index.js

var debug  = require('debug')('district')
var quote  = require('quotemeta')
var findup = require('findup')
var mkdirp = require('mkdirp')
var once   = require('once')
var uniq   = require('uniq')
var path   = require('path')
var fs     = require('fs')

module.exports = district

function district(namespace, linked, dirname, opts, done) {
  if (typeof opts === 'function') {
    done = opts
    opts = {}
  }

  linked  = uniq(Array.isArray(linked) ? linked : [linked])
  dirname = path.resolve(dirname)
  done    = once(done)
  opts    = opts || {}

  var prefix = opts.prefix && new RegExp('^' + quote(
    String(opts.prefix) || ''
  ) + '\\-?', 'g')

  var dup = getDuplicate(linked.map(function (d) {
    return path.basename(d)
  }))

  if (dup) {
    throw new Error('Duplicate package name: ' + dup)
  }

  findup(dirname, 'package.json', function(err, root) {
    if (err) return done(err)

    var node_modules = path.join(
      root = path.resolve(root || dirname)
    , 'node_modules', '@' + namespace)

    mkdirp(node_modules, function(err) {
      if (err) return done(err)
      doLink(node_modules)
    })
  })

  function doLink(node_modules) {
    var n = 0

    linked.forEach(function(dir) {
      var name = path.basename(dir)
      var suff = prefix ? name.replace(prefix, '') : name
      var dest = path.join(node_modules, suff)
      var rel  = path.relative(node_modules, dir)

      fs.lstat(dest, function(err, stat) {
        if (err && err.code !== 'ENOENT') return done(err)
        if (err) return link()
        if (!stat.isSymbolicLink()) return done(new Error(
            'Module "'+name+'" cannot be linked into '+node_modules
          + ': something else already exists there'
        ))

        fs.unlink(dest, link)
      })

      function link(err) {
        if (err) return done(err)
        fs.symlink(rel, dest, 'junction', bump)
      }

      function bump(err) {
        if (err) return done(err)
        debug('Linked ' + name + ' into ./' + path.relative(process.cwd(), dest))
        if (++n === linked.length) return done()
      }
    })
  }
}

function getDuplicate(arr) {
  for (var x = 0; x < arr.length; x++)
  for (var y = 0; y < arr.length; y++) {
    if (x === y) continue
    if (arr[x] === arr[y]) return arr[x]
  }

  return false
}