index.js

var pull = require('pull-core')

module.exports = pull.Source(function (onClose) {
  var buffer = [], cbs = [], waiting = [], ended

  function drain() {
    var l
    while(waiting.length && ((l = buffer.length) || ended)) {
      var data = buffer.shift()
      var cb   = cbs.shift()
      waiting.shift()(l ? null : ended, data)
      cb && cb(ended === true ? null : ended)
    }
  }

  function read (end, cb) {
    ended = ended || end
    waiting.push(cb)
    drain()
    if(ended)
      onClose && onClose(ended === true ? null : ended)
  }

  read.push = function (data, cb) {
    if(ended)
      return cb && cb(ended === true ? null : ended)
    buffer.push(data); cbs.push(cb)
    drain()
  }

  read.end = function (end, cb) {
    if('function' === typeof end)
      cb = end, end = true
    ended = ended || end || true;
    if(cb) cbs.push(cb)
    drain()
    if(ended)
      onClose && onClose(ended === true ? null : ended)
  }

  return read
})