camelToKebab = string => string.replace(/([a-z])([A-Z])/g, (_, a, b) => `${a}-${b.toLowerCase()}`)
-const kebabToCamel = string => string.replace(/([a-z])-([a-z])/g, (_, a, b) => a+b.toUpperCase())
-
-export class ChangeEvent extends Event {
-	#final
-	constructor(...changes) {
-		super('change')
-		this.changes = changes
-	}
-	get final() {
-		if (!this.#final) {
-			this.#final = new Map(this.changes)
-		}
-		return this.#final
-	}
-}
-
-export class SimpleState extends EventTarget {}
-
-export class MapStorage extends Storage {
-	#map = new Map()
-	key(index) {
-		return [...this.#map.keys()][index]
-	}
-	getItem(keyName) {
-		if (this.#map.has(keyName))
-			return this.#map.get(keyName)
-		else
-			return null
-	}
-	setItem(keyName, keyValue) {
-		this.#map.set(keyName, String(keyValue))
-	}
-	removeItem(keyName) {
-		this.#map.delete(keyName)
-	}
-	clear() {
-		this.#map.clear()
-	}
-}
-
-export class State extends SimpleState {
-	#target
-	#options
-	#queue
-	#forwardCache
-	#abortController
-	#nested = new Map()
-	#weakRef = new WeakRef(this)
-
-	static isState(object) { return SimpleState.prototype.isPrototypeOf(object) }
-
-	constructor(target={}, options={}) {
-		super()
-
-		this.#abortController = new AbortController
-		abortRegistry.register(this, this.#abortController)
-
-		this.#options = options
-		this.#target = target
-		this.values = new Proxy(target, {
-			set: (_target, prop, value) => {
-				const old = this.get(prop)
-				if (old !== value) {
-					this.emit(prop, value)
-					if (this.#options.shallow) {
-						if (State.isState(old)) this.disown(prop, old)
-						if (State.isState(value)) this.adopt(prop, value)
-					}
-					this.set(prop, value)
-				}
-				return true
-			},
-			get: (_target, prop) => this.get(prop),
-		})
-
-		this.addEventListener
-
-		// Try running a "<name>Changed" method for every changed property
-		// Can be disabled to maybe squeeze out some performance
-		if (options.methods ?? true) {
-			this.addEventListener("change", ({final}) => {
-				final.forEach((value, prop) => {
-					if (`${prop}Changed` in this) this[`${prop}Changed`](value)
-				})
-			})
-		}
-	}
-
-	// When you only need one value, you can skip the proxy.
-	set value(value) { this.values.value = value }
-	get value() { return this.values.value }
-
-	adopt(prop, state) {
-		let handlers = this.#nested.get(state)
-		if (!handlers) {
-			// Actual adoption
-			handlers = new Map()
-			this.#nested.set(state, handlers)
-		}
-		const ref = this.#weakRef
-		const handler = () => ref.deref()?.emit(prop, state)
-
-		handlers.set(prop, handler)
-		state.addEventListener("change", handler, {signal: this.#abortController.signal})
-	}
-	disown(prop, state) {
-		const handlers = this.#nested.get(state)
-		const handler = handlers.get(prop)
-		state.removeEventListener("change", handler)
-		handlers.delete(prop)
-		if (handlers.size == 0) {
-			this.#nested.delete(state)
-		}
-	}
-
-	// Anounces that a prop has changed
-	emit(prop, value) {
-		if (this.#options.defer ?? true) {
-			if (!this.#queue) {
-				this.#queue = []
-				queueMicrotask(() => {
-					this.dispatchEvent(new ChangeEvent(...this.#queue))
-					this.#queue = undefined
-				})
-			}
-			this.#queue.push([prop, value])
-		} else {
-			this.dispatchEvent(new ChangeEvent([prop, value]))
-		}
-	}
-
-	forward(property="value", fallback) {
-		if (!this.#forwardCache) this.#forwardCache = new Map()
-		const cached = this.#forwardCache.get(property)?.deref()
-		if (cached) {
-			return cached
-		} else {
-			const forwarded = new ForwardState(this, property, fallback)
-			const ref = new WeakRef(forwarded)
-			this.#forwardCache.set(property, ref)
-			forwardFinalizationRegistry.register(forwarded, [this.#forwardCache, property])
-			return forwarded
-		}
-	}
-
-	set(...args) {
-		if (args.length === 1) return this.set("value", ...args)
-
-		const [prop, value] = args
-		this.#target[prop] = value
-	}
-
-	get(...args) {
-		if (args.length === 0) return this.get("value")
-
-		const prop = args[0]
-		return this.#target[prop]
-	}
-
-	subscribe(prop, callback) {
-		if (!callback) return this.subscribe("value", prop)
-
-		const controller = new AbortController()
-		this.addEventListener("change", ({final}) => {
-			if (final.has(prop)) return callback(final.get(prop))
-		}, {signal: controller.signal})
-		callback(this.value)
-		return () => controller.abort()
-	}
-
-	// Backwards compatibility
-	get proxy() { return this.values }
-}
-
-const forwardFinalizationRegistry = new FinalizationRegistry(([cache, name]) => {
-	cache.remove(name)
-})
-
-export class ForwardState extends SimpleState {
-	#backend
-	#property
-	#fallback
-
-	constructor(backend, property, fallback) {
-		super()
-		this.#backend = backend
-		this.#property = property
-		this.#fallback = fallback
-		const ref = new WeakRef(this)
-		const abortController = new AbortController()
-		backend.addEventListener("change", event => {
-			const state = ref.deref()
-			if (state) {
-				const relevantChanges = event.changes
-					.filter(([name]) => name === property)
-					.map(([_, value]) => ["value", value])
-				if (relevantChanges.length > 0)
-					state.dispatchEvent(new ChangeEvent(...relevantChanges))
-			} else {
-				abortController.abort()
-			}
-		}, {signal: abortController.signal})
-	}
-
-	get value() { return this.#backend.values[this.#property] ?? this.#fallback }
-	set value(value) { this.#backend.values[this.#property] = value }
-}
-
-class StorageChangeEvent extends Event {
-	constructor(storage, key, value, targetState) {
-		super("storagechange")
-		this.storageArea = storage
-		this.key = key
-		this.newValue = value
-		this.targetState = targetState
-	}
-}
-
-export class StoredState extends State {
-	#storage
-
-	constructor(init, options={}) {
-		super({}, options)
-		this.#storage = options.storage ?? localStorage ?? new MapStorage()
-
-		// Initialise storage from defaults
-		for (const [prop, value] of Object.entries(init)) {
-			if (this.#storage[prop] === undefined)
-				this.set(prop, value)
-		}
-
-		// Emit change events for any changed keys
-		for (let i=0; i<this.#storage.length; i++) {
-			const key = this.#storage.key(i)
-			const value = this.#storage[key]
-			if (value !== JSON.stringify(init[key]))
-				this.emit(key, value)
-		}
-
-		// Listen for changes from other windows
-		const handler = event => {
-			if (event.targetState !== this && event.storageArea == this.#storage) {
-				this.emit(event.key, JSON.parse(event.newValue))
-			}
-		}
-		addEventListener("storage", handler)
-		addEventListener("storagechange", handler)
-	}
-
-	set(prop, value) {
-		const json = JSON.stringify(value)
-		dispatchEvent(new StorageChangeEvent(this.#storage, prop, json, this))
-		this.#storage[prop] = json
-	}
-
-	get(prop) {
-		const value = this.#storage[prop]
-		return value && JSON.parse(value)
-	}
-}
-
-const attributeObserver = new MutationObserver(mutations => {
-	for (const {type, target, attributeName: name} of mutations) {
-		if (type == "attributes") {
-			const next = target.getAttribute(name)
-			const camelName = kebabToCamel(name)
-			if (String(target.state.values[camelName]) !== next)
-				target.state.values[camelName] = next
-		}
-	}
-})
-
-export const component = (generator, name) => {
-	name = name ?? camelToKebab(generator.name)
-	const Element = class extends HTMLElement{
-		constructor() {
-			super()
-			this.state = new State(Object.fromEntries([...this.attributes].map(attribute => [kebabToCamel(attribute.name), attribute.value])))
-			this.state.addEventListener("change", event => {
-				for (const [name, value] of event.changes) {
-					const kebabName = camelToKebab(name)
-					if (this.getAttribute(kebabName) !== String(value))
-						this.setAttribute(kebabName, value)
-				}
-			})
-			attributeObserver.observe(this, {attributes: true})
-			this.replaceChildren(generator(this))
-		}
-	}
-	customElements.define(name, Element)
-	return Element;
-}
-
-class ComposedState extends SimpleState {
-	#func
-	#states
-	#options
-
-	constructor(func, options, ...states) {
-		super()
-
-		this.#func = func
-		this.#states = states
-		this.#options = options
-
-		const abortController = new AbortController()
-		abortRegistry.register(this, abortController)
-		const ref = new WeakRef(this)
-
-		states.forEach(state => {
-			state.addEventListener("change", event => {
-				const value = event.final.get("value")
-				if (value) ref.deref()?.scheduleUpdate()
-			}, {signal: abortController.signal})
-		})
-
-		this.update()
-	}
-
-	#microtaskQueued
-	scheduleUpdate() {
-		if (this.#options.defer) {
-			if (!this.#microtaskQueued) {
-				queueMicrotask(() => {
-					this.#microtaskQueued = false
-					this.update()
-				})
-			}
-			this.#microtaskQueued = true
-		} else {
-			this.update()
-		}
-	}
-
-	update() {
-		this.value = this.#func(...this.#states.map(state => state.value))
-		this.dispatchEvent(new ChangeEvent([["value", this.value]]))
-	}
-}
-
-export const compose = func => (...states) => new ComposedState(func, {defer: true}, ...states)
-
-const eventName = "mutation"
-
-class MutationEvent extends Event {
-	constructor() {
-		super(eventName, {bubbles: true})
-	}
-}
-
-const mutationObserver = new MutationObserver(mutations => {
-	for (const mutation of mutations) {
-		mutation.target.dispatchEvent(new MutationEvent())
-	}
-})
-
-export class DOMState extends SimpleState {
-	#target
-	#defer
-	#getValue
-	#equal
-
-	#old
-	#changedValue = false
-
-	constructor(target, options) {
-		super()
-		this.#defer = options.defer ?? false
-		this.#target = target
-		this.#getValue = options.get ?? (target => target.value)
-		this.#equal = options.equal ?? ((a, b) => a===b)
-
-		this.#old = this.#getValue(target)
-
-		const controller = new AbortController()
-		target.addEventListener(eventName, event=>{this.update(event)}, {signal: controller.signal})
-
-		abortRegistry.register(this, controller)
-		mutationObserver.observe(target, {
-			attributes: true,
-			childList: true,
-			characterData: true,
-			subtree: true,
-		})
-	}
-
-	get value() { return this.#old }
-
-	update() {
-		const current = this.#getValue(this.#target)
-
-		if (this.#equal(this.#old, current)) return
-
-		this.#old = current
-
-		if (this.#defer) {
-			if (!this.#changedValue) {
-				queueMicrotask(() => {
-					this.#changedValue = false
-					this.dispatchEvent(new ChangeEvent(["value", this.#changedValue]))
-				})
-				this.#changedValue = current
-			}
-		} else {
-			this.dispatchEvent(new ChangeEvent(["value", current]))
-		}
-	}
-}
-
-export default State