from django.conf import settings
from django.db import models


class Conversation(models.Model):
    """Stores a user's review-agent conversation shell."""

    user = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.CASCADE,
        related_name="review_conversations",
    )
    title = models.CharField(max_length=120, blank=True)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    class Meta:
        ordering = ["-updated_at", "-id"]

    def __str__(self) -> str:
        return self.title or f"对话 {self.pk}"


class Message(models.Model):
    """Stores one user or assistant message in a conversation."""

    class Role(models.TextChoices):
        USER = "user", "用户"
        ASSISTANT = "assistant", "助手"

    conversation = models.ForeignKey(
        Conversation,
        on_delete=models.CASCADE,
        related_name="messages",
    )
    role = models.CharField(max_length=20, choices=Role.choices)
    content = models.TextField()
    created_at = models.DateTimeField(auto_now_add=True)

    class Meta:
        ordering = ["created_at", "id"]

    def __str__(self) -> str:
        return f"{self.get_role_display()} - {self.conversation_id}"