from __future__ import annotations
from functools import lru_cache, singledispatch
from typing import TYPE_CHECKING, Any, Callable, Generic, Literal, TypeVar
from attrs import Factory, define
from ._compat import TypeAlias
from .fns import Predicate
if TYPE_CHECKING:
from .converters import BaseConverter
TargetType: TypeAlias = Any
UnstructuredValue: TypeAlias = Any
StructuredValue: TypeAlias = Any
StructureHook: TypeAlias = Callable[[UnstructuredValue, TargetType], StructuredValue]
UnstructureHook: TypeAlias = Callable[[StructuredValue], UnstructuredValue]
Hook = TypeVar("Hook", StructureHook, UnstructureHook)
HookFactory: TypeAlias = Callable[[TargetType], Hook]
@define
class _DispatchNotFound:
"""A dummy object to help signify a dispatch not found."""
[docs]@define
class FunctionDispatch:
"""
FunctionDispatch is similar to functools.singledispatch, but
instead dispatches based on functions that take the type of the
first argument in the method, and return True or False.
objects that help determine dispatch should be instantiated objects.
:param converter: A converter to be used for factories that require converters.
.. versionchanged:: 24.1.0
Support for factories that require converters, hence this requires a
converter when creating.
"""
_converter: BaseConverter
_handler_pairs: list[tuple[Predicate, Callable[[Any, Any], Any], bool, bool]] = (
Factory(list)
)
[docs] def register(
self,
predicate: Predicate,
func: Callable[..., Any],
is_generator=False,
takes_converter=False,
) -> None:
self._handler_pairs.insert(0, (predicate, func, is_generator, takes_converter))
[docs] def dispatch(self, typ: Any) -> Callable[..., Any] | None:
"""
Return the appropriate handler for the object passed.
"""
for can_handle, handler, is_generator, takes_converter in self._handler_pairs:
# can handle could raise an exception here
# such as issubclass being called on an instance.
# it's easier to just ignore that case.
try:
ch = can_handle(typ)
except Exception: # noqa: S112
continue
if ch:
if is_generator:
if takes_converter:
return handler(typ, self._converter)
return handler(typ)
return handler
return None
[docs] def get_num_fns(self) -> int:
return len(self._handler_pairs)
[docs] def copy_to(self, other: FunctionDispatch, skip: int = 0) -> None:
other._handler_pairs = self._handler_pairs[:-skip] + other._handler_pairs
[docs]@define(init=False)
class MultiStrategyDispatch(Generic[Hook]):
"""
MultiStrategyDispatch uses a combination of exact-match dispatch,
singledispatch, and FunctionDispatch.
:param converter: A converter to be used for factories that require converters.
:param fallback_factory: A hook factory to be called when a hook cannot be
produced.
.. versionchanged:: 23.2.0
Fallbacks are now factories.
.. versionchanged:: 24.1.0
Support for factories that require converters, hence this requires a
converter when creating.
"""
_fallback_factory: HookFactory[Hook]
_converter: BaseConverter
_direct_dispatch: dict[TargetType, Hook]
_function_dispatch: FunctionDispatch
_single_dispatch: Any
dispatch: Callable[[TargetType, BaseConverter], Hook]
def __init__(
self, fallback_factory: HookFactory[Hook], converter: BaseConverter
) -> None:
self._fallback_factory = fallback_factory
self._direct_dispatch = {}
self._function_dispatch = FunctionDispatch(converter)
self._single_dispatch = singledispatch(_DispatchNotFound)
self.dispatch = lru_cache(maxsize=None)(self.dispatch_without_caching)
[docs] def dispatch_without_caching(self, typ: TargetType) -> Hook:
"""Dispatch on the type but without caching the result."""
try:
dispatch = self._single_dispatch.dispatch(typ)
if dispatch is not _DispatchNotFound:
return dispatch
except Exception: # noqa: S110
pass
direct_dispatch = self._direct_dispatch.get(typ)
if direct_dispatch is not None:
return direct_dispatch
res = self._function_dispatch.dispatch(typ)
return res if res is not None else self._fallback_factory(typ)
[docs] def register_cls_list(self, cls_and_handler, direct: bool = False) -> None:
"""Register a class to direct or singledispatch."""
for cls, handler in cls_and_handler:
if direct:
self._direct_dispatch[cls] = handler
else:
self._single_dispatch.register(cls, handler)
self.clear_direct()
self.dispatch.cache_clear()
[docs] def register_func_list(
self,
pred_and_handler: list[
tuple[Predicate, Any]
| tuple[Predicate, Any, bool]
| tuple[Predicate, Callable[[Any, BaseConverter], Any], Literal["extended"]]
],
):
"""
Register a predicate function to determine if the handler
should be used for the type.
:param pred_and_handler: The list of predicates and their associated
handlers. If a handler is registered in `extended` mode, it's a
factory that requires a converter.
"""
for tup in pred_and_handler:
if len(tup) == 2:
func, handler = tup
self._function_dispatch.register(func, handler)
else:
func, handler, is_gen = tup
if is_gen == "extended":
self._function_dispatch.register(
func, handler, is_generator=is_gen, takes_converter=True
)
else:
self._function_dispatch.register(func, handler, is_generator=is_gen)
self.clear_direct()
self.dispatch.cache_clear()
[docs] def clear_direct(self) -> None:
"""Clear the direct dispatch."""
self._direct_dispatch.clear()
[docs] def clear_cache(self) -> None:
"""Clear all caches."""
self._direct_dispatch.clear()
self.dispatch.cache_clear()
[docs] def get_num_fns(self) -> int:
return self._function_dispatch.get_num_fns()
[docs] def copy_to(self, other: MultiStrategyDispatch, skip: int = 0) -> None:
self._function_dispatch.copy_to(other._function_dispatch, skip=skip)
for cls, fn in self._single_dispatch.registry.items():
other._single_dispatch.register(cls, fn)
other.clear_cache()