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import { Queue } from '../Queue'
/**
* Generic function type with configurable parameters and return type.
* @template P - Array of parameter types
* @template R - Return type
* @example
* ```typescript
* const add: Fn<[number, number], number> = (a, b) => a + b
* const log: Fn<[string], void> = (msg) => console.log(msg)
* ```
*/
export type Fn<P extends any[] = any[], R = any> = (...args: P) => R
/**
* A rune is a reactive computation function.
* Can be a computed value or an effect (side-effect function).
* Runes are the core building blocks of the reactive system.
* @template R - The type of value returned by the rune (void for effects)
* @example
* ```typescript
* const counter: Rune<number> = () => 42
* const effect: Rune<void> = () => console.log('side effect')
* ```
*/
export type Rune<R = any> = Fn<[], R>
/**
* A function that performs cleanup when called.
* Typically returned by subscription methods to allow unsubscribing.
* @example
* ```typescript
* const unsubscribe: Destructor = on(count, 'change', () => {
* console.log('changed')
* })
*
* // Later: unsubscribe()
* ```
*/
export type Destructor = Fn<[], void>
/**
* A listener function that responds to events.
* Listeners are called when specific events occur on a slot.
* @example
* ```typescript
* const listener: Listener = () => {
* console.log('Event triggered!')
* }
*
* slot.on('change', listener)
* ```
*/
export type Listener = Fn<[], void>
/**
* An action is a side-effect function that performs work.
* Actions are used in batching and context management.
* @example
* ```typescript
* const action: Action = () => {
* set(count, raw(count) + 1)
* console.log('Action performed')
* }
*
* batch(action)
* ```
*/
export type Action = Fn<[], void>
/**
* Events that can be emitted by a slot during its lifecycle.
* - `init`: Slot has been initialized
* - `update`: Slot value is being updated
* - `call`: Rune function is being called
* - `change`: Slot value has changed
* - `clear`: Slot dependencies are being cleared
* - `destroy`: Slot is being destroyed
* - `up`: Slot has gained subscribers
* - `down`: Slot has lost all subscribers
* - `get`: Fired when a rune's value is accessed
* @example
* ```typescript
* const count = () => 0
* on(count, 'change', () => console.log('Count changed!'))
* on(count, 'init', () => console.log('Count initialized'))
* ```
*/
export type Event = 'init' | 'update' | 'call' | 'change' | 'clear' | 'destroy' | 'up' | 'down' | 'get'
/**
* A Slot manages the reactive state and dependencies for a rune.
* It tracks subscribers, dependencies, and handles updates in the reactive graph.
* @template T - The type of value managed by this slot
* @example
* ```typescript
* const count = new Slot(() => 0)
*
* // Subscribe to changes
* count.on('change', () => console.log('Changed to:', count.raw))
*
* // Set new value
* count.set(5)
* ```
*/
export class Slot<T = unknown> {
/** Current value of the slot */
cur?: T
/** Previous value of the slot (before last update) */
prev?: T
/** Whether the slot has active subscribers */
up: boolean = false
/** Whether the slot has been initialized */
inited: boolean = false
/** Whether the slot is currently being prepared/initialized */
prep: boolean = false
/** The slot is a simple state */
state: boolean = false
/** Whether a set operation occurred during the current computation */
sets: boolean = false
/** Whether the slot has any subscribers */
hasSub: boolean = false
/** Queue item indicating this slot is scheduled for recomputation (needs to call force()) */
queue: QueueItem<Slot> | undefined
/** Queue item indicating this slot is scheduled for update notification (needs to call forceUpdate()) */
updateQueue: QueueItem<Slot> | undefined
/** Set of slots that depend on this slot (subscribers) */
subs: Set<Slot> = new Set<Slot>()
/** Set of slots this slot depends on (dependencies) */
deps: Set<Slot> = new Set<Slot>()
/** Event listeners registered for various slot lifecycle events */
events: Partial<Record<Event, Listener[]>> = {}
private activity = 0
private onId = {}
/**
* Creates a new Slot for managing a rune's reactive state.
* @param rune - The rune function to manage
* @param hub - The hub that owns this slot (defaults to root hub)
* @param anon - Whether this is an anonymous slot (not registered in hub)
* @example
* ```typescript
* const count = () => 0
* const slot = new Slot(count, Hub.root, false)
* ```
*/
constructor (
readonly rune: Rune<T>,
readonly hub: Hub = Hub.root,
readonly anon: boolean = hub === Hub.root,
) {
if (!anon) {
hub.slots.set(rune, this)
}
}
/**
* Destroys the slot, cleaning up all subscriptions and removing it from the hub.
* Emits 'clear' and 'destroy' events before cleanup.
* @example
* ```typescript
* const slot = new Slot(() => 0)
*
* slot.on('change', () => console.log('changed'))
* slot.destroy() // Cleans up all subscriptions and remove from hub
* ```
*/
destroy (): void {
this.event(this.events.destroy)
this.off()
this.up = false
this.prep = false
this.inited = false
this.clearQueue()
if (!this.anon) {
this.hub.slots.delete(this.rune)
}
}
/**
* Clears any pending recomputation from the queue.
* @internal
*/
private clearQueue () {
if (this.queue) {
this.queue.abort()
this.queue = undefined
}
}
/**
* Initializes the slot by computing its initial value.
* Runs the rune function and tracks dependencies.
* Emits 'init' event when complete.
* @example
* ```typescript
* const slot = new Slot(() => 42)
*
* console.log(slot.cur) // undefined
* slot.init() // Computes initial value and emits 'init'
* console.log(slot.cur) // 42
* ```
*/
init (): void {
if (this.prep) return
this.prep = true
this.call()
this.inited = true
this.event(this.events.init)
}
/**
* Executes an action within this slot's context.
* Sets this slot as the current context for dependency tracking.
* @template A - The action function type
* @param action - The action to execute
* @returns The result of the action
*/
use <A extends Fn<[]>> (action: A): ReturnType<A> {
const hub = this.hub
const prevSlot = hub.ctx
if (prevSlot === this) {
return hub.use(action)
}
hub.ctx = this
const result = hub.use(action)
hub.ctx = prevSlot
return result
}
clear () {
if (!this.inited) return
this.event(this.events.clear)
}
rawCall (): void {
this.sets = false
this.use(() => {
if (!this.updateQueue) {
this.prev = this.cur
}
this.cur = this.rune()
this.event(this.events.call)
})
}
/**
* Calls the rune function to compute a new value.
* Tracks dependencies and emits 'clear' and 'call' events.
* @internal
*/
call () {
do {
this.clear()
this.clearQueue()
this.rawCall()
} while (this.queue)
}
/**
* Gets the current value without tracking dependencies.
* Initializes the slot if needed and forces any pending updates.
* @returns The current value
* @example
* ```typescript
* const slot = new Slot(() => 42)
*
* console.log(slot.raw) // 42, no dependency tracking
* ```
*/
get raw (): T {
this.event(this.events.get)
this.init()
if (this.queue) {
this.force()
}
return this.cur!
}
/**
* Gets the current value with dependency tracking.
* Alias for the get() method.
* @example
* ```typescript
* const slot = new Slot(() => 0)
*
* on(() => {
* console.log(slot.value) // Tracks dependency
* })
* ```
*/
get value (): T {
return this.get()
}
/**
* Sets a new value for the slot.
* Alias for the set() method.
* @example
* ```typescript
* const slot = new Slot(() => 0)
*
* slot.value = 42 // Sets new value
* console.log(slot.value) // 42
* ```
*/
set value (value: T) {
this.set(value)
}
/**
* Gets the current value and tracks this slot as a dependency.
* If called within another slot's context, creates a dependency relationship.
* @returns The current value
* @example
* ```typescript
* const count = new Slot(() => 0)
*
* on(() => {
* console.log(count.get())
* })
* ```
*/
get (): T {
const result = this.raw
if (this.hub.ctx && !this.hub.unwatching) {
this.hub.ctx.bind(this)
}
return result
}
/**
* Sets a new value for the slot.
* If the value differs from the current value, schedules an update.
* @param value - The new value to set
* @example
* ```typescript
* const count = new Slot(() => 0)
* count.on('change', () => console.log('Changed to:', count.raw))
*
* slot.set(42) // Logs: Changed to: 42
* slot.set(42) // No change, no log
* ```
*/
set (value: T): void {
if (this.hub.ctx) {
this.hub.ctx.sets = true
}
if (this.raw !== value) {
if (!this.updateQueue) {
this.prev = this.cur
}
this.cur = value
this.update()
}
}
/**
* Creates a dependency relationship with another slot.
* This slot will be notified when the other slot updates.
* @param slot - The slot to depend on
* @internal
*/
bind (slot: Slot): void {
this.deps.add(slot)
slot.subs.add(this)
slot.hasSub = true
if (!slot.up) {
slot.up = true
slot.event(slot.events.up)
}
}
/**
* Activates the slot and keeps it active.
* @returns A destructor function to deactivate
* @example
* ```typescript
* const count = new Slot(() => 0)
*
* const log = new Slot(() => {
* console.log(count.value)
* })
*
* log.on()
* count.set(1) // logs: 1
* ```
*/
on (): Destructor
/**
* Subscribes to a specific slot event.
* @param event - The event to listen for
* @param listener - The listener function to call
* @returns A destructor function to unsubscribe
* @example
* ```typescript
* const count = new Slot(() => 0)
*
* const unsubscribe = count.on('change', () => {
* console.log('Value changed to:', count.raw)
* })
*
* slot.set(42) // Logs: Value changed to: 42
* unsubscribe() // Stop listening
* ```
*/
on (event: Event, listener: Listener): Destructor
on (event?: Event, listener?: Listener) {
if (!event) {
if (!this.up) {
this.up = true
if (!this.inited) {
this.init()
} else if (!this.state) {
this.call()
}
if (!this.deps.size) {
this.state = true
}
this.event(this.events.up)
}
if (this.hub.ctx && !this.hub.unwatching) {
this.hub.ctx.bind(this)
}
let onId: object = this.onId
this.activity++
return () => {
if (this.onId !== onId) return
if (this.activity === 1) return this.off()
this.activity--
onId = {}
}
}
const events = this.events[event]
if (!events) {
this.events[event] = [listener!]
} else {
events.push(listener!)
}
return this.off.bind(this, event, listener!)
}
/**
* Deactivates the slot and removes all its dependencies.
*/
off (): void
/**
* Unsubscribes a specific listener from an event.
* @param event - The event to unsubscribe from
* @param listener - The listener to remove
*/
off (event: Event, listener: Listener): void
off (event?: Event, listener?: Listener) {
if (!event) {
this.clear()
this.activity = 0
this.onId = {}
this.deps.forEach((source) => {
const sourceListeners = source.subs
if (sourceListeners.size === 1) {
source.off()
} else {
sourceListeners.delete(this)
}
})
this.deps.clear()
this.subs.forEach(sub => sub.deps.delete(this))
this.subs.clear()
this.hasSub = false
this.up = false
this.event(this.events.down)
return
}
const events = this.events[event]
if (!events) return
this.events[event] = events.filter((l) => l !== listener)
}
/**
* Triggers a list of event listeners.
* Executes listeners in a batched, unwatched context.
* @param events - Array of listener functions to call
* @internal
*/
event (events?: Listener[]): void {
if (!events || !events.length) return
const hub = this.hub
this.use(() => {
hub.unwatch(() => {
hub.batch(() => {
for (let i = 0; i < events.length; i++) {
events[i]()
}
})
})
})
}
/**
* Schedules an update notification for this slot.
* Queues the slot for update processing in the next batch.
*/
update (): void {
if (this.updateQueue) return
this.hub.batch(() => {
this.updateQueue = this.hub.queue.force(this)
})
}
/**
* Forces recomputation of the slot's value.
* Recomputes dependencies and schedules updates.
* @internal
*/
force () {
if (!this.deps.size) {
this.clearQueue()
this.update()
return
}
do {
this.clear()
this.clearQueue()
const deps = this.deps
const newDeps = new Set<Slot>()
this.deps = newDeps
this.rawCall()
for (const dep of deps) {
if (!newDeps.has(dep)) {
dep.off()
}
}
if (this.inited) {
this.update()
}
} while (this.queue)
}
/**
* Forces immediate update notification to subscribers.
* Emits 'update' and 'change' events and propagates to subscribers.
* @internal
*/
forceUpdate () {
const updateQueue = this.updateQueue
if (updateQueue) {
updateQueue.abort()
this.updateQueue = undefined
}
this.event(this.events.update)
if (this.prev !== this.cur) {
this.event(this.events.change)
if (this.hasSub) {
for (const sub of this.subs) {
if (sub.queue) continue
if (sub.hasSub || sub.sets) {
sub.force()
} else {
sub.queue = this.hub.queue.push(sub)
}
}
}
}
}
}
/**
* Hub manages the reactive system's execution context and slot lifecycle.
* It handles batching updates, tracking dependencies, and managing slot instances.
*/
export class Hub {
/** The root hub instance used as the default hub */
static root = new Hub()
/** The currently active hub during execution */
static cur: Hub | undefined
/** The currently executing slot (for dependency tracking) */
ctx: Slot | undefined
/** Map of runes to their corresponding slots */
readonly slots: Map<Rune, Slot> = new Map()
/** Whether dependency tracking is currently disabled */
unwatching: boolean = false
/** Whether updates are currently being batched */
batching = false
/** Queue for managing slot updates */
readonly queue: Queue<Slot> = new Queue()
/**
* Executes an action within this hub's context.
* Sets this hub as the current hub during execution.
* @template A - The action function type
* @param action - The action to execute
* @returns The result of the action
*/
use <A extends Fn<[]>> (action: A): ReturnType<A> {
const prevHub = Hub.cur
Hub.cur = this
const result = action()
Hub.cur = prevHub
return result
}
/**
* Executes an action without tracking dependencies.
* Temporarily disables dependency tracking during execution.
* @template A - The action function type
* @param action - The action to execute
* @returns The result of the action
*/
unwatch <A extends Fn<[]>> (action: A): ReturnType<A> {
const prevUnwatch = this.unwatching
this.unwatching = true
const result = action()
this.unwatching = prevUnwatch
return result
}
/**
* Batches multiple updates together for efficient processing.
* Updates are queued and processed together after the action completes.
* @param action - The action to execute in batch mode
*/
batch (action: Action): void {
if (this.batching) {
action()
return
}
this.batching = true
action()
this.endBatching()
}
/**
* Processes all queued updates and ends batch mode.
* Flushes the update queue and notifies all affected slots.
* @internal
*/
endBatching (): void {
if (!this.batching) return
if (!this.queue.size) {
this.batching = false
return
}
const queue = this.queue
let item: QueueItem<Slot> | undefined
while ((item = queue.start)) {
if (item.forced) {
item.value.forceUpdate()
} else {
item.value.force()
}
}
this.batching = false
}
/**
* Destroys the hub and all its slots.
* Cleans up all resources and resets the hub state.
*/
destroy () {
this.slots.forEach((slot) => {
slot.destroy()
})
this.slots.clear()
this.queue.clear()
this.batching = false
this.unwatching = false
this.ctx = undefined
}
}
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