from sqlalchemy.ext.asyncio import create_async_engine, async_sessionmaker, AsyncSession
from sqlalchemy.orm import DeclarativeBase
from app.config.config import settings

# Build engine with MySQL-optimised connection pool settings
engine = create_async_engine(
    settings.database_url,
    echo=False,
    future=True,
    pool_size=settings.DB_POOL_SIZE,
    max_overflow=settings.DB_MAX_OVERFLOW,
    pool_recycle=settings.DB_POOL_RECYCLE,
    pool_pre_ping=True,         # drops and replaces stale connections automatically
)

AsyncSessionLocal = async_sessionmaker(
    bind=engine,
    class_=AsyncSession,
    expire_on_commit=False,
    autocommit=False,
    autoflush=False,
)


class Base(DeclarativeBase):
    pass


async def get_db():
    async with AsyncSessionLocal() as session:
        try:
            yield session
            await session.commit()
        except Exception:
            await session.rollback()
            raise
        finally:
            await session.close()