from sqlmodel import Field, SQLModel, Relationship
from typing import Optional, List, TYPE_CHECKING
from datetime import datetime

if TYPE_CHECKING:
    from .user import User
    from .message import Message


class Conversation(SQLModel, table=True):
    """Conversation model representing a chat session between a user and the AI agent."""

    __tablename__ = "conversations"

    id: Optional[int] = Field(default=None, primary_key=True)
    user_id: int = Field(foreign_key="users.id", index=True)
    title: Optional[str] = Field(default=None, max_length=200)
    created_at: datetime = Field(default_factory=datetime.utcnow, index=True)
    updated_at: datetime = Field(default_factory=datetime.utcnow, index=True)
    deleted_at: Optional[datetime] = Field(default=None, index=True)

    # Relationships
    owner: "User" = Relationship(back_populates="conversations")
    messages: List["Message"] = Relationship(
        back_populates="conversation",
        cascade_delete=True,
        sa_relationship_kwargs={"order_by": "Message.created_at"}
    )