#############################################################################
# from http://djangosnippets.org/snippets/243/

from functools import wraps
import base64

from django.http import HttpResponse
from django.contrib.auth import authenticate, login


def view_or_basicauth(view, request, test_func, realm="", *args, **kwargs):
    """
    This is a helper function used by 'logged_in_or_basicauth' and
    'has_perm_or_basicauth' (deleted) that does the nitty of determining if they
    are already logged in or if they have provided proper http-authorization
    and returning the view if all goes well, otherwise responding with a 401.
    """
    if test_func(request.user):
        # Already logged in, just return the view.
        #
        return view(request, *args, **kwargs)

    # They are not logged in. See if they provided login credentials
    #
    if 'HTTP_AUTHORIZATION' in request.META:
        auth = request.META['HTTP_AUTHORIZATION'].split()
        if len(auth) == 2:
            # NOTE: We are only support basic authentication for now.
            #
            if auth[0].lower() == "basic":
                uname, passwd = base64.b64decode(auth[1].encode('utf-8')).decode('utf-8').split(':')
                user = authenticate(username=uname, password=passwd)
                if user is not None:
                    if user.is_active:
                        login(request, user)
                        request.user = user
                        return view(request, *args, **kwargs)

    # Either they did not provide an authorization header or
    # something in the authorization attempt failed. Send a 401
    # back to them to ask them to authenticate.
    #
    response = HttpResponse()
    response.status_code = 401
    response['WWW-Authenticate'] = 'Basic realm="%s"' % realm
    return response


#
def logged_in_or_basicauth(realm=""):
    """
    A simple decorator that requires a user to be logged in. If they are not
    logged in the request is examined for a 'authorization' header.

    If the header is present it is tested for basic authentication and
    the user is logged in with the provided credentials.

    If the header is not present a http 401 is sent back to the
    requestor to provide credentials.

    The purpose of this is that in several django projects I have needed
    several specific views that need to support basic authentication, yet the
    web site as a whole used django's provided authentication.

    The uses for this are for urls that are access programmatically such as
    by rss feed readers, yet the view requires a user to be logged in. Many rss
    readers support supplying the authentication credentials via http basic
    auth (and they do NOT support a redirect to a form where they post a
    username/password.)

    Use is simple:

    @logged_in_or_basicauth
    def your_view:
        ...

    You can provide the name of the realm to ask for authentication within.
    """
    def view_decorator(func):
        def wrapper(request, *args, **kwargs):
            return view_or_basicauth(func, request,
                                     lambda u: u.is_authenticated,
                                     realm, *args, **kwargs)
        return wrapper
    return view_decorator


#############################################################################


def factory_decorator(decorator):
    """ generates a decorator for a function factory class
    if A(*) == f, factory_decorator(D)(A)(*) == D(f)
    """
    def fac_dec(func):
        @wraps(func)
        def wrapper(*args, **kwargs):
            return decorator(func(*args, **kwargs))
        return wrapper
    return fac_dec
