"""数据库连接与会话管理（SQLAlchemy 2.0）。"""
from sqlalchemy import create_engine, event
from sqlalchemy.orm import DeclarativeBase, sessionmaker

from .config import get_database_url

_database_url = get_database_url()

_engine = create_engine(
    _database_url,
    pool_pre_ping=True,
    connect_args={"check_same_thread": False} if _database_url.startswith("sqlite") else {},
    echo=False,
)


@event.listens_for(_engine, "connect")
def _enable_sqlite_fk(dbapi_connection, connection_record):
    """SQLite 默认关闭外键约束，需显式开启以支持 CASCADE。"""
    if _database_url.startswith("sqlite"):
        cursor = dbapi_connection.cursor()
        cursor.execute("PRAGMA foreign_keys=ON")
        cursor.close()

SessionLocal = sessionmaker(bind=_engine, autocommit=False, autoflush=False)


class Base(DeclarativeBase):
    pass


def get_db():
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()