"""
logger decorator to enable logging of infos from django's HttpRequest object.

Usage:

    Code:

    @log.logger(__name__)
    def home(request, logger=None):
        logger.info('user performed some action')

    Class based views work the same way, just decorate/modify the view's METHOD(s).

    Logging formatter configuration:

    'format': '[%(asctime)s] %(levelname)s %(message)s ' \
              '[ip: %(request.META.REMOTE_ADDR)s, ua: "%(request.META.HTTP_USER_AGENT)s"]'

Based on code from (but heavily modified/refactored):
    https://derrickpetzold.com/p/django-requst-logging-json/
    which is (c) Derrick Petzold - with a Creative Commons BY-SA license.
"""

import logging

from django.http.request import HttpRequest


def _get_attrdict(obj, basename, excluded=None):
    """
    get a dictionary of (basename-prefixed) attribute names/values,
    excluding the excluded names, internal stuff and callables.

    :param obj: the object to inspect
    :param basename: the prefix for the names in the result dictionary
    :param excluded: excluded attribute names, do not even touch [set or list]
    :return: dict names: values
    """
    if excluded is None:
        excluded = set()
    d = {}
    names = set(dir(obj)) - set(excluded)
    for name in names:
        if not name.startswith('_'):
            try:
                attr = getattr(obj, name)
                if not callable(attr):
                    d[basename + name] = attr
            except AttributeError:
                pass
    return d


def _get_elementdict(dct, basename, excluded=None):
    """
    get a dictionary of (basename-prefixed) dictionary elements,
    excluding the excluded names.

    :param dct: the dict to inspect
    :param basename: the prefix for the names in the result dictionary
    :param excluded: excluded dictionary keys [set or list]
    :return: dict names: values
    """
    if excluded is None:
        excluded = set()
    names = set(dct) - set(excluded)
    return {basename + name: dct[name] for name in names}


def _build_request_info(request):
    """
    build a dictionary with extra information extracted from request object

    :param request: django HttpRequest object
    :return: dict names: values
    """
    d = _get_elementdict(request.META, "request.META.")
    d.update(_get_attrdict(request, "request.", ['raw_post_data', ]))
    d.update(_get_attrdict(request.session, "request.session."))
    d.update(_get_attrdict(request.user, "request.user."))
    return d


def logger(name):
    """
    decorator to provide extra information from request to logging

    :param name: name of the logger
    :return: decorated function/method
    """
    def wrap(func):
        def caller(*args, **kwargs):
            request = None
            for arg in args:
                if isinstance(arg, HttpRequest):
                    request = arg
                    break
            if 'logger' not in kwargs:
                l = logging.getLogger(name)
                if request is None:
                    kwargs['logger'] = l
                else:
                    kwargs['logger'] = logging.LoggerAdapter(l, _build_request_info(request))
            return func(*args, **kwargs)
        return caller
    return wrap