# Copyright (C) 2013 eNovance SAS <licensing@enovance.com>
#
# 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.

"""Log helper functions."""

import functools
import inspect
import logging


def _get_full_class_name(cls):
    return '{}.{}'.format(cls.__module__,
                          getattr(cls, '__qualname__', cls.__name__))


def _is_method(obj, method):
    """Returns True if a given method is obj's method.

    You can not simply test a given method like:

    return inspect.ismethod(method)

    This is because functools.wraps converts the method to a function
    in log_method_call function.
    """
    return inspect.ismethod(getattr(obj, method.__name__, None))


def log_method_call(method):
    """Decorator helping to log method calls.

    :param method: Method to decorate to be logged.
    :type method: method definition
    """
    log = logging.getLogger(method.__module__)

    @functools.wraps(method)
    def wrapper(*args, **kwargs):
        args_start_pos = 0
        if args:
            first_arg = args[0]
            if _is_method(first_arg, method):
                cls = (first_arg if isinstance(first_arg, type)
                       else first_arg.__class__)
                caller = _get_full_class_name(cls)
                args_start_pos = 1
            else:
                caller = 'static'
        else:
            caller = 'static'
        data = {'caller': caller,
                'method_name': method.__name__,
                'args': args[args_start_pos:], 'kwargs': kwargs}
        log.debug('%(caller)s method %(method_name)s '
                  'called with arguments %(args)s %(kwargs)s', data)
        return method(*args, **kwargs)
    return wrapper
