"""
ChatSession and ChatMessage models.

Maps to AGENT.md DBML: `chat_sessions` (Lines 526-534) and `chat_messages` (Lines 536-543).
"""
from django.conf import settings
from django.db import models

from core.models import BaseModel


class ChatSession(BaseModel):
    """A conversation session between a user and an AI model."""

    user = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.CASCADE,
        related_name="chat_sessions",
    )
    org = models.ForeignKey(
        "organizations.Organization",
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name="chat_sessions",
    )
    title = models.CharField(max_length=255, blank=True, default="")
    model = models.ForeignKey(
        "intelligence.AIModel",
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name="sessions",
    )
    system_prompt_snapshot = models.TextField(blank=True, default="")

    class Meta:
        db_table = "chat_sessions"
        ordering = ["-created_at"]

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


class ChatMessage(BaseModel):
    """A single message in a chat session."""

    class Role(models.TextChoices):
        USER = "user", "User"
        ASSISTANT = "assistant", "Assistant"
        SYSTEM = "system", "System"

    session = models.ForeignKey(
        ChatSession,
        on_delete=models.CASCADE,
        related_name="messages",
    )
    role = models.CharField(max_length=20, choices=Role.choices)
    content = models.TextField()
    tokens_used = models.PositiveIntegerField(default=0)

    class Meta:
        db_table = "chat_messages"
        ordering = ["created_at"]

    def __str__(self) -> str:
        return f"{self.get_role_display()}: {self.content[:50]}"