from django.contrib.auth import get_user_model
from django.contrib.auth.backends import ModelBackend
from django.contrib.auth.hashers import check_password

UserModel = get_user_model()

class CustomBackend(ModelBackend):
    """
    优化django原生认证，解决查询用户认证时查询无用的django内置权限（本系统有自己的权限设计）
    """

    def authenticate(self, request, username=None, password=None, **kwargs):
        try:
            if username is None:
                username = kwargs.get(UserModel.USERNAME_FIELD)
            if username is None or password is None:
                return
            user = UserModel.objects.get(username=username)
            if user.check_password(password) and self.user_can_authenticate(user):
                return user
        except UserModel.DoesNotExist:
            return None
        
    def _get_user_permissions(self, user_obj):
        return []
    
    def _get_group_permissions(self, user_obj):
        return []
    
    def _get_permissions(self, user_obj, obj, from_name):
        return set()
    
    def has_perm(self, user_obj, perm, obj=None):
        return False

    def has_module_perms(self, user_obj, app_label):
        return False