module.exports = realpath
  realpath.realpath = realpath
  realpath.sync = realpathSync
  realpath.realpathSync = realpathSync
  realpath.monkeypatch = monkeypatch
  realpath.unmonkeypatch = unmonkeypatch
  
  var fs = require('fs')
  var origRealpath = fs.realpath
  var origRealpathSync = fs.realpathSync
  
  var version = process.version
  var ok = /^v[0-5]\./.test(version)
  var old = require('./old.js')
  
  function newError (er) {
    return er && er.syscall === 'realpath' && (
      er.code === 'ELOOP' ||
      er.code === 'ENOMEM' ||
      er.code === 'ENAMETOOLONG'
    )
  }
  
  function realpath (p, cache, cb) {
    if (ok) {
      return origRealpath(p, cache, cb)
    }
  
    if (typeof cache === 'function') {
      cb = cache
      cache = null
    }
    origRealpath(p, cache, function (er, result) {
      if (newError(er)) {
        old.realpath(p, cache, cb)
      } else {
        cb(er, result)
      }
    })
  }
  
  function realpathSync (p, cache) {
    if (ok) {
      return origRealpathSync(p, cache)
    }
  
    try {
      return origRealpathSync(p, cache)
    } catch (er) {
      if (newError(er)) {
        return old.realpathSync(p, cache)
      } else {
        throw er
      }
    }
  }
  
  function monkeypatch () {
    fs.realpath = realpath
    fs.realpathSync = realpathSync
  }
  
  function unmonkeypatch () {
    fs.realpath = origRealpath
    fs.realpathSync = origRealpathSync
  }