sketch of how to do the useful part of gulp as a module

dont-sass-me-bro.js

/**
 * This is an example of what a build script would look like
 */

var globStream = require('glob-stream').create
var globWatch = require('glob-watcher')

// I have no idea if this exists, probably not
var createSassTransform = require('sass-transform')

// these two are defined below, haven't published them yet
var st = require('spit-take')
var replacer = require('replacer')

var unsassify = st(
  replacer([/\.sass$/, '.css'], [/\/sassy\//, 'css']),
  createSassTransform
)

var globs = "./sassy/*.sass"

globStream(globs).pipe(unsassify)
globWatch(globs, unsassify.write.bind(unsassify))

replacer.js

// Might publish this if I can't find something like it.
module.exports = function replacer () {
  var replaceArgs = [].slice.call(arguments)
  return function (string) {
    replaceArgs.reduce(function (string, args) {
      return string.replace.apply(string, args)
    }, string)
  }
}

spit-take.js

var fs = require('fs')

var once = require('once')
var through = require('through2')

module.exports = function spitTake (transformPath, makeTransformStream) {
  var inProgress = {}
  return through2({objectMode: true}, transformFile)
  
  function transformFileObject (file, _, cb) {
    var self = this
    var srcPath = file.path
    var destPath = transformPath(srcPath)

    if (!inProgress[destPath]) {
      run(srcPath, destPath, makeTransformStream(), onEnd)
    } else {
      inProgress[destPath].on('end', function () {
        run(srcPath, destPath, makeTransformStream(), onEnd)
      })
    }
    
    function onEnd (err) {
      delete inProgress[destPath]
      this.push(destPath)
      cb(err)
    }
  }
}

function run (src, dest, transform, callback) {
  callback = once(callback)
  var input = fs.createReadStream(src)
  var output = fs.createWriteStream(dest)
  var transform = makeTransformStream()
  input.on('error', callback)
  output.on('error', callback)
  input.pipe(transform).pipe(output).on('end', callback.bind(null, null))
}