import platform
import time

class KeyboardHandlerError (Exception): pass

class KeyboardHandler(object):

 def __init__(self, repeat_rate=0.0, *args, **kwargs):
  self.repeat_rate = repeat_rate #How long between accepting the same keystroke?
  self._last_key = None
  self._last_keypress_time = 0
  super(KeyboardHandler, self).__init__(*args, **kwargs)
  self.active_keys = {}
  if not hasattr(self, 'replacement_mods'):
   self.replacement_mods = {}
  if not hasattr(self, 'replacement_keys'):
   self.replacement_keys = {}

 def register_key (self, key, function):
  if key in self.active_keys:
   raise KeyboardHandlerError, "Key %s is already registered to a function" % key
  if not callable(function):
   raise TypeError, "Must provide a callable to be invoked upon keypress"
  self.active_keys[key] = function

 def unregister_key (self, key, function):
  try:
   if self.active_keys[key] != function:
    raise KeyboardHandlerError, "key %s is not registered to that function" % key
  except KeyError:
   raise KeyboardHandlerError, "Key %s not currently registered"
  del(self.active_keys[key])

 def unregister_all_keys(self):
  for key in list(self.active_keys):
   self.unregister_key(key, self.active_keys[key])

 def handle_key (self, key):
  if self.repeat_rate and key == self._last_key and time.time() - self._last_keypress_time < self.repeat_rate:
   return
  try:
   function = self.active_keys[key]
  except KeyError:
   return
  self._last_key = key
  self._last_keypress_time = time.time()
  return function()

 def register_keys(self, keys):
  """Given a mapping of keystrokes to functions, registers all keystrokes"""
  for k in keys:
   self.register_key(k, keys[k])

 def unregister_keys(self, keys):
  """Given a mapping of keys to their functions, unregisters all provided keys."""
  for k in keys:
   self.unregister_key(k, keys[k])

 def standardize_key(self, key):
  """Takes a keystroke and places it in a standard case and order in a list."""
  working = key.split('+')
  working = [i.lower() for i in working]
  answer = []
  if "control" in working:
   answer.append("control")
  if "win" in working:
   answer.append("win")
  if "alt" in working:
   answer.append("alt")
  if "shift" in working:
   answer.append("shift")
  if working[-1] not in answer:
   answer.append(working[-1])
  return answer

 def standardize_keymap(self, keymap):
  """Given a keymap, returns the keymap standardized."""
  full = {}
  for i in keymap:
   answer = ""
   new = self.standardize_key(keymap[i])
   for (c, j) in enumerate(new):
    if c < len(new)-1:
     answer = "%s%s+" % (answer, j)
    else:
     answer = "%s%s" % (answer, j)
   full[i] = answer
  return full