53 lines
1.3 KiB
TypeScript
53 lines
1.3 KiB
TypeScript
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export type FetchFunction<K, V> = (key: K) => Promise<V>;
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type ResolveReject<V> = Parameters<ConstructorParameters<typeof Promise<V>>[0]>;
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type ResolverPair<V> = {
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resolve: ResolveReject<V>[0];
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reject: ResolveReject<V>[1];
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};
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export class DebounceLoader<K, V> {
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private resolverMap = new Map<K, ResolverPair<V>>();
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private promiseMap = new Map<K, Promise<V>>();
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private resolvedPromise = Promise.resolve();
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constructor(private loadFn: FetchFunction<K, V>) {}
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public load(key: K): Promise<V> {
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const promise = this.promiseMap.get(key);
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if (typeof promise !== 'undefined') {
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return promise;
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}
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const isFirst = this.promiseMap.size === 0;
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const newPromise = new Promise<V>((resolve, reject) => {
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this.resolverMap.set(key, { resolve, reject });
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});
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this.promiseMap.set(key, newPromise);
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if (isFirst) {
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this.enqueueDebouncedLoadJob();
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}
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return newPromise;
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}
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private runDebouncedLoad(): void {
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const resolvers = [...this.resolverMap];
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this.resolverMap.clear();
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this.promiseMap.clear();
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for (const [key, { resolve, reject }] of resolvers) {
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this.loadFn(key).then(resolve, reject);
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}
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}
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private enqueueDebouncedLoadJob(): void {
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this.resolvedPromise.then(() => {
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process.nextTick(() => {
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this.runDebouncedLoad();
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});
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});
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}
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}
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