Refactor

Since States are now also valid svelte stores, skooma now uses that API
to decide whether something is an observable state and to interact with
it.

domLense.js

@@ -12,8 +12,6 @@ class ChildObserver extends MutationObserver {
 	}
 }
 
-const childObserver = new ChildObserver()
-
 export const lense = (methods, extra) => {
 	if (extra) return lense(extra)(methods)
 
@@ -24,12 +22,12 @@ 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]+$/)) {
 				const child = target.children[prop]
-				if (child) return methods.get(child)
+				if (child) return methods.get.call(child)
 				return child
 			} else {
 				return Array.prototype[prop]
@@ -39,7 +37,7 @@ export const lense = (methods, extra) => {
 			if (prop.match?.call(prop, /^[0-9]+$/)) {
 				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 +45,8 @@ export const lense = (methods, extra) => {
 					}
 					const element = methods.new(value)
 					target.appendChild(element)
-					if (methods.get(element) !== value)
-						methods.set(element, value)
+					if (methods.get.call(element) !== value)
+						methods.set.call(element, value)
 					return true
 				}
 			} else if (prop == "length") {
@@ -71,14 +69,8 @@ export const lense = (methods, extra) => {
 	}
 
 	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
+		if (!(element instanceof Element)) throw(new Error("Creating domLense on non-element"))
+		return new Proxy(element, traps)
 	}
 }
 

skooma.js

@@ -1,37 +1,30 @@
-/*
-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)) {
-		weakReferences.set(referrer, new Set())
-	}
+	if (!weakReferences.has(referrer)) weakReferences.set(referrer, new Set())
 	weakReferences.get(referrer).add(reference)
 }
 
+// Like AbortController, but resets after each abort
+class MultiAbortController {
+	#controller = new AbortController()
+	get signal() { return this.#controller.signal }
+	abort() { this.#controller.abort(); this.#controller = new AbortController() }
+}
+
 export const empty = Symbol("Explicit empty argument for Skooma")
 
-const keyToPropName = key => key.replace(/^[A-Z]/, a => "-"+a).replace(/[A-Z]/g, a => '-'+a.toLowerCase())
+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))
 		if (typeof value == "undefined")
-			rule.removeProperty(keyToPropName(key))
+			rule.removeProperty(snakeToCSS(key))
 	else
-		rule.setProperty(keyToPropName(key), value.toString())
+		rule.setProperty(snakeToCSS(key), value.toString())
 }
 
-const parseAttribute = (attribute) => {
+const processAttribute = (attribute) => {
 	if (typeof attribute == "string" || typeof attribute == "number")
 		return attribute
 	else if (attribute && "join" in attribute)
@@ -50,56 +43,54 @@ const getCustom = args => args.reduce(
 	,undefined
 )
 
-const isElement = object => HTMLElement.prototype.isPrototypeOf(object)
-
-const isReactive = object => object
-	&& (typeof object == "object")
-	&& ("addEventListener" in object)
-	&& ("value" in object)
+export const isReactive = object => object
+	&& typeof object == "object"
+	&& !(object instanceof HTMLElement)
+	&& object.subscribe
 
 const toChild = arg => {
-	if (typeof arg == "string" || typeof arg == "number") {
+	if (typeof arg == "string" || typeof arg == "number")
 		return document.createTextNode(arg)
-	} else if (isElement(arg)) {
+	else if (arg instanceof HTMLElement)
 		return arg
-	} else if (isReactive(arg)) {
+	else if (isReactive(arg))
 		return reactiveChild(arg)
-	}
 }
 
 const reactiveChild = reactive => {
-	const ref = new WeakRef(toChild(reactive.value))
-	reactive.addEventListener("change", () => {
-		const value = ref.deref()
-		if (value)
-			value.replaceWith(reactiveChild(reactive))
-	}, {once: true})
-	untilDeathDoThemPart(ref.deref(), 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()
 }
 
 const specialAttributes = {
 	value: {
-		get: element => element.value,
-		set: (element, value) => {
-			element.setAttribute("value", value)
-			element.value = value
+		get() { return this.value },
+		set(value) {
+			this.setAttribute("value", value)
+			this.value = value
 		},
-		hook: (element, callback) => { element.addEventListener("input", callback) }
+		hook(callback) { this.addEventListener("input", callback) }
 	},
 	style: {
-		set: (element, value) => { insertStyles(element.style, value) }
+		set(value) { insertStyles(this.style, value) }
 	},
 	dataset: {
-		set: (element, value) => {
+		set(value) {
 			for (const [attribute2, value2] of Object.entries(value)) {
-				element.dataset[attribute2] = parseAttribute(value2)
+				this.dataset[attribute2] = processAttribute(value2)
 			}
 		}
 	},
 	shadowRoot: {
-		set: (element, value) => {
-			parseArgs((element.shadowRoot || element.attachShadow({mode: "open"})), null, value)
+		set(value) {
+			processArgs((this.shadowRoot || this.attachShadow({mode: "open"})), value)
 		}
 	}
 }
@@ -109,59 +100,57 @@ const setAttribute = (element, attribute, value, cleanupSignal) => {
 	if (isReactive(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})
-	else if (special) {
-		special.set(element, value)
-	}
+		element.addEventListener(attribute, value, {signal: cleanupSignal})
+	else if (special?.set)
+		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) => {
+// (Two-way) binding between an attribute and a state container
+const setReactiveAttribute = (element, attribute, reactive) => {
 	untilDeathDoThemPart(element, reactive)
-
-	if (abortController) abortController.abort()
-	abortController = new AbortController()
-
-	const ref = new WeakRef(element)
-	setAttribute(element, attribute, reactive.value, abortController.signal)
-
-	reactive.addEventListener("change", () => {
-		const element = ref.deref()
-		if (element)
-			setReactiveAttribute(element, attribute, reactive, abortController)
-	}, {once: true})
-
+	const multiAbort = new MultiAbortController()
+	let old
+	reactive.subscribe(value => {
+		old = value
+		multiAbort.abort()
+		setAttribute(element, attribute, value, multiAbort.signal)
+	})
 	const special = specialAttributes[attribute]
-	if (special?.hook) {
-		special.hook(element, () => {
-			const value = special.get(element, attribute)
-			if (value != reactive.value) reactive.value = value
+	if (special?.hook && reactive.set) {
+		special.hook.call(element, () => {
+			const value = special.get.call(element, attribute)
+			if (value != old) reactive.set(value)
 		})
 	}
 }
 
-const parseArgs = (element, before, ...args) => {
+const processArgs = (element, ...args) => {
 	if (element.content) element = element.content
 	for (const arg of args) if (arg !== empty) {
+		if (arg instanceof Array) {
+			processArgs(element, ...arg)
+		} else {
 			const child = toChild(arg)
 			if (child)
-			element.insertBefore(child, before)
+				element.append(child)
 			else if (arg === undefined || arg == null)
 				console.warn(`An argument of type ${typeof arg} has been ignored`, element)
+			else if (typeof arg == "function" && arg.length == 0)
+				processArgs(element, arg())
 			else if (typeof arg == "function")
 				arg(element)
-		else if ("length" in arg)
-			parseArgs(element, before, ...arg)
 			else
 				for (const key in arg)
 					setAttribute(element, key, arg[key])
 		}
+	}
 }
 
 const node = (name, args, options) => {
@@ -174,7 +163,7 @@ 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
 }
 

state.js

@@ -5,82 +5,56 @@ const kebabToCamel = string => string.replace(/([a-z])-([a-z])/g, (_, a, b) => a
 
 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(this.changes)
+			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 {}
-
-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
+export class SimpleState extends EventTarget {
+	#synchronous
 	#queue
-	#forwardCache
-	#abortController
 	#nested = new Map()
 	#weakRef = new WeakRef(this)
+	#abortController = new AbortController
 
-	static isState(object) { return SimpleState.prototype.isPrototypeOf(object) }
-
-	constructor(target={}, options={}) {
+	constructor({synchronous, methods}={}) {
 		super()
-
-		this.#abortController = new AbortController
+		this.#synchronous = !!synchronous
 		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) {
+		if (methods ?? true) {
 			this.addEventListener("change", ({final}) => {
 				final.forEach((value, prop) => {
 					if (`${prop}Changed` in this) this[`${prop}Changed`](value)
@@ -89,77 +63,6 @@ export class State extends SimpleState {
 		}
 	}
 
-	// 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)
 
@@ -171,32 +74,127 @@ export class State extends SimpleState {
 		return () => controller.abort()
 	}
 
-	// Backwards compatibility
-	get proxy() { return this.values }
+	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 }
 }
 
-const forwardFinalizationRegistry = new FinalizationRegistry(([cache, name]) => {
-	cache.remove(name)
-})
+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
-	#fallback
+	#methods
 
-	constructor(backend, property, fallback) {
+	constructor(backend, property, methods = {}) {
 		super()
+		this.#methods = methods
 		this.#backend = backend
 		this.#property = property
-		this.#fallback = fallback
+
 		const ref = new WeakRef(this)
 		const abortController = new AbortController()
+		abortRegistry.register(this, abortController)
 		backend.addEventListener("change", event => {
 			const state = ref.deref()
 			if (state) {
-				const relevantChanges = event.changes
-					.filter(([name]) => name === property)
-					.map(([_, value]) => ["value", value])
+				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 {
@@ -205,8 +203,23 @@ export class ForwardState extends SimpleState {
 		}, {signal: abortController.signal})
 	}
 
-	get value() { return this.#backend.values[this.#property] ?? this.#fallback }
-	set value(value) { this.#backend.values[this.#property] = value }
+	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 {
@@ -273,23 +286,30 @@ const attributeObserver = new MutationObserver(mutations => {
 	}
 })
 
-export const component = (generator, name) => {
-	name = name ?? camelToKebab(generator.name)
+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 [name, value] of event.changes) {
-					const kebabName = camelToKebab(name)
+				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(this))
+			this.replaceChildren(generator.call(this, this.state))
 		}
 	}
+	if (methods) {
+		Object.defineProperties(Element.prototype, Object.getOwnPropertyDescriptors(methods))
+	}
 	customElements.define(name, Element)
 	return Element;
 }
@@ -297,14 +317,12 @@ export const component = (generator, name) => {
 class ComposedState extends SimpleState {
 	#func
 	#states
-	#options
 
 	constructor(func, options, ...states) {
-		super()
+		super(options)
 
 		this.#func = func
 		this.#states = states
-		this.#options = options
 
 		const abortController = new AbortController()
 		abortRegistry.register(this, abortController)
@@ -322,7 +340,9 @@ class ComposedState extends SimpleState {
 
 	#microtaskQueued
 	scheduleUpdate() {
-		if (this.#options.defer) {
+		if (this.synchronous) {
+			this.update()
+		} else {
 			if (!this.#microtaskQueued) {
 				queueMicrotask(() => {
 					this.#microtaskQueued = false
@@ -330,18 +350,18 @@ class ComposedState extends SimpleState {
 				})
 			}
 			this.#microtaskQueued = true
-		} else {
-			this.update()
 		}
 	}
 
 	update() {
-		this.value = this.#func(...this.#states.map(state => state.value))
-		this.dispatchEvent(new ChangeEvent([["value", this.value]]))
+		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, {defer: true}, ...states)
+export const compose = func => (...states) => new ComposedState(func, {}, ...states)
 
 const eventName = "mutation"
 
@@ -359,7 +379,6 @@ const mutationObserver = new MutationObserver(mutations => {
 
 export class DOMState extends SimpleState {
 	#target
-	#defer
 	#getValue
 	#equal
 
@@ -367,8 +386,7 @@ export class DOMState extends SimpleState {
 	#changedValue = false
 
 	constructor(target, options) {
-		super()
-		this.#defer = options.defer ?? false
+		super(options)
 		this.#target = target
 		this.#getValue = options.get ?? (target => target.value)
 		this.#equal = options.equal ?? ((a, b) => a===b)
@@ -396,7 +414,9 @@ export class DOMState extends SimpleState {
 
 		this.#old = current
 
-		if (this.#defer) {
+		if (this.synchronous) {
+			this.dispatchEvent(new ChangeEvent(["value", current]))
+		} else {
 			if (!this.#changedValue) {
 				queueMicrotask(() => {
 					this.#changedValue = false
@@ -404,10 +424,30 @@ export class DOMState extends SimpleState {
 				})
 				this.#changedValue = current
 			}
-		} else {
-			this.dispatchEvent(new ChangeEvent(["value", 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