import { Stream } from 'xstream';
/**
 * Delays periodic events by a given time period.
 *
 * Marble diagram:
 *
 * ```text
 * 1----2--3--4----5|
 *     delay(60)
 * ---1----2--3--4----5|
 * ```
 *
 * Example:
 *
 * ```js
 * import fromDiagram from 'xstream/extra/fromDiagram'
 * import uponStart from './uponStart'
 *
 * let is_complete = false
 * const stream = fromDiagram('1----2--3--4----5|')
 *  .compose(uponStart(() => {
 *    is_complete = true
 *  }))
 *
 * stream.addListener({
 *   next: i => console.log(i),
 *   error: err => console.error(err),
 *   complete: () => console.log('completed')
 * })
 * ```
 *
 * ```text
 * > 1  (after 60 ms)
 * > 2  (after 160 ms)
 * > 3  (after 220 ms)
 * > 4  (after 280 ms)
 * > 5  (after 380 ms)
 * > completed
 * ```
 *
 * @param {Function} op The amount of silence required in milliseconds.
 * @return {Stream}
 */
export default function uponStart<T>(op: () => void): (ins: Stream<T>) => Stream<T>;