59 lines
1.7 KiB
TypeScript
59 lines
1.7 KiB
TypeScript
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import type {Prism} from './prism/Interface'
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import type {Pointer, PointerType} from './pointer'
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import {getPointerMeta} from './pointer'
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import type {$IntentionalAny} from './types'
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const identifyPrismWeakMap = new WeakMap<{}, Prism<unknown>>()
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/**
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* Interface for objects that can provide a prism at a certain path.
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*/
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export interface PointerToPrismProvider {
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/**
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* @internal
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* Future: We could consider using a `Symbol.for("dataverse/PointerToPrismProvider")` as a key here, similar to
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* how {@link Iterable} works for `of`.
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*/
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readonly $$isPointerToPrismProvider: true
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/**
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* Returns a prism of the value at the provided pointer.
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*/
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pointerToPrism<P>(pointer: Pointer<P>): Prism<P>
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}
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export function isPointerToPrismProvider(
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val: unknown,
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): val is PointerToPrismProvider {
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return (
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typeof val === 'object' &&
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val !== null &&
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(val as $IntentionalAny)['$$isPointerToPrismProvider'] === true
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)
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}
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/**
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* Returns a prism of the value at the provided pointer. Prisms are
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* cached per pointer.
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*
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* @param pointer - The pointer to return the prism at.
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*/
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export const pointerToPrism = <P extends PointerType<$IntentionalAny>>(
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pointer: P,
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): Prism<P extends PointerType<infer T> ? T : void> => {
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const meta = getPointerMeta(pointer)
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let prismInstance = identifyPrismWeakMap.get(meta)
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if (!prismInstance) {
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const root = meta.root
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if (!isPointerToPrismProvider(root)) {
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throw new Error(
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`Cannot run pointerToPrism() on a pointer whose root is not an PointerToPrismProvider`,
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)
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}
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prismInstance = root.pointerToPrism(pointer as $IntentionalAny)
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identifyPrismWeakMap.set(meta, prismInstance)
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}
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return prismInstance as $IntentionalAny
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}
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