"""Database engine, sessions, and FastAPI dependency."""

from collections.abc import Iterator

from sqlalchemy import Engine
from sqlmodel import Session, SQLModel, create_engine

from .settings import settings

_engine: Engine | None = None


def get_engine(url: str | None = None) -> Engine:
    """Process-wide engine singleton (override URL in tests via settings)."""
    global _engine
    if _engine is None:
        _engine = create_engine(url or settings.database_url)
    return _engine


def reset_engine() -> None:
    """Drop the cached engine (used by the test suite between DB targets)."""
    global _engine
    if _engine is not None:
        _engine.dispose()
        _engine = None


def get_session() -> Iterator[Session]:
    with Session(get_engine()) as session:
        yield session


def create_all(url: str | None = None) -> None:
    """Create tables directly (dev convenience; migrations own prod schema)."""
    SQLModel.metadata.create_all(get_engine(url))