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type MapFn<T> = (x: T) => unknown;
type MapSchema<T> = { [K in keyof T]?: MapFn<T[K]> | MapSchema<T[K]> };
type MapReturnType<T, TMap extends MapSchema<T>> = {
  [K in keyof T]: TMap[K] extends Function
    ? ReturnType<Extract<TMap[K], MapFn<T[K]>>>
    : MapReturnType<T[K], TMap[K]>;
};

function isMapFn<T = any>(x: unknown): x is MapFn<T> {
  return typeof x === "function";

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enum QuerySelectors {
  Eq = "$eq",
  Gt = "$gt",
  Gte = "$gte",
  Lt = "$lt",
  Lte = "$lte",
  Ne = "$ne"
}

enum LogicalOperators {

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interface ReduceResult<T> {
  done: true;
  value: T;
}

export function reduceLargeArray<T, R>(
  arr: T[],
  processEachFn: (acc: R, x: T) => ReduceResult<R> | R,
  initialValue: R,
  onCompleteFn: (r: R) => void

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export function exponentialRandomBackoff(
  initialIntervalMillis: number,
  multiplier: number,
  randomizationFactor: number
) {
  checkInterval(initialIntervalMillis);
  checkMultiplier(multiplier);
  checkRandomizationFactor(randomizationFactor);
  return (attemptsMade: number) => {
    const interval = Math.round(Math.pow(multiplier, attemptsMade) * initialIntervalMillis);

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/**
 * Reimplemented python's `random.choices` function
 * https://github.com/python/cpython/blob/3.9/Lib/random.py#L473
 */
export function randomChoice<T>(population: T[], weights: number[], random: () => number): T {
  let n = population.length;
  let cum_weights = [];
  for (let i = 0; i < weights.length; i++) {
    cum_weights[i] = i === 0 ? weights[i] : weights[i] + cum_weights[i - 1];
  }

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function repeat(x: number, n: number): number[] {
  return Array(n).fill(x);
}

/**
 * Reimplemented Python's itertools.combinations_with_replacement
 * https://docs.python.org/3/library/itertools.html#itertools.combinations_with_replacement
 */
export function* combinationsWithReplacement<T>(pool: T[], r: number) {
  const n = pool.length;

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import {Multipart, MultipartFile, MultipartValue} from '@fastify/multipart';
import {FastifyRequest} from 'fastify';

function isMultipartFile(m: Multipart): m is MultipartFile {
  return !!m['toBuffer'];
}

async function getValueOrBuffer(m: Multipart): Promise<string | Buffer> {
  if (isMultipartFile(m)) {
    return m.toBuffer();