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fluids.ts
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fluids.ts
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/**
* MIT License
* Copyright (c) Alec Larson
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
const $get = Symbol.for('FluidValue.get')
const $observers = Symbol.for('FluidValue.observers')
export {
FluidValue,
hasFluidValue,
getFluidValue,
getFluidObservers,
callFluidObserver,
callFluidObservers,
// Mutations
setFluidGetter,
addFluidObserver,
removeFluidObserver,
}
/** Returns true if `arg` can be observed. */
const hasFluidValue = (arg: any): arg is FluidValue => Boolean(arg && arg[$get])
/**
* Get the current value.
* If `arg` is not observable, `arg` is returned.
*/
const getFluidValue: GetFluidValue = (arg: any) =>
arg && arg[$get] ? arg[$get]() : arg
/** Get the current observer set. Never mutate it directly! */
const getFluidObservers: GetFluidObservers = (target: any) =>
target[$observers] || null
/** Send an event to an observer. */
function callFluidObserver<E extends FluidEvent>(
observer: FluidObserver<E>,
event: E
): void
function callFluidObserver(observer: any, event: FluidEvent) {
if (observer.eventObserved) {
observer.eventObserved(event)
} else {
observer(event)
}
}
/** Send an event to all observers. */
function callFluidObservers<E extends FluidEvent>(
target: FluidValue<any, E>,
event: E
): void
function callFluidObservers(target: object, event: FluidEvent): void
function callFluidObservers(target: any, event: FluidEvent) {
const observers: Set<FluidObserver> = target[$observers]
if (observers) {
observers.forEach(observer => {
callFluidObserver(observer, event)
})
}
}
type GetFluidValue = {
<T, U = never>(target: T | FluidValue<U>): Exclude<T, FluidValue> | U
}
type GetFluidObservers = {
<E extends FluidEvent>(
target: FluidValue<any, E>
): ReadonlySet<FluidObserver<E>> | null
(target: object): ReadonlySet<FluidObserver> | null
}
/** An event sent to `FluidObserver` objects. */
export interface FluidEvent<T = any> {
type: string
parent: FluidValue<T>
}
/**
* Extend this class for automatic TypeScript support when passing this
* value to `fluids`-compatible libraries.
*/
abstract class FluidValue<T = any, E extends FluidEvent<T> = any> {
// @ts-expect-error (TS 4.4)
private [$get]: () => T
// @ts-expect-error (TS 4.4)
private [$observers]?: Set<FluidObserver<E>>
constructor(get?: () => T) {
if (!get && !(get = this.get)) {
throw Error('Unknown getter')
}
setFluidGetter(this, get)
}
/** Get the current value. */
protected get?(): T
/** Called after an observer is added. */
protected observerAdded?(count: number, observer: FluidObserver<E>): void
/** Called after an observer is removed. */
protected observerRemoved?(count: number, observer: FluidObserver<E>): void
}
/** An observer of `FluidValue` objects. */
export type FluidObserver<E extends FluidEvent = any> =
| { eventObserved(event: E): void }
| { (event: E): void }
/** Add the `FluidValue` type to every property. */
export type FluidProps<T> = T extends object
? { [P in keyof T]: T[P] | FluidValue<Exclude<T[P], void>> }
: unknown
/** Remove the `FluidValue` type from every property. */
export type StaticProps<T extends object> = {
[P in keyof T]: T[P] extends FluidValue<infer U> ? U : T[P]
}
/** Define the getter called by `getFluidValue`. */
const setFluidGetter = (target: object, get: () => any) =>
setHidden(target, $get, get)
/** Observe a `fluids`-compatible object. */
function addFluidObserver<T, E extends FluidEvent>(
target: FluidValue<T, E>,
observer: FluidObserver<E>
): typeof observer
function addFluidObserver<E extends FluidEvent>(
target: object,
observer: FluidObserver<E>
): typeof observer
function addFluidObserver(target: any, observer: FluidObserver) {
if (target[$get]) {
let observers: Set<FluidObserver> = target[$observers]
if (!observers) {
setHidden(target, $observers, (observers = new Set()))
}
if (!observers.has(observer)) {
observers.add(observer)
if (target.observerAdded) {
target.observerAdded(observers.size, observer)
}
}
}
return observer
}
/** Stop observing a `fluids`-compatible object. */
function removeFluidObserver<E extends FluidEvent>(
target: FluidValue<any, E>,
observer: FluidObserver<E>
): void
function removeFluidObserver<E extends FluidEvent>(
target: object,
observer: FluidObserver<E>
): void
function removeFluidObserver(target: any, observer: FluidObserver) {
const observers: Set<FluidObserver> = target[$observers]
if (observers && observers.has(observer)) {
const count = observers.size - 1
if (count) {
observers.delete(observer)
} else {
target[$observers] = null
}
if (target.observerRemoved) {
target.observerRemoved(count, observer)
}
}
}
const setHidden = (target: any, key: any, value: any) =>
Object.defineProperty(target, key, {
value,
writable: true,
configurable: true,
})