import uuid
from datetime import datetime
from sqlmodel import Field, Relationship, SQLModel
from typing import TYPE_CHECKING

if TYPE_CHECKING:
    from .message import Message

class Chat(SQLModel, table=True):
    id: uuid.UUID = Field(default_factory=uuid.uuid4, primary_key=True, index=True)
    user_id: uuid.UUID = Field(index=True)
    title: str = Field(default="New Chat", max_length=100)
    created_at: datetime = Field(default_factory=datetime.utcnow, nullable=False)
    updated_at: datetime = Field(
        default_factory=datetime.utcnow, 
        nullable=False, 
        sa_column_kwargs={"onupdate": datetime.utcnow}
    )
    messages: list["Message"] = Relationship(
        back_populates="chat",
        sa_relationship_kwargs={"cascade": "all, delete-orphan"}
    )