import uuid

from django.db import models
from django.urls import reverse
from django.utils import timezone


class Post(models.Model):
    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
    owner = models.ForeignKey(
        "lyric.User",
        related_name="posts",
        blank=True,
        null=True,
        on_delete=models.CASCADE,
    )

    shared_with = models.ManyToManyField(
        "lyric.User",
        related_name="shared_posts",
        blank=True,
    )

    @property
    def name(self):
        return self.lines.first().text

    def get_absolute_url(self):
        return reverse("billboard:view_post", args=[self.id])


class Line(models.Model):
    text = models.TextField(default="")
    post = models.ForeignKey(Post, default=None, on_delete=models.CASCADE, related_name="lines")

    class Meta:
        ordering = ("id",)
        unique_together = ("post", "text")

    def __str__(self):
        return self.text


class Brief(models.Model):
    """A slide-down notification record. Owner = whose attention; post = where
    FYI navigates (and where mark-read happens on GET); line = the specific
    appended Line that triggered it (so the banner can surface its text).

    `kind` discriminates the affordances the banner renders. NOTE_UNLOCK
    Briefs get a clickable square that jumps direct to my_notes.html;
    SHARE_INVITE Briefs render the invitation copy; USER_POST is the legacy
    user-authored compose flow.

    Magic-link confirmation + invalid-link banners use the same Gaussian-glass
    visual styling but ride no Brief row (transient one-shot).
    """
    KIND_NOTE_UNLOCK   = "note_unlock"
    KIND_USER_POST     = "user_post"
    KIND_SHARE_INVITE  = "share_invite"
    KIND_CHOICES = [
        (KIND_NOTE_UNLOCK,  "Note unlock"),
        (KIND_USER_POST,    "User post"),
        (KIND_SHARE_INVITE, "Share invite"),
    ]

    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
    owner = models.ForeignKey(
        "lyric.User",
        related_name="briefs",
        on_delete=models.CASCADE,
    )
    post = models.ForeignKey(
        Post,
        related_name="briefs",
        on_delete=models.CASCADE,
    )
    # Line is nullable because a share_invite-style Brief can race ahead of its
    # async-appended Line write; the post FK alone is enough to navigate.
    line = models.ForeignKey(
        Line,
        related_name="briefs",
        on_delete=models.CASCADE,
        null=True,
        blank=True,
    )
    is_unread = models.BooleanField(default=True)
    kind = models.CharField(
        max_length=32,
        choices=KIND_CHOICES,
        default=KIND_USER_POST,
    )
    title = models.CharField(max_length=255, blank=True)
    created_at = models.DateTimeField(default=timezone.now)

    class Meta:
        ordering = ["-created_at"]

    def __str__(self):
        return (
            f"Brief({self.kind}, {self.owner.email}, "
            f"unread={self.is_unread})"
        )