"""Database dependencies for FastAPI."""

from collections.abc import Generator
from pathlib import Path

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

from ont_platform.config import load_settings
from ont_platform.storage.models import Base

# Initialize database engine (lazy singleton)
_engine = None
_SessionLocal = None


def get_db_engine():
    """Get or create database engine."""
    global _engine
    if _engine is None:
        settings = load_settings()
        database_url = settings.database_url
        _ensure_sqlite_parent(database_url)
        _engine = create_engine(
            database_url,
            connect_args={"timeout": 30} if "sqlite" in database_url else {},
            pool_pre_ping=True,
            echo=False,
        )
        Base.metadata.create_all(bind=_engine)
    return _engine


def get_session_factory():
    """Get or create session factory."""
    global _SessionLocal
    if _SessionLocal is None:
        engine = get_db_engine()
        _SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
    return _SessionLocal


def get_db() -> Generator[Session, None, None]:
    """FastAPI dependency for database session."""
    SessionLocal = get_session_factory()
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()


def _ensure_sqlite_parent(database_url: str) -> None:
    if not database_url.startswith("sqlite:///"):
        return
    db_path = database_url.removeprefix("sqlite:///")
    if db_path in {":memory:", ""}:
        return
    Path(db_path).expanduser().parent.mkdir(parents=True, exist_ok=True)


__all__ = ["get_db", "get_db_engine", "get_session_factory"]