var util = require('util')
var stream = require('stream')

var HEADER_SIZE = 4
var MAX_PACKET_SIZE = 0xFFFF

function ForwardWriter(target) {
  stream.Transform.call(this)
  this._target = target
}

util.inherits(ForwardWriter, stream.Transform)

ForwardWriter.prototype._transform = function(fullChunk, encoding, done) {
  var chunk = fullChunk
  var header, length

  do {
    length = Math.min(MAX_PACKET_SIZE, chunk.length)

    header = new Buffer(HEADER_SIZE)
    header.writeUInt16LE(this._target, 0)
    header.writeUInt16LE(length, 2)

    this.push(header)
    this.push(chunk.slice(0, length))

    chunk = chunk.slice(length)
  }
  while (chunk.length)

  done()
}

ForwardWriter.prototype._flush = function(done) {
  var header = new Buffer(HEADER_SIZE)
  header.writeUInt16LE(this._target, 0)
  header.writeUInt16LE(0, 2)

  this.push(header)

  done()
}

module.exports = ForwardWriter