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