"""Database configuration and session management."""

from collections.abc import AsyncGenerator
from typing import Annotated

from fastapi import Depends
from sqlalchemy.ext.asyncio import (
    AsyncSession,
    async_sessionmaker,
    create_async_engine,
)

from app.config import settings

# Create async engine with connection pooling
engine = create_async_engine(
    settings.DATABASE_URL,
    pool_size=settings.DB_POOL_SIZE,
    max_overflow=settings.DB_MAX_OVERFLOW,
    pool_timeout=settings.DB_POOL_TIMEOUT,
    pool_recycle=settings.DB_POOL_RECYCLE,
    echo=settings.DEBUG,
)

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


async def get_db() -> AsyncGenerator[AsyncSession, None]:
    """
    Dependency that provides an async database session.

    Yields a session and ensures proper cleanup via finally block.
    """
    async with async_session_maker() as session:
        try:
            yield session
        except Exception:
            await session.rollback()
            raise
        finally:
            await session.close()


# Type alias for dependency injection
AsyncSessionDep = Annotated[AsyncSession, Depends(get_db)]