73 lines
2.1 KiB
TypeScript
73 lines
2.1 KiB
TypeScript
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export default class PromiseMap<K, V extends { toString(): string }> {
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#map: Map<K, PromiseMap.Entry<V>> = new Map()
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get(key: K & { toString(): string }): null | Promise<V> {
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let initialized: PromiseMap.Entry<V>
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// if the entry doesn't exist, set it
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if (!this.#map.has(key)) {
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initialized = this.#set(key)
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} else {
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// otherwise return the entry
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// eslint-disable-next-line @typescript-eslint/no-non-null-assertion
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initialized = this.#map.get(key)!
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}
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// if the entry is a pending promise, return it
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if (initialized.status === 'pending') {
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return initialized.promise
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} else {
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// otherwise return null
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return null
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}
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}
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#set(key: K, value?: V): PromiseMap.Entry<V> {
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if (this.#map.has(key)) {
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// eslint-disable-next-line @typescript-eslint/no-non-null-assertion
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return this.#map.get(key)!
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}
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// placeholder resolver for entry
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let resolve = (item: V) => {
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void item
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}
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// promise for entry (which assigns the resolver
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const promise = new Promise<V>((resolver) => {
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resolve = resolver
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})
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// the initialized entry
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const initialized: PromiseMap.Entry<V> = {
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status: 'pending',
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resolve,
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promise,
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}
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if (null != value) {
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initialized.resolve(value)
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}
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// set the entry
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this.#map.set(key, initialized)
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return initialized
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}
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set(key: K & { toString(): string }, value: V): this {
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const initialized = this.#set(key, value)
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// if the promise is pending ...
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if (initialized.status === 'pending') {
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// ... set the entry status to resolved to free the promise
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this.#map.set(key, { status: 'resolved' })
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// ... and resolve the promise with the given value
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initialized.resolve(value)
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}
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return this
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}
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get size(): number {
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return this.#map.size
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}
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}
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// eslint-disable-next-line @typescript-eslint/no-namespace
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export namespace PromiseMap {
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export type Entry<V> =
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| { status: 'pending'; resolve: (item: V) => void; promise: Promise<V> }
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| { status: 'resolved' }
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}
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