@zkochan/pnpm/lib/node_modules/most/src/source/generate.js

Fast, disk space efficient package manager

/** @license MIT License (c) copyright 2010-2014 original author or authors */
/** @author Brian Cavalier */
/** @author John Hann */

import Stream from '../Stream'
import * as base from '@most/prelude'

/**
 * Compute a stream using an *async* generator, which yields promises
 * to control event times.
 * @param f
 * @returns {Stream}
 */
export function generate (f /*, ...args */) {
  return new Stream(new GenerateSource(f, base.tail(arguments)))
}

function GenerateSource (f, args) {
  this.f = f
  this.args = args
}

GenerateSource.prototype.run = function (sink, scheduler) {
  return new Generate(this.f.apply(void 0, this.args), sink, scheduler)
}

function Generate (iterator, sink, scheduler) {
  this.iterator = iterator
  this.sink = sink
  this.scheduler = scheduler
  this.active = true

  var self = this
  function err (e) {
    self.sink.error(self.scheduler.now(), e)
  }

  Promise.resolve(this).then(next).catch(err)
}

function next (generate, x) {
  return generate.active ? handle(generate, generate.iterator.next(x)) : x
}

function handle (generate, result) {
  if (result.done) {
    return generate.sink.end(generate.scheduler.now(), result.value)
  }

  return Promise.resolve(result.value).then(function (x) {
    return emit(generate, x)
  }, function (e) {
    return error(generate, e)
  })
}

function emit (generate, x) {
  generate.sink.event(generate.scheduler.now(), x)
  return next(generate, x)
}

function error (generate, e) {
  return handle(generate, generate.iterator.throw(e))
}

Generate.prototype.dispose = function () {
  this.active = false
}