@johngw/stream/test/util.ts

Reactive programming tools using the WHATWG Streams API.

import { timeout } from '@johngw/stream-common'

export function defer<T = void>() {
  let $resolve: (value: T | PromiseLike<T>) => void
  let $reject: (reason?: unknown) => void

  return {
    promise: new Promise<T>((resolve, reject) => {
      $resolve = resolve
      $reject = reject
    }),

    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
    resolve: $resolve!,

    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
    reject: $reject!,
  }
}

export function delayedStream<T>(ms: number, items: T[]) {
  return new ReadableStream<T>({
    async pull(controller) {
      if (!items.length) return controller.close()
      await timeout(ms)
      controller.enqueue(items.shift())
    },
  })
}

export type IsString<T extends string> = T
export type IsNumber<T extends number> = T
export type IsStringOrNumber<T extends string | number> = T