from typing import Generator

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

from app.config import get_settings

engine = None
SessionLocal = sessionmaker(autocommit=False, autoflush=False)


class Base(DeclarativeBase):
    pass


def _build_engine(database_url: str):
    connect_args = {"check_same_thread": False} if database_url.startswith("sqlite") else {}
    return create_engine(database_url, connect_args=connect_args)


def configure_database(database_url: str | None = None) -> None:
    global engine

    settings = get_settings()
    resolved_database_url = database_url or settings.database_url
    engine = _build_engine(resolved_database_url)
    SessionLocal.configure(bind=engine)


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


def init_db(database_url: str | None = None) -> None:
    from app import models

    if engine is None or database_url is not None:
        configure_database(database_url)

    Base.metadata.create_all(bind=engine)