var Transform = require(‘readable-stream/transform’)

, inherits  = require('util').inherits
, xtend     = require('xtend')

function DestroyableTransform(opts) {

Transform.call(this, opts)
this._destroyed = false

}

inherits(DestroyableTransform, Transform)

DestroyableTransform.prototype.destroy = function(err) {

if (this._destroyed) return
this._destroyed = true

var self = this
process.nextTick(function() {
  if (err)
    self.emit('error', err)
  self.emit('close')
})

}

// a noop _transform function function noop (chunk, enc, callback) {

callback(null, chunk)

}

// create a new export function, used by both the main export and // the .ctor export, contains common logic for dealing with arguments function through2 (construct) {

return function (options, transform, flush) {
  if (typeof options == 'function') {
    flush     = transform
    transform = options
    options   = {}
  }

  if (typeof transform != 'function')
    transform = noop

  if (typeof flush != 'function')
    flush = null

  return construct(options, transform, flush)
}

}

// main export, just make me a transform stream! module.exports = through2(function (options, transform, flush) {

var t2 = new DestroyableTransform(options)

t2._transform = transform

if (flush)
  t2._flush = flush

return t2

})

// make me a reusable prototype that I can ‘new`, or implicitly `new` // with a constructor call module.exports.ctor = through2(function (options, transform, flush) {

function Through2 (override) {
  if (!(this instanceof Through2))
    return new Through2(override)

  this.options = xtend(options, override)

  DestroyableTransform.call(this, this.options)
}

inherits(Through2, DestroyableTransform)

Through2.prototype._transform = transform

if (flush)
  Through2.prototype._flush = flush

return Through2

})

module.exports.obj = through2(function (options, transform, flush) {

var t2 = new DestroyableTransform(xtend({ objectMode: true, highWaterMark: 16 }, options))

t2._transform = transform

if (flush)
  t2._flush = flush

return t2

})