import { Transform } from "stream";
import { performance } from "perf_hooks";
import { sleep } from "../../helpers";
import { TransformOptions } from "../baseDefinitions";
/**
 * Limits date of data transferred into stream.
 * @param targetRate Desired rate in ms
 * @param period Period to sleep for when rate is above or equal to targetRate
 */
export function rate(
    targetRate: number = 50,
    period: number = 2,
    options: TransformOptions = {
        readableObjectMode: true,
        writableObjectMode: true,
    },
) {
    const deltaMS = ((1 / targetRate) * 1000) / period; // Skip half a period
    let total = 0;
    const start = performance.now();
    return new Transform({
        async transform(data, encoding, callback) {
            const currentRate = (total / (performance.now() - start)) * 1000;
            if (targetRate && currentRate > targetRate) {
                await sleep(deltaMS);
            }
            total += 1;
            callback(undefined, data);
        },
    });
}