from django.db import models

from account.models import User

# 引入内置信号
from django.db.models.signals import post_save
# 引入信号接收器的装饰器
from django.dispatch import receiver


class Group(models.Model):
    # 群id
    group_id = models.AutoField(primary_key=True)
    # 群名
    group_name = models.CharField(max_length=50, blank=False)
    # 群管理员
    creator = models.ForeignKey(User, on_delete=models.CASCADE, related_name="my_groups")
    # 群成员(多对多）
    members = models.ManyToManyField(User, related_name="joined_groups")

    def to_json(self):
        return {'group_id': self.group_id, 'group_name': self.group_name}

    def get_root_folder(self):
        return self.folders.get(father_folder=None)

    def __str__(self):
        return str(self.group_id)


# 信号接收函数，每当新建Group实例的时候自动调用
@receiver(post_save, sender=Group)
def add_creator_to_group_members(sender, instance, created, **kwargs):
    if created and not instance.members.filter(username=instance.creator.username):
        instance.members.add(instance.creator)