Add Ref class to follow reactive elements

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

domProxy.js

@@ -1,19 +1,5 @@
-class ChildObserver extends MutationObserver {
-	constructor() {
-		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 })
-	}
-}
-
-export const lense = (methods, extra) => {
-	if (extra) return lense(extra)(methods)
+export const domArray = (methods, extra) => {
+	if (extra) return domArray(extra)(methods)
 
 	const traps = {
 		get(target, prop) {
@@ -69,9 +55,20 @@ export const lense = (methods, extra) => {
 	}
 
 	return element => {
-		if (!(element instanceof Element)) throw(new Error("Creating domLense on non-element"))
+		if (!(element instanceof Element)) throw(new Error("Creating domArray on non-element"))
 		return new Proxy(element, traps)
 	}
 }
 
-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

@@ -12,63 +12,37 @@ class MultiAbortController {
 	abort() { this.#controller.abort(); this.#controller = new AbortController() }
 }
 
+/** 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())
 
-const insertStyles = (rule, styles) => {
-	for (const [key, value] of Object.entries(styles))
+/**
+* @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")
-			rule.removeProperty(snakeToCSS(key))
+			style.removeProperty(snakeToCSS(key))
 	else
-		rule.setProperty(snakeToCSS(key), value.toString())
+		style.setProperty(snakeToCSS(key), value.toString())
 }
 
-const processAttribute = (attribute) => {
-	if (typeof attribute == "string" || typeof attribute == "number")
-		return attribute
-	else if (attribute && "join" in attribute)
-		return attribute.join(" ")
-	else
-		return JSON.stringify(attribute)
-}
-
-const defined = (value, fallback) => typeof value != "undefined" ? value : fallback
-const getCustom = args => args.reduce(
-	(current, argument) => Array.isArray(argument)
-		? defined(getCustom(argument), current)
-		: (argument && typeof argument == "object")
-		? defined(argument.is, current)
-		: current
-	,undefined
-)
-
-export const isReactive = object => object
-	&& typeof object == "object"
-	&& !(object instanceof HTMLElement)
-	&& object.subscribe
-
-const toChild = arg => {
-	if (typeof arg == "string" || typeof arg == "number")
-		return document.createTextNode(arg)
-	else if (arg instanceof HTMLElement)
-		return arg
-	else if (isReactive(arg))
-		return reactiveChild(arg)
-}
-
-const reactiveChild = reactive => {
-	let ref
-	const abort = reactive.subscribe(value => {
-		if (ref && !ref.deref()) return abort()
-		const child = toChild(value) ?? document.createComment("Placeholder for reactive content")
-		untilDeathDoThemPart(child, reactive)
-		if (ref) ref.deref().replaceWith(child)
-		ref = new WeakRef(child)
-	})
-	return ref.deref()
-}
+/** @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 },
@@ -95,9 +69,117 @@ const specialAttributes = {
 	}
 }
 
+const processAttribute = attribute => {
+	if (typeof attribute == "string" || typeof attribute == "number")
+		return attribute
+	else if (attribute && "join" in attribute)
+		return attribute.join(" ")
+	else
+		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)
+		: (argument && typeof argument == "object")
+		? defined(argument.is, current)
+		: current
+	,undefined
+)
+
+/**
+* @typedef Observable
+* @type {EventTarget|object}
+* @property {any} value
+*/
+
+/** Returns whether an object is an observable according to skooma's contract
+* @param {any} object
+* @return {object is Observable}
+*/
+export const isObservable = object => object && object.observable
+
+/** Turns an argument into something that can be inserted as a child into a DOM node
+* @param {any} value
+* @return {Element|Text}
+*/
+const toElement = value => {
+	if (typeof value == "string" || typeof value == "number")
+		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
+	}
+}
+
+class ReplacedEvent extends Event {
+	/** @param {Element|Text} next */
+	constructor(next) {
+		super("replaced")
+		this.next = next
+	}
+}
+
+/**
+* @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})
+	return element
+}
+
+/** A reference to a reactive element that follows it around through changes */
+export class Ref {
+	#current
+	/** @param {Element|Text} target A reactive element to follow */
+	constructor(target) {
+		this.#current = target
+		this.follow(target)
+	}
+
+	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, value, {signal: cleanupSignal})
@@ -112,32 +194,40 @@ const setAttribute = (element, attribute, value, cleanupSignal) => {
 	}
 }
 
-// (Two-way) binding between an attribute and a state container
-const setReactiveAttribute = (element, attribute, reactive) => {
-	untilDeathDoThemPart(element, reactive)
+/** Set up a binding between an attribute and an observable
+* @param {Element} element
+* @param {string} attribute
+* @param {Observable} observable
+*/
+const setReactiveAttribute = (element, attribute, observable) => {
 	const multiAbort = new MultiAbortController()
-	let old
-	reactive.subscribe(value => {
-		old = value
+
+	observable.addEventListener("change", () => {
 		multiAbort.abort()
-		setAttribute(element, attribute, value, multiAbort.signal)
+		setAttribute(element, attribute, observable.value, multiAbort.signal)
 	})
+	setAttribute(element, attribute, observable.value, multiAbort.signal)
+
 	const special = specialAttributes[attribute]
-	if (special?.hook && reactive.set) {
+	if (special.hook) {
+		untilDeathDoThemPart(element, observable)
 		special.hook.call(element, () => {
-			const value = special.get.call(element, attribute)
-			if (value != old) reactive.set(value)
+			const current = special.get.call(element, attribute)
+			if (current != observable.value) observable.value = current
 		})
 	}
 }
 
+/** Processes a list of arguments for an HTML Node
+* @param {Element} element
+* @param {Array} args
+*/
 const processArgs = (element, ...args) => {
-	if (element.content) element = element.content
 	for (const arg of args) if (arg !== empty) {
-		if (arg instanceof Array) {
+		if (Array.isArray(arg)) {
 			processArgs(element, ...arg)
 		} else {
-			const child = toChild(arg)
+			const child = toElement(arg)
 			if (child)
 				element.append(child)
 			else if (arg === undefined || arg == null)
@@ -153,6 +243,11 @@ const processArgs = (element, ...args) => {
 	}
 }
 
+/** Creates a new node
+* @param {String} name
+* @param {Array} args
+* @param {Object} options
+*/
 const node = (name, args, options) => {
 	let element
 	const custom = getCustom(args)
@@ -168,6 +263,7 @@ const node = (name, args, options) => {
 }
 
 const nameSpacedProxy = (options={}) => new Proxy(Window, {
+	/** @param {string} prop */
 	get: (_target, prop, _receiver) => { return (...args) => node(prop, args, options) },
 	has: (_target, _prop) => true,
 })
@@ -178,31 +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.
-// Strings are returned as text nodes.
-// Elements are inserted in between.
+/** Turns a template literal into document fragment.
+* Strings are returned as text nodes.
+* 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

@@ -1,453 +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
-	#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 SimpleState extends EventTarget {
-	#synchronous
-	#queue
-	#nested = new Map()
-	#weakRef = new WeakRef(this)
-	#abortController = new AbortController
-
-	constructor({synchronous, methods}={}) {
-		super()
-		this.#synchronous = !!synchronous
-		abortRegistry.register(this, this.#abortController)
-
-		// Try running a "<name>Changed" method for every changed property
-		// Can be disabled to maybe squeeze out some performance
-		if (methods ?? true) {
-			this.addEventListener("change", ({final}) => {
-				final.forEach((value, prop) => {
-					if (`${prop}Changed` in this) this[`${prop}Changed`](value)
-				})
-			})
-		}
-	}
-
-	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()
-	}
-
-	get() { return this.value }
-	set(value) { this.value = value }
-
-	emit(property, from, to, options={}) {
-		const change = {property, from, to, ...options}
-		if (!this.synchronous) {
-			if (!this.#queue) {
-				this.#queue = []
-				queueMicrotask(() => {
-					this.dispatchEvent(new ChangeEvent(...this.#queue))
-					this.#queue = undefined
-				})
-			}
-			this.#queue.push(change)
-		} else {
-			this.dispatchEvent(new ChangeEvent([change]))
-		}
-	}
-
-	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, state, {state: true})
-
-		handlers.set(prop, handler)
-		state.addEventListener("change", handler, {signal: this.ignal})
-	}
-
-	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)
-		}
-	}
-
-	get signal() { return this.#abortController.signal }
-	get synchronous() { return this.#synchronous }
-}
-
-export class State extends SimpleState {
-	#target
-	#shallow
-
-	static isState(object) { return SimpleState.prototype.isPrototypeOf(object) }
-
-	constructor(target={}, {shallow, ...options}={}) {
-		super(options)
-
-		this.#shallow = !!shallow
-		this.#target = target
-		this.values = new Proxy(target, {
-			set: (_target, prop, value) => {
-				const old = this.get(prop)
-				if (old !== value) {
-					this.emit(prop, old, value)
-					if (this.#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),
-		})
-	}
-
-	forward(property="value", methods) {
-		return new ForwardState(this, property, methods)
-	}
-
-	set(prop, value) {
-		if (arguments.length === 1) return this.set("value", prop)
-		this.#target[prop] = value
-	}
-
-	get(prop="value") {
-		return this.#target[prop]
-	}
-
-	set value(value) { this.set(value) }
-	get value() { return this.get() }
-}
-
-export class ForwardState extends SimpleState {
-	#backend
-	#property
-	#methods
-
-	constructor(backend, property, methods = {}) {
-		super()
-		this.#methods = methods
-		this.#backend = backend
-		this.#property = property
-
-		const ref = new WeakRef(this)
-		const abortController = new AbortController()
-		abortRegistry.register(this, abortController)
-		backend.addEventListener("change", event => {
-			const state = ref.deref()
-			if (state) {
-				let relevantChanges = event.changes
-					.filter(({property: name}) => name === property)
-				const get = methods.get
-				if (methods.get) {
-					relevantChanges = relevantChanges.map(
-						({from, to}) => ({property: "value", from: get(from), to: get(to)})
-					)
-				} else {
-					relevantChanges = relevantChanges.map(
-						({from, to}) => ({property: "value", from, to})
-					)
-				}
-				if (relevantChanges.length > 0)
-					state.dispatchEvent(new ChangeEvent(...relevantChanges))
-			} else {
-				abortController.abort()
-			}
-		}, {signal: abortController.signal})
-	}
-
-	get value() {
-		const methods = this.#methods
-		if (methods.get) {
-			return methods.get(this.#backend.values[this.#property])
-		} else {
-			return this.#backend.values[this.#property]
-		}
-	}
-
-	set value(value) {
-		const methods = this.#methods
-		if (methods.set) {
-			this.#backend.values[this.#property] = methods.set(value)
-		} else {
-			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 = (name, generator, methods) => {
-	if (typeof name === "function") {
-		methods = generator
-		generator = 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 {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})
-			this.replaceChildren(generator.call(this, this.state))
-		}
-	}
-	if (methods) {
-		Object.defineProperties(Element.prototype, Object.getOwnPropertyDescriptors(methods))
-	}
-	customElements.define(name, Element)
-	return Element;
-}
-
-class ComposedState extends SimpleState {
-	#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", event => {
-				const value = event.final.get("value")
-				if (value) 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.dispatchEvent(new ChangeEvent(change))
-	}
-}
-
-export const compose = func => (...states) => new ComposedState(func, {}, ...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
-	#getValue
-	#equal
-
-	#old
-	#changedValue = false
-
-	constructor(target, options) {
-		super(options)
-		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.synchronous) {
-			this.dispatchEvent(new ChangeEvent(["value", current]))
-		} else {
-			if (!this.#changedValue) {
-				queueMicrotask(() => {
-					this.#changedValue = false
-					this.dispatchEvent(new ChangeEvent(["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()
-	}
-}
-
-export default State