CACHE_FILE = '/tmp/rd2etrs.yaml'
coordinates = None

def etrs2rd(lam, phi):
  """ Convert etrs to rd """
  
  item['lam'] = lam
  item['phi'] = phi
  item['func'] = 'etrs2rd'
  url = 'http://vanderzwet.net/rdnap/%(func)s/%(xrd)s/%(yrd)s/0/' % item

  f = urllib.urlopen(url)
  raw = f.read()
  
  rdnap_x,rdnap_y,rdnap_h = raw.split('/')
  return (rdnap_x, rdnap_y)



def rd2etrs(xrd, yrd, hnap=0.0):
  """ 
  Convert rd to etrs 
  JavaScript Version: https://rdinfo.kadaster.nl/rd/transformator.html
  """
  # Get cache is exists
  global coordinates
  if coordinates == None:
    try: 
      coordinates = get_yaml(CACHE_FILE)
    except (IOError,AttributeError):
      coordinates = dict()
      pass

  # Check if item in cache
  xrd = float(str(xrd))
  yrd = float(str(yrd))
  if coordinates.has_key((xrd, yrd)):
    return coordinates[(xrd, yrd)]

  # Get new coordinate
  item = dict()
  item['xrd'] = xrd
  item['yrd'] = yrd
  item['hnap'] = hnap
  item['func'] = 'rd2etrs'
  url = 'http://vanderzwet.net/rdnap/%(func)s/%(xrd)s/%(yrd)s/%(hnap)s/' % item
  print "### Not in Cache, Fetching coordinate %s, %s from %s" % (xrd, yrd, url) 
  f = urllib.urlopen(url)
  raw = f.read()
  
  lam,phi,h = raw.split('/')
  coordinates[(xrd, yrd)] = (lam, phi)
  write_yaml(CACHE_FILE, coordinates)
  return (lam, phi)