from django.conf import settings
from django.contrib.auth.models import User
from django.core.exceptions import ValidationError
from django.db import models

from django.db.models import Manager

from api.models import Project
from roles.models import Role


class MemberManager(Manager):

    def can_update(self, project: int, member_id: int, new_role: str) -> bool:
        """The project needs at least 1 admin.

        Args:
            project: The project id.
            member_id: The member id.
            new_role: The new role name.

        Returns:
            Whether the mapping can be updated or not.
        """
        queryset = self.filter(
            project=project, role__name=settings.ROLE_PROJECT_ADMIN
        )
        if queryset.count() > 1:
            return True
        else:
            admin = queryset.first()
            # we can change the role except for the only admin.
            return admin.id != member_id or new_role == settings.ROLE_PROJECT_ADMIN

    def has_role(self, project_id: int, user: User, role_name: str):
        return self.filter(project=project_id, user=user, role__name=role_name).exists()


class Member(models.Model):
    user = models.ForeignKey(
        to=User,
        on_delete=models.CASCADE,
        related_name='role_mappings'
    )
    project = models.ForeignKey(
        to=Project,
        on_delete=models.CASCADE,
        related_name='role_mappings'
    )
    role = models.ForeignKey(
        to=Role,
        on_delete=models.CASCADE
    )
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)
    objects = MemberManager()

    def clean(self):
        members = self.objects.exclude(id=self.id)
        if members.filter(user=self.user, project=self.project).exists():
            message = 'This user is already assigned to a role in this project.'
            raise ValidationError(message)

    class Meta:
        unique_together = ('user', 'project')