from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession, async_sessionmaker
from sqlalchemy.orm import declarative_base
from ..core.config import settings
import contextlib

# Create async engine for FastAPI
async_engine = create_async_engine(
    settings.DATABASE_URL,
    echo=True,
    future=True,
    pool_pre_ping=True
)

# Create async session factory
AsyncSessionLocal = async_sessionmaker(
    bind=async_engine,
    class_=AsyncSession,
    expire_on_commit=False
)

# Create declarative base for models
Base = declarative_base()

# Database dependency for FastAPI routes
async def get_db():
    async with AsyncSessionLocal() as session:
        try:
            yield session
        finally:
            await session.close()

# Database access for background tasks and services
class Database:
    def __init__(self):
        self._session_factory = AsyncSessionLocal

    @contextlib.asynccontextmanager
    async def session(self):
        """Get a database session with automatic commit/rollback"""
        session = self._session_factory()
        try:
            yield session
            await session.commit()
        except:
            await session.rollback()
            raise
        finally:
            await session.close()

    async def get_session(self):
        """Get a session for manual management"""
        return self._session_factory()

# Create singleton instance for database access
db = Database()