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const DEFAULT_CONCURRENCY = 1024
export interface Pool {  run<T>(fn: () => T): Promise<T>}
export const createPool = ({  concurrency,  interval,}: {  concurrency?: number  interval?: number} = {}): Pool => {  concurrency ||= DEFAULT_CONCURRENCY
  if (concurrency === Infinity) {    // unlimited    return {      run: async (fn) => fn(),    }  }
  const pool: Set<{}> = new Set()  const run = async <T>(    fn: () => T,    promise?: Promise<T>,    resolve?: (result: T) => void  ): Promise<T> => {    if (pool.size >= (concurrency as number)) {      promise ||= new Promise<T>((r) => (resolve = r))      setTimeout(() => run(fn, promise, resolve))      return promise    }    const marker = {}    pool.add(marker)    const result = await fn()    if (interval) {      setTimeout(() => pool.delete(marker), interval)    } else {      pool.delete(marker)    }    if (resolve) {      resolve(result)      return promise as Promise<T>    } else {      return result    }  }  return { run }}