from sqlmodel import Field, SQLModel, Relationship, Column, JSON
from typing import Optional, Dict, Any, TYPE_CHECKING
from datetime import datetime
from enum import Enum

if TYPE_CHECKING:
    from .conversation import Conversation


class MessageRole(str, Enum):
    """Enum representing the role of a message sender."""
    USER = "user"
    ASSISTANT = "assistant"


class Message(SQLModel, table=True):
    """Message model representing a single exchange in a conversation."""

    __tablename__ = "messages"
    __table_args__ = (
        {"sqlite_autoincrement": True},
    )

    id: Optional[int] = Field(default=None, primary_key=True)
    conversation_id: int = Field(foreign_key="conversations.id", index=True)
    role: MessageRole = Field(sa_column_kwargs={"nullable": False})
    content: str = Field(sa_column_kwargs={"nullable": False})
    tool_calls: Optional[Dict[str, Any]] = Field(
        default=None,
        sa_column=Column(JSON)
    )
    sequence_number: int = Field(index=True)
    created_at: datetime = Field(default_factory=datetime.utcnow, index=True)
    deleted_at: Optional[datetime] = Field(default=None, index=True)

    # Relationships
    conversation: "Conversation" = Relationship(back_populates="messages")