"""Database engine and session; pool_recycle=180, pool_pre_ping=True for TiDB."""
from collections.abc import Generator
from sqlalchemy import create_engine
from sqlmodel import Session, Session as SessionType
import redis as redis_lib

from app.core.config import get_settings

_engine = None
_redis_client = None


def get_redis() -> redis_lib.Redis:
    global _redis_client
    if _redis_client is None:
        _redis_client = redis_lib.from_url(get_settings().REDIS_URL, decode_responses=True)
    return _redis_client


def get_engine():
    global _engine
    if _engine is None:
        s = get_settings()
        _engine = create_engine(
            s.sqlalchemy_database_uri,
            pool_recycle=180,
            pool_pre_ping=True,
            echo=False,
        )
    return _engine


def get_session() -> Generator[SessionType, None, None]:
    engine = get_engine()
    with Session(engine) as session:
        try:
            yield session
        except Exception:
            session.rollback()
            raise
        finally:
            session.close()