"""Database configuration and session management."""
from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine, async_sessionmaker
from sqlalchemy.orm import DeclarativeBase

from app.config import get_settings

settings = get_settings()

# Create async engine
engine_kwargs = {
    "echo": settings.debug,
    "future": True,
}
# Production hardening: enable connection pooling for Postgres
if settings.database_url.startswith("postgresql"):
    engine_kwargs.update(
        {
            "pool_size": settings.db_pool_size,
            "max_overflow": settings.db_max_overflow,
            "pool_timeout": settings.db_pool_timeout,
            "pool_pre_ping": True,
        }
    )

engine = create_async_engine(settings.database_url, **engine_kwargs)

# Create async session factory
AsyncSessionLocal = async_sessionmaker(
    engine,
    class_=AsyncSession,
    expire_on_commit=False,
    autocommit=False,
    autoflush=False,
)


class Base(DeclarativeBase):
    """Base class for all database models."""
    pass


async def get_db() -> AsyncSession:
    """Dependency to get database session."""
    async with AsyncSessionLocal() as session:
        try:
            yield session
            await session.commit()
        except Exception:
            await session.rollback()
            raise
        finally:
            await session.close()


async def init_db():
    """Initialize database tables."""
    async with engine.begin() as conn:
        await conn.run_sync(Base.metadata.create_all)
        # Apply additive migrations (indexes / optional columns) for existing DBs
        from app.db_migrations import apply_migrations
        await apply_migrations(conn)