62 lines
1.8 KiB
TypeScript
62 lines
1.8 KiB
TypeScript
import type {PointerToPrismProvider} from './Atom'
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import Atom, {val} from './Atom'
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import type {Pointer} from './pointer'
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import {getPointerMeta} from './pointer'
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import pointer from './pointer'
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import type {$FixMe, $IntentionalAny} from './types'
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import prism from './prism/prism'
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import type {Prism} from './prism/Interface'
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/**
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* Allows creating pointer-prisms where the pointer can be switched out.
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*
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* @remarks
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* This allows reacting not just to value changes at a certain pointer, but changes
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* to the proxied pointer too.
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*/
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export default class PointerProxy<O extends {}>
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implements PointerToPrismProvider
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{
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/**
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* @internal
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*/
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readonly $$isPointerToPrismProvider = true
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private readonly _currentPointerBox: Atom<Pointer<O>>
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/**
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* Convenience pointer pointing to the root of this PointerProxy.
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*
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* @remarks
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* Allows convenient use of {@link pointerToPrism} and {@link val}.
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*/
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readonly pointer: Pointer<O>
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constructor(currentPointer: Pointer<O>) {
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this._currentPointerBox = new Atom(currentPointer)
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this.pointer = pointer({root: this as $FixMe, path: []})
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}
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/**
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* Sets the underlying pointer.
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* @param p - The pointer to be proxied.
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*/
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setPointer(p: Pointer<O>) {
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this._currentPointerBox.set(p)
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}
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/**
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* Returns a prism of the value at the provided sub-path of the proxied pointer.
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*
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* @param path - The path to create the prism at.
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*/
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pointerToPrism<P>(pointer: Pointer<P>): Prism<P> {
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const {path} = getPointerMeta(pointer)
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return prism(() => {
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const currentPointer = this._currentPointerBox.prism.getValue()
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const subPointer = path.reduce(
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(pointerSoFar, pathItem) => (pointerSoFar as $IntentionalAny)[pathItem],
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currentPointer,
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)
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return val(subPointer) as P
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})
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}
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}
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