type QueryMultipleFn = (keys: string[]) => Promise<string[]>;
type ThrottledRequest = {
key: string;
resolve: (result: string) => void;
};
class QueryBatcher {
private readonly queryMultiple: QueryMultipleFn;
private readonly throttleTime: number;
private isThrottling: boolean;
private throttledRequests: ThrottledRequest[];
constructor(queryMultiple: QueryMultipleFn, t: number) {
this.queryMultiple = queryMultiple;
this.throttleTime = t;
this.isThrottling = false;
this.throttledRequests = [];
}
async getValue(key: string): Promise<string> {
if (this.throttleTime === 0) {
const results = await this.queryMultiple([key]);
return results[0];
}
if (this.isThrottling) {
return new Promise<string>((resolve) => {
this.throttledRequests.push({ key, resolve });
});
}
this.isThrottling = true;
setTimeout(() => this.deThrottle(), this.throttleTime);
const results = await this.queryMultiple([key]);
return results[0];
}
// De-throttles and processes any pending requests.
private deThrottle(): void {
const throttledRequests = this.throttledRequests;
if (throttledRequests.length === 0) {
this.isThrottling = false;
} else {
const keys = throttledRequests.map((req) => req.key);
this.queryMultiple(keys).then((results) => {
results.forEach((result, index) => {
throttledRequests[index].resolve(result);
});
});
setTimeout(() => this.deThrottle(), this.throttleTime);
this.throttledRequests = [];
}
}
}
