from django.conf import settings
from django.contrib.auth import REDIRECT_FIELD_NAME
from django.contrib.auth.views import redirect_to_login
from django.core.exceptions import ImproperlyConfigured, PermissionDenied
from django.utils import six
from django.utils.encoding import force_text


class AccessMixin(object):
    """
    Abstract CBV mixin that gives access mixins the same customizable
    functionality.
    """
    login_url = None
    permission_denied_message = ''
    raise_exception = False
    redirect_field_name = REDIRECT_FIELD_NAME

    def get_login_url(self):
        """
        Override this method to override the login_url attribute.
        """
        login_url = self.login_url or settings.LOGIN_URL
        if not login_url:
            raise ImproperlyConfigured(
                '{0} is missing the login_url attribute. Define {0}.login_url, settings.LOGIN_URL, or override '
                '{0}.get_login_url().'.format(self.__class__.__name__)
            )
        return force_text(login_url)

    def get_permission_denied_message(self):
        """
        Override this method to override the permission_denied_message attribute.
        """
        return self.permission_denied_message

    def get_redirect_field_name(self):
        """
        Override this method to override the redirect_field_name attribute.
        """
        return self.redirect_field_name

    def handle_no_permission(self):
        if self.raise_exception:
            raise PermissionDenied(self.get_permission_denied_message())
        return redirect_to_login(self.request.get_full_path(), self.get_login_url(), self.get_redirect_field_name())


class LoginRequiredMixin(AccessMixin):
    """
    CBV mixin which verifies that the current user is authenticated.
    """
    def dispatch(self, request, *args, **kwargs):
        if not request.user.is_authenticated:
            return self.handle_no_permission()
        return super(LoginRequiredMixin, self).dispatch(request, *args, **kwargs)


class PermissionRequiredMixin(AccessMixin):
    """
    CBV mixin which verifies that the current user has all specified
    permissions.
    """
    permission_required = None

    def get_permission_required(self):
        """
        Override this method to override the permission_required attribute.
        Must return an iterable.
        """
        if self.permission_required is None:
            raise ImproperlyConfigured(
                '{0} is missing the permission_required attribute. Define {0}.permission_required, or override '
                '{0}.get_permission_required().'.format(self.__class__.__name__)
            )
        if isinstance(self.permission_required, six.string_types):
            perms = (self.permission_required, )
        else:
            perms = self.permission_required
        return perms

    def has_permission(self):
        """
        Override this method to customize the way permissions are checked.
        """
        perms = self.get_permission_required()
        return self.request.user.has_perms(perms)

    def dispatch(self, request, *args, **kwargs):
        if not self.has_permission():
            return self.handle_no_permission()
        return super(PermissionRequiredMixin, self).dispatch(request, *args, **kwargs)


class UserPassesTestMixin(AccessMixin):
    """
    CBV Mixin that allows you to define a test function which must return True
    if the current user can access the view.
    """

    def test_func(self):
        raise NotImplementedError(
            '{0} is missing the implementation of the test_func() method.'.format(self.__class__.__name__)
        )

    def get_test_func(self):
        """
        Override this method to use a different test_func method.
        """
        return self.test_func

    def dispatch(self, request, *args, **kwargs):
        user_test_result = self.get_test_func()()
        if not user_test_result:
            return self.handle_no_permission()
        return super(UserPassesTestMixin, self).dispatch(request, *args, **kwargs)
