Add domState class

domLense.js

@@ -0,0 +1,85 @@
+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 })
+	}
+}
+
+const childObserver = new ChildObserver()
+
+const lense = (methods, extra) => {
+	if (extra) return lense(extra)(methods)
+
+	const traps = {
+		get(target, prop) {
+			if (prop === "length") {
+				return target.children.length
+			} else if (prop === Symbol.iterator) {
+				return function*() {
+					for (const child of target.children) {
+						yield methods.get(child)
+					}
+				}
+			} else if (prop.match?.call(prop, /^[0-9]+$/)) {
+				const child = target.children[prop]
+				if (child) return methods.get(child)
+				return child
+			} else {
+				return Array.prototype[prop]
+			}
+		},
+		set(target, prop, value) {
+			if (prop.match?.call(prop, /^[0-9]+$/)) {
+				const child = target.children[prop]
+				if (child) {
+					methods.set(child, value)
+					return true
+				} else {
+					for (let i = target.children.length; i < Number(prop); i++) {
+						target.appendChild(methods.new(undefined))
+					}
+					const element = methods.new(value)
+					target.appendChild(element)
+					if (methods.get(element) !== value)
+						methods.set(element, value)
+					return true
+				}
+			} else if (prop == "length") {
+				if (value == target.children.length)
+					return true
+				else
+					return false
+			}
+		},
+		deleteProperty(target, prop) {
+			if (prop.match?.call(prop, /^[0-9]+$/)) {
+				const child = target.children[prop]
+				if (child) child.remove()
+				return true
+			}
+		},
+		has(target, prop) {
+			return (prop === Symbol.iterator) || (prop in target.children) || (prop in Array.prototype)
+		}
+	}
+
+	return element => {
+		const proxy = 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

state.js

@@ -1,5 +1,8 @@
 export 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) {
@@ -250,26 +253,28 @@ const attributeObserver = new MutationObserver(mutations => {
 	for (const {type, target, attributeName: name} of mutations) {
 		if (type == "attributes") {
 			const next = target.getAttribute(name)
-			if (String(target.state.proxy[name]) !== next)
-				target.state.proxy[name] = next
+			const camelName = kebabToCamel(name)
+			if (String(target.state.proxy[camelName]) !== next)
+				target.state.proxy[camelName] = next
 		}
 	}
 })
 
 export const component = (generator, name) => {
-	name = name ?? generator.name.replace(/([a-z])([A-Z])/g, (_, a, b) => `${a}-${b.toLowerCase()}`)
+	name = name ?? camelToKebab(generator.name)
 	const Element = class extends HTMLElement{
 		constructor() {
 			super()
-			this.state = new State(Object.fromEntries([...this.attributes].map(attribute => [attribute.name, attribute.value])))
+			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) {
-					if (this.getAttribute(name) !== String(value))
-						this.setAttribute(name, value)
+					const kebabName = camelToKebab(name)
+					if (this.getAttribute(kebabName) !== String(value))
+						this.setAttribute(kebabName, value)
 				}
 			})
 			attributeObserver.observe(this, {attributes: true})
-			this.replaceChildren(generator(this.state))
+			this.replaceChildren(generator(this))
 		}
 	}
 	customElements.define(name, Element)
@@ -325,4 +330,62 @@ class ComposedState extends SimpleState {
 
 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 {
+	#old
+	#options
+	#changedValue = false
+
+	constructor(target, value, options) {
+		super()
+		this.#options = options
+		this.#old = [...value]
+		this.value = value
+		const controller = new AbortController()
+		mutationObserver.observe(target, {
+			attributes: true,
+			childList: true,
+			characterData: true,
+			subtree: true,
+		})
+		target.addEventListener(eventName, event=>{this.update(event)}, {signal: controller.signal})
+		abortRegistry.register(this, controller)
+	}
+
+	update() {
+		const current = [...this.value]
+		if (current.length === this.#old.length) {
+			for (const idx in current) {
+				if (current[idx] !== this.#old[idx]) break
+			}
+			return
+		}
+		this.#old = current
+		if (this.#options?.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