from apistar import Component
from sqlalchemy.engine import Engine
from sqlalchemy.orm import Session
from sqlalchemy.orm import sessionmaker, Session, scoped_session

DBSession = scoped_session(sessionmaker())


class SQLAlchemySession(Component):
    def __init__(self, engine=None):
        if not isinstance(engine, Engine):
            raise ValueError('SQLAlchemySession must be instantiated with a sqlalchemy.engine.Engine object')
        self.engine = engine
        DBSession.configure(bind=self.engine)

    def resolve(self) -> Session:
        return DBSession()