src/mdis/dispatcher.py

   1 import inspect as _inspect
   2 import operator as _operator
   3
   4 from . import core as _core
   5
   6
   7 class DispatcherMeta(type):
   8     def __new__(metacls, name, bases, ns):
   9         hooks = {}
  10
  11         for (key, value) in tuple(ns.items()):
  12             if not isinstance(value, _core.CallHook):
  13                 continue
  14             hook = ns.pop(key)
  15             for typeid in hook.typeids:
  16                 if typeid in hooks:
  17                     raise ValueError(f"conflicting hook: {typeid!r}")
  18                 hooks[typeid] = hook
  19             site = hook.call.__name__
  20             ns[site] = hook
  21
  22         return super().__new__(metacls, name, bases, ns)
  23
  24     def __init__(cls, name, bases, ns):
  25         hooks = {}
  26         for hook in map(_operator.itemgetter(1), _inspect.getmembers(cls,
  27                 predicate=lambda member: isinstance(member, _core.CallHook))):
  28             for typeid in hook.typeids:
  29                 hooks[typeid] = hook
  30         cls.__hooks = hooks
  31         return super().__init__(name, bases, ns)
  32
  33     def dispatch(cls, typeid=object):
  34         return cls.__hooks.get(typeid)
  35
  36
  37 class Dispatcher(metaclass=DispatcherMeta):
  38     def __call__(self, instance):
  39         for typeid in instance.__class__.__mro__:
  40             hook = self.__class__.dispatch(typeid=typeid)
  41             if hook is not None:
  42                 break
  43         if hook is None:
  44             hook = self.__class__.dispatch()
  45         return hook(dispatcher=self, instance=instance)
  46
  47     @_core.hook(object)
  48     def dispatch_object(self, instance):
  49         raise NotImplementedError()