kefir/src/two-sources/buffer-while-by.js

Reactive Programming library for JavaScript inspired by Bacon.js and RxJS with focus on high performance and low memory usage

import {createStream, createProperty} from '../patterns/two-sources'
import {NOTHING} from '../constants'

const mixin = {
  _init({flushOnEnd = true, flushOnChange = false} = {}) {
    this._buff = []
    this._flushOnEnd = flushOnEnd
    this._flushOnChange = flushOnChange
  },

  _free() {
    this._buff = null
  },

  _flush() {
    if (this._buff !== null) {
      this._emitValue(this._buff)
      this._buff = []
    }
  },

  _handlePrimaryEnd() {
    if (this._flushOnEnd) {
      this._flush()
    }
    this._emitEnd()
  },

  _handlePrimaryValue(x) {
    this._buff.push(x)
    if (this._lastSecondary !== NOTHING && !this._lastSecondary) {
      this._flush()
    }
  },

  _handleSecondaryEnd() {
    if (!this._flushOnEnd && (this._lastSecondary === NOTHING || this._lastSecondary)) {
      this._emitEnd()
    }
  },

  _handleSecondaryValue(x) {
    if (this._flushOnChange && !x) {
      this._flush()
    }

    // from default _handleSecondaryValue
    this._lastSecondary = x
  },
}

const S = createStream('bufferWhileBy', mixin)
const P = createProperty('bufferWhileBy', mixin)

export default function bufferWhileBy(primary, secondary, options /* optional */) {
  return new (primary._ofSameType(S, P))(primary, secondary, options)
}