from collections.abc import Generator

from sqlalchemy import create_engine
from sqlalchemy.engine import Engine
from sqlalchemy.orm import DeclarativeBase, Session, sessionmaker
from sqlalchemy.pool import StaticPool

from fan_passport.config import get_settings


class Base(DeclarativeBase):
    """Shared declarative base for all ORM models."""


def _sqlite_connect_args(database_url: str) -> dict[str, bool]:
    if database_url.startswith("sqlite"):
        return {"check_same_thread": False}
    return {}


def _make_engine(database_url: str) -> Engine:
    kwargs: dict[str, object] = {
        "connect_args": _sqlite_connect_args(database_url),
        "future": True,
    }
    if database_url in {"sqlite://", "sqlite:///:memory:", "sqlite+pysqlite:///:memory:"}:
        kwargs["poolclass"] = StaticPool
    return create_engine(database_url, **kwargs)


_engine: Engine = _make_engine(get_settings().database_url)

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


def configure_database(database_url: str) -> Engine:
    """Rebind the global session factory.

    This is used by tests and by app factories that are passed explicit settings.
    """

    global _engine
    _engine = _make_engine(database_url)
    SessionLocal.configure(bind=_engine)
    return _engine


def get_engine() -> Engine:
    return _engine


def init_db() -> None:
    """Create all tables for MVP/local deployments.

    Production deployments should use a migration tool pointed at Base.metadata.
    """

    import fan_passport.models  # noqa: F401 - required so metadata knows all tables

    Base.metadata.create_all(bind=_engine)


def drop_db() -> None:
    import fan_passport.models  # noqa: F401 - required so metadata knows all tables

    Base.metadata.drop_all(bind=_engine)


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