"""Utilities for marking deprecated functions."""
# Copyright 2018 Quantopian, Inc.
#
# 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 warnings
from functools import wraps


def deprecated(msg=None, stacklevel=2):
    """
    Used to mark a function as deprecated.
    Parameters
    ----------
    msg : str
        The message to display in the deprecation warning.
    stacklevel : int
        How far up the stack the warning needs to go, before
        showing the relevant calling lines.
    Usage
    -----
    @deprecated(msg='function_a is deprecated! Use function_b instead.')
    def function_a(*args, **kwargs):
    """
    def deprecated_dec(fn):
        @wraps(fn)
        def wrapper(*args, **kwargs):
            warnings.warn(
                msg or "Function %s is deprecated." % fn.__name__,
                category=DeprecationWarning,
                stacklevel=stacklevel
            )
            return fn(*args, **kwargs)
        return wrapper
    return deprecated_dec