import urlparse
try:
    from functools import wraps
except ImportError:
    from django.utils.functional import wraps  # Python 2.4 fallback.

from django.conf import settings
from django.contrib.auth import REDIRECT_FIELD_NAME
from django.utils.decorators import available_attrs


def user_passes_test(test_func, login_url=None, redirect_field_name=REDIRECT_FIELD_NAME):
    """
    Decorator for views that checks that the user passes the given test,
    redirecting to the log-in page if necessary. The test should be a callable
    that takes the user object and returns True if the user passes.
    """

    def decorator(view_func):
        @wraps(view_func, assigned=available_attrs(view_func))
        def _wrapped_view(request, *args, **kwargs):
            if test_func(request.user):
                return view_func(request, *args, **kwargs)
            path = request.build_absolute_uri()
            # If the login url is the same scheme and net location then just
            # use the path as the "next" url.
            login_scheme, login_netloc = urlparse.urlparse(login_url or
                                                        settings.LOGIN_URL)[:2]
            current_scheme, current_netloc = urlparse.urlparse(path)[:2]
            if ((not login_scheme or login_scheme == current_scheme) and
                (not login_netloc or login_netloc == current_netloc)):
                path = request.get_full_path()
            from django.contrib.auth.views import redirect_to_login
            return redirect_to_login(path, login_url, redirect_field_name)
        return _wrapped_view
    return decorator


def login_required(function=None, redirect_field_name=REDIRECT_FIELD_NAME, login_url=None):
    """
    Decorator for views that checks that the user is logged in, redirecting
    to the log-in page if necessary.
    """
    actual_decorator = user_passes_test(
        lambda u: u.is_authenticated(),
        login_url=login_url,
        redirect_field_name=redirect_field_name
    )
    if function:
        return actual_decorator(function)
    return actual_decorator


def permission_required(perm, login_url=None):
    """
    Decorator for views that checks whether a user has a particular permission
    enabled, redirecting to the log-in page if necessary.
    """
    return user_passes_test(lambda u: u.has_perm(perm), login_url=login_url)
