91 lines
2.1 KiB
TypeScript
91 lines
2.1 KiB
TypeScript
import type {IDerivation} from './derivations/IDerivation'
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import prism from './derivations/prism/prism'
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import Emitter from './utils/Emitter'
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/**
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* Common interface for Box types. Boxes wrap a single value.
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*/
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export interface IBox<V> {
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/**
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* Sets the value of the Box.
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*
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* @param v - The value to update the Box with.
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*/
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set(v: V): void
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/**
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* Gets the value of the Box.
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*
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* @remarks
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* Usages of `get()` aren't tracked, they are only for retrieving the value. To track changes, you need to
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* create a derivation.
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*
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* @see derivation
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*/
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get(): V
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/**
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* Creates a derivation of the Box that you can use to track changes to it.
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*/
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derivation: IDerivation<V>
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}
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/**
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* Wraps a single value.
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*
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* @remarks
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* Derivations created with {@link Box.derivation} update based on strict equality (`===`) of the old value and the new one.
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* This also means that property-changes of objects won't be tracked, and that for objects, updates will trigger on changes of
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* reference even if the objects are structurally equal.
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*/
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export default class Box<V> implements IBox<V> {
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private _publicDerivation: IDerivation<V>
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private _emitter = new Emitter<V>()
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/**
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* @param _value - The initial value of the Box.
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*/
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constructor(
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/**
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* @internal
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*/
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protected _value: V,
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) {
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const subscribe = (listener: (val: V) => void) =>
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this._emitter.tappable.tap(listener)
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const getValue = () => this._value
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this._publicDerivation = prism(() => {
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return prism.source(subscribe, getValue)
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})
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}
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/**
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* Sets the value of the Box.
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*
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* @param v - The value to update the Box with.
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*/
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set(v: V) {
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if (v === this._value) return
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this._value = v
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this._emitter.emit(v)
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}
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/**
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* Gets the value of the Box.
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*
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* Note: usages of `get()` aren't tracked, they are only for retrieving the value. To track changes, you need to
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* create a derivation.
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*
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* @see Box.derivation
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*/
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get() {
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return this._value
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}
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/**
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* Creates a derivation of the Box that you can use to track changes to it.
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*/
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get derivation() {
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return this._publicDerivation
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}
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}
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