40 lines
1.0 KiB
TypeScript
40 lines
1.0 KiB
TypeScript
export class CachePromiseFactory <A, R> {
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private readonly running = new Map<string, Promise<R>>()
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constructor (
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private readonly fn: (arg: A) => Promise<R>,
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private readonly keyBuilder: (arg: A) => string
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) {
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}
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run (arg: A) {
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return this.runWithContext(null, arg)
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}
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runWithContext (ctx: any, arg: A) {
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const key = this.keyBuilder(arg)
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if (this.running.has(key)) return this.running.get(key)
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const p = this.fn.apply(ctx || this, [ arg ])
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this.running.set(key, p)
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return p.finally(() => this.running.delete(key))
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}
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}
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export function CachePromise (options: {
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keyBuilder: (...args: any[]) => string
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}) {
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return function (_target, _key, descriptor: PropertyDescriptor) {
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const promiseCache = new CachePromiseFactory(descriptor.value, options.keyBuilder)
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descriptor.value = function () {
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if (arguments.length !== 1) throw new Error('Cache promise only support methods with 1 argument')
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return promiseCache.runWithContext(this, arguments[0])
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}
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}
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}
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