@zkochan/pnpm/lib/node_modules/most/src/combinator/transform.js

Fast, disk space efficient package manager

/** @license MIT License (c) copyright 2010-2016 original author or authors */
/** @author Brian Cavalier */
/** @author John Hann */

import Stream from '../Stream'
import Map from '../fusion/Map'
import Pipe from '../sink/Pipe'

/**
 * Transform each value in the stream by applying f to each
 * @param {function(*):*} f mapping function
 * @param {Stream} stream stream to map
 * @returns {Stream} stream containing items transformed by f
 */
export function map (f, stream) {
  return new Stream(Map.create(f, stream.source))
}

/**
* Replace each value in the stream with x
* @param {*} x
* @param {Stream} stream
* @returns {Stream} stream containing items replaced with x
*/
export function constant (x, stream) {
  return map(function () {
    return x
  }, stream)
}

/**
* Perform a side effect for each item in the stream
* @param {function(x:*):*} f side effect to execute for each item. The
*  return value will be discarded.
* @param {Stream} stream stream to tap
* @returns {Stream} new stream containing the same items as this stream
*/
export function tap (f, stream) {
  return new Stream(new Tap(f, stream.source))
}

function Tap (f, source) {
  this.source = source
  this.f = f
}

Tap.prototype.run = function (sink, scheduler) {
  return this.source.run(new TapSink(this.f, sink), scheduler)
}

function TapSink (f, sink) {
  this.sink = sink
  this.f = f
}

TapSink.prototype.end = Pipe.prototype.end
TapSink.prototype.error = Pipe.prototype.error

TapSink.prototype.event = function (t, x) {
  var f = this.f
  f(x)
  this.sink.event(t, x)
}