from collections.abc import Generator
from contextlib import contextmanager
from sqlalchemy.orm.session import Session
from sqlalchemy import create_engine, event, Engine
from sqlalchemy.orm import scoped_session, sessionmaker
from backend.core.config import get_app_settings

settings = get_app_settings()

def sql_global_init(db_url: str):
  connect_args = {"check_same_thread": False}

  engine = create_engine(db_url, echo=False, connect_args=connect_args, pool_pre_ping=True, future=True)

  SessionLocal = scoped_session(sessionmaker(autocommit=False, autoflush=False, bind=engine, future=True))

  return SessionLocal, engine

SessionLocal, engine = sql_global_init(settings.DB_URL)

@event.listens_for(Engine, "connect")
def set_sqlite_pragma(dbapi_connection, connection_record):
  cursor = dbapi_connection.cursor()
  cursor.execute("PRAGMA foreign_keys=ON")
  cursor.close()

@contextmanager
def session_context() -> Session: # type: ignore
    """
    session_context() provides a managed session to the database that is automatically
    closed when the context is exited. This is the preferred method of accessing the
    database.

    Note: use `generate_session` when using the `Depends` function from FastAPI
    """
    global SessionLocal
    sess = SessionLocal()
    try:
        yield sess
    finally:
        sess.close()

def generate_session() -> Generator[Session, None, None]:
  db = SessionLocal()
  try:
      yield db
  finally:
      db.close()