pull-stream/throughs/take.js

'use strict'

//read a number of items and then stop.
module.exports = function take (test, opts) {
  opts = opts || {}
  var last = opts.last || false // whether the first item for which !test(item) should still pass
  var ended = false
  if('number' === typeof test) {
    last = true
    var n = test; test = function () {
      return --n
    }
  }

  return function (read) {

    function terminate (cb) {
      read(true, function (err) {
        last = false; cb(err || true)
      })
    }

    return function (end, cb) {
      if(ended && !end) last ? terminate(cb) : cb(ended)
      else if(ended = end) read(ended, cb)
      else
        read(null, function (end, data) {
          if(ended = ended || end) {
            //last ? terminate(cb) :
            cb(ended)
          }
          else if(!test(data)) {
            ended = true
            last ? cb(null, data) : terminate(cb)
          }
          else
            cb(null, data)
        })
    }
  }
}