src/mdis/dispatcher.py

   1 import collections as _collections
   2 import inspect as _inspect
   3 import types as _types
   4
   5 from . import core as _core
   6
   7
   8 class DispatcherMeta(type):
   9     def __new__(metacls, name, bases, ns):
  10         hooks = {}
  11         ishook = lambda member: isinstance(member, _core.CallHook)
  12
  13         for basecls in reversed(bases):
  14             members = _inspect.getmembers(basecls, predicate=ishook)
  15             for (_, hook) in members:
  16                 hooks.update(dict.fromkeys(hook, hook))
  17
  18         conflicts = _collections.defaultdict(list)
  19         for (key, value) in tuple(ns.items()):
  20             if not ishook(value):
  21                 continue
  22             hook = value
  23             for typeid in hook:
  24                 hooks[typeid] = hook
  25                 conflicts[typeid].append(key)
  26             ns[key] = hook
  27
  28         for (typeid, keys) in conflicts.items():
  29             if len(keys) > 1:
  30                 raise ValueError(f"dispatch conflict: {keys!r}")
  31
  32         ns["__hooks__"] = _types.MappingProxyType(hooks)
  33
  34         return super().__new__(metacls, name, bases, ns)
  35
  36     def dispatch(cls, typeid=object):
  37         return cls.__hooks__.get(typeid)
  38
  39
  40 class Dispatcher(metaclass=DispatcherMeta):
  41     def __call__(self, instance):
  42         for typeid in instance.__class__.__mro__:
  43             hook = self.__class__.dispatch(typeid=typeid)
  44             if hook is not None:
  45                 break
  46         if hook is None:
  47             hook = self.__class__.dispatch()
  48         return hook(dispatcher=self, instance=instance)
  49
  50     @_core.hook(object)
  51     def dispatch_object(self, instance):
  52         raise NotImplementedError()