from django.conf import settings
from django.db import models
from django.utils.translation import gettext_lazy as _


class Announcement(models.Model):
    course = models.ForeignKey(
        "courses.Course",
        on_delete=models.CASCADE,
        related_name="announcements",
    )
    body = models.TextField(_("body"))
    posted_by = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name="posted_announcements",
    )
    created_at = models.DateTimeField(_("created at"), auto_now_add=True)
    updated_at = models.DateTimeField(_("updated at"), auto_now=True)

    class Meta:
        verbose_name = _("announcement")
        verbose_name_plural = _("announcements")
        ordering = ["-created_at"]
        indexes = [models.Index(fields=["course", "-created_at"])]

    def __str__(self):
        return self.body[:60]