text: # The MIT License (MIT)
  #
  # Copyright (c) 2013 Curtis Schlak
  #
  # Permission is hereby granted, free of charge, to any person obtaining a copy
  # of this software and associated documentation files (the "Software"), to deal
  # in the Software without restriction, including without limitation the rights
  # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  # copies of the Software, and to permit persons to whom the Software is
  # furnished to do so, subject to the following conditions:
  #
  # The above copyright notice and this permission notice shall be included in
  # all copies or substantial portions of the Software.
  #
  # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  # THE SOFTWARE.
  
  import inspect
  
  __all__ = ["on", "when"]
  
  
  def on(param_name):
      def f(fn):
          dispatcher = Dispatcher(param_name, fn)
          return dispatcher
  
      return f
  
  
  def when(param_type):
      def f(fn):
          frame = inspect.currentframe().f_back
          func_name = fn.func_name if "func_name" in dir(fn) else fn.__name__
          dispatcher = frame.f_locals[func_name]
          if not isinstance(dispatcher, Dispatcher):
              dispatcher = dispatcher.dispatcher
          dispatcher.add_target(param_type, fn)
  
          def ff(*args, **kw):
              return dispatcher(*args, **kw)
  
          ff.dispatcher = dispatcher
          return ff
  
      return f
  
  
  class Dispatcher(object):
      def __init__(self, param_name, fn):
          frame = inspect.currentframe().f_back.f_back
          top_level = frame.f_locals == frame.f_globals  # noqa:F841
          self.param_index = self.__argspec(fn).args.index(param_name)
          self.param_name = param_name
          self.targets = {}
  
      def __call__(self, *args, **kw):
          typ = args[self.param_index].__class__
          d = self.targets.get(typ)
          if d is not None:
              return d(*args, **kw)
          else:
              issub = issubclass
              t = self.targets
              ks = t.keys()
              ans = [t[k](*args, **kw) for k in ks if issub(typ, k)]
              if len(ans) == 1:
                  return ans.pop()
              return ans
  
      def add_target(self, typ, target):
          self.targets[typ] = target
  
      @staticmethod
      def __argspec(fn):
          # Support for Python 3 type hints requires inspect.getfullargspec
          if hasattr(inspect, "getfullargspec"):
              return inspect.getfullargspec(fn)
          else:
              return inspect.getargspec(fn)
  