from typing import TYPE_CHECKING

from django.contrib import admin as django_admin
from django.contrib.admin.exceptions import AlreadyRegistered  # type: ignore
from django.db import models


class tMUser(models.Model):
    username = models.CharField(max_length=30, unique=True, primary_key=True)

    if TYPE_CHECKING:
        liked = models.Manager["tMMessage"]
        sent = models.Manager["tMMessage"]
        received = models.Manager["tMMessage"]

    def __str__(self) -> str:
        return self.username

class tMMessage(models.Model):
    message_id = models.IntegerField(primary_key=True)
    content = models.CharField(max_length=10_000)
    response = models.CharField(max_length=10_000, blank=True, null=True)
    anonymous = models.BooleanField()
    likes = models.ManyToManyField(tMUser, through="tMM2MLike", related_name="liked")
    u_to = models.ForeignKey(tMUser, on_delete=models.CASCADE, related_name="received")

    if TYPE_CHECKING:
        u_from: tMUser | None
    else:
        u_from = models.ForeignKey(tMUser, on_delete=models.SET_NULL, blank=True, null=True, related_name="sent")

    def __str__(self) -> str:
        return f"({self.message_id}) {self.u_from.username if self.u_from else 'Anonymous'} messaged {self.u_to.username}"

class tMM2MLike(models.Model):
    user = models.ForeignKey(tMUser, on_delete=models.CASCADE, related_name="liked_obj")
    message = models.ForeignKey(tMMessage, on_delete=models.CASCADE, related_name="likes_obj")

    class Meta:
        unique_together = ("user", "message")

    def __str__(self) -> str:
        return f"{self.user.username} liked message {self.message.message_id}"

try:
    django_admin.site.register((tMUser, tMMessage, tMM2MLike))
except AlreadyRegistered:
    ...