# SPDX-FileCopyrightText: Copyright (c) 2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
# SPDX-License-Identifier: Apache-2.0
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import inspect
import pydoc
from typing import Any

"""
``Registry`` and `locate` provide ways to map a string (typically found
in config files) to callable objects.
"""

__all__ = ["locate", "convert_target_to_string"]

try:
    from fvcore.common.registry import Registry  # for backward compatibility.

    __all__ += ["Registry"]
except Exception:
    pass


def convert_target_to_string(t: Any) -> str:
    """
    Inverse of ``locate()``.

    Args:
        t: any object with ``__module__`` and ``__qualname__``
    """
    if hasattr(t, "__self__") and inspect.isclass(t.__self__):
        # classmethod
        cls = t.__self__
        module = cls.__module__
        qualname = f"{cls.__name__}.{t.__name__}"
    else:
        module = t.__module__
        qualname = t.__qualname__

    # Compress the path to this object, e.g. ``module.submodule._impl.class``
    # may become ``module.submodule.class``, if the later also resolves to the same
    # object. This simplifies the string, and also is less affected by moving the
    # class implementation.
    module_parts = module.split(".")
    for k in range(1, len(module_parts)):
        prefix = ".".join(module_parts[:k])
        candidate = f"{prefix}.{qualname}"
        try:
            if locate(candidate) is t:
                return candidate
        except ImportError:
            pass
    return f"{module}.{qualname}"


_convert_target_to_string = convert_target_to_string  # for backward compatibility.


def locate(name: str) -> Any:
    """
    Locate and return an object ``x`` using an input string ``{x.__module__}.{x.__qualname__}``,
    such as "module.submodule.class_name".

    Raise Exception if it cannot be found.
    """
    obj = pydoc.locate(name)

    # Some cases (e.g. torch.optim.sgd.SGD) not handled correctly
    # by pydoc.locate. Try a private function from hydra.
    if obj is None:
        try:
            # from hydra.utils import get_method - will print many errors

            from hydra.utils import _locate
        except ImportError as e:
            raise ImportError(f"Cannot dynamically locate object {name}!") from e
        else:
            obj = _locate(name)  # it raises if fails

    return obj