Remove valueKey from StoredState

This makes the State class fully compatible with svelte stores

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()
+
+export 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

package.json

@@ -1,6 +1,6 @@
 {
 	"name": "skooma",
-	"version": "1.4.0",
+	"version": "1.7.0",
 	"author": "darkwiiplayer",
 	"license": "Unlicense",
 	"main": "skooma.js",

readme.md

@@ -1,12 +1,12 @@
 # Skooma
 
+A functional-friendly helper library for procedural DOM generation and
+templating.
+
 ```js
 import {html} from "skooma.js"
 ```
 
-A functional-friendly helper library for procedural DOM generation and
-templating.
-
 ## Overview
 
 ```js

skooma.js

@@ -10,6 +10,7 @@ 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)) {
@@ -49,6 +50,8 @@ const getCustom = args => args.reduce(
 	,undefined
 )
 
+const isElement = object => HTMLElement.prototype.isPrototypeOf(object)
+
 const isReactive = object => object
 	&& (typeof object == "object")
 	&& ("addEventListener" in object)
@@ -57,7 +60,7 @@ const isReactive = object => object
 const toChild = arg => {
 	if (typeof arg == "string" || typeof arg == "number") {
 		return document.createTextNode(arg)
-	} else if ("nodeName" in arg) {
+	} else if (isElement(arg)) {
 		return arg
 	} else if (isReactive(arg)) {
 		return reactiveChild(arg)
@@ -182,11 +185,12 @@ const nameSpacedProxy = (options={}) => new Proxy(Window, {
 
 export const html = nameSpacedProxy({nameFilter: name => name.replace(/([a-z])([A-Z])/g, "$1-$2").toLowerCase()})
 export const svg = nameSpacedProxy({xmlns: "http://www.w3.org/2000/svg"})
+export default html
 
 // Other utility exports
 
 // Wraps an event handler in a function that calls preventDefault on the event
-export const handle = fn => event => { fn(event); event.preventDefault() }
+export const handle = fn => event => { event.preventDefault(); return fn(event) }
 
 // Wraps a list of elements in a document fragment
 export const fragment = (...elements) => {

state.js

@@ -1,3 +1,8 @@
+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) {
@@ -12,6 +17,8 @@ export class ChangeEvent extends Event {
 	}
 }
 
+export class SimpleState extends EventTarget {}
+
 export class MapStorage extends Storage {
 	#map = new Map()
 	key(index) {
@@ -34,20 +41,36 @@ export class MapStorage extends Storage {
 	}
 }
 
-export class State extends EventTarget {
+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.proxy = new Proxy(target, {
+		this.values = new Proxy(target, {
 			set: (_target, prop, value) => {
-				this.emit(prop, value)
-				this.set(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),
@@ -67,8 +90,31 @@ export class State extends EventTarget {
 	}
 
 	// When you only need one value, you can skip the proxy.
-	set value(value) { this.proxy.value = value }
-	get value() { return this.proxy.value }
+	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) {
@@ -88,32 +134,52 @@ export class State extends EventTarget {
 
 	forward(property="value", fallback) {
 		if (!this.#forwardCache) this.#forwardCache = new Map()
-		const cached = this.#forwardCache.get(property).deref()
+		const cached = this.#forwardCache.get(property)?.deref()
 		if (cached) {
 			return cached
 		} else {
 			const forwarded = new ForwardState(this, property, fallback)
-			ref = new Weakref(forwarded)
+			const ref = new WeakRef(forwarded)
 			this.#forwardCache.set(property, ref)
 			forwardFinalizationRegistry.register(forwarded, [this.#forwardCache, property])
 			return forwarded
 		}
 	}
 
-	set(prop, value) {
+	set(...args) {
+		if (args.length === 1) return this.set("value", ...args)
+
+		const [prop, value] = args
 		this.#target[prop] = value
 	}
 
-	get(prop) {
+	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 EventTarget {
+export class ForwardState extends SimpleState {
 	#backend
 	#property
 	#fallback
@@ -128,20 +194,22 @@ export class ForwardState extends EventTarget {
 		backend.addEventListener("change", event => {
 			const state = ref.deref()
 			if (state) {
-				const relevantChanges = event.changes.filter(([name]) => name === property)
+				const relevantChanges = event.changes
+					.filter(([name]) => name === property)
+					.map(([_, value]) => ["value", value])
 				if (relevantChanges.length > 0)
-					state.dispatchEvent(new ChangeEvent(relevantChanges))
+					state.dispatchEvent(new ChangeEvent(...relevantChanges))
 			} else {
 				abortController.abort()
 			}
 		}, {signal: abortController.signal})
 	}
 
-	get value() { return this.#backend.proxy[this.#property] ?? this.#fallback }
-	set value(value) { this.#backend.proxy[this.#property] = value }
+	get value() { return this.#backend.values[this.#property] ?? this.#fallback }
+	set value(value) { this.#backend.values[this.#property] = value }
 }
 
-export class StorageChangeEvent extends Event {
+class StorageChangeEvent extends Event {
 	constructor(storage, key, value, targetState) {
 		super("storagechange")
 		this.storageArea = storage
@@ -153,16 +221,13 @@ export class StorageChangeEvent extends Event {
 
 export class StoredState extends State {
 	#storage
-	#valueKey
 
 	constructor(init, options={}) {
 		super({}, options)
 		this.#storage = options.storage ?? localStorage ?? new MapStorage()
-		this.#valueKey = options.key ?? 'value'
 
 		// Initialise storage from defaults
-		for (let [prop, value] of Object.entries(init)) {
-			if (prop === 'value') prop = this.#valueKey
+		for (const [prop, value] of Object.entries(init)) {
 			if (this.#storage[prop] === undefined)
 				this.set(prop, value)
 		}
@@ -178,9 +243,7 @@ export class StoredState extends State {
 		// Listen for changes from other windows
 		const handler = event => {
 			if (event.targetState !== this && event.storageArea == this.#storage) {
-				let prop = event.key
-				if (prop === this.#valueKey) prop = 'value'
-				this.emit(prop, JSON.parse(event.newValue))
+				this.emit(event.key, JSON.parse(event.newValue))
 			}
 		}
 		addEventListener("storage", handler)
@@ -188,14 +251,12 @@ export class StoredState extends State {
 	}
 
 	set(prop, value) {
-		if (prop == "value") prop = this.#valueKey
 		const json = JSON.stringify(value)
 		dispatchEvent(new StorageChangeEvent(this.#storage, prop, json, this))
 		this.#storage[prop] = json
 	}
 
 	get(prop) {
-		if (prop == "value") prop = this.#valueKey
 		const value = this.#storage[prop]
 		return value && JSON.parse(value)
 	}
@@ -203,21 +264,150 @@ export class StoredState extends State {
 
 const attributeObserver = new MutationObserver(mutations => {
 	for (const {type, target, attributeName: name} of mutations) {
-		if (type == "attributes")
-			target.state.proxy[name] = target.getAttribute(name)
+		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 ?? generator.name.replace(/([a-z])([A-Z])/g, (_, a, b) => `${a}-${b.toLowerCase()}`)
-	customElements.define(name, class extends HTMLElement{
+	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) {
+					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)
+	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