from collections.abc import Iterator

from sqlalchemy import create_engine, event
from sqlalchemy.orm import Session, sessionmaker

from app.core.config import settings

_is_sqlite = settings.database_url.startswith("sqlite")
_connect_args = {"check_same_thread": False, "timeout": 30} if _is_sqlite else {}

engine = create_engine(
    settings.database_url,
    pool_pre_ping=True,
    future=True,
    connect_args=_connect_args,
)

if _is_sqlite:
    # WAL: reader 와 writer 가 공존(테스트의 eager worker 동시 쓰기 데드락 방지).
    # 운영(Postgres)에는 영향 없음.
    @event.listens_for(engine, "connect")
    def _sqlite_pragmas(dbapi_conn, _record):  # pragma: no cover
        cur = dbapi_conn.cursor()
        cur.execute("PRAGMA journal_mode=WAL")
        cur.execute("PRAGMA busy_timeout=30000")
        cur.close()

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


def get_db() -> Iterator[Session]:
    """FastAPI 의존성: 요청 단위 DB 세션."""
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()