from typing import AsyncGenerator, Optional
from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine

from src.core.config import settings

# Convert sync URL to async
db_url = settings.DATABASE_URL
if db_url.startswith("postgresql://"):
    db_url = db_url.replace("postgresql://", "postgresql+psycopg://", 1)
elif db_url.startswith("postgresql+psycopg://"):
    pass  # already correct

engine = create_async_engine(
    db_url,
    pool_pre_ping=True,
    pool_size=settings.DB_POOL_SIZE,
    max_overflow=settings.DB_MAX_OVERFLOW,
    echo=settings.DEBUG,
)

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


async def get_db() -> AsyncGenerator[AsyncSession, None]:
    """FastAPI dependency — yields an async DB session."""
    async with AsyncSessionLocal() as session:
        try:
            yield session
            await session.commit()
        except Exception:
            await session.rollback()
            raise
        finally:
            await session.close()


async def get_redis():
    """Return an async Redis client (or None if unavailable)."""
    try:
        import redis.asyncio as aioredis
        client = aioredis.from_url(settings.REDIS_URL, decode_responses=False)
        return client
    except Exception:
        return None