import copy
import functools
import importlib.util
import os
from contextlib import contextmanager
from pathlib import Path
from types import ModuleType
from typing import Any, Callable, Generic, Optional, Sequence, TypeVar, Union
import catalogue
T = TypeVar('T')
TypeBoundT = TypeVar('TypeBoundT', bound=type)
CallableBoundT = TypeVar('CallableBoundT', bound=Callable[..., Any])

class TypedRegistry(catalogue.Registry, Generic[T]):
    """A thin wrapper around catalogue.Registry to add static typing and.

    descriptions.
    """

    def __init__(self, namespace: Sequence[str], entry_points: bool=False, description: str='') -> None:
        super().__init__(namespace, entry_points=entry_points)
        self.description = description

    def __call__(self, name: str, func: Optional[T]=None) -> Callable[[T], T]:
        return super().__call__(name, func)

    def register(self, name: str, *, func: Optional[T]=None) -> T:
        return super().register(name, func=func)

    def register_class(self, name: str, *, func: Optional[TypeBoundT]=None) -> TypeBoundT:
        return super().register(name, func=func)

    def get(self, name: str) -> T:
        return super().get(name)

    def get_all(self) -> dict[str, T]:
        return super().get_all()

    def get_entry_point(self, name: str, default: Optional[T]=None) -> T:
        return super().get_entry_point(name, default=default)

    def get_entry_points(self) -> dict[str, T]:
        return super().get_entry_points()
S = TypeVar('S')

def create_registry(*namespace: str, generic_type: type[S], entry_points: bool=False, description: str='') -> 'TypedRegistry[S]':
    """Create a new registry.

    Args:
        namespace (str): The namespace, e.g. "llmfoundry.loggers"
        generic_type (Type[S]): The type of the registry.
        entry_points (bool): Accept registered functions from entry points.
        description (str): A description of the registry.

    Returns:
        The TypedRegistry object.
    """
    if catalogue.check_exists(*namespace):
        raise catalogue.RegistryError(f'Namespace already exists: {namespace}')
    return TypedRegistry[generic_type](namespace, entry_points=entry_points, description=description)

def construct_from_registry(name: str, registry: TypedRegistry, partial_function: bool=True, pre_validation_function: Optional[Union[Callable[[Any], None], type]]=None, post_validation_function: Optional[Callable[[Any], None]]=None, kwargs: Optional[dict[str, Any]]=None) -> Any:
    """Helper function to build an item from the registry.

    Args:
        name (str): The name of the registered item
        registry (catalogue.Registry): The registry to fetch the item from
        partial_function (bool, optional): Whether to return a partial function for registered callables. Defaults to True.
        pre_validation_function (Optional[Union[Callable[[Any], None], type]], optional): An optional validation function called
            before constructing the item to return. This should throw an exception if validation fails. Defaults to None.
        post_validation_function (Optional[Callable[[Any], None]], optional): An optional validation function called after
            constructing the item to return. This should throw an exception if validation fails. Defaults to None.
        kwargs (Optional[Dict[str, Any]]): Other relevant keyword arguments.

    Raises:
        ValueError: If the validation functions failed or the registered item is invalid

    Returns:
        Any: The constructed item from the registry
    """
    if kwargs is None:
        kwargs = {}
    registered_constructor = registry.get(name)
    print('construction')
    print(registered_constructor)
    if pre_validation_function is not None:
        if isinstance(pre_validation_function, type):
            if not issubclass(registered_constructor, pre_validation_function):
                raise ValueError(f'Expected {name} to be of type {pre_validation_function}, but got {type(registered_constructor)}')
        elif isinstance(pre_validation_function, Callable):
            pre_validation_function(registered_constructor)
        else:
            raise ValueError(f'Expected pre_validation_function to be a callable or a type, but got {type(pre_validation_function)}')
    if isinstance(registered_constructor, type) or (callable(registered_constructor) and (not partial_function)):
        constructed_item = registered_constructor(**kwargs)
    elif callable(registered_constructor):
        constructed_item = functools.partial(registered_constructor, **kwargs)
    else:
        raise ValueError(f'Expected {name} to be a class or function, but got {type(registered_constructor)}')
    if post_validation_function is not None:
        post_validation_function(constructed_item)
    return constructed_item

def import_file(loc: Union[str, Path]) -> ModuleType:
    """Import module from a file.

    Used to run arbitrary python code.

    Args:
        name (str): Name of module to load.
        loc (str / Path): Path to the file.

    Returns:
        ModuleType: The module object.
    """
    if not os.path.exists(loc):
        raise FileNotFoundError(f'File {loc} does not exist.')
    spec = importlib.util.spec_from_file_location('python_code', str(loc))
    assert spec is not None
    assert spec.loader is not None
    module = importlib.util.module_from_spec(spec)
    try:
        spec.loader.exec_module(module)
    except Exception as e:
        raise RuntimeError(f'Error executing {loc}') from e
    return module

@contextmanager
def save_registry():
    """Save the registry state and restore after the context manager exits."""
    saved_registry_state = copy.deepcopy(catalogue.REGISTRY)
    yield
    catalogue.REGISTRY = saved_registry_state