98 lines
2.2 KiB
TypeScript
98 lines
2.2 KiB
TypeScript
import type {$IntentionalAny} from './types'
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type PathToProp = Array<string | number>
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type PointerMeta = {
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root: {}
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path: (string | number)[]
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}
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export type UnindexableTypesForPointer =
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| number
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| string
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| boolean
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| null
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| void
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| undefined
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| Function // eslint-disable-line @typescript-eslint/ban-types
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export type UnindexablePointer = {
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[K in $IntentionalAny]: Pointer<undefined>
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}
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const pointerMetaWeakMap = new WeakMap<{}, PointerMeta>()
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export type PointerType<O> = {
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$$__pointer_type: O
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}
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export type Pointer<O> = PointerType<O> &
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(O extends UnindexableTypesForPointer
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? UnindexablePointer
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: unknown extends O
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? UnindexablePointer
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: O extends (infer T)[]
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? Pointer<T>[]
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: O extends {}
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? {[K in keyof O]-?: Pointer<O[K]>}
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: UnindexablePointer)
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const pointerMetaSymbol = Symbol('pointerMeta')
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const cachedSubPointersWeakMap = new WeakMap<
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{},
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Record<string | number, Pointer<unknown>>
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>()
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const handler = {
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get(obj: {}, prop: string | typeof pointerMetaSymbol): $IntentionalAny {
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if (prop === pointerMetaSymbol) return pointerMetaWeakMap.get(obj)!
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let subs = cachedSubPointersWeakMap.get(obj)
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if (!subs) {
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subs = {}
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cachedSubPointersWeakMap.set(obj, subs)
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}
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if (subs[prop]) return subs[prop]
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const meta = pointerMetaWeakMap.get(obj)!
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const subPointer = pointer({root: meta.root, path: [...meta.path, prop]})
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subs[prop] = subPointer
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return subPointer
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},
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}
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export const getPointerMeta = (p: Pointer<$IntentionalAny>): PointerMeta => {
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const meta: PointerMeta = p[
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pointerMetaSymbol as unknown as $IntentionalAny
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] as $IntentionalAny
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return meta
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}
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export const getPointerParts = (
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p: Pointer<$IntentionalAny>,
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): {root: {}; path: PathToProp} => {
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const {root, path} = getPointerMeta(p)
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return {root, path}
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}
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function pointer<O>({
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root,
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path,
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}: {
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root: {}
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path: Array<string | number>
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}): Pointer<O>
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function pointer(args: {root: {}; path?: Array<string | number>}) {
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const meta: PointerMeta = {
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root: args.root as $IntentionalAny,
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path: args.path ?? [],
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}
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const hiddenObj = {}
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pointerMetaWeakMap.set(hiddenObj, meta)
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return new Proxy(hiddenObj, handler) as Pointer<$IntentionalAny>
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}
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export default pointer
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