fs         = require 'fs'
path       = require 'path'
source     = require 'vinyl-source-stream'
buffer     = require 'vinyl-buffer'
stream     = require 'vinyl-to-stream'
watchify   = require 'watchify'
browserify = require 'browserify'


defaultOptions =
  extensions: ['.coffee']
  debug: true
  cache: {}
  packageCache: {}
  transform: ["coffeeify"]


defaults = (target, def) ->
  for own key, val of def when not (key of target)
    target[key] = val
  target


module.exports = (src, dest, getInstance = false, opts = {}) ->
  config = defaults(opts, defaultOptions)
  config.entries = [src]

  fileName = "#{path.basename(dest, '.coffee')}.js"
  log = console.log.bind(console, "watchify: #{src} -> #{dest}")
  b = watchify browserify config

  bundle = ->
    unless b
      b = watchify browserify config
      events()

    b.bundle()
      .on 'error', (err) ->
        console.error('watchify ', err.toString())
        this.emit('end')
        b = null
      .pipe source(fileName)
      .pipe buffer()
      .pipe stream()
      .pipe fs.createWriteStream(dest)

  events = ->
    b.on('update', bundle)
    b.on('log', log)
  events()

  return if getInstance then {b, bundle} else bundle