+ public static insertAt = (str: string, subStr: string, pos: number): string =>
+ `${str.slice(0, pos)}${subStr}${str.slice(pos)}`;
+
+ /**
+ * @param retryNumber - the number of retries that have already been attempted
+ * @returns delay in milliseconds
+ */
+ public static exponentialDelay(retryNumber = 0, maxDelayRatio = 0.2): number {
+ const delay = Math.pow(2, retryNumber) * 100;
+ const randomSum = delay * maxDelayRatio * Utils.secureRandom(); // 0-20% of the delay
+ return delay + randomSum;
+ }
+
+ public static isPromisePending(promise: Promise<unknown>): boolean {
+ return util.inspect(promise).includes('pending');
+ }
+
+ public static async promiseWithTimeout<T>(
+ promise: Promise<T>,
+ timeoutMs: number,
+ timeoutError: Error,
+ timeoutCallback: () => void = () => {
+ /* This is intentional */
+ }
+ ): Promise<T> {
+ // Create a timeout promise that rejects in timeout milliseconds
+ const timeoutPromise = new Promise<never>((_, reject) => {
+ setTimeout(() => {
+ if (Utils.isPromisePending(promise)) {
+ timeoutCallback();
+ // FIXME: The original promise shall be canceled
+ }
+ reject(timeoutError);
+ }, timeoutMs);
+ });
+
+ // Returns a race between timeout promise and the passed promise
+ return Promise.race<T>([promise, timeoutPromise]);
+ }
+
+ /**
+ * Generate a cryptographically secure random number in the [0,1[ range
+ *
+ * @returns
+ */
+ public static secureRandom(): number {
+ return crypto.randomBytes(4).readUInt32LE() / 0x100000000;
+ }
+
+ public static JSONStringifyWithMapSupport(
+ obj: Record<string, unknown> | Record<string, unknown>[] | Map<unknown, unknown>,
+ space?: number
+ ): string {
+ return JSON.stringify(
+ obj,
+ (key, value: Record<string, unknown>) => {
+ if (value instanceof Map) {
+ return {
+ dataType: 'Map',
+ value: [...value],
+ };
+ }
+ return value;
+ },
+ space
+ );
+ }
+
+ /**
+ * Convert websocket error code to human readable string message
+ *
+ * @param code - websocket error code
+ * @returns human readable string message
+ */
+ public static getWebSocketCloseEventStatusString(code: number): string {
+ if (code >= 0 && code <= 999) {
+ return '(Unused)';
+ } else if (code >= 1016) {
+ if (code <= 1999) {
+ return '(For WebSocket standard)';
+ } else if (code <= 2999) {
+ return '(For WebSocket extensions)';
+ } else if (code <= 3999) {
+ return '(For libraries and frameworks)';
+ } else if (code <= 4999) {
+ return '(For applications)';
+ }
+ }
+ if (!Utils.isUndefined(WebSocketCloseEventStatusString[code])) {
+ return WebSocketCloseEventStatusString[code] as string;
+ }
+ return '(Unknown)';
+ }
+
+ public static median(dataSet: number[]): number {
+ if (Utils.isEmptyArray(dataSet)) {
+ return 0;
+ }
+ if (Array.isArray(dataSet) === true && dataSet.length === 1) {
+ return dataSet[0];
+ }
+ const sortedDataSet = dataSet.slice().sort((a, b) => a - b);
+ return (
+ (sortedDataSet[(sortedDataSet.length - 1) >> 1] + sortedDataSet[sortedDataSet.length >> 1]) /
+ 2
+ );
+ }
+
+ // TODO: use order statistics tree https://en.wikipedia.org/wiki/Order_statistic_tree
+ public static percentile(dataSet: number[], percentile: number): number {
+ if (percentile < 0 && percentile > 100) {
+ throw new RangeError('Percentile is not between 0 and 100');
+ }
+ if (Utils.isEmptyArray(dataSet)) {
+ return 0;
+ }
+ const sortedDataSet = dataSet.slice().sort((a, b) => a - b);
+ if (percentile === 0 || sortedDataSet.length === 1) {
+ return sortedDataSet[0];
+ }
+ if (percentile === 100) {
+ return sortedDataSet[sortedDataSet.length - 1];
+ }
+ const percentileIndexBase = (percentile / 100) * (sortedDataSet.length - 1);
+ const percentileIndexInteger = Math.floor(percentileIndexBase);
+ if (!Utils.isNullOrUndefined(sortedDataSet[percentileIndexInteger + 1])) {
+ return (
+ sortedDataSet[percentileIndexInteger] +
+ (percentileIndexBase - percentileIndexInteger) *
+ (sortedDataSet[percentileIndexInteger + 1] - sortedDataSet[percentileIndexInteger])
+ );
+ }
+ return sortedDataSet[percentileIndexInteger];
+ }
+
+ public static stdDeviation(dataSet: number[]): number {
+ let totalDataSet = 0;
+ for (const data of dataSet) {
+ totalDataSet += data;
+ }
+ const dataSetMean = totalDataSet / dataSet.length;
+ let totalGeometricDeviation = 0;
+ for (const data of dataSet) {
+ const deviation = data - dataSetMean;
+ totalGeometricDeviation += deviation * deviation;
+ }
+ return Math.sqrt(totalGeometricDeviation / dataSet.length);