backend/database/models.py

"""
Database models and session management.
"""
import os
from datetime import datetime
from typing import Optional, List
from sqlalchemy import create_engine, Column, String, Text, DateTime, ForeignKey
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker, relationship
from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession
from sqlalchemy.orm import sessionmaker as async_sessionmaker
import uuid


DATABASE_URL = os.getenv("DATABASE_URL", "sqlite+aiosqlite:///./algebra_chat.db")

Base = declarative_base()


class Conversation(Base):
    """Conversation/Session model."""
    __tablename__ = "conversations"
    
    id = Column(String(36), primary_key=True, default=lambda: str(uuid.uuid4()))
    title = Column(String(255), nullable=True)
    created_at = Column(DateTime, default=datetime.utcnow)
    updated_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)
    
    messages = relationship("Message", back_populates="conversation", cascade="all, delete-orphan")


class Message(Base):
    """Message model for chat history."""
    __tablename__ = "messages"
    
    id = Column(String(36), primary_key=True, default=lambda: str(uuid.uuid4()))
    conversation_id = Column(String(36), ForeignKey("conversations.id"), nullable=False)
    role = Column(String(20), nullable=False)  # 'user' or 'assistant'
    content = Column(Text, nullable=False)
    image_data = Column(Text, nullable=True)  # Base64 encoded image
    created_at = Column(DateTime, default=datetime.utcnow)
    
    conversation = relationship("Conversation", back_populates="messages")


# Async engine and session
engine = create_async_engine(DATABASE_URL, echo=False)
AsyncSessionLocal = async_sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)


async def init_db():
    """Initialize database tables."""
    # Ensure database directory exists
    if "sqlite" in DATABASE_URL:
        db_path = DATABASE_URL.replace("sqlite+aiosqlite:///", "").replace("sqlite:///", "")
        db_dir = os.path.dirname(db_path)
        if db_dir and not os.path.exists(db_dir):
            try:
                os.makedirs(db_dir, exist_ok=True)
                print(f"Created database directory: {db_dir}")
            except Exception as e:
                print(f"Error creating database directory {db_dir}: {e}")

    async with engine.begin() as conn:
        await conn.run_sync(Base.metadata.create_all)


async def get_db():
    """Get database session."""
    async with AsyncSessionLocal() as session:
        yield session